< draft-ietf-trans-rfc6962-bis-35.txt   draft-ietf-trans-rfc6962-bis-36.txt >
TRANS (Public Notary Transparency) B. Laurie TRANS (Public Notary Transparency) B. Laurie
Internet-Draft A. Langley Internet-Draft A. Langley
Obsoletes: 6962 (if approved) E. Kasper Obsoletes: 6962 (if approved) E. Kasper
Intended status: Experimental E. Messeri Intended status: Experimental E. Messeri
Expires: 26 September 2021 Google Expires: 14 November 2021 Google
R. Stradling R. Stradling
Sectigo Sectigo
25 March 2021 13 May 2021
Certificate Transparency Version 2.0 Certificate Transparency Version 2.0
draft-ietf-trans-rfc6962-bis-35 draft-ietf-trans-rfc6962-bis-36
Abstract Abstract
This document describes version 2.0 of the Certificate Transparency This document describes version 2.0 of the Certificate Transparency
(CT) protocol for publicly logging the existence of Transport Layer (CT) protocol for publicly logging the existence of Transport Layer
Security (TLS) server certificates as they are issued or observed, in Security (TLS) server certificates as they are issued or observed, in
a manner that allows anyone to audit certification authority (CA) a manner that allows anyone to audit certification authority (CA)
activity and notice the issuance of suspect certificates as well as activity and notice the issuance of suspect certificates as well as
to audit the certificate logs themselves. The intent is that to audit the certificate logs themselves. The intent is that
eventually clients would refuse to honor certificates that do not eventually clients would refuse to honor certificates that do not
appear in a log, effectively forcing CAs to add all issued appear in a log, effectively forcing CAs to add all issued
certificates to the logs. certificates to the logs.
This document obsoletes RFC 6962. It also specifies a new TLS This document obsoletes RFC 6962. It also specifies a new TLS
extension that is used to send various CT log artifacts. extension that is used to send various CT log artifacts.
Logs are network services that implement the protocol operations for Logs are network services that implement the protocol operations for
submissions and queries that are defined in this document. submissions and queries that are defined in this document.
[RFC Editor: please update 'RFCXXXX' to refer to this document, once
its RFC number is known, through the document.]
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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."
This Internet-Draft will expire on 14 November 2021.
This Internet-Draft will expire on 26 September 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 31 skipping to change at page 2, line 32
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.2. Data Structures . . . . . . . . . . . . . . . . . . . . . 5 1.2. Data Structures . . . . . . . . . . . . . . . . . . . . . 5
1.3. Major Differences from CT 1.0 . . . . . . . . . . . . . . 5 1.3. Major Differences from CT 1.0 . . . . . . . . . . . . . . 5
2. Cryptographic Components . . . . . . . . . . . . . . . . . . 7 2. Cryptographic Components . . . . . . . . . . . . . . . . . . 7
2.1. Merkle Hash Trees . . . . . . . . . . . . . . . . . . . . 7 2.1. Merkle Hash Trees . . . . . . . . . . . . . . . . . . . . 7
2.1.1. Definition of the Merkle Tree . . . . . . . . . . . . 7 2.1.1. Definition of the Merkle Tree . . . . . . . . . . . . 7
2.1.2. Verifying a Tree Head Given Entries . . . . . . . . . 8 2.1.2. Verifying a Tree Head Given Entries . . . . . . . . . 8
2.1.3. Merkle Inclusion Proofs . . . . . . . . . . . . . . . 9 2.1.3. Merkle Inclusion Proofs . . . . . . . . . . . . . . . 9
2.1.4. Merkle Consistency Proofs . . . . . . . . . . . . . . 10 2.1.4. Merkle Consistency Proofs . . . . . . . . . . . . . . 10
2.1.5. Example . . . . . . . . . . . . . . . . . . . . . . . 12 2.1.5. Example . . . . . . . . . . . . . . . . . . . . . . . 13
2.2. Signatures . . . . . . . . . . . . . . . . . . . . . . . 14 2.2. Signatures . . . . . . . . . . . . . . . . . . . . . . . 14
3. Submitters . . . . . . . . . . . . . . . . . . . . . . . . . 15 3. Submitters . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1. Certificates . . . . . . . . . . . . . . . . . . . . . . 15 3.1. Certificates . . . . . . . . . . . . . . . . . . . . . . 15
3.2. Precertificates . . . . . . . . . . . . . . . . . . . . . 15 3.2. Precertificates . . . . . . . . . . . . . . . . . . . . . 15
3.2.1. Binding Intent to Issue . . . . . . . . . . . . . . . 17 3.2.1. Binding Intent to Issue . . . . . . . . . . . . . . . 17
4. Log Format and Operation . . . . . . . . . . . . . . . . . . 17 4. Log Format and Operation . . . . . . . . . . . . . . . . . . 17
4.1. Log Parameters . . . . . . . . . . . . . . . . . . . . . 18 4.1. Log Parameters . . . . . . . . . . . . . . . . . . . . . 18
4.2. Evaluating Submissions . . . . . . . . . . . . . . . . . 19 4.2. Evaluating Submissions . . . . . . . . . . . . . . . . . 19
4.2.1. Minimum Acceptance Criteria . . . . . . . . . . . . . 19 4.2.1. Minimum Acceptance Criteria . . . . . . . . . . . . . 19
4.2.2. Discretionary Acceptance Criteria . . . . . . . . . . 20 4.2.2. Discretionary Acceptance Criteria . . . . . . . . . . 20
4.3. Log Entries . . . . . . . . . . . . . . . . . . . . . . . 21 4.3. Log Entries . . . . . . . . . . . . . . . . . . . . . . . 20
4.4. Log ID . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.4. Log ID . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.5. TransItem Structure . . . . . . . . . . . . . . . . . . . 21 4.5. TransItem Structure . . . . . . . . . . . . . . . . . . . 21
4.6. Log Artifact Extensions . . . . . . . . . . . . . . . . . 22 4.6. Log Artifact Extensions . . . . . . . . . . . . . . . . . 22
4.7. Merkle Tree Leaves . . . . . . . . . . . . . . . . . . . 23 4.7. Merkle Tree Leaves . . . . . . . . . . . . . . . . . . . 23
4.8. Signed Certificate Timestamp (SCT) . . . . . . . . . . . 24 4.8. Signed Certificate Timestamp (SCT) . . . . . . . . . . . 24
4.9. Merkle Tree Head . . . . . . . . . . . . . . . . . . . . 25 4.9. Merkle Tree Head . . . . . . . . . . . . . . . . . . . . 25
4.10. Signed Tree Head (STH) . . . . . . . . . . . . . . . . . 25 4.10. Signed Tree Head (STH) . . . . . . . . . . . . . . . . . 26
4.11. Merkle Consistency Proofs . . . . . . . . . . . . . . . . 26 4.11. Merkle Consistency Proofs . . . . . . . . . . . . . . . . 26
4.12. Merkle Inclusion Proofs . . . . . . . . . . . . . . . . . 27 4.12. Merkle Inclusion Proofs . . . . . . . . . . . . . . . . . 27
4.13. Shutting down a log . . . . . . . . . . . . . . . . . . . 27 4.13. Shutting down a log . . . . . . . . . . . . . . . . . . . 28
5. Log Client Messages . . . . . . . . . . . . . . . . . . . . . 28 5. Log Client Messages . . . . . . . . . . . . . . . . . . . . . 28
5.1. Submit Entry to Log . . . . . . . . . . . . . . . . . . . 30 5.1. Submit Entry to Log . . . . . . . . . . . . . . . . . . . 30
5.2. Retrieve Latest Signed Tree Head . . . . . . . . . . . . 32 5.2. Retrieve Latest Signed Tree Head . . . . . . . . . . . . 32
5.3. Retrieve Merkle Consistency Proof between Two Signed Tree 5.3. Retrieve Merkle Consistency Proof between Two Signed Tree
Heads . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Heads . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.4. Retrieve Merkle Inclusion Proof from Log by Leaf Hash . . 33 5.4. Retrieve Merkle Inclusion Proof from Log by Leaf Hash . . 33
5.5. Retrieve Merkle Inclusion Proof, Signed Tree Head and 5.5. Retrieve Merkle Inclusion Proof, Signed Tree Head and
Consistency Proof by Leaf Hash . . . . . . . . . . . . . 34 Consistency Proof by Leaf Hash . . . . . . . . . . . . . 34
5.6. Retrieve Entries and STH from Log . . . . . . . . . . . . 35 5.6. Retrieve Entries and STH from Log . . . . . . . . . . . . 35
5.7. Retrieve Accepted Trust Anchors . . . . . . . . . . . . . 37 5.7. Retrieve Accepted Trust Anchors . . . . . . . . . . . . . 37
6. TLS Servers . . . . . . . . . . . . . . . . . . . . . . . . . 38 6. TLS Servers . . . . . . . . . . . . . . . . . . . . . . . . . 38
6.1. TLS Client Authentication . . . . . . . . . . . . . . . . 38 6.1. TLS Client Authentication . . . . . . . . . . . . . . . . 38
6.2. Multiple SCTs . . . . . . . . . . . . . . . . . . . . . . 39 6.2. Multiple SCTs . . . . . . . . . . . . . . . . . . . . . . 39
6.3. TransItemList Structure . . . . . . . . . . . . . . . . . 39 6.3. TransItemList Structure . . . . . . . . . . . . . . . . . 39
6.4. Presenting SCTs, inclusions proofs and STHs . . . . . . . 40 6.4. Presenting SCTs, inclusions proofs and STHs . . . . . . . 40
6.5. transparency_info TLS Extension . . . . . . . . . . . . . 40 6.5. transparency_info TLS Extension . . . . . . . . . . . . . 40
7. Certification Authorities . . . . . . . . . . . . . . . . . . 40 7. Certification Authorities . . . . . . . . . . . . . . . . . . 41
7.1. Transparency Information X.509v3 Extension . . . . . . . 41 7.1. Transparency Information X.509v3 Extension . . . . . . . 41
7.1.1. OCSP Response Extension . . . . . . . . . . . . . . . 41 7.1.1. OCSP Response Extension . . . . . . . . . . . . . . . 41
7.1.2. Certificate Extension . . . . . . . . . . . . . . . . 41 7.1.2. Certificate Extension . . . . . . . . . . . . . . . . 41
7.2. TLS Feature X.509v3 Extension . . . . . . . . . . . . . . 41 7.2. TLS Feature X.509v3 Extension . . . . . . . . . . . . . . 41
8. Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 8. Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.1. TLS Client . . . . . . . . . . . . . . . . . . . . . . . 42 8.1. TLS Client . . . . . . . . . . . . . . . . . . . . . . . 42
8.1.1. Receiving SCTs and inclusion proofs . . . . . . . . . 42 8.1.1. Receiving SCTs and inclusion proofs . . . . . . . . . 42
8.1.2. Reconstructing the TBSCertificate . . . . . . . . . . 42 8.1.2. Reconstructing the TBSCertificate . . . . . . . . . . 42
8.1.3. Validating SCTs . . . . . . . . . . . . . . . . . . . 42 8.1.3. Validating SCTs . . . . . . . . . . . . . . . . . . . 42
8.1.4. Fetching inclusion proofs . . . . . . . . . . . . . . 43 8.1.4. Fetching inclusion proofs . . . . . . . . . . . . . . 43
8.1.5. Validating inclusion proofs . . . . . . . . . . . . . 43 8.1.5. Validating inclusion proofs . . . . . . . . . . . . . 43
8.1.6. Evaluating compliance . . . . . . . . . . . . . . . . 44 8.1.6. Evaluating compliance . . . . . . . . . . . . . . . . 44
8.2. Monitor . . . . . . . . . . . . . . . . . . . . . . . . . 44 8.2. Monitor . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.3. Auditing . . . . . . . . . . . . . . . . . . . . . . . . 45 8.3. Auditing . . . . . . . . . . . . . . . . . . . . . . . . 45
9. Algorithm Agility . . . . . . . . . . . . . . . . . . . . . . 46 9. Algorithm Agility . . . . . . . . . . . . . . . . . . . . . . 46
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47
10.1. New Entry to the TLS ExtensionType Registry . . . . . . 47 10.1. New Entry to the TLS ExtensionType Registry . . . . . . 47
10.2. Hash Algorithms . . . . . . . . . . . . . . . . . . . . 47 10.2. Hash Algorithms . . . . . . . . . . . . . . . . . . . . 47
10.2.1. Specification Required guidance . . . . . . . . . . 47 10.2.1. Specification Required guidance . . . . . . . . . . 47
10.3. Signature Algorithms . . . . . . . . . . . . . . . . . . 48 10.3. Signature Algorithms . . . . . . . . . . . . . . . . . . 48
10.3.1. Expert Review guidelines . . . . . . . . . . . . . . 48 10.3.1. Expert Review guidelines . . . . . . . . . . . . . . 49
10.4. VersionedTransTypes . . . . . . . . . . . . . . . . . . 49 10.4. VersionedTransTypes . . . . . . . . . . . . . . . . . . 49
10.4.1. Specification Required guidance . . . . . . . . . . 49
10.5. Log Artifact Extension Registry . . . . . . . . . . . . 50 10.5. Log Artifact Extension Registry . . . . . . . . . . . . 50
10.5.1. Specification Required guidance . . . . . . . . . . 50 10.5.1. Specification Required guidance . . . . . . . . . . 51
10.6. Object Identifiers . . . . . . . . . . . . . . . . . . . 50 10.6. Object Identifiers . . . . . . . . . . . . . . . . . . . 51
10.6.1. Log ID Registry . . . . . . . . . . . . . . . . . . 50 10.6.1. Log ID Registry . . . . . . . . . . . . . . . . . . 51
10.7. URN Sub-namespace for TRANS errors 10.7. URN Sub-namespace for TRANS errors
(urn:ietf:params:trans:error) . . . . . . . . . . . . . 51 (urn:ietf:params:trans:error) . . . . . . . . . . . . . 52
10.7.1. TRANS Error Types . . . . . . . . . . . . . . . . . 52 10.7.1. TRANS Error Types . . . . . . . . . . . . . . . . . 53
11. Security Considerations . . . . . . . . . . . . . . . . . . . 53
11.1. Misissued Certificates . . . . . . . . . . . . . . . . . 54 11. Security Considerations . . . . . . . . . . . . . . . . . . . 54
11.2. Detection of Misissue . . . . . . . . . . . . . . . . . 54 11.1. Misissued Certificates . . . . . . . . . . . . . . . . . 55
11.3. Misbehaving Logs . . . . . . . . . . . . . . . . . . . . 54 11.2. Detection of Misissue . . . . . . . . . . . . . . . . . 55
11.4. Preventing Tracking Clients . . . . . . . . . . . . . . 55 11.3. Misbehaving Logs . . . . . . . . . . . . . . . . . . . . 55
11.5. Multiple SCTs . . . . . . . . . . . . . . . . . . . . . 55 11.4. Multiple SCTs . . . . . . . . . . . . . . . . . . . . . 56
11.6. Leakage of DNS Information . . . . . . . . . . . . . . . 55 11.5. Leakage of DNS Information . . . . . . . . . . . . . . . 56
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 55 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 56
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 56 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 57
13.1. Normative References . . . . . . . . . . . . . . . . . . 56 13.1. Normative References . . . . . . . . . . . . . . . . . . 57
13.2. Informative References . . . . . . . . . . . . . . . . . 57 13.2. Informative References . . . . . . . . . . . . . . . . . 59
Appendix A. Supporting v1 and v2 simultaneously . . . . . . . . 59 Appendix A. Supporting v1 and v2 simultaneously (Informative) . 60
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 60 Appendix B. An ASN.1 Module (Informative) . . . . . . . . . . . 61
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 62
1. Introduction 1. Introduction
Certificate Transparency aims to mitigate the problem of misissued Certificate Transparency aims to mitigate the problem of misissued
certificates by providing append-only logs of issued certificates. certificates by providing append-only logs of issued certificates.
The logs do not themselves prevent misissuance, but they ensure that The logs do not themselves prevent misissuance, but they ensure that
interested parties (particularly those named in certificates) can interested parties (particularly those named in certificates) can
detect such misissuance. Note that this is a general mechanism that detect such misissuance. Note that this is a general mechanism that
could be used for transparently logging any form of binary data, could be used for transparently logging any form of binary data,
subject to some kind of inclusion criteria. In this document, we subject to some kind of inclusion criteria. In this document, we
only describe its use for public TLS server certificates (i.e., where only describe its use for public TLS server certificates (i.e., where
the inclusion criteria is a valid certificate issued by a public the inclusion criteria is a valid certificate issued by a public
certification authority (CA)). certification authority (CA)). A typical definition of "public" can
be found in [CABBR].
Each log contains certificate chains, which can be submitted by Each log contains certificate chains, which can be submitted by
anyone. It is expected that public CAs will contribute all their anyone. It is expected that public CAs will contribute all their
newly issued certificates to one or more logs; however certificate newly issued certificates to one or more logs; however certificate
holders can also contribute their own certificate chains, as can holders can also contribute their own certificate chains, as can
third parties. In order to avoid logs being rendered useless by the third parties. In order to avoid logs being rendered useless by the
submission of large numbers of spurious certificates, it is required submission of large numbers of spurious certificates, it is required
that each chain ends with a trust anchor that is accepted by the log. that each chain ends with a trust anchor that is accepted by the log.
When a chain is accepted by a log, a signed timestamp is returned, A log may also limit the length of the chain it is willing to accept;
which can later be used to provide evidence to TLS clients that the such chains must also end with an acceptable trust anchor. When a
chain has been submitted. TLS clients can thus require that all chain is accepted by a log, a signed timestamp is returned, which can
certificates they accept as valid are accompanied by signed later be used to provide evidence to TLS clients that the chain has
timestamps. been submitted. TLS clients can thus require that all certificates
they accept as valid are accompanied by signed timestamps.
Those who are concerned about misissuance can monitor the logs, Those who are concerned about misissuance can monitor the logs,
asking them regularly for all new entries, and can thus check whether asking them regularly for all new entries, and can thus check whether
domains for which they are responsible have had certificates issued domains for which they are responsible have had certificates issued
that they did not expect. What they do with this information, that they did not expect. What they do with this information,
particularly when they find that a misissuance has happened, is particularly when they find that a misissuance has happened, is
beyond the scope of this document. However, broadly speaking, they beyond the scope of this document. However, broadly speaking, they
can invoke existing business mechanisms for dealing with misissued can invoke existing business mechanisms for dealing with misissued
certificates, such as working with the CA to get the certificate certificates, such as working with the CA to get the certificate
revoked, or with maintainers of trust anchor lists to get the CA revoked, or with maintainers of trust anchor lists to get the CA
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The append-only property of each log is achieved using Merkle Trees, The append-only property of each log is achieved using Merkle Trees,
which can be used to efficiently prove that any particular instance which can be used to efficiently prove that any particular instance
of the log is a superset of any particular previous instance and to of the log is a superset of any particular previous instance and to
efficiently detect various misbehaviors of the log (e.g., issuing a efficiently detect various misbehaviors of the log (e.g., issuing a
signed timestamp for a certificate that is not subsequently logged). signed timestamp for a certificate that is not subsequently logged).
It is necessary to treat each log as a trusted third party, because It is necessary to treat each log as a trusted third party, because
the log auditing mechanisms described in this document can be the log auditing mechanisms described in this document can be
circumvented by a misbehaving log that shows different, inconsistent circumvented by a misbehaving log that shows different, inconsistent
views of itself to different clients. Whilst it is anticipated that views of itself to different clients. While mechanisms are being
additional mechanisms could be developed to address these developed to address these shortcomings and thereby avoid the need to
shortcomings and thereby avoid the need to blindly trust logs, such blindly trust logs, such mechanisms are outside the scope of this
mechanisms are outside the scope of this document. document.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. Data Structures 1.2. Data Structures
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inclusion proofs, for verifying consistency between two STHs, and inclusion proofs, for verifying consistency between two STHs, and
for verifying a root hash given a complete list of the relevant for verifying a root hash given a complete list of the relevant
leaf input entries. leaf input entries.
* Extensive clarifications and editorial work. * Extensive clarifications and editorial work.
2. Cryptographic Components 2. Cryptographic Components
2.1. Merkle Hash Trees 2.1. Merkle Hash Trees
A full description of Merkle Hash Tree is beyond the scope of this
document. Briefly, it is a binary tree where each non-leaf node is a
hash of its children. For CT, the number of children is at most two.
Additional information can be found in the Introduction and Reference
section of [RFC8391].
2.1.1. Definition of the Merkle Tree 2.1.1. Definition of the Merkle Tree
The log uses a binary Merkle Hash Tree for efficient auditing. The The log uses a binary Merkle Hash Tree for efficient auditing. The
hash algorithm used is one of the log's parameters (see Section 4.1). hash algorithm used is one of the log's parameters (see Section 4.1).
This document establishes a registry of acceptable hash algorithms This document establishes a registry of acceptable hash algorithms
(see Section 10.2). Throughout this document, the hash algorithm in (see Section 10.2). Throughout this document, the hash algorithm in
use is referred to as HASH and the size of its output in bytes as use is referred to as HASH and the size of its output in bytes as
HASH_SIZE. The input to the Merkle Tree Hash is a list of data HASH_SIZE. The input to the Merkle Tree Hash is a list of data
entries; these entries will be hashed to form the leaves of the entries; these entries will be hashed to form the leaves of the
Merkle Hash Tree. The output is a single HASH_SIZE Merkle Tree Hash. Merkle Hash Tree. The output is a single HASH_SIZE Merkle Tree Hash.
skipping to change at page 8, line 17 skipping to change at page 8, line 24
Note that we do not require the length of the input list to be a Note that we do not require the length of the input list to be a
power of two. The resulting Merkle Tree may thus not be balanced; power of two. The resulting Merkle Tree may thus not be balanced;
however, its shape is uniquely determined by the number of leaves. however, its shape is uniquely determined by the number of leaves.
(Note: This Merkle Tree is essentially the same as the history tree (Note: This Merkle Tree is essentially the same as the history tree
[CrosbyWallach] proposal, except our definition handles non-full [CrosbyWallach] proposal, except our definition handles non-full
trees differently). trees differently).
2.1.2. Verifying a Tree Head Given Entries 2.1.2. Verifying a Tree Head Given Entries
When a client has a complete list of n input "entries" from "0" up to When a client has a complete list of "entries" from "0" up to
"tree_size - 1" and wishes to verify this list against a tree head "tree_size - 1" and wishes to verify this list against a tree head
"root_hash" returned by the log for the same "tree_size", the "root_hash" returned by the log for the same "tree_size", the
following algorithm may be used: following algorithm may be used:
1. Set "stack" to an empty stack. 1. Set "stack" to an empty stack.
2. For each "i" from "0" up to "tree_size - 1": 2. For each "i" from "0" up to "tree_size - 1":
1. Push "HASH(0x00 || entries[i])" to "stack". 1. Push "HASH(0x00 || entries[i])" to "stack".
2. Set "merge_count" to the lowest value ("0" included) such 2. Set "merge_count" to the lowest value ("0" included) such
that "LSB(i >> merge_count)" is not set. In other words, set that "LSB(i >> merge_count)" is not set, where "LSB" means
"merge_count" to the number of consecutive "1"s found the least significant bit. In other words, set "merge_count"
starting at the least significant bit of "i". to the number of consecutive "1"s found starting at the least
significant bit of "i".
3. Repeat "merge_count" times: 3. Repeat "merge_count" times:
1. Pop "right" from "stack". 1. Pop "right" from "stack".
2. Pop "left" from "stack". 2. Pop "left" from "stack".
3. Push "HASH(0x01 || left || right)" to "stack". 3. Push "HASH(0x01 || left || right)" to "stack".
3. If there is more than one element in the "stack", repeat the same 3. If there is more than one element in the "stack", repeat the same
merge procedure (Step 2.3 above) until only a single element merge procedure (the sub-items of Step 2.3 above) until only a
remains. single element remains.
4. The remaining element in "stack" is the Merkle Tree hash for the 4. The remaining element in "stack" is the Merkle Tree hash for the
given "tree_size" and should be compared by equality against the given "tree_size" and should be compared by equality against the
supplied "root_hash". supplied "root_hash".
2.1.3. Merkle Inclusion Proofs 2.1.3. Merkle Inclusion Proofs
A Merkle inclusion proof for a leaf in a Merkle Hash Tree is the A Merkle inclusion proof for a leaf in a Merkle Hash Tree is the
shortest list of additional nodes in the Merkle Tree required to shortest list of additional nodes in the Merkle Tree required to
compute the Merkle Tree Hash for that tree. Each node in the tree is compute the Merkle Tree Hash for that tree. Each node in the tree is
skipping to change at page 9, line 48 skipping to change at page 10, line 5
The : operator and D[k1:k2] are defined the same as in Section 2.1.1. The : operator and D[k1:k2] are defined the same as in Section 2.1.1.
2.1.3.2. Verifying an Inclusion Proof 2.1.3.2. Verifying an Inclusion Proof
When a client has received an inclusion proof (e.g., in a "TransItem" When a client has received an inclusion proof (e.g., in a "TransItem"
of type "inclusion_proof_v2") and wishes to verify inclusion of an of type "inclusion_proof_v2") and wishes to verify inclusion of an
input "hash" for a given "tree_size" and "root_hash", the following input "hash" for a given "tree_size" and "root_hash", the following
algorithm may be used to prove the "hash" was included in the algorithm may be used to prove the "hash" was included in the
"root_hash": "root_hash":
1. Compare "leaf_index" against "tree_size". If "leaf_index" is 1. Compare "leaf_index" from the "inclusion_proof_v2" structure
greater than or equal to "tree_size" then fail the proof against "tree_size". If "leaf_index" is greater than or equal to
verification. "tree_size" then fail the proof verification.
2. Set "fn" to "leaf_index" and "sn" to "tree_size - 1". 2. Set "fn" to "leaf_index" and "sn" to "tree_size - 1".
3. Set "r" to "hash". 3. Set "r" to "hash".
4. For each value "p" in the "inclusion_path" array: 4. For each value "p" in the "inclusion_path" array:
If "sn" is 0, stop the iteration and fail the proof verification. If "sn" is 0, stop the iteration and fail the proof verification.
If "LSB(fn)" is set, or if "fn" is equal to "sn", then: If "LSB(fn)" is set, or if "fn" is equal to "sn", then:
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same nodes can be used to verify MTH(D[0:m]). We define an algorithm same nodes can be used to verify MTH(D[0:m]). We define an algorithm
that outputs the (unique) minimal consistency proof. that outputs the (unique) minimal consistency proof.
2.1.4.1. Generating a Consistency Proof 2.1.4.1. Generating a Consistency Proof
Given an ordered list of n inputs to the tree, D_n = {d[0], d[1], Given an ordered list of n inputs to the tree, D_n = {d[0], d[1],
..., d[n-1]}, the Merkle consistency proof PROOF(m, D_n) for a ..., d[n-1]}, the Merkle consistency proof PROOF(m, D_n) for a
previous Merkle Tree Hash MTH(D[0:m]), 0 < m < n, is defined as: previous Merkle Tree Hash MTH(D[0:m]), 0 < m < n, is defined as:
PROOF(m, D_n) = SUBPROOF(m, D_n, true) PROOF(m, D_n) = SUBPROOF(m, D_n, true)
In SUBPROOF, the boolean value represents whether the subtree created In SUBPROOF, the boolean value represents whether the subtree created
from D[0:m] is a complete subtree of the Merkle Tree created from from D[0:m] is a complete subtree of the Merkle Tree created from
D_n, and, consequently, whether the subtree Merkle Tree Hash D_n, and, consequently, whether the subtree Merkle Tree Hash
MTH(D[0:m]) is known. The initial call to SUBPROOF sets this to be MTH(D[0:m]) is known. The initial call to SUBPROOF sets this to be
true, and SUBPROOF is then defined as follows: true, and SUBPROOF is then defined as follows:
The subproof for m = n is empty if m is the value for which PROOF was The subproof for m = n is empty if m is the value for which PROOF was
originally requested (meaning that the subtree created from D[0:m] is originally requested (meaning that the subtree created from D[0:m] is
a complete subtree of the Merkle Tree created from the original D_n a complete subtree of the Merkle Tree created from the original D_n
for which PROOF was requested, and the subtree Merkle Tree Hash for which PROOF was requested, and the subtree Merkle Tree Hash
MTH(D[0:m]) is known): MTH(D[0:m]) is known):
SUBPROOF(m, D[m], true) = {} SUBPROOF(m, D_m, true) = {}
Otherwise, the subproof for m = n is the Merkle Tree Hash committing Otherwise, the subproof for m = n is the Merkle Tree Hash committing
inputs D[0:m]: inputs D[0:m]:
SUBPROOF(m, D[m], false) = {MTH(D[m])} SUBPROOF(m, D_m, false) = {MTH(D_m)}
For m < n, let k be the largest power of two smaller than n. The For m < n, let k be the largest power of two smaller than n. The
subproof is then defined recursively. subproof is then defined recursively, using the appropriate step
below:
If m <= k, the right subtree entries D[k:n] only exist in the current If m <= k, the right subtree entries D[k:n] only exist in the current
tree. We prove that the left subtree entries D[0:k] are consistent tree. We prove that the left subtree entries D[0:k] are consistent
and add a commitment to D[k:n]: and add a commitment to D[k:n]:
SUBPROOF(m, D_n, b) = SUBPROOF(m, D[0:k], b) : MTH(D[k:n]) SUBPROOF(m, D_n, b) = SUBPROOF(m, D[0:k], b) : MTH(D[k:n])
If m > k, the left subtree entries D[0:k] are identical in both If m > k, the left subtree entries D[0:k] are identical in both
trees. We prove that the right subtree entries D[k:n] are consistent trees. We prove that the right subtree entries D[k:n] are consistent
and add a commitment to D[0:k]. and add a commitment to D[0:k].
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The : operator and D[k1:k2] are defined the same as in Section 2.1.1. The : operator and D[k1:k2] are defined the same as in Section 2.1.1.
2.1.4.2. Verifying Consistency between Two Tree Heads 2.1.4.2. Verifying Consistency between Two Tree Heads
When a client has a tree head "first_hash" for tree size "first", a When a client has a tree head "first_hash" for tree size "first", a
tree head "second_hash" for tree size "second" where "0 < first < tree head "second_hash" for tree size "second" where "0 < first <
second", and has received a consistency proof between the two (e.g., second", and has received a consistency proof between the two (e.g.,
in a "TransItem" of type "consistency_proof_v2"), the following in a "TransItem" of type "consistency_proof_v2"), the following
algorithm may be used to verify the consistency proof: algorithm may be used to verify the consistency proof:
1. If "first" is an exact power of 2, then prepend "first_hash" to 1. If "consistency_path" is an empty array, stop and fail the proof
verification.
2. If "first" is an exact power of 2, then prepend "first_hash" to
the "consistency_path" array. the "consistency_path" array.
2. Set "fn" to "first - 1" and "sn" to "second - 1". 3. Set "fn" to "first - 1" and "sn" to "second - 1".
3. If "LSB(fn)" is set, then right-shift both "fn" and "sn" equally 4. If "LSB(fn)" is set, then right-shift both "fn" and "sn" equally
until "LSB(fn)" is not set. until "LSB(fn)" is not set.
4. Set both "fr" and "sr" to the first value in the 5. Set both "fr" and "sr" to the first value in the
"consistency_path" array. "consistency_path" array.
5. For each subsequent value "c" in the "consistency_path" array: 6. For each subsequent value "c" in the "consistency_path" array:
If "sn" is 0, stop the iteration and fail the proof verification. If "sn" is 0, stop the iteration and fail the proof verification.
If "LSB(fn)" is set, or if "fn" is equal to "sn", then: If "LSB(fn)" is set, or if "fn" is equal to "sn", then:
1. Set "fr" to "HASH(0x01 || c || fr)" 1. Set "fr" to "HASH(0x01 || c || fr)"
Set "sr" to "HASH(0x01 || c || sr)" Set "sr" to "HASH(0x01 || c || sr)"
2. If "LSB(fn)" is not set, then right-shift both "fn" and "sn" 2. If "LSB(fn)" is not set, then right-shift both "fn" and "sn"
equally until either "LSB(fn)" is set or "fn" is "0". equally until either "LSB(fn)" is set or "fn" is "0".
Otherwise: Otherwise:
1. Set "sr" to "HASH(0x01 || sr || c)" 1. Set "sr" to "HASH(0x01 || sr || c)"
Finally, right-shift both "fn" and "sn" one time. Finally, right-shift both "fn" and "sn" one time.
6. After completing iterating through the "consistency_path" array 7. After completing iterating through the "consistency_path" array
as described above, verify that the "fr" calculated is equal to as described above, verify that the "fr" calculated is equal to
the "first_hash" supplied, that the "sr" calculated is equal to the "first_hash" supplied, that the "sr" calculated is equal to
the "second_hash" supplied and that "sn" is 0. the "second_hash" supplied and that "sn" is 0.
2.1.5. Example 2.1.5. Example
The binary Merkle Tree with 7 leaves: The binary Merkle Tree with 7 leaves:
hash hash
/ \ / \
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The consistency proof between hash1 and hash is PROOF(4, D[7]) = [l]. The consistency proof between hash1 and hash is PROOF(4, D[7]) = [l].
hash can be verified using hash1=k and l. hash can be verified using hash1=k and l.
The consistency proof between hash2 and hash is PROOF(6, D[7]) = [i, The consistency proof between hash2 and hash is PROOF(6, D[7]) = [i,
j, k]. k, i are used to verify hash2, and j is additionally used to j, k]. k, i are used to verify hash2, and j is additionally used to
show hash is consistent with hash2. show hash is consistent with hash2.
2.2. Signatures 2.2. Signatures
Various data structures Section 1.2 are signed. A log MUST use one When signing data structures, a log MUST use one of the signature
of the signature algorithms defined in Section 10.3. algorithms from the IANA CT Signature Algorithms registry, described
in Section 10.3.
3. Submitters 3. Submitters
Submitters submit certificates or preannouncements of certificates Submitters submit certificates or preannouncements of certificates
prior to issuance (precertificates) to logs for public auditing, as prior to issuance (precertificates) to logs for public auditing, as
described below. In order to enable attribution of each logged described below. In order to enable attribution of each logged
certificate or precertificate to its issuer, each submission MUST be certificate or precertificate to its issuer, each submission MUST be
accompanied by all additional certificates required to verify the accompanied by all additional certificates required to verify the
chain up to an accepted trust anchor (Section 5.7). The trust anchor chain up to an accepted trust anchor (Section 5.7). The trust anchor
(a root or intermediate CA certificate) MAY be omitted from the (a root or intermediate CA certificate) MAY be omitted from the
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precertificate (Section 5.1) that the log can use to create an entry precertificate (Section 5.1) that the log can use to create an entry
that will be valid against the issued certificate. The CA MAY that will be valid against the issued certificate. The CA MAY
incorporate the returned SCT in the issued certificate. One example incorporate the returned SCT in the issued certificate. One example
of where the returned SCT is not incorporated in the issued of where the returned SCT is not incorporated in the issued
certificate is when a CA sends the precertificate to multiple logs, certificate is when a CA sends the precertificate to multiple logs,
but only incorporates the SCTs that are returned first. but only incorporates the SCTs that are returned first.
A precertificate is a CMS [RFC5652] "signed-data" object that A precertificate is a CMS [RFC5652] "signed-data" object that
conforms to the following profile: conforms to the following profile:
* It MUST be DER encoded. * It MUST be DER encoded as described in [X690].
* "SignedData.version" MUST be v3(3). * "SignedData.version" MUST be v3(3).
* "SignedData.digestAlgorithms" MUST only include the * "SignedData.digestAlgorithms" MUST be the same as the
"SignerInfo.digestAlgorithm" OID value (see below). "SignerInfo.digestAlgorithm" OID value (see below).
* "SignedData.encapContentInfo": * "SignedData.encapContentInfo":
- "eContentType" MUST be the OID 1.3.101.78. - "eContentType" MUST be the OID 1.3.101.78.
- "eContent" MUST contain a TBSCertificate [RFC5280] that will be - "eContent" MUST contain a TBSCertificate [RFC5280] that will be
identical to the TBSCertificate in the issued certificate, identical to the TBSCertificate in the issued certificate,
except that the Transparency Information (Section 7.1) except that the Transparency Information (Section 7.1)
extension MUST be omitted. extension MUST be omitted.
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* "SignedData.crls" MUST be omitted. * "SignedData.crls" MUST be omitted.
* "SignedData.signerInfos" MUST contain one "SignerInfo": * "SignedData.signerInfos" MUST contain one "SignerInfo":
- "version" MUST be v3(3). - "version" MUST be v3(3).
- "sid" MUST use the "subjectKeyIdentifier" option. - "sid" MUST use the "subjectKeyIdentifier" option.
- "digestAlgorithm" MUST be one of the hash algorithm OIDs listed - "digestAlgorithm" MUST be one of the hash algorithm OIDs listed
in Section 10.2. in the IANA CT Hash Algorithms Registry, described in
Section 10.2.
- "signedAttrs" MUST be present and MUST contain two attributes: - "signedAttrs" MUST be present and MUST contain two attributes:
o A content-type attribute whose value is the same as o A content-type attribute whose value is the same as
"SignedData.encapContentInfo.eContentType". "SignedData.encapContentInfo.eContentType".
o A message-digest attribute whose value is the message digest o A message-digest attribute whose value is the message digest
of "SignedData.encapContentInfo.eContent". of "SignedData.encapContentInfo.eContent".
- "signatureAlgorithm" MUST be the same OID as - "signatureAlgorithm" MUST be the same OID as
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corresponding precertificate. corresponding precertificate.
4. Log Format and Operation 4. Log Format and Operation
A log is a single, append-only Merkle Tree of submitted certificate A log is a single, append-only Merkle Tree of submitted certificate
and precertificate entries. and precertificate entries.
When it receives and accepts a valid submission, the log MUST return When it receives and accepts a valid submission, the log MUST return
an SCT that corresponds to the submitted certificate or an SCT that corresponds to the submitted certificate or
precertificate. If the log has previously seen this valid precertificate. If the log has previously seen this valid
submission, it SHOULD return the same SCT as it returned before (to submission, it SHOULD return the same SCT as it returned before, as
reduce the ability to track clients as described in Section 11.4). discussed in Section 11.3. If different SCTs are produced for the
If different SCTs are produced for the same submission, multiple log same submission, multiple log entries will have to be created, one
entries will have to be created, one for each SCT (as the timestamp for each SCT (as the timestamp is a part of the leaf structure).
is a part of the leaf structure). Note that if a certificate was Note that if a certificate was previously logged as a precertificate,
previously logged as a precertificate, then the precertificate's SCT then the precertificate's SCT of type "precert_sct_v2" would not be
of type "precert_sct_v2" would not be appropriate; instead, a fresh appropriate; instead, a fresh SCT of type "x509_sct_v2" should be
SCT of type "x509_sct_v2" should be generated. generated.
An SCT is the log's promise to append to its Merkle Tree an entry for An SCT is the log's promise to append to its Merkle Tree an entry for
the accepted submission. Upon producing an SCT, the log MUST fulfil the accepted submission. Upon producing an SCT, the log MUST fulfil
this promise by performing the following actions within a fixed this promise by performing the following actions within a fixed
amount of time known as the Maximum Merge Delay (MMD), which is one amount of time known as the Maximum Merge Delay (MMD), which is one
of the log's parameters (see Section 4.1): of the log's parameters (see Section 4.1):
* Allocate a tree index to the entry representing the accepted * Allocate a tree index to the entry representing the accepted
submission. submission.
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sharing data from the log. sharing data from the log.
4.1. Log Parameters 4.1. Log Parameters
A log is defined by a collection of immutable parameters, which are A log is defined by a collection of immutable parameters, which are
used by clients to communicate with the log and to verify log used by clients to communicate with the log and to verify log
artifacts. Except for the Final Signed Tree Head (STH), each of artifacts. Except for the Final Signed Tree Head (STH), each of
these parameters MUST be established before the log operator begins these parameters MUST be established before the log operator begins
to operate the log. to operate the log.
Base URL: The prefix used to construct URLs for client messages (see Base URL: The prefix used to construct URLs ([RFC3986]) for client
Section 5). The base URL MUST be an "https" URL, MAY contain a messages (see Section 5). The base URL MUST be an "https" URL,
port, MAY contain a path with any number of path segments, but MAY contain a port, MAY contain a path with any number of path
MUST NOT contain a query string, fragment, or trailing "/". segments, but MUST NOT contain a query string, fragment, or
Example: https://ct.example.org/blue trailing "/". Example: https://ct.example.org/blue
Hash Algorithm: The hash algorithm used for the Merkle Tree (see Hash Algorithm: The hash algorithm used for the Merkle Tree (see
Section 10.2). Section 10.2).
Signature Algorithm: The signature algorithm used (see Section 2.2). Signature Algorithm: The signature algorithm used (see Section 2.2).
Public Key: The public key used to verify signatures generated by Public Key: The public key used to verify signatures generated by
the log. A log MUST NOT use the same keypair as any other log. the log. A log MUST NOT use the same keypair as any other log.
Log ID: The OID that uniquely identifies the log. Log ID: The OID that uniquely identifies the log.
Maximum Merge Delay: The MMD the log has committed to. Maximum Merge Delay: The MMD the log has committed to. This
document deliberately does not specify any limits on the value, to
allow for experimentation.
Version: The version of the protocol supported by the log (currently Version: The version of the protocol supported by the log (currently
1 or 2). 1 or 2).
Maximum Chain Length: The longest chain submission the log is Maximum Chain Length: The longest certificate chain submission the
willing to accept, if the log imposes any limit. log is willing to accept, if the log imposes any limit.
STH Frequency Count: The maximum number of STHs the log may produce STH Frequency Count: The maximum number of STHs the log may produce
in any period equal to the "Maximum Merge Delay" (see in any period equal to the "Maximum Merge Delay" (see
Section 4.10). Section 4.10).
Final STH: If a log has been closed down (i.e., no longer accepts Final STH: If a log has been closed down (i.e., no longer accepts
new entries), existing entries may still be valid. In this case, new entries), existing entries may still be valid. In this case,
the client should know the final valid STH in the log to ensure no the client should know the final valid STH in the log to ensure no
new entries can be added without detection. The final STH should new entries can be added without detection. This value MUST be
be provided in the form of a TransItem of type provided in the form of a TransItem of type "signed_tree_head_v2".
"signed_tree_head_v2". If a log is still accepting entries, this value should not be
provided.
[JSON.Metadata] is an example of a metadata format which includes the [JSON.Metadata] is an example of a metadata format which includes the
above elements. above elements.
4.2. Evaluating Submissions 4.2. Evaluating Submissions
A log determines whether to accept or reject a submission by A log determines whether to accept or reject a submission by
evaluating it against the minimum acceptance criteria (see evaluating it against the minimum acceptance criteria (see
Section 4.2.1) and against the log's discretionary acceptance Section 4.2.1) and against the log's discretionary acceptance
criteria (see Section 4.2.2). criteria (see Section 4.2.2).
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Logs SHOULD limit the length of chain they will accept. The maximum Logs SHOULD limit the length of chain they will accept. The maximum
chain length is one of the log's parameters (see Section 4.1). chain length is one of the log's parameters (see Section 4.1).
4.3. Log Entries 4.3. Log Entries
If a submission is accepted and an SCT issued, the accepting log MUST If a submission is accepted and an SCT issued, the accepting log MUST
store the entire chain used for verification. This chain MUST store the entire chain used for verification. This chain MUST
include the certificate or precertificate itself, the zero or more include the certificate or precertificate itself, the zero or more
intermediate CA certificates provided by the submitter, and the trust intermediate CA certificates provided by the submitter, and the trust
anchor used to verify the chain (even if it was omitted from the anchor used to verify the chain (even if it was omitted from the
submission). The log MUST present this chain for auditing upon submission). The log MUST provide this chain for auditing upon
request (see Section 5.6). This prevents the CA from avoiding blame request (see Section 5.6) so that the CA cannot avoid blame by
by logging a partial or empty chain. Each log entry is a "TransItem" logging a partial or empty chain. Each log entry is a "TransItem"
structure of type "x509_entry_v2" or "precert_entry_v2". However, a structure of type "x509_entry_v2" or "precert_entry_v2". However, a
log may store its entries in any format. If a log does not store log may store its entries in any format. If a log does not store
this "TransItem" in full, it must store the "timestamp" and this "TransItem" in full, it must store the "timestamp" and
"sct_extensions" of the corresponding "sct_extensions" of the corresponding
"TimestampedCertificateEntryDataV2" structure. The "TransItem" can "TimestampedCertificateEntryDataV2" structure. The "TransItem" can
be reconstructed from these fields and the entire chain that the log be reconstructed from these fields and the entire chain that the log
used to verify the submission. used to verify the submission.
4.4. Log ID 4.4. Log ID
Each log is identified by an OID, which is one of the log's Each log is identified by an OID, which is one of the log's
parameters (see Section 4.1) and which MUST NOT be used to identify parameters (see Section 4.1) and which MUST NOT be used to identify
any other log. A log's operator MUST either allocate the OID any other log. A log's operator MUST either allocate the OID
themselves or request an OID from the Log ID Registry (see themselves or request an OID from the Log ID Registry (see
Section 10.6.1). Various data structures include the DER encoding of Section 10.6.1). The only advantage of the registry is that the DER
this OID, excluding the ASN.1 tag and length bytes, in an opaque encoding can be small. (Recall that OID allocations do not require a
vector: central registration, although logs will most likely want to make
themselves known to potential clients through out of band means.)
Various data structures include the DER encoding of this OID,
excluding the ASN.1 tag and length bytes, in an opaque vector:
opaque LogID<2..127>; opaque LogID<2..127>;
Note that the ASN.1 length and the opaque vector length are identical Note that the ASN.1 length and the opaque vector length are identical
in size (1 byte) and value, so the DER encoding of the OID can be in size (1 byte) and value, so the full DER encoding (including the
reproduced simply by prepending an OBJECT IDENTIFIER tag (0x06) to tag and length) of the OID can be reproduced simply by prepending an
the opaque vector length and contents. OBJECT IDENTIFIER tag (0x06) to the opaque vector length and
contents.
OIDs used to identify logs are limited such that the DER encoding of The OID used to identify a log is limited such that the DER encoding
their value is less than or equal to 127 octets. of its value, excluding the tag and length, MUST be no longer than
127 octets.
4.5. TransItem Structure 4.5. TransItem Structure
Various data structures are encapsulated in the "TransItem" structure Various data structures are encapsulated in the "TransItem" structure
to ensure that the type and version of each one is identified in a to ensure that the type and version of each one is identified in a
common fashion: common fashion:
enum { enum {
reserved(0), reserved(0),
x509_entry_v2(1), precert_entry_v2(2), x509_entry_v2(1), precert_entry_v2(2),
skipping to change at page 24, line 19 skipping to change at page 24, line 19
impossible for the corresponding SCT to be valid for any other impossible for the corresponding SCT to be valid for any other
certificate or precertificate whose TBSCertificate matches certificate or precertificate whose TBSCertificate matches
"tbs_certificate". The length of the "issuer_key_hash" MUST match "tbs_certificate". The length of the "issuer_key_hash" MUST match
HASH_SIZE. HASH_SIZE.
"tbs_certificate" is the DER encoded TBSCertificate from the "tbs_certificate" is the DER encoded TBSCertificate from the
submission. (Note that a precertificate's TBSCertificate can be submission. (Note that a precertificate's TBSCertificate can be
reconstructed from the corresponding certificate as described in reconstructed from the corresponding certificate as described in
Section 8.1.2). Section 8.1.2).
"sct_extensions" matches the SCT extensions of the corresponding SCT. "sct_extensions" is byte-for-byte identical to the SCT extensions of
the corresponding SCT.
The type of the "TransItem" corresponds to the value of the "type" The type of the "TransItem" corresponds to the value of the "type"
parameter supplied in the Section 5.1 call. parameter supplied in the Section 5.1 call.
4.8. Signed Certificate Timestamp (SCT) 4.8. Signed Certificate Timestamp (SCT)
An SCT is a "TransItem" structure of type "x509_sct_v2" or An SCT is a "TransItem" structure of type "x509_sct_v2" or
"precert_sct_v2", which encapsulates a "precert_sct_v2", which encapsulates a
"SignedCertificateTimestampDataV2" structure: "SignedCertificateTimestampDataV2" structure:
struct { struct {
LogID log_id; LogID log_id;
uint64 timestamp; uint64 timestamp;
Extension sct_extensions<0..2^16-1>; Extension sct_extensions<0..2^16-1>;
opaque signature<0..2^16-1>; opaque signature<1..2^16-1>;
} SignedCertificateTimestampDataV2; } SignedCertificateTimestampDataV2;
"log_id" is this log's unique ID, encoded in an opaque vector as "log_id" is this log's unique ID, encoded in an opaque vector as
described in Section 4.4. described in Section 4.4.
"timestamp" is equal to the timestamp from the corresponding "timestamp" is equal to the timestamp from the corresponding
"TimestampedCertificateEntryDataV2" structure. "TimestampedCertificateEntryDataV2" structure.
"sct_extensions" is a vector of 0 or more SCT extensions. This "sct_extensions" is a vector of 0 or more SCT extensions. This
vector MUST NOT include more than one extension with the same vector MUST NOT include more than one extension with the same
"extension_type". The extensions in the vector MUST be ordered by "extension_type". The extensions in the vector MUST be ordered by
the value of the "extension_type" field, smallest value first. If an the value of the "extension_type" field, smallest value first. All
implementation sees an extension that it does not understand, it SCT extensions are similar to non-critical X.509v3 extensions (i.e.,
SHOULD ignore that extension. Furthermore, an implementation MAY the "mustUnderstand" field is not set), and a recipient SHOULD ignore
choose to ignore any extension(s) that it does understand. any extension it does not understand. Furthermore, an implementation
MAY choose to ignore any extension(s) that it does understand.
"signature" is computed over a "TransItem" structure of type "signature" is computed over a "TransItem" structure of type
"x509_entry_v2" or "precert_entry_v2" (see Section 4.7) using the "x509_entry_v2" or "precert_entry_v2" (see Section 4.7) using the
signature algorithm declared in the log's parameters (see signature algorithm declared in the log's parameters (see
Section 4.1). Section 4.1).
4.9. Merkle Tree Head 4.9. Merkle Tree Head
The log stores information about its Merkle Tree in a The log stores information about its Merkle Tree in a
"TreeHeadDataV2": "TreeHeadDataV2":
skipping to change at page 25, line 26 skipping to change at page 25, line 26
struct { struct {
uint64 timestamp; uint64 timestamp;
uint64 tree_size; uint64 tree_size;
NodeHash root_hash; NodeHash root_hash;
Extension sth_extensions<0..2^16-1>; Extension sth_extensions<0..2^16-1>;
} TreeHeadDataV2; } TreeHeadDataV2;
The length of NodeHash MUST match HASH_SIZE of the log. The length of NodeHash MUST match HASH_SIZE of the log.
"timestamp" is the current date and time, in the form of a 64-bit "timestamp" is the current date and time, using the format defined in
unsigned number of milliseconds elapsed since the Unix Epoch (1 {tree_leaves}.
January 1970 00:00:00 UTC - see [UNIXTIME]), ignoring leap seconds,
in network byte order.
"tree_size" is the number of entries currently in the log's Merkle "tree_size" is the number of entries currently in the log's Merkle
Tree. Tree.
"root_hash" is the root of the Merkle Hash Tree. "root_hash" is the root of the Merkle Hash Tree.
"sth_extensions" is a vector of 0 or more STH extensions. This "sth_extensions" is a vector of 0 or more STH extensions. This
vector MUST NOT include more than one extension with the same vector MUST NOT include more than one extension with the same
"extension_type". The extensions in the vector MUST be ordered by "extension_type". The extensions in the vector MUST be ordered by
the value of the "extension_type" field, smallest value first. If an the value of the "extension_type" field, smallest value first. If an
skipping to change at page 26, line 42 skipping to change at page 27, line 9
To prepare a Merkle Consistency Proof for distribution to clients, To prepare a Merkle Consistency Proof for distribution to clients,
the log produces a "TransItem" structure of type the log produces a "TransItem" structure of type
"consistency_proof_v2", which encapsulates a "ConsistencyProofDataV2" "consistency_proof_v2", which encapsulates a "ConsistencyProofDataV2"
structure: structure:
struct { struct {
LogID log_id; LogID log_id;
uint64 tree_size_1; uint64 tree_size_1;
uint64 tree_size_2; uint64 tree_size_2;
NodeHash consistency_path<1..2^16-1>; NodeHash consistency_path<0..2^16-1>;
} ConsistencyProofDataV2; } ConsistencyProofDataV2;
"log_id" is this log's unique ID, encoded in an opaque vector as "log_id" is this log's unique ID, encoded in an opaque vector as
described in Section 4.4. described in Section 4.4.
"tree_size_1" is the size of the older tree. "tree_size_1" is the size of the older tree.
"tree_size_2" is the size of the newer tree. "tree_size_2" is the size of the newer tree.
"consistency_path" is a vector of Merkle Tree nodes proving the "consistency_path" is a vector of Merkle Tree nodes proving the
consistency of two STHs. consistency of two STHs as described in {consistency}.
4.12. Merkle Inclusion Proofs 4.12. Merkle Inclusion Proofs
To prepare a Merkle Inclusion Proof for distribution to clients, the To prepare a Merkle Inclusion Proof for distribution to clients, the
log produces a "TransItem" structure of type "inclusion_proof_v2", log produces a "TransItem" structure of type "inclusion_proof_v2",
which encapsulates an "InclusionProofDataV2" structure: which encapsulates an "InclusionProofDataV2" structure:
struct { struct {
LogID log_id; LogID log_id;
uint64 tree_size; uint64 tree_size;
uint64 leaf_index; uint64 leaf_index;
NodeHash inclusion_path<1..2^16-1>; NodeHash inclusion_path<0..2^16-1>;
} InclusionProofDataV2; } InclusionProofDataV2;
"log_id" is this log's unique ID, encoded in an opaque vector as "log_id" is this log's unique ID, encoded in an opaque vector as
described in Section 4.4. described in Section 4.4.
"tree_size" is the size of the tree on which this inclusion proof is "tree_size" is the size of the tree on which this inclusion proof is
based. based.
"leaf_index" is the 0-based index of the log entry corresponding to "leaf_index" is the 0-based index of the log entry corresponding to
this inclusion proof. this inclusion proof.
"inclusion_path" is a vector of Merkle Tree nodes proving the "inclusion_path" is a vector of Merkle Tree nodes proving the
inclusion of the chosen certificate or precertificate. inclusion of the chosen certificate or precertificate as described in
{merkle_inclusion_proof}.
4.13. Shutting down a log 4.13. Shutting down a log
Log operators may decide to shut down a log for various reasons, such Log operators may decide to shut down a log for various reasons, such
as deprecation of the signature algorithm. If there are entries in as deprecation of the signature algorithm. If there are entries in
the log for certificates that have not yet expired, simply making TLS the log for certificates that have not yet expired, simply making TLS
clients stop recognizing that log will have the effect of clients stop recognizing that log will have the effect of
invalidating SCTs from that log. To avoid that, the following invalidating SCTs from that log. In order to avoid that, the
actions are suggested: following actions SHOULD be taken:
* Make it known to clients and monitors that the log will be frozen. * Make it known to clients and monitors that the log will be frozen.
This is not part of the API, so it will have to be done via a
relevant out-of-band mechanism.
* Stop accepting new submissions (the error code "shutdown" should * Stop accepting new submissions (the error code "shutdown" should
be returned for such requests). be returned for such requests).
* Once MMD from the last accepted submission has passed and all * Once MMD from the last accepted submission has passed and all
pending submissions are incorporated, issue a final STH and pending submissions are incorporated, issue a final STH and
publish it as one of the log's parameters. Having an STH with a publish it as one of the log's parameters. Having an STH with a
timestamp that is after the MMD has passed from the last SCT timestamp that is after the MMD has passed from the last SCT
issuance allows clients to audit this log regularly without issuance allows clients to audit this log regularly without
special handling for the final STH. At this point the log's special handling for the final STH. At this point the log's
skipping to change at page 28, line 25 skipping to change at page 28, line 41
scanning other logs or connecting to domains mentioned in the scanning other logs or connecting to domains mentioned in the
certificates and inspecting the SCTs served). certificates and inspecting the SCTs served).
5. Log Client Messages 5. Log Client Messages
Messages are sent as HTTPS GET or POST requests. Parameters for Messages are sent as HTTPS GET or POST requests. Parameters for
POSTs and all responses are encoded as JavaScript Object Notation POSTs and all responses are encoded as JavaScript Object Notation
(JSON) objects [RFC8259]. Parameters for GETs are encoded as order- (JSON) objects [RFC8259]. Parameters for GETs are encoded as order-
independent key/value URL parameters, using the "application/x-www- independent key/value URL parameters, using the "application/x-www-
form-urlencoded" format described in the "HTML 4.01 Specification" form-urlencoded" format described in the "HTML 4.01 Specification"
[HTML401]. Binary data is base64 encoded [RFC4648] as specified in [HTML401]. Binary data is base64 encoded according to section 4 of
the individual messages. [RFC4648] as specified in the individual messages.
Clients are configured with a log's base URL, which is one of the Clients are configured with a log's base URL, which is one of the
log's parameters. Clients construct URLs for requests by appending log's parameters. Clients construct URLs for requests by appending
suffixes to this base URL. This structure places some degree of suffixes to this base URL. This structure places some degree of
restriction on how log operators can deploy these services, as noted restriction on how log operators can deploy these services, as noted
in [RFC7320]. However, operational experience with version 1 of this in [RFC7320]. However, operational experience with version 1 of this
protocol has not indicated that these restrictions are a problem in protocol has not indicated that these restrictions are a problem in
practice. practice.
Note that JSON objects and URL parameters may contain fields not Note that JSON objects and URL parameters may contain fields not
specified here. These extra fields SHOULD be ignored. specified here, to allow for experimentation. Any fields that are
not understood SHOULD be ignored.
In practice, log servers may include multiple front-end machines. In practice, log servers may include multiple front-end machines.
Since it is impractical to keep these machines in perfect sync, Since it is impractical to keep these machines in perfect sync,
errors may occur that are caused by skew between the machines. Where errors may occur that are caused by skew between the machines. Where
such errors are possible, the front-end will return additional such errors are possible, the front-end will return additional
information (as specified below) making it possible for clients to information (as specified below) making it possible for clients to
make progress, if progress is possible. Front-ends MUST only serve make progress, if progress is possible. Front-ends MUST only serve
data that is free of gaps (that is, for example, no front-end will data that is free of gaps (that is, for example, no front-end will
respond with an STH unless it is also able to prove consistency from respond with an STH unless it is also able to prove consistency from
all log entries logged within that STH). all log entries logged within that STH).
skipping to change at page 29, line 51 skipping to change at page 30, line 24
| malformed | The request could not be parsed. | | malformed | The request could not be parsed. |
+-----------+----------------------------------+ +-----------+----------------------------------+
Table 1 Table 1
Clients SHOULD treat "500 Internal Server Error" and "503 Service Clients SHOULD treat "500 Internal Server Error" and "503 Service
Unavailable" responses as transient failures and MAY retry the same Unavailable" responses as transient failures and MAY retry the same
request without modification at a later date. Note that as per request without modification at a later date. Note that as per
[RFC7231], in the case of a 503 response the log MAY include a [RFC7231], in the case of a 503 response the log MAY include a
"Retry-After:" header in order to request a minimum time for the "Retry-After:" header in order to request a minimum time for the
client to wait before retrying the request. client to wait before retrying the request. In the absence of this
header, this document does not specify a minimum.
Clients SHOULD treat any 4xx error as a problem with the request and
not attempt to resubmit without some modification to the request.
The full status code MAY provide additional details.
This document deliberately does not provide more specific guidance on
the use of HTTP status codes.
5.1. Submit Entry to Log 5.1. Submit Entry to Log
POST <Base URL>/ct/v2/submit-entry POST <Base URL>/ct/v2/submit-entry
Inputs: submission: The base64 encoded certificate or Inputs: submission: The base64 encoded certificate or
precertificate. precertificate.
type: The "VersionedTransType" integer value that indicates type: The "VersionedTransType" integer value that indicates
the type of the "submission": 1 for "x509_entry_v2", or 2 for the type of the "submission": 1 for "x509_entry_v2", or 2 for
"precert_entry_v2". "precert_entry_v2".
chain: An array of zero or more base64 encoded CA chain: An array of zero or more JSON strings, each of which
certificates. The first element is the certifier of the is a base64 encoded CA certificate. The first element is the
"submission"; the second certifies the first; etc. The last certifier of the "submission"; the second certifies the first;
element of "chain" (or, if "chain" is an empty array, the etc. The last element of "chain" (or, if "chain" is an empty
"submission") is certified by an accepted trust anchor. array, the "submission") is certified by an accepted trust
anchor.
Outputs: sct: A base64 encoded "TransItem" of type "x509_sct_v2" or Outputs: sct: A base64 encoded "TransItem" of type "x509_sct_v2" or
"precert_sct_v2", signed by this log, that corresponds to the "precert_sct_v2", signed by this log, that corresponds to the
"submission". "submission".
If the submitted entry is immediately appended to (or already If the submitted entry is immediately appended to (or already
exists in) this log's tree, then the log SHOULD also output: exists in) this log's tree, then the log SHOULD also output:
sth: A base64 encoded "TransItem" of type "signed_tree_head_v2", sth: A base64 encoded "TransItem" of type "signed_tree_head_v2",
signed by this log. signed by this log.
skipping to change at page 31, line 44 skipping to change at page 32, line 14
If a log detects bad encoding in a chain that otherwise verifies If a log detects bad encoding in a chain that otherwise verifies
correctly then the log MUST either log the certificate or return the correctly then the log MUST either log the certificate or return the
"bad certificate" error. If the certificate is logged, an SCT MUST "bad certificate" error. If the certificate is logged, an SCT MUST
be issued. Logging the certificate is useful, because monitors be issued. Logging the certificate is useful, because monitors
(Section 8.2) can then detect these encoding errors, which may be (Section 8.2) can then detect these encoding errors, which may be
accepted by some TLS clients. accepted by some TLS clients.
If "submission" is an accepted trust anchor whose certifier is If "submission" is an accepted trust anchor whose certifier is
neither an accepted trust anchor nor the first element of "chain", neither an accepted trust anchor nor the first element of "chain",
then the log MUST return the "unknown anchor" error. A log cannot then the log MUST return the "unknown anchor" error. A log is not
generate an SCT for a submission if it does not have access to the able to generate an SCT for a submission if it does not have access
issuer's public key. to the issuer's public key.
If the returned "sct" is intended to be provided to TLS clients, then If the returned "sct" is intended to be provided to TLS clients, then
"sth" and "inclusion" (if returned) SHOULD also be provided to TLS "sth" and "inclusion" (if returned) SHOULD also be provided to TLS
clients (e.g., if "type" was 2 (for "precert_sct_v2") then all three clients. For example, if "type" was 2 (indicating "precert_sct_v2")
"TransItem"s could be embedded in the certificate). then all three "TransItem"s could be embedded in the certificate.
5.2. Retrieve Latest Signed Tree Head 5.2. Retrieve Latest Signed Tree Head
GET <Base URL>/ct/v2/get-sth GET <Base URL>/ct/v2/get-sth
No inputs. No inputs.
Outputs: sth: A base64 encoded "TransItem" of type Outputs: sth: A base64 encoded "TransItem" of type
"signed_tree_head_v2", signed by this log, that is no older "signed_tree_head_v2", signed by this log, that is no older
than the log's MMD. than the log's MMD.
skipping to change at page 33, line 31 skipping to change at page 33, line 46
5.4. Retrieve Merkle Inclusion Proof from Log by Leaf Hash 5.4. Retrieve Merkle Inclusion Proof from Log by Leaf Hash
GET <Base URL>/ct/v2/get-proof-by-hash GET <Base URL>/ct/v2/get-proof-by-hash
Inputs: hash: A base64 encoded v2 leaf hash. Inputs: hash: A base64 encoded v2 leaf hash.
tree_size: The tree_size of the tree on which to base the tree_size: The tree_size of the tree on which to base the
proof, in decimal. proof, in decimal.
The "hash" must be calculated as defined in Section 4.7. The The "hash" must be calculated as defined in Section 4.7. A v2 STH
"tree_size" must designate an existing v2 STH. Because of skew, must exist for the "tree_size". Because of skew, the front-end
the front-end may not know the requested STH. In that case, it may not know the requested tree head. In that case, it will
will return the latest STH it knows, along with an inclusion proof return the latest STH it knows, along with an inclusion proof to
to that STH. If the front-end knows the requested STH then only that STH. If the front-end knows the requested tree head then
"inclusion" is returned. only "inclusion" is returned.
Outputs: inclusion: A base64 encoded "TransItem" of type Outputs: inclusion: A base64 encoded "TransItem" of type
"inclusion_proof_v2" whose "inclusion_path" array of Merkle "inclusion_proof_v2" whose "inclusion_path" array of Merkle
Tree nodes proves the inclusion of the chosen certificate in Tree nodes proves the inclusion of the certificate (as
the selected STH. specified by the "hash" parameter) in the selected STH.
sth: A base64 encoded "TransItem" of type sth: A base64 encoded "TransItem" of type
"signed_tree_head_v2", signed by this log. "signed_tree_head_v2", signed by this log.
Note that no signature is required for the "inclusion" output as Note that no signature is required for the "inclusion" output as
it is used to verify inclusion in the selected STH, which is it is used to verify inclusion in the selected STH, which is
signed. signed.
Error codes: Error codes:
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5.5. Retrieve Merkle Inclusion Proof, Signed Tree Head and Consistency 5.5. Retrieve Merkle Inclusion Proof, Signed Tree Head and Consistency
Proof by Leaf Hash Proof by Leaf Hash
GET <Base URL>/ct/v2/get-all-by-hash GET <Base URL>/ct/v2/get-all-by-hash
Inputs: hash: A base64 encoded v2 leaf hash. Inputs: hash: A base64 encoded v2 leaf hash.
tree_size: The tree_size of the tree on which to base the tree_size: The tree_size of the tree on which to base the
proofs, in decimal. proofs, in decimal.
The "hash" must be calculated as defined in Section 4.7. The The "hash" must be calculated as defined in Section 4.7. A v2 STH
"tree_size" must designate an existing v2 STH. must exist for the "tree_size".
Because of skew, the front-end may not know the requested STH or the Because of skew, the front-end may not know the requested tree head
requested hash, which leads to a number of cases: or the requested hash, which leads to a number of cases:
+================+=====================================+ +=====================+=====================================+
| Case | Response | | Case | Response |
+================+=====================================+ +=====================+=====================================+
| latest STH < | Return latest STH | | latest STH < | Return latest STH |
| requested STH | | | requested tree head | |
+----------------+-------------------------------------+ +---------------------+-------------------------------------+
| latest STH > | Return latest STH and a consistency | | latest STH > | Return latest STH and a consistency |
| requested STH | proof between it and the requested | | requested tree head | proof between it and the requested |
| | STH (see Section 5.3) | | | tree head (see Section 5.3) |
+----------------+-------------------------------------+ +---------------------+-------------------------------------+
| index of | Return "inclusion" | | index of requested | Return "inclusion" |
| requested hash | | | hash < latest STH | |
| < latest STH | | +---------------------+-------------------------------------+
+----------------+-------------------------------------+
Table 5 Table 5
Note that more than one case can be true, in which case the returned Note that more than one case can be true, in which case the returned
data is their union. It is also possible for none to be true, in data is their union. It is also possible for none to be true, in
which case the front-end MUST return an empty response. which case the front-end MUST return an empty response.
Outputs: inclusion: A base64 encoded "TransItem" of type Outputs: inclusion: A base64 encoded "TransItem" of type
"inclusion_proof_v2" whose "inclusion_path" array of Merkle "inclusion_proof_v2" whose "inclusion_path" array of Merkle
Tree nodes proves the inclusion of the chosen certificate in Tree nodes proves the inclusion of the certificate (as
the returned STH. specified by the "hash" parameter) in the selected STH.
sth: A base64 encoded "TransItem" of type sth: A base64 encoded "TransItem" of type
"signed_tree_head_v2", signed by this log. "signed_tree_head_v2", signed by this log.
consistency: A base64 encoded "TransItem" of type consistency: A base64 encoded "TransItem" of type
"consistency_proof_v2" that proves the consistency of the "consistency_proof_v2" that proves the consistency of the
requested STH and the returned STH. requested tree head and the returned STH.
Note that no signature is required for the "inclusion" or Note that no signature is required for the "inclusion" or
"consistency" outputs as they are used to verify inclusion in and "consistency" outputs as they are used to verify inclusion in and
consistency of STHs, which are signed. consistency of STHs, which are signed.
Errors are the same as in Section 5.4. Errors are the same as in Section 5.4.
See Section 2.1.3.2 for an outline of how to use the "inclusion" See Section 2.1.3.2 for an outline of how to use the "inclusion"
output, and see Section 2.1.4.2 for an outline of how to use the output, and see Section 2.1.4.2 for an outline of how to use the
"consistency" output. "consistency" output.
skipping to change at page 36, line 13 skipping to change at page 36, line 12
Inputs: start: 0-based index of first entry to retrieve, in Inputs: start: 0-based index of first entry to retrieve, in
decimal. decimal.
end: 0-based index of last entry to retrieve, in decimal. end: 0-based index of last entry to retrieve, in decimal.
Outputs: entries: An array of objects, each consisting of Outputs: entries: An array of objects, each consisting of
log_entry: The base64 encoded "TransItem" structure of type log_entry: The base64 encoded "TransItem" structure of type
"x509_entry_v2" or "precert_entry_v2" (see Section 4.3). "x509_entry_v2" or "precert_entry_v2" (see Section 4.3).
submitted_entry: JSON object representing the inputs that were submitted_entry: JSON object equivalent to inputs that were
submitted to "submit-entry", with the addition of the trust submitted to "submit-entry", with the addition of the trust
anchor to the "chain" field if the submission did not anchor to the "chain" field if the submission did not
include it. include it.
sct: The base64 encoded "TransItem" of type "x509_sct_v2" or sct: The base64 encoded "TransItem" of type "x509_sct_v2" or
"precert_sct_v2" corresponding to this log entry. "precert_sct_v2" corresponding to this log entry.
sth: A base64 encoded "TransItem" of type sth: A base64 encoded "TransItem" of type
"signed_tree_head_v2", signed by this log. "signed_tree_head_v2", signed by this log.
skipping to change at page 37, line 9 skipping to change at page 37, line 5
Log servers MUST honor requests where 0 <= "start" < "tree_size" and Log servers MUST honor requests where 0 <= "start" < "tree_size" and
"end" >= "tree_size" by returning a partial response covering only "end" >= "tree_size" by returning a partial response covering only
the valid entries in the specified range. "end" >= "tree_size" could the valid entries in the specified range. "end" >= "tree_size" could
be caused by skew. Note that the following restriction may also be caused by skew. Note that the following restriction may also
apply: apply:
Logs MAY restrict the number of entries that can be retrieved per Logs MAY restrict the number of entries that can be retrieved per
"get-entries" request. If a client requests more than the permitted "get-entries" request. If a client requests more than the permitted
number of entries, the log SHALL return the maximum number of entries number of entries, the log SHALL return the maximum number of entries
permissible. These entries SHALL be sequential beginning with the permissible. These entries SHALL be sequential beginning with the
entry specified by "start". entry specified by "start". Note that limit on the number of entries
is not immutable and therefore the restriction may be changed or
lifted at any time and is not listed with the other Log Parameters in
Section 4.1.
Because of skew, it is possible the log server will not have any Because of skew, it is possible the log server will not have any
entries between "start" and "end". In this case it MUST return an entries between "start" and "end". In this case it MUST return an
empty "entries" array. empty "entries" array.
In any case, the log server MUST return the latest STH it knows In any case, the log server MUST return the latest STH it knows
about. about.
See Section 2.1.2 for an outline of how to use a complete list of See Section 2.1.2 for an outline of how to use a complete list of
"log_entry" entries to verify the "root_hash". "log_entry" entries to verify the "root_hash".
skipping to change at page 37, line 41 skipping to change at page 37, line 40
+----------------+------------------------------------+ +----------------+------------------------------------+
Table 6 Table 6
5.7. Retrieve Accepted Trust Anchors 5.7. Retrieve Accepted Trust Anchors
GET <Base URL>/ct/v2/get-anchors GET <Base URL>/ct/v2/get-anchors
No inputs. No inputs.
Outputs: certificates: An array of base64 encoded trust anchors Outputs: certificates: An array of JSON strings, each of which is a
that are acceptable to the log. base64 encoded CA certificate that is acceptable to the log.
max_chain_length:
max_chain_length: If the server has chosen to limit the If the server has chosen to limit the length of chains it
length of chains it accepts, this is the maximum number of accepts, this is the maximum number of certificates in the
certificates in the chain, in decimal. If there is no limit, chain, in decimal. If there is no limit, this is omitted.
this is omitted.
This data is not signed and the protocol depends on the security
guarantees of TLS to ensure correctness.
6. TLS Servers 6. TLS Servers
CT-using TLS servers MUST use at least one of the mechanisms CT-using TLS servers MUST use at least one of the mechanisms
described below to present one or more SCTs from one or more logs to described below to present one or more SCTs from one or more logs to
each TLS client during full TLS handshakes, where each SCT each TLS client during full TLS handshakes, where each SCT
corresponds to the server certificate. They SHOULD also present corresponds to the server certificate. (Of course, a server can only
corresponding inclusion proofs and STHs. send a TLS extension if the client has specified it first.) Servers
SHOULD also present corresponding inclusion proofs and STHs.
A server can provide SCTs using a TLS 1.3 extension (Section 4.2 of A server can provide SCTs using a TLS 1.3 extension (Section 4.2 of
[RFC8446]) with type "transparency_info" (see Section 6.5). This [RFC8446]) with type "transparency_info" (see Section 6.5). This
mechanism allows TLS servers to participate in CT without the mechanism allows TLS servers to participate in CT without the
cooperation of CAs, unlike the other two mechanisms. It also allows cooperation of CAs, unlike the other two mechanisms. It also allows
SCTs and inclusion proofs to be updated on the fly. SCTs and inclusion proofs to be updated on the fly.
The server may also use an Online Certificate Status Protocol (OCSP) The server may also use an Online Certificate Status Protocol (OCSP)
[RFC6960] response extension (see Section 7.1.1), providing the OCSP [RFC6960] response extension (see Section 7.1.1), providing the OCSP
response as part of the TLS handshake. Providing a response during a response as part of the TLS handshake. Providing a response during a
TLS handshake is popularly known as "OCSP stapling." For TLS 1.3, TLS handshake is popularly known as "OCSP stapling." For TLS 1.3,
the information is encoded as an extension in the "status_request" the information is encoded as an extension in the "status_request"
extension data; see Section 4.4.2.1 of [RFC8446]. For TLS 1.2, the extension data; see Section 4.4.2.1 of [RFC8446]. For TLS 1.2
information is encoded as an extension in the "CertificateStatus" ([RFC5246]), the information is encoded as an extension in the
message; see Section 8 of [RFC6066]. Using stapling also allows SCTs "CertificateStatus" message; see Section 8 of [RFC6066]. Using
and inclusion proofs to be updated on the fly. stapling also allows SCTs and inclusion proofs to be updated on the
fly.
CT information can also be encoded as an extension in the X.509v3 CT information can also be encoded as an extension in the X.509v3
certificate (see Section 7.1.2). This mechanism allows the use of certificate (see Section 7.1.2). This mechanism allows the use of
unmodified TLS servers, but the SCTs and inclusion proofs cannot be unmodified TLS servers, but the SCTs and inclusion proofs cannot be
updated on the fly. Since the logs from which the SCTs and inclusion updated on the fly. Since the logs from which the SCTs and inclusion
proofs originated won't necessarily be accepted by TLS clients for proofs originated won't necessarily be accepted by TLS clients for
the full lifetime of the certificate, there is a risk that TLS the full lifetime of the certificate, there is a risk that TLS
clients may subsequently consider the certificate to be non-compliant clients may subsequently consider the certificate to be non-compliant
and in need of re-issuance or the use of one of the other two methods and in need of re-issuance or the use of one of the other two methods
for delivering CT information. for delivering CT information.
skipping to change at page 39, line 10 skipping to change at page 39, line 12
submitted to CT logs, particularly those intended for general submitted to CT logs, particularly those intended for general
public use. public use.
A future version could include such information. A future version could include such information.
6.2. Multiple SCTs 6.2. Multiple SCTs
CT-using TLS servers SHOULD send SCTs from multiple logs, because: CT-using TLS servers SHOULD send SCTs from multiple logs, because:
* One or more logs may not have become acceptable to all CT-using * One or more logs may not have become acceptable to all CT-using
TLS clients. TLS clients. Note that client discovery, trust, and distrust of
logs is expected to be handled out-of-band and is out of scope of
this document.
* If a CA and a log collude, it is possible to temporarily hide * If a CA and a log collude, it is possible to temporarily hide
misissuance from clients. When a TLS client requires SCTs from misissuance from clients. When a TLS client requires SCTs from
multiple logs to be provided, it is more difficult to mount this multiple logs to be provided, it is more difficult to mount this
attack. attack.
* If a log misbehaves or suffers a key compromise, a consequence may * If a log misbehaves or suffers a key compromise, a consequence may
be that clients cease to trust it. Since the time an SCT may be be that clients cease to trust it. Since the time an SCT may be
in use can be considerable (several years is common in current in use can be considerable (several years is common in current
practice when embedded in a certificate), including SCTs from practice when embedded in a certificate), including SCTs from
skipping to change at page 40, line 7 skipping to change at page 40, line 14
Here, "SerializedTransItem" is an opaque byte string that contains Here, "SerializedTransItem" is an opaque byte string that contains
the serialized "TransItem" structure. This encoding ensures that TLS the serialized "TransItem" structure. This encoding ensures that TLS
clients can decode each "TransItem" individually (so, for example, if clients can decode each "TransItem" individually (so, for example, if
there is a version upgrade, out-of-date clients can still parse old there is a version upgrade, out-of-date clients can still parse old
"TransItem" structures while skipping over new "TransItem" structures "TransItem" structures while skipping over new "TransItem" structures
whose versions they don't understand). whose versions they don't understand).
6.4. Presenting SCTs, inclusions proofs and STHs 6.4. Presenting SCTs, inclusions proofs and STHs
In each "TransItemList" that is sent to a client during a TLS In each "TransItemList" that is sent during a TLS handshake, the TLS
handshake, the TLS server MUST include a "TransItem" structure of server MUST include a "TransItem" structure of type "x509_sct_v2" or
type "x509_sct_v2" or "precert_sct_v2". "precert_sct_v2".
Presenting inclusion proofs and STHs in the TLS handshake helps to Presenting inclusion proofs and STHs in the TLS handshake helps to
protect the client's privacy (see Section 8.1.4) and reduces load on protect the client's privacy (see Section 8.1.4) and reduces load on
log servers. Therefore, if the TLS server can obtain them, it SHOULD log servers. Therefore, if the TLS server can obtain them, it SHOULD
also include "TransItem"s of type "inclusion_proof_v2" and also include "TransItem"s of type "inclusion_proof_v2" and
"signed_tree_head_v2" in the "TransItemList". "signed_tree_head_v2" in the "TransItemList".
6.5. transparency_info TLS Extension 6.5. transparency_info TLS Extension
Provided that a TLS client includes the "transparency_info" extension Provided that a TLS client includes the "transparency_info" extension
skipping to change at page 40, line 32 skipping to change at page 40, line 39
* The TLS server MUST verify that the received "extension_data" is * The TLS server MUST verify that the received "extension_data" is
empty. empty.
* The TLS server MUST construct a "TransItemList" of relevant * The TLS server MUST construct a "TransItemList" of relevant
"TransItem"s (see Section 6.4), which SHOULD omit any "TransItem"s "TransItem"s (see Section 6.4), which SHOULD omit any "TransItem"s
that are already embedded in the server certificate or the stapled that are already embedded in the server certificate or the stapled
OCSP response (see Section 7.1). If the constructed OCSP response (see Section 7.1). If the constructed
"TransItemList" is not empty, then the TLS server MUST include the "TransItemList" is not empty, then the TLS server MUST include the
"transparency_info" extension with the "extension_data" set to "transparency_info" extension with the "extension_data" set to
this "TransItemList". this "TransItemList". If the list is empty then the server SHOULD
omit the "extension_data" element, but MAY send it with an empty
array.
TLS servers MUST only include this extension in the following TLS servers MUST only include this extension in the following
messages: messages:
* the ServerHello message (for TLS 1.2 or earlier). * the ServerHello message (for TLS 1.2 or earlier).
* the Certificate or CertificateRequest message (for TLS 1.3). * the Certificate or CertificateRequest message (for TLS 1.3).
TLS servers MUST NOT process or include this extension when a TLS TLS servers MUST NOT process or include this extension when a TLS
session is resumed, since session resumption uses the original session is resumed, since session resumption uses the original
skipping to change at page 44, line 49 skipping to change at page 44, line 49
4. If applicable, check each entry to see if it's a certificate of 4. If applicable, check each entry to see if it's a certificate of
interest. interest.
5. Confirm that the tree made from the fetched entries produces the 5. Confirm that the tree made from the fetched entries produces the
same hash as that in the STH. same hash as that in the STH.
To inspect new entries, the monitor SHOULD follow these steps To inspect new entries, the monitor SHOULD follow these steps
repeatedly for each log: repeatedly for each log:
1. Fetch the current STH (Section 5.2). Repeat until the STH 1. Fetch the current STH (Section 5.2). Repeat until the STH
changes. changes. This document does not specify the polling frequency,
to allow for experimentation.
2. Verify the STH signature. 2. Verify the STH signature.
3. Fetch all the new entries in the tree corresponding to the STH 3. Fetch all the new entries in the tree corresponding to the STH
(Section 5.6). If they remain unavailable for an extended (Section 5.6). If they remain unavailable for an extended
period, then this should be viewed as misbehavior on the part of period, then this should be viewed as misbehavior on the part of
the log. the log.
4. If applicable, check each entry to see if it's a certificate of 4. If applicable, check each entry to see if it's a certificate of
interest. interest.
skipping to change at page 47, line 48 skipping to change at page 47, line 48
| 0xEF | | | | | 0xEF | | | |
+--------+------------+------------------------+-------------------+ +--------+------------+------------------------+-------------------+
| 0xF0 - | Reserved | | Private Use | | 0xF0 - | Reserved | | Private Use |
| 0xFF | | | | | 0xFF | | | |
+--------+------------+------------------------+-------------------+ +--------+------------+------------------------+-------------------+
Table 7 Table 7
10.2.1. Specification Required guidance 10.2.1. Specification Required guidance
The appointed Expert should ensure that the proposed algorithm has a The appointed Expert(s) should ensure that the proposed algorithm has
public specification and is suitable for use as a cryptographic hash a public specification and is suitable for use as a cryptographic
algorithm with no known preimage or collision attacks. These attacks hash algorithm with no known preimage or collision attacks. These
can damage the integrity of the log. attacks can damage the integrity of the log.
10.3. Signature Algorithms 10.3. Signature Algorithms
IANA is asked to establish a registry of signature algorithm values, IANA is asked to establish a registry of signature algorithm values,
named "CT Signature Algorithms", that initially consists of: named "CT Signature Algorithms"
The following notes should be added:
* This is a subset of the TLS SignatureScheme Registry, limited to
those algorithms that are appropriate for CT. A major advantage
of this is leveraging the expertise of the TLS working group and
its designated experts.
* The value "0x0403" appears twice. While this may be confusing, it
is okay because the verification process is the same for both
algorithms, and the choice of which to use when generating a
signature is purely internal to the log server.
The registry should initially consist of:
+================================+==================+==============+ +================================+==================+==============+
| SignatureScheme Value | Signature | Reference / | | SignatureScheme Value | Signature | Reference / |
| | Algorithm | Assignment | | | Algorithm | Assignment |
| | | Policy | | | | Policy |
+================================+==================+==============+ +================================+==================+==============+
| 0x0000 - 0x0402 | Unassigned | Expert | | 0x0000 - 0x0402 | Unassigned | Expert |
| | | Review | | | | Review |
+--------------------------------+------------------+--------------+ +--------------------------------+------------------+--------------+
| ecdsa_secp256r1_sha256(0x0403) | ECDSA (NIST | [FIPS186-4] | | ecdsa_secp256r1_sha256(0x0403) | ECDSA (NIST | [FIPS186-4] |
skipping to change at page 49, line 42 skipping to change at page 50, line 37
| 0xE000 - | Reserved | Experimental Use | | 0xE000 - | Reserved | Experimental Use |
| 0xEFFF | | | | 0xEFFF | | |
+----------+----------------------+-------------------------------+ +----------+----------------------+-------------------------------+
| 0xF000 - | Reserved | Private Use | | 0xF000 - | Reserved | Private Use |
| 0xFFFF | | | | 0xFFFF | | |
+----------+----------------------+-------------------------------+ +----------+----------------------+-------------------------------+
Table 9 Table 9
* The 0x0000 value is reserved so that v1 SCTs are distinguishable * The 0x0000 value is reserved so that v1 SCTs are distinguishable
from v2 SCTs and other "TransItem" structures. from v2 SCTs and other "TransItem" structures. ### Specification
Required guidance
[RFC Editor: please update 'RFCXXXX' to refer to this document, once
its RFC number is known through the document.]
10.4.1. Specification Required guidance
The appointed Expert should review the public specification to ensure The appointed Expert should review the public specification to ensure
that it is detailed enough to ensure implementation interoperability. that it is detailed enough to ensure implementation interoperability.
10.5. Log Artifact Extension Registry 10.5. Log Artifact Extension Registry
IANA is asked to establish a registry of "ExtensionType" values, IANA is asked to establish a registry of "ExtensionType" values,
named "CT Log Artifact Extensions", that initially consists of: named "CT Log Artifact Extensions", that initially consists of:
+===============+============+=====+===============================+ +===============+============+=====+===============================+
skipping to change at page 51, line 19 skipping to change at page 52, line 19
| 1.3.101.8192 - | Unassigned | Unassigned | First Come First | | 1.3.101.8192 - | Unassigned | Unassigned | First Come First |
| 1.3.101.16383 | | | Served | | 1.3.101.16383 | | | Served |
+----------------+--------------+--------------+-------------------+ +----------------+--------------+--------------+-------------------+
| 1.3.101.80.0 - | Unassigned | Unassigned | First Come First | | 1.3.101.80.0 - | Unassigned | Unassigned | First Come First |
| 1.3.101.80.* | | | Served | | 1.3.101.80.* | | | Served |
+----------------+--------------+--------------+-------------------+ +----------------+--------------+--------------+-------------------+
Table 11 Table 11
All OIDs in the range from 1.3.101.8192 to 1.3.101.16383 have been All OIDs in the range from 1.3.101.8192 to 1.3.101.16383 have been
reserved. This is a limited resource of 8,192 OIDs, each of which set aside for Log IDs. This is a limited resource of 8,192 OIDs,
has an encoded length of 4 octets. each of which has an encoded length of 4 octets.
The 1.3.101.80 arc has been delegated. This is an unlimited The 1.3.101.80 arc has also been set assigned for LogIDs. This is an
resource, but only the 128 OIDs from 1.3.101.80.0 to 1.3.101.80.127 unlimited resource, but only the 128 OIDs from 1.3.101.80.0 to
have an encoded length of only 4 octets. 1.3.101.80.127 have an encoded length of only 4 octets.
Each application for the allocation of a Log ID MUST be accompanied Each application for the allocation of a Log ID MUST be accompanied
by: by:
* the Log's Base URL (see Section 4.1). * the Log's Base URL (see Section 4.1).
* the Log Operator's contact details. * the Log Operator's contact details.
IANA is asked to reject any request to update a Log ID or Log Base IANA is asked to reject any request to update a Log ID or Log Base
URL in this registry, because these fields are immutable (see URL in this registry, because these fields are immutable (see
skipping to change at page 54, line 14 skipping to change at page 55, line 14
A signed timestamp does not guarantee this though, since appropriate A signed timestamp does not guarantee this though, since appropriate
monitors might not have checked the logs or the CA might have refused monitors might not have checked the logs or the CA might have refused
to revoke the certificate. to revoke the certificate.
In addition, if TLS clients will not accept unlogged certificates, In addition, if TLS clients will not accept unlogged certificates,
then site owners will have a greater incentive to submit certificates then site owners will have a greater incentive to submit certificates
to logs, possibly with the assistance of their CA, increasing the to logs, possibly with the assistance of their CA, increasing the
overall transparency of the system. overall transparency of the system.
[I-D.ietf-trans-threat-analysis] provides a more detailed threat
analysis of the Certificate Transparency architecture.
11.1. Misissued Certificates 11.1. Misissued Certificates
Misissued certificates that have not been publicly logged, and thus Misissued certificates that have not been publicly logged, and thus
do not have a valid SCT, are not considered compliant. Misissued do not have a valid SCT, are not considered compliant. Misissued
certificates that do have an SCT from a log will appear in that certificates that do have an SCT from a log will appear in that
public log within the Maximum Merge Delay, assuming the log is public log within the Maximum Merge Delay, assuming the log is
operating correctly. Since a log is allowed to serve an STH of any operating correctly. Since a log is allowed to serve an STH of any
age up to the MMD, the maximum period of time during which a age up to the MMD, the maximum period of time during which a
misissued certificate can be used without being available for audit misissued certificate can be used without being available for audit
is twice the MMD. is twice the MMD.
skipping to change at page 54, line 42 skipping to change at page 55, line 39
and take corrective action when a misissue is detected. and take corrective action when a misissue is detected.
11.3. Misbehaving Logs 11.3. Misbehaving Logs
A log can misbehave in several ways. Examples include: failing to A log can misbehave in several ways. Examples include: failing to
incorporate a certificate with an SCT in the Merkle Tree within the incorporate a certificate with an SCT in the Merkle Tree within the
MMD; presenting different, conflicting views of the Merkle Tree at MMD; presenting different, conflicting views of the Merkle Tree at
different times and/or to different parties; issuing STHs too different times and/or to different parties; issuing STHs too
frequently; mutating the signature of a logged certificate; and frequently; mutating the signature of a logged certificate; and
failing to present a chain containing the certifier of a logged failing to present a chain containing the certifier of a logged
certificate. Such misbehavior is detectable and certificate.
[I-D.ietf-trans-threat-analysis] provides more details on how this
can be done.
Violation of the MMD contract is detected by log clients requesting a Violation of the MMD contract is detected by log clients requesting a
Merkle inclusion proof (Section 5.4) for each observed SCT. These Merkle inclusion proof (Section 5.4) for each observed SCT. These
checks can be asynchronous and need only be done once per checks can be asynchronous and need only be done once per
certificate. However, note that there may be privacy concerns (see certificate. However, note that there may be privacy concerns (see
Section 8.1.4). Section 8.1.4).
Violation of the append-only property or the STH issuance rate limit Violation of the append-only property or the STH issuance rate limit
can be detected by clients comparing their instances of the Signed can be detected by multiple clients comparing their instances of the
Tree Heads. There are various ways this could be done, for example Signed Tree Heads. This technique, known as "gossip," is an active
via gossip (see [I-D.ietf-trans-gossip]) or peer-to-peer area of research and not defined here. Proof of misbehavior in such
communications or by sending STHs to monitors (who could then cases would be: a series of STHs that were issued too closely
directly check against their own copy of the relevant log). Proof of together, proving violation of the STH issuance rate limit; or an STH
misbehavior in such cases would be: a series of STHs that were issued with a root hash that does not match the one calculated from a copy
too closely together, proving violation of the STH issuance rate of the log, proving violation of the append-only property.
limit; or an STH with a root hash that does not match the one
calculated from a copy of the log, proving violation of the append-
only property.
11.4. Preventing Tracking Clients
Clients that gossip STHs or report back SCTs can be tracked or traced Clients that report back SCTs can be tracked or traced if a log
if a log produces multiple STHs or SCTs with the same timestamp and produces multiple STHs or SCTs with the same timestamp and data but
data but different signatures. Logs SHOULD mitigate this risk by different signatures. Logs SHOULD mitigate this risk by either:
either:
* Using deterministic signature schemes, or * Using deterministic signature schemes, or
* Producing no more than one SCT for each distinct submission and no * Producing no more than one SCT for each distinct submission and no
more than one STH for each distinct tree_size. Each of these SCTs more than one STH for each distinct tree_size. Each of these SCTs
and STHs can be stored by the log and served to other clients that and STHs can be stored by the log and served to other clients that
submit the same certificate or request the same STH. submit the same certificate or request the same STH.
11.5. Multiple SCTs 11.4. Multiple SCTs
By requiring TLS servers to offer multiple SCTs, each from a By requiring TLS servers to offer multiple SCTs, each from a
different log, TLS clients reduce the effectiveness of an attack different log, TLS clients reduce the effectiveness of an attack
where a CA and a log collude (see Section 6.2). where a CA and a log collude (see Section 6.2).
11.6. Leakage of DNS Information 11.5. Leakage of DNS Information
Malicious monitors can use logs to learn about the existence of Malicious monitors can use logs to learn about the existence of
domain names that might not otherwise be easy to discover. Some domain names that might not otherwise be easy to discover. Some
subdomain labels may reveal information about the service and subdomain labels may reveal information about the service and
software for which the subdomain is used, which in turn might software for which the subdomain is used, which in turn might
facilitate targeted attacks. facilitate targeted attacks.
12. Acknowledgements 12. Acknowledgements
The authors would like to thank Erwann Abelea, Robin Alden, Andrew The authors would like to thank Erwann Abelea, Robin Alden, Andrew
skipping to change at page 56, line 34 skipping to change at page 57, line 29
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
IETF URN Sub-namespace for Registered Protocol IETF URN Sub-namespace for Registered Protocol
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
2003, <https://www.rfc-editor.org/info/rfc3553>. 2003, <https://www.rfc-editor.org/info/rfc3553>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>. <https://www.rfc-editor.org/info/rfc4648>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009, RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>. <https://www.rfc-editor.org/info/rfc5652>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066, Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011, DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>. <https://www.rfc-editor.org/info/rfc6066>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., [RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP", Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013, RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>. <https://www.rfc-editor.org/info/rfc6960>.
[RFC6979] Pornin, T., "Deterministic Usage of the Digital Signature
Algorithm (DSA) and Elliptic Curve Digital Signature
Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, August
2013, <https://www.rfc-editor.org/info/rfc6979>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC7633] Hallam-Baker, P., "X.509v3 Transport Layer Security (TLS) [RFC7633] Hallam-Baker, P., "X.509v3 Transport Layer Security (TLS)
Feature Extension", RFC 7633, DOI 10.17487/RFC7633, Feature Extension", RFC 7633, DOI 10.17487/RFC7633,
October 2015, <https://www.rfc-editor.org/info/rfc7633>. October 2015, <https://www.rfc-editor.org/info/rfc7633>.
[RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
skipping to change at page 57, line 38 skipping to change at page 59, line 5
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259, Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017, DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>. <https://www.rfc-editor.org/info/rfc8259>.
[RFC8391] Huelsing, A., Butin, D., Gazdag, S., Rijneveld, J., and A.
Mohaisen, "XMSS: eXtended Merkle Signature Scheme",
RFC 8391, DOI 10.17487/RFC8391, May 2018,
<https://www.rfc-editor.org/info/rfc8391>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
[UNIXTIME] IEEE, "The Open Group Base Specifications Issue 7 IEEE Std [UNIXTIME] IEEE, "The Open Group Base Specifications Issue 7 IEEE Std
1003.1-2008, 2016 Edition", n.d., 1003.1-2008, 2016 Edition", n.d.,
<http://pubs.opengroup.org/ <http://pubs.opengroup.org/
onlinepubs/9699919799.2016edition/basedefs/ onlinepubs/9699919799.2016edition/basedefs/
V1_chap04.html#tag_04_16>. V1_chap04.html#tag_04_16>.
[X690] ITU-T, "Information technology - ASN.1 encoding Rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ISO/IEC 8825-1:2002, November 2015.
13.2. Informative References 13.2. Informative References
[CABBR] CA/Browser Forum, "Baseline Requirements for the Issuance
and Management of Publicly-Trusted Certificates", 2020,
<https://cabforum.org/wp-content/uploads/CA-Browser-Forum-
BR-1.7.3.pdf>.
[Chromium.Log.Policy] [Chromium.Log.Policy]
The Chromium Projects, "Chromium Certificate Transparency The Chromium Projects, "Chromium Certificate Transparency
Log Policy", 2014, <http://www.chromium.org/Home/chromium- Log Policy", 2014, <http://www.chromium.org/Home/chromium-
security/certificate-transparency/log-policy>. security/certificate-transparency/log-policy>.
[Chromium.Policy] [Chromium.Policy]
The Chromium Projects, "Chromium Certificate The Chromium Projects, "Chromium Certificate
Transparency", 2014, <http://www.chromium.org/Home/ Transparency", 2014, <http://www.chromium.org/Home/
chromium-security/certificate-transparency>. chromium-security/certificate-transparency>.
[CrosbyWallach] [CrosbyWallach]
Crosby, S. and D. Wallach, "Efficient Data Structures for Crosby, S. and D. Wallach, "Efficient Data Structures for
Tamper-Evident Logging", Proceedings of the 18th USENIX Tamper-Evident Logging", Proceedings of the 18th USENIX
Security Symposium, Montreal, August 2009, Security Symposium, Montreal, August 2009,
<http://static.usenix.org/event/sec09/tech/full_papers/ <http://static.usenix.org/event/sec09/tech/full_papers/
crosby.pdf>. crosby.pdf>.
[I-D.ietf-trans-gossip]
Nordberg, L., Gillmor, D. K., and T. Ritter, "Gossiping in
CT", Work in Progress, Internet-Draft, draft-ietf-trans-
gossip-05, 14 January 2018,
<https://www.ietf.org/archive/id/draft-ietf-trans-gossip-
05.txt>.
[I-D.ietf-trans-threat-analysis]
Kent, S., "Attack and Threat Model for Certificate
Transparency", Work in Progress, Internet-Draft, draft-
ietf-trans-threat-analysis-16, 5 October 2018,
<https://www.ietf.org/archive/id/draft-ietf-trans-threat-
analysis-16.txt>.
[JSON.Metadata] [JSON.Metadata]
The Chromium Projects, "Chromium Log Metadata JSON The Chromium Projects, "Chromium Log Metadata JSON
Schema", 2014, <https://www.gstatic.com/ct/log_list/ Schema", 2014, <https://www.gstatic.com/ct/log_list/
log_list_schema.json>. log_list_schema.json>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate [RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate
Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013, Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
<https://www.rfc-editor.org/info/rfc6962>. <https://www.rfc-editor.org/info/rfc6962>.
[RFC6979] Pornin, T., "Deterministic Usage of the Digital Signature
Algorithm (DSA) and Elliptic Curve Digital Signature
Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, August
2013, <https://www.rfc-editor.org/info/rfc6979>.
[RFC7320] Nottingham, M., "URI Design and Ownership", RFC 7320, [RFC7320] Nottingham, M., "URI Design and Ownership", RFC 7320,
DOI 10.17487/RFC7320, July 2014, DOI 10.17487/RFC7320, July 2014,
<https://www.rfc-editor.org/info/rfc7320>. <https://www.rfc-editor.org/info/rfc7320>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Supporting v1 and v2 simultaneously Appendix A. Supporting v1 and v2 simultaneously (Informative)
Certificate Transparency logs have to be either v1 (conforming to Certificate Transparency logs have to be either v1 (conforming to
[RFC6962]) or v2 (conforming to this document), as the data [RFC6962]) or v2 (conforming to this document), as the data
structures are incompatible and so a v2 log could not issue a valid structures are incompatible and so a v2 log could not issue a valid
v1 SCT. v1 SCT.
CT clients, however, can support v1 and v2 SCTs, for the same CT clients, however, can support v1 and v2 SCTs, for the same
certificate, simultaneously, as v1 SCTs are delivered in different certificate, simultaneously, as v1 SCTs are delivered in different
TLS, X.509 and OCSP extensions than v2 SCTs. TLS, X.509 and OCSP extensions than v2 SCTs.
skipping to change at page 60, line 5 skipping to change at page 61, line 5
* Use that TBSCertificate to create a v1 precertificate, as * Use that TBSCertificate to create a v1 precertificate, as
described in Section 3.1. of [RFC6962] and submit it to v1 logs. described in Section 3.1. of [RFC6962] and submit it to v1 logs.
* Embed the v1 SCTs in the TBSCertificate, as described in * Embed the v1 SCTs in the TBSCertificate, as described in
Section 3.3 of [RFC6962]. Section 3.3 of [RFC6962].
* Sign that TBSCertificate (which now contains v1 and v2 SCTs) to * Sign that TBSCertificate (which now contains v1 and v2 SCTs) to
issue the final X.509 certificate. issue the final X.509 certificate.
Appendix B. An ASN.1 Module (Informative)
The following ASN.1 module may be useful to implementors.
CertificateTransparencyV2Module-2021
-- { OID Needed, but no point in using a short one }
DEFINITIONS IMPLICIT TAGS ::= BEGIN
-- EXPORTS ALL --
IMPORTS
EXTENSION
FROM PKIX-CommonTypes-2009 -- RFC 5912
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkixCommon-02(57) }
CONTENT-TYPE
FROM CryptographicMessageSyntax-2010 -- RFC 6268
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) }
TBSCertificate
FROM PKIX1Explicit-2009 -- RFC 5912
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-explicit-02(51) }
;
--
-- Section 3.2. Precertificates
--
ct-tbsCertificate CONTENT-TYPE ::= {
TYPE TBSCertificate
IDENTIFIED BY id-ct-tbsCertificate }
id-ct-tbsCertificate OBJECT IDENTIFIER ::= { 1 3 101 78 }
--
-- Section 7.1. Transparency Information X.509v3 Extension
--
ext-transparencyInfo EXTENSION ::= {
SYNTAX TransparencyInformationSyntax
IDENTIFIED BY id-ce-transparencyInfo
CRITICALITY { FALSE } }
id-ce-transparencyInfo OBJECT IDENTIFIER ::= { 1 3 101 75 }
TransparencyInformationSyntax ::= OCTET STRING
--
-- Section 7.1.1. OCSP Response Extension
--
ext-ocsp-transparencyInfo EXTENSION ::= {
SYNTAX TransparencyInformationSyntax
IDENTIFIED BY id-pkix-ocsp-transparencyInfo
CRITICALITY { FALSE } }
id-pkix-ocsp-transparencyInfo OBJECT IDENTIFIER ::=
id-ce-transparencyInfo
--
-- Section 8.1.2. Reconstructing the TBSCertificate
--
ext-embeddedSCT-CTv1 EXTENSION ::= {
SYNTAX SignedCertificateTimestampList
IDENTIFIED BY id-ce-embeddedSCT-CTv1
CRITICALITY { FALSE } }
id-ce-embeddedSCT-CTv1 OBJECT IDENTIFIER ::= {
1 3 6 1 4 1 11129 2 4 2 }
SignedCertificateTimestampList ::= OCTET STRING
END
Authors' Addresses Authors' Addresses
Ben Laurie Ben Laurie
Google UK Ltd. Google UK Ltd.
Email: benl@google.com Email: benl@google.com
Adam Langley Adam Langley
Google Inc. Google Inc.
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