< draft-eastlake-dnsext-cookies-02.txt   draft-eastlake-dnsext-cookies-03.txt >
INTERNET-DRAFT Donald E. Eastlake 3rd INTERNET-DRAFT Donald E. Eastlake 3rd
Intended Status: Proposed Standard Motorola Laboratories Intended Status: Proposed Standard Motorola Laboratories
Expires: February 2008 August 2007 Expires: August 2008 February 25, 2008
Domain Name System (DNS) Cookies Domain Name System (DNS) Cookies
------ ---- ------ ----- -------
<draft-eastlake-dnsext-cookies-02.txt> <draft-eastlake-dnsext-cookies-03.txt>
Status of This Document Status of This Document
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.
This draft is intended to be become a Proposed Standard RFC. This draft is intended to be become a Proposed Standard RFC.
Distribution of this document is unlimited. Comments should be sent Distribution of this document is unlimited. Comments should be sent
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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/1id-abstracts.html http://www.ietf.org/1id-abstracts.html
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
Abstract Abstract
DNS cookies are a light-weight DNS transaction security mechanism. DNS cookies are a light-weight DNS transaction security mechanism
They provides limited protection to DNS servers and resolvers against designed for incremental deployment. They provide limited protection
a variety of increasingly common denial-of-service and cache to DNS servers and resolvers against a variety of increasingly common
poisoning or forgery attacks by off-path attackers. denial-of-service and cache poisoning or forgery attacks by off-path
attackers. DNS Cookies are tolerant of NAT, NAT-PT, and Anycast.
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
Table of Contents Table of Contents
Status of This Document....................................1 Status of This Document....................................1
Abstract...................................................1 Abstract...................................................1
Table of Contents..........................................2 Table of Contents..........................................2
1. Introduction............................................3 1. Introduction............................................3
1.1 Contents of This Document..............................3 1.1 Contents of This Document..............................3
1.2 Definitions............................................3 1.2 Definitions............................................4
2. Threats Considered......................................5 2. Threats Considered......................................5
2.1 Denial-of-Service Attacks..............................5 2.1 Denial-of-Service Attacks..............................5
2.1.1 DNS Server Denial-of-Service.........................5 2.1.1 DNS Server Denial-of-Service.........................5
2.1.2 Selected Host Denial-of-Service......................5 2.1.2 Selected Host Denial-of-Service......................5
2.2 Cache Poisoning and Answer Forgery Attacks.............6 2.2 Cache Poisoning and Answer Forgery Attacks.............6
3. Comments on Existing DNS Security.......................6 3. Comments on Existing DNS Security.......................6
3.1 Existing DNS Data Security.............................6 3.1 Existing DNS Data Security.............................6
3.2 DNS Message or Transaction Security....................7 3.2 DNS Message or Transaction Security....................7
3.3 Conclusions on Existing DNS Security...................7 3.3 Conclusions on Existing DNS Security...................7
4. The COOKIE OPT option...................................8 4. The COOKIE OPT option...................................8
4.1 Resolver Cookies.......................................8 4.1 Resolver Cookies.......................................8
4.2 Server Cookies.........................................9 4.2 Server Cookies.........................................9
5. DNS Cookie Policies and Implementation Requirements.....9 5. DNS Cookie Policies and Implementation Requirements.....9
5.1 Resolver Policies and Implementation..................10 5.1 Resolver Policies and Implementation..................10
5.2 Server Policies and Implementation....................10 5.2 Server Policies and Implementation....................11
5.3 Implementation Requirements...........................11 5.3 Implementation Requirements...........................11
6. NAT and AnyCast Considerations.........................11 6. NAT Considerations and AnyCast Server Considerations...12
7. IANA Considerations....................................14 7. Incremental Deployment.................................14
8. Security Considerations................................14
9. Normative References...................................15
10. Informative References................................15
Author's Address..........................................17 8. IANA Considerations....................................15
Copyright and Disclaimer..................................17 9. Security Considerations................................15
Additional IPR Provisions.................................17 10. Normative References..................................16
Expiration and File Name..................................18 11. Informative References................................16
Author's Address..........................................18
Copyright and Disclaimer..................................18
Additional IPR Provisions.................................18
Expiration and File Name..................................19
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1. Introduction 1. Introduction
The Domain Name System (DNS) provides a replicated distributed As with many core Internet protocols, the Domain Name System (DNS)
database which stores "resource records" (RRs) under hierarchical was designed at a time when the Internet had only a small pool of
domain names. DNS data is structured into CLASSes and zones which trusted users. As the Internet has exploded to a global information
can be independently maintained. See [STD13] and [RFC2181] utility, the DNS has increasingly been subject to abuse and been used
familiarity with which is assumed. as a vector for abuse.
As with many core Internet protocols, DNS was designed at a time when
the Internet had only a small pool of trusted users. As the Internet
has exploded to a global information utility the DNS has increasingly
been subject to abuse and been used as a vector for abuse.
This document describes DNS cookies, a light-weight DNS transaction This document describes DNS cookies, a light-weight DNS transaction
security mechanism specified as an OPT [RFC2671] option. They security mechanism specified as an OPT [RFC2671] option. This
provides limited protection to DNS servers and resolvers against a mechanism provides limited protection to DNS servers and resolvers
variety of increasingly common denial-of-service and cache poisoning against a variety of increasingly common denial-of-service and cache
forgery attacks by off-path attackers. poisoning forgery attacks by off-path attackers.
The DNS cookies mechanism is designed with a default mode which
supports incremental deployment. If only one party to a DNS
transaction supports the mechanism, it does not interfere or provide
a benefit, but, if both support it, the additional security provided
is automatically available for that and subsequent transactions.
The DNS cookies mechanism is compatible with and can be used in
conjunction with other DNS transaction forgery resistance measures
such as those in [forgery].
The DNS cookies mechanism is designed to work in the presence of NAT
and NAT-PT boxes and guidance is provided herein on supporting the
DNS cookies mechanism in anycast servers.
1.1 Contents of This Document 1.1 Contents of This Document
In Section 2, we discuss the threats against which DNS cookies In Section 2, we discuss the threats against which the DNS cookie
provides some protection. mechanism provides some protection.
Section 3 describes existing DNS security mechanisms and why they are Section 3 describes existing DNS security mechanisms and why they are
not adequate substitutes for DNS cookies. not adequate substitutes for DNS cookies.
Section 4 describes the COOKIE OPT option including recommendations Section 4 describes the COOKIE OPT option including recommendations
for calculating Resolver and Server Cookies. for calculating Resolver and Server Cookies.
Section 5 describes the processing of COOKIE OPT options by resolvers Section 5 describes the processing of COOKIE OPT options by resolvers
and server and policies for such processing. and server and policies for such processing.
Section 6 discusses some NAT and anycast related DNS Cookies design Section 6 discusses some NAT and anycast related DNS Cookies design
considerations. considerations.
Sections 7 and 8 describe IANA and Security Considerations. Section 7 discusses incremental deployment considerations.
Sections 8 and 9 describe IANA and Security Considerations.
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1.2 Definitions 1.2 Definitions
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 [RFC2119]. document are to be interpreted as described in [RFC2119].
An "off-path attacker", for a particular DNS resolver and server, is An "off-path attacker", for a particular DNS resolver and server, is
defined as an attacker which cannot observe the legitimate plain text defined as an attacker which cannot observe the legitimate plain text
INTERNET-DRAFT DNS Cookies
DNS requests and responses between that resolver and server. DNS requests and responses between that resolver and server.
"Soft state" indicates information learned or derived by a host which "Soft state" indicates information learned or derived by a host which
may be discarded when indicated by the policies of that host but can may be discarded when indicated by the policies of that host but can
be later re-instantiated if needed. For example, it could be be later re-instantiated if needed. For example, it could be
discarded after a period of time or when storage for caching such discarded after a period of time or when storage for caching such
data becomes full. If operations requiring that soft state continue data becomes full. If operations requiring that soft state continue
after it has been discarded, it will be automatically re-generated, after it has been discarded, it will be automatically re-generated,
albeit at some cost. albeit at some cost.
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DNS requests that are accepted cause work on the part of DNS servers. DNS requests that are accepted cause work on the part of DNS servers.
This is particularly true for recursive servers which may issue one This is particularly true for recursive servers which may issue one
or more requests and process the responses thereto in order to or more requests and process the responses thereto in order to
determine their response to the initial query. And the situation is determine their response to the initial query. And the situation is
even worse for recursive servers implementing DNSSEC [RFC4033], even worse for recursive servers implementing DNSSEC [RFC4033],
[RFC4034], [RFC4035] because they may be induced to perform [RFC4034], [RFC4035] because they may be induced to perform
burdensome public key cryptographic computations in attempts to burdensome public key cryptographic computations in attempts to
verify the authenticity of data they retrieve while trying to answer verify the authenticity of data they retrieve while trying to answer
the request. the request.
The computational or communications burden cause by such requests is The computational or communications burden caused by such requests
not dependent on a forged IP source address, but the use of such may not dependent on a forged IP source address, but the use of such
addresses makes addresses makes
+ the source of the requests causing the denial-of-service attack to + the source of the requests causing the denial-of-service attack to
be harder to find and be harder to find and
+ administrative restriction of the IP addresses from which such + administrative restriction of the IP addresses from which such
requests should be honored harder to accurately specify. requests should be honored harder or impossible to specify.
Use of DNS cookies almost always enables a server to reject forged Use of DNS cookies almost always enables a server to reject forged
queries from an off path attacker with relative ease, certainly queries from an off path attacker with relative ease, certainly
before any recursive queries or public key cryptographic operations before any recursive queries or public key cryptographic operations
are performed. are performed.
2.1.2 Selected Host Denial-of-Service 2.1.2 Selected Host Denial-of-Service
A request with a forged IP address generally causes a response to be A request with a forged IP address generally causes a response to be
sent to that forged IP address. Thus the forging of many such sent to that forged IP address. Thus the forging of many such
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traffic being sent to the forged IP address to interfere with service traffic being sent to the forged IP address to interfere with service
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
to the host at the IP address. Furthermore, it is generally easy in to the host at the IP address. Furthermore, it is generally easy in
the DNS to create short requests that produce much longer responses. the DNS to create short requests that produce much longer responses.
Thus a DNS server can be used as not only a way to obscure the true Thus a DNS server can be used as not only a way to obscure the true
source of an attack but as a traffic amplifier to make the attack source of an attack but as a traffic amplifier to make the attack
more effective. more effective.
Use of DNS cookies severely limits the traffic amplification that can Use of the DNS Cookies mechanism severely limits the traffic
be obtained by attackers off path for the server and the attacked amplification that can be obtained by attackers off path for the
host. Enforced DNS cookies would make it hard for an off path server and the attacked host. Enforced DNS cookies would make it hard
attacker to cause any more than a brief error response to be send to for an off path attacker to cause any more than a brief error
a forged IP address. Furthermore, DNS cookies make it more effective response to be sent to a forged IP address. Furthermore, DNS cookies
to implement a rate limiting scheme for bad DNS cookie error make it more effective to implement a rate limiting scheme for bad
responses from the server. Such a scheme would further restrict DNS cookie error responses from the server. Such a scheme would
selected host denial-of-service traffic from that server. further restrict selected host denial-of-service traffic from that
server.
2.2 Cache Poisoning and Answer Forgery Attacks 2.2 Cache Poisoning and Answer Forgery Attacks
The form of the cache poisoning attacks considered is to send forged The form of the cache poisoning attacks considered is to send forged
replies to a resolver. Modern network speeds for well connected hosts replies to a resolver. Modern network speeds for well connected hosts
are such that, by forging replies from the IP addresses of heavily are such that, by forging replies from the IP addresses of heavily
used DNS servers and for popular names to a heavily used resolver, used DNS servers for popular names to a heavily used resolver, there
there can be an unacceptably high probability of randomly coming up can be an unacceptably high probability of randomly coming up with a
with a reply that will be accepted and cause false DNS information to reply that will be accepted and cause false DNS information to be
be cached by that resolver. This can be used to facilitate phishing cached by that resolver. This can be used to facilitate phishing
attacks and other diversion of legitimate traffic to a compromised or attacks and other diversion of legitimate traffic to a compromised or
malicious host such as a web server. malicious host such as a web server.
In a similar manner it is possible, under some circumstances to send
forged answers that will be accepted by resolvers with an
unacceptably high probability.
3. Comments on Existing DNS Security 3. Comments on Existing DNS Security
Two forms of security have been added to DNS, data security and Two forms of security have been added to DNS, data security and
message or transaction security. message or transaction security.
3.1 Existing DNS Data Security 3.1 Existing DNS Data Security
DNS data security is one part of DNSSEC and is described in DNS data security is one part of DNSSEC and is described in
[RFC4033], [RFC4034], and [RFC4035]. It provides data origin [RFC4033], [RFC4034], and [RFC4035]. It provides data origin
authentication and authenticated denial of existence. It is being authentication and authenticated denial of existence. It is being
deployed slowly and, in any case, can make some denial-of-service deployed slowly and, in any case, can make some denial-of-service
attacks worse because of the high cryptographic computational load it attacks worse because of the high cryptographic computational load it
can require and the increased size in DNS packets that it tends to can require and the increased size in DNS packets that it tends to
produce.
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
produce.
3.2 DNS Message or Transaction Security 3.2 DNS Message or Transaction Security
The second form of security which has been added to DNS provides The second form of security which has been added to DNS provides
"transaction" security through TSIG [RFC2845] or SIG(0) [RFC2931]. "transaction" security through TSIG [RFC2845] or SIG(0) [RFC2931].
TSIG could provide near perfect protection against the attacks for TSIG could provide near perfect protection against the attacks for
which DNS cookies provide weak and incomplete protection; however, which the DNS Cookies mechanism provide weak and incomplete
TSIG is hard to deploy in the general Internet because of the burden protection; however, TSIG is hard to deploy in the general Internet
it imposes of pre-agreement and key distribution between pairs of because of the burden it imposes of pre-agreement and key
resolvers and servers and because it requires time synchronization distribution between pairs of resolvers and servers and because it
between resolver and server. requires time synchronization between resolver and server.
TKEY [RFC2930] can solve the problem of key distribution for TSIG but TKEY [RFC2930] can solve the problem of key distribution for TSIG but
some modes of TKEY impose substantial cryptographic computations some modes of TKEY impose a substantial cryptographic computation
loads and can be dependent on the deployment of DNSSEC. loads and can be dependent on the deployment of DNSSEC.
SIG(0) provides less denial of service protection than TSIG or, in SIG(0) provides less denial of service protection than TSIG or, in
one way, even DNS cookies, because it does not authenticate requests, one way, even DNS cookies, because it does not authenticate requests,
only complete transactions. In any case, it also depends on the only complete transactions. In any case, it also depends on the
deployment of DNSSEC and requires computationally burdensome public deployment of DNSSEC and requires computationally burdensome public
key cryptographic operations. key cryptographic operations.
3.3 Conclusions on Existing DNS Security 3.3 Conclusions on Existing DNS Security
Thus, none of the previous forms of DNS security are a suitable Thus, none of the previous forms of DNS security are a suitable
substitute for DNS cookies, which provide light weight message substitute for the DNS Cookies mechanism, which provide light weight
authentication of DNS requests and responses with no requirement for message authentication of DNS requests and responses with no
pre-configuration. requirement for pre-configuration.
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
4. The COOKIE OPT option 4. The COOKIE OPT option
COOKIE is an OPT RR [RFC2671] option that can be included once in the COOKIE is an OPT RR [RFC2671] option that can be included no more
RDATA portion of an OPT RR in DNS requests and responses. than once in the RDATA portion of an OPT RR in DNS requests and
responses.
The option is encoded into 22 bytes as shown below. The option is encoded into 22 bytes as shown below.
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION-CODE TBD | OPTION-LENGTH = 18 | | OPTION-CODE = {TBD} | OPTION-LENGTH = 18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Resolver Cookie upper half |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Resolver Cookie lower half |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server Cookie upper half | | |
+- Resolver Cookie -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server Cookie lower half | | |
+-- Server Cookie -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Code | | Error Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Resolver and Server Cookies are stored in network byte order and The 64-bit Resolver and Server Cookies are stored in network byte
are determined as described below. order and are determined as described below.
The Error Code field MUST be zero in requests and in responses unless The Error Code field MUST be zero in requests and in responses unless
the response is communicating a DNS cookie error. Three values are the response is communicating a DNS cookie error. Three values are
specified in this document for Error Code: NOCOOKIE and BADCOOKIE specified in this document for Error Code: NOCOOKIE and BADCOOKIE
which occur with a Refused RCODE in the DNS response header, and which occur with a Refused RCODE in the DNS response header, and
MANYCOOKIE which occurs with a FormErr RCODE in the DNS header. More MANYCOOKIE which occurs with a FormErr RCODE in the DNS header. More
information on the generation of error response appears in Section 5 information on the generation of error responses appears in Section 5
below. below.
4.1 Resolver Cookies 4.1 Resolver Cookies
The Resolver Cookie, when it occurs in an OPT in a DNS response, is The Resolver Cookie, when it occurs in an OPT in a DNS response, is
intended to weakly assure the resolver that the response came from a intended to weakly assure the resolver that the response came from a
server at the indicated source IP address. server at the indicated source IP address.
Servers remember the Resolver Cookie that appears in a query long Servers remember the Resolver Cookie that appears in a query long
enough to use it in the construction of the COOKIE OPT option in the enough to use it in the construction of the COOKIE OPT option in the
corresponding response if such a COOKIE OPT option is included in corresponding response if such a COOKIE OPT option is included in
that response. that response.
The Resolver Cookie SHOULD be a pseudo-random function of the server The Resolver Cookie SHOULD be a pseudo-random function of the server
IP address and a secret quantity known only to the resolver. This IP address and a secret quantity known only to the resolver. This
resolver secret SHOULD have 64 bits of entropy [RFC4086] and MAY be
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
resolver secret SHOULD have 64 bits of entropy [RFC4086] and MAY be
changed periodically. The RECOMMENDED method is the HMAC-SHA1-64 changed periodically. The RECOMMENDED method is the HMAC-SHA1-64
[RFC1321], [RFC2104] of the server IP address and the resolver [RFC1321] [RFC2104] of the server IP address and the resolver secret.
secret. That is That is
Resolver Cookie = Truncate-64 Resolver Cookie = Truncate-64
( HMAC-SHA1 ( Server IP Address, Resolver Secret ) ) ( HMAC-SHA1 ( Server IP Address, Resolver Secret ) )
where Truncate-64 takes the first 64 bits. A resolver MUST NOT use where Truncate-64 takes the first 64 bits. A resolver MUST NOT use
the same Resolver Cookie value for queries to all servers. the same Resolver Cookie value for queries to all servers.
4.2 Server Cookies 4.2 Server Cookies
The Server Cookie, when it occurs in a COOKIE OPT option in a query, The Server Cookie, when it occurs in a COOKIE OPT option in a query,
is intended to weakly assure the server that the query legitimately is intended to weakly assure the server that the query legitimately
came from a resolver at the indicated source IP address that is using came from a resolver at the indicated source IP address that is using
that Resolver Cookie. that Resolver Cookie.
Resolvers learn Server Cookies and retain them as soft state Resolvers learn Server Cookies and retain them as soft state
associated with the server IP address. They learn them from the associated with the server IP address. They learn them from the
Server Cookie that appears in the COOKIE OPT option of a reply that Server Cookie that appears in the COOKIE OPT option of a reply if
also has the correct Resolver Cookie, even if that reply is an error that reply has the correct Resolver Cookie, even if that reply is an
message. error message.
The Server Cookie SHOULD be a pseudo-random function of the request The Server Cookie SHOULD be a pseudo-random function of the request
source IP address, the request Resolver Cookie, and a secret quantity source IP address, the request Resolver Cookie, and a secret quantity
known only to the server. This server secret SHOULD have 64 bits of known only to the server. This server secret SHOULD have 64 bits of
entropy [RFC4086] and SHOULD be changed periodically such as daily. entropy [RFC4086] and SHOULD be changed periodically such as daily.
The RECOMMENDED method is the HMAC-SHA1-64 [RFC1321], [RFC2104] of The RECOMMENDED method is the HMAC-SHA1-64 [RFC1321], [RFC2104] of
the request IP address, the Resolver Cookie, and the server secret. the request IP address, the Resolver Cookie, and the server secret.
That is That is
Server Cookie = Truncate-64 ( HMAC-SHA1 ( Server Cookie = Truncate-64 ( HMAC-SHA1 (
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concatenation. concatenation.
A server MUST NOT use the same Server Cookie value for responses to A server MUST NOT use the same Server Cookie value for responses to
all resolvers. all resolvers.
5. DNS Cookie Policies and Implementation Requirements 5. DNS Cookie Policies and Implementation Requirements
DNS resolvers and servers will adopt one of various policies DNS resolvers and servers will adopt one of various policies
regarding cookies. These policies SHOULD be logically settable on a regarding cookies. These policies SHOULD be logically settable on a
per server IP address basis for resolvers and a per resolver ( IP per server IP address basis for resolvers and a per resolver ( IP
address, Resolver Cookie ) pair for servers. Thus a resolver can
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address, Resolver Cookie ) pair for servers. Thus a resolver can
have different policies for different servers, based on the server IP have different policies for different servers, based on the server IP
address. And a server can have different policies for different address. And a server can have different policies for different
resolvers, based on the resolver IP address and Resolver Cookie. Of resolvers, based on the resolver IP address and Resolver Cookie. Of
course, the actual implementation of setting these policies may be course, the actual implementation of setting these policies may be
for blocks or classes of values or use sparse array techniques. for blocks or classes of values or use sparse array techniques or the
like.
The policy for each value is either "Disabled", "Enabled", or The policy for each value is either "Disabled", "Enabled", or
"Enforced" as described below. "Enforced" as described below.
5.1 Resolver Policies and Implementation 5.1 Resolver Policies and Implementation
A resolver will logically have one of the following three policies A resolver will logically have one of the following three modes of
for each DNS server as distinguished by server IP Address. operation or "policies" for each DNS server as distinguished by
server IP Address.
Disabled: Disabled:
Never include a COOKIE OPT option in requests. Never include a COOKIE OPT option in requests.
Ignore COOKIE OPT options in responses. Ignore COOKIE OPT options in responses.
Enabled: Enabled:
Always include a COOKIE OPT option in requests. If a cached Server Always include a COOKIE OPT option in requests. If a cached Server
Cookie for the server is not available, the Server Cookie field Cookie for the server is not available, the Server Cookie field
can be set to any value. can be set to any value.
Normally process responses without a COOKIE OPT option. Normally process responses without a COOKIE OPT option.
Silently ignore responses with more than one COOKIE OPT option. Silently ignore responses with more than one COOKIE OPT option.
Silently ignore responses with one COOKIE OPT option if it has an Silently ignore responses with one COOKIE OPT option if it has an
incorrect Resolver Cookie value. incorrect Resolver Cookie value.
On receipt of a response with one COOKIE OPT option and it having On receipt of a response with one COOKIE OPT option carrying the
the correct Resolver Cookie value (even if it is a BADCOOKIE correct Resolver Cookie value (even if it is a BADCOOKIE error
error response), perform normal response processing, including response), the DNS client performs normal response processing,
caching the received Server Cookie and MUST change to the including caching the received Server Cookie, and it MUST
Enforced policy for DNS requests to that DNS server IP address. change to the Enforced policy for DNS requests to that DNS
This policy change SHOULD be treated as soft state with the server IP address. This policy change SHOULD be treated as soft
same discard policy as the Server Cookie value for that server. state with the same timeout strategy as the Server Cookie value
On discarding that state information, the policy for that DNS for that server. On timeout of that state information, the
server reverts to Enabled. policy for that DNS server reverts to Enabled.
Enforced: Enforced:
Always include a COOKIE OPT option in requests. Always include a COOKIE OPT option in requests.
Silently ignore all responses that do not include exactly one Silently ignore all responses that do not include exactly one
COOKIE OPT option having the correct Resolver Cookie value. COOKIE OPT option having the correct Resolver Cookie value.
5.2 Server Policies and Implementation INTERNET-DRAFT DNS Cookies
A server will logically have one of the following three policies for 5.2 Server Policies and Implementation
each DNS resolver as distinguished by resolver IP Address and
Resolver Cookie.
INTERNET-DRAFT DNS Cookies A server will logically have one of the following three modes of
operation or "policies" for each DNS resolver as distinguished by
resolver IP Address and Resolver Cookie.
Disabled: Disabled:
Ignore COOKIE OPT options in requests. Ignore COOKIE OPT options in requests.
Never include a COOKIE OPT option in responses. Never include a COOKIE OPT option in responses.
Enabled: Enabled:
Always include a COOKIE OPT option in responses. Always include a COOKIE OPT option in responses.
Normally process requests without a COOKIE OPT option. Normally process requests without a COOKIE OPT option.
Ignore, other than sending a MANYCOOKIE error response, any Ignore, other than sending a MANYCOOKIE error response, any
request with more than one COOKIE OPT option. request with more than one COOKIE OPT option.
Ignore, other than sending a BADCOOKIE error response, any query Ignore, other than sending a BADCOOKIE error response, any query
with one COOKIE OPT option if it has an incorrect Server with one COOKIE OPT option if it has an incorrect Server
Cookie. Cookie.
On receipt of a request with a COOKIE OPT option having the On receipt of a request with a COOKIE OPT option carrying the
correct Server Cookie value, perform normal request processing correct Server Cookie value, the DNS server performs normal
and SHOULD adopt the Enforced policy for DNS requests from that request processing and it SHOULD switch to the Enforced policy
resolver IP address with that Resolver Cookie in the request. for DNS requests from that resolver IP address with that
This policy change for that resolver SHOULD be treated as soft Resolver Cookie in the request. This policy change for that
state. On discarding that state information, the policy for resolver SHOULD be treated as soft state. On timing out that
that resolver IP and Resolver Cookie pair reverts to enabled. state information, the policy for that resolver IP and Resolver
Cookie pair reverts to Enabled.
Enforced: Enforced:
Always include a COOKIE OPT option in responses. Always include a COOKIE OPT option in responses.
Ignore requests without a COOKIE OPT option or with more than one Ignore requests without a COOKIE OPT option or with more than one
COOKIE OPT option, other than sending a NOCOOKIE or MANYCOOKIE COOKIE OPT option, other than returning a NOCOOKIE or
error respectively. MANYCOOKIE error respectively.
Ignore requests with one COOKIE OPT option if they have an Ignore requests with one COOKIE OPT option if they have an
incorrect Server Cookie, other than sending a BADCOOKIE error incorrect Server Cookie, other than returning a BADCOOKIE error
message. message.
If a request has one COOKIE OPT option with a correct Server If a request has one COOKIE OPT option with a correct Server
Cookie, perform normal processing of the request. Cookie, perform normal processing of the request.
5.3 Implementation Requirements 5.3 Implementation Requirements
DNS resolvers and servers SHOULD implement DNS cookies. DNS resolvers and servers SHOULD implement DNS cookies.
DNS resolvers SHOULD operate in and be shipped so as to default to DNS resolvers SHOULD operate in and be shipped so as to default to
the Enabled or Enforced mode for all servers. the Enabled or Enforced mode for all servers.
DNS servers SHOULD operate in and be shipped so as to default to the DNS servers SHOULD operate in and be shipped so as to default to the
Enabled or Enforced mode for all resolvers they are willing to Enabled or Enforced mode for all resolvers they are willing to
service. service.
6. NAT and AnyCast Considerations
[The section below is too confusing and needs to be reworded...]
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
6. NAT Considerations and AnyCast Server Considerations
In the Classic Internet, DNS Cookies could simply be a pseudo-random In the Classic Internet, DNS Cookies could simply be a pseudo-random
function of the resolver IP address and a sever secret or the server function of the resolver IP address and a sever secret or the server
IP address and a resolver secret. You would want to compute the IP address and a resolver secret. You would want to compute the
Server Cookie that way, so a resolver could cache its Server Cookie Server Cookie that way, so a resolver could cache its Server Cookie
for a particular server for an indefinitely amount of time and the for a particular server for an indefinitely amount of time and the
server could easily regenerate and check it. You could consider the server could easily regenerate and check it. You could consider the
Resolver Cookie to be a resolver signature over the server IP address Resolver Cookie to be a resolver signature over the server IP address
which the resolver checks in responses and you could extend this which the resolver checks in responses and you could extend this
signature to cover the request ID, for example. signature to cover the request ID, for example.
But we have this reality called NAT [RFC3022], Network Address But we have this reality called NAT [RFC3022], Network Address
Translation (including therein for the purposes of this document NAT- Translation (including, for the purposes of this document, NAT-PT
PT [RFC2766], Network Address and Protocol Translation). There is no [RFC2766], Network Address and Protocol Translation, which has been
problem with DNS transactions between resolvers and servers behind a declared Historic [RFC4966]). There is no problem with DNS
NAT box using local IP addresses. Nor is there a problem with NAT transactions between resolvers and servers behind a NAT box using
translation of internal addresses to external addresses or local IP addresses. Nor is there a problem with NAT translation of
translations between IPv4 and IPv6 addresses, as long as the address internal addresses to external addresses or translations between IPv4
mapping is relatively stable. Should an internal resolver being and IPv6 addresses, as long as the address mapping is relatively
mapped to a particular external IP address change occasionally, the stable. Should an internal resolver being mapped to a particular
disruption is no more than when a resolver rolls-over its DNS COOKIE external IP address change occasionally, the disruption is no more
secret. And normally external access to a DNS server behind a NAT box than when a resolver rolls-over its DNS COOKIE secret. And normally
is handled by a fixed mapping which forwards externally received DNS external access to a DNS server behind a NAT box is handled by a
requests to a specific host. fixed mapping which forwards externally received DNS requests to a
specific host.
However, NAT devices sometimes also map ports. This can cause However, NAT devices sometimes also map ports. This can cause
multiple DNS requests and responses from multiple internal hosts to multiple DNS requests and responses from multiple internal hosts to
be simultaneously mapped to a smaller number of external IP be simultaneously mapped to a smaller number of external IP
addresses, frequently one. There could be many resolvers behind a addresses, frequently one. There could be many resolvers behind a
NAT box that appear to come from the same source IP address to a NAT box that appear to come from the same source IP address to a
server outside that NAT box.. If one of these were an attacker server outside that NAT box. If one of these were an attacker (think
(think Zombie or Botnet), that behind-NAT attacker could get the Zombie or Botnet), that behind-NAT attacker could get the Server
Server Cookie for some server for the outgoing IP address by just Cookie for some server for the outgoing IP address by just making
making some random request to that server. It could then include that some random request to that server. It could then include that Server
Server Cookie in the COOKIE RR of requests to the server with the Cookie in the COOKIE RR of requests to the server with the forged
forged IP address of the local IP address of some other host and/or local IP address of some other host and/or resolver behind the NAT
resolver behind the NAT box. (Attacker possession of this Server box. (Attacker possession of this Server Cookie will not help in
Cookie will not help in forging responses to cause cache poisoning as forging responses to cause cache poisoning as such responses are
such responses are protected by the required Resolver Cookie.) protected by the required Resolver Cookie.)
To fix this potential defect, it is necessary to distinguish To fix this potential defect, it is necessary to distinguish
different resolvers behind a NAT box from the point of view of the different resolvers behind a NAT box from the point of view of the
server. It is for this reason that the Server Cookie is specified as server. It is for this reason that the Server Cookie is specified as
a pseudo-random function of both the request source IP address and a pseudo-random function of both the request source IP address and
the Resolver Cookie. From this inclusion of the Resolver Cookie in the Resolver Cookie. From this inclusion of the Resolver Cookie in
the calculation of the Server Cookie, it follows that a stable the calculation of the Server Cookie, it follows that a stable
Resolver Cookie, for any particular server, is needed. If, for Resolver Cookie, for any particular server, is needed. If, for
example, the request ID was included in the calculation of the example, the request ID was included in the calculation of the
Resolver Cookie, it would normally change with each query to a
particular server. This would mean that each query would have to be
sent twice: first to learn the new Server Cookie based on this new
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
Resolver Cookie, it would normally change with each query to a
particular server. This would mean that each query would have to be
sent twice: first to learn the new Server Cookie based on this new
Resolver Cookie based on the new ID and then again using this new Resolver Cookie based on the new ID and then again using this new
Resolver Cookie to actually get an answer. Thus the input to the Resolver Cookie to actually get an answer. Thus the input to the
Resolver Cookie computation must be limited to the server IP address Resolver Cookie computation must be limited to the server IP address
and one or more things that change slowly such as the resolver and one or more things that change slowly such as the resolver
secret. secret.
In principle, there could be a similar problem for servers, not In principle, there could be a similar problem for servers, not
particularly due to NAT but due to mechanisms like anycast which may particularly due to NAT but due to mechanisms like anycast which may
cause queries to a DNS server at an IP address to be delivered to any cause queries to a DNS server at an IP address to be delivered to any
one of several machines. (External queries to a DNS server behind a one of several machines. (External queries to a DNS server behind a
NAT box usually occur via port forwarding such that all such queries NAT box usually occur via port forwarding such that all such queries
go to one host.) However, it is impossible to solve this the way the go to one host.) However, it is impossible to solve this the way the
similar problem was solved for NATed resolvers; if the Server Cookie similar problem was solved for NATed resolvers; if the Server Cookie
was included in the calculation of the Resolver Cookie the same way was included in the calculation of the Resolver Cookie the same way
the Resolver Cookie is included in the Server Cookie, you would just the Resolver Cookie is included in the Server Cookie, you would just
get an almost infinite series of BADCOOKIE errors as a query was get an almost infinite series of BADCOOKIE errors as a query was
repeatedly retried. repeatedly retried.
For server accessed via anycast or similar mechanisms to successfully For servers accessed via anycast to successfully support DNS COOKIES,
support DNS COOKIES, the server clones must either all use the same the server clones must either all use the same server secret or the
server secret or the mechanism that distributes queries to them must mechanism that distributes queries to them must cause the queries
cause the queries from a particular resolver to go to a particular from a particular resolver to go to a particular server for a
server for a sufficiently long period of time that extra queries due sufficiently long period of time that extra queries due to changes in
to changes in Server Cookie resulting from accessing different server Server Cookie resulting from accessing different server machines are
machines are not unduly burdensome. When such anycast accessed not unduly burdensome. When such anycast accessed servers act as
servers act as recursive servers or otherwise act as resolvers they recursive servers or otherwise act as resolvers they normally use a
normally use a different unique address to source their queries and different unique address to source their queries and avoid confusion
avoid confusion in the delivery of responses. in the delivery of responses.
For simplicity, it is RECOMMENDED that the same server secret be used For simplicity, it is RECOMMENDED that the same server secret be used
by each set of anycast servers. by each DNS server in a set of anycast servers.
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
7. IANA Considerations 7. Incremental Deployment
The DNS cookies mechanism is designed for incremental deployment and
to complement the orthogonal techniques in [forgery]. Either or both
techniques can be deployed independently at each DNS server and
resolver.
In particular, a DNS server or resolver that implements the DNS
cookies mechanism and is in the Enabled mode will interoperate
successfully with a DNS resolver or server that does not implement
this mechanism although, of course, in this case it will not get the
benefit of the mechanism. When such a server or resolver
interoperates with a resolver or server which also implements the DNS
cookies mechanism, this is recognized and, for that transaction
partner, it enters the Enforced mode and gets the full benefit of the
DNS cookies mechanism until this soft state times out and it reverts
to Enabled.
INTERNET-DRAFT DNS Cookies
8. IANA Considerations
IANA will allocate the following code points: IANA will allocate the following code points:
The OPT option value for COOKIE is <TBD>. The OPT option value for COOKIE is <TBD>.
Three new RCODES are assigned values as listed below: Three new RCODES are assigned values as listed below:
NOCOOKIE is assigned the value (<TBD>, 23 suggested). NOCOOKIE is assigned the value ({TBD}, 23 suggested).
BADCOOKIE is assigned the value (<TBD>, 24 suggested). BADCOOKIE is assigned the value ({TBD}, 24 suggested).
MANYCOOKIE is assigned the value (<TBD>, 25 suggested). MANYCOOKIE is assigned the value ({TBD}, 25 suggested).
8. Security Considerations 9. Security Considerations
DNS Cookies provide a weak form of authentication of DNS requests and DNS Cookies provide a weak form of authentication of DNS requests and
responses. In particular, they provide no protection at all against responses. In particular, they provide no protection at all against
"on-path" adversaries; that is, they provide no protection against "on-path" adversaries; that is, they provide no protection against
any adversary which can observe the plain text DNS traffic, such as any adversary which can observe the plain text DNS traffic, such as
an on-path router, bridge, or any device on an on-path shared link an on-path router, bridge, or any device on an on-path shared link
(unless the DNS traffic in question on that path is appropriately (unless the DNS traffic in question on that path is appropriately
encrypted). encrypted).
For example, if a host is connected via an unsecured IEEE 802.11 link For example, if a host is connected via an unsecured IEEE 802.11 link
(Wi-Fi), any device in the vicinity that could receive and decode the (Wi-Fi), any device in the vicinity that could receive and decode the
802.11 transmissions must be considered "on-path". On the other hand, 802.11 transmissions must be considered "on-path". On the other hand,
in a similar situation but one where 802.11i security is in a similar situation but one where 802.11 Robust Security (WPAv2)
appropriately deployed on the Wi-Fi network nodes, only the Access is appropriately deployed on the Wi-Fi network nodes, only the Access
Point via which the host is connecting is "on-path". Point via which the host is connecting is "on-path".
Despite these limitations, use of DNS Cookies on the global Internet Despite these limitations, use of DNS Cookies on the global Internet
is expected to provide a reduction in the available launch points for is expected to provide a reduction in the available launch points for
the traffic amplification and denial of service forgery attacks the traffic amplification and denial of service forgery attacks
described in Section 2 above. described in Section 2 above.
The recommended cryptographic algorithms for use in DNS Cookies is The recommended cryptographic algorithms for use in DNS Cookies is
HMAC-SHA1-64, that is, the HMAC scheme [RFC2104] using the SHA1 hash HMAC-SHA1-64, that is, the HMAC scheme [RFC2104] using the SHA1 hash
function [RFC3174] [RFC4634] with the HMAC output truncated to function [RFC3174] [RFC4634] with the HMAC output truncated to
64-bits. MD5 is now considered to be susceptible to collisions 64-bits. MD5 is now considered to be susceptible to collisions
attacks. Although this does not effect the security of HMAC-MD5, attacks. Although this does not effect the security of HMAC-MD5,
HMAC-SHA1 is stronger. HMAC-SHA1 is believed to be stronger.
In light of the weak plain-text token security provided by DNS In light of the weak plain-text token security provided by DNS
Cookies, stronger cryptography is probably not warranted and in many Cookies, stronger cryptography is probably not warranted and in many
cases it would be acceptable to use the weaker MD5 hash function cases it would be acceptable to use the weaker MD5 hash function
[RFC1321]. However, there is nothing wrong with using something [RFC1321]. However, there is nothing wrong with using something
stronger, for example, HMAC-SHA256-64 [RFC4634], assuming a DNS stronger, for example, HMAC-SHA256-64 [RFC4634], assuming a DNS
processor has adequate computational resources available. DNS processor has adequate computational resources available. DNS
processors that feel the need for somewhat stronger security without processors that feel the need for somewhat stronger security without
a significant increase in computational load should consider more a significant increase in computational load should consider more
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
frequent changes in their resolver and/or server secret; however, frequent changes in their resolver and/or server secret; however,
this does require more frequent generation of a cryptographically this does require more frequent generation of a cryptographically
strong random number [RFC4086] and a change in a server secret will strong random number [RFC4086] and a change in a server secret will
result in a number of initial BADCOOKIE rejected requests from result in a number of initial BADCOOKIE rejected requests from
resolvers caching their old Server Cookie. resolvers caching their old Server Cookie.
9. Normative References 10. Normative References
[RFC1321] - Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] - Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992. April 1992.
[RFC2104] - Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- [RFC2104] - Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February 1997. Hashing for Message Authentication", RFC 2104, February 1997.
[RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2181] - Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, July 1997.
[RFC2671] - Vixie, P., "Extension Mechanisms for DNS (EDNS0)", August [RFC2671] - Vixie, P., "Extension Mechanisms for DNS (EDNS0)", August
1999. 1999.
[RFC4086] - Eastlake, D., 3rd, Schiller, J., and S. Crocker, [RFC4086] - Eastlake, D., 3rd, Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005.
[STD13] 11. Informative References
Mockapetris, P., "Domain names - concepts and facilities", STD
13, RFC 1034, November 1987.
Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
10. Informative References [forgery] - "Measures for making DNS more resilient against forged
answers", Hubert, A. , R. van Mook, draft-ietf-dnsext-forgery-
resilience-01.txt, work in progress, July 2007.
[RFC2766] - Tsirtsis, G., P. Srisuresh, "Network Address Translation [RFC2766] - Tsirtsis, G., P. Srisuresh, "Network Address Translation
- Protocol Translation (NAT-PT)", February 2000. - Protocol Translation (NAT-PT)", February 2000.
[RFC2845] - Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B. [RFC2845] - Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS (TSIG)", Wellington, "Secret Key Transaction Authentication for DNS (TSIG)",
RFC 2845, May 2000. RFC 2845, May 2000.
[RFC2930] - Eastlake 3rd, D., "Secret Key Establishment for DNS (TKEY [RFC2930] - Eastlake 3rd, D., "Secret Key Establishment for DNS (TKEY
RR)", RFC 2930, September 2000. RR)", RFC 2930, September 2000.
[RFC2931] - Eastlake 3rd, D., "DNS Request and Transaction Signatures [RFC2931] - Eastlake 3rd, D., "DNS Request and Transaction Signatures
INTERNET-DRAFT DNS Cookies
( SIG(0)s )", RFC 2931, September 2000. ( SIG(0)s )", RFC 2931, September 2000.
[RFC3022] - Srisuresh, P. and K. Egevang, "Traditional IP Network [RFC3022] - Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January 2001. Address Translator (Traditional NAT)", RFC 3022, January 2001.
[RFC3174] - Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm [RFC3174] - Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm
INTERNET-DRAFT DNS Cookies
1 (SHA1)", RFC 3174, September 2001. 1 (SHA1)", RFC 3174, September 2001.
[RFC4033] - Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC 4033, March Rose, "DNS Security Introduction and Requirements", RFC 4033, March
2005. 2005.
[RFC4034] - Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", RFC 4034, Rose, "Resource Records for the DNS Security Extensions", RFC 4034,
March 2005. March 2005.
[RFC4035] - Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4035] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security Extensions", RFC Rose, "Protocol Modifications for the DNS Security Extensions", RFC
4035, March 2005. 4035, March 2005.
[RFC4634] - Eastlake, D. and T. Hansen, "US Secure Hash Algorithms [RFC4634] - Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA)", RFC 4634, July 2006. (SHA)", RFC 4634, July 2006.
[RFC4966] - Aoun, C. and E. Davies, "Reasons to Move the Network
Address Translator - Protocol Translator (NAT-PT) to Historic
Status", RFC 4966, July 2007.
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
Author's Address Author's Address
Donald E. Eastlake 3rd Donald E. Eastlake 3rd
Motorola Laboratories Motorola Laboratories
111 Locke Drive 111 Locke Drive
Marlborough, MA 01752 USA Marlborough, MA 01752 USA
Telephone: +1-508-786-7554 (w) Telephone: +1-508-786-7554 (w)
EMail: Donald.Eastlake@motorola.com EMail: Donald.Eastlake@motorola.com
Copyright and Disclaimer Copyright and Disclaimer
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
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
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
skipping to change at page 18, line 15 skipping to change at page 19, line 15
INTERNET-DRAFT DNS Cookies INTERNET-DRAFT DNS Cookies
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf- this standard. Please address the information to the IETF at ietf-
ipr@ietf.org. ipr@ietf.org.
Expiration and File Name Expiration and File Name
This draft expires in February 2008. This draft expires in August 2008.
Its file name is draft-eastlake-dnsext-cookies-02.txt Its file name is draft-eastlake-dnsext-cookies-03.txt
 End of changes. 67 change blocks. 
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