< draft-ietf-tls-rfc4346-bis-06.txt   draft-ietf-tls-rfc4346-bis-07.txt >
INTERNET-DRAFT Tim Dierks INTERNET-DRAFT Tim Dierks
Obsoletes (if approved): RFC 3268, 4346, 4366 Independent Obsoletes (if approved): RFC 3268, 4346, 4366 Independent
Intended status: Proposed Standard Eric Rescorla Intended status: Proposed Standard Eric Rescorla
Network Resonance, Inc. Network Resonance, Inc.
<draft-ietf-tls-rfc4346-bis-06.txt> October 2007 (Expires April 2008) <draft-ietf-tls-rfc4346-bis-07.txt> November 2007 (Expires May 2008)
The Transport Layer Security (TLS) Protocol The Transport Layer Security (TLS) Protocol
Version 1.2 Version 1.2
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 99, line ? skipping to change at page 1, line 37
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document specifies Version 1.2 of the Transport Layer Security This document specifies Version 1.2 of the Transport Layer Security
(TLS) protocol. The TLS protocol provides communications security (TLS) protocol. The TLS protocol provides communications security
over the Internet. The protocol allows client/server applications to over the Internet. The protocol allows client/server applications to
communicate in a way that is designed to prevent eavesdropping, communicate in a way that is designed to prevent eavesdropping,
tampering, or message forgery. tampering, or message forgery.
Table of Contents Table of Contents
1. Introduction 3 1. Introduction 4
1.1 Requirements Terminology 5 1.1. Requirements Terminology 5
1.2 Major Differences from TLS 1.1 5 1.2. Major Differences from TLS 1.1 5
2. Goals 6 2. Goals 6
3. Goals of This Document 6 3. Goals of This Document 6
4. Presentation Language 7 4. Presentation Language 7
4.1. Basic Block Size 7 4.1. Basic Block Size 7
4.2. Miscellaneous 7 4.2. Miscellaneous 7
4.3. Vectors 7 4.3. Vectors 8
4.4. Numbers 8 4.4. Numbers 9
4.5. Enumerateds 9 4.5. Enumerateds 9
4.6. Constructed Types 10 4.6. Constructed Types 10
4.6.1. Variants 10 4.6.1. Variants 10
4.7. Cryptographic Attributes 11 4.7. Cryptographic Attributes 11
4.8. Constants 13 4.8. Constants 13
5. HMAC and the Pseudorandom Function 13 5. HMAC and the Pseudorandom Function 13
6. The TLS Record Protocol 14 6. The TLS Record Protocol 14
6.1. Connection States 15 6.1. Connection States 15
6.2. Record layer 17 6.2. Record layer 18
6.2.1. Fragmentation 17 6.2.1. Fragmentation 18
6.2.2. Record Compression and Decompression 19 6.2.2. Record Compression and Decompression 19
6.2.3. Record Payload Protection 19 6.2.3. Record Payload Protection 20
6.2.3.1. Null or Standard Stream Cipher 20 6.2.3.1. Null or Standard Stream Cipher 21
6.2.3.2. CBC Block Cipher 21 6.2.3.2. CBC Block Cipher 21
6.2.3.3. AEAD ciphers 23 6.2.3.3. AEAD ciphers 23
6.3. Key Calculation 24 6.3. Key Calculation 24
7. The TLS Handshaking Protocols 25 7. The TLS Handshaking Protocols 25
7.1. Change Cipher Spec Protocol 25 7.1. Change Cipher Spec Protocol 26
7.2. Alert Protocol 26 7.2. Alert Protocol 27
7.2.1. Closure Alerts 27 7.2.1. Closure Alerts 28
7.2.2. Error Alerts 28 7.2.2. Error Alerts 29
7.3. Handshake Protocol Overview 31 7.3. Handshake Protocol Overview 32
7.4. Handshake Protocol 34 7.4. Handshake Protocol 35
7.4.1. Hello Messages 35 7.4.1. Hello Messages 36
7.4.1.1. Hello Request 36 7.4.1.1. Hello Request 36
7.4.1.2. Client Hello 36 7.4.1.2. Client Hello 37
7.4.1.3. Server Hello 39 7.4.1.3. Server Hello 40
7.4.1.4 Hello Extensions 41 7.4.1.4 Hello Extensions 42
7.4.1.4.1 Signature Hash Algorithms 42 7.4.1.4.1 Signature Algorithms 43
7.4.2. Server Certificate 43 7.4.2. Server Certificate 44
7.4.3. Server Key Exchange Message 46 7.4.3. Server Key Exchange Message 47
7.4.4. Certificate Request 49 7.4.4. Certificate Request 49
7.4.5 Server hello done 50 7.4.5 Server hello done 51
7.4.6. Client Certificate 51 7.4.6. Client Certificate 52
7.4.7. Client Key Exchange Message 52 7.4.7. Client Key Exchange Message 53
7.4.7.1. RSA Encrypted Premaster Secret Message 53 7.4.7.1. RSA Encrypted Premaster Secret Message 54
7.4.7.2. Client Diffie-Hellman Public Value 55 7.4.7.2. Client Diffie-Hellman Public Value 56
7.4.8. Certificate verify 56 7.4.8. Certificate verify 57
7.4.9. Finished 57 7.4.9. Finished 58
8. Cryptographic Computations 58 8. Cryptographic Computations 59
8.1. Computing the Master Secret 58 8.1. Computing the Master Secret 60
8.1.1. RSA 59 8.1.1. RSA 60
8.1.2. Diffie-Hellman 59 8.1.2. Diffie-Hellman 60
9. Mandatory Cipher Suites 59 9. Mandatory Cipher Suites 60
10. Application Data Protocol 59 10. Application Data Protocol 60
11. Security Considerations 59 11. Security Considerations 60
12. IANA Considerations 59 12. IANA Considerations 61
A. Protocol Constant Values 62 A. Protocol Constant Values 63
A.1. Record Layer 62 A.1. Record Layer 63
A.2. Change Cipher Specs Message 63 A.2. Change Cipher Specs Message 64
A.3. Alert Messages 63 A.3. Alert Messages 64
A.4. Handshake Protocol 65 A.4. Handshake Protocol 65
A.4.1. Hello Messages 65 A.4.1. Hello Messages 65
A.4.2. Server Authentication and Key Exchange Messages 67 A.4.2. Server Authentication and Key Exchange Messages 67
A.4.3. Client Authentication and Key Exchange Messages 68 A.4.3. Client Authentication and Key Exchange Messages 68
A.4.4. Handshake Finalization Message 68 A.4.4. Handshake Finalization Message 69
A.5. The CipherSuite 69 A.5. The CipherSuite 69
A.6. The Security Parameters 71 A.6. The Security Parameters 72
B. Glossary 73 B. Glossary 73
C. CipherSuite Definitions 77 C. CipherSuite Definitions 77
D. Implementation Notes 79 D. Implementation Notes 79
D.1 Random Number Generation and Seeding 79 D.1 Random Number Generation and Seeding 79
D.2 Certificates and Authentication 79 D.2 Certificates and Authentication 79
D.3 CipherSuites 79 D.3 CipherSuites 79
D.4 Implementation Pitfalls 79 D.4 Implementation Pitfalls 79
E. Backward Compatibility 82 E. Backward Compatibility 82
E.1 Compatibility with TLS 1.0/1.1 and SSL 3.0 82 E.1 Compatibility with TLS 1.0/1.1 and SSL 3.0 82
E.2 Compatibility with SSL 2.0 83 E.2 Compatibility with SSL 2.0 83
skipping to change at page 99, line ? skipping to change at page 3, line 50
F.1.1.1. Anonymous Key Exchange 86 F.1.1.1. Anonymous Key Exchange 86
F.1.1.2. RSA Key Exchange and Authentication 87 F.1.1.2. RSA Key Exchange and Authentication 87
F.1.1.3. Diffie-Hellman Key Exchange with Authentication 87 F.1.1.3. Diffie-Hellman Key Exchange with Authentication 87
F.1.2. Version Rollback Attacks 88 F.1.2. Version Rollback Attacks 88
F.1.3. Detecting Attacks Against the Handshake Protocol 89 F.1.3. Detecting Attacks Against the Handshake Protocol 89
F.1.4. Resuming Sessions 89 F.1.4. Resuming Sessions 89
F.2. Protecting Application Data 89 F.2. Protecting Application Data 89
F.3. Explicit IVs 90 F.3. Explicit IVs 90
F.4. Security of Composite Cipher Modes 90 F.4. Security of Composite Cipher Modes 90
F.5 Denial of Service 91 F.5 Denial of Service 91
F.6 Final Notes 92 F.6 Final Notes 91
1. Introduction 1. Introduction
The primary goal of the TLS Protocol is to provide privacy and data The primary goal of the TLS Protocol is to provide privacy and data
integrity between two communicating applications. The protocol is integrity between two communicating applications. The protocol is
composed of two layers: the TLS Record Protocol and the TLS Handshake composed of two layers: the TLS Record Protocol and the TLS Handshake
Protocol. At the lowest level, layered on top of some reliable Protocol. At the lowest level, layered on top of some reliable
transport protocol (e.g., TCP[TCP]), is the TLS Record Protocol. The transport protocol (e.g., TCP[TCP]), is the TLS Record Protocol. The
TLS Record Protocol provides connection security that has two basic TLS Record Protocol provides connection security that has two basic
properties: properties:
- The connection is private. Symmetric cryptography is used for - The connection is private. Symmetric cryptography is used for
data encryption (e.g., DES [DES], RC4 [SCH] etc.). The keys for data encryption (e.g., DES [DES], RC4 [SCH] etc.). The keys for
this symmetric encryption are generated uniquely for each this symmetric encryption are generated uniquely for each
connection and are based on a secret negotiated by another connection and are based on a secret negotiated by another
protocol (such as the TLS Handshake Protocol). The Record protocol (such as the TLS Handshake Protocol). The Record Protocol
Protocol can also be used without encryption. can also be used without encryption.
- The connection is reliable. Message transport includes a message - The connection is reliable. Message transport includes a message
integrity check using a keyed MAC. Secure hash functions (e.g., integrity check using a keyed MAC. Secure hash functions (e.g.,
SHA, MD5, etc.) are used for MAC computations. The Record SHA, MD5, etc.) are used for MAC computations. The Record Protocol
Protocol can operate without a MAC, but is generally only used in can operate without a MAC, but is generally only used in this mode
this mode while another protocol is using the Record Protocol as while another protocol is using the Record Protocol as a transport
a transport for negotiating security parameters. for negotiating security parameters.
The TLS Record Protocol is used for encapsulation of various higher- The TLS Record Protocol is used for encapsulation of various higher-
level protocols. One such encapsulated protocol, the TLS Handshake level protocols. One such encapsulated protocol, the TLS Handshake
Protocol, allows the server and client to authenticate each other and Protocol, allows the server and client to authenticate each other and
to negotiate an encryption algorithm and cryptographic keys before to negotiate an encryption algorithm and cryptographic keys before
the application protocol transmits or receives its first byte of the application protocol transmits or receives its first byte of
data. The TLS Handshake Protocol provides connection security that data. The TLS Handshake Protocol provides connection security that
has three basic properties: has three basic properties:
- The peer's identity can be authenticated using asymmetric, or - The peer's identity can be authenticated using asymmetric, or
public key, cryptography (e.g., RSA [RSA], DSS [DSS], etc.). This public key, cryptography (e.g., RSA [RSA], DSS [DSS], etc.). This
authentication can be made optional, but is generally required authentication can be made optional, but is generally required for
for at least one of the peers. at least one of the peers.
- The negotiation of a shared secret is secure: the negotiated - The negotiation of a shared secret is secure: the negotiated
secret is unavailable to eavesdroppers, and for any authenticated secret is unavailable to eavesdroppers, and for any authenticated
connection the secret cannot be obtained, even by an attacker who connection the secret cannot be obtained, even by an attacker who
can place himself in the middle of the connection. can place himself in the middle of the connection.
- The negotiation is reliable: no attacker can modify the - The negotiation is reliable: no attacker can modify the
negotiation communication without being detected by the parties negotiation communication without being detected by the parties to
to the communication. the communication.
One advantage of TLS is that it is application protocol independent. One advantage of TLS is that it is application protocol independent.
Higher-level protocols can layer on top of the TLS Protocol Higher-level protocols can layer on top of the TLS Protocol
transparently. The TLS standard, however, does not specify how transparently. The TLS standard, however, does not specify how
protocols add security with TLS; the decisions on how to initiate TLS protocols add security with TLS; the decisions on how to initiate TLS
handshaking and how to interpret the authentication certificates handshaking and how to interpret the authentication certificates
exchanged are left to the judgment of the designers and implementors exchanged are left to the judgment of the designers and implementors
of protocols that run on top of TLS. of protocols that run on top of TLS.
1.1 Requirements Terminology 1.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [REQ]. document are to be interpreted as described in RFC 2119 [REQ].
1.2 Major Differences from TLS 1.1 1.2. Major Differences from TLS 1.1
This document is a revision of the TLS 1.1 [TLS1.1] protocol which This document is a revision of the TLS 1.1 [TLS1.1] protocol which
contains improved flexibility, particularly for negotiation of contains improved flexibility, particularly for negotiation of
cryptographic algorithms. The major changes are: cryptographic algorithms. The major changes are:
- Merged in TLS Extensions definition and AES Cipher Suites from - The MD5/SHA-1 combination in the PRF has been replaced with cipher
external documents [TLSEXT] and [TLSAES]. suite specified PRFs. All cipher suites in this document use
P_SHA256.
- Replacement of MD5/SHA-1 combination in the PRF. Addition
of cipher-suite specified PRFs.
- Replacement of MD5/SHA-1 combination in the digitally-signed - The MD5/SHA-1 combination in the digitally-signed element has been
element. replaced with a single hash.
- Substantial cleanup to the clients and servers ability to - Substantial cleanup to the clients and servers ability to specify
specify which digest and signature algorithms they will which hash and signature algorithms they will accept. Note that
accept. Note that this also relaxes some of the constraints this also relaxes some of the constraints on signature and hash
on signature and digest algorithms from previous versions of algorithms from previous versions of TLS.
TLS.
- Addition of support for authenticated encryption with additional - Addition of support for authenticated encryption with additional
data modes. data modes.
- Tightened up a number of requirements. - TLS Extensions definition and AES Cipher Suites were merged in
from external [TLSEXT] and [TLSAES].
- Added some guidance that DH groups should be checked for size. - Tighter checking of EncryptedPreMasterSecret version numbers.
- Cleaned up description of Bleichenbacher/Klima attack defenses. - Tightened up a number of requirements.
- Tighter checking of EncryptedPreMasterSecret version numbers. - Verify_data length now depends on the cipher suite (default is
still 12).
- Stronger language about when alerts MUST be sent. - Cleaned up description of Bleichenbacher/Klima attack defenses.
- Added an Implementation Pitfalls sections - Alerts MUST now be sent in many cases.
- After a certificate_request, if no certificates are available,
clients now MUST send an empty certificate list.
- Harmonized the requirement to send an empty certificate list - TLS_RSA_WITH_AES_128_CBC_SHA is now the mandatory to implement
after certificate_request even when no certs are available. cipher suite.
- Made the verify_data length depend on the cipher suite. - IDEE and DES are now deprecated.
- TLS_RSA_WITH_AES_128_CBC_SHA is now the mandatory to implement - Support for the SSLv2 backward-compatible hello is now a MAY, not
cipher suite. a SHOULD. This will probably become a SHOULD NOT in the future.
- The usual clarifications and editorial work. - Added an Implementation Pitfalls sections
- The usual clarifications and editorial work.
2. Goals 2. Goals
The goals of TLS Protocol, in order of their priority, are as The goals of TLS Protocol, in order of their priority, are as
follows: follows:
1. Cryptographic security: TLS should be used to establish a secure 1. Cryptographic security: TLS should be used to establish a secure
connection between two parties. connection between two parties.
2. Interoperability: Independent programmers should be able to 2. Interoperability: Independent programmers should be able to
develop applications utilizing TLS that can successfully exchange develop applications utilizing TLS that can successfully exchange
cryptographic parameters without knowledge of one another's code. cryptographic parameters without knowledge of one another's code.
3. Extensibility: TLS seeks to provide a framework into which new 3. Extensibility: TLS seeks to provide a framework into which new
public key and bulk encryption methods can be incorporated as public key and bulk encryption methods can be incorporated as
necessary. This will also accomplish two sub-goals: preventing necessary. This will also accomplish two sub-goals: preventing the
the need to create a new protocol (and risking the introduction need to create a new protocol (and risking the introduction of
of possible new weaknesses) and avoiding the need to implement an possible new weaknesses) and avoiding the need to implement an
entire new security library. entire new security library.
4. Relative efficiency: Cryptographic operations tend to be highly 4. Relative efficiency: Cryptographic operations tend to be highly
CPU intensive, particularly public key operations. For this CPU intensive, particularly public key operations. For this
reason, the TLS protocol has incorporated an optional session reason, the TLS protocol has incorporated an optional session
caching scheme to reduce the number of connections that need to caching scheme to reduce the number of connections that need to be
be established from scratch. Additionally, care has been taken to established from scratch. Additionally, care has been taken to
reduce network activity. reduce network activity.
3. Goals of This Document 3. Goals of This Document
This document and the TLS protocol itself are based on the SSL 3.0 This document and the TLS protocol itself are based on the SSL 3.0
Protocol Specification as published by Netscape. The differences Protocol Specification as published by Netscape. The differences
between this protocol and SSL 3.0 are not dramatic, but they are between this protocol and SSL 3.0 are not dramatic, but they are
significant enough that the various versions of TLS and SSL 3.0 do significant enough that the various versions of TLS and SSL 3.0 do
not interoperate (although each protocol incorporates a mechanism by not interoperate (although each protocol incorporates a mechanism by
which an implementation can back down to prior versions). This which an implementation can back down to prior versions). This
document is intended primarily for readers who will be implementing document is intended primarily for readers who will be implementing
skipping to change at page 99, line ? skipping to change at page 7, line 34
no general application beyond that particular goal. no general application beyond that particular goal.
4.1. Basic Block Size 4.1. Basic Block Size
The representation of all data items is explicitly specified. The The representation of all data items is explicitly specified. The
basic data block size is one byte (i.e., 8 bits). Multiple byte data basic data block size is one byte (i.e., 8 bits). Multiple byte data
items are concatenations of bytes, from left to right, from top to items are concatenations of bytes, from left to right, from top to
bottom. From the bytestream, a multi-byte item (a numeric in the bottom. From the bytestream, a multi-byte item (a numeric in the
example) is formed (using C notation) by: example) is formed (using C notation) by:
value = (byte[0] << 8*(n-1)) | (byte[1] << 8*(n-2)) | value = (byte[0] << 8*(n-1)) | (byte[1] << 8*(n-2)) |
... | byte[n-1]; ... | byte[n-1];
This byte ordering for multi-byte values is the commonplace network This byte ordering for multi-byte values is the commonplace network
byte order or big endian format. byte order or big endian format.
4.2. Miscellaneous 4.2. Miscellaneous
Comments begin with "/*" and end with "*/". Comments begin with "/*" and end with "*/".
Optional components are denoted by enclosing them in "[[ ]]" double Optional components are denoted by enclosing them in "[[ ]]" double
brackets. brackets.
skipping to change at page 99, line ? skipping to change at page 8, line 13
opaque. opaque.
4.3. Vectors 4.3. Vectors
A vector (single dimensioned array) is a stream of homogeneous data A vector (single dimensioned array) is a stream of homogeneous data
elements. The size of the vector may be specified at documentation elements. The size of the vector may be specified at documentation
time or left unspecified until runtime. In either case, the length time or left unspecified until runtime. In either case, the length
declares the number of bytes, not the number of elements, in the declares the number of bytes, not the number of elements, in the
vector. The syntax for specifying a new type, T', that is a fixed- vector. The syntax for specifying a new type, T', that is a fixed-
length vector of type T is length vector of type T is
T T'[n];
T T'[n];
Here, T' occupies n bytes in the data stream, where n is a multiple Here, T' occupies n bytes in the data stream, where n is a multiple
of the size of T. The length of the vector is not included in the of the size of T. The length of the vector is not included in the
encoded stream. encoded stream.
In the following example, Datum is defined to be three consecutive In the following example, Datum is defined to be three consecutive
bytes that the protocol does not interpret, while Data is three bytes that the protocol does not interpret, while Data is three
consecutive Datum, consuming a total of nine bytes. consecutive Datum, consuming a total of nine bytes.
opaque Datum[3]; /* three uninterpreted bytes */ opaque Datum[3]; /* three uninterpreted bytes */
Datum Data[9]; /* 3 consecutive 3 byte vectors */ Datum Data[9]; /* 3 consecutive 3 byte vectors */
Variable-length vectors are defined by specifying a subrange of legal Variable-length vectors are defined by specifying a subrange of legal
lengths, inclusively, using the notation <floor..ceiling>. When lengths, inclusively, using the notation <floor..ceiling>. When
these are encoded, the actual length precedes the vector's contents these are encoded, the actual length precedes the vector's contents
in the byte stream. The length will be in the form of a number in the byte stream. The length will be in the form of a number
consuming as many bytes as required to hold the vector's specified consuming as many bytes as required to hold the vector's specified
maximum (ceiling) length. A variable-length vector with an actual maximum (ceiling) length. A variable-length vector with an actual
length field of zero is referred to as an empty vector. length field of zero is referred to as an empty vector.
T T'<floor..ceiling>; T T'<floor..ceiling>;
In the following example, mandatory is a vector that must contain In the following example, mandatory is a vector that must contain
between 300 and 400 bytes of type opaque. It can never be empty. The between 300 and 400 bytes of type opaque. It can never be empty. The
actual length field consumes two bytes, a uint16, sufficient to actual length field consumes two bytes, a uint16, sufficient to
represent the value 400 (see Section 4.4). On the other hand, longer represent the value 400 (see Section 4.4). On the other hand, longer
can represent up to 800 bytes of data, or 400 uint16 elements, and it can represent up to 800 bytes of data, or 400 uint16 elements, and it
may be empty. Its encoding will include a two-byte actual length may be empty. Its encoding will include a two-byte actual length
field prepended to the vector. The length of an encoded vector must field prepended to the vector. The length of an encoded vector must
be an even multiple of the length of a single element (for example, a be an even multiple of the length of a single element (for example, a
17-byte vector of uint16 would be illegal). 17-byte vector of uint16 would be illegal).
opaque mandatory<300..400>; opaque mandatory<300..400>;
/* length field is 2 bytes, cannot be empty */ /* length field is 2 bytes, cannot be empty */
uint16 longer<0..800>; uint16 longer<0..800>;
/* zero to 400 16-bit unsigned integers */ /* zero to 400 16-bit unsigned integers */
4.4. Numbers 4.4. Numbers
The basic numeric data type is an unsigned byte (uint8). All larger The basic numeric data type is an unsigned byte (uint8). All larger
numeric data types are formed from fixed-length series of bytes numeric data types are formed from fixed-length series of bytes
concatenated as described in Section 4.1 and are also unsigned. The concatenated as described in Section 4.1 and are also unsigned. The
following numeric types are predefined. following numeric types are predefined.
uint8 uint16[2]; uint8 uint16[2];
uint8 uint24[3]; uint8 uint24[3];
uint8 uint32[4]; uint8 uint32[4];
uint8 uint64[8]; uint8 uint64[8];
All values, here and elsewhere in the specification, are stored in All values, here and elsewhere in the specification, are stored in
"network" or "big-endian" order; the uint32 represented by the hex "network" or "big-endian" order; the uint32 represented by the hex
bytes 01 02 03 04 is equivalent to the decimal value 16909060. bytes 01 02 03 04 is equivalent to the decimal value 16909060.
Note that in some cases (e.g., DH parameters) it is necessary to Note that in some cases (e.g., DH parameters) it is necessary to
represent integers as opaque vectors. In such cases, they are represent integers as opaque vectors. In such cases, they are
represented as unsigned integers (i.e., leading zero octets are not represented as unsigned integers (i.e., leading zero octets are not
required even if the most significant bit is set). required even if the most significant bit is set).
4.5. Enumerateds 4.5. Enumerateds
An additional sparse data type is available called enum. A field of An additional sparse data type is available called enum. A field of
type enum can only assume the values declared in the definition. type enum can only assume the values declared in the definition.
Each definition is a different type. Only enumerateds of the same Each definition is a different type. Only enumerateds of the same
type may be assigned or compared. Every element of an enumerated must type may be assigned or compared. Every element of an enumerated must
be assigned a value, as demonstrated in the following example. Since be assigned a value, as demonstrated in the following example. Since
the elements of the enumerated are not ordered, they can be assigned the elements of the enumerated are not ordered, they can be assigned
any unique value, in any order. any unique value, in any order.
enum { e1(v1), e2(v2), ... , en(vn) [[, (n)]] } Te; enum { e1(v1), e2(v2), ... , en(vn) [[, (n)]] } Te;
Enumerateds occupy as much space in the byte stream as would its Enumerateds occupy as much space in the byte stream as would its
maximal defined ordinal value. The following definition would cause maximal defined ordinal value. The following definition would cause
one byte to be used to carry fields of type Color. one byte to be used to carry fields of type Color.
enum { red(3), blue(5), white(7) } Color; enum { red(3), blue(5), white(7) } Color;
One may optionally specify a value without its associated tag to One may optionally specify a value without its associated tag to
force the width definition without defining a superfluous element. force the width definition without defining a superfluous element.
In the following example, Taste will consume two bytes in the data In the following example, Taste will consume two bytes in the data
stream but can only assume the values 1, 2, or 4. stream but can only assume the values 1, 2, or 4.
enum { sweet(1), sour(2), bitter(4), (32000) } Taste; enum { sweet(1), sour(2), bitter(4), (32000) } Taste;
The names of the elements of an enumeration are scoped within the The names of the elements of an enumeration are scoped within the
defined type. In the first example, a fully qualified reference to defined type. In the first example, a fully qualified reference to
the second element of the enumeration would be Color.blue. Such the second element of the enumeration would be Color.blue. Such
qualification is not required if the target of the assignment is well qualification is not required if the target of the assignment is well
specified. specified.
Color color = Color.blue; /* overspecified, legal */ Color color = Color.blue; /* overspecified, legal */
Color color = blue; /* correct, type implicit */ Color color = blue; /* correct, type implicit */
For enumerateds that are never converted to external representation, For enumerateds that are never converted to external representation,
the numerical information may be omitted. the numerical information may be omitted.
enum { low, medium, high } Amount; enum { low, medium, high } Amount;
4.6. Constructed Types 4.6. Constructed Types
Structure types may be constructed from primitive types for Structure types may be constructed from primitive types for
convenience. Each specification declares a new, unique type. The convenience. Each specification declares a new, unique type. The
syntax for definition is much like that of C. syntax for definition is much like that of C.
struct { struct {
T1 f1; T1 f1;
T2 f2; T2 f2;
... ...
Tn fn; Tn fn;
} [[T]]; } [[T]];
The fields within a structure may be qualified using the type's name, The fields within a structure may be qualified using the type's name,
with a syntax much like that available for enumerateds. For example, with a syntax much like that available for enumerateds. For example,
T.f2 refers to the second field of the previous declaration. T.f2 refers to the second field of the previous declaration.
Structure definitions may be embedded. Structure definitions may be embedded.
4.6.1. Variants 4.6.1. Variants
Defined structures may have variants based on some knowledge that is Defined structures may have variants based on some knowledge that is
available within the environment. The selector must be an enumerated available within the environment. The selector must be an enumerated
type that defines the possible variants the structure defines. There type that defines the possible variants the structure defines. There
must be a case arm for every element of the enumeration declared in must be a case arm for every element of the enumeration declared in
the select. The body of the variant structure may be given a label the select. The body of the variant structure may be given a label
for reference. The mechanism by which the variant is selected at for reference. The mechanism by which the variant is selected at
runtime is not prescribed by the presentation language. runtime is not prescribed by the presentation language.
struct { struct {
T1 f1; T1 f1;
T2 f2; T2 f2;
.... ....
Tn fn; Tn fn;
select (E) { select (E) {
case e1: Te1; case e1: Te1;
case e2: Te2; case e2: Te2;
.... ....
case en: Ten; case en: Ten;
} [[fv]]; } [[fv]];
} [[Tv]]; } [[Tv]];
For example: For example:
enum { apple, orange } VariantTag; enum { apple, orange } VariantTag;
struct { struct {
uint16 number; uint16 number;
opaque string<0..10>; /* variable length */ opaque string<0..10>; /* variable length */
} V1; } V1;
struct { struct {
uint32 number; uint32 number;
opaque string[10]; /* fixed length */ opaque string[10]; /* fixed length */
} V2; } V2;
struct { struct {
select (VariantTag) { /* value of selector is implicit */ select (VariantTag) { /* value of selector is implicit */
case apple: V1; /* VariantBody, tag = apple */ case apple: V1; /* VariantBody, tag = apple */
case orange: V2; /* VariantBody, tag = orange */ case orange: V2; /* VariantBody, tag = orange */
} variant_body; /* optional label on variant */ } variant_body; /* optional label on variant */
} VariantRecord; } VariantRecord;
Variant structures may be qualified (narrowed) by specifying a value Variant structures may be qualified (narrowed) by specifying a value
for the selector prior to the type. For example, an for the selector prior to the type. For example, an
orange VariantRecord orange VariantRecord
is a narrowed type of a VariantRecord containing a variant_body of is a narrowed type of a VariantRecord containing a variant_body of
type V2. type V2.
4.7. Cryptographic Attributes 4.7. Cryptographic Attributes
The five cryptographic operations digital signing, stream cipher The five cryptographic operations digital signing, stream cipher
encryption, block cipher encryption, authenticated encryption with encryption, block cipher encryption, authenticated encryption with
additional data (AEAD) encryption and public key encryption are additional data (AEAD) encryption and public key encryption are
designated digitally-signed, stream-ciphered, block-ciphered, aead- designated digitally-signed, stream-ciphered, block-ciphered, aead-
skipping to change at page 99, line ? skipping to change at page 12, line 7
Cryptographic keys are implied by the current session state (see Cryptographic keys are implied by the current session state (see
Section 6.1). Section 6.1).
In digital signing, one-way hash functions are used as input for a In digital signing, one-way hash functions are used as input for a
signing algorithm. A digitally-signed element is encoded as an opaque signing algorithm. A digitally-signed element is encoded as an opaque
vector <0..2^16-1>, where the length is specified by the signing vector <0..2^16-1>, where the length is specified by the signing
algorithm and key. algorithm and key.
In RSA signing, the opaque vector contains the signature generated In RSA signing, the opaque vector contains the signature generated
using the RSASSA-PKCS1-v1_5 signature scheme defined in [PKCS1]. As using the RSASSA-PKCS1-v1_5 signature scheme defined in [PKCS1]. As
discussed in [PKCS1], the DigestInfo MUST be DER encoded and for discussed in [PKCS1], the DigestInfo MUST be DER encoded and for hash
digest algorithms without parameters (which include SHA-1) the algorithms without parameters (which include SHA-1) the
DigestInfo.AlgorithmIdentifier.parameters field MUST be NULL but DigestInfo.AlgorithmIdentifier.parameters field MUST be NULL but
implementations MUST accept both without parameters and with NULL implementations MUST accept both without parameters and with NULL
parameters. Note that earlier versions of TLS used a different RSA parameters. Note that earlier versions of TLS used a different RSA
signature scheme which did not include a DigestInfo encoding. signature scheme which did not include a DigestInfo encoding.
In DSS, the 20 bytes of the SHA-1 hash are run directly through the In DSS, the 20 bytes of the SHA-1 hash are run directly through the
Digital Signing Algorithm with no additional hashing. This produces Digital Signing Algorithm with no additional hashing. This produces
two values, r and s. The DSS signature is an opaque vector, as above, two values, r and s. The DSS signature is an opaque vector, as above,
the contents of which are the DER encoding of: the contents of which are the DER encoding of:
Dss-Sig-Value ::= SEQUENCE { Dss-Sig-Value ::= SEQUENCE {
r INTEGER, r INTEGER,
s INTEGER s INTEGER
} }
Note: In current terminology, DSA refers to the Digital Signature Note: In current terminology, DSA refers to the Digital Signature
Algorithm and DSS refers to the NIST standard. For historical Algorithm and DSS refers to the NIST standard. For historical
reasons, this document uses DSS and DSA interchangeably reasons, this document uses DSS and DSA interchangeably
to refer to the DSA algorithm, as was done in SSLv3. to refer to the DSA algorithm, as was done in SSLv3.
In stream cipher encryption, the plaintext is exclusive-ORed with an In stream cipher encryption, the plaintext is exclusive-ORed with an
identical amount of output generated from a cryptographically secure identical amount of output generated from a cryptographically secure
keyed pseudorandom number generator. keyed pseudorandom number generator.
In block cipher encryption, every block of plaintext encrypts to a In block cipher encryption, every block of plaintext encrypts to a
block of ciphertext. All block cipher encryption is done in CBC block of ciphertext. All block cipher encryption is done in CBC
(Cipher Block Chaining) mode, and all items that are block-ciphered (Cipher Block Chaining) mode, and all items that are block-ciphered
will be an exact multiple of the cipher block length. will be an exact multiple of the cipher block length.
In AEAD encryption, the plaintext is simultaneously encrypted and In AEAD encryption, the plaintext is simultaneously encrypted and
integrity protected. The input may be of any length and the output is integrity protected. The input may be of any length and aead-ciphered
generally larger than the input in order to accomodate the integrity output is generally larger than the input in order to accomodate the
check value. integrity check value.
In public key encryption, a public key algorithm is used to encrypt In public key encryption, a public key algorithm is used to encrypt
data in such a way that it can be decrypted only with the matching data in such a way that it can be decrypted only with the matching
private key. A public-key-encrypted element is encoded as an opaque private key. A public-key-encrypted element is encoded as an opaque
vector <0..2^16-1>, where the length is specified by the encryption vector <0..2^16-1>, where the length is specified by the encryption
algorithm and key. algorithm and key.
RSA encryption is done using the RSAES-PKCS1-v1_5 encryption scheme RSA encryption is done using the RSAES-PKCS1-v1_5 encryption scheme
defined in [PKCS1]. defined in [PKCS1].
In the following example In the following example
stream-ciphered struct { stream-ciphered struct {
uint8 field1; uint8 field1;
uint8 field2; uint8 field2;
digitally-signed opaque hash[20]; digitally-signed opaque hash[20];
} UserType; } UserType;
the contents of hash are used as input for the signing algorithm, and the contents of hash are used as input for the signing algorithm, and
then the entire structure is encrypted with a stream cipher. The then the entire structure is encrypted with a stream cipher. The
length of this structure, in bytes, would be equal to two bytes for length of this structure, in bytes, would be equal to two bytes for
field1 and field2, plus two bytes for the length of the signature, field1 and field2, plus two bytes for the length of the signature,
plus the length of the output of the signing algorithm. This is known plus the length of the output of the signing algorithm. This is known
because the algorithm and key used for the signing are known prior to because the algorithm and key used for the signing are known prior to
encoding or decoding this structure. encoding or decoding this structure.
4.8. Constants 4.8. Constants
Typed constants can be defined for purposes of specification by Typed constants can be defined for purposes of specification by
declaring a symbol of the desired type and assigning values to it. declaring a symbol of the desired type and assigning values to it.
Under-specified types (opaque, variable length vectors, and Under-specified types (opaque, variable length vectors, and
structures that contain opaque) cannot be assigned values. No fields structures that contain opaque) cannot be assigned values. No fields
of a multi-element structure or vector may be elided. of a multi-element structure or vector may be elided.
For example: For example:
struct { struct {
uint8 f1; uint8 f1;
uint8 f2; uint8 f2;
} Example1; } Example1;
Example1 ex1 = {1, 4}; /* assigns f1 = 1, f2 = 4 */ Example1 ex1 = {1, 4}; /* assigns f1 = 1, f2 = 4 */
5. HMAC and the Pseudorandom Function 5. HMAC and the Pseudorandom Function
The TLS record layer uses a keyed Message Authentication Code (MAC) The TLS record layer uses a keyed Message Authentication Code (MAC)
to protect message integrity. The cipher suites defined in this to protect message integrity. The cipher suites defined in this
document use a construction known as HMAC, described in [HMAC], which document use a construction known as HMAC, described in [HMAC], which
is based on a hash function. Other cipher suites MAY define their own is based on a hash function. Other cipher suites MAY define their own
MAC constructions, if needed. MAC constructions, if needed.
In addition, a construction is required to do expansion of secrets In addition, a construction is required to do expansion of secrets
skipping to change at page 99, line ? skipping to change at page 14, line 14
SHA-256 hash function is used for all cipher suites defined in this SHA-256 hash function is used for all cipher suites defined in this
document and in TLS documents published prior to this document when document and in TLS documents published prior to this document when
TLS 1.2 is negotiated. New cipher suites MUST explicitly specify a TLS 1.2 is negotiated. New cipher suites MUST explicitly specify a
PRF and in general SHOULD use the TLS PRF with SHA-256 or a stronger PRF and in general SHOULD use the TLS PRF with SHA-256 or a stronger
standard hash function. standard hash function.
First, we define a data expansion function, P_hash(secret, data) that First, we define a data expansion function, P_hash(secret, data) that
uses a single hash function to expand a secret and seed into an uses a single hash function to expand a secret and seed into an
arbitrary quantity of output: arbitrary quantity of output:
P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) + P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) +
HMAC_hash(secret, A(2) + seed) + HMAC_hash(secret, A(2) + seed) +
HMAC_hash(secret, A(3) + seed) + ... HMAC_hash(secret, A(3) + seed) + ...
Where + indicates concatenation. Where + indicates concatenation.
A() is defined as: A() is defined as:
A(0) = seed
A(i) = HMAC_hash(secret, A(i-1)) A(0) = seed
A(i) = HMAC_hash(secret, A(i-1))
P_hash can be iterated as many times as is necessary to produce the P_hash can be iterated as many times as is necessary to produce the
required quantity of data. For example, if P_SHA-1 is being used to required quantity of data. For example, if P_SHA-1 is being used to
create 64 bytes of data, it will have to be iterated 4 times (through create 64 bytes of data, it will have to be iterated 4 times (through
A(4)), creating 80 bytes of output data; the last 16 bytes of the A(4)), creating 80 bytes of output data; the last 16 bytes of the
final iteration will then be discarded, leaving 64 bytes of output final iteration will then be discarded, leaving 64 bytes of output
data. data.
TLS's PRF is created by applying P_hash to the secret as: TLS's PRF is created by applying P_hash to the secret as:
PRF(secret, label, seed) = P_<hash>(secret, label + seed) PRF(secret, label, seed) = P_<hash>(secret, label + seed)
The label is an ASCII string. It should be included in the exact form The label is an ASCII string. It should be included in the exact form
it is given without a length byte or trailing null character. For it is given without a length byte or trailing null character. For
example, the label "slithy toves" would be processed by hashing the example, the label "slithy toves" would be processed by hashing the
following bytes: following bytes:
73 6C 69 74 68 79 20 74 6F 76 65 73 73 6C 69 74 68 79 20 74 6F 76 65 73
6. The TLS Record Protocol 6. The TLS Record Protocol
The TLS Record Protocol is a layered protocol. At each layer, The TLS Record Protocol is a layered protocol. At each layer,
messages may include fields for length, description, and content. messages may include fields for length, description, and content.
The Record Protocol takes messages to be transmitted, fragments the The Record Protocol takes messages to be transmitted, fragments the
data into manageable blocks, optionally compresses the data, applies data into manageable blocks, optionally compresses the data, applies
a MAC, encrypts, and transmits the result. Received data is a MAC, encrypts, and transmits the result. Received data is
decrypted, verified, decompressed, reassembled, and then delivered to decrypted, verified, decompressed, reassembled, and then delivered to
higher-level clients. higher-level clients.
skipping to change at page 99, line ? skipping to change at page 15, line 29
deal with all possible attacks against it. Note that because the deal with all possible attacks against it. Note that because the
type and length of a record are not protected by encryption, care type and length of a record are not protected by encryption, care
SHOULD be taken to minimize the value of traffic analysis of these SHOULD be taken to minimize the value of traffic analysis of these
values. values.
6.1. Connection States 6.1. Connection States
A TLS connection state is the operating environment of the TLS Record A TLS connection state is the operating environment of the TLS Record
Protocol. It specifies a compression algorithm, an encryption Protocol. It specifies a compression algorithm, an encryption
algorithm, and a MAC algorithm. In addition, the parameters for these algorithm, and a MAC algorithm. In addition, the parameters for these
algorithms are known: the MAC secret and the bulk encryption keys for algorithms are known: the MAC key and the bulk encryption keys for
the connection in both the read and the write directions. Logically, the connection in both the read and the write directions. Logically,
there are always four connection states outstanding: the current read there are always four connection states outstanding: the current read
and write states, and the pending read and write states. All records and write states, and the pending read and write states. All records
are processed under the current read and write states. The security are processed under the current read and write states. The security
parameters for the pending states can be set by the TLS Handshake parameters for the pending states can be set by the TLS Handshake
Protocol, and the Change Cipher Spec can selectively make either of Protocol, and the Change Cipher Spec can selectively make either of
the pending states current, in which case the appropriate current the pending states current, in which case the appropriate current
state is disposed of and replaced with the pending state; the pending state is disposed of and replaced with the pending state; the pending
state is then reinitialized to an empty state. It is illegal to make state is then reinitialized to an empty state. It is illegal to make
a state that has not been initialized with security parameters a a state that has not been initialized with security parameters a
current state. The initial current state always specifies that no current state. The initial current state always specifies that no
encryption, compression, or MAC will be used. encryption, compression, or MAC will be used.
The security parameters for a TLS Connection read and write state are The security parameters for a TLS Connection read and write state are
set by providing the following values: set by providing the following values:
connection end connection end
Whether this entity is considered the "client" or the "server" in Whether this entity is considered the "client" or the "server" in
this connection. this connection.
PRF algorithm
An algorithm used to generate keys from the master secret (see
Sections 5 and 6.3).
bulk encryption algorithm bulk encryption algorithm
An algorithm to be used for bulk encryption. This specification An algorithm to be used for bulk encryption. This specification
includes the key size of this algorithm, how much of that key is includes the key size of this algorithm, whether it is a block,
secret, whether it is a block, stream, or AEAD cipher, and the stream, or AEAD cipher, the block size of the cipher (if
block size and fixed initialization vector size of the cipher (if appropriate), and the lengths of explicit and implicit
appropriate). initialization vectors (or nonces).
MAC algorithm MAC algorithm
An algorithm to be used for message authentication. This An algorithm to be used for message authentication. This
specification includes the size of the value returned by the MAC specification includes the size of the value returned by the MAC
algorithm. algorithm.
compression algorithm compression algorithm
An algorithm to be used for data compression. This specification An algorithm to be used for data compression. This specification
must include all information the algorithm requires to do must include all information the algorithm requires to do
compression. compression.
master secret master secret
A 48-byte secret shared between the two peers in the connection. A 48-byte secret shared between the two peers in the connection.
client random client random
A 32-byte value provided by the client. A 32-byte value provided by the client.
server random server random
A 32-byte value provided by the server. A 32-byte value provided by the server.
These parameters are defined in the presentation language as: These parameters are defined in the presentation language as:
enum { server, client } ConnectionEnd; enum { server, client } ConnectionEnd;
enum { null, rc4, rc2, des, 3des, idea, aes } enum { tls_prf_sha256 } PRFAlgorithm;
BulkCipherAlgorithm;
enum { stream, block, aead } CipherType; enum { null, rc4, 3des, aes }
BulkCipherAlgorithm;
enum { null, hmac_md5, hmac_sha, hmac_sha256, hmac_sha384, enum { stream, block, aead } CipherType;
hmac_sha512} MACAlgorithm;
/* The use of "sha" above is historical and denotes SHA-1 */ enum { null, hmac_md5, hmac_sha, hmac_sha256, hmac_sha384,
hmac_sha512} MACAlgorithm;
enum { null(0), (255) } CompressionMethod; /* The use of "sha" above is historical and denotes SHA-1 */
/* The algorithms specified in CompressionMethod, enum { null(0), (255) } CompressionMethod;
BulkCipherAlgorithm, and MACAlgorithm may be added to. */ /* The algorithms specified in CompressionMethod,
BulkCipherAlgorithm, and MACAlgorithm may be added to. */
struct { struct {
ConnectionEnd entity; ConnectionEnd entity;
BulkCipherAlgorithm bulk_cipher_algorithm; PRFAlgorithm prf_algorithm;
CipherType cipher_type; BulkCipherAlgorithm bulk_cipher_algorithm;
uint8 enc_key_length; CipherType cipher_type;
uint8 block_length; uint8 enc_key_length;
uint8 fixed_iv_length; uint8 block_length;
uint8 record_iv_length; uint8 fixed_iv_length;
MACAlgorithm mac_algorithm; uint8 record_iv_length;
uint8 mac_length; MACAlgorithm mac_algorithm;
uint8 mac_key_length; uint8 mac_length;
uint8 verify_data_length; uint8 mac_key_length;
CompressionMethod compression_algorithm; CompressionMethod compression_algorithm;
opaque master_secret[48]; opaque master_secret[48];
opaque client_random[32]; opaque client_random[32];
opaque server_random[32]; opaque server_random[32];
} SecurityParameters; } SecurityParameters;
The record layer will use the security parameters to generate the The record layer will use the security parameters to generate the
following six items: following six items (some of which are not required by all ciphers,
and are thus empty):
client write MAC secret client write MAC key
server write MAC secret server write MAC key
client write key client write encryption key
server write key server write encryption key
client write IV client write IV
server write IV server write IV
The client write parameters are used by the server when receiving and The client write parameters are used by the server when receiving and
processing records and vice-versa. The algorithm used for generating processing records and vice-versa. The algorithm used for generating
these items from the security parameters is described in Section 6.3. these items from the security parameters is described in Section 6.3.
Once the security parameters have been set and the keys have been Once the security parameters have been set and the keys have been
generated, the connection states can be instantiated by making them generated, the connection states can be instantiated by making them
the current states. These current states MUST be updated for each the current states. These current states MUST be updated for each
record processed. Each connection state includes the following record processed. Each connection state includes the following
elements: elements:
compression state compression state
The current state of the compression algorithm. The current state of the compression algorithm.
cipher state cipher state
The current state of the encryption algorithm. This will consist The current state of the encryption algorithm. This will consist
of the scheduled key for that connection. For stream ciphers, of the scheduled key for that connection. For stream ciphers, this
this will also contain whatever state information is necessary to will also contain whatever state information is necessary to allow
allow the stream to continue to encrypt or decrypt data. the stream to continue to encrypt or decrypt data.
MAC secret MAC key
The MAC secret for this connection, as generated above. The MAC key for this connection, as generated above.
sequence number sequence number
Each connection state contains a sequence number, which is Each connection state contains a sequence number, which is
maintained separately for read and write states. The sequence maintained separately for read and write states. The sequence
number MUST be set to zero whenever a connection state is made number MUST be set to zero whenever a connection state is made the
the active state. Sequence numbers are of type uint64 and may not active state. Sequence numbers are of type uint64 and may not
exceed 2^64-1. Sequence numbers do not wrap. If a TLS exceed 2^64-1. Sequence numbers do not wrap. If a TLS
implementation would need to wrap a sequence number, it must implementation would need to wrap a sequence number, it must
renegotiate instead. A sequence number is incremented after each renegotiate instead. A sequence number is incremented after each
record: specifically, the first record transmitted under a record: specifically, the first record transmitted under a
particular connection state MUST use sequence number 0. particular connection state MUST use sequence number 0.
6.2. Record layer 6.2. Record layer
The TLS Record Layer receives uninterpreted data from higher layers The TLS Record Layer receives uninterpreted data from higher layers
in non-empty blocks of arbitrary size. in non-empty blocks of arbitrary size.
6.2.1. Fragmentation 6.2.1. Fragmentation
The record layer fragments information blocks into TLSPlaintext The record layer fragments information blocks into TLSPlaintext
records carrying data in chunks of 2^14 bytes or less. Client message records carrying data in chunks of 2^14 bytes or less. Client message
boundaries are not preserved in the record layer (i.e., multiple boundaries are not preserved in the record layer (i.e., multiple
client messages of the same ContentType MAY be coalesced into a client messages of the same ContentType MAY be coalesced into a
single TLSPlaintext record, or a single message MAY be fragmented single TLSPlaintext record, or a single message MAY be fragmented
across several records). across several records).
struct { struct {
uint8 major, minor; uint8 major, minor;
} ProtocolVersion; } ProtocolVersion;
enum { enum {
change_cipher_spec(20), alert(21), handshake(22), change_cipher_spec(20), alert(21), handshake(22),
application_data(23), (255) application_data(23), (255)
} ContentType; } ContentType;
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
opaque fragment[TLSPlaintext.length]; opaque fragment[TLSPlaintext.length];
} TLSPlaintext; } TLSPlaintext;
type type
The higher-level protocol used to process the enclosed fragment. The higher-level protocol used to process the enclosed fragment.
version version
The version of the protocol being employed. This document The version of the protocol being employed. This document
describes TLS Version 1.2, which uses the version { 3, 3 }. The describes TLS Version 1.2, which uses the version { 3, 3 }. The
version value 3.3 is historical, deriving from the use of 3.1 for version value 3.3 is historical, deriving from the use of 3.1 for
TLS 1.0. (See Appendix A.1). Note that a client that supports TLS 1.0. (See Appendix A.1). Note that a client that supports
multiple versions of TLS may not know what version will be multiple versions of TLS may not know what version will be
employed before it receives ServerHello. See Appendix E for employed before it receives ServerHello. See Appendix E for
discussion about what record layer version number should be discussion about what record layer version number should be
employed for ClientHello. employed for ClientHello.
length length
The length (in bytes) of the following TLSPlaintext.fragment. The length (in bytes) of the following TLSPlaintext.fragment. The
The length MUST NOT exceed 2^14. length MUST NOT exceed 2^14.
fragment fragment
The application data. This data is transparent and treated as an The application data. This data is transparent and treated as an
independent block to be dealt with by the higher-level protocol independent block to be dealt with by the higher-level protocol
specified by the type field. specified by the type field.
Implementations MUST NOT send zero-length fragments of Handshake, Implementations MUST NOT send zero-length fragments of Handshake,
Alert, or Change Cipher Spec content types. Zero-length fragments Alert, or Change Cipher Spec content types. Zero-length fragments of
of Application data MAY be sent as they are potentially useful as Application data MAY be sent as they are potentially useful as a
a traffic analysis countermeasure. traffic analysis countermeasure.
Note: Data of different TLS Record layer content types MAY be Note: Data of different TLS Record layer content types MAY be
interleaved. Application data is generally of lower precedence interleaved. Application data is generally of lower precedence for
for transmission than other content types. However, records MUST transmission than other content types. However, records MUST be
be delivered to the network in the same order as they are delivered to the network in the same order as they are protected by
protected by the record layer. Recipients MUST receive and the record layer. Recipients MUST receive and process interleaved
process interleaved application layer traffic during handshakes application layer traffic during handshakes subsequent to the first
subsequent to the first one on a connection. one on a connection.
6.2.2. Record Compression and Decompression 6.2.2. Record Compression and Decompression
All records are compressed using the compression algorithm defined in All records are compressed using the compression algorithm defined in
the current session state. There is always an active compression the current session state. There is always an active compression
algorithm; however, initially it is defined as algorithm; however, initially it is defined as
CompressionMethod.null. The compression algorithm translates a CompressionMethod.null. The compression algorithm translates a
TLSPlaintext structure into a TLSCompressed structure. Compression TLSPlaintext structure into a TLSCompressed structure. Compression
functions are initialized with default state information whenever a functions are initialized with default state information whenever a
connection state is made active. connection state is made active.
Compression must be lossless and may not increase the content length Compression must be lossless and may not increase the content length
by more than 1024 bytes. If the decompression function encounters a by more than 1024 bytes. If the decompression function encounters a
TLSCompressed.fragment that would decompress to a length in excess of TLSCompressed.fragment that would decompress to a length in excess of
2^14 bytes, it MUST report a fatal decompression failure error. 2^14 bytes, it MUST report a fatal decompression failure error.
struct { struct {
ContentType type; /* same as TLSPlaintext.type */ ContentType type; /* same as TLSPlaintext.type */
ProtocolVersion version;/* same as TLSPlaintext.version */ ProtocolVersion version;/* same as TLSPlaintext.version */
uint16 length; uint16 length;
opaque fragment[TLSCompressed.length]; opaque fragment[TLSCompressed.length];
} TLSCompressed; } TLSCompressed;
length length
The length (in bytes) of the following TLSCompressed.fragment. The length (in bytes) of the following TLSCompressed.fragment.
The length MUST NOT exceed 2^14 + 1024. The length MUST NOT exceed 2^14 + 1024.
fragment fragment
The compressed form of TLSPlaintext.fragment. The compressed form of TLSPlaintext.fragment.
Note: A CompressionMethod.null operation is an identity operation; no Note: A CompressionMethod.null operation is an identity operation; no
fields are altered. fields are altered.
Implementation note: Implementation note: Decompression functions are responsible for
Decompression functions are responsible for ensuring that ensuring that messages cannot cause internal buffer overflows.
messages cannot cause internal buffer overflows.
6.2.3. Record Payload Protection 6.2.3. Record Payload Protection
The encryption and MAC functions translate a TLSCompressed structure The encryption and MAC functions translate a TLSCompressed structure
into a TLSCiphertext. The decryption functions reverse the process. into a TLSCiphertext. The decryption functions reverse the process.
The MAC of the record also includes a sequence number so that The MAC of the record also includes a sequence number so that
missing, extra, or repeated messages are detectable. missing, extra, or repeated messages are detectable.
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
select (SecurityParameters.cipher_type) { select (SecurityParameters.cipher_type) {
case stream: GenericStreamCipher; case stream: GenericStreamCipher;
case block: GenericBlockCipher; case block: GenericBlockCipher;
case aead: GenericAEADCipher; case aead: GenericAEADCipher;
} fragment; } fragment;
} TLSCiphertext; } TLSCiphertext;
type type
The type field is identical to TLSCompressed.type. The type field is identical to TLSCompressed.type.
version version
The version field is identical to TLSCompressed.version. The version field is identical to TLSCompressed.version.
length length
The length (in bytes) of the following TLSCiphertext.fragment. The length (in bytes) of the following TLSCiphertext.fragment.
The length MUST NOT exceed 2^14 + 2048. The length MUST NOT exceed 2^14 + 2048.
fragment fragment
The encrypted form of TLSCompressed.fragment, with the MAC. The encrypted form of TLSCompressed.fragment, with the MAC.
6.2.3.1. Null or Standard Stream Cipher 6.2.3.1. Null or Standard Stream Cipher
Stream ciphers (including BulkCipherAlgorithm.null, see Appendix A.6) Stream ciphers (including BulkCipherAlgorithm.null, see Appendix A.6)
convert TLSCompressed.fragment structures to and from stream convert TLSCompressed.fragment structures to and from stream
TLSCiphertext.fragment structures. TLSCiphertext.fragment structures.
stream-ciphered struct { stream-ciphered struct {
opaque content[TLSCompressed.length]; opaque content[TLSCompressed.length];
opaque MAC[SecurityParameters.mac_length]; opaque MAC[SecurityParameters.mac_length];
} GenericStreamCipher; } GenericStreamCipher;
The MAC is generated as: The MAC is generated as:
MAC(MAC_write_secret, seq_num + TLSCompressed.type + MAC(MAC_write_secret, seq_num +
TLSCompressed.version + TLSCompressed.length + TLSCompressed.type +
TLSCompressed.fragment); TLSCompressed.version +
TLSCompressed.length +
TLSCompressed.fragment);
where "+" denotes concatenation. where "+" denotes concatenation.
seq_num seq_num
The sequence number for this record. The sequence number for this record.
MAC MAC
The MAC algorithm specified by SecurityParameters.mac_algorithm. The MAC algorithm specified by SecurityParameters.mac_algorithm.
Note that the MAC is computed before encryption. The stream cipher Note that the MAC is computed before encryption. The stream cipher
encrypts the entire block, including the MAC. For stream ciphers that encrypts the entire block, including the MAC. For stream ciphers that
do not use a synchronization vector (such as RC4), the stream cipher do not use a synchronization vector (such as RC4), the stream cipher
state from the end of one record is simply used on the subsequent state from the end of one record is simply used on the subsequent
packet. If the CipherSuite is TLS_NULL_WITH_NULL_NULL, encryption packet. If the CipherSuite is TLS_NULL_WITH_NULL_NULL, encryption
consists of the identity operation (i.e., the data is not encrypted, consists of the identity operation (i.e., the data is not encrypted,
and the MAC size is zero, implying that no MAC is used). and the MAC size is zero, implying that no MAC is used).
TLSCiphertext.length is TLSCompressed.length plus TLSCiphertext.length is TLSCompressed.length plus
SecurityParameters.mac_length. SecurityParameters.mac_length.
6.2.3.2. CBC Block Cipher 6.2.3.2. CBC Block Cipher
For block ciphers (such as RC2, DES, or AES), the encryption and MAC For block ciphers (such as 3DES, or AES), the encryption and MAC
functions convert TLSCompressed.fragment structures to and from block functions convert TLSCompressed.fragment structures to and from block
TLSCiphertext.fragment structures. TLSCiphertext.fragment structures.
struct { struct {
opaque IV[SecurityParameters.record_iv_length]; opaque IV[SecurityParameters.record_iv_length];
block-ciphered struct { block-ciphered struct {
opaque content[TLSCompressed.length]; opaque content[TLSCompressed.length];
opaque MAC[SecurityParameters.mac_length]; opaque MAC[SecurityParameters.mac_length];
uint8 padding[GenericBlockCipher.padding_length]; uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length; uint8 padding_length;
}; };
} GenericBlockCipher; } GenericBlockCipher;
The MAC is generated as described in Section 6.2.3.1. The MAC is generated as described in Section 6.2.3.1.
IV IV
The Initialization Vector (IV) SHOULD be chosen at random, and The Initialization Vector (IV) SHOULD be chosen at random, and
MUST be unpredictable. Note that in versions of TLS prior to 1.1, MUST be unpredictable. Note that in versions of TLS prior to 1.1,
there was no IV field, and the last ciphertext block of the there was no IV field, and the last ciphertext block of the
previous record (the "CBC residue") was used as the IV. This was previous record (the "CBC residue") was used as the IV. This was
changed to prevent the attacks described in [CBCATT]. For block changed to prevent the attacks described in [CBCATT]. For block
ciphers, the IV length is of length ciphers, the IV length is of length
SecurityParameters.record_iv_length which is equal to the SecurityParameters.record_iv_length which is equal to the
SecurityParameters.block_size. SecurityParameters.block_size.
padding padding
Padding that is added to force the length of the plaintext to be Padding that is added to force the length of the plaintext to be
an integral multiple of the block cipher's block length. The an integral multiple of the block cipher's block length. The
padding MAY be any length up to 255 bytes, as long as it results padding MAY be any length up to 255 bytes, as long as it results
in the TLSCiphertext.length being an integral multiple of the in the TLSCiphertext.length being an integral multiple of the
block length. Lengths longer than necessary might be desirable to block length. Lengths longer than necessary might be desirable to
frustrate attacks on a protocol that are based on analysis of the frustrate attacks on a protocol that are based on analysis of the
lengths of exchanged messages. Each uint8 in the padding data lengths of exchanged messages. Each uint8 in the padding data
vector MUST be filled with the padding length value. The receiver vector MUST be filled with the padding length value. The receiver
MUST check this padding and MUST use the bad_record_mac alert to MUST check this padding and MUST use the bad_record_mac alert to
indicate padding errors. indicate padding errors.
padding_length padding_length
The padding length MUST be such that the total size of the The padding length MUST be such that the total size of the
GenericBlockCipher structure is a multiple of the cipher's block GenericBlockCipher structure is a multiple of the cipher's block
length. Legal values range from zero to 255, inclusive. This length. Legal values range from zero to 255, inclusive. This
length specifies the length of the padding field exclusive of the length specifies the length of the padding field exclusive of the
padding_length field itself. padding_length field itself.
The encrypted data length (TLSCiphertext.length) is one more than the The encrypted data length (TLSCiphertext.length) is one more than the
sum of SecurityParameters.block_length, TLSCompressed.length, sum of SecurityParameters.block_length, TLSCompressed.length,
SecurityParameters.mac_length, and padding_length. SecurityParameters.mac_length, and padding_length.
Example: If the block length is 8 bytes, the content length Example: If the block length is 8 bytes, the content length
(TLSCompressed.length) is 61 bytes, and the MAC length is 20 (TLSCompressed.length) is 61 bytes, and the MAC length is 20 bytes,
bytes, then the length before padding is 82 bytes (this does then the length before padding is 82 bytes (this does not include the
not include the IV. Thus, the padding length modulo 8 must be IV. Thus, the padding length modulo 8 must be equal to 6 in order to
equal to 6 in order to make the total length an even multiple make the total length an even multiple of 8 bytes (the block length).
of 8 bytes (the block length). The padding length can be 6, The padding length can be 6, 14, 22, and so on, through 254. If the
14, 22, and so on, through 254. If the padding length were the padding length were the minimum necessary, 6, the padding would be 6
minimum necessary, 6, the padding would be 6 bytes, each bytes, each containing the value 6. Thus, the last 8 octets of the
containing the value 6. Thus, the last 8 octets of the GenericBlockCipher before block encryption would be xx 06 06 06 06 06
GenericBlockCipher before block encryption would be xx 06 06 06 06, where xx is the last octet of the MAC.
06 06 06 06 06, where xx is the last octet of the MAC.
Note: With block ciphers in CBC mode (Cipher Block Chaining), Note: With block ciphers in CBC mode (Cipher Block Chaining), it is
it is critical that the entire plaintext of the record be known critical that the entire plaintext of the record be known before any
before any ciphertext is transmitted. Otherwise, it is possible ciphertext is transmitted. Otherwise, it is possible for the attacker
for the attacker to mount the attack described in [CBCATT]. to mount the attack described in [CBCATT].
Implementation Note: Canvel et al. [CBCTIME] have demonstrated a timing Implementation Note: Canvel et al. [CBCTIME] have demonstrated a
attack on CBC padding based on the time required to compute the timing attack on CBC padding based on the time required to compute
MAC. In order to defend against this attack, implementations MUST the MAC. In order to defend against this attack, implementations MUST
ensure that record processing time is essentially the same ensure that record processing time is essentially the same whether or
whether or not the padding is correct. In general, the best way not the padding is correct. In general, the best way to do this is
to do this is to compute the MAC even if the padding is to compute the MAC even if the padding is incorrect, and only then
incorrect, and only then reject the packet. For instance, if the reject the packet. For instance, if the pad appears to be incorrect,
pad appears to be incorrect, the implementation might assume a the implementation might assume a zero-length pad and then compute
zero-length pad and then compute the MAC. This leaves a small the MAC. This leaves a small timing channel, since MAC performance
timing channel, since MAC performance depends to some extent on depends to some extent on the size of the data fragment, but it is
the size of the data fragment, but it is not believed to be large not believed to be large enough to be exploitable, due to the large
enough to be exploitable, due to the large block size of existing block size of existing MACs and the small size of the timing signal.
MACs and the small size of the timing signal.
6.2.3.3. AEAD ciphers 6.2.3.3. AEAD ciphers
For AEAD [AEAD] ciphers (such as [CCM] or [GCM]) the AEAD function For AEAD [AEAD] ciphers (such as [CCM] or [GCM]) the AEAD function
converts TLSCompressed.fragment structures to and from AEAD converts TLSCompressed.fragment structures to and from AEAD
TLSCiphertext.fragment structures. TLSCiphertext.fragment structures.
struct { struct {
opaque nonce_explicit[SecurityParameters.record_iv_length]; opaque nonce_explicit[SecurityParameters.record_iv_length];
aead-ciphered struct { aead-ciphered struct {
opaque content[TLSCompressed.length]; opaque content[TLSCompressed.length];
}; };
} GenericAEADCipher; } GenericAEADCipher;
AEAD ciphers take as input a single key, a nonce, a plaintext, and AEAD ciphers take as input a single key, a nonce, a plaintext, and
"additional data" to be included in the authentication check, as "additional data" to be included in the authentication check, as
described in Section 2.1 of [AEAD]. The key is either the described in Section 2.1 of [AEAD]. The key is either the
client_write_key or the server_write_key. No MAC key is used. client_write_key or the server_write_key. No MAC key is used.
Each AEAD cipher suite has to specify how the nonce supplied to the Each AEAD cipher suite MUST specify how the nonce supplied to the
AEAD operation is constructed, and what is the length of the AEAD operation is constructed, and what is the length of the
GenericAEADCipher.nonce_explicit part. In many cases, it is GenericAEADCipher.nonce_explicit part. In many cases, it is
appropriate to use the partially implicit nonce technique described appropriate to use the partially implicit nonce technique described
in Section 3.2.1 of [AEAD]; in this case, the implicit part SHOULD be in Section 3.2.1 of [AEAD]; with record_iv_length being the length of
derived from key_block as client_write_iv and server_write_iv (as the explicit part. In this case, the implicit part SHOULD be derived
described in Section 6.3), and the explicit part is included in from key_block as client_write_iv and server_write_iv (as described
in Section 6.3), and the explicit part is included in
GenericAEAEDCipher.nonce_explicit. GenericAEAEDCipher.nonce_explicit.
The plaintext is the TLSCompressed.fragment. The plaintext is the TLSCompressed.fragment.
The additional authenticated data, which we denote as The additional authenticated data, which we denote as
additional_data, is defined as follows: additional_data, is defined as follows:
additional_data = seq_num + TLSCompressed.type + additional_data = seq_num + TLSCompressed.type +
TLSCompressed.version + TLSCompressed.length; TLSCompressed.version + TLSCompressed.length;
skipping to change at page 99, line ? skipping to change at page 24, line 27
Where "+" denotes concatenation. Where "+" denotes concatenation.
The aead_output consists of the ciphertext output by the AEAD The aead_output consists of the ciphertext output by the AEAD
encryption operation. The length will generally be larger than encryption operation. The length will generally be larger than
TLSCompressed.length, but by an amount that varies with the AEAD TLSCompressed.length, but by an amount that varies with the AEAD
cipher. Since the ciphers might incorporate padding, the amount of cipher. Since the ciphers might incorporate padding, the amount of
overhead could vary with different TLSCompressed.length values. Each overhead could vary with different TLSCompressed.length values. Each
AEAD cipher MUST NOT produce an expansion of greater than 1024 bytes. AEAD cipher MUST NOT produce an expansion of greater than 1024 bytes.
Symbolically, Symbolically,
AEADEncrypted = AEAD-Encrypt(key, IV, plaintext, AEADEncrypted = AEAD-Encrypt(key, IV, plaintext,
additional_data) additional_data)
In order to decrypt and verify, the cipher takes as input the key, In order to decrypt and verify, the cipher takes as input the key,
IV, the "additional_data", and the AEADEncrypted value. The output is IV, the "additional_data", and the AEADEncrypted value. The output is
either the plaintext or an error indicating that the decryption either the plaintext or an error indicating that the decryption
failed. There is no separate integrity check. I.e., failed. There is no separate integrity check. I.e.,
TLSCompressed.fragment = AEAD-Decrypt(write_key, IV, AEADEncrypted, TLSCompressed.fragment = AEAD-Decrypt(write_key, IV,
additional_data) AEADEncrypted,
additional_data)
If the decryption fails, a fatal bad_record_mac alert MUST be If the decryption fails, a fatal bad_record_mac alert MUST be
generated. generated.
6.3. Key Calculation 6.3. Key Calculation
The Record Protocol requires an algorithm to generate keys, and MAC The Record Protocol requires an algorithm to generates keys required
secrets from the security parameters provided by the handshake by the current connection state (see Appendix A.6) from the security
protocol. parameters provided by the handshake protocol.
The master secret is hashed into a sequence of secure bytes, which The master secret is expanded into a sequence of secure bytes, which
are assigned to the MAC secrets and keys required by the current is then split to a client write MAC key, a server write MAC key, a
connection state (see Appendix A.6). CipherSpecs require a client client write encryption key, and a server write encryption key. Each
write MAC secret, a server write MAC secret, a client write key, and of these is generated from the byte sequence in that order. Unused
a server write key, each of which is generated from the master secret values are empty. Some AEAD ciphers may additionally require a
in that order. Unused values are empty. client write IV and a server write IV (see Section 6.2.3.3).
When keys and MAC secrets are generated, the master secret is used as When keys and MAC keys are generated, the master secret is used as an
an entropy source. entropy source.
To generate the key material, compute To generate the key material, compute
key_block = PRF(SecurityParameters.master_secret, key_block = PRF(SecurityParameters.master_secret,
"key expansion", "key expansion",
SecurityParameters.server_random + SecurityParameters.server_random +
SecurityParameters.client_random); SecurityParameters.client_random);
until enough output has been generated. Then the key_block is until enough output has been generated. Then the key_block is
partitioned as follows: partitioned as follows:
client_write_MAC_secret[SecurityParameters.mac_key_length] client_write_MAC_key[SecurityParameters.mac_key_length]
server_write_MAC_secret[SecurityParameters.mac_key_length] server_write_MAC_key[SecurityParameters.mac_key_length]
client_write_key[SecurityParameters.enc_key_length] client_write_key[SecurityParameters.enc_key_length]
server_write_key[SecurityParameters.enc_key_length] server_write_key[SecurityParameters.enc_key_length]
client_write_IV[SecurityParameters.fixed_iv_length] client_write_IV[SecurityParameters.fixed_iv_length]
server_write_IV[SecurityParameters.fixed_iv_length] server_write_IV[SecurityParameters.fixed_iv_length]
The client_write_IV and server_write_IV are only generated for The client_write_IV and server_write_IV are only generated for
implicit nonce techniques as described in Section 3.2.1 of [AEAD]. implicit nonce techniques as described in Section 3.2.1 of [AEAD].
Implementation note: Implementation note: The currently defined cipher suite which
The currently defined cipher suite which requires the most requires the most material is AES_256_CBC_SHA. It requires 2 x 32
material is AES_256_CBC_SHA. It requires 2 x 32 byte keys and 2 x byte keys and 2 x 20 byte MAC keys, for a total 104 bytes of key
20 byte MAC secrets, for a total 104 bytes of key material. material.
7. The TLS Handshaking Protocols 7. The TLS Handshaking Protocols
TLS has three subprotocols that are used to allow peers to agree TLS has three subprotocols that are used to allow peers to agree upon
upon security parameters for the record layer, to authenticate security parameters for the record layer, to authenticate themselves,
themselves, to instantiate negotiated security parameters, and to to instantiate negotiated security parameters, and to report error
report error conditions to each other. conditions to each other.
The Handshake Protocol is responsible for negotiating a session, The Handshake Protocol is responsible for negotiating a session,
which consists of the following items: which consists of the following items:
session identifier session identifier
An arbitrary byte sequence chosen by the server to identify an An arbitrary byte sequence chosen by the server to identify an
active or resumable session state. active or resumable session state.
peer certificate peer certificate
X509v3 [PKIX] certificate of the peer. This element of the X509v3 [PKIX] certificate of the peer. This element of the state
state may be null. may be null.
compression method compression method
The algorithm used to compress data prior to encryption. The algorithm used to compress data prior to encryption.
cipher spec cipher spec
Specifies the bulk data encryption algorithm (such as null, Specifies the bulk data encryption algorithm (such as null, DES,
DES, etc.) and a MAC algorithm (such as MD5 or SHA). It also etc.) and a MAC algorithm (such as MD5 or SHA). It also defines
defines cryptographic attributes such as the mac_length. (See cryptographic attributes such as the mac_length. (See Appendix A.6
Appendix A.6 for formal definition.) for formal definition.)
master secret master secret
48-byte secret shared between the client and server. 48-byte secret shared between the client and server.
is resumable is resumable
A flag indicating whether the session can be used to initiate A flag indicating whether the session can be used to initiate new
new connections. connections.
These items are then used to create security parameters for use by These items are then used to create security parameters for use by
the Record Layer when protecting application data. Many connections the Record Layer when protecting application data. Many connections
can be instantiated using the same session through the resumption can be instantiated using the same session through the resumption
feature of the TLS Handshake Protocol. feature of the TLS Handshake Protocol.
7.1. Change Cipher Spec Protocol 7.1. Change Cipher Spec Protocol
The change cipher spec protocol exists to signal transitions in The change cipher spec protocol exists to signal transitions in
ciphering strategies. The protocol consists of a single message, ciphering strategies. The protocol consists of a single message,
which is encrypted and compressed under the current (not the pending) which is encrypted and compressed under the current (not the pending)
connection state. The message consists of a single byte of value 1. connection state. The message consists of a single byte of value 1.
struct { struct {
enum { change_cipher_spec(1), (255) } type; enum { change_cipher_spec(1), (255) } type;
} ChangeCipherSpec; } ChangeCipherSpec;
The change cipher spec message is sent by both the client and the The change cipher spec message is sent by both the client and the
server to notify the receiving party that subsequent records will be server to notify the receiving party that subsequent records will be
protected under the newly negotiated CipherSpec and keys. Reception protected under the newly negotiated CipherSpec and keys. Reception
of this message causes the receiver to instruct the Record Layer to of this message causes the receiver to instruct the Record Layer to
immediately copy the read pending state into the read current state. immediately copy the read pending state into the read current state.
Immediately after sending this message, the sender MUST instruct the Immediately after sending this message, the sender MUST instruct the
record layer to make the write pending state the write active state. record layer to make the write pending state the write active state.
(See Section 6.1.) The change cipher spec message is sent during the (See Section 6.1.) The change cipher spec message is sent during the
handshake after the security parameters have been agreed upon, but handshake after the security parameters have been agreed upon, but
before the verifying finished message is sent. before the verifying finished message is sent.
Note: If a rehandshake occurs while data is flowing on a connection, Note: If a rehandshake occurs while data is flowing on a connection,
the communicating parties may continue to send data using the old the communicating parties may continue to send data using the old
CipherSpec. However, once the ChangeCipherSpec has been sent, the new CipherSpec. However, once the ChangeCipherSpec has been sent, the new
CipherSpec MUST be used. The first side to send the ChangeCipherSpec CipherSpec MUST be used. The first side to send the ChangeCipherSpec
does not know that the other side has finished computing the new does not know that the other side has finished computing the new
keying material (e.g., if it has to perform a time consuming public keying material (e.g., if it has to perform a time consuming public
key operation). Thus, a small window of time, during which the key operation). Thus, a small window of time, during which the
recipient must buffer the data, MAY exist. In practice, with modern recipient must buffer the data, MAY exist. In practice, with modern
machines this interval is likely to be fairly short. machines this interval is likely to be fairly short.
7.2. Alert Protocol 7.2. Alert Protocol
skipping to change at page 99, line ? skipping to change at page 27, line 27
One of the content types supported by the TLS Record layer is the One of the content types supported by the TLS Record layer is the
alert type. Alert messages convey the severity of the message and a alert type. Alert messages convey the severity of the message and a
description of the alert. Alert messages with a level of fatal result description of the alert. Alert messages with a level of fatal result
in the immediate termination of the connection. In this case, other in the immediate termination of the connection. In this case, other
connections corresponding to the session may continue, but the connections corresponding to the session may continue, but the
session identifier MUST be invalidated, preventing the failed session session identifier MUST be invalidated, preventing the failed session
from being used to establish new connections. Like other messages, from being used to establish new connections. Like other messages,
alert messages are encrypted and compressed, as specified by the alert messages are encrypted and compressed, as specified by the
current connection state. current connection state.
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
unexpected_message(10), unexpected_message(10),
bad_record_mac(20), bad_record_mac(20),
decryption_failed_RESERVED(21), decryption_failed_RESERVED(21),
record_overflow(22), record_overflow(22),
decompression_failure(30), decompression_failure(30),
handshake_failure(40), handshake_failure(40),
no_certificate_RESERVED(41), no_certificate_RESERVED(41),
bad_certificate(42), bad_certificate(42),
unsupported_certificate(43), unsupported_certificate(43),
certificate_revoked(44), certificate_revoked(44),
certificate_expired(45), certificate_expired(45),
certificate_unknown(46), certificate_unknown(46),
illegal_parameter(47), illegal_parameter(47),
unknown_ca(48), unknown_ca(48),
access_denied(49), access_denied(49),
decode_error(50), decode_error(50),
decrypt_error(51), decrypt_error(51),
export_restriction_RESERVED(60), export_restriction_RESERVED(60),
protocol_version(70), protocol_version(70),
insufficient_security(71), insufficient_security(71),
internal_error(80), internal_error(80),
user_canceled(90), user_canceled(90),
no_renegotiation(100), no_renegotiation(100),
unsupported_extension(110), unsupported_extension(110),
(255) (255)
} AlertDescription; } AlertDescription;
struct { struct {
AlertLevel level; AlertLevel level;
AlertDescription description; AlertDescription description;
} Alert; } Alert;
7.2.1. Closure Alerts 7.2.1. Closure Alerts
The client and the server must share knowledge that the connection is The client and the server must share knowledge that the connection is
ending in order to avoid a truncation attack. Either party may ending in order to avoid a truncation attack. Either party may
initiate the exchange of closing messages. initiate the exchange of closing messages.
close_notify close_notify
This message notifies the recipient that the sender will not send This message notifies the recipient that the sender will not send
any more messages on this connection. Note that as of TLS 1.1, any more messages on this connection. Note that as of TLS 1.1,
skipping to change at page 99, line ? skipping to change at page 28, line 51
close_notify alert before indicating to the application layer that close_notify alert before indicating to the application layer that
the TLS connection has ended. If the application protocol will not the TLS connection has ended. If the application protocol will not
transfer any additional data, but will only close the underlying transfer any additional data, but will only close the underlying
transport connection, then the implementation MAY choose to close the transport connection, then the implementation MAY choose to close the
transport without waiting for the responding close_notify. No part of transport without waiting for the responding close_notify. No part of
this standard should be taken to dictate the manner in which a usage this standard should be taken to dictate the manner in which a usage
profile for TLS manages its data transport, including when profile for TLS manages its data transport, including when
connections are opened or closed. connections are opened or closed.
Note: It is assumed that closing a connection reliably delivers Note: It is assumed that closing a connection reliably delivers
pending data before destroying the transport. pending data before destroying the transport.
7.2.2. Error Alerts 7.2.2. Error Alerts
Error handling in the TLS Handshake protocol is very simple. When an Error handling in the TLS Handshake protocol is very simple. When an
error is detected, the detecting party sends a message to the other error is detected, the detecting party sends a message to the other
party. Upon transmission or receipt of a fatal alert message, both party. Upon transmission or receipt of a fatal alert message, both
parties immediately close the connection. Servers and clients MUST parties immediately close the connection. Servers and clients MUST
forget any session-identifiers, keys, and secrets associated with a forget any session-identifiers, keys, and secrets associated with a
failed connection. Thus, any connection terminated with a fatal alert failed connection. Thus, any connection terminated with a fatal alert
MUST NOT be resumed. MUST NOT be resumed.
skipping to change at page 99, line ? skipping to change at page 29, line 31
If an alert with a level of warning is sent and received, generally If an alert with a level of warning is sent and received, generally
the connection can continue normally. If the receiving party decides the connection can continue normally. If the receiving party decides
not to proceed with the connection (e.g., after having received a not to proceed with the connection (e.g., after having received a
no_renegotiation alert that it is not willing to accept), it SHOULD no_renegotiation alert that it is not willing to accept), it SHOULD
send a fatal alert to terminate the connection. send a fatal alert to terminate the connection.
The following error alerts are defined: The following error alerts are defined:
unexpected_message unexpected_message
An inappropriate message was received. This alert is always fatal An inappropriate message was received. This alert is always fatal
and should never be observed in communication between proper and should never be observed in communication between proper
implementations. implementations.
bad_record_mac bad_record_mac
This alert is returned if a record is received with an incorrect This alert is returned if a record is received with an incorrect
MAC. This alert also MUST be returned if an alert is sent because MAC. This alert also MUST be returned if an alert is sent because
a TLSCiphertext decrypted in an invalid way: either it wasn't an a TLSCiphertext decrypted in an invalid way: either it wasn't an
even multiple of the block length, or its padding values, when even multiple of the block length, or its padding values, when
checked, weren't correct. This message is always fatal. checked, weren't correct. This message is always fatal.
decryption_failed_RESERVED decryption_failed_RESERVED
This alert was used in some earlier versions of TLS, and may have This alert was used in some earlier versions of TLS, and may have
permitted certain attacks against the CBC mode [CBCATT]. It MUST permitted certain attacks against the CBC mode [CBCATT]. It MUST
NOT be sent by compliant implementations. NOT be sent by compliant implementations.
record_overflow record_overflow
A TLSCiphertext record was received that had a length more than A TLSCiphertext record was received that had a length more than
2^14+2048 bytes, or a record decrypted to a TLSCompressed record 2^14+2048 bytes, or a record decrypted to a TLSCompressed record
with more than 2^14+1024 bytes. This message is always fatal. with more than 2^14+1024 bytes. This message is always fatal.
decompression_failure decompression_failure
The decompression function received improper input (e.g., data The decompression function received improper input (e.g., data
that would expand to excessive length). This message is always that would expand to excessive length). This message is always
fatal. fatal.
handshake_failure handshake_failure
Reception of a handshake_failure alert message indicates that the Reception of a handshake_failure alert message indicates that the
sender was unable to negotiate an acceptable set of security sender was unable to negotiate an acceptable set of security
parameters given the options available. This is a fatal error. parameters given the options available. This is a fatal error.
no_certificate_RESERVED no_certificate_RESERVED
This alert was used in SSLv3 but not any version of TLS. It MUST This alert was used in SSLv3 but not any version of TLS. It MUST
NOT be sent by compliant implementations. NOT be sent by compliant implementations.
bad_certificate bad_certificate
A certificate was corrupt, contained signatures that did not A certificate was corrupt, contained signatures that did not
verify correctly, etc. verify correctly, etc.
unsupported_certificate unsupported_certificate
A certificate was of an unsupported type. A certificate was of an unsupported type.
certificate_revoked certificate_revoked
A certificate was revoked by its signer. A certificate was revoked by its signer.
certificate_expired certificate_expired
A certificate has expired or is not currently valid. A certificate has expired or is not currently valid.
certificate_unknown certificate_unknown
Some other (unspecified) issue arose in processing the Some other (unspecified) issue arose in processing the
certificate, rendering it unacceptable. certificate, rendering it unacceptable.
illegal_parameter illegal_parameter
A field in the handshake was out of range or inconsistent with A field in the handshake was out of range or inconsistent with
other fields. This message is always fatal. other fields. This message is always fatal.
unknown_ca unknown_ca
A valid certificate chain or partial chain was received, but the A valid certificate chain or partial chain was received, but the
certificate was not accepted because the CA certificate could not certificate was not accepted because the CA certificate could not
be located or couldn't be matched with a known, trusted CA. This be located or couldn't be matched with a known, trusted CA. This
message is always fatal. message is always fatal.
access_denied access_denied
A valid certificate was received, but when access control was A valid certificate was received, but when access control was
applied, the sender decided not to proceed with negotiation. applied, the sender decided not to proceed with negotiation. This
This message is always fatal. message is always fatal.
decode_error decode_error
A message could not be decoded because some field was out of the A message could not be decoded because some field was out of the
specified range or the length of the message was incorrect. This specified range or the length of the message was incorrect. This
message is always fatal. message is always fatal.
decrypt_error decrypt_error
A handshake cryptographic operation failed, including being A handshake cryptographic operation failed, including being unable
unable to correctly verify a signature, decrypt a key exchange, to correctly verify a signature, decrypt a key exchange, or
or validate a finished message. validate a finished message.
export_restriction_RESERVED export_restriction_RESERVED
This alert was used in some earlier versions of TLS. It MUST NOT This alert was used in some earlier versions of TLS. It MUST NOT
be sent by compliant implementations. be sent by compliant implementations.
protocol_version protocol_version
The protocol version the client has attempted to negotiate is The protocol version the client has attempted to negotiate is
recognized but not supported. (For example, old protocol versions recognized but not supported. (For example, old protocol versions
might be avoided for security reasons). This message is always might be avoided for security reasons). This message is always
fatal. fatal.
insufficient_security insufficient_security
Returned instead of handshake_failure when a negotiation has Returned instead of handshake_failure when a negotiation has
failed specifically because the server requires ciphers more failed specifically because the server requires ciphers more
secure than those supported by the client. This message is always secure than those supported by the client. This message is always
fatal. fatal.
internal_error internal_error
An internal error unrelated to the peer or the correctness of the An internal error unrelated to the peer or the correctness of the
protocol (such as a memory allocation failure) makes it protocol (such as a memory allocation failure) makes it impossible
impossible to continue. This message is always fatal. to continue. This message is always fatal.
user_canceled user_canceled
This handshake is being canceled for some reason unrelated to a This handshake is being canceled for some reason unrelated to a
protocol failure. If the user cancels an operation after the protocol failure. If the user cancels an operation after the
handshake is complete, just closing the connection by sending a handshake is complete, just closing the connection by sending a
close_notify is more appropriate. This alert should be followed close_notify is more appropriate. This alert should be followed by
by a close_notify. This message is generally a warning. a close_notify. This message is generally a warning.
no_renegotiation no_renegotiation
Sent by the client in response to a hello request or by the Sent by the client in response to a hello request or by the server
server in response to a client hello after initial handshaking. in response to a client hello after initial handshaking. Either
Either of these would normally lead to renegotiation; when that of these would normally lead to renegotiation; when that is not
is not appropriate, the recipient should respond with this alert. appropriate, the recipient should respond with this alert. At
At that point, the original requester can decide whether to that point, the original requester can decide whether to proceed
proceed with the connection. One case where this would be with the connection. One case where this would be appropriate is
appropriate is where a server has spawned a process to satisfy a where a server has spawned a process to satisfy a request; the
request; the process might receive security parameters (key process might receive security parameters (key length,
length, authentication, etc.) at startup and it might be authentication, etc.) at startup and it might be difficult to
difficult to communicate changes to these parameters after that communicate changes to these parameters after that point. This
point. This message is always a warning. message is always a warning.
unsupported_extension unsupported_extension
sent by clients that receive an extended server hello containing sent by clients that receive an extended server hello containing
an extension that they did not put in the corresponding client an extension that they did not put in the corresponding client
hello. This message is always fatal. hello. This message is always fatal.
For all errors where an alert level is not explicitly specified, the For all errors where an alert level is not explicitly specified, the
sending party MAY determine at its discretion whether this is a fatal sending party MAY determine at its discretion whether this is a fatal
error or not; if an alert with a level of warning is received, the error or not; if an alert with a level of warning is received, the
receiving party MAY decide at its discretion whether to treat this as receiving party MAY decide at its discretion whether to treat this as
a fatal error or not. However, all messages that are transmitted a fatal error or not. However, all messages that are transmitted
with a level of fatal MUST be treated as fatal messages. with a level of fatal MUST be treated as fatal messages.
New Alert values are assigned by IANA as described in Section 12. New Alert values are assigned by IANA as described in Section 12.
skipping to change at page 99, line ? skipping to change at page 32, line 30
The cryptographic parameters of the session state are produced by the The cryptographic parameters of the session state are produced by the
TLS Handshake Protocol, which operates on top of the TLS Record TLS Handshake Protocol, which operates on top of the TLS Record
Layer. When a TLS client and server first start communicating, they Layer. When a TLS client and server first start communicating, they
agree on a protocol version, select cryptographic algorithms, agree on a protocol version, select cryptographic algorithms,
optionally authenticate each other, and use public-key encryption optionally authenticate each other, and use public-key encryption
techniques to generate shared secrets. techniques to generate shared secrets.
The TLS Handshake Protocol involves the following steps: The TLS Handshake Protocol involves the following steps:
- Exchange hello messages to agree on algorithms, exchange random - Exchange hello messages to agree on algorithms, exchange random
values, and check for session resumption. values, and check for session resumption.
- Exchange the necessary cryptographic parameters to allow the - Exchange the necessary cryptographic parameters to allow the
client and server to agree on a premaster secret. client and server to agree on a premaster secret.
- Exchange certificates and cryptographic information to allow the - Exchange certificates and cryptographic information to allow the
client and server to authenticate themselves. client and server to authenticate themselves.
- Generate a master secret from the premaster secret and exchanged - Generate a master secret from the premaster secret and exchanged
random values. random values.
- Provide security parameters to the record layer. - Provide security parameters to the record layer.
- Allow the client and server to verify that their peer has - Allow the client and server to verify that their peer has
calculated the same security parameters and that the handshake calculated the same security parameters and that the handshake
occurred without tampering by an attacker. occurred without tampering by an attacker.
Note that higher layers should not be overly reliant on whether TLS Note that higher layers should not be overly reliant on whether TLS
always negotiates the strongest possible connection between two always negotiates the strongest possible connection between two
peers. There are a number of ways in which a man in the middle peers. There are a number of ways in which a man in the middle
attacker can attempt to make two entities drop down to the least attacker can attempt to make two entities drop down to the least
secure method they support. The protocol has been designed to secure method they support. The protocol has been designed to
minimize this risk, but there are still attacks available: for minimize this risk, but there are still attacks available: for
example, an attacker could block access to the port a secure service example, an attacker could block access to the port a secure service
runs on, or attempt to get the peers to negotiate an unauthenticated runs on, or attempt to get the peers to negotiate an unauthenticated
connection. The fundamental rule is that higher levels must be connection. The fundamental rule is that higher levels must be
skipping to change at page 99, line ? skipping to change at page 34, line 37
Finished --------> Finished -------->
[ChangeCipherSpec] [ChangeCipherSpec]
<-------- Finished <-------- Finished
Application Data <-------> Application Data Application Data <-------> Application Data
Fig. 1. Message flow for a full handshake Fig. 1. Message flow for a full handshake
* Indicates optional or situation-dependent messages that are not * Indicates optional or situation-dependent messages that are not
always sent. always sent.
Note: To help avoid pipeline stalls, ChangeCipherSpec is an Note: To help avoid pipeline stalls, ChangeCipherSpec is an
independent TLS Protocol content type, and is not actually a TLS independent TLS Protocol content type, and is not actually a TLS
handshake message. handshake message.
When the client and server decide to resume a previous session or When the client and server decide to resume a previous session or
duplicate an existing session (instead of negotiating new security duplicate an existing session (instead of negotiating new security
parameters), the message flow is as follows: parameters), the message flow is as follows:
The client sends a ClientHello using the Session ID of the session to The client sends a ClientHello using the Session ID of the session to
be resumed. The server then checks its session cache for a match. If be resumed. The server then checks its session cache for a match. If
a match is found, and the server is willing to re-establish the a match is found, and the server is willing to re-establish the
connection under the specified session state, it will send a connection under the specified session state, it will send a
ServerHello with the same Session ID value. At this point, both ServerHello with the same Session ID value. At this point, both
skipping to change at page 99, line ? skipping to change at page 35, line 33
7.4. Handshake Protocol 7.4. Handshake Protocol
The TLS Handshake Protocol is one of the defined higher-level clients The TLS Handshake Protocol is one of the defined higher-level clients
of the TLS Record Protocol. This protocol is used to negotiate the of the TLS Record Protocol. This protocol is used to negotiate the
secure attributes of a session. Handshake messages are supplied to secure attributes of a session. Handshake messages are supplied to
the TLS Record Layer, where they are encapsulated within one or more the TLS Record Layer, where they are encapsulated within one or more
TLSPlaintext structures, which are processed and transmitted as TLSPlaintext structures, which are processed and transmitted as
specified by the current active session state. specified by the current active session state.
enum { enum {
hello_request(0), client_hello(1), server_hello(2), hello_request(0), client_hello(1), server_hello(2),
certificate(11), server_key_exchange (12), certificate(11), server_key_exchange (12),
certificate_request(13), server_hello_done(14), certificate_request(13), server_hello_done(14),
certificate_verify(15), client_key_exchange(16), certificate_verify(15), client_key_exchange(16),
finished(20), (255) finished(20), (255)
} HandshakeType; } HandshakeType;
struct { struct {
HandshakeType msg_type; /* handshake type */ HandshakeType msg_type; /* handshake type */
uint24 length; /* bytes in message */ uint24 length; /* bytes in message */
select (HandshakeType) { select (HandshakeType) {
case hello_request: HelloRequest; case hello_request: HelloRequest;
case client_hello: ClientHello; case client_hello: ClientHello;
case server_hello: ServerHello; case server_hello: ServerHello;
case certificate: Certificate; case certificate: Certificate;
case server_key_exchange: ServerKeyExchange; case server_key_exchange: ServerKeyExchange;
case certificate_request: CertificateRequest; case certificate_request: CertificateRequest;
case server_hello_done: ServerHelloDone; case server_hello_done: ServerHelloDone;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case client_key_exchange: ClientKeyExchange; case client_key_exchange: ClientKeyExchange;
case finished: Finished; case finished: Finished;
} body; } body;
} Handshake; } Handshake;
The handshake protocol messages are presented below in the order they The handshake protocol messages are presented below in the order they
MUST be sent; sending handshake messages in an unexpected order MUST be sent; sending handshake messages in an unexpected order
results in a fatal error. Unneeded handshake messages can be omitted, results in a fatal error. Unneeded handshake messages can be omitted,
however. Note one exception to the ordering: the Certificate message however. Note one exception to the ordering: the Certificate message
is used twice in the handshake (from server to client, then from is used twice in the handshake (from server to client, then from
client to server), but described only in its first position. The one client to server), but described only in its first position. The one
message that is not bound by these ordering rules is the Hello message that is not bound by these ordering rules is the Hello
Request message, which can be sent at any time, but which SHOULD be Request message, which can be sent at any time, but which SHOULD be
ignored by the client if it arrives in the middle of a handshake. ignored by the client if it arrives in the middle of a handshake.
skipping to change at page 99, line ? skipping to change at page 36, line 34
The hello phase messages are used to exchange security enhancement The hello phase messages are used to exchange security enhancement
capabilities between the client and server. When a new session capabilities between the client and server. When a new session
begins, the Record Layer's connection state encryption, hash, and begins, the Record Layer's connection state encryption, hash, and
compression algorithms are initialized to null. The current compression algorithms are initialized to null. The current
connection state is used for renegotiation messages. connection state is used for renegotiation messages.
7.4.1.1. Hello Request 7.4.1.1. Hello Request
When this message will be sent: When this message will be sent:
The hello request message MAY be sent by the server at any time.
The hello request message MAY be sent by the server at any time.
Meaning of this message: Meaning of this message:
Hello request is a simple notification that the client should
begin the negotiation process anew by sending a client hello
message when convenient. This message is not intended to
establish which side is the client or server but merely to
initiate a new negotiation. Servers SHOULD NOT send a
HelloRequest immediately upon the client's initial connection.
It is the client's job to send a ClientHello at that time.
This message will be ignored by the client if the client is Hello request is a simple notification that the client should
currently negotiating a session. This message may be ignored by begin the negotiation process anew by sending a client hello
the client if it does not wish to renegotiate a session, or the message when convenient. This message is not intended to establish
client may, if it wishes, respond with a no_renegotiation alert. which side is the client or server but merely to initiate a new
Since handshake messages are intended to have transmission negotiation. Servers SHOULD NOT send a HelloRequest immediately
precedence over application data, it is expected that the upon the client's initial connection. It is the client's job to
negotiation will begin before no more than a few records are send a ClientHello at that time.
received from the client. If the server sends a hello request but
does not receive a client hello in response, it may close the
connection with a fatal alert.
After sending a hello request, servers SHOULD NOT repeat the request This message will be ignored by the client if the client is
until the subsequent handshake negotiation is complete. currently negotiating a session. This message may be ignored by
the client if it does not wish to renegotiate a session, or the
client may, if it wishes, respond with a no_renegotiation alert.
Since handshake messages are intended to have transmission
precedence over application data, it is expected that the
negotiation will begin before no more than a few records are
received from the client. If the server sends a hello request but
does not receive a client hello in response, it may close the
connection with a fatal alert.
After sending a hello request, servers SHOULD NOT repeat the
request until the subsequent handshake negotiation is complete.
Structure of this message: Structure of this message:
struct { } HelloRequest;
Note: This message MUST NOT be included in the message hashes that are struct { } HelloRequest;
maintained throughout the handshake and used in the finished
messages and the certificate verify message. Note: This message MUST NOT be included in the message hashes that
are maintained throughout the handshake and used in the finished
messages and the certificate verify message.
7.4.1.2. Client Hello 7.4.1.2. Client Hello
When this message will be sent: When this message will be sent:
When a client first connects to a server it is required to send
the client hello as its first message. The client can also send a When a client first connects to a server it is required to send
client hello in response to a hello request or on its own the client hello as its first message. The client can also send a
initiative in order to renegotiate the security parameters in an client hello in response to a hello request or on its own
existing connection. initiative in order to renegotiate the security parameters in an
existing connection.
Structure of this message: Structure of this message:
The client hello message includes a random structure, which is
used later in the protocol.
struct { The client hello message includes a random structure, which is
uint32 gmt_unix_time; used later in the protocol.
opaque random_bytes[28];
} Random;
gmt_unix_time struct {
The current time and date in standard UNIX 32-bit format (seconds uint32 gmt_unix_time;
since the midnight starting Jan 1, 1970, GMT, ignoring leap opaque random_bytes[28];
seconds) according to the sender's internal clock. Clocks are not } Random;
required to be set correctly by the basic TLS Protocol; higher-
level or application protocols may define additional
requirements.
random_bytes gmt_unix_time
28 bytes generated by a secure random number generator. The current time and date in standard UNIX 32-bit format
(seconds since the midnight starting Jan 1, 1970, GMT, ignoring
leap seconds) according to the sender's internal clock. Clocks
are not required to be set correctly by the basic TLS Protocol;
higher-level or application protocols may define additional
requirements.
random_bytes
28 bytes generated by a secure random number generator.
The client hello message includes a variable-length session The client hello message includes a variable-length session
identifier. If not empty, the value identifies a session between the identifier. If not empty, the value identifies a session between the
same client and server whose security parameters the client wishes to same client and server whose security parameters the client wishes to
reuse. The session identifier MAY be from an earlier connection, this reuse. The session identifier MAY be from an earlier connection, this
connection, or from another currently active connection. The second connection, or from another currently active connection. The second
option is useful if the client only wishes to update the random option is useful if the client only wishes to update the random
structures and derived values of a connection, and the third option structures and derived values of a connection, and the third option
makes it possible to establish several independent secure connections makes it possible to establish several independent secure connections
without repeating the full handshake protocol. These independent without repeating the full handshake protocol. These independent
connections may occur sequentially or simultaneously; a SessionID connections may occur sequentially or simultaneously; a SessionID
becomes valid when the handshake negotiating it completes with the becomes valid when the handshake negotiating it completes with the
exchange of Finished messages and persists until it is removed due to exchange of Finished messages and persists until it is removed due to
aging or because a fatal error was encountered on a connection aging or because a fatal error was encountered on a connection
associated with the session. The actual contents of the SessionID are associated with the session. The actual contents of the SessionID are
defined by the server. defined by the server.
opaque SessionID<0..32>; opaque SessionID<0..32>;
Warning: Warning: Because the SessionID is transmitted without encryption or
Because the SessionID is transmitted without encryption or immediate MAC protection, servers MUST NOT place confidential
immediate MAC protection, servers MUST NOT place confidential information in session identifiers or let the contents of fake
information in session identifiers or let the contents of fake session identifiers cause any breach of security. (Note that the
session identifiers cause any breach of security. (Note that the content of the handshake as a whole, including the SessionID, is
content of the handshake as a whole, including the SessionID, is protected by the Finished messages exchanged at the end of the
protected by the Finished messages exchanged at the end of the handshake.)
handshake.)
The CipherSuite list, passed from the client to the server in the The CipherSuite list, passed from the client to the server in the
client hello message, contains the combinations of cryptographic client hello message, contains the combinations of cryptographic
algorithms supported by the client in order of the client's algorithms supported by the client in order of the client's
preference (favorite choice first). Each CipherSuite defines a key preference (favorite choice first). Each CipherSuite defines a key
exchange algorithm, a bulk encryption algorithm (including secret key exchange algorithm, a bulk encryption algorithm (including secret key
length), a MAC algorithm, and a PRF. The server will select a cipher length), a MAC algorithm, and a PRF. The server will select a cipher
suite or, if no acceptable choices are presented, return a handshake suite or, if no acceptable choices are presented, return a handshake
failure alert and close the connection. failure alert and close the connection.
uint8 CipherSuite[2]; /* Cryptographic suite selector */ uint8 CipherSuite[2]; /* Cryptographic suite selector */
The client hello includes a list of compression algorithms supported The client hello includes a list of compression algorithms supported
by the client, ordered according to the client's preference. by the client, ordered according to the client's preference.
enum { null(0), (255) } CompressionMethod; enum { null(0), (255) } CompressionMethod;
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suites<2..2^16-2>; CipherSuite cipher_suites<2..2^16-2>;
CompressionMethod compression_methods<1..2^8-1>; CompressionMethod compression_methods<1..2^8-1>;
select (extensions_present) { select (extensions_present) {
case false: case false:
struct {}; struct {};
case true: case true:
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
}; };
} ClientHello; } ClientHello;
TLS allows extensions to follow the compression_methods field in an TLS allows extensions to follow the compression_methods field in an
extensions block. The presence of extensions can be detected by extensions block. The presence of extensions can be detected by
determining whether there are bytes following the compression_methods determining whether there are bytes following the compression_methods
at the end of the ClientHello. Note that this method of detecting at the end of the ClientHello. Note that this method of detecting
optional data differs from the normal TLS method of having a optional data differs from the normal TLS method of having a
variable-length field but is used for compatibility with TLS before variable-length field but is used for compatibility with TLS before
extensions were defined. extensions were defined.
client_version client_version
The version of the TLS protocol by which the client wishes to The version of the TLS protocol by which the client wishes to
communicate during this session. This SHOULD be the latest communicate during this session. This SHOULD be the latest
(highest valued) version supported by the client. For this (highest valued) version supported by the client. For this version
version of the specification, the version will be 3.3 (See of the specification, the version will be 3.3 (See Appendix E for
Appendix E for details about backward compatibility). details about backward compatibility).
random random
A client-generated random structure. A client-generated random structure.
session_id session_id
The ID of a session the client wishes to use for this connection. The ID of a session the client wishes to use for this connection.
This field is empty if no session_id is available, or it the This field is empty if no session_id is available, or it the
client wishes to generate new security parameters. client wishes to generate new security parameters.
cipher_suites cipher_suites
This is a list of the cryptographic options supported by the This is a list of the cryptographic options supported by the
client, with the client's first preference first. If the client, with the client's first preference first. If the
session_id field is not empty (implying a session resumption session_id field is not empty (implying a session resumption
request) this vector MUST include at least the cipher_suite from request) this vector MUST include at least the cipher_suite from
that session. Values are defined in Appendix A.5. that session. Values are defined in Appendix A.5.
compression_methods compression_methods
This is a list of the compression methods supported by the This is a list of the compression methods supported by the client,
client, sorted by client preference. If the session_id field is sorted by client preference. If the session_id field is not empty
not empty (implying a session resumption request) it MUST include (implying a session resumption request) it MUST include the
the compression_method from that session. This vector MUST compression_method from that session. This vector MUST contain,
contain, and all implementations MUST support, and all implementations MUST support, CompressionMethod.null.
CompressionMethod.null. Thus, a client and server will always be Thus, a client and server will always be able to agree on a
able to agree on a compression method. compression method.
client_hello_extension_list client_hello_extension_list
Clients MAY request extended functionality from servers by Clients MAY request extended functionality from servers by sending
sending data in the client_hello_extension_list. Here the new data in the client_hello_extension_list. Here the new
"client_hello_extension_list" field contains a list of "client_hello_extension_list" field contains a list of extensions.
extensions. The actual "Extension" format is defined in Section The actual "Extension" format is defined in Section 7.4.1.4.
7.4.1.4.
In the event that a client requests additional functionality using In the event that a client requests additional functionality using
extensions, and this functionality is not supplied by the server, the extensions, and this functionality is not supplied by the server, the
client MAY abort the handshake. A server that supports the client MAY abort the handshake. A server that supports the
extensions mechanism MUST accept client hello messages in either the extensions mechanism MUST accept client hello messages in either the
original (TLS 1.0/TLS 1.1) ClientHello or the extended ClientHello original (TLS 1.0/TLS 1.1) ClientHello or the extended ClientHello
format defined in this document, and (as for all other messages) MUST format defined in this document, and (as for all other messages) MUST
check that the amount of data in the message precisely matches one of check that the amount of data in the message precisely matches one of
these formats; if not then it MUST send a fatal "decode_error" alert. these formats; if not then it MUST send a fatal "decode_error" alert.
After sending the client hello message, the client waits for a server After sending the client hello message, the client waits for a server
hello message. Any other handshake message returned by the server hello message. Any other handshake message returned by the server
except for a hello request is treated as a fatal error. except for a hello request is treated as a fatal error.
7.4.1.3. Server Hello 7.4.1.3. Server Hello
When this message will be sent: When this message will be sent:
The server will send this message in response to a client hello
message when it was able to find an acceptable set of algorithms. The server will send this message in response to a client hello
If it cannot find such a match, it will respond with a handshake message when it was able to find an acceptable set of algorithms.
failure alert. If it cannot find such a match, it will respond with a handshake
failure alert.
Structure of this message: Structure of this message:
struct {
ProtocolVersion server_version; struct {
Random random; ProtocolVersion server_version;
SessionID session_id; Random random;
CipherSuite cipher_suite; SessionID session_id;
CompressionMethod compression_method; CipherSuite cipher_suite;
select (extensions_present) { CompressionMethod compression_method;
case false: select (extensions_present) {
struct {}; case false:
case true: struct {};
Extension extensions<0..2^16-1>; case true:
}; Extension extensions<0..2^16-1>;
} ServerHello; };
} ServerHello;
The presence of extensions can be detected by determining whether The presence of extensions can be detected by determining whether
there are bytes following the compression_method field at the end of there are bytes following the compression_method field at the end of
the ServerHello. the ServerHello.
server_version server_version
This field will contain the lower of that suggested by the client This field will contain the lower of that suggested by the client
in the client hello and the highest supported by the server. For in the client hello and the highest supported by the server. For
this version of the specification, the version is 3.3. (See this version of the specification, the version is 3.3. (See
Appendix E for details about backward compatibility.) Appendix E for details about backward compatibility.)
random random
This structure is generated by the server and MUST be This structure is generated by the server and MUST be
independently generated from the ClientHello.random. independently generated from the ClientHello.random.
session_id session_id
This is the identity of the session corresponding to this This is the identity of the session corresponding to this
connection. If the ClientHello.session_id was non-empty, the connection. If the ClientHello.session_id was non-empty, the
server will look in its session cache for a match. If a match is server will look in its session cache for a match. If a match is
found and the server is willing to establish the new connection found and the server is willing to establish the new connection
using the specified session state, the server will respond with using the specified session state, the server will respond with
the same value as was supplied by the client. This indicates a the same value as was supplied by the client. This indicates a
resumed session and dictates that the parties must proceed resumed session and dictates that the parties must proceed
directly to the finished messages. Otherwise this field will directly to the finished messages. Otherwise this field will
contain a different value identifying the new session. The server contain a different value identifying the new session. The server
may return an empty session_id to indicate that the session will may return an empty session_id to indicate that the session will
not be cached and therefore cannot be resumed. If a session is not be cached and therefore cannot be resumed. If a session is
resumed, it must be resumed using the same cipher suite it was resumed, it must be resumed using the same cipher suite it was
originally negotiated with. Note that there is no requirement originally negotiated with. Note that there is no requirement that
that the server resume any session even if it had formerly the server resume any session even if it had formerly provided a
provided a session_id. Client MUST be prepared to do a full session_id. Client MUST be prepared to do a full negotiation --
negotiation -- including negotiating new cipher suites -- during including negotiating new cipher suites -- during any handshake.
any handshake.
cipher_suite cipher_suite
The single cipher suite selected by the server from the list in The single cipher suite selected by the server from the list in
ClientHello.cipher_suites. For resumed sessions, this field is ClientHello.cipher_suites. For resumed sessions, this field is the
the value from the state of the session being resumed. value from the state of the session being resumed.
compression_method compression_method
The single compression algorithm selected by the server from the The single compression algorithm selected by the server from the
list in ClientHello.compression_methods. For resumed sessions list in ClientHello.compression_methods. For resumed sessions this
this field is the value from the resumed session state. field is the value from the resumed session state.
server_hello_extension_list server_hello_extension_list
A list of extensions. Note that only extensions offered by the A list of extensions. Note that only extensions offered by the
client can appear in the server's list. client can appear in the server's list.
7.4.1.4 Hello Extensions 7.4.1.4 Hello Extensions
The extension format is: The extension format is:
struct { struct {
ExtensionType extension_type; ExtensionType extension_type;
opaque extension_data<0..2^16-1>; opaque extension_data<0..2^16-1>;
} Extension; } Extension;
enum { enum {
signature_hash_algorithms(TBD-BY-IANA), (65535) signature_algorithms(TBD-BY-IANA), (65535)
} ExtensionType; } ExtensionType;
Here: Here:
- "extension_type" identifies the particular extension type. - "extension_type" identifies the particular extension type.
- "extension_data" contains information specific to the particular - "extension_data" contains information specific to the particular
extension type. extension type.
The initial set of extensions is defined in a companion document The initial set of extensions is defined in a companion document
[TLSEXT]. The list of extension types is maintained by IANA as [TLSEXT]. The list of extension types is maintained by IANA as
described in Section 12. described in Section 12.
There are subtle (and not so subtle) interactions that may occur in There are subtle (and not so subtle) interactions that may occur in
this protocol between new features and existing features which may this protocol between new features and existing features which may
result in a significant reduction in overall security, The following result in a significant reduction in overall security, The following
considerations should be taken into account when designing new considerations should be taken into account when designing new
extensions: extensions:
- Some cases where a server does not agree to an extension are - Some cases where a server does not agree to an extension are error
error conditions, and some simply a refusal to support a conditions, and some simply a refusal to support a particular
particular feature. In general error alerts should be used for feature. In general error alerts should be used for the former,
the former, and a field in the server extension response for the and a field in the server extension response for the latter.
latter.
- Extensions should as far as possible be designed to prevent any - Extensions should as far as possible be designed to prevent any
attack that forces use (or non-use) of a particular feature by attack that forces use (or non-use) of a particular feature by
manipulation of handshake messages. This principle should be manipulation of handshake messages. This principle should be
followed regardless of whether the feature is believed to cause a followed regardless of whether the feature is believed to cause a
security problem. security problem.
Often the fact that the extension fields are included in the Often the fact that the extension fields are included in the
inputs to the Finished message hashes will be sufficient, but inputs to the Finished message hashes will be sufficient, but
extreme care is needed when the extension changes the meaning of extreme care is needed when the extension changes the meaning of
messages sent in the handshake phase. Designers and implementors messages sent in the handshake phase. Designers and implementors
should be aware of the fact that until the handshake has been should be aware of the fact that until the handshake has been
authenticated, active attackers can modify messages and insert, authenticated, active attackers can modify messages and insert,
remove, or replace extensions. remove, or replace extensions.
- It would be technically possible to use extensions to change - It would be technically possible to use extensions to change major
major aspects of the design of TLS; for example the design of aspects of the design of TLS; for example the design of cipher
cipher suite negotiation. This is not recommended; it would be suite negotiation. This is not recommended; it would be more
more appropriate to define a new version of TLS - particularly appropriate to define a new version of TLS - particularly since
since the TLS handshake algorithms have specific protection the TLS handshake algorithms have specific protection against
against version rollback attacks based on the version number, and version rollback attacks based on the version number, and the
the possibility of version rollback should be a significant possibility of version rollback should be a significant
consideration in any major design change. consideration in any major design change.
7.4.1.4.1 Signature Hash Algorithms 7.4.1.4.1 Signature Algorithms
The client MAY use the "signature_hash_algorithms" to indicate to the The client MAY use the "signature_algorithms" extension to indicate
server which signature/hash algorithm pairs may be used in digital to the server which signature/hash algorithm pairs may be used in
signatures. The "extension_data" field of this extension contains a digital signatures. The "extension_data" field of this extension
"supported_signature_algorithms" value. contains a "supported_signature_algorithms" value.
enum{ enum {
none(0), md5(1), sha1(2), sha256(3), sha384(4), none(0), md5(1), sha1(2), sha256(3), sha384(4),
sha512(5), (255) sha512(5), (255)
} HashAlgorithm; } HashAlgorithm;
enum { anonymous(0), rsa(1), dsa(2), (255) } SignatureAlgorithm; enum { anonymous(0), rsa(1), dsa(2), ecdsa(3), (255) }
SignatureAlgorithm;
struct { struct {
HashAlgorithm hash; HashAlgorithm hash;
SignatureAlgorithm signature; SignatureAlgorithm signature;
} SignatureAndHashAlgorithm; } SignatureAndHashAlgorithm;
SignatureAndHashAlgorithm SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-1>; supported_signature_algorithms<2..2^16-1>;
Each SignatureAndHashAlgorithm value lists a single digest/signature Each SignatureAndHashAlgorithm value lists a single hash/signature
pair which the client is willing to verify. The values are indicated pair which the client is willing to verify. The values are indicated
in descending order of preference. in descending order of preference.
Note: Because not all signature algorithms and hash algorithms may be Note: Because not all signature algorithms and hash algorithms may be
accepted by an implementation (e.g., DSA with SHA-1, but not accepted by an implementation (e.g., DSA with SHA-1, but not
SHA-256), algorithms here are listed in pairs. SHA-256), algorithms here are listed in pairs.
hash hash
This field indicates the hash algorithm which may be used. The This field indicates the hash algorithm which may be used. The
values indicate support for undigested data, MD5 [MD5], SHA-1, values indicate support for unhashed data, MD5 [MD5], SHA-1,
SHA-256, SHA-384, and SHA-512 [SHA] respectively. The "none" SHA-256, SHA-384, and SHA-512 [SHA] respectively. The "none" value
value is provided for future extensibility, in case of a is provided for future extensibility, in case of a signature
signature algorithm which does not require hashing before algorithm which does not require hashing before signing.
signing.
signature signature
This field indicates the signature algorithm which may be used. This field indicates the signature algorithm which may be used.
The values indicate anonymous signatures, RSA [PKCS1] and DSA The values indicate anonymous signatures, RSA [PKCS1] and DSA
[DSS] respectively. The "anonymous" value is meaningless in this [DSS] respectively. The "anonymous" value is meaningless in this
context but used later in the specification. It MUST NOT appear context but used later in the specification. It MUST NOT appear in
in this extension. this extension.
The semantics of this extension are somewhat complicated because the The semantics of this extension are somewhat complicated because the
cipher suite indicates permissible signature algorithms but not cipher suite indicates permissible signature algorithms but not hash
digest algorithm. Sections 7.4.2 and 7.4.3 describe the appropriate algorithm. Sections 7.4.2 and 7.4.3 describe the appropriate rules.
rules.
Clients SHOULD send this extension if they support any digest Clients SHOULD send this extension if they support any hash algorithm
algorithm other than SHA-1. If this extension is not used, servers other than SHA-1.
SHOULD assume that the client supports only SHA-1. Note: this is a
change from TLS 1.1 where there are no explicit rules but as a If the client does not send the signature_algorithms extension, the
practical matter one can assume that the peer supports MD5 and SHA-1. server SHOULD assume the following:
- If the negotiated key exchange algorithm is one of (RSA, DHE_RSA,
DH_RSA, RSA_PSK, ECDH_RSA, ECDHE_RSA), behave as if client had sent
the value (sha1,rsa).
- If the negotiated key exchange algorithm is one of (DHE_DSS,
DH_DSS), behave as if the client had sent the value (sha1,dsa).
- If the negotiated key exchnage algorithm is one of (ECDH_ECDSA,
ECDHE_ECDSA), behave as if the client had sent value (sha1,ecdsa).
Note: this is a change from TLS 1.1 where there are no explicit rules
but as a practical matter one can assume that the peer supports MD5
and SHA-1.
Servers MUST NOT send this extension. Servers MUST NOT send this extension.
7.4.2. Server Certificate 7.4.2. Server Certificate
When this message will be sent: When this message will be sent:
The server MUST send a certificate whenever the agreed-upon key
exchange method uses certificates for authentication (this The server MUST send a certificate whenever the agreed-upon key
includes all key exchange methods defined in this document except exchange method uses certificates for authentication (this
DH_anon). This message will always immediately follow the server includes all key exchange methods defined in this document except
hello message. DH_anon). This message will always immediately follow the server
hello message.
Meaning of this message: Meaning of this message:
This message conveys the server's certificate to the client. The
certificate MUST be appropriate for the negotiated cipher suite's This message conveys the server's certificate to the client. The
key exchange algorithm, and any negotiated extensions. certificate MUST be appropriate for the negotiated cipher suite's
key exchange algorithm, and any negotiated extensions.
Structure of this message: Structure of this message:
opaque ASN.1Cert<1..2^24-1>;
struct {
ASN.1Cert certificate_list<0..2^24-1>;
} Certificate;
certificate_list opaque ASN.1Cert<1..2^24-1>;
This is a sequence (chain) of certificates. The sender's struct {
certificate MUST come first in the list. Each following ASN.1Cert certificate_list<0..2^24-1>;
certificate MUST directly certify the one preceding it. Because } Certificate;
certificate validation requires that root keys be distributed
independently, the self-signed certificate that specifies the certificate_list
root certificate authority MAY optionally be omitted from the This is a sequence (chain) of certificates. The sender's
chain, under the assumption that the remote end must already certificate MUST come first in the list. Each following
possess it in order to validate it in any case. certificate MUST directly certify the one preceding it. Because
certificate validation requires that root keys be distributed
independently, the self-signed certificate that specifies the root
certificate authority MAY optionally be omitted from the chain,
under the assumption that the remote end must already possess it
in order to validate it in any case.
The same message type and structure will be used for the client's The same message type and structure will be used for the client's
response to a certificate request message. Note that a client MAY response to a certificate request message. Note that a client MAY
send no certificates if it does not have an appropriate certificate send no certificates if it does not have an appropriate certificate
to send in response to the server's authentication request. to send in response to the server's authentication request.
Note: PKCS #7 [PKCS7] is not used as the format for the certificate Note: PKCS #7 [PKCS7] is not used as the format for the certificate
vector because PKCS #6 [PKCS6] extended certificates are not vector because PKCS #6 [PKCS6] extended certificates are not used.
used. Also, PKCS #7 defines a SET rather than a SEQUENCE, making Also, PKCS #7 defines a SET rather than a SEQUENCE, making the task
the task of parsing the list more difficult. of parsing the list more difficult.
The following rules apply to the certificates sent by the server: The following rules apply to the certificates sent by the server:
- The certificate type MUST be X.509v3, unless explicitly - The certificate type MUST be X.509v3, unless explicitly negotiated
negotiated otherwise (e.g., [TLSPGP]). otherwise (e.g., [TLSPGP]).
- The certificate's public key (and associated restrictions) - The certificate's public key (and associated restrictions) MUST be
MUST be compatible with the selected key exchange compatible with the selected key exchange algorithm.
algorithm.
Key Exchange Alg. Certificate Key Type Key Exchange Alg. Certificate Key Type
RSA RSA public key; the certificate MUST RSA RSA public key; the certificate MUST
RSA_PSK allow the key to be used for encryption RSA_PSK allow the key to be used for encryption
(the keyEncipherment bit MUST be set (the keyEncipherment bit MUST be set
if the key usage extension is present). if the key usage extension is present).
Note: RSA_PSK is defined in [TLSPSK]. Note: RSA_PSK is defined in [TLSPSK].
DHE_RSA RSA public key; the certificate MUST DHE_RSA RSA public key; the certificate MUST
skipping to change at page 99, line ? skipping to change at page 46, line 29
by the client, as described in [TLSECC]. by the client, as described in [TLSECC].
ECDHE_ECDSA ECDSA-capable public key; the certificate ECDHE_ECDSA ECDSA-capable public key; the certificate
MUST allow the key to be used for signing MUST allow the key to be used for signing
with the hash algorithm that will be with the hash algorithm that will be
employed in the server key exchange employed in the server key exchange
message. The public key MUST use a curve message. The public key MUST use a curve
and point format supported by the client, and point format supported by the client,
as described in [TLSECC]. as described in [TLSECC].
- The "server_name" and "trusted_ca_keys" extensions - The "server_name" and "trusted_ca_keys" extensions [4366bis] are
[4366bis] are used to guide certificate selection. used to guide certificate selection.
If the client provided a "signature_algorithms" extension, then all If the client provided a "signature_algorithms" extension, then all
certificates provided by the server MUST be signed by a certificates provided by the server MUST be signed by a
digest/signature algorithm pair that appears in that extension. Note hash/signature algorithm pair that appears in that extension. Note
that this implies that a certificate containing a key for one that this implies that a certificate containing a key for one
signature algorithm MAY be signed using a different signature signature algorithm MAY be signed using a different signature
algorithm (for instance, an RSA key signed with a DSA key.) This is a algorithm (for instance, an RSA key signed with a DSA key.) This is a
departure from TLS 1.1, which required that the algorithms be the departure from TLS 1.1, which required that the algorithms be the
same. Note that this also implies that the DH_DS, DH_RSA, same. Note that this also implies that the DH_DSS, DH_RSA,
ECDH_ECDSA, and ECDH_RSA key exchange algorithms do not restrict the ECDH_ECDSA, and ECDH_RSA key exchange algorithms do not restrict the
algorithm used to sign the certificate. Fixed DH certificates MAY be algorithm used to sign the certificate. Fixed DH certificates MAY be
signed with any digest/signature algorithm pair appearing in the signed with any hash/signature algorithm pair appearing in the
extension. The naming is historical. extension. The naming is historical.
If no "signature_algorithms" extension is present, the end-entity
certificate MUST be signed as follows:
Key Exchange Alg. Signature Algorithm Used by Issuer
RSA RSA (RSASSA-PKCS1-v1_5)
DHE_RSA
DH_RSA
RSA_PSK
ECDH_RSA
ECDHE_RSA
DHE_DSS DSA
DH_DSS
ECDH_ECDSA ECDSA
ECDHE_ECDSA
If the server has multiple certificates, it chooses one of them based If the server has multiple certificates, it chooses one of them based
on the above-mentioned criteria (in addition to other criteria, such on the above-mentioned criteria (in addition to other criteria, such
as transport layer endpoint, local configuration and preferences, as transport layer endpoint, local configuration and preferences,
etc.). etc.).
Note that there are certificates that use algorithms and/or algorithm Note that there are certificates that use algorithms and/or algorithm
combinations that cannot be currently used with TLS. For example, a combinations that cannot be currently used with TLS. For example, a
certificate with RSASSA-PSS signature key (id-RSASSA-PSS OID in certificate with RSASSA-PSS signature key (id-RSASSA-PSS OID in
SubjectPublicKeyInfo) cannot be used because TLS defines no SubjectPublicKeyInfo) cannot be used because TLS defines no
corresponding signature algorithm. corresponding signature algorithm.
As CipherSuites that specify new key exchange methods are specified As CipherSuites that specify new key exchange methods are specified
for the TLS Protocol, they will imply certificate format and the for the TLS Protocol, they will imply certificate format and the
required encoded keying information. required encoded keying information.
7.4.3. Server Key Exchange Message 7.4.3. Server Key Exchange Message
When this message will be sent: When this message will be sent:
This message will be sent immediately after the server
certificate message (or the server hello message, if this is an
anonymous negotiation).
The server key exchange message is sent by the server only when This message will be sent immediately after the server certificate
the server certificate message (if sent) does not contain enough message (or the server hello message, if this is an anonymous
data to allow the client to exchange a premaster secret. This is negotiation).
true for the following key exchange methods:
DHE_DSS The server key exchange message is sent by the server only when
DHE_RSA the server certificate message (if sent) does not contain enough
DH_anon data to allow the client to exchange a premaster secret. This is
true for the following key exchange methods:
It is not legal to send the server key exchange message for the DHE_DSS
following key exchange methods: DHE_RSA
DH_anon
It is not legal to send the server key exchange message for the
following key exchange methods:
RSA
DH_DSS
DH_RSA
RSA
DH_DSS
DH_RSA
Meaning of this message: Meaning of this message:
This message conveys cryptographic information to allow the
client to communicate the premaster secret: a Diffie-Hellman This message conveys cryptographic information to allow the client
public key with which the client can complete a key exchange to communicate the premaster secret: a Diffie-Hellman public key
(with the result being the premaster secret) or a public key for with which the client can complete a key exchange (with the result
some other algorithm. being the premaster secret) or a public key for some other
algorithm.
Structure of this message: Structure of this message:
enum { diffie_hellman, rsa} KeyExchangeAlgorithm;
struct { enum { diffie_hellman, rsa } KeyExchangeAlgorithm;
opaque dh_p<1..2^16-1>;
opaque dh_g<1..2^16-1>;
opaque dh_Ys<1..2^16-1>;
} ServerDHParams; /* Ephemeral DH parameters */
dh_p struct {
The prime modulus used for the Diffie-Hellman operation. opaque dh_p<1..2^16-1>;
opaque dh_g<1..2^16-1>;
opaque dh_Ys<1..2^16-1>;
dh_g } ServerDHParams; /* Ephemeral DH parameters */
The generator used for the Diffie-Hellman operation.
dh_Ys dh_p
The server's Diffie-Hellman public value (g^X mod p). The prime modulus used for the Diffie-Hellman operation.
struct { dh_g
select (KeyExchangeAlgorithm) { The generator used for the Diffie-Hellman operation.
case diffie_hellman:
ServerDHParams params;
Signature signed_params;
};
} ServerKeyExchange;
struct { dh_Ys
select (KeyExchangeAlgorithm) { The server's Diffie-Hellman public value (g^X mod p).
case diffie_hellman:
ServerDHParams params;
};
} ServerParams;
params struct {
The server's key exchange parameters. select (KeyExchangeAlgorithm) {
case diffie_hellman:
ServerDHParams params;
Signature signed_params;
};
} ServerKeyExchange;
signed_params struct {
For non-anonymous key exchanges, a hash of the corresponding select (KeyExchangeAlgorithm) {
params value, with the signature appropriate to that hash case diffie_hellman:
applied. ServerDHParams params;
};
} ServerParams;
hash params
Hash(ClientHello.random + ServerHello.random + ServerParams) The server's key exchange parameters.
struct { signed_params
select (SignatureAlgorithm) { For non-anonymous key exchanges, a hash of the corresponding
case anonymous: struct { }; params value, with the signature appropriate to that hash
case rsa: applied.
SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
digitally-signed struct { hash
opaque hash[Hash.length]; Hash(ClientHello.random + ServerHello.random + ServerParams)
}; where Hash is the chosen hash value and Hash.length is
case dsa: its output.
SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
digitally-signed struct { struct {
opaque hash[Hash.length]; select (SignatureAlgorithm) {
}; case anonymous: struct { };
}; case rsa:
}; SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
} Signature; digitally-signed struct {
opaque hash[Hash.length];
};
case dsa:
SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
digitally-signed struct {
opaque hash[Hash.length];
};
};
};
} Signature;
If the client has offered the "signature_algorithms" extension, the If the client has offered the "signature_algorithms" extension, the
signature algorithm and digest algorithm MUST be a pair listed in signature algorithm and hash algorithm MUST be a pair listed in that
that extension. Note that there is a possibility for inconsistencies extension. Note that there is a possibility for inconsistencies here.
here. For instance, the client might offer DHE_DSS key exchange but For instance, the client might offer DHE_DSS key exchange but omit
omit any DSS pairs from its "signature_algorithms" extension. In any DSS pairs from its "signature_algorithms" extension. In order to
order to negotiate correctly, the server MUST check any candidate negotiate correctly, the server MUST check any candidate cipher
cipher suites against the "signature_algorithms" extension before suites against the "signature_algorithms" extension before selecting
selecting them. This is somewhat inelegant but is a compromise them. This is somewhat inelegant but is a compromise designed to
designed to minimize changes to the original cipher suite design. minimize changes to the original cipher suite design.
If no "signature_algorithms" extension is present, the server MUST If no "signature_algorithms" extension is present, the server MUST
use SHA-1 as the hash algorithm. use SHA-1 as the hash algorithm.
In addition, the digest and signature algorithms MUST be compatible In addition, the hash and signature algorithms MUST be compatible
with the key in the client's end-entity certificate. RSA keys MAY be with the key in the server's end-entity certificate. RSA keys MAY be
used with any permitted digest algorithm. used with any permitted hash algorithm, subject to restrictions in
the certificate, if any.
Because DSA signatures do not contain any secure indication of digest
algorithm, it must be unambiguous which digest algorithm is to be
used with any key. DSA keys specified with Object Identifier
1 2 840 10040 4 1 MUST only be used with SHA-1. Future revisions of
[PKIX] MAY define new object identifiers for DSA with other digest
algorithms.
The hash algorithm is denoted Hash below. Hash.length is the length Because DSA signatures do not contain any secure indication of hash
of the output of that algorithm. algorithm, there is a risk of hash substitution if multiple hashes
may be used with any key. Currently, DSS [DSS] may only be used with
SHA-1. Future revisions of DSS [DSS-3] are expected to allow other
digest algorithms, as well as guidance as to which digest algorithms
should be used with each key size. In addition, future revisions of
[PKIX] may specify mechanisms for certificates to indicate which
digest algorithms are to be used with DSA.
As additional CipherSuites are defined for TLS that include new key As additional CipherSuites are defined for TLS that include new key
exchange algorithms, the server key exchange message will be sent if exchange algorithms, the server key exchange message will be sent if
and only if the certificate type associated with the key exchange and only if the certificate type associated with the key exchange
algorithm does not provide enough information for the client to algorithm does not provide enough information for the client to
exchange a premaster secret. exchange a premaster secret.
7.4.4. Certificate Request 7.4.4. Certificate Request
When this message will be sent: When this message will be sent:
skipping to change at page 99, line ? skipping to change at page 49, line 50
As additional CipherSuites are defined for TLS that include new key As additional CipherSuites are defined for TLS that include new key
exchange algorithms, the server key exchange message will be sent if exchange algorithms, the server key exchange message will be sent if
and only if the certificate type associated with the key exchange and only if the certificate type associated with the key exchange
algorithm does not provide enough information for the client to algorithm does not provide enough information for the client to
exchange a premaster secret. exchange a premaster secret.
7.4.4. Certificate Request 7.4.4. Certificate Request
When this message will be sent: When this message will be sent:
A non-anonymous server can optionally request a certificate from A non-anonymous server can optionally request a certificate from
the client, if appropriate for the selected cipher suite. This the client, if appropriate for the selected cipher suite. This
message, if sent, will immediately follow the Server Key Exchange message, if sent, will immediately follow the Server Key Exchange
message (if it is sent; otherwise, the Server Certificate message (if it is sent; otherwise, the Server Certificate
message). message).
Structure of this message: Structure of this message:
enum {
rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
rsa_ephemeral_dh_RESERVED(5), dss_ephemeral_dh_RESERVED(6),
fortezza_dms_RESERVED(20), (255)
} ClientCertificateType;
opaque DistinguishedName<1..2^16-1>; enum {
rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
rsa_ephemeral_dh_RESERVED(5), dss_ephemeral_dh_RESERVED(6),
fortezza_dms_RESERVED(20), (255)
} ClientCertificateType;
struct { opaque DistinguishedName<1..2^16-1>;
ClientCertificateType certificate_types<1..2^8-1>;
SignatureAndHashAlgorithm struct {
supported_signature_algorithms<2^16-1>; ClientCertificateType certificate_types<1..2^8-1>;
DistinguishedName certificate_authorities<0..2^16-1>; SignatureAndHashAlgorithm
} CertificateRequest; supported_signature_algorithms<2^16-1>;
DistinguishedName certificate_authorities<0..2^16-1>;
} CertificateRequest;
certificate_types certificate_types
A list of the types of certificate types which the client may A list of the types of certificate types which the client may
offer. offer.
rsa_sign a certificate containing an RSA key
dss_sign a certificate containing a DSS key rsa_sign a certificate containing an RSA key
rsa_fixed_dh a certificate containing a static DH key. dss_sign a certificate containing a DSS key
dss_fixed_dh a certificate containing a static DH key rsa_fixed_dh a certificate containing a static DH key.
dss_fixed_dh a certificate containing a static DH key
supported_signature_algorithms supported_signature_algorithms
A list of the digest/signature algorithm pairs that the server is A list of the hash/signature algorithm pairs that the server is
able to verify, listed in descending order of preference. able to verify, listed in descending order of preference.
certificate_authorities certificate_authorities
A list of the distinguished names [X501] of acceptable A list of the distinguished names [X501] of acceptable
certificate_authorities, represented in DER-encoded format. These certificate_authorities, represented in DER-encoded format. These
distinguished names may specify a desired distinguished name for distinguished names may specify a desired distinguished name for a
a root CA or for a subordinate CA; thus, this message can be used root CA or for a subordinate CA; thus, this message can be used
both to describe known roots and a desired authorization space. both to describe known roots and a desired authorization space. If
If the certificate_authorities list is empty then the client MAY the certificate_authorities list is empty then the client MAY send
send any certificate of the appropriate ClientCertificateType, any certificate of the appropriate ClientCertificateType, unless
unless there is some external arrangement to the contrary. there is some external arrangement to the contrary.
The interaction of the certificate_types and The interaction of the certificate_types and
supported_signature_algorithms fields is somewhat complicated. supported_signature_algorithms fields is somewhat complicated.
certificate_types has been present in TLS since SSLv3, but was certificate_types has been present in TLS since SSLv3, but was
somewhat underspecified. Much of its functionality is superseded by somewhat underspecified. Much of its functionality is superseded by
supported_signature_algorithms. The following rules apply: supported_signature_algorithms. The following rules apply:
- Any certificates provided by the client MUST be signed using - Any certificates provided by the client MUST be signed using a
a digest/signature algorithm pair found in hash/signature algorithm pair found in supported_signature_types.
supported_signature_types.
- The end-entity certificate provided by the client MUST contain a - The end-entity certificate provided by the client MUST contain a
key which is compatible with certificate_types. If the key is a key which is compatible with certificate_types. If the key is a
signature key, it MUST be usable with some digest/signature signature key, it MUST be usable with some hash/signature
algorithm pair in supported_signature_types. algorithm pair in supported_signature_types.
- For historical reasons, the names of some client certificate - For historical reasons, the names of some client certificate types
types include the algorithm used to sign the certificate. For include the algorithm used to sign the certificate. For example,
example, in earlier versions of TLS, rsa_fixed_dh meant a in earlier versions of TLS, rsa_fixed_dh meant a certificate
certificate signed with RSA and containing a static DH key. In signed with RSA and containing a static DH key. In TLS 1.2, this
TLS 1.2, this functionality has been obsoleted by the functionality has been obsoleted by the signature_types field, and
signature_types field, and the certificate type no longer the certificate type no longer restricts the algorithm used to
restricts the algorithm used to sign the certificate. For sign the certificate. For example, if the server sends
example, if the server sends dss_fixed_dh certificate type and dss_fixed_dh certificate type and {dss_sha1, rsa_sha1} signature
{dss_sha1, rsa_sha1} signature types, the client MAY to reply types, the client MAY to reply with a certificate containing a
with a certificate containing a static DH key, signed with RSA- static DH key, signed with RSA-SHA1.
SHA1.
New ClientCertificateType values are assigned by IANA as described in New ClientCertificateType values are assigned by IANA as described in
Section 12. Section 12.
Note: Values listed as RESERVED may not be used. They were used in Note: Values listed as RESERVED may not be used. They were used in
SSLv3. SSLv3.
Note: It is a fatal handshake_failure alert for an anonymous server to Note: It is a fatal handshake_failure alert for an anonymous server
request client authentication. to request client authentication.
7.4.5 Server hello done 7.4.5 Server hello done
When this message will be sent: When this message will be sent:
The server hello done message is sent by the server to indicate
the end of the server hello and associated messages. After The server hello done message is sent by the server to indicate
sending this message, the server will wait for a client response. the end of the server hello and associated messages. After sending
this message, the server will wait for a client response.
Meaning of this message: Meaning of this message:
This message means that the server is done sending messages to
support the key exchange, and the client can proceed with its
phase of the key exchange.
Upon receipt of the server hello done message, the client SHOULD This message means that the server is done sending messages to
verify that the server provided a valid certificate, if required support the key exchange, and the client can proceed with its
and check that the server hello parameters are acceptable. phase of the key exchange.
Upon receipt of the server hello done message, the client SHOULD
verify that the server provided a valid certificate, if required
and check that the server hello parameters are acceptable.
Structure of this message: Structure of this message:
struct { } ServerHelloDone;
struct { } ServerHelloDone;
7.4.6. Client Certificate 7.4.6. Client Certificate
When this message will be sent: When this message will be sent:
This is the first message the client can send after receiving a
server hello done message. This message is only sent if the This is the first message the client can send after receiving a
server requests a certificate. If no suitable certificate is server hello done message. This message is only sent if the server
available, the client SHOULD send a certificate message requests a certificate. If no suitable certificate is available,
containing no certificates. That is, the certificate_list the client MUST send a certificate message containing no
structure has a length of zero. If client authentication is certificates. That is, the certificate_list structure has a length
required by the server for the handshake to continue, it may of zero. If client authentication is required by the server for
respond with a fatal handshake failure alert. Client certificates the handshake to continue, it may respond with a fatal handshake
are sent using the Certificate structure defined in Section failure alert. Client certificates are sent using the Certificate
7.4.2. structure defined in Section 7.4.2.
Meaning of this message: Meaning of this message:
This message conveys the client's certificate to the server; the
server will use it when verifying the certificate verify message
(when the client authentication is based on signing), or
calculate the premaster secret (for non-ephemeral Diffie-
Hellman). The certificate MUST be appropriate for the negotiated
cipher suite's key exchange algorithm, and any negotiated
extensions.
In particular: This message conveys the client's certificate to the server; the
server will use it when verifying the certificate verify message
(when the client authentication is based on signing), or calculate
the premaster secret (for non-ephemeral Diffie-Hellman). The
certificate MUST be appropriate for the negotiated cipher suite's
key exchange algorithm, and any negotiated extensions.
- The certificate type MUST be X.509v3, unless explicitly In particular:
negotiated otherwise (e.g. [TLSPGP]).
- The certificate's public key (and associated restrictions) - The certificate type MUST be X.509v3, unless explicitly negotiated
has to be compatible with the certificate types listed in otherwise (e.g. [TLSPGP]).
CertificateRequest:
Client Cert. Type Certificate Key Type - The certificate's public key (and associated restrictions) has to
rsa_sign RSA public key; the certificate MUST allow be compatible with the certificate types listed in
the key to be used for signing with the CertificateRequest:
signature scheme and hash algorithm that
will be employed in the certificate verify
message.
dss_sign DSA public key; the certificate MUST allow Client Cert. Type Certificate Key Type
the key to be used for signing with the
hash algorithm that will be employed in
the certificate verify message.
ecdsa_sign ECDSA-capable public key; the certificate rsa_sign RSA public key; the certificate MUST allow
MUST allow the key to be used for signing the key to be used for signing with the
with the hash algorithm that will be signature scheme and hash algorithm that
employed in the certificate verify will be employed in the certificate verify
message; the public key MUST use a message.
curve and point format supported by the
server.
rsa_fixed_dh Diffie-Hellman public key; MUST use dss_sign DSA public key; the certificate MUST allow
dss_fixed_dh the same parameters as server's key. the key to be used for signing with the
hash algorithm that will be employed in
the certificate verify message.
rsa_fixed_ecdh ECDH-capable public key; MUST use ecdsa_sign ECDSA-capable public key; the certificate
ecdsa_fixed_ecdh the same curve as server's key, and MUST allow the key to be used for signing
MUST use a point format supported by with the hash algorithm that will be
employed in the certificate verify
message; the public key MUST use a
curve and point format supported by the
server.
- If the certificate_authorities list in the certificate rsa_fixed_dh Diffie-Hellman public key; MUST use
request message was non-empty, the certificate SHOULD be dss_fixed_dh the same parameters as server's key.
issued by one of the listed CAs.
- The certificates MUST be signed using an acceptable digest/ rsa_fixed_ecdh ECDH-capable public key; MUST use
signature algorithm pair, as described in Section 7.4.4. Note ecdsa_fixed_ecdh the same curve as server's key, and
that this relaxes the constraints on certificate signing MUST use a point format supported by
algorithms found in prior versions of TLS.
- If the certificate_authorities list in the certificate request
message was non-empty, the certificate SHOULD be issued by one of
the listed CAs.
- The certificates MUST be signed using an acceptable hash/
signature algorithm pair, as described in Section 7.4.4. Note that
this relaxes the constraints on certificate signing algorithms
found in prior versions of TLS.
Note that as with the server certificate, there are certificates that Note that as with the server certificate, there are certificates that
use algorithms/algorithm combinations that cannot be currently used use algorithms/algorithm combinations that cannot be currently used
with TLS. with TLS.
7.4.7. Client Key Exchange Message 7.4.7. Client Key Exchange Message
When this message will be sent: When this message will be sent:
This message is always sent by the client. It MUST immediately follow
the client certificate message, if it is sent. Otherwise it MUST be This message is always sent by the client. It MUST immediately
the first message sent by the client after it receives the server follow the client certificate message, if it is sent. Otherwise it
hello done message. MUST be the first message sent by the client after it receives the
server hello done message.
Meaning of this message: Meaning of this message:
With this message, the premaster secret is set, either though direct With this message, the premaster secret is set, either though
transmission of the RSA-encrypted secret, or by the transmission of direct transmission of the RSA-encrypted secret, or by the
Diffie-Hellman parameters that will allow each side to agree upon the transmission of Diffie-Hellman parameters that will allow each
same premaster secret. When the key exchange method is DH_RSA or side to agree upon the same premaster secret.
DH_DSS, client certification has been requested, and the client was
able to respond with a certificate that contained a Diffie-Hellman When the client is using an ephemeral Diffie-Hellman exponent,
public key whose parameters (group and generator) matched those then this message contains the client's Diffie-Hellman public
specified by the server in its certificate, this message MUST NOT value. If the client is sending a certificate containing a static
contain any data. DH exponent (i.e., it is doing fixed_dh client authentication)
then this message MUST be sent but MUST be empty.
Structure of this message: Structure of this message:
The choice of messages depends on which key exchange method has been
selected. See Section 7.4.3 for the KeyExchangeAlgorithm definition.
struct { The choice of messages depends on which key exchange method has
select (KeyExchangeAlgorithm) { been selected. See Section 7.4.3 for the KeyExchangeAlgorithm
case rsa: EncryptedPreMasterSecret; definition.
case diffie_hellman: ClientDiffieHellmanPublic;
} exchange_keys; struct {
} ClientKeyExchange; select (KeyExchangeAlgorithm) {
case rsa: EncryptedPreMasterSecret;
case diffie_hellman: ClientDiffieHellmanPublic;
} exchange_keys;
} ClientKeyExchange;
7.4.7.1. RSA Encrypted Premaster Secret Message 7.4.7.1. RSA Encrypted Premaster Secret Message
Meaning of this message: Meaning of this message:
If RSA is being used for key agreement and authentication, the client
generates a 48-byte premaster secret, encrypts it using the public If RSA is being used for key agreement and authentication, the
key from the server's certificate and sends the result in an client generates a 48-byte premaster secret, encrypts it using the
encrypted premaster secret message. This structure is a variant of public key from the server's certificate and sends the result in
the client key exchange message and is not a message in itself. an encrypted premaster secret message. This structure is a variant
of the client key exchange message and is not a message in itself.
Structure of this message: Structure of this message:
struct {
ProtocolVersion client_version;
opaque random[46];
} PreMasterSecret;
client_version struct {
ProtocolVersion client_version;
opaque random[46];
} PreMasterSecret;
The latest (newest) version supported by the client. This is client_version
used to detect version roll-back attacks. The latest (newest) version supported by the client. This is
used to detect version roll-back attacks.
random random
46 securely-generated random bytes. 46 securely-generated random bytes.
struct { struct {
public-key-encrypted PreMasterSecret pre_master_secret; public-key-encrypted PreMasterSecret pre_master_secret;
} EncryptedPreMasterSecret; } EncryptedPreMasterSecret;
pre_master_secret
This random value is generated by the client and is used to pre_master_secret
generate the master secret, as specified in Section 8.1. This random value is generated by the client and is used to
generate the master secret, as specified in Section 8.1.
Note: The version number in the PreMasterSecret is the version Note: The version number in the PreMasterSecret is the version
offered by the client in the ClientHello.client_version, not the offered by the client in the ClientHello.client_version, not the
version negotiated for the connection. This feature is designed version negotiated for the connection. This feature is designed to
to prevent rollback attacks. Unfortunately, some old prevent rollback attacks. Unfortunately, some old implementations
implementations use the negotiated version instead and therefore use the negotiated version instead and therefore checking the version
checking the version number may lead to failure to interoperate number may lead to failure to interoperate with such incorrect client
with such incorrect client implementations. implementations.
Client implementations MUST always send the correct version Client implementations MUST always send the correct version number in
number in PreMasterSecret. If ClientHello.client_version is TLS PreMasterSecret. If ClientHello.client_version is TLS 1.1 or higher,
1.1 or higher, server implementations MUST check the version server implementations MUST check the version number as described in
number as described in the note below. If the version number is the note below. If the version number is earlier than 1.0, server
earlier than 1.0, server implementations SHOULD check the version implementations SHOULD check the version number, but MAY have a
number, but MAY have a configuration option to disable the check. configuration option to disable the check. Note that if the check
Note that if the check fails, the PreMasterSecret SHOULD be fails, the PreMasterSecret SHOULD be randomized as described below.
randomized as described below.
Note: Attacks discovered by Bleichenbacher [BLEI] and Klima et al. Note: Attacks discovered by Bleichenbacher [BLEI] and Klima et al.
[KPR03] can be used to attack a TLS server that reveals whether a [KPR03] can be used to attack a TLS server that reveals whether a
particular message, when decrypted, is properly PKCS#1 formatted, particular message, when decrypted, is properly PKCS#1 formatted,
contains a valid PreMasterSecret structure, or has the correct contains a valid PreMasterSecret structure, or has the correct
version number. version number.
The best way to avoid these vulnerabilities is to treat incorrectly The best way to avoid these vulnerabilities is to treat incorrectly
formatted messages in a manner indistinguishable from correctly formatted messages in a manner indistinguishable from correctly
formatted RSA blocks. In other words: formatted RSA blocks. In other words:
1. Generate a string R of 46 random bytes 1. Generate a string R of 46 random bytes
2. Decrypt the message M 2. Decrypt the message M
3. If the PKCS#1 padding is not correct, or the length of 3. If the PKCS#1 padding is not correct, or the length of
message M is not exactly 48 bytes: message M is not exactly 48 bytes:
premaster secret = ClientHello.client_version || R premaster secret = ClientHello.client_version || R
else If ClientHello.client_version <= TLS 1.0, and else If ClientHello.client_version <= TLS 1.0, and
version number check is explicitly disabled: version number check is explicitly disabled:
premaster secret = M premaster secret = M
else: else:
premaster secret = ClientHello.client_version || M[2..47] premaster secret = ClientHello.client_version || M[2..47]
In any case, a TLS server MUST NOT generate an alert if processing an In any case, a TLS server MUST NOT generate an alert if processing an
RSA-encrypted premaster secret message fails, or the version number RSA-encrypted premaster secret message fails, or the version number
is not as expected. Instead, it MUST continue the handshake with a is not as expected. Instead, it MUST continue the handshake with a
randomly generated premaster secret. It may be useful to log the randomly generated premaster secret. It may be useful to log the
real cause of failure for troubleshooting purposes; however, care real cause of failure for troubleshooting purposes; however, care
must be taken to avoid leaking the information to an attacker must be taken to avoid leaking the information to an attacker
(though, e.g., timing, log files, or other channels.) (though, e.g., timing, log files, or other channels.)
The RSAES-OAEP encryption scheme defined in [PKCS1] is more secure The RSAES-OAEP encryption scheme defined in [PKCS1] is more secure
against the Bleichenbacher attack. However, for maximal compatibility against the Bleichenbacher attack. However, for maximal compatibility
with earlier versions of TLS, this specification uses the RSAES- with earlier versions of TLS, this specification uses the RSAES-
PKCS1-v1_5 scheme. No variants of the Bleichenbacher attack are known PKCS1-v1_5 scheme. No variants of the Bleichenbacher attack are known
to exist provided that the above recommendations are followed. to exist provided that the above recommendations are followed.
Implementation Note: Public-key-encrypted data is represented as an Implementation Note: Public-key-encrypted data is represented as an
opaque vector <0..2^16-1> (see Section 4.7). Thus, the RSA-encrypted opaque vector <0..2^16-1> (see Section 4.7). Thus, the RSA-encrypted
PreMasterSecret in a ClientKeyExchange is preceded by two length PreMasterSecret in a ClientKeyExchange is preceded by two length
bytes. These bytes are redundant in the case of RSA because the bytes. These bytes are redundant in the case of RSA because the
EncryptedPreMasterSecret is the only data in the ClientKeyExchange EncryptedPreMasterSecret is the only data in the ClientKeyExchange
and its length can therefore be unambiguously determined. The SSLv3 and its length can therefore be unambiguously determined. The SSLv3
specification was not clear about the encoding of public-key- specification was not clear about the encoding of public-key-
encrypted data, and therefore many SSLv3 implementations do not encrypted data, and therefore many SSLv3 implementations do not
include the the length bytes, encoding the RSA encrypted data include the the length bytes, encoding the RSA encrypted data
directly in the ClientKeyExchange message. directly in the ClientKeyExchange message.
This specification requires correct encoding of the This specification requires correct encoding of the
EncryptedPreMasterSecret complete with length bytes. The resulting EncryptedPreMasterSecret complete with length bytes. The resulting
PDU is incompatible with many SSLv3 implementations. Implementors PDU is incompatible with many SSLv3 implementations. Implementors
upgrading from SSLv3 MUST modify their implementations to generate upgrading from SSLv3 MUST modify their implementations to generate
and accept the correct encoding. Implementors who wish to be and accept the correct encoding. Implementors who wish to be
compatible with both SSLv3 and TLS should make their implementation's compatible with both SSLv3 and TLS should make their implementation's
behavior dependent on the protocol version. behavior dependent on the protocol version.
Implementation Note: It is now known that remote timing-based attacks Implementation Note: It is now known that remote timing-based attacks
on TLS are possible, at least when the client and server are on the on TLS are possible, at least when the client and server are on the
same LAN. Accordingly, implementations that use static RSA keys MUST same LAN. Accordingly, implementations that use static RSA keys MUST
use RSA blinding or some other anti-timing technique, as described in use RSA blinding or some other anti-timing technique, as described in
[TIMING]. [TIMING].
7.4.7.2. Client Diffie-Hellman Public Value 7.4.7.2. Client Diffie-Hellman Public Value
Meaning of this message: Meaning of this message:
This structure conveys the client's Diffie-Hellman public value
(Yc) if it was not already included in the client's certificate. This structure conveys the client's Diffie-Hellman public value
The encoding used for Yc is determined by the enumerated (Yc) if it was not already included in the client's certificate.
PublicValueEncoding. This structure is a variant of the client The encoding used for Yc is determined by the enumerated
key exchange message, and not a message in itself. PublicValueEncoding. This structure is a variant of the client key
exchange message, and not a message in itself.
Structure of this message: Structure of this message:
enum { implicit, explicit } PublicValueEncoding;
implicit
If the client certificate already contains a suitable Diffie-
Hellman key, then Yc is implicit and does not need to be sent
again. In this case, the client key exchange message will be
sent, but it MUST be empty.
explicit enum { implicit, explicit } PublicValueEncoding;
Yc needs to be sent.
struct { implicit
select (PublicValueEncoding) { If the client has sent a certificate which contains a suitable
case implicit: struct { }; Diffie-Hellman key (for fixed_dh client authentication) then Yc
case explicit: opaque dh_Yc<1..2^16-1>; is implicit and does not need to be sent again. In this case,
} dh_public; the client key exchange message will be sent, but it MUST be
} ClientDiffieHellmanPublic; empty.
dh_Yc explicit
The client's Diffie-Hellman public value (Yc). Yc needs to be sent.
struct {
select (PublicValueEncoding) {
case implicit: struct { };
case explicit: opaque dh_Yc<1..2^16-1>;
} dh_public;
} ClientDiffieHellmanPublic;
dh_Yc
The client's Diffie-Hellman public value (Yc).
7.4.8. Certificate verify 7.4.8. Certificate verify
When this message will be sent: When this message will be sent:
This message is used to provide explicit verification of a client
certificate. This message is only sent following a client This message is used to provide explicit verification of a client
certificate that has signing capability (i.e. all certificates certificate. This message is only sent following a client
except those containing fixed Diffie-Hellman parameters). When certificate that has signing capability (i.e. all certificates
sent, it MUST immediately follow the client key exchange message. except those containing fixed Diffie-Hellman parameters). When
sent, it MUST immediately follow the client key exchange message.
Structure of this message: Structure of this message:
struct {
Signature signature;
} CertificateVerify;
The Signature type is defined in 7.4.3. struct {
Signature signature;
} CertificateVerify;
The hash algorithm is denoted Hash below. The Signature type is defined in 7.4.3.
CertificateVerify.signature.hash = Hash(handshake_messages); The hash algorithm is denoted Hash below.
The digest and signature algorithms MUST be one of those present CertificateVerify.signature.hash = Hash(handshake_messages);
in the supported_signature_algorithms field of the
CertificateRequest message. In addition, the digest and signature
algorithms MUST be compatible with the key in the client's end-
entity certificate. RSA keys MAY be used with any permitted
digest algorithm.
Because DSA signatures do not contain any secure indication of The hash and signature algorithms MUST be one of those present in the
digest algorithm, it must be unambiguous which digest algorithm supported_signature_algorithms field of the CertificateRequest
is to be used with any key. DSA keys specified with Object message. In addition, the hash and signature algorithms MUST be
Identifier 1 2 840 10040 4 1 MUST only be used with SHA-1. compatible with the key in the client's end-entity certificate. RSA
Future revisions of [PKIX] MAY define new object identifiers for keys MAY be used with any permitted hash algorith, subject to
DSA with other digest algorithms. restrictions in the certificate, if any.
Because DSA signatures do not contain any secure indication of hash
algorithm, there is a risk of hash substitution if multiple hashes
may be used with any key. Currently, DSS [DSS] may only be used with
SHA-1. Future revisions of DSS [DSS-3] are expected to allow other
digest algorithms, as well as guidance as to which digest algorithms
should be used with each key size. In addition, future revisions of
[PKIX] may specify mechanisms for certificates to indicate which
digest algorithms are to be used with DSA.
Here handshake_messages refers to all handshake messages sent or Here handshake_messages refers to all handshake messages sent or
received starting at client hello up to but not including this received starting at client hello up to but not including this
message, including the type and length fields of the handshake message, including the type and length fields of the handshake
messages. This is the concatenation of all the Handshake structures messages. This is the concatenation of all the Handshake structures
as defined in 7.4 exchanged thus far. as defined in 7.4 exchanged thus far.
7.4.9. Finished 7.4.9. Finished
When this message will be sent: When this message will be sent:
A finished message is always sent immediately after a change
cipher spec message to verify that the key exchange and A finished message is always sent immediately after a change
authentication processes were successful. It is essential that a cipher spec message to verify that the key exchange and
change cipher spec message be received between the other authentication processes were successful. It is essential that a
handshake messages and the Finished message. change cipher spec message be received between the other handshake
messages and the Finished message.
Meaning of this message: Meaning of this message:
The finished message is the first protected with the just-
negotiated algorithms, keys, and secrets. Recipients of finished
messages MUST verify that the contents are correct. Once a side
has sent its Finished message and received and validated the
Finished message from its peer, it may begin to send and receive
application data over the connection.
struct { The finished message is the first protected with the just-
opaque verify_data[SecurityParameters.verify_data_length]; negotiated algorithms, keys, and secrets. Recipients of finished
} Finished; messages MUST verify that the contents are correct. Once a side
has sent its Finished message and received and validated the
Finished message from its peer, it may begin to send and receive
application data over the connection.
verify_data Structure of this message:
PRF(master_secret, finished_label, Hash(handshake_messages))
[0..SecurityParameters.verify_data_length-1];
finished_label struct {
For Finished messages sent by the client, the string "client opaque verify_data[verify_data_length];
finished". For Finished messages sent by the server, the } Finished;
string "server finished".
Hash denotes the negotiated hash used for the PRF. If a new verify_data
PRF is defined, then this hash MUST be specified. PRF(master_secret, finished_label, Hash(handshake_messages))
[0..verify_data_length-1];
In previous versions of TLS, the verify_data was always 12 finished_label
octets long. In the current version of TLS, it depends on the For Finished messages sent by the client, the string "client
cipher suite. Any cipher suite which does not explicitly finished". For Finished messages sent by the server, the string
specify SecurityParameters.verify_data_length has a "server finished".
SecurityParameters.verify_data_length equal to 12. This
includes all existing cipher suites. Note that this
representation has the same encoding as with previous
versions. Future cipher suites MAY specify other lengths but
such length MUST be at least 12 bytes.
handshake_messages Hash denotes a Hash of the handshake messages. For the PRF defined
All of the data from all messages in this handshake (not in Section 5, the Hash MUST be the Hash used as the basis for the
including any HelloRequest messages) up to but not including PRF. Any cipher suite which defines a different PRF MUST also
this message. This is only data visible at the handshake define the Hash to use in the Finished computation.
layer and does not include record layer headers. This is the
concatenation of all the Handshake structures as defined in In previous versions of TLS, the verify_data was always 12 octets
7.4, exchanged thus far. long. In the current version of TLS, it depends on the cipher
suite. Any cipher suite which does not explicitly specify
verify_data_length has a verify_data_length equal to 12. This
includes all existing cipher suites. Note that this
representation has the same encoding as with previous versions.
Future cipher suites MAY specify other lengths but such length
MUST be at least 12 bytes.
handshake_messages
All of the data from all messages in this handshake (not
including any HelloRequest messages) up to but not including
this message. This is only data visible at the handshake layer
and does not include record layer headers. This is the
concatenation of all the Handshake structures as defined in
7.4, exchanged thus far.
It is a fatal error if a finished message is not preceded by a change It is a fatal error if a finished message is not preceded by a change
cipher spec message at the appropriate point in the handshake. cipher spec message at the appropriate point in the handshake.
The value handshake_messages includes all handshake messages starting The value handshake_messages includes all handshake messages starting
at client hello up to, but not including, this finished message. This at client hello up to, but not including, this finished message. This
may be different from handshake_messages in Section 7.4.8 because it may be different from handshake_messages in Section 7.4.8 because it
would include the certificate verify message (if sent). Also, the would include the certificate verify message (if sent). Also, the
handshake_messages for the finished message sent by the client will handshake_messages for the finished message sent by the client will
be different from that for the finished message sent by the server, be different from that for the finished message sent by the server,
because the one that is sent second will include the prior one. because the one that is sent second will include the prior one.
Note: Change cipher spec messages, alerts, and any other record types Note: Change cipher spec messages, alerts, and any other record types
are not handshake messages and are not included in the hash are not handshake messages and are not included in the hash
computations. Also, Hello Request messages are omitted from computations. Also, Hello Request messages are omitted from handshake
handshake hashes. hashes.
8. Cryptographic Computations 8. Cryptographic Computations
In order to begin connection protection, the TLS Record Protocol In order to begin connection protection, the TLS Record Protocol
requires specification of a suite of algorithms, a master secret, and requires specification of a suite of algorithms, a master secret, and
the client and server random values. The authentication, encryption, the client and server random values. The authentication, encryption,
and MAC algorithms are determined by the cipher_suite selected by the and MAC algorithms are determined by the cipher_suite selected by the
server and revealed in the server hello message. The compression server and revealed in the server hello message. The compression
algorithm is negotiated in the hello messages, and the random values algorithm is negotiated in the hello messages, and the random values
are exchanged in the hello messages. All that remains is to calculate are exchanged in the hello messages. All that remains is to calculate
the master secret. the master secret.
8.1. Computing the Master Secret 8.1. Computing the Master Secret
For all key exchange methods, the same algorithm is used to convert For all key exchange methods, the same algorithm is used to convert
the pre_master_secret into the master_secret. The pre_master_secret the pre_master_secret into the master_secret. The pre_master_secret
should be deleted from memory once the master_secret has been should be deleted from memory once the master_secret has been
computed. computed.
master_secret = PRF(pre_master_secret, "master secret", master_secret = PRF(pre_master_secret, "master secret",
ClientHello.random + ServerHello.random) ClientHello.random + ServerHello.random)
[0..47]; [0..47];
The master secret is always exactly 48 bytes in length. The length of The master secret is always exactly 48 bytes in length. The length of
the premaster secret will vary depending on key exchange method. the premaster secret will vary depending on key exchange method.
8.1.1. RSA 8.1.1. RSA
When RSA is used for server authentication and key exchange, a When RSA is used for server authentication and key exchange, a
48-byte pre_master_secret is generated by the client, encrypted under 48-byte pre_master_secret is generated by the client, encrypted under
the server's public key, and sent to the server. The server uses its the server's public key, and sent to the server. The server uses its
skipping to change at page 99, line ? skipping to change at page 60, line 36
above. above.
8.1.2. Diffie-Hellman 8.1.2. Diffie-Hellman
A conventional Diffie-Hellman computation is performed. The A conventional Diffie-Hellman computation is performed. The
negotiated key (Z) is used as the pre_master_secret, and is converted negotiated key (Z) is used as the pre_master_secret, and is converted
into the master_secret, as specified above. Leading bytes of Z that into the master_secret, as specified above. Leading bytes of Z that
contain all zero bits are stripped before it is used as the contain all zero bits are stripped before it is used as the
pre_master_secret. pre_master_secret.
Note: Diffie-Hellman parameters are specified by the server and may Note: Diffie-Hellman parameters are specified by the server and may
be either ephemeral or contained within the server's certificate. be either ephemeral or contained within the server's certificate.
9. Mandatory Cipher Suites 9. Mandatory Cipher Suites
In the absence of an application profile standard specifying In the absence of an application profile standard specifying
otherwise, a TLS compliant application MUST implement the cipher otherwise, a TLS compliant application MUST implement the cipher
suite TLS_RSA_WITH_AES_128_CBC_SHA. suite TLS_RSA_WITH_AES_128_CBC_SHA.
10. Application Data Protocol 10. Application Data Protocol
Application data messages are carried by the Record Layer and are Application data messages are carried by the Record Layer and are
skipping to change at page 99, line ? skipping to change at page 61, line 4
suite TLS_RSA_WITH_AES_128_CBC_SHA. suite TLS_RSA_WITH_AES_128_CBC_SHA.
10. Application Data Protocol 10. Application Data Protocol
Application data messages are carried by the Record Layer and are Application data messages are carried by the Record Layer and are
fragmented, compressed, and encrypted based on the current connection fragmented, compressed, and encrypted based on the current connection
state. The messages are treated as transparent data to the record state. The messages are treated as transparent data to the record
layer. layer.
11. Security Considerations 11. Security Considerations
Security issues are discussed throughout this memo, especially in Security issues are discussed throughout this memo, especially in
Appendices D, E, and F. Appendices D, E, and F.
12. IANA Considerations 12. IANA Considerations
This document uses several registries that were originally created in This document uses several registries that were originally created in
[TLS1.1]. IANA is requested to update (has updated) these to [TLS1.1]. IANA is requested to update (has updated) these to
reference this document. The registries and their allocation policies reference this document. The registries and their allocation policies
(unchanged from [TLS1.1]) are listed below. (unchanged from [TLS1.1]) are listed below.
- TLS ClientCertificateType Identifiers Registry: Future - TLS ClientCertificateType Identifiers Registry: Future values in
values in the range 0-63 (decimal) inclusive are assigned via the range 0-63 (decimal) inclusive are assigned via Standards
Standards Action [RFC2434]. Values in the range 64-223 Action [RFC2434]. Values in the range 64-223 (decimal) inclusive
(decimal) inclusive are assigned Specification Required are assigned Specification Required [RFC2434]. Values from 224-255
[RFC2434]. Values from 224-255 (decimal) inclusive are (decimal) inclusive are reserved for Private Use [RFC2434].
reserved for Private Use [RFC2434].
- TLS Cipher Suite Registry: Future values with the first byte - TLS Cipher Suite Registry: Future values with the first byte in
in the range 0-191 (decimal) inclusive are assigned via the range 0-191 (decimal) inclusive are assigned via Standards
Standards Action [RFC2434]. Values with the first byte in Action [RFC2434]. Values with the first byte in the range 192-254
the range 192-254 (decimal) are assigned via Specification (decimal) are assigned via Specification Required [RFC2434].
Required [RFC2434]. Values with the first byte 255 (decimal) Values with the first byte 255 (decimal) are reserved for Private
are reserved for Private Use [RFC2434]. Use [RFC2434].
- TLS ContentType Registry: Future values are allocated via - TLS ContentType Registry: Future values are allocated via
Standards Action [RFC2434]. Standards Action [RFC2434].
- TLS Alert Registry: Future values are allocated via - TLS Alert Registry: Future values are allocated via Standards
Standards Action [RFC2434]. Action [RFC2434].
- TLS HandshakeType Registry: Future values are allocated via - TLS HandshakeType Registry: Future values are allocated via
Standards Action [RFC2434]. Standards Action [RFC2434].
This document also uses a registry originally created in [RFC4366]. This document also uses a registry originally created in [RFC4366].
IANA is requested to update (has updated) it to reference this IANA is requested to update (has updated) it to reference this
document. The registry and its allocation policy (unchanged from document. The registry and its allocation policy (unchanged from
[RFC4366]) is listed below:. [RFC4366]) is listed below:
- TLS ExtensionType Registry: Future values are allocated - TLS ExtensionType Registry: Future values are allocated via IETF
via IETF Consensus [RFC2434] Consensus [RFC2434]
In addition, this document defines one new registry to be maintained In addition, this document defines two new registries to be
by IANA: maintained by IANA:
- TLS SignatureAlgorithm Registry: The registry will be initially - TLS SignatureAlgorithm Registry: The registry will be initially
populated with the values described in Section 7.4.1.4.1. populated with the values described in Section 7.4.1.4.1. Future
Future values in the range 0-63 (decimal) inclusive are values in the range 0-63 (decimal) inclusive are assigned via
assigned via Standards Action [RFC2434]. Values in the Standards Action [RFC2434]. Values in the range 64-223 (decimal)
range 64-223 (decimal) inclusive are assigned via inclusive are assigned via Specification Required [RFC2434].
Specification Required [RFC2434]. Values from 224-255
(decimal) inclusive are reserved for Private Use [RFC2434].
- TLS HashAlgorithm Registry: The registry will be initially Values from 224-255 (decimal) inclusive are reserved for Private
populated with the values described in Section 7.4.1.4.1. Use [RFC2434].
Future values in the range 0-63 (decimal) inclusive are - TLS HashAlgorithm Registry: The registry will be initially
assigned via Standards Action [RFC2434]. Values in the populated with the values described in Section 7.4.1.4.1. Future
range 64-223 (decimal) inclusive are assigned via values in the range 0-63 (decimal) inclusive are assigned via
Specification Required [RFC2434]. Values from 224-255 Standards Action [RFC2434]. Values in the range 64-223 (decimal)
(decimal) inclusive are reserved for Private Use [RFC2434]. inclusive are assigned via Specification Required [RFC2434].
Values from 224-255 (decimal) inclusive are reserved for Private
Use [RFC2434].
This document defines one new TLS extension, cert_hash_type, which is This document defines one new TLS extension, signature_algorithms,
to be (has been) allocated value TBD-BY-IANA in the TLS ExtensionType which is to be (has been) allocated value TBD-BY-IANA in the TLS
registry. ExtensionType registry.
This document also uses the TLS Compression Method Identifiers This document also uses the TLS Compression Method Identifiers
Registry, defined in [RFC3749]. IANA is requested to allocate value Registry, defined in [RFC3749]. IANA is requested to allocate value
0 for the "null" compression method. 0 for the "null" compression method.
Appendix A. Protocol Constant Values Appendix A. Protocol Constant Values
This section describes protocol types and constants. This section describes protocol types and constants.
A.1. Record Layer A.1. Record Layer
struct { struct {
uint8 major, minor; uint8 major, minor;
} ProtocolVersion; } ProtocolVersion;
ProtocolVersion version = { 3, 3 }; /* TLS v1.2*/
enum { ProtocolVersion version = { 3, 3 }; /* TLS v1.2*/
change_cipher_spec(20), alert(21), handshake(22),
application_data(23), (255)
} ContentType;
struct { enum {
ContentType type; change_cipher_spec(20), alert(21), handshake(22),
ProtocolVersion version; application_data(23), (255)
uint16 length; } ContentType;
opaque fragment[TLSPlaintext.length];
} TLSPlaintext;
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
opaque fragment[TLSCompressed.length]; opaque fragment[TLSPlaintext.length];
} TLSCompressed; } TLSPlaintext;
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
select (SecurityParameters.cipher_type) { opaque fragment[TLSCompressed.length];
case stream: GenericStreamCipher; } TLSCompressed;
case block: GenericBlockCipher;
case aead: GenericAEADCipher;
} fragment;
} TLSCiphertext;
stream-ciphered struct { struct {
opaque content[TLSCompressed.length]; ContentType type;
opaque MAC[SecurityParameters.mac_length]; ProtocolVersion version;
} GenericStreamCipher; uint16 length;
select (SecurityParameters.cipher_type) {
case stream: GenericStreamCipher;
case block: GenericBlockCipher;
case aead: GenericAEADCipher;
} fragment;
} TLSCiphertext;
struct { stream-ciphered struct {
opaque IV[SecurityParameters.record_iv_length]; opaque content[TLSCompressed.length];
block-ciphered struct { opaque MAC[SecurityParameters.mac_length];
opaque content[TLSCompressed.length]; } GenericStreamCipher;
opaque MAC[SecurityParameters.mac_length]; struct {
uint8 padding[GenericBlockCipher.padding_length]; opaque IV[SecurityParameters.record_iv_length];
uint8 padding_length; block-ciphered struct {
}; opaque content[TLSCompressed.length];
} GenericBlockCipher; opaque MAC[SecurityParameters.mac_length];
uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length;
};
} GenericBlockCipher;
aead-ciphered struct { aead-ciphered struct {
opaque IV[SecurityParameters.record_iv_length]; opaque IV[SecurityParameters.record_iv_length];
opaque aead_output[AEADEncrypted.length]; opaque aead_output[AEADEncrypted.length];
} GenericAEADCipher; } GenericAEADCipher;
A.2. Change Cipher Specs Message A.2. Change Cipher Specs Message
struct { struct {
enum { change_cipher_spec(1), (255) } type; enum { change_cipher_spec(1), (255) } type;
} ChangeCipherSpec; } ChangeCipherSpec;
A.3. Alert Messages A.3. Alert Messages
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
unexpected_message(10), unexpected_message(10),
bad_record_mac(20), bad_record_mac(20),
decryption_failed_RESERVED(21), decryption_failed_RESERVED(21),
record_overflow(22), record_overflow(22),
decompression_failure(30), decompression_failure(30),
handshake_failure(40), handshake_failure(40),
no_certificate_RESERVED(41), no_certificate_RESERVED(41),
bad_certificate(42), bad_certificate(42),
unsupported_certificate(43), unsupported_certificate(43),
certificate_revoked(44), certificate_revoked(44),
certificate_expired(45), certificate_expired(45),
certificate_unknown(46), certificate_unknown(46),
illegal_parameter(47), illegal_parameter(47),
unknown_ca(48), unknown_ca(48),
access_denied(49), access_denied(49),
decode_error(50), decode_error(50),
decrypt_error(51), decrypt_error(51),
export_restriction_RESERVED(60), export_restriction_RESERVED(60),
protocol_version(70), protocol_version(70),
insufficient_security(71), insufficient_security(71),
internal_error(80), internal_error(80),
user_canceled(90), user_canceled(90),
no_renegotiation(100), no_renegotiation(100),
unsupported_extension(110), /* new */ unsupported_extension(110), /* new */
(255) (255)
} AlertDescription; } AlertDescription;
struct {
AlertLevel level;
AlertDescription description;
} Alert;
struct {
AlertLevel level;
AlertDescription description;
} Alert;
A.4. Handshake Protocol A.4. Handshake Protocol
enum { enum {
hello_request(0), client_hello(1), server_hello(2), hello_request(0), client_hello(1), server_hello(2),
certificate(11), server_key_exchange (12), certificate(11), server_key_exchange (12),
certificate_request(13), server_hello_done(14), certificate_request(13), server_hello_done(14),
certificate_verify(15), client_key_exchange(16), certificate_verify(15), client_key_exchange(16),
finished(20) finished(20)
(255) (255)
} HandshakeType; } HandshakeType;
struct { struct {
HandshakeType msg_type; HandshakeType msg_type;
uint24 length; uint24 length;
select (HandshakeType) { select (HandshakeType) {
case hello_request: HelloRequest; case hello_request: HelloRequest;
case client_hello: ClientHello; case client_hello: ClientHello;
case server_hello: ServerHello; case server_hello: ServerHello;
case certificate: Certificate; case certificate: Certificate;
case server_key_exchange: ServerKeyExchange; case server_key_exchange: ServerKeyExchange;
case certificate_request: CertificateRequest; case certificate_request: CertificateRequest;
case server_hello_done: ServerHelloDone; case server_hello_done: ServerHelloDone;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case client_key_exchange: ClientKeyExchange; case client_key_exchange: ClientKeyExchange;
case finished: Finished; case finished: Finished;
} body; } body;
} Handshake; } Handshake;
A.4.1. Hello Messages A.4.1. Hello Messages
struct { } HelloRequest; struct { } HelloRequest;
struct {
uint32 gmt_unix_time;
opaque random_bytes[28];
} Random;
opaque SessionID<0..32>; struct {
uint32 gmt_unix_time;
opaque random_bytes[28];
} Random;
opaque SessionID<0..32>;
uint8 CipherSuite[2]; uint8 CipherSuite[2];
enum { null(0), (255) } CompressionMethod; enum { null(0), (255) } CompressionMethod;
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suites<2..2^16-1>; CipherSuite cipher_suites<2..2^16-2>;
CompressionMethod compression_methods<1..2^8-1>; CompressionMethod compression_methods<1..2^8-1>;
select (extensions_present) { select (extensions_present) {
case false: case false:
struct {}; struct {};
case true: case true:
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
}; };
} ClientHello; } ClientHello;
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suite; CipherSuite cipher_suite;
CompressionMethod compression_method; CompressionMethod compression_method;
select (extensions_present) { select (extensions_present) {
case false: case false:
struct {}; struct {};
case true: case true:
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
}; };
} ServerHello; } ServerHello;
struct { struct {
ExtensionType extension_type; ExtensionType extension_type;
opaque extension_data<0..2^16-1>; opaque extension_data<0..2^16-1>;
} Extension; } Extension;
enum { enum {
signature_hash_algorithms(TBD-BY-IANA), (65535) signature_algorithms(TBD-BY-IANA), (65535)
} ExtensionType; } ExtensionType;
enum{ enum{
none(0), md5(1), sha1(2), sha256(3), sha384(4), none(0), md5(1), sha1(2), sha256(3), sha384(4),
sha512(5), (255) sha512(5), (255)
} HashAlgorithm; } HashAlgorithm;
enum { anonymous(0), rsa(1), dsa(2), (255) } SignatureAlgorithm;
enum { anonymous(0), rsa(1), dsa(2), (255) } SignatureAlgorithm; struct {
HashAlgorithm hash;
SignatureAlgorithm signature;
} SignatureAndHashAlgorithm;
struct { SignatureAndHashAlgorithm
HashAlgorithm hash; supported_signature_algorithms<2..2^16-1>;
SignatureAlgorithm signature;
} SignatureAndHashAlgorithm;
SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-1>;
A.4.2. Server Authentication and Key Exchange Messages A.4.2. Server Authentication and Key Exchange Messages
opaque ASN.1Cert<2^24-1>; opaque ASN.1Cert<2^24-1>;
struct { struct {
ASN.1Cert certificate_list<0..2^24-1>; ASN.1Cert certificate_list<0..2^24-1>;
} Certificate; } Certificate;
enum { rsa, diffie_hellman } KeyExchangeAlgorithm; enum { rsa, diffie_hellman } KeyExchangeAlgorithm;
struct { struct {
opaque dh_p<1..2^16-1>; opaque dh_p<1..2^16-1>;
opaque dh_g<1..2^16-1>; opaque dh_g<1..2^16-1>;
opaque dh_Ys<1..2^16-1>; opaque dh_Ys<1..2^16-1>;
} ServerDHParams; } ServerDHParams;
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case diffie_hellman: case diffie_hellman:
ServerDHParams params; ServerDHParams params;
Signature signed_params; Signature signed_params;
} }
} ServerKeyExchange; } ServerKeyExchange;
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case diffie_hellman: case diffie_hellman:
ServerDHParams params; ServerDHParams params;
}; };
} ServerParams; } ServerParams;
struct { struct {
select (SignatureAlgorithm) { select (SignatureAlgorithm) {
case anonymous: struct { }; case anonymous: struct { };
case rsa: case rsa:
SignatureAndHashAlgorithm signature_algorithm; /*NEW*/ SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
digitally-signed struct { digitally-signed struct {
opaque hash[Hash.length]; opaque hash[Hash.length];
};
case dsa:
SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
digitally-signed struct {
opaque hash[Hash.length];
};
};
};
} Signature;
enum {
rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
rsa_ephemeral_dh_RESERVED(5), dss_ephemeral_dh_RESERVED(6),
fortezza_dms_RESERVED(20),
(255)
} ClientCertificateType;
opaque DistinguishedName<1..2^16-1>; };
case dsa:
SignatureAndHashAlgorithm signature_algorithm; /*NEW*/
digitally-signed struct {
opaque hash[Hash.length];
};
};
};
} Signature;
struct { enum {
ClientCertificateType certificate_types<1..2^8-1>; rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
DistinguishedName certificate_authorities<0..2^16-1>; rsa_ephemeral_dh_RESERVED(5), dss_ephemeral_dh_RESERVED(6),
} CertificateRequest; fortezza_dms_RESERVED(20),
(255)
} ClientCertificateType;
struct { } ServerHelloDone; opaque DistinguishedName<1..2^16-1>;
struct {
ClientCertificateType certificate_types<1..2^8-1>;
DistinguishedName certificate_authorities<0..2^16-1>;
} CertificateRequest;
struct { } ServerHelloDone;
A.4.3. Client Authentication and Key Exchange Messages A.4.3. Client Authentication and Key Exchange Messages
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case rsa: EncryptedPreMasterSecret; case rsa: EncryptedPreMasterSecret;
case diffie_hellman: ClientDiffieHellmanPublic; case diffie_hellman: ClientDiffieHellmanPublic;
} exchange_keys; } exchange_keys;
} ClientKeyExchange; } ClientKeyExchange;
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
opaque random[46]; opaque random[46];
} PreMasterSecret; } PreMasterSecret;
struct { struct {
public-key-encrypted PreMasterSecret pre_master_secret; public-key-encrypted PreMasterSecret pre_master_secret;
} EncryptedPreMasterSecret; } EncryptedPreMasterSecret;
enum { implicit, explicit } PublicValueEncoding; enum { implicit, explicit } PublicValueEncoding;
struct { struct {
select (PublicValueEncoding) { select (PublicValueEncoding) {
case implicit: struct {}; case implicit: struct {};
case explicit: opaque DH_Yc<1..2^16-1>; case explicit: opaque DH_Yc<1..2^16-1>;
} dh_public; } dh_public;
} ClientDiffieHellmanPublic; } ClientDiffieHellmanPublic;
struct { struct {
Signature signature; Signature signature;
} CertificateVerify; } CertificateVerify;
A.4.4. Handshake Finalization Message A.4.4. Handshake Finalization Message
struct {
opaque verify_data[SecurityParameters.verify_data_length]; struct {
} Finished; opaque verify_data[verify_data_length];
} Finished;
A.5. The CipherSuite A.5. The CipherSuite
The following values define the CipherSuite codes used in the client The following values define the CipherSuite codes used in the client
hello and server hello messages. hello and server hello messages.
A CipherSuite defines a cipher specification supported in TLS Version A CipherSuite defines a cipher specification supported in TLS Version
1.2. 1.2.
TLS_NULL_WITH_NULL_NULL is specified and is the initial state of a TLS_NULL_WITH_NULL_NULL is specified and is the initial state of a
TLS connection during the first handshake on that channel, but MUST TLS connection during the first handshake on that channel, but MUST
not be negotiated, as it provides no more protection than an not be negotiated, as it provides no more protection than an
unsecured connection. unsecured connection.
CipherSuite TLS_NULL_WITH_NULL_NULL = { 0x00,0x00 }; CipherSuite TLS_NULL_WITH_NULL_NULL = { 0x00,0x00 };
The following CipherSuite definitions require that the server provide The following CipherSuite definitions require that the server provide
an RSA certificate that can be used for key exchange. The server may an RSA certificate that can be used for key exchange. The server may
request either an RSA or a DSS signature-capable certificate in the request either any signature-capable certificate in the certificate
certificate request message. request message.
CipherSuite TLS_RSA_WITH_NULL_MD5 = { 0x00,0x01 }; CipherSuite TLS_RSA_WITH_NULL_MD5 = { 0x00,0x01 };
CipherSuite TLS_RSA_WITH_NULL_SHA = { 0x00,0x02 }; CipherSuite TLS_RSA_WITH_NULL_SHA = { 0x00,0x02 };
CipherSuite TLS_RSA_WITH_RC4_128_MD5 = { 0x00,0x04 }; CipherSuite TLS_RSA_WITH_RC4_128_MD5 = { 0x00,0x04 };
CipherSuite TLS_RSA_WITH_RC4_128_SHA = { 0x00,0x05 }; CipherSuite TLS_RSA_WITH_RC4_128_SHA = { 0x00,0x05 };
CipherSuite TLS_RSA_WITH_IDEA_CBC_SHA = { 0x00,0x07 }; CipherSuite TLS_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0A };
CipherSuite TLS_RSA_WITH_DES_CBC_SHA = { 0x00,0x09 }; CipherSuite TLS_RSA_WITH_AES_128_CBC_SHA = { 0x00,0x2F };
CipherSuite TLS_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0A }; CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA = { 0x00,0x35 };
CipherSuite TLS_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x2F };
CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x35 };
The following CipherSuite definitions are used for server- The following CipherSuite definitions are used for server-
authenticated (and optionally client-authenticated) Diffie-Hellman. authenticated (and optionally client-authenticated) Diffie-Hellman.
DH denotes cipher suites in which the server's certificate contains DH denotes cipher suites in which the server's certificate contains
the Diffie-Hellman parameters signed by the certificate authority the Diffie-Hellman parameters signed by the certificate authority
(CA). DHE denotes ephemeral Diffie-Hellman, where the Diffie-Hellman (CA). DHE denotes ephemeral Diffie-Hellman, where the Diffie-Hellman
parameters are signed by a DSS or RSA certificate, which has been parameters are signed by a a signature-capable certificate, which has
signed by the CA. The signing algorithm used is specified after the been signed by the CA. The signing algorithm used is specified after
DH or DHE parameter. The server can request an RSA or DSS signature- the DH or DHE parameter. The server can request any signature-capable
capable certificate from the client for client authentication or it certificate from the client for client authentication or it may
may request a Diffie-Hellman certificate. Any Diffie-Hellman request a Diffie-Hellman certificate. Any Diffie-Hellman certificate
certificate provided by the client must use the parameters (group and provided by the client must use the parameters (group and generator)
generator) described by the server. described by the server.
CipherSuite TLS_DH_DSS_WITH_DES_CBC_SHA = { 0x00,0x0C }; CipherSuite TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0D };
CipherSuite TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0D }; CipherSuite TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x10 };
CipherSuite TLS_DH_RSA_WITH_DES_CBC_SHA = { 0x00,0x0F }; CipherSuite TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x13 };
CipherSuite TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x10 }; CipherSuite TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x16 };
CipherSuite TLS_DHE_DSS_WITH_DES_CBC_SHA = { 0x00,0x12 }; CipherSuite TLS_DH_DSS_WITH_AES_128_CBC_SHA = { 0x00,0x30 };
CipherSuite TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x13 }; CipherSuite TLS_DH_RSA_WITH_AES_128_CBC_SHA = { 0x00,0x31 };
CipherSuite TLS_DHE_RSA_WITH_DES_CBC_SHA = { 0x00,0x15 }; CipherSuite TLS_DHE_DSS_WITH_AES_128_CBC_SHA = { 0x00,0x32 };
CipherSuite TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x16 }; CipherSuite TLS_DHE_RSA_WITH_AES_128_CBC_SHA = { 0x00,0x33 };
CipherSuite TLS_DH_DSS_WITH_AES_128_CBC_SHA = { 0x00, 0x30 }; CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA = { 0x00,0x36 };
CipherSuite TLS_DH_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x31 }; CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA = { 0x00,0x37 };
CipherSuite TLS_DHE_DSS_WITH_AES_128_CBC_SHA = { 0x00, 0x32 }; CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA = { 0x00,0x38 };
CipherSuite TLS_DHE_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x33 }; CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA = { 0x00,0x39 };
CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x36 };
CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x37 };
CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x38 };
CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x39 };
The following cipher suites are used for completely anonymous Diffie- The following cipher suites are used for completely anonymous Diffie-
Hellman communications in which neither party is authenticated. Note Hellman communications in which neither party is authenticated. Note
that this mode is vulnerable to man-in-the-middle attacks. Using that this mode is vulnerable to man-in-the-middle attacks. Using
this mode therefore is of limited use: These ciphersuites MUST NOT be this mode therefore is of limited use: These ciphersuites MUST NOT be
used by TLS 1.2 implementations unless the application layer has used by TLS 1.2 implementations unless the application layer has
specifically requested to allow anonymous key exchange. (Anonymous specifically requested to allow anonymous key exchange. (Anonymous
key exchange may sometimes be acceptable, for example, to support key exchange may sometimes be acceptable, for example, to support
opportunistic encryption when no set-up for authentication is in opportunistic encryption when no set-up for authentication is in
place, or when TLS is used as part of more complex security protocols place, or when TLS is used as part of more complex security protocols
that have other means to ensure authentication.) that have other means to ensure authentication.)
CipherSuite TLS_DH_anon_WITH_RC4_128_MD5 = { 0x00, 0x18 }; CipherSuite TLS_DH_anon_WITH_RC4_128_MD5 = { 0x00,0x18 };
CipherSuite TLS_DH_anon_WITH_DES_CBC_SHA = { 0x00, 0x1A }; CipherSuite TLS_DH_anon_WITH_3DES_EDE_CBC_SHA = { 0x00,0x1B };
CipherSuite TLS_DH_anon_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x1B }; CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA = { 0x00,0x34 };
CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA = { 0x00, 0x34 }; CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA = { 0x00,0x3A };
CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA = { 0x00, 0x3A };
Note that using non-anonymous key exchange without actually verifying Note that using non-anonymous key exchange without actually verifying
the key exchange is essentially equivalent to anonymous key exchange, the key exchange is essentially equivalent to anonymous key exchange,
and the same precautions apply. While non-anonymous key exchange and the same precautions apply. While non-anonymous key exchange
will generally involve a higher computational and communicational will generally involve a higher computational and communicational
cost than anonymous key exchange, it may be in the interest of cost than anonymous key exchange, it may be in the interest of
interoperability not to disable non-anonymous key exchange when the interoperability not to disable non-anonymous key exchange when the
application layer is allowing anonymous key exchange. application layer is allowing anonymous key exchange.
SSLv3, TLS 1.0, and TLS 1.1 supported DES and IDEA. DES had a 56-bit
key which is too weak for modern use. Triple-DES (3DES) has an
effective key strength of 112 bits and is still acceptable. IDEA and
is no longer in wide use. Cipher suites using RC2, DES, and IDEA are
hereby deprecated for TLS 1.2. TLS 1.2 implementations MUST NOT
negotiate these cipher suites in TLS 1.2 mode. However, for backward
compatibility they may be offered in the ClientHello for use with TLS
1.0 or SSLv3 only servers. TLS 1.2 clients MUST check that the server
did not choose one of these cipher suites during the handshake. These
ciphersuites are listed below for informational purposes and to
reserve the numbers.
CipherSuite TLS_RSA_WITH_IDEA_CBC_SHA = { 0x00,0x07 };
CipherSuite TLS_RSA_WITH_DES_CBC_SHA = { 0x00,0x09 };
CipherSuite TLS_DH_DSS_WITH_DES_CBC_SHA = { 0x00,0x0C };
CipherSuite TLS_DH_RSA_WITH_DES_CBC_SHA = { 0x00,0x0F };
CipherSuite TLS_DHE_RSA_WITH_DES_CBC_SHA = { 0x00,0x15 };
CipherSuite TLS_DHE_DSS_WITH_DES_CBC_SHA = { 0x00,0x12 };
CipherSuite TLS_DH_anon_WITH_DES_CBC_SHA = { 0x00,0x1A };
When SSLv3 and TLS 1.0 were designed, the United States restricted When SSLv3 and TLS 1.0 were designed, the United States restricted
the export of cryptographic software containing certain strong the export of cryptographic software containing certain strong
encryption algorithms. A series of cipher suites were designed to encryption algorithms. A series of cipher suites were designed to
operate at reduced key lengths in order to comply with those operate at reduced key lengths in order to comply with those
regulations. Due to advances in computer performance, these regulations. Due to advances in computer performance, these
algorithms are now unacceptably weak and export restrictions have algorithms are now unacceptably weak and export restrictions have
since been loosened. TLS 1.2 implementations MUST NOT negotiate these since been loosened. TLS 1.2 implementations MUST NOT negotiate these
cipher suites in TLS 1.2 mode. However, for backward compatibility cipher suites in TLS 1.2 mode. However, for backward compatibility
they may be offered in the ClientHello for use with TLS 1.0 or SSLv3 they may be offered in the ClientHello for use with TLS 1.0 or SSLv3
only servers. TLS 1.2 clients MUST check that the server did not only servers. TLS 1.2 clients MUST check that the server did not
choose one of these cipher suites during the handshake. These choose one of these cipher suites during the handshake. These
ciphersuites are listed below for informational purposes and to ciphersuites are listed below for informational purposes and to
reserve the numbers. reserve the numbers.
CipherSuite TLS_RSA_EXPORT_WITH_RC4_40_MD5 = { 0x00,0x03 }; CipherSuite TLS_RSA_EXPORT_WITH_RC4_40_MD5 = { 0x00,0x03 };
CipherSuite TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 = { 0x00,0x06 }; CipherSuite TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 = { 0x00,0x06 };
CipherSuite TLS_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x08 }; CipherSuite TLS_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x08 };
CipherSuite TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0B }; CipherSuite TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0B };
CipherSuite TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0E }; CipherSuite TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0E };
CipherSuite TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x11 }; CipherSuite TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x11 };
CipherSuite TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x14 }; CipherSuite TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x14 };
CipherSuite TLS_DH_anon_EXPORT_WITH_RC4_40_MD5 = { 0x00,0x17 }; CipherSuite TLS_DH_anon_EXPORT_WITH_RC4_40_MD5 = { 0x00,0x17 };
CipherSuite TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x19 }; CipherSuite TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x19 };
New cipher suite values are assigned by IANA as described in Section New cipher suite values are assigned by IANA as described in Section
12. 12.
Note: The cipher suite values { 0x00, 0x1C } and { 0x00, 0x1D } are Note: The cipher suite values { 0x00, 0x1C } and { 0x00, 0x1D } are
reserved to avoid collision with Fortezza-based cipher suites in SSL reserved to avoid collision with Fortezza-based cipher suites in SSL
3. 3.
A.6. The Security Parameters A.6. The Security Parameters
These security parameters are determined by the TLS Handshake These security parameters are determined by the TLS Handshake
Protocol and provided as parameters to the TLS Record Layer in order Protocol and provided as parameters to the TLS Record Layer in order
to initialize a connection state. SecurityParameters includes: to initialize a connection state. SecurityParameters includes:
enum { null(0), (255) } CompressionMethod; enum { null(0), (255) } CompressionMethod;
enum { server, client } ConnectionEnd; enum { server, client } ConnectionEnd;
enum { null, rc4, rc2, des, 3des, des40, aes, idea } enum { tls_prf_sha256 } PRFAlgorithm;
BulkCipherAlgorithm;
enum { stream, block, aead } CipherType; enum { null, rc4, 3des, aes }
BulkCipherAlgorithm;
enum { null, hmac_md5, hmac_sha, hmac_sha256, hmac_sha384, enum { stream, block, aead } CipherType;
hmac_sha512} MACAlgorithm;
enum { null, hmac_md5, hmac_sha, hmac_sha256, hmac_sha384,
hmac_sha512} MACAlgorithm;
/* The algorithms specified in CompressionMethod, /* The algorithms specified in CompressionMethod,
BulkCipherAlgorithm, and MACAlgorithm may be added to. */ BulkCipherAlgorithm, and MACAlgorithm may be added to. */
struct { struct {
ConnectionEnd entity; ConnectionEnd entity;
BulkCipherAlgorithm bulk_cipher_algorithm; PRFAlgorithm prf_algorithm;
CipherType cipher_type; BulkCipherAlgorithm bulk_cipher_algorithm;
uint8 enc_key_length; CipherType cipher_type;
uint8 block_length; uint8 enc_key_length;
uint8 fixed_iv_length; uint8 block_length;
uint8 record_iv_length; uint8 fixed_iv_length;
MACAlgorithm mac_algorithm; uint8 record_iv_length;
uint8 mac_length; MACAlgorithm mac_algorithm;
uint8 mac_key_length; uint8 mac_length;
uint8 verify_data_length; uint8 mac_key_length;
CompressionMethod compression_algorithm; CompressionMethod compression_algorithm;
opaque master_secret[48]; opaque master_secret[48];
opaque client_random[32]; opaque client_random[32];
opaque server_random[32]; opaque server_random[32];
} SecurityParameters; } SecurityParameters;
Appendix B. Glossary Appendix B. Glossary
Advanced Encryption Standard (AES) Advanced Encryption Standard (AES)
AES is a widely used symmetric encryption algorithm. AES is a AES is a widely used symmetric encryption algorithm. AES is a
block cipher with a 128, 192, or 256 bit keys and a 16 byte block block cipher with a 128, 192, or 256 bit keys and a 16 byte block
size. [AES] TLS currently only supports the 128 and 256 bit key size. [AES] TLS currently only supports the 128 and 256 bit key
sizes. sizes.
application protocol application protocol
An application protocol is a protocol that normally layers An application protocol is a protocol that normally layers
directly on top of the transport layer (e.g., TCP/IP). Examples directly on top of the transport layer (e.g., TCP/IP). Examples
include HTTP, TELNET, FTP, and SMTP. include HTTP, TELNET, FTP, and SMTP.
asymmetric cipher asymmetric cipher
See public key cryptography. See public key cryptography.
authenticated encryption with additional data (AEAD) authenticated encryption with additional data (AEAD)
A symmetric encryption algorithm that simultaneously provides A symmetric encryption algorithm that simultaneously provides
confidentiality and message integrity. confidentiality and message integrity.
authentication authentication
Authentication is the ability of one entity to determine the Authentication is the ability of one entity to determine the
identity of another entity. identity of another entity.
block cipher block cipher
A block cipher is an algorithm that operates on plaintext in A block cipher is an algorithm that operates on plaintext in
groups of bits, called blocks. 64 bits is a common block size. groups of bits, called blocks. 64 bits is a common block size.
bulk cipher bulk cipher
A symmetric encryption algorithm used to encrypt large quantities A symmetric encryption algorithm used to encrypt large quantities
of data. of data.
cipher block chaining (CBC) cipher block chaining (CBC)
CBC is a mode in which every plaintext block encrypted with a CBC is a mode in which every plaintext block encrypted with a
block cipher is first exclusive-ORed with the previous ciphertext block cipher is first exclusive-ORed with the previous ciphertext
block (or, in the case of the first block, with the block (or, in the case of the first block, with the initialization
initialization vector). For decryption, every block is first vector). For decryption, every block is first decrypted, then
decrypted, then exclusive-ORed with the previous ciphertext block exclusive-ORed with the previous ciphertext block (or IV).
(or IV).
certificate certificate
As part of the X.509 protocol (a.k.a. ISO Authentication As part of the X.509 protocol (a.k.a. ISO Authentication
framework), certificates are assigned by a trusted Certificate framework), certificates are assigned by a trusted Certificate
Authority and provide a strong binding between a party's identity Authority and provide a strong binding between a party's identity
or some other attributes and its public key. or some other attributes and its public key.
client client
The application entity that initiates a TLS connection to a The application entity that initiates a TLS connection to a
server. This may or may not imply that the client initiated the server. This may or may not imply that the client initiated the
underlying transport connection. The primary operational underlying transport connection. The primary operational
difference between the server and client is that the server is difference between the server and client is that the server is
generally authenticated, while the client is only optionally generally authenticated, while the client is only optionally
authenticated. authenticated.
client write key client write key
The key used to encrypt data written by the client. The key used to encrypt data written by the client.
client write MAC secret client write MAC key
The secret data used to authenticate data written by the client. The secret data used to authenticate data written by the client.
connection connection
A connection is a transport (in the OSI layering model A connection is a transport (in the OSI layering model definition)
definition) that provides a suitable type of service. For TLS, that provides a suitable type of service. For TLS, such
such connections are peer-to-peer relationships. The connections connections are peer-to-peer relationships. The connections are
are transient. Every connection is associated with one session. transient. Every connection is associated with one session.
Data Encryption Standard Data Encryption Standard
DES is a very widely used symmetric encryption algorithm. DES is DES is a very widely used symmetric encryption algorithm. DES is a
a block cipher with a 56 bit key and an 8 byte block size. Note block cipher with a 56 bit key and an 8 byte block size. Note that
that in TLS, for key generation purposes, DES is treated as in TLS, for key generation purposes, DES is treated as having an 8
having an 8 byte key length (64 bits), but it still only provides byte key length (64 bits), but it still only provides 56 bits of
56 bits of protection. (The low bit of each key byte is presumed protection. (The low bit of each key byte is presumed to be set to
to be set to produce odd parity in that key byte.) DES can also produce odd parity in that key byte.) DES can also be operated in
be operated in a mode where three independent keys and three a mode where three independent keys and three encryptions are used
encryptions are used for each block of data; this uses 168 bits for each block of data; this uses 168 bits of key (24 bytes in the
of key (24 bytes in the TLS key generation method) and provides TLS key generation method) and provides the equivalent of 112 bits
the equivalent of 112 bits of security. [DES], [3DES] of security. [DES], [3DES]
Digital Signature Standard (DSS) Digital Signature Standard (DSS)
A standard for digital signing, including the Digital Signing A standard for digital signing, including the Digital Signing
Algorithm, approved by the National Institute of Standards and Algorithm, approved by the National Institute of Standards and
Technology, defined in NIST FIPS PUB 186, "Digital Signature Technology, defined in NIST FIPS PUB 186, "Digital Signature
Standard", published May, 1994 by the U.S. Dept. of Commerce. Standard", published May, 1994 by the U.S. Dept. of Commerce.
[DSS] [DSS]
digital signatures digital signatures
Digital signatures utilize public key cryptography and one-way Digital signatures utilize public key cryptography and one-way
hash functions to produce a signature of the data that can be hash functions to produce a signature of the data that can be
authenticated, and is difficult to forge or repudiate. authenticated, and is difficult to forge or repudiate.
handshake handshake
An initial negotiation between client and server that establishes An initial negotiation between client and server that establishes
the parameters of their transactions. the parameters of their transactions.
Initialization Vector (IV) Initialization Vector (IV)
When a block cipher is used in CBC mode, the initialization When a block cipher is used in CBC mode, the initialization vector
vector is exclusive-ORed with the first plaintext block prior to is exclusive-ORed with the first plaintext block prior to
encryption. encryption.
IDEA IDEA
A 64-bit block cipher designed by Xuejia Lai and James Massey. A 64-bit block cipher designed by Xuejia Lai and James Massey.
[IDEA] [IDEA]
Message Authentication Code (MAC) Message Authentication Code (MAC)
A Message Authentication Code is a one-way hash computed from a A Message Authentication Code is a one-way hash computed from a
message and some secret data. It is difficult to forge without message and some secret data. It is difficult to forge without
knowing the secret data. Its purpose is to detect if the message knowing the secret data. Its purpose is to detect if the message
has been altered. has been altered.
master secret master secret
Secure secret data used for generating encryption keys, MAC Secure secret data used for generating encryption keys, MAC
secrets, and IVs. secrets, and IVs.
MD5 MD5
MD5 is a secure hashing function that converts an arbitrarily MD5 is a secure hashing function that converts an arbitrarily long
long data stream into a digest of fixed size (16 bytes). [MD5] data stream into a hash of fixed size (16 bytes). [MD5]
public key cryptography public key cryptography
A class of cryptographic techniques employing two-key ciphers. A class of cryptographic techniques employing two-key ciphers.
Messages encrypted with the public key can only be decrypted with Messages encrypted with the public key can only be decrypted with
the associated private key. Conversely, messages signed with the the associated private key. Conversely, messages signed with the
private key can be verified with the public key. private key can be verified with the public key.
one-way hash function one-way hash function
A one-way transformation that converts an arbitrary amount of A one-way transformation that converts an arbitrary amount of data
data into a fixed-length hash. It is computationally hard to into a fixed-length hash. It is computationally hard to reverse
reverse the transformation or to find collisions. MD5 and SHA are the transformation or to find collisions. MD5 and SHA are examples
examples of one-way hash functions. of one-way hash functions.
RC2 RC2
A block cipher developed by Ron Rivest, described in [RC2]. A block cipher developed by Ron Rivest, described in [RC2].
RC4 RC4
A stream cipher invented by Ron Rivest. A compatible cipher is A stream cipher invented by Ron Rivest. A compatible cipher is
described in [SCH]. described in [SCH].
RSA RSA
A very widely used public-key algorithm that can be used for A very widely used public-key algorithm that can be used for
either encryption or digital signing. [RSA] either encryption or digital signing. [RSA]
server server
The server is the application entity that responds to requests The server is the application entity that responds to requests for
for connections from clients. See also under client. connections from clients. See also under client.
session session
A TLS session is an association between a client and a server. A TLS session is an association between a client and a server.
Sessions are created by the handshake protocol. Sessions define a Sessions are created by the handshake protocol. Sessions define a
set of cryptographic security parameters that can be shared among set of cryptographic security parameters that can be shared among
multiple connections. Sessions are used to avoid the expensive multiple connections. Sessions are used to avoid the expensive
negotiation of new security parameters for each connection. negotiation of new security parameters for each connection.
session identifier session identifier
A session identifier is a value generated by a server that A session identifier is a value generated by a server that
identifies a particular session. identifies a particular session.
server write key server write key
The key used to encrypt data written by the server. The key used to encrypt data written by the server.
server write MAC secret server write MAC key
The secret data used to authenticate data written by the server. The secret data used to authenticate data written by the server.
SHA SHA
The Secure Hash Algorithm is defined in FIPS PUB 180-2. It The Secure Hash Algorithm is defined in FIPS PUB 180-2. It
produces a 20-byte output. Note that all references to SHA produces a 20-byte output. Note that all references to SHA
actually use the modified SHA-1 algorithm. [SHA] actually use the modified SHA-1 algorithm. [SHA]
SSL SSL
Netscape's Secure Socket Layer protocol [SSL3]. TLS is based on Netscape's Secure Socket Layer protocol [SSL3]. TLS is based on
SSL Version 3.0 SSL Version 3.0
stream cipher stream cipher
An encryption algorithm that converts a key into a An encryption algorithm that converts a key into a
cryptographically strong keystream, which is then exclusive-ORed cryptographically strong keystream, which is then exclusive-ORed
with the plaintext. with the plaintext.
symmetric cipher symmetric cipher
See bulk cipher. See bulk cipher.
Transport Layer Security (TLS) Transport Layer Security (TLS)
This protocol; also, the Transport Layer Security working group This protocol; also, the Transport Layer Security working group of
of the Internet Engineering Task Force (IETF). See "Comments" at the Internet Engineering Task Force (IETF). See "Comments" at the
the end of this document. end of this document.
Appendix C. CipherSuite Definitions Appendix C. CipherSuite Definitions
CipherSuite Key Cipher Hash CipherSuite Key Cipher Hash
Exchange Exchange
TLS_NULL_WITH_NULL_NULL NULL NULL NULL TLS_NULL_WITH_NULL_NULL NULL NULL NULL
TLS_RSA_WITH_NULL_MD5 RSA NULL MD5 TLS_RSA_WITH_NULL_MD5 RSA NULL MD5
TLS_RSA_WITH_NULL_SHA RSA NULL SHA TLS_RSA_WITH_NULL_SHA RSA NULL SHA
TLS_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5 TLS_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5
TLS_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA TLS_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA
TLS_RSA_WITH_IDEA_CBC_SHA RSA IDEA_CBC SHA
TLS_RSA_WITH_DES_CBC_SHA RSA DES_CBC SHA
TLS_RSA_WITH_3DES_EDE_CBC_SHA RSA 3DES_EDE_CBC SHA TLS_RSA_WITH_3DES_EDE_CBC_SHA RSA 3DES_EDE_CBC SHA
TLS_RSA_WITH_AES_128_CBC_SHA RSA AES_128_CBC SHA TLS_RSA_WITH_AES_128_CBC_SHA RSA AES_128_CBC SHA
TLS_RSA_WITH_AES_256_CBC_SHA RSA AES_256_CBC SHA TLS_RSA_WITH_AES_256_CBC_SHA RSA AES_256_CBC SHA
TLS_DH_DSS_WITH_DES_CBC_SHA DH_DSS DES_CBC SHA
TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA DH_DSS 3DES_EDE_CBC SHA TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA DH_DSS 3DES_EDE_CBC SHA
TLS_DH_RSA_WITH_DES_CBC_SHA DH_RSA DES_CBC SHA
TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA DH_RSA 3DES_EDE_CBC SHA TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA DH_RSA 3DES_EDE_CBC SHA
TLS_DHE_DSS_WITH_DES_CBC_SHA DHE_DSS DES_CBC SHA
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA DHE_DSS 3DES_EDE_CBC SHA TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA DHE_DSS 3DES_EDE_CBC SHA
TLS_DHE_RSA_WITH_DES_CBC_SHA DHE_RSA DES_CBC SHA
TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA DHE_RSA 3DES_EDE_CBC SHA TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA DHE_RSA 3DES_EDE_CBC SHA
TLS_DH_anon_WITH_RC4_128_MD5 DH_anon RC4_128 MD5 TLS_DH_anon_WITH_RC4_128_MD5 DH_anon RC4_128 MD5
TLS_DH_anon_WITH_DES_CBC_SHA DH_anon DES_CBC SHA
TLS_DH_anon_WITH_3DES_EDE_CBC_SHA DH_anon 3DES_EDE_CBC SHA TLS_DH_anon_WITH_3DES_EDE_CBC_SHA DH_anon 3DES_EDE_CBC SHA
TLS_DH_DSS_WITH_AES_128_CBC_SHA DH_DSS AES_128_CBC SHA TLS_DH_DSS_WITH_AES_128_CBC_SHA DH_DSS AES_128_CBC SHA
TLS_DH_RSA_WITH_AES_128_CBC_SHA DH_RSA AES_128_CBC SHA TLS_DH_RSA_WITH_AES_128_CBC_SHA DH_RSA AES_128_CBC SHA
TLS_DHE_DSS_WITH_AES_128_CBC_SHA DHE_DSS AES_128_CBC SHA TLS_DHE_DSS_WITH_AES_128_CBC_SHA DHE_DSS AES_128_CBC SHA
TLS_DHE_RSA_WITH_AES_128_CBC_SHA DHE_RSA AES_128_CBC SHA TLS_DHE_RSA_WITH_AES_128_CBC_SHA DHE_RSA AES_128_CBC SHA
TLS_DH_anon_WITH_AES_128_CBC_SHA DH_anon AES_128_CBC SHA TLS_DH_anon_WITH_AES_128_CBC_SHA DH_anon AES_128_CBC SHA
TLS_DH_DSS_WITH_AES_256_CBC_SHA DH_DSS AES_256_CBC SHA TLS_DH_DSS_WITH_AES_256_CBC_SHA DH_DSS AES_256_CBC SHA
TLS_DH_RSA_WITH_AES_256_CBC_SHA DH_RSA AES_256_CBC SHA TLS_DH_RSA_WITH_AES_256_CBC_SHA DH_RSA AES_256_CBC SHA
TLS_DHE_DSS_WITH_AES_256_CBC_SHA DHE_DSS AES_256_CBC SHA TLS_DHE_DSS_WITH_AES_256_CBC_SHA DHE_DSS AES_256_CBC SHA
TLS_DHE_RSA_WITH_AES_256_CBC_SHA DHE_RSA AES_256_CBC SHA TLS_DHE_RSA_WITH_AES_256_CBC_SHA DHE_RSA AES_256_CBC SHA
TLS_DH_anon_WITH_AES_256_CBC_SHA DH_anon AES_256_CBC SHA TLS_DH_anon_WITH_AES_256_CBC_SHA DH_anon AES_256_CBC SHA
Key Key Expanded IV Block
Exchange Cipher Type Material Key Material Size Size
Algorithm Description Key size limit
DHE_DSS Ephemeral DH with DSS signatures None
DHE_RSA Ephemeral DH with RSA signatures None
DH_anon Anonymous DH, no signatures None
DH_DSS DH with DSS-based certificates None
DH_RSA DH with RSA-based certificates None
NULL No key exchange N/A
RSA RSA key exchange None
Key Expanded IV Block
Cipher Type Material Key Material Size Size
NULL Stream 0 0 0 N/A NULL Stream 0 0 0 N/A
IDEA_CBC Block 16 16 8 8 RC4_128 Stream 16 16 0 N/A
RC4_128 Stream 16 16 0 N/A 3DES_EDE_CBC Block 24 24 8 8
DES_CBC Block 8 8 8 8
3DES_EDE_CBC Block 24 24 8 8
Type Type
Indicates whether this is a stream cipher or a block cipher Indicates whether this is a stream cipher or a block cipher
running in CBC mode. running in CBC mode.
Key Material Key Material
The number of bytes from the key_block that are used for The number of bytes from the key_block that are used for
generating the write keys. generating the write keys.
Expanded Key Material Expanded Key Material
The number of bytes actually fed into the encryption algorithm. The number of bytes actually fed into the encryption algorithm.
IV Size IV Size
The amount of data needed to be generated for the initialization The amount of data needed to be generated for the initialization
vector. Zero for stream ciphers; equal to the block size for vector. Zero for stream ciphers; equal to the block size for block
block ciphers (this is equal to ciphers (this is equal to SecurityParameters.record_iv_length).
SecurityParameters.record_iv_length).
Block Size Block Size
The amount of data a block cipher enciphers in one chunk; a The amount of data a block cipher enciphers in one chunk; a block
block cipher running in CBC mode can only encrypt an even cipher running in CBC mode can only encrypt an even multiple of
multiple of its block size. its block size.
Hash Hash Padding
function Size Size
NULL 0 0
MD5 16 48
SHA 20 40
Appendix D. Implementation Notes Appendix D. Implementation Notes
The TLS protocol cannot prevent many common security mistakes. This The TLS protocol cannot prevent many common security mistakes. This
section provides several recommendations to assist implementors. section provides several recommendations to assist implementors.
D.1 Random Number Generation and Seeding D.1 Random Number Generation and Seeding
TLS requires a cryptographically secure pseudorandom number generator TLS requires a cryptographically secure pseudorandom number generator
(PRNG). Care must be taken in designing and seeding PRNGs. PRNGs (PRNG). Care must be taken in designing and seeding PRNGs. PRNGs
based on secure hash operations, most notably SHA-1, are acceptable, based on secure hash operations, most notably SHA-1, are acceptable,
skipping to change at page 99, line ? skipping to change at page 80, line 21
cases like a ClientHello that is split to several small cases like a ClientHello that is split to several small
fragments? fragments?
- Do you ignore the TLS record layer version number in all TLS - Do you ignore the TLS record layer version number in all TLS
records before ServerHello (see Appendix E.1)? records before ServerHello (see Appendix E.1)?
- Do you handle TLS extensions in ClientHello correctly, - Do you handle TLS extensions in ClientHello correctly,
including omitting the extensions field completely? including omitting the extensions field completely?
- Do you support renegotiation, both client and server initiated? - Do you support renegotiation, both client and server initiated?
While renegotiation this is an optional feature, supporting While renegotiation is an optional feature, supporting
it is highly recommended. it is highly recommended.
- When the server has requested a client certificate, but no - When the server has requested a client certificate, but no
suitable certificate is available, do you correctly send suitable certificate is available, do you correctly send
an empty Certificate message, instead of omitting the whole an empty Certificate message, instead of omitting the whole
message (see Section 7.4.6)? message (see Section 7.4.6)?
Cryptographic details: Cryptographic details:
- In RSA-encrypted Premaster Secret, do you correctly send and - In RSA-encrypted Premaster Secret, do you correctly send and
skipping to change at page 99, line ? skipping to change at page 82, line 51
ClientHello.client_version. For example, if the server supports TLS ClientHello.client_version. For example, if the server supports TLS
1.0, 1.1, and 1.2, and client_version is TLS 1.0, the server will 1.0, 1.1, and 1.2, and client_version is TLS 1.0, the server will
proceed with a TLS 1.0 ServerHello. If server supports (or is willing proceed with a TLS 1.0 ServerHello. If server supports (or is willing
to use) only versions greater than client_version, it MUST send a to use) only versions greater than client_version, it MUST send a
"protocol_version" alert message and close the connection. "protocol_version" alert message and close the connection.
Whenever a client already knows the highest protocol known to a Whenever a client already knows the highest protocol known to a
server (for example, when resuming a session), it SHOULD initiate the server (for example, when resuming a session), it SHOULD initiate the
connection in that native protocol. connection in that native protocol.
Note: some server implementations are known to implement version Note: some server implementations are known to implement version
negotiation incorrectly. For example, there are buggy TLS 1.0 servers negotiation incorrectly. For example, there are buggy TLS 1.0 servers
that simply close the connection when the client offers a version that simply close the connection when the client offers a version
newer than TLS 1.0. Also, it is known that some servers will refuse newer than TLS 1.0. Also, it is known that some servers will refuse
connection if any TLS extensions are included in ClientHello. connection if any TLS extensions are included in ClientHello.
Interoperability with such buggy servers is a complex topic beyond Interoperability with such buggy servers is a complex topic beyond
the scope of this document, and may require multiple connection the scope of this document, and may require multiple connection
attempts by the client. attempts by the client.
Earlier versions of the TLS specification were not fully clear on Earlier versions of the TLS specification were not fully clear on
what the record layer version number (TLSPlaintext.version) should what the record layer version number (TLSPlaintext.version) should
skipping to change at page 99, line ? skipping to change at page 83, line 33
complex topic beyond the scope of this document. complex topic beyond the scope of this document.
E.2 Compatibility with SSL 2.0 E.2 Compatibility with SSL 2.0
TLS 1.2 clients that wish to support SSL 2.0 servers MUST send TLS 1.2 clients that wish to support SSL 2.0 servers MUST send
version 2.0 CLIENT-HELLO messages defined in [SSL2]. The message MUST version 2.0 CLIENT-HELLO messages defined in [SSL2]. The message MUST
contain the same version number as would be used for ordinary contain the same version number as would be used for ordinary
ClientHello, and MUST encode the supported TLS ciphersuites in the ClientHello, and MUST encode the supported TLS ciphersuites in the
CIPHER-SPECS-DATA field as described below. CIPHER-SPECS-DATA field as described below.
Warning: The ability to send version 2.0 CLIENT-HELLO messages will be Warning: The ability to send version 2.0 CLIENT-HELLO messages will
phased out with all due haste, since the newer ClientHello format be phased out with all due haste, since the newer ClientHello format
provides better mechanisms for moving to newer versions and provides better mechanisms for moving to newer versions and
negotiating extensions. TLS 1.2 clients SHOULD NOT support SSL 2.0. negotiating extensions. TLS 1.2 clients SHOULD NOT support SSL 2.0.
However, even TLS servers that do not support SSL 2.0 SHOULD accept However, even TLS servers that do not support SSL 2.0 MAY accept
version 2.0 CLIENT-HELLO messages. The message is presented below in version 2.0 CLIENT-HELLO messages. The message is presented below in
sufficient detail for TLS server implementors; the true definition is sufficient detail for TLS server implementors; the true definition is
still assumed to be [SSL2]. still assumed to be [SSL2].
For negotiation purposes, 2.0 CLIENT-HELLO is interpreted the same For negotiation purposes, 2.0 CLIENT-HELLO is interpreted the same
way as a ClientHello with a "null" compression method and no way as a ClientHello with a "null" compression method and no
extensions. Note that this message MUST be sent directly on the wire, extensions. Note that this message MUST be sent directly on the wire,
not wrapped as a TLS record. For the purposes of calculating Finished not wrapped as a TLS record. For the purposes of calculating Finished
and CertificateVerify, the msg_length field is not considered to be a and CertificateVerify, the msg_length field is not considered to be a
part of the handshake message. part of the handshake message.
uint8 V2CipherSpec[3]; uint8 V2CipherSpec[3];
struct { struct {
uint16 msg_length; uint16 msg_length;
uint8 msg_type; uint8 msg_type;
Version version; Version version;
uint16 cipher_spec_length; uint16 cipher_spec_length;
uint16 session_id_length; uint16 session_id_length;
uint16 challenge_length; uint16 challenge_length;
V2CipherSpec cipher_specs[V2ClientHello.cipher_spec_length]; V2CipherSpec cipher_specs[V2ClientHello.cipher_spec_length];
opaque session_id[V2ClientHello.session_id_length]; opaque session_id[V2ClientHello.session_id_length];
opaque challenge[V2ClientHello.challenge_length; opaque challenge[V2ClientHello.challenge_length;
} V2ClientHello; } V2ClientHello;
msg_length msg_length
The highest bit MUST be 1; the remaining bits contain the The highest bit MUST be 1; the remaining bits contain the length
length of the following data in bytes. of the following data in bytes.
msg_type msg_type
This field, in conjunction with the version field, identifies a This field, in conjunction with the version field, identifies a
version 2 client hello message. The value MUST be one (1). version 2 client hello message. The value MUST be one (1).
version version
Equal to ClientHello.client_version. Equal to ClientHello.client_version.
cipher_spec_length cipher_spec_length
This field is the total length of the field cipher_specs. It This field is the total length of the field cipher_specs. It
cannot be zero and MUST be a multiple of the V2CipherSpec length cannot be zero and MUST be a multiple of the V2CipherSpec length
(3). (3).
session_id_length session_id_length
This field MUST have a value of zero for a client that claims to This field MUST have a value of zero for a client that claims to
support TLS 1.2. support TLS 1.2.
challenge_length challenge_length
The length in bytes of the client's challenge to the server to The length in bytes of the client's challenge to the server to
authenticate itself. Historically, permissible values are between authenticate itself. Historically, permissible values are between
16 and 32 bytes inclusive. When using the SSLv2 backward 16 and 32 bytes inclusive. When using the SSLv2 backward
compatible handshake the client SHOULD use a 32 byte challenge. compatible handshake the client SHOULD use a 32 byte challenge.
cipher_specs cipher_specs
This is a list of all CipherSpecs the client is willing and able This is a list of all CipherSpecs the client is willing and able
to use. In addition to the 2.0 cipher specs defined in [SSL2], to use. In addition to the 2.0 cipher specs defined in [SSL2],
this includes the TLS cipher suites normally sent in this includes the TLS cipher suites normally sent in
ClientHello.cipher_suites, each cipher suite prefixed by a zero ClientHello.cipher_suites, each cipher suite prefixed by a zero
byte. For example, TLS ciphersuite {0x00,0x0A} would be sent as byte. For example, TLS ciphersuite {0x00,0x0A} would be sent as
{0x00,0x00,0x0A}. {0x00,0x00,0x0A}.
session_id session_id
This field MUST be empty. This field MUST be empty.
challenge challenge
Corresponds to ClientHello.random. If the challenge length is Corresponds to ClientHello.random. If the challenge length is less
less than 32, the TLS server will pad the data with leading than 32, the TLS server will pad the data with leading (note: not
(note: not trailing) zero bytes to make it 32 bytes long. trailing) zero bytes to make it 32 bytes long.
Note: Requests to resume a TLS session MUST use a TLS client hello. Note: Requests to resume a TLS session MUST use a TLS client hello.
E.3. Avoiding Man-in-the-Middle Version Rollback E.3. Avoiding Man-in-the-Middle Version Rollback
When TLS clients fall back to Version 2.0 compatibility mode, they When TLS clients fall back to Version 2.0 compatibility mode, they
MUST use special PKCS#1 block formatting. This is done so that TLS MUST use special PKCS#1 block formatting. This is done so that TLS
servers will reject Version 2.0 sessions with TLS-capable clients. servers will reject Version 2.0 sessions with TLS-capable clients.
When a client negotiates SSL 2.0 but also supports TLS, it MUST set When a client negotiates SSL 2.0 but also supports TLS, it MUST set
the right-hand (least-significant) 8 random bytes of the PKCS padding the right-hand (least-significant) 8 random bytes of the PKCS padding
(not including the terminal null of the padding) for the RSA (not including the terminal null of the padding) for the RSA
skipping to change at page 99, line ? skipping to change at page 86, line 43
its certificate message must provide a valid certificate chain its certificate message must provide a valid certificate chain
leading to an acceptable certificate authority. Similarly, leading to an acceptable certificate authority. Similarly,
authenticated clients must supply an acceptable certificate to the authenticated clients must supply an acceptable certificate to the
server. Each party is responsible for verifying that the other's server. Each party is responsible for verifying that the other's
certificate is valid and has not expired or been revoked. certificate is valid and has not expired or been revoked.
The general goal of the key exchange process is to create a The general goal of the key exchange process is to create a
pre_master_secret known to the communicating parties and not to pre_master_secret known to the communicating parties and not to
attackers. The pre_master_secret will be used to generate the attackers. The pre_master_secret will be used to generate the
master_secret (see Section 8.1). The master_secret is required to master_secret (see Section 8.1). The master_secret is required to
generate the finished messages, encryption keys, and MAC secrets (see generate the finished messages, encryption keys, and MAC keys (see
Sections 7.4.9 and 6.3). By sending a correct finished message, Sections 7.4.9 and 6.3). By sending a correct finished message,
parties thus prove that they know the correct pre_master_secret. parties thus prove that they know the correct pre_master_secret.
F.1.1.1. Anonymous Key Exchange F.1.1.1. Anonymous Key Exchange
Completely anonymous sessions can be established using Diffie-Hellman Completely anonymous sessions can be established using Diffie-Hellman
for key exchange. The server's public parameters are contained in the for key exchange. The server's public parameters are contained in the
server key exchange message and the client's are sent in the client server key exchange message and the client's are sent in the client
key exchange message. Eavesdroppers who do not know the private key exchange message. Eavesdroppers who do not know the private
values should not be able to find the Diffie-Hellman result (i.e. the values should not be able to find the Diffie-Hellman result (i.e. the
pre_master_secret). pre_master_secret).
Warning: Completely anonymous connections only provide protection Warning: Completely anonymous connections only provide protection
against passive eavesdropping. Unless an independent tamper- against passive eavesdropping. Unless an independent tamper-proof
proof channel is used to verify that the finished messages channel is used to verify that the finished messages were not
were not replaced by an attacker, server authentication is replaced by an attacker, server authentication is required in
required in environments where active man-in-the-middle environments where active man-in-the-middle attacks are a concern.
attacks are a concern.
F.1.1.2. RSA Key Exchange and Authentication F.1.1.2. RSA Key Exchange and Authentication
With RSA, key exchange and server authentication are combined. The With RSA, key exchange and server authentication are combined. The
public key is contained in the server's certificate. Note that public key is contained in the server's certificate. Note that
compromise of the server's static RSA key results in a loss of compromise of the server's static RSA key results in a loss of
confidentiality for all sessions protected under that static key. TLS confidentiality for all sessions protected under that static key. TLS
users desiring Perfect Forward Secrecy should use DHE cipher suites. users desiring Perfect Forward Secrecy should use DHE cipher suites.
The damage done by exposure of a private key can be limited by The damage done by exposure of a private key can be limited by
changing one's private key (and certificate) frequently. changing one's private key (and certificate) frequently.
skipping to change at page 99, line ? skipping to change at page 89, line 26
result, the parties will not accept each others' finished messages. result, the parties will not accept each others' finished messages.
Without the master_secret, the attacker cannot repair the finished Without the master_secret, the attacker cannot repair the finished
messages, so the attack will be discovered. messages, so the attack will be discovered.
F.1.4. Resuming Sessions F.1.4. Resuming Sessions
When a connection is established by resuming a session, new When a connection is established by resuming a session, new
ClientHello.random and ServerHello.random values are hashed with the ClientHello.random and ServerHello.random values are hashed with the
session's master_secret. Provided that the master_secret has not been session's master_secret. Provided that the master_secret has not been
compromised and that the secure hash operations used to produce the compromised and that the secure hash operations used to produce the
encryption keys and MAC secrets are secure, the connection should be encryption keys and MAC keys are secure, the connection should be
secure and effectively independent from previous connections. secure and effectively independent from previous connections.
Attackers cannot use known encryption keys or MAC secrets to Attackers cannot use known encryption keys or MAC secrets to
compromise the master_secret without breaking the secure hash compromise the master_secret without breaking the secure hash
operations. operations.
Sessions cannot be resumed unless both the client and server agree. Sessions cannot be resumed unless both the client and server agree.
If either party suspects that the session may have been compromised, If either party suspects that the session may have been compromised,
or that certificates may have expired or been revoked, it should or that certificates may have expired or been revoked, it should
force a full handshake. An upper limit of 24 hours is suggested for force a full handshake. An upper limit of 24 hours is suggested for
session ID lifetimes, since an attacker who obtains a master_secret session ID lifetimes, since an attacker who obtains a master_secret
skipping to change at page 99, line ? skipping to change at page 89, line 50
stable storage. stable storage.
F.2. Protecting Application Data F.2. Protecting Application Data
The master_secret is hashed with the ClientHello.random and The master_secret is hashed with the ClientHello.random and
ServerHello.random to produce unique data encryption keys and MAC ServerHello.random to produce unique data encryption keys and MAC
secrets for each connection. secrets for each connection.
Outgoing data is protected with a MAC before transmission. To prevent Outgoing data is protected with a MAC before transmission. To prevent
message replay or modification attacks, the MAC is computed from the message replay or modification attacks, the MAC is computed from the
MAC secret, the sequence number, the message length, the message MAC key, the sequence number, the message length, the message
contents, and two fixed character strings. The message type field is contents, and two fixed character strings. The message type field is
necessary to ensure that messages intended for one TLS Record Layer necessary to ensure that messages intended for one TLS Record Layer
client are not redirected to another. The sequence number ensures client are not redirected to another. The sequence number ensures
that attempts to delete or reorder messages will be detected. Since that attempts to delete or reorder messages will be detected. Since
sequence numbers are 64 bits long, they should never overflow. sequence numbers are 64 bits long, they should never overflow.
Messages from one party cannot be inserted into the other's output, Messages from one party cannot be inserted into the other's output,
since they use independent MAC secrets. Similarly, the server-write since they use independent MAC keys. Similarly, the server-write and
and client-write keys are independent, so stream cipher keys are used client-write keys are independent, so stream cipher keys are used
only once. only once.
If an attacker does break an encryption key, all messages encrypted If an attacker does break an encryption key, all messages encrypted
with it can be read. Similarly, compromise of a MAC key can make with it can be read. Similarly, compromise of a MAC key can make
message modification attacks possible. Because MACs are also message modification attacks possible. Because MACs are also
encrypted, message-alteration attacks generally require breaking the encrypted, message-alteration attacks generally require breaking the
encryption algorithm as well as the MAC. encryption algorithm as well as the MAC.
Note: MAC secrets may be larger than encryption keys, so messages can Note: MAC keys may be larger than encryption keys, so messages can
remain tamper resistant even if encryption keys are broken. remain tamper resistant even if encryption keys are broken.
F.3. Explicit IVs F.3. Explicit IVs
[CBCATT] describes a chosen plaintext attack on TLS that depends on [CBCATT] describes a chosen plaintext attack on TLS that depends on
knowing the IV for a record. Previous versions of TLS [TLS1.0] used knowing the IV for a record. Previous versions of TLS [TLS1.0] used
the CBC residue of the previous record as the IV and therefore the CBC residue of the previous record as the IV and therefore
enabled this attack. This version uses an explicit IV in order to enabled this attack. This version uses an explicit IV in order to
protect against this attack. protect against this attack.
F.4. Security of Composite Cipher Modes F.4. Security of Composite Cipher Modes
skipping to change at page 99, line ? skipping to change at page 92, line 14
cryptographic functions should be used. Short public keys and cryptographic functions should be used. Short public keys and
anonymous servers should be used with great caution. Implementations anonymous servers should be used with great caution. Implementations
and users must be careful when deciding which certificates and and users must be careful when deciding which certificates and
certificate authorities are acceptable; a dishonest certificate certificate authorities are acceptable; a dishonest certificate
authority can do tremendous damage. authority can do tremendous damage.
Changes in This Version Changes in This Version
[RFC Editor: Please delete this] [RFC Editor: Please delete this]
- Redid the hash function advertisements for CertificateRequest - SSLv2 backward compatibility downgraded to MAY
and the client-side extension. They are now pairs of
hash/signature and the semantics are clearly defined for
all uses of signatures (hopefully). [Issue 41]
- Clarified the DH group checking per list discussion [Issue 35] - Altered DSA hash rules to more closely match FIPS186-3 and
PKIX, plus remove OID restriction.
- Added a note about DSS vs. DSA [Issue 58] - verify_length no longer in SecurityParameters
- Editorial issues [Issue 59] - Moved/cleaned up cert selection text for server cert
when signature_algorithms is not specified.
- Cleaned up certificate text in 7.4.2 and 7.4.6 [Issue 57] - Other editorial changes.
Normative References Normative References
[AES] National Institute of Standards and Technology, [AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard (AES)" "Specification for the Advanced Encryption Standard (AES)"
FIPS 197. November 26, 2001. FIPS 197. November 26, 2001.
[3DES] National Institute of Standards and Technology, [3DES] National Institute of Standards and Technology,
"Recommendation for the Triple Data Encryption Algorithm "Recommendation for the Triple Data Encryption Algorithm
(TDEA) Block Cipher", NIST Special Publication 800-67, May (TDEA) Block Cipher", NIST Special Publication 800-67, May
2004. 2004.
[DES] National Institute of Standards and Technology, "Data [DES] National Institute of Standards and Technology, "Data
skipping to change at page 99, line ? skipping to change at page 93, line 8
Hashing for Message Authentication", RFC 2104, February Hashing for Message Authentication", RFC 2104, February
1997. 1997.
[IDEA] X. Lai, "On the Design and Security of Block Ciphers," ETH [IDEA] X. Lai, "On the Design and Security of Block Ciphers," ETH
Series in Information Processing, v. 1, Konstanz: Hartung- Series in Information Processing, v. 1, Konstanz: Hartung-
Gorre Verlag, 1992. Gorre Verlag, 1992.
[MD5] Rivest, R., "The MD5 Message Digest Algorithm", RFC 1321, [MD5] Rivest, R., "The MD5 Message Digest Algorithm", RFC 1321,
April 1992. April 1992.
[PKCS1] J. Jonsson, B. Kaliski, "Public-Key Cryptography Standards [PKCS1] J. Jonsson, B. Kaliski, "Public-Key Cryptography Standards
(PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC (PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC
3447, February 2003. 3447, February 2003.
[PKIX] Housley, R., Ford, W., Polk, W. and D. Solo, "Internet X.509 [PKIX] Housley, R., Ford, W., Polk, W. and D. Solo, "Internet X.509
Public Key Infrastructure Certificate and Certificate Public Key Infrastructure Certificate and Certificate
Revocation List (CRL) Profile", RFC 3280, April 2002. Revocation List (CRL) Profile", RFC 3280, April 2002.
[RC2] Rivest, R., "A Description of the RC2(r) Encryption [RC2] Rivest, R., "A Description of the RC2(r) Encryption
Algorithm", RFC 2268, March 1998. Algorithm", RFC 2268, March 1998.
skipping to change at page 99, line ? skipping to change at page 93, line 45
[AEAD] Mcgrew, D., "Authenticated Encryption", February 2007, [AEAD] Mcgrew, D., "Authenticated Encryption", February 2007,
draft-mcgrew-auth-enc-02.txt. draft-mcgrew-auth-enc-02.txt.
[AH] Kent, S., and Atkinson, R., "IP Authentication Header", RFC [AH] Kent, S., and Atkinson, R., "IP Authentication Header", RFC
4302, December 2005. 4302, December 2005.
[BLEI] Bleichenbacher D., "Chosen Ciphertext Attacks against [BLEI] Bleichenbacher D., "Chosen Ciphertext Attacks against
Protocols Based on RSA Encryption Standard PKCS #1" in Protocols Based on RSA Encryption Standard PKCS #1" in
Advances in Cryptology -- CRYPTO'98, LNCS vol. 1462, pages: Advances in Cryptology -- CRYPTO'98, LNCS vol. 1462, pages:
1-12, 1998. 1-12, 1998.
[CBCATT] Moeller, B., "Security of CBC Ciphersuites in SSL/TLS: [CBCATT] Moeller, B., "Security of CBC Ciphersuites in SSL/TLS:
Problems and Countermeasures", Problems and Countermeasures",
http://www.openssl.org/~bodo/tls-cbc.txt. http://www.openssl.org/~bodo/tls-cbc.txt.
[CBCTIME] Canvel, B., Hiltgen, A., Vaudenay, S., and M. Vuagnoux, [CBCTIME] Canvel, B., Hiltgen, A., Vaudenay, S., and M. Vuagnoux,
"Password Interception in a SSL/TLS Channel", Advances in "Password Interception in a SSL/TLS Channel", Advances in
Cryptology -- CRYPTO 2003, LNCS vol. 2729, 2003. Cryptology -- CRYPTO 2003, LNCS vol. 2729, 2003.
[CCM] "NIST Special Publication 800-38C: The CCM Mode for [CCM] "NIST Special Publication 800-38C: The CCM Mode for
Authentication and Confidentiality", Authentication and Confidentiality",
http://csrc.nist.gov/publications/nistpubs/800-38C/ http://csrc.nist.gov/publications/nistpubs/800-38C/
SP800-38C.pdf SP800-38C.pdf
[DSS-3] NIST FIPS PUB 186-3 Draft, "Digital Signature Standard,"
National Institute of Standards and Technology, U.S.
Department of Commerce, 2006.
[ENCAUTH] Krawczyk, H., "The Order of Encryption and Authentication [ENCAUTH] Krawczyk, H., "The Order of Encryption and Authentication
for Protecting Communications (Or: How Secure is SSL?)", for Protecting Communications (Or: How Secure is SSL?)",
Crypto 2001. Crypto 2001.
[ESP] Kent, S., and Atkinson, R., "IP Encapsulating Security [ESP] Kent, S., and Atkinson, R., "IP Encapsulating Security
Payload (ESP)", RFC 4303, December 2005. Payload (ESP)", RFC 4303, December 2005.
[FI06] Hal Finney, "Bleichenbacher's RSA signature forgery based on [FI06] Hal Finney, "Bleichenbacher's RSA signature forgery based on
implementation error", ietf-openpgp@imc.org mailing list, 27 implementation error", ietf-openpgp@imc.org mailing list, 27
August 2006, http://www.imc.org/ietf-openpgp/mail- August 2006, http://www.imc.org/ietf-openpgp/mail-
archive/msg14307.html. archive/msg14307.html.
[GCM] "NIST Special Publication 800-38D DRAFT (June, 2007): [GCM] "NIST Special Publication 800-38D DRAFT (June, 2007):
Recommendation for Block Cipher Modes of Operation: Recommendation for Block Cipher Modes of Operation:
Galois/Counter Mode (GCM) and GMAC" Galois/Counter Mode (GCM) and GMAC"
[IKEALG] Schiller, J., "Cryptographic Algorithms for Use in the [IKEALG] Schiller, J., "Cryptographic Algorithms for Use in the
Internet Key Exchange Version 2 (IKEv2)", RFC 4307, December Internet Key Exchange Version 2 (IKEv2)", RFC 4307, December
2005. 2005.
[KEYSIZ] Orman, H., and Hoffman, P., "Determining Strengths For [KEYSIZ] Orman, H., and Hoffman, P., "Determining Strengths For
Public Keys Used For Exchanging Symmetric Keys" RFC 3766, Public Keys Used For Exchanging Symmetric Keys" RFC 3766,
April 2004. April 2004.
skipping to change at page 99, line ? skipping to change at page 95, line 5
[MODP] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) [MODP] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
Diffie-Hellman groups for Internet Key Exchange (IKE)", RFC Diffie-Hellman groups for Internet Key Exchange (IKE)", RFC
3526, May 2003. 3526, May 2003.
[PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate Syntax [PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate Syntax
Standard," version 1.5, November 1993. Standard," version 1.5, November 1993.
[PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message Syntax [PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message Syntax
Standard," version 1.5, November 1993. Standard," version 1.5, November 1993.
[RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker, [RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker, "Randomness
"Randomness Requirements for Security", BCP 106, RFC 4086, Requirements for Security", BCP 106, RFC 4086, June 2005.
June 2005.
[RFC3749] Hollenbeck, S., "Transport Layer Security Protocol [RFC3749] Hollenbeck, S., "Transport Layer Security Protocol
Compression Methods", RFC 3749, May 2004. Compression Methods", RFC 3749, May 2004.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., [RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
Wright, T., "Transport Layer Security (TLS) Extensions", RFC Wright, T., "Transport Layer Security (TLS) Extensions", RFC
4366, April 2006. 4366, April 2006.
[RSA] R. Rivest, A. Shamir, and L. M. Adleman, "A Method for [RSA] R. Rivest, A. Shamir, and L. M. Adleman, "A Method for
Obtaining Digital Signatures and Public-Key Cryptosystems," Obtaining Digital Signatures and Public-Key Cryptosystems,"
skipping to change at page 99, line ? skipping to change at page 96, line 5
Suites for Transport Layer Security (TLS)", RFC 4492, May Suites for Transport Layer Security (TLS)", RFC 4492, May
2006. 2006.
[TLSEXT] Eastlake, D.E., "Transport Layer Security (TLS) Extensions: [TLSEXT] Eastlake, D.E., "Transport Layer Security (TLS) Extensions:
Extension Definitions", July 2007, draft-ietf-tls- Extension Definitions", July 2007, draft-ietf-tls-
rfc4366-bis-00.txt. rfc4366-bis-00.txt.
[TLSPGP] Mavrogiannopoulos, N., "Using OpenPGP keys for TLS [TLSPGP] Mavrogiannopoulos, N., "Using OpenPGP keys for TLS
authentication", draft-ietf-tls-openpgp-keys-11, July 2006. authentication", draft-ietf-tls-openpgp-keys-11, July 2006.
[TLSPSK] Eronen, P., Tschofenig, H., "Pre-Shared Key Ciphersuites [TLSPSK] Eronen, P., Tschofenig, H., "Pre-Shared Key Ciphersuites for
for Transport Layer Security (TLS)", RFC 4279, December Transport Layer Security (TLS)", RFC 4279, December 2005.
2005.
[TLS1.0] Dierks, T., and C. Allen, "The TLS Protocol, Version 1.0", [TLS1.0] Dierks, T., and C. Allen, "The TLS Protocol, Version 1.0",
RFC 2246, January 1999. RFC 2246, January 1999.
[TLS1.1] Dierks, T., and E. Rescorla, "The TLS Protocol, Version [TLS1.1] Dierks, T., and E. Rescorla, "The TLS Protocol, Version
1.1", RFC 4346, April, 2006. 1.1", RFC 4346, April, 2006.
[X501] ITU-T Recommendation X.501: Information Technology - Open [X501] ITU-T Recommendation X.501: Information Technology - Open
Systems Interconnection - The Directory: Models, 1993. Systems Interconnection - The Directory: Models, 1993.
[XDR] Eisler, M., "External Data Representation Standard", RFC [XDR] Eisler, M., "External Data Representation Standard", RFC
4506, May 2006. 4506, May 2006.
Credits Credits
Working Group Chairs Working Group Chairs
Eric Rescorla Eric Rescorla
EMail: ekr@networkresonance.com EMail: ekr@networkresonance.com
Pasi Eronen Pasi Eronen
pasi.eronen@nokia.com pasi.eronen@nokia.com
Editors Editors
Tim Dierks Eric Rescorla Tim Dierks Eric Rescorla
Independent Network Resonance, Inc. Independent Network Resonance, Inc.
skipping to change at page 99, line ? skipping to change at page 97, line 38
Independent Consultant Independent Consultant
EMail: david.hopwood@blueyonder.co.uk EMail: david.hopwood@blueyonder.co.uk
Phil Karlton (co-author of SSLv3) Phil Karlton (co-author of SSLv3)
Paul Kocher (co-author of SSLv3) Paul Kocher (co-author of SSLv3)
Cryptography Research Cryptography Research
paul@cryptography.com paul@cryptography.com
Hugo Krawczyk Hugo Krawczyk
Technion Israel Institute of Technology IBM
hugo@ee.technion.ac.il hugo@ee.technion.ac.il
Jan Mikkelsen Jan Mikkelsen
Transactionware Transactionware
EMail: janm@transactionware.com EMail: janm@transactionware.com
Magnus Nystrom Magnus Nystrom
RSA Security RSA Security
EMail: magnus@rsasecurity.com EMail: magnus@rsasecurity.com
Robert Relyea Robert Relyea
Netscape Communications Netscape Communications
relyea@netscape.com relyea@netscape.com
Jim Roskind Jim Roskind
Netscape Communications Netscape Communications
jar@netscape.com jar@netscape.com
Michael Sabin Michael Sabin
Dan Simon Dan Simon
Microsoft, Inc. Microsoft, Inc.
dansimon@microsoft.com dansimon@microsoft.com
skipping to change at page 99, line ? skipping to change at page 98, line 28
EMail: timothy.wright@vodafone.com EMail: timothy.wright@vodafone.com
Comments Comments
The discussion list for the IETF TLS working group is located at the The discussion list for the IETF TLS working group is located at the
e-mail address <tls@ietf.org>. Information on the group and e-mail address <tls@ietf.org>. Information on the group and
information on how to subscribe to the list is at information on how to subscribe to the list is at
<https://www1.ietf.org/mailman/listinfo/tls> <https://www1.ietf.org/mailman/listinfo/tls>
Archives of the list can be found at: Archives of the list can be found at:
<http://www.ietf.org/mail-archive/web/tls/current/index.html> <http://www.ietf.org/mail-archive/web/tls/current/index.html>
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 End of changes. 496 change blocks. 
1814 lines changed or deleted 1849 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/