draft-ietf-tls-tls13-10.txt   draft-ietf-tls-tls13-11.txt 
Network Working Group E. Rescorla Network Working Group E. Rescorla
Internet-Draft RTFM, Inc. Internet-Draft RTFM, Inc.
Obsoletes: 5077, 5246, 5746 (if October 19, 2015 Obsoletes: 5077, 5246, 5746 (if December 28, 2015
approved) approved)
Updates: 4492 (if approved) Updates: 4492 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: April 21, 2016 Expires: June 30, 2016
The Transport Layer Security (TLS) Protocol Version 1.3 The Transport Layer Security (TLS) Protocol Version 1.3
draft-ietf-tls-tls13-10 draft-ietf-tls-tls13-11
Abstract Abstract
This document specifies Version 1.3 of the Transport Layer Security This document specifies Version 1.3 of the Transport Layer Security
(TLS) protocol. The TLS protocol allows client/server applications (TLS) protocol. The TLS protocol allows client/server applications
to communicate over the Internet in a way that is designed to prevent to communicate over the Internet in a way that is designed to prevent
eavesdropping, tampering, and message forgery. eavesdropping, tampering, and message forgery.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on April 21, 2016. This Internet-Draft will expire on June 30, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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 Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions and Terminology . . . . . . . . . . . . . . . 5 1.1. Conventions and Terminology . . . . . . . . . . . . . . . 5
1.2. Major Differences from TLS 1.2 . . . . . . . . . . . . . 6 1.2. Major Differences from TLS 1.2 . . . . . . . . . . . . . 6
2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3. Goals of This Document . . . . . . . . . . . . . . . . . . . 9 3. Goals of This Document . . . . . . . . . . . . . . . . . . . 9
4. Presentation Language . . . . . . . . . . . . . . . . . . . . 9 4. Presentation Language . . . . . . . . . . . . . . . . . . . . 10
4.1. Basic Block Size . . . . . . . . . . . . . . . . . . . . 10 4.1. Basic Block Size . . . . . . . . . . . . . . . . . . . . 10
4.2. Miscellaneous . . . . . . . . . . . . . . . . . . . . . . 10 4.2. Miscellaneous . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Vectors . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.3. Vectors . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.4. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.5. Enumerateds . . . . . . . . . . . . . . . . . . . . . . . 12 4.5. Enumerateds . . . . . . . . . . . . . . . . . . . . . . . 12
4.6. Constructed Types . . . . . . . . . . . . . . . . . . . . 12 4.6. Constructed Types . . . . . . . . . . . . . . . . . . . . 13
4.6.1. Variants . . . . . . . . . . . . . . . . . . . . . . 13 4.6.1. Variants . . . . . . . . . . . . . . . . . . . . . . 13
4.7. Constants . . . . . . . . . . . . . . . . . . . . . . . . 14 4.7. Constants . . . . . . . . . . . . . . . . . . . . . . . . 14
4.8. Primitive Types . . . . . . . . . . . . . . . . . . . . . 14 4.8. Cryptographic Attributes . . . . . . . . . . . . . . . . 14
4.9. Cryptographic Attributes . . . . . . . . . . . . . . . . 15 4.8.1. Digital Signing . . . . . . . . . . . . . . . . . . . 15
4.9.1. Digital Signing . . . . . . . . . . . . . . . . . . . 15 4.8.2. Authenticated Encryption with Additional Data (AEAD) 16
4.9.2. Authenticated Encryption with Additional Data (AEAD) 16 5. The TLS Record Protocol . . . . . . . . . . . . . . . . . . . 17
5. The TLS Record Protocol . . . . . . . . . . . . . . . . . . . 16
5.1. Connection States . . . . . . . . . . . . . . . . . . . . 17 5.1. Connection States . . . . . . . . . . . . . . . . . . . . 17
5.2. Record Layer . . . . . . . . . . . . . . . . . . . . . . 19 5.2. Record Layer . . . . . . . . . . . . . . . . . . . . . . 19
5.2.1. Fragmentation . . . . . . . . . . . . . . . . . . . . 19 5.2.1. Fragmentation . . . . . . . . . . . . . . . . . . . . 19
5.2.2. Record Payload Protection . . . . . . . . . . . . . . 21 5.2.2. Record Payload Protection . . . . . . . . . . . . . . 21
5.2.3. Record Padding . . . . . . . . . . . . . . . . . . . 23 5.2.3. Record Padding . . . . . . . . . . . . . . . . . . . 23
6. The TLS Handshaking Protocols . . . . . . . . . . . . . . . . 24 6. The TLS Handshaking Protocols . . . . . . . . . . . . . . . . 24
6.1. Alert Protocol . . . . . . . . . . . . . . . . . . . . . 25 6.1. Alert Protocol . . . . . . . . . . . . . . . . . . . . . 25
6.1.1. Closure Alerts . . . . . . . . . . . . . . . . . . . 26 6.1.1. Closure Alerts . . . . . . . . . . . . . . . . . . . 26
6.1.2. Error Alerts . . . . . . . . . . . . . . . . . . . . 27 6.1.2. Error Alerts . . . . . . . . . . . . . . . . . . . . 28
6.2. Handshake Protocol Overview . . . . . . . . . . . . . . . 31 6.2. Handshake Protocol Overview . . . . . . . . . . . . . . . 31
6.2.1. Incorrect DHE Share . . . . . . . . . . . . . . . . . 34 6.2.1. Incorrect DHE Share . . . . . . . . . . . . . . . . . 35
6.2.2. Zero-RTT Exchange . . . . . . . . . . . . . . . . . . 35 6.2.2. Zero-RTT Exchange . . . . . . . . . . . . . . . . . . 36
6.2.3. Resumption and PSK . . . . . . . . . . . . . . . . . 37 6.2.3. Resumption and PSK . . . . . . . . . . . . . . . . . 37
6.3. Handshake Protocol . . . . . . . . . . . . . . . . . . . 38
6.3.1. Hello Messages . . . . . . . . . . . . . . . . . . . 39 6.3. Handshake Protocol . . . . . . . . . . . . . . . . . . . 39
6.3.2. Hello Extensions . . . . . . . . . . . . . . . . . . 44 6.3.1. Key Exchange Messages . . . . . . . . . . . . . . . . 40
6.3.3. Encrypted Extensions . . . . . . . . . . . . . . . . 57 6.3.2. Hello Extensions . . . . . . . . . . . . . . . . . . 46
6.3.4. Server Certificate . . . . . . . . . . . . . . . . . 57 6.3.3. Server Parameters . . . . . . . . . . . . . . . . . . 58
6.3.5. Certificate Request . . . . . . . . . . . . . . . . . 60 6.3.4. Authentication Messages . . . . . . . . . . . . . . . 63
6.3.6. Server Configuration . . . . . . . . . . . . . . . . 62 6.3.5. Post-Handshake Messages . . . . . . . . . . . . . . . 71
6.3.7. Server Certificate Verify . . . . . . . . . . . . . . 63 7. Cryptographic Computations . . . . . . . . . . . . . . . . . 73
6.3.8. Server Finished . . . . . . . . . . . . . . . . . . . 64 7.1. Key Schedule . . . . . . . . . . . . . . . . . . . . . . 73
6.3.9. Client Certificate . . . . . . . . . . . . . . . . . 65 7.2. Updating Traffic Keys and IVs . . . . . . . . . . . . . . 75
6.3.10. Client Certificate Verify . . . . . . . . . . . . . . 66 7.3. Traffic Key Calculation . . . . . . . . . . . . . . . . . 76
6.3.11. New Session Ticket Message . . . . . . . . . . . . . 67 7.3.1. The Handshake Hash . . . . . . . . . . . . . . . . . 77
7. Cryptographic Computations . . . . . . . . . . . . . . . . . 68 7.3.2. Diffie-Hellman . . . . . . . . . . . . . . . . . . . 77
7.1. Key Schedule . . . . . . . . . . . . . . . . . . . . . . 68 7.3.3. Elliptic Curve Diffie-Hellman . . . . . . . . . . . . 77
7.2. Traffic Key Calculation . . . . . . . . . . . . . . . . . 70 8. Mandatory Algorithms . . . . . . . . . . . . . . . . . . . . 78
7.2.1. The Handshake Hash . . . . . . . . . . . . . . . . . 71 8.1. MTI Cipher Suites . . . . . . . . . . . . . . . . . . . . 78
7.2.2. Diffie-Hellman . . . . . . . . . . . . . . . . . . . 71 8.2. MTI Extensions . . . . . . . . . . . . . . . . . . . . . 78
7.2.3. Elliptic Curve Diffie-Hellman . . . . . . . . . . . . 72 9. Application Data Protocol . . . . . . . . . . . . . . . . . . 79
8. Mandatory Algorithms . . . . . . . . . . . . . . . . . . . . 72 10. Security Considerations . . . . . . . . . . . . . . . . . . . 80
8.1. MTI Cipher Suites . . . . . . . . . . . . . . . . . . . . 72 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 80
8.2. MTI Extensions . . . . . . . . . . . . . . . . . . . . . 72 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 83
9. Application Data Protocol . . . . . . . . . . . . . . . . . . 73 12.1. Normative References . . . . . . . . . . . . . . . . . . 83
10. Security Considerations . . . . . . . . . . . . . . . . . . . 74 12.2. Informative References . . . . . . . . . . . . . . . . . 85
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 74 Appendix A. Protocol Data Structures and Constant Values . . . . 91
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 75 A.1. Record Layer . . . . . . . . . . . . . . . . . . . . . . 91
12.1. Normative References . . . . . . . . . . . . . . . . . . 75 A.2. Alert Messages . . . . . . . . . . . . . . . . . . . . . 91
12.2. Informative References . . . . . . . . . . . . . . . . . 77 A.3. Handshake Protocol . . . . . . . . . . . . . . . . . . . 93
Appendix A. Protocol Data Structures and Constant Values . . . . 81 A.3.1. Key Exchange Messages . . . . . . . . . . . . . . . . 93
A.1. Record Layer . . . . . . . . . . . . . . . . . . . . . . 81 A.3.2. Server Parameters Messages . . . . . . . . . . . . . 98
A.2. Alert Messages . . . . . . . . . . . . . . . . . . . . . 81 A.3.3. Authentication Messages . . . . . . . . . . . . . . . 98
A.3. Handshake Protocol . . . . . . . . . . . . . . . . . . . 82 A.3.4. Ticket Establishment . . . . . . . . . . . . . . . . 99
A.3.1. Hello Messages . . . . . . . . . . . . . . . . . . . 83 A.4. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 99
A.3.2. Key Exchange Messages . . . . . . . . . . . . . . . . 87 A.4.1. Unauthenticated Operation . . . . . . . . . . . . . . 102
A.3.3. Authentication Messages . . . . . . . . . . . . . . . 87 A.5. The Security Parameters . . . . . . . . . . . . . . . . . 102
A.3.4. Handshake Finalization Messages . . . . . . . . . . . 88 A.6. Changes to RFC 4492 . . . . . . . . . . . . . . . . . . . 103
A.3.5. Ticket Establishment . . . . . . . . . . . . . . . . 88 Appendix B. Implementation Notes . . . . . . . . . . . . . . . . 104
A.4. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 88 B.1. Random Number Generation and Seeding . . . . . . . . . . 104
A.4.1. Unauthenticated Operation . . . . . . . . . . . . . . 90 B.2. Certificates and Authentication . . . . . . . . . . . . . 104
A.5. The Security Parameters . . . . . . . . . . . . . . . . . 91 B.3. Cipher Suite Support . . . . . . . . . . . . . . . . . . 104
A.6. Changes to RFC 4492 . . . . . . . . . . . . . . . . . . . 91 B.4. Implementation Pitfalls . . . . . . . . . . . . . . . . . 104
Appendix B. Implementation Notes . . . . . . . . . . . . . . . . 92 Appendix C. Backward Compatibility . . . . . . . . . . . . . . . 106
B.1. Random Number Generation and Seeding . . . . . . . . . . 92 C.1. Negotiating with an older server . . . . . . . . . . . . 106
B.2. Certificates and Authentication . . . . . . . . . . . . . 92 C.2. Negotiating with an older client . . . . . . . . . . . . 107
B.3. Cipher Suite Support . . . . . . . . . . . . . . . . . . 93 C.3. Backwards Compatibility Security Restrictions . . . . . . 107
B.4. Implementation Pitfalls . . . . . . . . . . . . . . . . . 93 Appendix D. Security Analysis . . . . . . . . . . . . . . . . . 108
Appendix C. Backward Compatibility . . . . . . . . . . . . . . . 94 D.1. Handshake Protocol . . . . . . . . . . . . . . . . . . . 108
C.1. Negotiating with an older server . . . . . . . . . . . . 95 D.1.1. Authentication and Key Exchange . . . . . . . . . . . 109
C.2. Negotiating with an older client . . . . . . . . . . . . 95 D.1.2. Version Rollback Attacks . . . . . . . . . . . . . . 109
C.3. Backwards Compatibility Security Restrictions . . . . . . 96 D.1.3. Detecting Attacks Against the Handshake Protocol . . 110
Appendix D. Security Analysis . . . . . . . . . . . . . . . . . 96
D.1. Handshake Protocol . . . . . . . . . . . . . . . . . . . 97 D.2. Protecting Application Data . . . . . . . . . . . . . . . 110
D.1.1. Authentication and Key Exchange . . . . . . . . . . . 97 D.3. Denial of Service . . . . . . . . . . . . . . . . . . . . 110
D.1.2. Version Rollback Attacks . . . . . . . . . . . . . . 98 D.4. Final Notes . . . . . . . . . . . . . . . . . . . . . . . 111
D.1.3. Detecting Attacks Against the Handshake Protocol . . 98 Appendix E. Working Group Information . . . . . . . . . . . . . 111
D.2. Protecting Application Data . . . . . . . . . . . . . . . 98 Appendix F. Contributors . . . . . . . . . . . . . . . . . . . . 111
D.3. Denial of Service . . . . . . . . . . . . . . . . . . . . 99 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 115
D.4. Final Notes . . . . . . . . . . . . . . . . . . . . . . . 99
Appendix E. Working Group Information . . . . . . . . . . . . . 99
Appendix F. Contributors . . . . . . . . . . . . . . . . . . . . 100
1. Introduction 1. Introduction
DISCLAIMER: This is a WIP draft of TLS 1.3 and has not yet seen DISCLAIMER: This is a WIP draft of TLS 1.3 and has not yet seen
significant security analysis. significant security analysis.
RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH The source for this RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH The source for this
draft is maintained in GitHub. Suggested changes should be submitted draft is maintained in GitHub. Suggested changes should be submitted
as pull requests at https://github.com/tlswg/tls13-spec. as pull requests at https://github.com/tlswg/tls13-spec.
Instructions are on that page as well. Editorial changes can be Instructions are on that page as well. Editorial changes can be
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sender: An endpoint that is transmitting records. sender: An endpoint that is transmitting records.
session: An association between a client and a server resulting from session: An association between a client and a server resulting from
a handshake. a handshake.
server: The endpoint which did not initiate the TLS connection. server: The endpoint which did not initiate the TLS connection.
1.2. Major Differences from TLS 1.2 1.2. Major Differences from TLS 1.2
draft-11
- Port the CFRG curves & signatures work from RFC4492bis.
- Remove sequence number and version from additional_data, which is
now empty.
- Reorder values in HkdfLabel.
- Add support for version anti-downgrade mechanism.
- Update IANA considerations section and relax some of the policies.
- Unify authentication modes. Add post-handshake client
authentication.
- Remove early_handshake content type. Terminate 0-RTT data with an
alert.
- Reset sequence number upon key change (as proposed by Fournet et
al.)
draft-10 draft-10
- Remove ClientCertificateTypes field from CertificateRequest and - Remove ClientCertificateTypes field from CertificateRequest and
add extensions. add extensions.
- Merge client and server key shares into a single extension. - Merge client and server key shares into a single extension.
draft-09 draft-09
- Change to RSA-PSS signatures for handshake messages. - Change to RSA-PSS signatures for handshake messages.
skipping to change at page 14, line 45 skipping to change at page 14, line 47
For example: For example:
struct { struct {
uint8 f1; uint8 f1;
uint8 f2; uint8 f2;
} Example1; } Example1;
Example1 ex1 = {1, 4}; /* assigns f1 = 1, f2 = 4 */ Example1 ex1 = {1, 4}; /* assigns f1 = 1, f2 = 4 */
4.8. Primitive Types 4.8. Cryptographic Attributes
The following common primitive types are defined and used
subsequently:
enum { false(0), true(1) } Boolean;
4.9. Cryptographic Attributes
The two cryptographic operations -- digital signing, and The two cryptographic operations -- digital signing, and
authenticated encryption with additional data (AEAD) -- are authenticated encryption with additional data (AEAD) -- are
designated digitally-signed, and aead-ciphered, respectively. A designated digitally-signed, and aead-ciphered, respectively. A
field's cryptographic processing is specified by prepending an field's cryptographic processing is specified by prepending an
appropriate key word designation before the field's type appropriate key word designation before the field's type
specification. Cryptographic keys are implied by the current session specification. Cryptographic keys are implied by the current session
state (see Section 5.1). state (see Section 5.1).
4.9.1. Digital Signing 4.8.1. Digital Signing
A digitally-signed element is encoded as a struct DigitallySigned: A digitally-signed element is encoded as a struct DigitallySigned:
struct { struct {
SignatureAndHashAlgorithm algorithm; SignatureAndHashAlgorithm algorithm;
opaque signature<0..2^16-1>; opaque signature<0..2^16-1>;
} DigitallySigned; } DigitallySigned;
The algorithm field specifies the algorithm used (see Section 6.3.2.1 The algorithm field specifies the algorithm used (see Section 6.3.2.1
for the definition of this field). Note that the algorithm field was for the definition of this field). Note that the algorithm field was
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the element. The contents themselves do not appear on the wire but the element. The contents themselves do not appear on the wire but
are simply calculated. The length of the signature is specified by are simply calculated. The length of the signature is specified by
the signing algorithm and key. the signing algorithm and key.
In previous versions of TLS, the ServerKeyExchange format meant that In previous versions of TLS, the ServerKeyExchange format meant that
attackers can obtain a signature of a message with a chosen, 32-byte attackers can obtain a signature of a message with a chosen, 32-byte
prefix. Because TLS 1.3 servers are likely to also implement prior prefix. Because TLS 1.3 servers are likely to also implement prior
versions, the contents of the element always start with 64 bytes of versions, the contents of the element always start with 64 bytes of
octet 32 in order to clear that chosen-prefix. octet 32 in order to clear that chosen-prefix.
Following that padding is a NUL-terminated context string in order to Following that padding is a context string used to disambiguate
disambiguate signatures for different purposes. The context string signatures for different purposes. The context string will be
will be specified whenever a digitally-signed element is used. specified whenever a digitally-signed element is used. A single 0
byte is appended to the context to act as a separator.
Finally, the specified contents of the digitally-signed structure Finally, the specified contents of the digitally-signed structure
follow the NUL at the end of the context string. (See the example at follow the NUL after the context string. (See the example at the end
the end of this section.) of this section.)
In RSA signing, the opaque vector contains the signature generated In RSA signing, the opaque vector contains the signature generated
using the RSASSA-PSS signature scheme defined in [RFC3447] with MGF1. using the RSASSA-PSS signature scheme defined in [RFC3447] with MGF1.
The digest used in the mask generation function MUST be the same as The digest used in the mask generation function MUST be the same as
the digest which is being signed (i.e., what appears in the digest which is being signed (i.e., what appears in
algorithm.signature). The length of the salt MUST be equal to the algorithm.signature). The length of the salt MUST be equal to the
octet length of the digest output. Note that previous versions of length of the digest output. Note that previous versions of TLS used
TLS used RSASSA-PKCS1-v1_5, not RSASSA-PSS. RSASSA-PKCS1-v1_5, not RSASSA-PSS.
All ECDSA computations MUST be performed according to ANSI X9.62 All ECDSA computations MUST be performed according to ANSI X9.62
[X962] or its successors. Data to be signed/verified is hashed, and [X962] or its successors. Data to be signed/verified is hashed, and
the result run directly through the ECDSA algorithm with no the result run directly through the ECDSA algorithm with no
additional hashing. The SignatureAndHashAlgorithm parameter in the additional hashing. The SignatureAndHashAlgorithm parameter in the
DigitallySigned object indicates the digest algorithm which was used DigitallySigned object indicates the digest algorithm which was used
in the signature. in the signature. Signature-only curves MUST NOT be used for ECDSA
unless otherwise noted.
All EdDSA computations MUST be performed according to
[I-D.irtf-cfrg-eddsa] or its successors. Data to be signed/verified
is passed as-is to the EdDSA algorithm with no hashing. The
signature output is placed as-is in the signature field. The
SignatureAndHashAlgorithm.hash value MUST set to none(0).
In the following example In the following example
struct { struct {
uint8 field1; uint8 field1;
uint8 field2; uint8 field2;
digitally-signed opaque { digitally-signed opaque {
uint8 field3<0..255>; uint8 field3<0..255>;
uint8 field4; uint8 field4;
}; };
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followed by the encoding of the inner struct (field3 and field4). followed by the encoding of the inner struct (field3 and field4).
The length of the structure, in bytes, would be equal to two bytes The length of the structure, in bytes, would be equal to two bytes
for field1 and field2, plus two bytes for the signature and hash for field1 and field2, plus two bytes for the signature and hash
algorithm, plus two bytes for the length of the signature, plus the algorithm, plus two bytes for the length of the signature, plus the
length of the output of the signing algorithm. The length of the length of the output of the signing algorithm. The length of the
signature is known because the algorithm and key used for the signing signature is known because the algorithm and key used for the signing
are known prior to encoding or decoding this structure. are known prior to encoding or decoding this structure.
4.9.2. Authenticated Encryption with Additional Data (AEAD) 4.8.2. Authenticated Encryption with Additional Data (AEAD)
In AEAD encryption, the plaintext is simultaneously encrypted and In AEAD encryption, the plaintext is simultaneously encrypted and
integrity protected. The input may be of any length, and aead- integrity protected. The input may be of any length, and aead-
ciphered output is generally larger than the input in order to ciphered output is generally larger than the input in order to
accommodate the integrity check value. accommodate the integrity check value.
5. The TLS Record Protocol 5. The TLS Record Protocol
The TLS Record Protocol is a layered protocol. At each layer, The TLS Record Protocol is a layered protocol. At each layer,
messages may include fields for length, description, and content. messages may include fields for length, description, and content.
skipping to change at page 18, line 5 skipping to change at page 18, line 11
The security parameters for a TLS Connection read and write state are The security parameters for a TLS Connection read and write state are
set by providing the following values: set by providing the following values:
connection end connection end
Whether this entity is considered the "client" or the "server" in Whether this entity is considered the "client" or the "server" in
this connection. this connection.
Hash algorithm Hash algorithm
An algorithm used to generate keys from the appropriate secret An algorithm used to generate keys from the appropriate secret
(see Section 7.1 and Section 7.2). (see Section 7.1 and Section 7.3).
record protection algorithm record protection algorithm
The algorithm to be used for record protection. This algorithm The algorithm to be used for record protection. This algorithm
must be of the AEAD type and thus provides integrity and must be of the AEAD type and thus provides integrity and
confidentiality as a single primitive. This specification confidentiality as a single primitive. This specification
includes the key size of this algorithm and of the nonce for the includes the key size of this algorithm and of the nonce for the
AEAD algorithm. AEAD algorithm.
master secret master secret
A 48-byte secret shared between the two peers in the connection A 48-byte secret shared between the two peers in the connection
skipping to change at page 19, line 12 skipping to change at page 19, line 17
The connection state will use the security parameters to generate the The connection state will use the security parameters to generate the
following four items: following four items:
client write key client write key
server write key server write key
client write iv client write iv
server write iv server write iv
The client write parameters are used by the server when receiving and The client write parameters are used by the server when receiving and
processing records and vice versa. The algorithm used for generating processing records and vice versa. The algorithm used for generating
these items from the security parameters is described in Section 7.2. these items from the security parameters is described in Section 7.3.
Once the security parameters have been set and the keys have been Once the security parameters have been set and the keys have been
generated, the connection states can be instantiated by making them generated, the connection states can be instantiated by making them
the current states. These current states MUST be updated for each the current states. These current states MUST be updated for each
record processed. Each connection state includes the following record processed. Each connection state includes the following
elements: elements:
cipher state cipher state
The current state of the encryption algorithm. This will consist The current state of the encryption algorithm. This will consist
of the scheduled key for that connection. of the scheduled key for that connection.
sequence number sequence number
Each connection state contains a sequence number, which is Each connection state contains a sequence number, which is
maintained separately for read and write states. The sequence maintained separately for read and write states. The sequence
number is set to zero at the beginning of a connection and number is set to zero at the beginning of a connection, and
incremented by one thereafter. Sequence numbers are of type whenever the key is changed. The sequence number is incremented
uint64 and MUST NOT exceed 2^64-1. Sequence numbers do not wrap.
If a TLS implementation would need to wrap a sequence number, it
MUST terminate the connection. A sequence number is incremented
after each record: specifically, the first record transmitted after each record: specifically, the first record transmitted
under a particular connection state MUST use sequence number 0. under a particular connection state and record key MUST use
NOTE: This is a change from previous versions of TLS, where sequence number 0. Sequence numbers are of type uint64 and MUST
sequence numbers were reset whenever keys were changed. NOT exceed 2^64-1. Sequence numbers do not wrap. If a TLS
implementation would need to wrap a sequence number, it MUST
either rekey (Section 6.3.5.3) or terminate the connection.
5.2. Record Layer 5.2. Record Layer
The TLS record layer receives uninterpreted data from higher layers The TLS record layer receives uninterpreted data from higher layers
in non-empty blocks of arbitrary size. in non-empty blocks of arbitrary size.
5.2.1. Fragmentation 5.2.1. Fragmentation
The record layer fragments information blocks into TLSPlaintext The record layer fragments information blocks into TLSPlaintext
records carrying data in chunks of 2^14 bytes or less. Client records carrying data in chunks of 2^14 bytes or less. Client
skipping to change at page 20, line 13 skipping to change at page 20, line 15
NOT be fragmented across records. NOT be fragmented across records.
struct { struct {
uint8 major; uint8 major;
uint8 minor; uint8 minor;
} ProtocolVersion; } ProtocolVersion;
enum { enum {
alert(21), alert(21),
handshake(22), handshake(22),
application_data(23), application_data(23)
early_handshake(25),
(255) (255)
} ContentType; } ContentType;
struct { struct {
ContentType type; ContentType type;
ProtocolVersion record_version = { 3, 1 }; /* TLS v1.x */ ProtocolVersion record_version = { 3, 1 }; /* TLS v1.x */
uint16 length; uint16 length;
opaque fragment[TLSPlaintext.length]; opaque fragment[TLSPlaintext.length];
} TLSPlaintext; } TLSPlaintext;
skipping to change at page 21, line 25 skipping to change at page 21, line 28
into a TLSCiphertext. The deprotection functions reverse the into a TLSCiphertext. The deprotection functions reverse the
process. In TLS 1.3 as opposed to previous versions of TLS, all process. In TLS 1.3 as opposed to previous versions of TLS, all
ciphers are modeled as "Authenticated Encryption with Additional ciphers are modeled as "Authenticated Encryption with Additional
Data" (AEAD) [RFC5116]. AEAD functions provide a unified encryption Data" (AEAD) [RFC5116]. AEAD functions provide a unified encryption
and authentication operation which turns plaintext into authenticated and authentication operation which turns plaintext into authenticated
ciphertext and back again. ciphertext and back again.
AEAD ciphers take as input a single key, a nonce, a plaintext, and AEAD ciphers take as input a single key, a nonce, a plaintext, and
"additional data" to be included in the authentication check, as "additional data" to be included in the authentication check, as
described in Section 2.1 of [RFC5116]. The key is either the described in Section 2.1 of [RFC5116]. The key is either the
client_write_key or the server_write_key. client_write_key or the server_write_key and in TLS 1.3 the
additional data input is empty (zero length).
struct { struct {
ContentType opaque_type = application_data(23); /* see fragment.type */ ContentType opaque_type = application_data(23); /* see fragment.type */
ProtocolVersion record_version = { 3, 1 }; /* TLS v1.x */ ProtocolVersion record_version = { 3, 1 }; /* TLS v1.x */
uint16 length; uint16 length;
aead-ciphered struct { aead-ciphered struct {
opaque content[TLSPlaintext.length]; opaque content[TLSPlaintext.length];
ContentType type; ContentType type;
uint8 zeros[length_of_padding]; uint8 zeros[length_of_padding];
} fragment; } fragment;
skipping to change at page 22, line 48 skipping to change at page 22, line 50
The resulting quantity (of length iv_length) is used as the per- The resulting quantity (of length iv_length) is used as the per-
record nonce. record nonce.
Note: This is a different construction from that in TLS 1.2, which Note: This is a different construction from that in TLS 1.2, which
specified a partially explicit nonce. specified a partially explicit nonce.
The plaintext is the concatenation of TLSPlaintext.fragment and The plaintext is the concatenation of TLSPlaintext.fragment and
TLSPlaintext.type. TLSPlaintext.type.
The additional authenticated data, which we denote as
additional_data, is defined as follows:
additional_data = seq_num + TLSPlaintext.record_version
where "+" denotes concatenation.
Note: In versions of TLS prior to 1.3, the additional_data included a
length field. This presents a problem for cipher constructions with
data-dependent padding (such as CBC). TLS 1.3 removes the length
field and relies on the AEAD cipher to provide integrity for the
length of the data.
The AEAD output consists of the ciphertext output by the AEAD The AEAD output consists of the ciphertext output by the AEAD
encryption operation. The length of the plaintext is greater than encryption operation. The length of the plaintext is greater than
TLSPlaintext.length due to the inclusion of TLSPlaintext.type and TLSPlaintext.length due to the inclusion of TLSPlaintext.type and
however much padding is supplied by the sender. The length of however much padding is supplied by the sender. The length of
aead_output will generally be larger than the plaintext, but by an aead_output will generally be larger than the plaintext, but by an
amount that varies with the AEAD cipher. Since the ciphers might amount that varies with the AEAD cipher. Since the ciphers might
incorporate padding, the amount of overhead could vary with different incorporate padding, the amount of overhead could vary with different
lengths of plaintext. Symbolically, lengths of plaintext. Symbolically,
AEADEncrypted = AEAD-Encrypt(write_key, nonce, plaintext of fragment, AEADEncrypted =
additional_data) AEAD-Encrypt(write_key, nonce, plaintext of fragment)
In order to decrypt and verify, the cipher takes as input the key, In order to decrypt and verify, the cipher takes as input the key,
nonce, the "additional_data", and the AEADEncrypted value. The nonce, and the AEADEncrypted value. The output is either the
output is either the plaintext or an error indicating that the plaintext or an error indicating that the decryption failed. There
decryption failed. There is no separate integrity check. That is: is no separate integrity check. That is:
plaintext of fragment = AEAD-Decrypt(write_key, nonce, plaintext of fragment =
AEADEncrypted, AEAD-Decrypt(write_key, nonce, AEADEncrypted)
additional_data)
If the decryption fails, a fatal "bad_record_mac" alert MUST be If the decryption fails, a fatal "bad_record_mac" alert MUST be
generated. generated.
An AEAD cipher MUST NOT produce an expansion of greater than 255 An AEAD cipher MUST NOT produce an expansion of greater than 255
bytes. An endpoint that receives a record from its peer with bytes. An endpoint that receives a record from its peer with
TLSCipherText.length larger than 2^14 + 256 octets MUST generate a TLSCipherText.length larger than 2^14 + 256 octets MUST generate a
fatal "record_overflow" alert. This limit is derived from the fatal "record_overflow" alert. This limit is derived from the
maximum TLSPlaintext length of 2^14 octets + 1 octet for ContentType maximum TLSPlaintext length of 2^14 octets + 1 octet for ContentType
+ the maximum AEAD expansion of 255 octets. + the maximum AEAD expansion of 255 octets.
skipping to change at page 26, line 9 skipping to change at page 26, line 9
connection. In this case, other connections corresponding to the connection. In this case, other connections corresponding to the
session may continue, but the session identifier MUST be invalidated, session may continue, but the session identifier MUST be invalidated,
preventing the failed session from being used to establish new preventing the failed session from being used to establish new
connections. Like other messages, alert messages are encrypted as connections. Like other messages, alert messages are encrypted as
specified by the current connection state. specified by the current connection state.
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
end_of_early_data(1),
unexpected_message(10), /* fatal */ unexpected_message(10), /* fatal */
bad_record_mac(20), /* fatal */ bad_record_mac(20), /* fatal */
record_overflow(22), /* fatal */ record_overflow(22), /* fatal */
handshake_failure(40), /* fatal */ handshake_failure(40), /* fatal */
bad_certificate(42), bad_certificate(42),
unsupported_certificate(43), unsupported_certificate(43),
certificate_revoked(44), certificate_revoked(44),
certificate_expired(45), certificate_expired(45),
certificate_unknown(46), certificate_unknown(46),
illegal_parameter(47), /* fatal */ illegal_parameter(47), /* fatal */
skipping to change at page 26, line 50 skipping to change at page 27, line 4
AlertDescription description; AlertDescription description;
} Alert; } Alert;
6.1.1. Closure Alerts 6.1.1. Closure Alerts
The client and the server must share knowledge that the connection is The client and the server must share knowledge that the connection is
ending in order to avoid a truncation attack. Failure to properly ending in order to avoid a truncation attack. Failure to properly
close a connection does not prohibit a session from being resumed. close a connection does not prohibit a session from being resumed.
close_notify close_notify
This message notifies the recipient that the sender will not send This alert notifies the recipient that the sender will not send
any more messages on this connection. Any data received after a any more messages on this connection. Any data received after a
closure MUST be ignored. closure MUST be ignored.
end_of_early_data
This alert is sent by the client to indicate that all 0-RTT
application_data messages have been transmitted (or none will be
sent at all) and that this is the end of the flight. This alert
MUST be at the warning level. Servers MUST NOT send this alert
and clients receiving it MUST terminate the connection with an
"unexpected_message" alert.
user_canceled user_canceled
This message notifies the recipient that the sender is canceling This alert notifies the recipient that the sender is canceling the
the handshake for some reason unrelated to a protocol failure. If handshake for some reason unrelated to a protocol failure. If a
a user cancels an operation after the handshake is complete, just user cancels an operation after the handshake is complete, just
closing the connection by sending a "close_notify" is more closing the connection by sending a "close_notify" is more
appropriate. This alert SHOULD be followed by a "close_notify". appropriate. This alert SHOULD be followed by a "close_notify".
This alert is generally a warning. This alert is generally a warning.
Either party MAY initiate a close by sending a "close_notify" alert. Either party MAY initiate a close by sending a "close_notify" alert.
Any data received after a closure alert is ignored. If a transport- Any data received after a closure alert is ignored. If a transport-
level close is received prior to a "close_notify", the receiver level close is received prior to a "close_notify", the receiver
cannot know that all the data that was sent has been received. cannot know that all the data that was sent has been received.
Each party MUST send a "close_notify" alert before closing the write Each party MUST send a "close_notify" alert before closing the write
skipping to change at page 31, line 35 skipping to change at page 31, line 47
TLS supports three basic key exchange modes: TLS supports three basic key exchange modes:
- Diffie-Hellman (of both the finite field and elliptic curve - Diffie-Hellman (of both the finite field and elliptic curve
varieties). varieties).
- A pre-shared symmetric key (PSK) - A pre-shared symmetric key (PSK)
- A combination of a symmetric key and Diffie-Hellman - A combination of a symmetric key and Diffie-Hellman
Which mode is used depends on the negotiated cipher suite. Which mode is used depends on the negotiated cipher suite.
Conceptually, the handshake establishes two secrets which are used to Conceptually, the handshake establishes three secrets which are used
derive all the keys. to derive all the keys.
Ephemeral Secret (ES): A secret which is derived from fresh (EC)DHE Ephemeral Secret (ES): A secret which is derived from fresh (EC)DHE
shares for this connection. Keying material derived from ES is shares for this connection. Keying material derived from ES is
intended to be forward secure (with the exception of pre-shared key intended to be forward secret (with the exception of pre-shared key
only modes). only modes).
Static Secret (SS): A secret which may be derived from static or Static Secret (SS): A secret which may be derived from static or
semi-static keying material, such as a pre-shared key or the server's semi-static keying material, such as a pre-shared key or the server's
semi-static (EC)DH share. semi-static (EC)DH share.
In some cases, as with the DH handshake shown in Figure 1, these Master Secret (MS): A secret derived from both the static and the
secrets are the same, but having both allows for a uniform key ephemeral secret.
derivation scheme for all cipher modes.
In some cases, as with the DH handshake shown in Figure 1, the
ephemeral and shared secrets are the same, but having both allows for
a uniform key derivation scheme for all cipher modes.
The basic TLS Handshake for DH is shown in Figure 1: The basic TLS Handshake for DH is shown in Figure 1:
Client Server Client Server
ClientHello Key / ClientHello
+ KeyShare --------> Exch \ + key_share -------->
ServerHello ServerHello \ Key
+ KeyShare + key_share / Exch
{EncryptedExtensions} {EncryptedExtensions} ^
{ServerConfiguration*} {CertificateRequest*} | Server
{Certificate*} {ServerConfiguration*} v Params
{CertificateRequest*} {Certificate*} ^
{CertificateVerify*} {CertificateVerify*} | Auth
<-------- {Finished} <-------- {Finished} v
{Certificate*} ^ {Certificate*}
{CertificateVerify*} Auth | {CertificateVerify*}
{Finished} --------> v {Finished} -------->
[Application Data] <-------> [Application Data] [Application Data] <-------> [Application Data]
+ Indicates extensions sent in the + Indicates extensions sent in the
previously noted message. previously noted message.
* Indicates optional or situation-dependent * Indicates optional or situation-dependent
messages that are not always sent. messages that are not always sent.
{} Indicates messages protected using keys {} Indicates messages protected using keys
derived from the ephemeral secret. derived from the ephemeral secret.
[] Indicates messages protected using keys [] Indicates messages protected using keys
derived from the master secret. derived from the master secret.
Figure 1: Message flow for full TLS Handshake Figure 1: Message flow for full TLS Handshake
The first message sent by the client is the ClientHello The handshake can be thought of as having three phases, indicated in
Section 6.3.1.1 which contains a random nonce (ClientHello.random), the diagram above.
its offered protocol version, cipher suite, and extensions, and one
or more Diffie-Hellman key shares in the KeyShare extension Key Exchange: establish shared keying material and select the
Section 6.3.2.3. cryptographic parameters. Everything after this phase is encrypted.
Server Parameters: establish other handshake parameters (whether the
client is authenticated, support for 0-RTT, etc.)
Authentication: authenticate the server (and optionally the client)
and provide key confirmation and handshake integrity.
In the Key Exchange phase, the client sends the ClientHello
(Section 6.3.1.1) message, which contains a random nonce
(ClientHello.random), its offered protocol version, cipher suite, and
extensions, and one or more Diffie-Hellman key shares in the
"key_share" extension Section 6.3.2.3.
The server processes the ClientHello and determines the appropriate The server processes the ClientHello and determines the appropriate
cryptographic parameters for the connection. It then responds with cryptographic parameters for the connection. It then responds with
the following messages: its own ServerHello which indicates the negotiated connection
parameters. [Section 6.3.1.2] If DH is in use, this will contain a
ServerHello "key_share" extension with the server's ephemeral Diffie-Hellman
indicates the negotiated connection parameters. [Section 6.3.1.2] share which MUST be in the same group as one of the shares offered by
If DH is in use, this will contain a KeyShare extension with the the client. The server's KeyShare and the client's KeyShare
server's ephemeral Diffie-Hellman share which MUST be in the same corresponding to the negotiated key exchange are used together to
group as one of the shares offered by the client. The server's derive the Static Secret and Ephemeral Secret (in this mode they are
KeyShare and the client's KeyShare corresponding to the negotiated the same). [Section 6.3.2.3]
key exchange are used together to derive the Static Secret and
Ephemeral Secret (in this mode they are the same).
[Section 6.3.2.3]
ServerConfiguration The server then sends three messages to establish the Server
supplies a configuration for 0-RTT handshakes (see Section 6.2.2). Parameters:
[Section 6.3.6]
EncryptedExtensions EncryptedExtensions
responses to any extensions which are not required in order to responses to any extensions which are not required in order to
determine the cryptographic parameters. [Section 6.3.3] determine the cryptographic parameters. [Section 6.3.3.1]
Certificate
the server certificate. This message will be omitted if the
server is not authenticating via a certificates. [Section 6.3.4]
CertificateRequest CertificateRequest
if certificate-based client authentication is desired, the desired if certificate-based client authentication is desired, the desired
parameters for that certificate. This message will be omitted if parameters for that certificate. This message will be omitted if
client authentication is not desired. [[OPEN ISSUE: See client authentication is not desired. [[OPEN ISSUE: See
https://github.com/tlswg/tls13-spec/issues/184]]. [Section 6.3.5] https://github.com/tlswg/tls13-spec/issues/184]].
[Section 6.3.3.2]
CertificateVerify
a signature over the entire handshake using the public key in the
Certificate message. This message will be omitted if the server
is not authenticating via a certificate. [Section 6.3.7]
Finished ServerConfiguration
a MAC over the entire handshake computed using the Static Secret. supplies a configuration for 0-RTT handshakes (see Section 6.2.2).
This message provides key confirmation and In some modes (see [Section 6.3.3.3]
Section 6.2.2) it also authenticates the handshake using the the
Static Secret. [Section 6.3.8]
Upon receiving the server's messages, the client responds with his Finally, the client and server exchange Authentication messages. TLS
final flight of messages: uses the same set of messages every time that authentication is
needed. Specifically:
Certificate Certificate
the client's certificate. This message will be omitted if the the certificate of the endpoint. This message is omitted if
client is not authenticating via a certificates. [Section 6.3.9] certificate authentication is not being used. [Section 6.3.4.1]
CertificateVerify CertificateVerify
a signature over the entire handshake using the private key a signature over the entire handshake using the public key in the
corresponding to the public key in the Certificate message. This Certificate message. This message will be omitted if the server
message will be omitted if the client is not authenticating via a is not authenticating via a certificate. [Section 6.3.4.2]
certificate. [Section 6.3.10]
Finished Finished
a MAC over the entire handshake computed using the Static Secret a MAC over the entire handshake. This message provides key
and providing key confirmation. [Section 6.3.8] confirmation, binds the endpoint's identity to the exchanged keys,
and in some modes (0-RTT and PSK) also authenticates the handshake
using the the Static Secret. [Section 6.3.4.3]
Upon receiving the server's messages, the client responds with its
Authentication messages, namely Certificate and CertificateVerify (if
requested), and Finished.
At this point, the handshake is complete, and the client and server At this point, the handshake is complete, and the client and server
may exchange application layer data. Application data MUST NOT be may exchange application layer data. Application data MUST NOT be
sent prior to sending the Finished message. If client authentication sent prior to sending the Finished message. Note that while the
is requested, the server MUST NOT send application data before it server may send application data prior to receiving the client's
receives the client's Finished. Authentication messages, any data sent at that point is of course
being sent to an unauthenticated peer.
[[TODO: Move this elsewhere? Note that higher layers should not be [[TODO: Move this elsewhere? Note that higher layers should not be
overly reliant on whether TLS always negotiates the strongest overly reliant on whether TLS always negotiates the strongest
possible connection between two endpoints. There are a number of possible connection between two endpoints. There are a number of
ways in which a man-in-the-middle attacker can attempt to make two ways in which a man-in-the-middle attacker can attempt to make two
entities drop down to the least secure method they support (i.e., entities drop down to the least secure method they support (i.e.,
perform a downgrade attack). The TLS protocol has been designed to perform a downgrade attack). The TLS protocol has been designed to
minimize this risk, but there are still attacks available: for minimize this risk, but there are still attacks available: for
example, an attacker could block access to the port a secure service example, an attacker could block access to the port a secure service
runs on, or attempt to get the peers to negotiate an unauthenticated runs on, or attempt to get the peers to negotiate an unauthenticated
skipping to change at page 34, line 31 skipping to change at page 35, line 7
cognizant of what their security requirements are and never transmit cognizant of what their security requirements are and never transmit
information over a channel less secure than what they require. The information over a channel less secure than what they require. The
TLS protocol is secure in that any cipher suite offers its promised TLS protocol is secure in that any cipher suite offers its promised
level of security: if you negotiate AES-GCM [GCM] with a 255-bit level of security: if you negotiate AES-GCM [GCM] with a 255-bit
ECDHE key exchange with a host whose certificate chain you have ECDHE key exchange with a host whose certificate chain you have
verified, you can expect that to be reasonably "secure" against verified, you can expect that to be reasonably "secure" against
algorithmic attacks, at least in the year 2015.]] algorithmic attacks, at least in the year 2015.]]
6.2.1. Incorrect DHE Share 6.2.1. Incorrect DHE Share
If the client has not provided an appropriate KeyShare extension If the client has not provided an appropriate "key_share" extension
(e.g. it includes only DHE or ECDHE groups unacceptable or (e.g. it includes only DHE or ECDHE groups unacceptable or
unsupported by the server), the server corrects the mismatch with a unsupported by the server), the server corrects the mismatch with a
HelloRetryRequest and the client will need to restart the handshake HelloRetryRequest and the client will need to restart the handshake
with an appropriate KeyShare extension, as shown in Figure 2: with an appropriate "key_share" extension, as shown in Figure 2:
Client Server Client Server
ClientHello ClientHello
+ KeyShare --------> + key_share -------->
<-------- HelloRetryRequest <-------- HelloRetryRequest
ClientHello ClientHello
+ KeyShare --------> + key_share -------->
ServerHello ServerHello
+ KeyShare + key_share
{EncryptedExtensions} {EncryptedExtensions}
{ServerConfiguration*} {CertificateRequest*}
{Certificate*} {ServerConfiguration*}
{CertificateRequest*} {Certificate*}
{CertificateVerify*} {CertificateVerify*}
<-------- {Finished} <-------- {Finished}
{Certificate*} {Certificate*}
{CertificateVerify*} {CertificateVerify*}
{Finished} --------> {Finished} -------->
[Application Data] <-------> [Application Data] [Application Data] <-------> [Application Data]
Figure 2: Message flow for a full handshake with mismatched Figure 2: Message flow for a full handshake with mismatched
parameters parameters
[[OPEN ISSUE: Should we restart the handshake hash? [[OPEN ISSUE: Should we restart the handshake hash?
https://github.com/tlswg/tls13-spec/issues/104.]] [[OPEN ISSUE: We https://github.com/tlswg/tls13-spec/issues/104.]] [[OPEN ISSUE: We
need to make sure that this flow doesn't introduce downgrade issues. need to make sure that this flow doesn't introduce downgrade issues.
Potential options include continuing the handshake hashes (as long as Potential options include continuing the handshake hashes (as long as
clients don't change their opinion of the server's capabilities with clients don't change their opinion of the server's capabilities with
aborted handshakes) and requiring the client to send the same aborted handshakes) and requiring the client to send the same
skipping to change at page 35, line 47 skipping to change at page 36, line 7
If no common cryptographic parameters can be negotiated, the server If no common cryptographic parameters can be negotiated, the server
will send a "handshake_failure" or "insufficient_security" fatal will send a "handshake_failure" or "insufficient_security" fatal
alert (see Section 6.1). alert (see Section 6.1).
TLS also allows several optimized variants of the basic handshake, as TLS also allows several optimized variants of the basic handshake, as
described below. described below.
6.2.2. Zero-RTT Exchange 6.2.2. Zero-RTT Exchange
TLS 1.3 supports a "0-RTT" mode in which the client can send TLS 1.3 supports a "0-RTT" mode in which the client can both
application data as well as its Certificate and CertificateVerify (if authenticate and send application on its first flight, thus reducing
client authentication is requested) on its first flight, thus handshake latency. In order to enable this functionality, the server
reducing handshake latency. In order to enable this functionality, provides a ServerConfiguration message containing a long-term (EC)DH
the server provides a ServerConfiguration message containing a long- share. On future connections to the same server, the client can use
term (EC)DH share. On future connections to the same server, the that share to protect the first-flight data.
client can use that share to encrypt the first-flight data.
Client Server Client Server
ClientHello ClientHello
+ KeyShare + key_share
+ EarlyDataIndication + early_data
(EncryptedExtensions) ^ (Certificate*)
(Certificate*) 0-RTT | (CertificateVerify*)
(CertificateVerify*) Data | (Finished)
(Application Data) --------> v (Application Data*)
ServerHello (end_of_early_data) -------->
+ KeyShare ServerHello
+ EarlyDataIndication + early_data
{EncryptedExtensions} + key_share
{ServerConfiguration*} {EncryptedExtensions}
{Certificate*} {CertificateRequest*}
{CertificateRequest*} {ServerConfiguration*}
{CertificateVerify*} {Certificate*}
<-------- {Finished} {CertificateVerify*}
{Finished} --------> <-------- {Finished}
{Certificate*}
{CertificateVerify*}
{Finished} -------->
[Application Data] <-------> [Application Data] [Application Data] <-------> [Application Data]
() Indicates messages protected using keys * Indicates optional or situation-dependent
derived from the static secret. messages that are not always sent.
() Indicates messages protected using keys
derived from the static secret.
{} Indicates messages protected using keys
derived from the ephemeral secret.
[] Indicates messages protected using keys
derived from the master secret.
Figure 3: Message flow for a zero round trip handshake Figure 3: Message flow for a zero round trip handshake
Note: because sequence numbers continue to increment between the As shown in Figure 3, the Zero-RTT data is just added to the 1-RTT
initial (early) application data and the application data sent after handshake in the first flight. Specifically, the client sends its
the handshake has completed, an attacker cannot remove early Authentication messages after the ClientHello, followed by any
application data messages. application data. The rest of the handshake messages are the same as
with Figure 1. This implies that the server can request client
authentication even if the client offers a certificate on its first
flight. This is consistent with the server being able to ask for
client authentication after the handshake is complete (see
Section 6.3.5.2). When offering PSK support, the "pre_shared_key"
extension will be used instead of (or in addition to) the "key_share"
extension as specified above.
IMPORTANT NOTE: The security properties for 0-RTT data (regardless of IMPORTANT NOTE: The security properties for 0-RTT data (regardless of
the cipher suite) are weaker than those for other kinds of TLS data. the cipher suite) are weaker than those for other kinds of TLS data.
Specifically: Specifically:
1. This data is not forward secure, because it is encrypted solely 1. This data is not forward secret, because it is encrypted solely
with the server's semi-static (EC)DH share. with the server's semi-static (EC)DH share.
2. There are no guarantees of non-replay between connections. 2. There are no guarantees of non-replay between connections.
Unless the server takes special measures outside those provided Unless the server takes special measures outside those provided
by TLS (See Section 6.3.2.5.2), the server has no guarantee that by TLS (See Section 6.3.2.5.2), the server has no guarantee that
the same 0-RTT data was not transmitted on multiple 0-RTT the same 0-RTT data was not transmitted on multiple 0-RTT
connections. This is especially relevant if the data is connections. This is especially relevant if the data is
authenticated either with TLS client authentication or inside the authenticated either with TLS client authentication or inside the
application layer protocol. However, 0-RTT data cannot be application layer protocol. However, 0-RTT data cannot be
duplicated within a connection (i.e., the server will not process duplicated within a connection (i.e., the server will not process
the same data twice for the same connection) and also cannot be the same data twice for the same connection) and also cannot be
sent as if it were ordinary TLS data. sent as if it were ordinary TLS data.
3. If the server key is compromised, and client authentication is 3. If the server key is compromised, then the attacker can tamper
used, then the attacker can impersonate the client to the server with the 0-RTT data without detection. If the client's ephemeral
(as it knows the traffic key). share is compromised and client authentication is used, then the
attacker can impersonate the client on subsequent connections.
6.2.3. Resumption and PSK 6.2.3. Resumption and PSK
Finally, TLS provides a pre-shared key (PSK) mode which allows a Finally, TLS provides a pre-shared key (PSK) mode which allows a
client and server who share an existing secret (e.g., a key client and server who share an existing secret (e.g., a key
established out of band) to establish a connection authenticated by established out of band) to establish a connection authenticated by
that key. PSKs can also be established in a previous session and that key. PSKs can also be established in a previous session and
then reused ("session resumption"). Once a handshake has completed, then reused ("session resumption"). Once a handshake has completed,
the server can send the client a PSK identity which corresponds to a the server can send the client a PSK identity which corresponds to a
key derived from the initial handshake (See Section 6.3.11). The key derived from the initial handshake (See Section 6.3.5.1). The
client can then use that PSK identity in future handshakes to client can then use that PSK identity in future handshakes to
negotiate use of the PSK; if the server accepts it, then the security negotiate use of the PSK; if the server accepts it, then the security
context of the original connection is tied to the new connection. In context of the original connection is tied to the new connection. In
TLS 1.2 and below, this functionality was provided by "session TLS 1.2 and below, this functionality was provided by "session
resumption" and "session tickets" [RFC5077]. Both mechanisms are resumption" and "session tickets" [RFC5077]. Both mechanisms are
obsoleted in TLS 1.3. obsoleted in TLS 1.3.
PSK cipher suites can either use PSK in combination with an (EC)DHE PSK cipher suites can either use PSK in combination with an (EC)DHE
exchange in order to provide forward secrecy in combination with exchange in order to provide forward secrecy in combination with
shared keys, or can use PSKs alone, at the cost of losing forward shared keys, or can use PSKs alone, at the cost of losing forward
secrecy. secrecy.
Figure 4 shows a pair of handshakes in which the first establishes a Figure 4 shows a pair of handshakes in which the first establishes a
PSK and the second uses it: PSK and the second uses it:
Client Server Client Server
Initial Handshake: Initial Handshake:
ClientHello ClientHello
+ KeyShare --------> + key_share -------->
ServerHello ServerHello
+ KeyShare + key_share
{EncryptedExtensions} {EncryptedExtensions}
{CertificateRequest*}
{ServerConfiguration*} {ServerConfiguration*}
{Certificate*} {Certificate*}
{CertificateRequest*}
{CertificateVerify*} {CertificateVerify*}
<-------- {Finished} <-------- {Finished}
{Certificate*} {Certificate*}
{CertificateVerify*} {CertificateVerify*}
{Finished} --------> {Finished} -------->
<-------- [NewSessionTicket] <-------- [NewSessionTicket]
[Application Data] <-------> [Application Data] [Application Data] <-------> [Application Data]
Subsequent Handshake: Subsequent Handshake:
ClientHello ClientHello
+ KeyShare + key_share
+ PreSharedKeyExtension --------> + pre_shared_key -------->
ServerHello ServerHello
+ PreSharedKeyExtension + pre_shared_key
{EncryptedExtensions} {EncryptedExtensions}
<-------- {Finished} <-------- {Finished}
{Finished} --------> {Finished} -------->
[Application Data] <-------> [Application Data] [Application Data] <-------> [Application Data]
Figure 4: Message flow for resumption and PSK Figure 4: Message flow for resumption and PSK
As the server is authenticating via a PSK, it does not send a As the server is authenticating via a PSK, it does not send a
Certificate or a CertificateVerify. PSK-based resumption cannot be Certificate or a CertificateVerify. PSK-based resumption cannot be
used to provide a new ServerConfiguration. Note that the client used to provide a new ServerConfiguration. Note that the client
skipping to change at page 39, line 19 skipping to change at page 39, line 30
client_hello(1), client_hello(1),
server_hello(2), server_hello(2),
session_ticket(4), session_ticket(4),
hello_retry_request(6), hello_retry_request(6),
encrypted_extensions(8), encrypted_extensions(8),
certificate(11), certificate(11),
certificate_request(13), certificate_request(13),
certificate_verify(15), certificate_verify(15),
server_configuration(17), server_configuration(17),
finished(20), finished(20),
key_update(24),
(255) (255)
} HandshakeType; } HandshakeType;
struct { struct {
HandshakeType msg_type; /* handshake type */ HandshakeType msg_type; /* handshake type */
uint24 length; /* bytes in message */ uint24 length; /* bytes in message */
select (HandshakeType) { select (HandshakeType) {
case client_hello: ClientHello; case client_hello: ClientHello;
case server_hello: ServerHello; case server_hello: ServerHello;
case hello_retry_request: HelloRetryRequest; case hello_retry_request: HelloRetryRequest;
case encrypted_extensions: EncryptedExtensions; case encrypted_extensions: EncryptedExtensions;
case certificate_request: CertificateRequest;
case server_configuration:ServerConfiguration; case server_configuration:ServerConfiguration;
case certificate: Certificate; case certificate: Certificate;
case certificate_request: CertificateRequest;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case finished: Finished; case finished: Finished;
case session_ticket: NewSessionTicket; case session_ticket: NewSessionTicket;
case key_update: KeyUpdate;
} body; } body;
} Handshake; } Handshake;
The TLS Handshake Protocol messages are presented below in the order The TLS Handshake Protocol messages are presented below in the order
they MUST be sent; sending handshake messages in an unexpected order they MUST be sent; sending handshake messages in an unexpected order
results in an "unexpected_message" fatal error. Unneeded handshake results in an "unexpected_message" fatal error. Unneeded handshake
messages can be omitted, however. messages can be omitted, however.
New handshake message types are assigned by IANA as described in New handshake message types are assigned by IANA as described in
Section 11. Section 11.
6.3.1. Hello Messages 6.3.1. Key Exchange Messages
The hello phase messages are used to exchange security enhancement The key exchange messages are used to exchange security capabilities
capabilities between the client and server. When a new session between the client and server and to establish the traffic keys used
begins, the record layer's connection state AEAD algorithm is to protect the handshake and the data.
initialized to NULL_NULL.
6.3.1.1. Client Hello 6.3.1.1. Client Hello
When this message will be sent: When this message will be sent:
When a client first connects to a server, it is required to send When a client first connects to a server, it is required to send
the ClientHello as its first message. The client will also send a the ClientHello as its first message. The client will also send a
ClientHello when the server has responded to its ClientHello with ClientHello when the server has responded to its ClientHello with
a ServerHello that selects cryptographic parameters that don't a ServerHello that selects cryptographic parameters that don't
match the client's KeyShare extension. In that case, the client match the client's "key_share" extension. In that case, the
MUST send the same ClientHello (without modification) except client MUST send the same ClientHello (without modification)
including a new KeyShareEntry as the lowest priority share (i.e., except including a new KeyShareEntry as the lowest priority share
appended to the list of shares in the KeyShare message). [[OPEN (i.e., appended to the list of shares in the KeyShare message).
ISSUE: New random values? See: https://github.com/tlswg/tls13- [[OPEN ISSUE: New random values? See: https://github.com/tlswg/
spec/issues/185]] If a server receives a ClientHello at any other tls13-spec/issues/185]] If a server receives a ClientHello at any
time, it MUST send a fatal "unexpected_message" alert and close other time, it MUST send a fatal "unexpected_message" alert and
the connection. close the connection.
Structure of this message: Structure of this message:
The ClientHello message includes a random structure, which is used The ClientHello message includes a random structure, which is used
later in the protocol. later in the protocol.
struct { struct {
opaque random_bytes[32]; opaque random_bytes[32];
} Random; } Random;
random_bytes random_bytes
32 bytes generated by a secure random number generator. See 32 bytes generated by a secure random number generator. See
Appendix B for additional information. Appendix B for additional information.
TLS 1.3 server implementations which respond to a ClientHello with a
client_version indicating TLS 1.2 or below MUST set the first eight
bytes of their Random value to the bytes:
44 4F 57 4E 47 52 44 01
TLS 1.2 server implementations which respond to a ClientHello with a
client_version indicating TLS 1.1 or below SHOULD set the first eight
bytes of their Random value to the bytes:
44 4F 57 4E 47 52 44 00
TLS 1.3 clients receiving a TLS 1.2 or below ServerHello MUST check
that the top eight octets are not equal to either of these values.
TLS 1.2 clients SHOULD also perform this check if the ServerHello
indicates TLS 1.1 or below. If a match is found the client MUST
abort the handshake with a fatal "illegal_parameter" alert. This
mechanism provides limited protection against downgrade attacks over
and above that provided by the Finished exchange: because the
ServerKeyExchange includes a signature over both random values, it is
not possible for an active attacker to modify the randoms without
detection as long as ephemeral ciphers are used. It does not provide
downgrade protection when static RSA is used.
Note: This is an update to TLS 1.2 so in practice many TLS 1.2
clients and servers will not behave as specified above.
Note: Versions of TLS prior to TLS 1.3 used the top 32 bits of the Note: Versions of TLS prior to TLS 1.3 used the top 32 bits of the
Random value to encode the time since the UNIX epoch. Random value to encode the time since the UNIX epoch. The sentinel
value above was selected to avoid conflicting with any valid TLS 1.2
Random value and to have a low (2^{-64}) probability of colliding
with randomly selected Random values.
The cipher suite list, passed from the client to the server in the The cipher suite list, passed from the client to the server in the
ClientHello message, contains the combinations of cryptographic ClientHello message, contains the combinations of cryptographic
algorithms supported by the client in order of the client's algorithms supported by the client in order of the client's
preference (favorite choice first). Each cipher suite defines a key preference (favorite choice first). Each cipher suite defines a key
exchange algorithm, a record protection algorithm (including secret exchange algorithm, a record protection algorithm (including secret
key length) and a hash to be used with HKDF. The server will select key length) and a hash to be used with HKDF. The server will select
a cipher suite or, if no acceptable choices are presented, return a a cipher suite or, if no acceptable choices are presented, return a
"handshake_failure" alert and close the connection. If the list "handshake_failure" alert and close the connection. If the list
contains cipher suites the server does not recognize, support, or contains cipher suites the server does not recognize, support, or
wish to use, the server MUST ignore those cipher suites, and process wish to use, the server MUST ignore those cipher suites, and process
the remaining ones as usual. the remaining ones as usual.
uint8 CipherSuite[2]; /* Cryptographic suite selector */ uint8 CipherSuite[2]; /* Cryptographic suite selector */
enum { null(0), (255) } CompressionMethod;
struct { struct {
ProtocolVersion client_version = { 3, 4 }; /* TLS v1.3 */ ProtocolVersion client_version = { 3, 4 }; /* TLS v1.3 */
Random random; Random random;
SessionID session_id; opaque legacy_session_id<0..32>;
CipherSuite cipher_suites<2..2^16-2>; CipherSuite cipher_suites<2..2^16-2>;
CompressionMethod compression_methods<1..2^8-1>; opaque legacy_compression_methods<1..2^8-1>;
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
} ClientHello; } ClientHello;
TLS allows extensions to follow the compression_methods field in an TLS allows extensions to follow the compression_methods field in an
extensions block. The presence of extensions can be detected by extensions block. The presence of extensions can be detected by
determining whether there are bytes following the compression_methods determining whether there are bytes following the compression_methods
at the end of the ClientHello. Note that this method of detecting at the end of the ClientHello. Note that this method of detecting
optional data differs from the normal TLS method of having a optional data differs from the normal TLS method of having a
variable-length field, but it is used for compatibility with TLS variable-length field, but it is used for compatibility with TLS
before extensions were defined. before extensions were defined.
skipping to change at page 41, line 36 skipping to change at page 42, line 34
client_version client_version
The version of the TLS protocol by which the client wishes to The version of the TLS protocol by which the client wishes to
communicate during this session. This SHOULD be the latest communicate during this session. This SHOULD be the latest
(highest valued) version supported by the client. For this (highest valued) version supported by the client. For this
version of the specification, the version will be { 3, 4 }. (See version of the specification, the version will be { 3, 4 }. (See
Appendix C for details about backward compatibility.) Appendix C for details about backward compatibility.)
random random
A client-generated random structure. A client-generated random structure.
session_id legacy_session_id
Versions of TLS prior to TLS 1.3 supported a session resumption Versions of TLS before TLS 1.3 supported a session resumption
feature which has been merged with Pre-Shared Keys in this version feature which has been merged with Pre-Shared Keys in this version
(see Section 6.2.3). This field MUST be ignored by a server (see Section 6.2.3). This field MUST be ignored by a server
negotiating TLS 1.3 and should be set as a zero length vector negotiating TLS 1.3 and SHOULD be set as a zero length vector
(i.e., a single zero byte length field) by clients which do not (i.e., a single zero byte length field) by clients which do not
have a cached session_id set by a pre-TLS 1.3 server. have a cached session ID set by a pre-TLS 1.3 server.
cipher_suites cipher_suites
This is a list of the cryptographic options supported by the This is a list of the cryptographic options supported by the
client, with the client's first preference first. Values are client, with the client's first preference first. Values are
defined in Appendix A.4. defined in Appendix A.4.
compression_methods legacy_compression_methods
Versions of TLS before 1.3 supported compression and the list of Versions of TLS before 1.3 supported compression and the list of
compression methods was supplied in this field. For any TLS 1.3 compression methods was supplied in this field. For any TLS 1.3
ClientHello, this field MUST contain only the "null" compression ClientHello, this vector MUST contain exactly one byte set to
method with the code point of 0. If a TLS 1.3 ClientHello is zero, which corresponds to the "null" compression method in prior
received with any other value in this field, the server MUST versions of TLS. If a TLS 1.3 ClientHello is received with any
generate a fatal "illegal_parameter" alert. Note that TLS 1.3 other value in this field, the server MUST generate a fatal
servers may receive TLS 1.2 or prior ClientHellos which contain "illegal_parameter" alert. Note that TLS 1.3 servers might
other compression methods and MUST follow the procedures for the receive TLS 1.2 or prior ClientHellos which contain other
compression methods and MUST follow the procedures for the
appropriate prior version of TLS. appropriate prior version of TLS.
extensions extensions
Clients MAY request extended functionality from servers by sending Clients MAY request extended functionality from servers by sending
data in the extensions field. The actual "Extension" format is data in the extensions field. The actual "Extension" format is
defined in Section 6.3.2. defined in Section 6.3.2.
In the event that a client requests additional functionality using In the event that a client requests additional functionality using
extensions, and this functionality is not supplied by the server, the extensions, and this functionality is not supplied by the server, the
client MAY abort the handshake. A server MUST accept ClientHello client MAY abort the handshake. A server MUST accept ClientHello
skipping to change at page 42, line 33 skipping to change at page 43, line 32
After sending the ClientHello message, the client waits for a After sending the ClientHello message, the client waits for a
ServerHello or HelloRetryRequest message. ServerHello or HelloRetryRequest message.
6.3.1.2. Server Hello 6.3.1.2. Server Hello
When this message will be sent: When this message will be sent:
The server will send this message in response to a ClientHello The server will send this message in response to a ClientHello
message when it was able to find an acceptable set of algorithms message when it was able to find an acceptable set of algorithms
and the client's KeyShare extension was acceptable. If the client and the client's "key_share" extension was acceptable. If the
proposed groups are not acceptable by the server, it will respond client proposed groups are not acceptable by the server, it will
with a "handshake_failure" fatal alert. respond with a "handshake_failure" fatal alert.
Structure of this message: Structure of this message:
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
CipherSuite cipher_suite; CipherSuite cipher_suite;
select (extensions_present) { select (extensions_present) {
case false: case false:
struct {}; struct {};
skipping to change at page 43, line 29 skipping to change at page 44, line 29
cipher_suite cipher_suite
The single cipher suite selected by the server from the list in The single cipher suite selected by the server from the list in
ClientHello.cipher_suites. For resumed sessions, this field is ClientHello.cipher_suites. For resumed sessions, this field is
the value from the state of the session being resumed. [[TODO: the value from the state of the session being resumed. [[TODO:
interaction with PSK.]] interaction with PSK.]]
extensions extensions
A list of extensions. Note that only extensions offered by the A list of extensions. Note that only extensions offered by the
client can appear in the server's list. In TLS 1.3 as opposed to client can appear in the server's list. In TLS 1.3 as opposed to
previous versions of TLS, the server's extensions are split previous versions of TLS, the server's extensions are split
between the ServerHello and the EncryptedExtensions Section 6.3.3 between the ServerHello and the EncryptedExtensions
message. The ServerHello MUST only include extensions which are Section 6.3.3.1 message. The ServerHello MUST only include
required to establish the cryptographic context. extensions which are required to establish the cryptographic
context. Currently the only such extensions are "key_share",
"pre_shared_key", and "early_data". Clients MUST check the
ServerHello for the presence of any forbidden extensions and if
any are found MUST terminate the handshake with a
"illegal_parameter" alert.
6.3.1.3. Hello Retry Request 6.3.1.3. Hello Retry Request
When this message will be sent: When this message will be sent:
Servers send this message in response to a ClientHello message Servers send this message in response to a ClientHello message
when it was able to find an acceptable set of algorithms and when it was able to find an acceptable set of algorithms and
groups that are mutually supported, but the client's KeyShare did groups that are mutually supported, but the client's KeyShare did
not contain an acceptable offer. If it cannot find such a match, not contain an acceptable offer. If it cannot find such a match,
it will respond with a "handshake_failure" alert. it will respond with a fatal "handshake_failure" alert.
Structure of this message: Structure of this message:
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
CipherSuite cipher_suite; CipherSuite cipher_suite;
NamedGroup selected_group; NamedGroup selected_group;
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
} HelloRetryRequest; } HelloRetryRequest;
skipping to change at page 44, line 4 skipping to change at page 45, line 13
Structure of this message: Structure of this message:
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
CipherSuite cipher_suite; CipherSuite cipher_suite;
NamedGroup selected_group; NamedGroup selected_group;
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
} HelloRetryRequest; } HelloRetryRequest;
[[OPEN ISSUE: Merge in DTLS Cookies?]] [[OPEN ISSUE: Merge in DTLS Cookies?]]
selected_group selected_group
The group which the client MUST use for its new ClientHello. The mutually supported group the server intends to negotiate and
is requesting a retried ClientHello/KeyShare for.
The "server_version", "cipher_suite" and "extensions" fields have the The server_version, cipher_suite, and extensions fields have the same
same meanings as their corresponding values in the ServerHello. The meanings as their corresponding values in the ServerHello. The
server SHOULD send only the extensions necessary for the client to server SHOULD send only the extensions necessary for the client to
generate a correct ClientHello pair. generate a correct ClientHello pair. As with ServerHello, a
HelloRetryRequest MUST NOT contain any extensions that were not first
offered by the client in its ClientHello.
Upon receipt of a HelloRetryRequest, the client MUST first verify Upon receipt of a HelloRetryRequest, the client MUST first verify
that the "selected_group" field corresponds to a group which was that the selected_group field corresponds to a group which was
provided in the "supported_groups" extension in the original provided in the "supported_groups" extension in the original
ClientHello. It MUST then verify that the "selected_group" field ClientHello. It MUST then verify that the selected_group field does
does not correspond to a group which was provided in the "key_share" not correspond to a group which was provided in the "key_share"
extension in the original ClientHello. If either of these checks extension in the original ClientHello. If either of these checks
fails, then the client MUST abort the handshake with a fatal fails, then the client MUST abort the handshake with a fatal
"handshake_failure" alert. Clients SHOULD also abort with "handshake_failure" alert. Clients SHOULD also abort with
"handshake_failure" in response to any second HelloRetryRequest which "handshake_failure" in response to any second HelloRetryRequest which
was sent in the same connection (i.e., where the ClientHello was was sent in the same connection (i.e., where the ClientHello was
itself in response to a HelloRetryRequest). itself in response to a HelloRetryRequest).
Otherwise, the client MUST send a ClientHello with a new KeyShare Otherwise, the client MUST send a ClientHello with an updated
extension to the server. The client MUST append a new KeyShareEntry KeyShare extension to the server. The client MUST append a new
list which is consistent with the "selected_group" field to the KeyShareEntry for the group indicated in the selected_group field to
groups in its original KeyShare. the groups in its original KeyShare.
Upon re-sending the ClientHello and receiving the server's Upon re-sending the ClientHello and receiving the server's
ServerHello/KeyShare, the client MUST verify that the selected ServerHello/KeyShare, the client MUST verify that the selected
CipherSuite and NamedGroup match that supplied in the CipherSuite and NamedGroup match that supplied in the
HelloRetryRequest. HelloRetryRequest. If either of these values differ, the client MUST
abort the connection with a fatal "handshake_failure" alert.
[[OPEN ISSUE: https://github.com/tlswg/tls13-spec/issues/104]] [[OPEN ISSUE: https://github.com/tlswg/tls13-spec/issues/104]]
6.3.2. Hello Extensions 6.3.2. Hello Extensions
The extension format is: The extension format is:
struct { struct {
ExtensionType extension_type; ExtensionType extension_type;
opaque extension_data<0..2^16-1>; opaque extension_data<0..2^16-1>;
skipping to change at page 47, line 33 skipping to change at page 48, line 33
sha1(2), sha1(2),
sha256(4), sha384(5), sha512(6), sha256(4), sha384(5), sha512(6),
(255) (255)
} HashAlgorithm; } HashAlgorithm;
enum { enum {
rsa(1), rsa(1),
dsa(2), dsa(2),
ecdsa(3), ecdsa(3),
rsapss(4), rsapss(4),
eddsa(5),
(255) (255)
} SignatureAlgorithm; } SignatureAlgorithm;
struct { struct {
HashAlgorithm hash; HashAlgorithm hash;
SignatureAlgorithm signature; SignatureAlgorithm signature;
} SignatureAndHashAlgorithm; } SignatureAndHashAlgorithm;
SignatureAndHashAlgorithm SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>; supported_signature_algorithms<2..2^16-2>;
skipping to change at page 48, line 9 skipping to change at page 49, line 13
in descending order of preference. in descending order of preference.
Note: Because not all signature algorithms and hash algorithms may be Note: Because not all signature algorithms and hash algorithms may be
accepted by an implementation (e.g., ECDSA with SHA-256, but not SHA- accepted by an implementation (e.g., ECDSA with SHA-256, but not SHA-
384), algorithms here are listed in pairs. 384), algorithms here are listed in pairs.
hash hash
This field indicates the hash algorithms which may be used. The This field indicates the hash algorithms which may be used. The
values indicate support for unhashed data, SHA-1, SHA-256, SHA- values indicate support for unhashed data, SHA-1, SHA-256, SHA-
384, and SHA-512 [SHS], respectively. The "none" value is 384, and SHA-512 [SHS], respectively. The "none" value is
provided for future extensibility, in case of a signature provided for signature algorithms which do not require hashing
algorithm which does not require hashing before signing. Previous before signing, such as EdDSA. Previous versions of TLS supported
versions of TLS supported MD5 and SHA-1. These algorithms are now MD5, SHA-1, and SHA-224. These algorithms are now deprecated.
deprecated and MUST NOT be offered by TLS 1.3 implementations. MD5 and SHA-224 MUST NOT be offered by TLS 1.3 implementations;
SHA-1 SHOULD NOT be offered, however clients willing to negotiate SHA-1 SHOULD NOT be offered. Clients MAY offer support for SHA-1
use of TLS 1.2 MAY offer support for SHA-1 for backwards for backwards compatibility, either with TLS 1.2 servers or for
compatibility with old servers. servers that have certification paths with signatures based on
SHA-1.
signature signature
This field indicates the signature algorithm that may be used. This field indicates the signature algorithm that may be used.
The values indicate RSASSA-PKCS1-v1_5 [RFC3447], DSA [DSS], ECDSA The values indicate RSASSA-PKCS1-v1_5 [RFC3447], DSA [DSS], ECDSA
[ECDSA], and RSASSA-PSS [RFC3447] respectively. Because all RSA [ECDSA], RSASSA-PSS [RFC3447], and EdDSA [I-D.irtf-cfrg-eddsa]
signatures used in signed TLS handshake messages (see respectively. Because all RSA signatures used in signed TLS
Section 4.9.1), as opposed to those in certificates, are RSASSA- handshake messages (see Section 4.8.1), as opposed to those in
PSS, the "rsa" value refers solely to signatures which appear in certificates, are RSASSA-PSS, the "rsa" value refers solely to
certificates. The use of DSA and anonymous is deprecated. signatures which appear in certificates. The use of DSA and
Previous versions of TLS supported DSA. DSA is deprecated as of anonymous is deprecated. Previous versions of TLS supported DSA.
TLS 1.3 and SHOULD NOT be offered or negotiated by any DSA is deprecated as of TLS 1.3 and SHOULD NOT be offered or
implementation. negotiated by any implementation.
The semantics of this extension are somewhat complicated because the The semantics of this extension are somewhat complicated because the
cipher suite indicates permissible signature algorithms but not hash cipher suite indicates permissible signature algorithms but not hash
algorithms. Section 6.3.4 and Section 6.3.2.3 describe the algorithms. Section 6.3.4.1.1 and Section 6.3.2.3 describe the
appropriate rules. appropriate rules.
Clients offering support for SHA-1 for TLS 1.2 servers MUST do so by Clients offering support for SHA-1 for backwards compatibility MUST
listing those hash/signature pairs as the lowest priority (listed do so by listing those hash/signature pairs as the lowest priority
after all other pairs in the supported_signature_algorithms vector). (listed after all other pairs in the supported_signature_algorithms
TLS 1.3 servers MUST NOT offer a SHA-1 signed certificate unless no vector). TLS 1.3 servers MUST NOT offer a SHA-1 signed certificate
valid certificate chain can be produced without it (see unless no valid certificate chain can be produced without it (see
Section 6.3.4). Section 6.3.4.1.1).
Note: TLS 1.3 servers MAY receive TLS 1.2 ClientHellos which do not The signatures on certificates that are self-signed or certificates
that are trust anchors are not validated since they begin a
certification path (see [RFC5280], Section 3.2). A certificate that
begins a certification path MAY use a hash or signature algorithm
that is not advertised as being supported in the
"signature_algorithms" extension.
Note: TLS 1.3 servers might receive TLS 1.2 ClientHellos which do not
contain this extension. If those servers are willing to negotiate contain this extension. If those servers are willing to negotiate
TLS 1.2, they MUST behave in accordance with the requirements of TLS 1.2, they MUST behave in accordance with the requirements of
[RFC5246] when negotiating that version. [RFC5246] when negotiating that version.
6.3.2.2. Negotiated Groups 6.3.2.2. Negotiated Groups
When sent by the client, the "supported_groups" extension indicates When sent by the client, the "supported_groups" extension indicates
the named groups which the client supports, ordered from most the named groups which the client supports, ordered from most
preferred to least preferred. preferred to least preferred.
skipping to change at page 49, line 29 skipping to change at page 51, line 9
across all cipher suites, then the server MUST generate a fatal across all cipher suites, then the server MUST generate a fatal
"handshake_failure" alert. "handshake_failure" alert.
The "extension_data" field of this extension contains a The "extension_data" field of this extension contains a
"NamedGroupList" value: "NamedGroupList" value:
enum { enum {
// Elliptic Curve Groups. // Elliptic Curve Groups.
secp256r1 (23), secp384r1 (24), secp521r1 (25), secp256r1 (23), secp384r1 (24), secp521r1 (25),
// ECDH functions.
ecdh_x25519 (29), ecdh_x448 (30),
// Signature-only curves.
eddsa_ed25519 (31), eddsa_ed448 (32),
// Finite Field Groups. // Finite Field Groups.
ffdhe2048 (256), ffdhe3072 (257), ffdhe4096 (258), ffdhe2048 (256), ffdhe3072 (257), ffdhe4096 (258),
ffdhe6144 (259), ffdhe8192 (260), ffdhe6144 (259), ffdhe8192 (260),
// Reserved Code Points. // Reserved Code Points.
ffdhe_private_use (0x01FC..0x01FF), ffdhe_private_use (0x01FC..0x01FF),
ecdhe_private_use (0xFE00..0xFEFF), ecdhe_private_use (0xFE00..0xFEFF),
(0xFFFF) (0xFFFF)
} NamedGroup; } NamedGroup;
struct { struct {
NamedGroup named_group_list<1..2^16-1>; NamedGroup named_group_list<1..2^16-1>;
} NamedGroupList; } NamedGroupList;
secp256r1, etc. secp256r1, etc.
Indicates support of the corresponding named curve. Note that Indicates support of the corresponding named curve. Note that
some curves are also recommended in ANSI X9.62 [X962] and FIPS some curves are also recommended in ANSI X9.62 [X962] and FIPS
186-4 [DSS]. Values 0xFE00 through 0xFEFF are reserved for 186-4 [DSS]. Values 0xFE00 through 0xFEFF are reserved for
private use. private use.
ecdh_x25519 and ecdh_x448
Indicates support of the corresponding ECDH functions X25519 and
X448.
eddsa_ed25519 and eddsa_ed448
Indicates support of the corresponding curve for signatures.
ffdhe2048, etc. ffdhe2048, etc.
Indicates support of the corresponding finite field group, defined Indicates support of the corresponding finite field group, defined
in [I-D.ietf-tls-negotiated-ff-dhe]. Values 0x01FC through 0x01FF in [I-D.ietf-tls-negotiated-ff-dhe]. Values 0x01FC through 0x01FF
are reserved for private use. are reserved for private use.
Items in named_curve_list are ordered according to the client's Items in named_group_list are ordered according to the client's
preferences (most preferred choice first). preferences (most preferred choice first).
As an example, a client that only supports secp256r1 (aka NIST P-256; As an example, a client that only supports secp256r1 (aka NIST P-256;
value 23 = 0x0017) and secp384r1 (aka NIST P-384; value 24 = 0x0018) value 23 = 0x0017) and secp384r1 (aka NIST P-384; value 24 = 0x0018)
and prefers to use secp256r1 would include a TLS extension consisting and prefers to use secp256r1 would include a TLS extension consisting
of the following octets. Note that the first two octets indicate the of the following octets. Note that the first two octets indicate the
extension type (Supported Group Extension): extension type ("supported_groups" extension):
00 0A 00 06 00 04 00 17 00 18 00 0A 00 06 00 04 00 17 00 18
NOTE: A server participating in an ECDHE-ECDSA key exchange may use NOTE: A server participating in an ECDHE-ECDSA key exchange may use
different curves for (i) the ECDSA key in its certificate, and (ii) different curves for (i) the ECDSA or EdDSA key in its certificate,
the ephemeral ECDH key in its KeyShare extension. The server must and (ii) the ephemeral ECDH key in its "key_share" extension. The
consider the supported groups in both cases. server must consider the supported groups in both cases.
[[TODO: IANA Considerations.]] [[TODO: IANA Considerations.]]
6.3.2.3. Key Share 6.3.2.3. Key Share
The "key_share" extension contains the endpoint's cryptographic The "key_share" extension contains the endpoint's cryptographic
parameters for non-PSK key establishment methods (currently DHE or parameters for non-PSK key establishment methods (currently DHE or
ECDHE). ECDHE).
Clients which offer one or more (EC)DHE cipher suites MUST send at Clients which offer one or more (EC)DHE cipher suites MUST send this
least one supported KeyShare value and servers MUST NOT negotiate any extension and SHOULD send at least one supported KeyShareEntry value.
of these cipher suites unless a supported value was provided. If Servers MUST NOT negotiate any of these cipher suites unless a
this extension is not provided in a ServerHello or retried supported value was provided. If this extension is not provided in a
ClientHello, and the peer is offering (EC)DHE cipher suites, then the ServerHello or ClientHello, and the peer is offering (EC)DHE cipher
endpoint MUST close the connection with a fatal "missing_extension" suites, then the endpoint MUST close the connection with a fatal
alert. (see Section 8.2) "missing_extension" alert. (see Section 8.2) Clients MAY send an
empty client_shares vector in order to request group selection from
the server at the cost of an additional round trip. (see
Section 6.3.1.3)
struct { struct {
NamedGroup group; NamedGroup group;
opaque key_exchange<1..2^16-1>; opaque key_exchange<1..2^16-1>;
} KeyShareEntry; } KeyShareEntry;
group group
The named group for the key being exchanged. Finite Field Diffie- The named group for the key being exchanged. Finite Field Diffie-
Hellman [DH] parameters are described in Section 6.3.2.3.1; Hellman [DH] parameters are described in Section 6.3.2.3.1;
Elliptic Curve Diffie-Hellman parameters are described in Elliptic Curve Diffie-Hellman parameters are described in
Section 6.3.2.3.2. Section 6.3.2.3.2. Signature-only curves, currently eddsa_ed25519
(31) and eddsa_ed448 (32), MUST NOT be used for key exchange.
key_exchange key_exchange
Key exchange information. The contents of this field are Key exchange information. The contents of this field are
determined by the specified group and its corresponding determined by the specified group and its corresponding
definition. Endpoints MUST NOT send empty or otherwise invalid definition. Endpoints MUST NOT send empty or otherwise invalid
key_exchange values for any reason. key_exchange values for any reason.
The "extension_data" field of this extension contains a "KeyShare" The "extension_data" field of this extension contains a "KeyShare"
value: value:
skipping to change at page 51, line 20 skipping to change at page 53, line 20
case client: case client:
KeyShareEntry client_shares<4..2^16-1>; KeyShareEntry client_shares<4..2^16-1>;
case server: case server:
KeyShareEntry server_share; KeyShareEntry server_share;
} }
} KeyShare; } KeyShare;
client_shares client_shares
A list of offered KeyShareEntry values in descending order of A list of offered KeyShareEntry values in descending order of
client preference. This vector MUST NOT be empty. Clients not client preference. This vector MAY be empty if the client is
providing a KeyShare MUST instead omit this extension from the requesting a HelloRetryRequest. The ordering of values here
ClientHello. SHOULD match that of the ordering of offered support in the
"supported_groups" extension.
server_shares server_share
A single KeyShareEntry value for the negotiated cipher suite. A single KeyShareEntry value for the negotiated cipher suite.
Servers MUST NOT send a KeyShareEntry value for a group not
offered by the client.
Servers offer exactly one KeyShareEntry value, which corresponds to Servers offer exactly one KeyShareEntry value, which corresponds to
the key exchange used for the negotiated cipher suite. the key exchange used for the negotiated cipher suite.
Clients offer an arbitrary number of KeyShareEntry values, each Clients offer an arbitrary number of KeyShareEntry values, each
representing a single set of key exchange parameters. For instance, representing a single set of key exchange parameters. For instance,
a client might offer shares for several elliptic curves or multiple a client might offer shares for several elliptic curves or multiple
integer DH groups. The key_exchange values for each KeyShareEntry integer DH groups. The key_exchange values for each KeyShareEntry
MUST by generated independently. Clients MUST NOT offer multiple MUST by generated independently. Clients MUST NOT offer multiple
KeyShareEntry values for the same parameters. Clients MAY omit this KeyShareEntry values for the same parameters. Clients and servers
extension from the ClientHello, and in response to this, servers MUST MUST NOT offer any KeyShareEntry values for groups not listed in the
send a HelloRetryRequest requesting use of one of the groups the client's "supported_groups" extension. Servers MUST NOT offer a
client offered support for in its "supported_groups" extension. If KeyShareEntry value for a group not offered by the client in its
no common supported group is available, the server MUST produce a corresponding KeyShare. Implementations receiving any KeyShare
fatal "handshake_failure" alert. (see Section 6.3.1.3) containing any of these prohibited values MUST abort the connection
with a fatal "illegal_parameter" alert.
If the server selects an (EC)DHE cipher suite and no mutually
supported group is available between the two endpoints' KeyShare
offers, yet there is a mutually supported group that can be found via
the "supported_groups" extension, then the server MUST reply with a
HelloRetryRequest. If there is no mutually supported group at all,
the server MUST NOT negotiate an (EC)DHE cipher suite.
[[TODO: Recommendation about what the client offers. Presumably [[TODO: Recommendation about what the client offers. Presumably
which integer DH groups and which curves.]] which integer DH groups and which curves.]]
6.3.2.3.1. Diffie-Hellman Parameters 6.3.2.3.1. Diffie-Hellman Parameters
Diffie-Hellman [DH] parameters for both clients and servers are Diffie-Hellman [DH] parameters for both clients and servers are
encoded in the opaque key_exchange field of a KeyShareEntry in a encoded in the opaque key_exchange field of a KeyShareEntry in a
KeyShare structure. The opaque value contains the Diffie-Hellman KeyShare structure. The opaque value contains the Diffie-Hellman
public value (dh_Y = g^X mod p), encoded as a big-endian integer. public value (dh_Y = g^X mod p), encoded as a big-endian integer.
skipping to change at page 52, line 17 skipping to change at page 54, line 24
6.3.2.3.2. ECDHE Parameters 6.3.2.3.2. ECDHE Parameters
ECDHE parameters for both clients and servers are encoded in the the ECDHE parameters for both clients and servers are encoded in the the
opaque key_exchange field of a KeyShareEntry in a KeyShare structure. opaque key_exchange field of a KeyShareEntry in a KeyShare structure.
The opaque value conveys the Elliptic Curve Diffie-Hellman public The opaque value conveys the Elliptic Curve Diffie-Hellman public
value (ecdh_Y) represented as a byte string ECPoint.point. value (ecdh_Y) represented as a byte string ECPoint.point.
opaque point <1..2^8-1>; opaque point <1..2^8-1>;
point point
This is the byte string representation of an elliptic curve point For secp256r1, secp384r1 and secp521r1, this is the byte string
following the conversion routine in Section 4.3.6 of ANSI X9.62 representation of an elliptic curve point following the conversion
[X962]. routine in Section 4.3.6 of ANSI X9.62 [X962]. For ecdh_x25519
and ecdh_x448, this is raw opaque octet-string representation of
point (in the format those functions use), 32 octets for
ecdh_x25519 and 56 octets for ecdh_x448.
Although X9.62 supports multiple point formats, any given curve MUST Although X9.62 supports multiple point formats, any given curve MUST
specify only a single point format. All curves currently specified specify only a single point format. All curves currently specified
in this document MUST only be used with the uncompressed point in this document MUST only be used with the uncompressed point format
format. (the format for all ECDH functions is considered uncompressed).
Note: Versions of TLS prior to 1.3 permitted point negotiation; TLS Note: Versions of TLS prior to 1.3 permitted point negotiation; TLS
1.3 removes this feature in favor of a single point format for each 1.3 removes this feature in favor of a single point format for each
curve. curve.
[[OPEN ISSUE: We will need to adjust the compressed/uncompressed
point issue if we have new curves that don't need point compression.
This depends on the CFRG's recommendations. The expectation is that
future curves will come with defined point formats and that existing
curves conform to X9.62.]]
6.3.2.4. Pre-Shared Key Extension 6.3.2.4. Pre-Shared Key Extension
The "pre_shared_key" extension is used to indicate the identity of The "pre_shared_key" extension is used to indicate the identity of
the pre-shared key to be used with a given handshake in association the pre-shared key to be used with a given handshake in association
with a PSK or (EC)DHE-PSK cipher suite (see [RFC4279] for with a PSK or (EC)DHE-PSK cipher suite (see [RFC4279] for
background). background).
Clients which offer one or more PSK cipher suites MUST send at least Clients which offer one or more PSK cipher suites MUST send at least
one supported psk_identity value and servers MUST NOT negotiate any one supported psk_identity value and servers MUST NOT negotiate any
of these cipher suites unless a supported value was provided. If of these cipher suites unless a supported value was provided. If
skipping to change at page 53, line 28 skipping to change at page 55, line 30
An opaque label for the pre-shared key. An opaque label for the pre-shared key.
If no suitable identity is provided, the server MUST NOT negotiate a If no suitable identity is provided, the server MUST NOT negotiate a
PSK cipher suite and MAY respond with an "unknown_psk_identity" alert PSK cipher suite and MAY respond with an "unknown_psk_identity" alert
message. Sending this alert is OPTIONAL; servers MAY instead choose message. Sending this alert is OPTIONAL; servers MAY instead choose
to send a "decrypt_error" alert to merely indicate an invalid PSK to send a "decrypt_error" alert to merely indicate an invalid PSK
identity or instead negotiate use of a non-PSK cipher suite, if identity or instead negotiate use of a non-PSK cipher suite, if
available. available.
If the server selects a PSK cipher suite, it MUST send a If the server selects a PSK cipher suite, it MUST send a
PreSharedKeyExtension with the identity that it selected. The client "pre_shared_key" extension with the identity that it selected. The
MUST verify that the server has selected one of the identities that client MUST verify that the server has selected one of the identities
the client supplied. If any other identity is returned, the client that the client supplied. If any other identity is returned, the
MUST generate a fatal "unknown_psk_identity" alert and close the client MUST generate a fatal "unknown_psk_identity" alert and close
connection. the connection.
6.3.2.5. Early Data Indication 6.3.2.5. Early Data Indication
In cases where TLS clients have previously interacted with the server In cases where TLS clients have previously interacted with the server
and the server has supplied a ServerConfiguration Section 6.3.6, the and the server has supplied a ServerConfiguration (Section 6.3.3.3),
client can send application data and its Certificate/ the client can send application data and its Certificate/
CertificateVerify messages (if client authentication is required). CertificateVerify messages (if client authentication is required).
If the client opts to do so, it MUST supply an Early Data Indication If the client opts to do so, it MUST supply an "early_data"
extension. extension.
The "extension_data" field of this extension contains an The "extension_data" field of this extension contains an
"EarlyDataIndication" value: "EarlyDataIndication" value:
enum { client_authentication(1), early_data(2),
client_authentication_and_data(3), (255) } EarlyDataType;
struct { struct {
select (Role) { select (Role) {
case client: case client:
opaque configuration_id<1..2^16-1>; opaque configuration_id<1..2^16-1>;
CipherSuite cipher_suite; CipherSuite cipher_suite;
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
opaque context<0..255>; opaque context<0..255>;
EarlyDataType type;
case server: case server:
struct {}; struct {};
} }
} EarlyDataIndication; } EarlyDataIndication;
configuration_id configuration_id
The label for the configuration in question. The label for the configuration in question.
cipher_suite cipher_suite
skipping to change at page 54, line 37 skipping to change at page 56, line 33
data. data.
extensions extensions
The extensions required to define the cryptographic configuration The extensions required to define the cryptographic configuration
for the clients early data (see below for details). for the clients early data (see below for details).
context context
An optional context value that can be used for anti-replay (see An optional context value that can be used for anti-replay (see
below). below).
type
The type of early data that is being sent. "client_authentication"
means that only handshake data is being sent. "early_data" means
that only data is being sent. "client_authentication_and_data"
means that both are being sent.
The client specifies the cryptographic configuration for the 0-RTT The client specifies the cryptographic configuration for the 0-RTT
data using the "configuration", "cipher_suite", and "extensions" data using the "configuration_id", "cipher_suite", and "extensions"
values. For configurations received in-band (in a previous TLS values. For configurations received in-band (in a previous TLS
connection) the client MUST: connection) the client MUST:
- Send the same cryptographic determining parameters - Send the same cryptographic determining parameters
(Section Section 6.3.2.5.1) with the previous connection. If a (Section Section 6.3.2.5.1) with the previous connection. If a
0-RTT handshake is being used with a PSK that was negotiated via a 0-RTT handshake is being used with a PSK that was negotiated via a
non-PSK handshake, then the client MUST use the same symmetric non-PSK handshake, then the client MUST use the same symmetric
cipher parameters as were negotiated on that handshake but with a cipher parameters as were negotiated on that handshake but with a
PSK cipher suite. PSK cipher suite.
- Indicate the same parameters as the server indicated in that - Indicate the same parameters as the server indicated in that
connection. connection.
If TLS client authentication is being used, then either 0-RTT messages sent in the first flight have the same content types
"early_handshake" or "early_handshake_and_data" MUST be indicated in as their corresponding messages sent in other flights (handshake,
order to send the client authentication data on the first flight. In application_data, and alert respectively) but are protected under
either case, the client Certificate and CertificateVerify (assuming different keys. After all the 0-RTT application data messages (if
that the Certificate is non-empty) MUST be sent on the first flight. any) have been sent, a "end_of_early_data" alert of type "warning" is
A server which receives an initial flight with only "early_data" and sent to indicate the end of the flight. Clients which do 0-RTT MUST
which expects certificate-based client authentication MUST NOT accept always send "end_of_early_data" even if the ServerConfiguration
early data. indicates that no application data is allowed (EarlyDataType of
"client_authentication"), though in that case it MUST NOT send any
In order to allow servers to readily distinguish between messages non-empty data records (i.e., those which consist of anything other
sent in the first flight and in the second flight (in cases where the than padding).
server does not accept the EarlyDataIndication extension), the client
MUST send the handshake messages as content type "early_handshake".
A server which does not accept the extension proceeds by skipping all
records after the ClientHello and until the next client message of
type "handshake". [[OPEN ISSUE: This needs replacement when we add
encrypted content types.]]
A server which receives an EarlyDataIndication extension can behave A server which receives an "early_data" extension can behave in one
in one of two ways: of two ways:
- Ignore the extension and return no response. This indicates that - Ignore the extension and return no response. This indicates that
the server has ignored any early data and an ordinary 1-RTT the server has ignored any early data and an ordinary 1-RTT
handshake is required. handshake is required.
- Return an empty extension, indicating that it intends to process - Return an empty extension, indicating that it intends to process
the early data. It is not possible for the server to accept only the early data. It is not possible for the server to accept only
a subset of the early data messages. a subset of the early data messages.
Prior to accepting the EarlyDataIndication extension, the server MUST Prior to accepting the "early_data" extension, the server MUST
perform the following checks: perform the following checks:
- The configuration_id matches a known server configuration. - The configuration_id matches a known server configuration.
- The client's cryptographic determining parameters match the - The client's cryptographic determining parameters match the
parameters that the server has negotiated based on the rest of the parameters that the server has negotiated based on the rest of the
ClientHello. ClientHello. If (EC)DHE is selected, this includes verifying that
(1) the ClientHello contains a key from the same group that is
indicated by the server configuration and (2) that the server has
negotiated that group and will therefore include a share from that
group in its own "key_share" extension.
If any of these checks fail, the server MUST NOT respond with the If any of these checks fail, the server MUST NOT respond with the
extension and must discard all the remaining first flight data (thus extension and must discard all the remaining first flight data (thus
falling back to 1-RTT). falling back to 1-RTT). If the client attempts a 0-RTT handshake but
the server rejects it, it will generally not have the 0-RTT record
protection keys and will instead trial decrypt each record with the
1-RTT handshake keys until it finds one that decrypts properly, and
then pick up the handshake from that point.
If the server choosed to accept the "early_data" extension, then it
MUST comply with the same error handling requirements specified for
all records when processing early data records. Specifically,
decryption failure of any 0-RTT record following an accepted
"early_data" extension MUST produce a fatal "bad_record_mac" alert as
per Section 5.2.2.
[[TODO: How does the client behave if the indication is rejected.]] [[TODO: How does the client behave if the indication is rejected.]]
[[OPEN ISSUE: This just specifies the signaling for 0-RTT but not the [[OPEN ISSUE: This just specifies the signaling for 0-RTT but not the
the 0-RTT cryptographic transforms, including: the 0-RTT cryptographic transforms, including:
- What is in the handshake hash (including potentially some - What is in the handshake hash (including potentially some
speculative data from the server). speculative data from the server).
- What is signed in the client's CertificateVerify. - What is signed in the client's CertificateVerify.
skipping to change at page 56, line 27 skipping to change at page 58, line 25
What's here now needs a lot of cleanup before it is clear and What's here now needs a lot of cleanup before it is clear and
correct.]] correct.]]
6.3.2.5.1. Cryptographic Determining Parameters 6.3.2.5.1. Cryptographic Determining Parameters
In order to allow the server to decrypt 0-RTT data, the client needs In order to allow the server to decrypt 0-RTT data, the client needs
to provide enough information to allow the server to decrypt the to provide enough information to allow the server to decrypt the
traffic without negotiation. This is accomplished by having the traffic without negotiation. This is accomplished by having the
client indicate the "cryptographic determining parameters" in its client indicate the "cryptographic determining parameters" in its
ClientHello, which are necessary to decrypt the client's packets. ClientHello, which are necessary to decrypt the client's packets
This includes the following values: (i.e., those present in the ServerHello). This includes the
following values:
- The cipher suite identifier. - The cipher suite identifier.
- If PSK is being used, the server's version of the PreSharedKey - If (EC)DHE is being used, the server's version of "key_share".
extension (indicating the PSK the client is using).
[[TODO: Are there other extensions we need? I've gone over the list - If PSK is being used, the server's version of the "pre_shared_key"
and I don't see any, but...]] [[TODO: This should be the same list as (indicating the PSK the client is using).
what you need for !EncryptedExtensions. Consolidate this list.]]
6.3.2.5.2. Replay Properties 6.3.2.5.2. Replay Properties
As noted in Section 6.2.2, TLS does not provide any inter-connection As noted in Section 6.2.2, TLS does not provide any inter-connection
mechanism for replay protection for data sent by the client in the mechanism for replay protection for data sent by the client in the
first flight. As a special case, implementations where the server first flight. As a special case, implementations where the server
configuration, is delivered out of band (as has been proposed for configuration, is delivered out of band (as has been proposed for
DTLS-SRTP [RFC5763]), MAY use a unique server configuration DTLS-SRTP [RFC5763]), MAY use a unique server configuration
identifier for each connection, thus preventing replay. identifier for each connection, thus preventing replay.
Implementations are responsible for ensuring uniqueness of the Implementations are responsible for ensuring uniqueness of the
identifier in this case. identifier in this case.
6.3.3. Encrypted Extensions 6.3.3. Server Parameters
6.3.3.1. Encrypted Extensions
When this message will be sent: When this message will be sent:
If this message is sent, it MUST be sent immediately after the The EncryptedExtensions message MUST be sent immediately after the
ServerHello message. This is the first message that is encrypted ServerHello message. This is the first message that is encrypted
under keys derived from ES. under keys derived from ES.
Meaning of this message: Meaning of this message:
The EncryptedExtensions message simply contains any extensions The EncryptedExtensions message simply contains any extensions
which should be protected, i.e., any which are not needed to which should be protected, i.e., any which are not needed to
establish the cryptographic context. The same extension types establish the cryptographic context. The same extension types
MUST NOT appear in both the ServerHello and EncryptedExtensions. MUST NOT appear in both the ServerHello and EncryptedExtensions.
If the same extension appears in both locations, the client MUST If the same extension appears in both locations, the client MUST
rely only on the value in the EncryptedExtensions block. [[OPEN rely only on the value in the EncryptedExtensions block. All
ISSUE: Should we just produce a canonical list of what goes where server-sent extensions other than those explicitly listed in
and have it be an error to have it in the wrong place? That seems Section 6.3.1.2 or designated in the IANA registry MUST only
simpler. Perhaps have a whitelist of which extensions can be appear in EncryptedExtensions. Extensions which are designated to
unencrypted and everything else MUST be encrypted.]] appear in ServerHello MUST NOT appear in EncryptedExtensions.
Clients MUST check EncryptedExtensions for the presence of any
forbidden extensions and if any are found MUST terminate the
handshake with a "illegal_parameter" alert.
Structure of this message: Structure of this message:
struct { struct {
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
} EncryptedExtensions; } EncryptedExtensions;
extensions extensions
A list of extensions. A list of extensions.
6.3.4. Server Certificate 6.3.3.2. Certificate Request
When this message will be sent:
The server MUST send a Certificate message whenever the agreed-
upon key exchange method uses certificates for authentication
(this includes all key exchange methods defined in this document
except PSK). This message will always immediately follow the
EncryptedExtensions message.
Meaning of this message:
This message conveys the server's certificate chain to the client.
The certificate MUST be appropriate for the negotiated cipher
suite's key exchange algorithm and any negotiated extensions.
Structure of this message:
opaque ASN1Cert<1..2^24-1>;
struct {
ASN1Cert certificate_list<0..2^24-1>;
} Certificate;
certificate_list
This is a sequence (chain) of certificates. The sender's
certificate MUST come first in the list. Each following
certificate SHOULD directly certify one preceding it. Because
certificate validation requires that trust anchors be distributed
independently, a certificate that specifies a trust anchor MAY be
omitted from the chain, provided that supported peers are known to
possess any omitted certificates.
Note: Prior to TLS 1.3, "certificate_list" ordering required each
certificate to certify the one immediately preceding it, however some
implementations allowed some flexibility. Servers sometimes send
both a current and deprecated intermediate for transitional purposes,
and others are simply configured incorrectly, but these cases can
nonetheless be validated properly. For maximum compatibility, all
implementations SHOULD be prepared to handle potentially extraneous
certificates and arbitrary orderings from any TLS version, with the
exception of the end-entity certificate which MUST be first.
The same message type and structure will be used for the client's
response to a certificate request message. Note that a client MAY
send no certificates if it does not have an appropriate certificate
to send in response to the server's authentication request.
Note: PKCS #7 [PKCS7] is not used as the format for the certificate
vector because PKCS #6 [PKCS6] extended certificates are not used.
Also, PKCS #7 defines a SET rather than a SEQUENCE, making the task
of parsing the list more difficult.
The following rules apply to the certificates sent by the server:
- The certificate type MUST be X.509v3 [RFC5280], unless explicitly
negotiated otherwise (e.g., [RFC5081]).
- The server's end-entity certificate's public key (and associated
restrictions) MUST be compatible with the selected key exchange
algorithm.
Key Exchange Alg. Certificate Key Type
DHE_RSA RSA public key; the certificate MUST allow the
ECDHE_RSA key to be used for signing (i.e., the
digitalSignature bit MUST be set if the key
usage extension is present) with the signature
scheme and hash algorithm that will be employed
in the server's KeyShare extension.
Note: ECDHE_RSA is defined in [RFC4492].
ECDHE_ECDSA ECDSA-capable public key; the certificate MUST
allow the key to be used for signing with the
hash algorithm that will be employed in the
server's KeyShare extension. The public key
MUST use a curve and point format supported by
the client, as described in [RFC4492].
- The "server_name" and "trusted_ca_keys" extensions [RFC6066] are
used to guide certificate selection. As servers MAY require the
presence of the server_name extension, clients SHOULD send this
extension.
All certificates provided by the server MUST be signed by a hash/
signature algorithm pair that appears in the "signature_algorithms"
extension provided by the client, if they are able to provide such a
chain (see Section 6.3.2.1). If the server cannot produce a
certificate chain that is signed only via the indicated supported
pairs, then it SHOULD continue the handshake by sending the client a
certificate chain of its choice that may include algorithms that are
not known to be supported by the client. This fallback chain MAY use
the deprecated SHA-1 hash algorithm. If the client cannot construct
an acceptable chain using the provided certificates and decides to
abort the handshake, then it MUST send an "unsupported_certificate"
alert message and close the connection.
Any endpoint receiving any certificate signed using any signature
algorithm using an MD5 hash MUST send a "bad_certificate" alert
message and close the connection.
As SHA-1 and SHA-224 are deprecated, support for them is NOT
RECOMMENDED. Endpoints that reject chains due to use of a deprecated
hash MUST send a fatal "bad_certificate" alert message before closing
the connection. All servers are RECOMMENDED to transition to SHA-256
or better as soon as possible to maintain interoperability with
implementations currently in the process of phasing out SHA-1
support.
Note that a certificate containing a key for one signature algorithm
MAY be signed using a different signature algorithm (for instance, an
RSA key signed with a ECDSA key).
If the server has multiple certificates, it chooses one of them based
on the above-mentioned criteria (in addition to other criteria, such
as transport layer endpoint, local configuration and preferences).
If the server has a single certificate, it SHOULD attempt to validate
that it meets these criteria.
As cipher suites that specify new key exchange methods are specified
for the TLS protocol, they will imply the certificate format and the
required encoded keying information.
6.3.5. Certificate Request
When this message will be sent: When this message will be sent:
A non-anonymous server can optionally request a certificate from A non-anonymous server can optionally request a certificate from
the client, if appropriate for the selected cipher suite. This the client, if appropriate for the selected cipher suite. This
message, if sent, will immediately follow the server's Certificate message, if sent, will follow EncryptedExtensions.
message.
Structure of this message: Structure of this message:
opaque DistinguishedName<1..2^16-1>; opaque DistinguishedName<1..2^16-1>;
struct { struct {
opaque certificate_extension_oid<1..2^8-1>; opaque certificate_extension_oid<1..2^8-1>;
opaque certificate_extension_values<0..2^16-1>; opaque certificate_extension_values<0..2^16-1>;
} CertificateExtension; } CertificateExtension;
struct { struct {
opaque certificate_request_context<0..2^8-1>;
SignatureAndHashAlgorithm SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>; supported_signature_algorithms<2..2^16-2>;
DistinguishedName certificate_authorities<0..2^16-1>; DistinguishedName certificate_authorities<0..2^16-1>;
CertificateExtension certificate_extensions<0..2^16-1>; CertificateExtension certificate_extensions<0..2^16-1>;
} CertificateRequest; } CertificateRequest;
certificate_request_context
An opaque string which identifies the certificate request and
which will be echoed in the client's Certificate message. The
certificate_request_context MUST be unique within the scope of
this connection (thus preventing replay of client
CertificateVerify messages).
supported_signature_algorithms supported_signature_algorithms
A list of the hash/signature algorithm pairs that the server is A list of the hash/signature algorithm pairs that the server is
able to verify, listed in descending order of preference. Any able to verify, listed in descending order of preference. Any
certificates provided by the client MUST be signed using a hash/ certificates provided by the client MUST be signed using a hash/
signature algorithm pair found in supported_signature_algorithms. signature algorithm pair found in supported_signature_algorithms.
certificate_authorities certificate_authorities
A list of the distinguished names [X501] of acceptable A list of the distinguished names [X501] of acceptable
certificate_authorities, represented in DER-encoded [X690] format. certificate_authorities, represented in DER-encoded [X690] format.
These distinguished names may specify a desired distinguished name These distinguished names may specify a desired distinguished name
for a root CA or for a subordinate CA; thus, this message can be for a root CA or for a subordinate CA; thus, this message can be
used to describe known roots as well as a desired authorization used to describe known roots as well as a desired authorization
space. If the certificate_authorities list is empty, then the space. If the certificate_authorities list is empty, then the
client MAY send any certificate that meets the rest of the client MAY send any certificate that meets the rest of the
selection criteria in the CertificateRequest, unless there is some selection criteria in the CertificateRequest, unless there is some
external arrangement to the contrary. external arrangement to the contrary.
certificate_extensions certificate_extensions
A list of certificate extension OIDs [RFC5280] with their allowed A list of certificate extension OIDs [RFC5280] with their allowed
skipping to change at page 61, line 15 skipping to change at page 60, line 46
These distinguished names may specify a desired distinguished name These distinguished names may specify a desired distinguished name
for a root CA or for a subordinate CA; thus, this message can be for a root CA or for a subordinate CA; thus, this message can be
used to describe known roots as well as a desired authorization used to describe known roots as well as a desired authorization
space. If the certificate_authorities list is empty, then the space. If the certificate_authorities list is empty, then the
client MAY send any certificate that meets the rest of the client MAY send any certificate that meets the rest of the
selection criteria in the CertificateRequest, unless there is some selection criteria in the CertificateRequest, unless there is some
external arrangement to the contrary. external arrangement to the contrary.
certificate_extensions certificate_extensions
A list of certificate extension OIDs [RFC5280] with their allowed A list of certificate extension OIDs [RFC5280] with their allowed
values, represented in DER-encoded format. Some certificate values, represented in DER-encoded [X690] format. Some
extension OIDs allow multiple values (e.g. Extended Key Usage). certificate extension OIDs allow multiple values (e.g. Extended
If the server has included a non-empty certificate_extensions Key Usage). If the server has included a non-empty
list, the client certificate MUST contain all of the specified certificate_extensions list, the client certificate MUST contain
extension OIDs that the client recognizes. For each extension OID all of the specified extension OIDs that the client recognizes.
recognized by the client, all of the specified values MUST be For each extension OID recognized by the client, all of the
present in the client certificate (but the certificate MAY have specified values MUST be present in the client certificate (but
other values as well). However, the client MUST ignore and skip the certificate MAY have other values as well). However, the
any unrecognized certificate extension OIDs. If the client has client MUST ignore and skip any unrecognized certificate extension
ignored some of the required certificate extension OIDs, and OIDs. If the client has ignored some of the required certificate
supplied a certificate that does not satisfy the request, the extension OIDs, and supplied a certificate that does not satisfy
server MAY at its discretion either continue the session without the request, the server MAY at its discretion either continue the
client authentication, or terminate the session with a fatal session without client authentication, or terminate the session
unsupported_certificate alert. PKIX RFCs define a variety of with a fatal unsupported_certificate alert. PKIX RFCs define a
certificate extension OIDs and their corresponding value types. variety of certificate extension OIDs and their corresponding
Depending on the type, matching certificate extension values are value types. Depending on the type, matching certificate
not necessarily bitwise-equal. It is expected that TLS extension values are not necessarily bitwise-equal. It is
implementations will rely on their PKI libraries to perform expected that TLS implementations will rely on their PKI libraries
certificate selection using certificate extension OIDs. This to perform certificate selection using certificate extension OIDs.
document defines matching rules for two standard certificate This document defines matching rules for two standard certificate
extensions defined in [RFC5280]: extensions defined in [RFC5280]:
o The Key Usage extension in a certificate matches the request o The Key Usage extension in a certificate matches the request
when all key usage bits asserted in the request are also when all key usage bits asserted in the request are also
asserted in the Key Usage certificate extension. asserted in the Key Usage certificate extension.
o The Extended Key Usage extension in a certificate matches the o The Extended Key Usage extension in a certificate matches the
request when all key purpose OIDs present in the request are request when all key purpose OIDs present in the request are
also found in the Extended Key Usage certificate extension. also found in the Extended Key Usage certificate extension.
The special anyExtendedKeyUsage OID MUST NOT be used in the The special anyExtendedKeyUsage OID MUST NOT be used in the
request. request.
Separate specifications may define matching rules for other Separate specifications may define matching rules for other
certificate extensions. certificate extensions.
Note: It is a fatal "handshake_failure" alert for an anonymous server Note: It is a fatal "handshake_failure" alert for an anonymous server
to request client authentication. to request client authentication.
6.3.6. Server Configuration 6.3.3.3. Server Configuration
When this message will be sent: When this message will be sent:
This message is used to provide a server configuration which the This message is used to provide a server configuration which the
client can use in future to skip handshake negotiation and client can use in the future to skip handshake negotiation and
(optionally) to allow 0-RTT handshakes. The ServerConfiguration (optionally) to allow 0-RTT handshakes. The ServerConfiguration
message is sent as the last message before the CertificateVerify. message is sent as the last message before the CertificateVerify.
Structure of this Message: Structure of this Message:
enum { (65535) } ConfigurationExtensionType; enum { (65535) } ConfigurationExtensionType;
struct { enum { client_authentication(1), early_data(2),
ConfigurationExtensionType extension_type; client_authentication_and_data(3), (255) } EarlyDataType;
opaque extension_data<0..2^16-1>;
} ConfigurationExtension;
struct { struct {
opaque configuration_id<1..2^16-1>; ConfigurationExtensionType extension_type;
uint32 expiration_date; opaque extension_data<0..2^16-1>;
NamedGroup group; } ConfigurationExtension;
opaque server_key<1..2^16-1>;
EarlyDataType early_data_type; struct {
ConfigurationExtension extensions<0..2^16-1>; opaque configuration_id<1..2^16-1>;
} ServerConfiguration; uint32 expiration_date;
KeyShareEntry static_key_share;
EarlyDataType early_data_type;
ConfigurationExtension extensions<0..2^16-1>;
} ServerConfiguration;
configuration_id configuration_id
The configuration identifier to be used in 0-RTT mode. The configuration identifier to be used in 0-RTT mode.
group
The group for the long-term DH key that is being established for
this configuration.
expiration_date expiration_date
The last time when this configuration is expected to be valid (in The last time when this configuration is expected to be valid (in
seconds since the Unix epoch). Servers MUST NOT use any value seconds since the Unix epoch). Servers MUST NOT use any value
more than 604800 seconds (7 days) in the future. Clients MUST NOT more than 604800 seconds (7 days) in the future. Clients MUST NOT
cache configurations for longer than 7 days, regardless of the cache configurations for longer than 7 days, regardless of the
expiration_date. [[OPEN ISSUE: Is this the right value? The idea expiration_date. [[OPEN ISSUE: Is this the right value? The idea
is just to minimize exposure.]] is just to minimize exposure.]]
server_key static_key_share
The long-term DH key that is being established for this The long-term DH key that is being established for this
configuration. configuration.
early_data_type early_data_type
The type of 0-RTT handshake that this configuration is to be used The type of 0-RTT handshake that this configuration is to be used
for (see Section 6.3.2.5). If "client_authentication" or for (see Section 6.3.2.5). If "client_authentication" or
"client_authentication_and_data", then the client should select "client_authentication_and_data", then the client MUST select the
the certificate for future handshakes based on the certificate for future handshakes based on the CertificateRequest
CertificateRequest parameters supplied in this handshake. The parameters supplied in this handshake. The server MUST NOT send
server MUST NOT send either of these two options unless it also either of these two options unless it also requested a certificate
requested a certificate on this handshake. [[OPEN ISSUE: Should on this handshake. [[OPEN ISSUE: Should we relax this?]]
we relax this?]]
extensions extensions
This field is a placeholder for future extensions to the This field is a placeholder for future extensions to the
ServerConfiguration format. ServerConfiguration format.
The semantics of this message are to establish a shared state between The semantics of this message are to establish a shared state between
the client and server for use with the "known_configuration" the client and server for use with the "known_configuration"
extension with the key specified in key and with the handshake extension with the key specified in key and with the handshake
parameters negotiated by this handshake. parameters negotiated by this handshake.
When the ServerConfiguration message is sent, the server MUST also When the ServerConfiguration message is sent, the server MUST also
send a Certificate message and a CertificateVerify message, even if send a Certificate message and a CertificateVerify message, even if
the "known_configuration" extension was used for this handshake, thus the "known_configuration" extension was used for this handshake, thus
requiring a signature over the configuration before it can be used by requiring a signature over the configuration before it can be used by
the client. Clients MUST NOT rely on the ServerConfiguration message the client. Clients MUST NOT rely on the ServerConfiguration message
until successfully receiving and processing the server's Certificate, until successfully receiving and processing the server's Certificate,
CertificateVerify, and Finished. If there is a failure in processing CertificateVerify, and Finished. If there is a failure in processing
those messages, the client MUST discard the ServerConfiguration. those messages, the client MUST discard the ServerConfiguration.
6.3.7. Server Certificate Verify 6.3.4. Authentication Messages
When this message will be sent: As discussed in Section 6.2, TLS uses a common set of messages for
authentication, key confirmation, and handshake integrity:
Certificate, CertificateVerify, and Finished. These messages are
always sent as the last messages in their handshake flight. The
Certificate and CertificateVerify messages are only sent under
certain circumstances, as defined below. The Finished message is
always sent as part of the Authentication block.
This message is used to provide explicit proof that the server The computations for the Authentication messages all uniformly take
possesses the private key corresponding to its certificate and the following inputs:
also provides integrity for the handshake up to this point. This
message is sent when the server is authenticated via a
certificate. When sent, it MUST be the last server handshake
message prior to the Finished.
Structure of this message: - The certificate and signing key to be used.
struct { - A Handshake Context based on the handshake hash (see
digitally-signed struct { Section 7.3.1).
opaque handshake_hash[hash_length];
};
} CertificateVerify;
Where handshake_hash is as described in Section 7.2.1 and includes - A base key to be used to compute a MAC key.
the messages sent or received, starting at ClientHello and up to,
but not including, this message, including the type and length
fields of the handshake messages. This is a digest of the
concatenation of all the Handshake structures (as defined in
Section 6.3) exchanged thus far. The digest MUST be the Hash used
as the basis for HKDF.
The context string for the signature is "TLS 1.3, server Based on these inputs, the messages then contain:
CertificateVerify". A hash of the handshake messages is signed
rather than the messages themselves because the digitally-signed
format requires padding and context bytes at the beginning of the
input. Thus, by signing a digest of the messages, an
implementation need only maintain one running hash per hash type
for CertificateVerify, Finished and other messages.
The signature algorithm and hash algorithm MUST be a pair offered Certificate
in the client's "signature_algorithms" extension unless no valid The certificate to be used for authentication and any supporting
certificate chain can be produced without unsupported algorithms certificates in the chain.
(see Section 6.3.2.1). Note that there is a possibility for
inconsistencies here. For instance, the client might offer
ECDHE_ECDSA key exchange but omit any ECDSA pairs from its
"signature_algorithms" extension. In order to negotiate
correctly, the server MUST check any candidate cipher suites
against the "signature_algorithms" extension before selecting
them. This is somewhat inelegant but is a compromise designed to
minimize changes to the original cipher suite design.
In addition, the hash and signature algorithms MUST be compatible CertificateVerify
with the key in the server's end-entity certificate. RSA keys MAY A signature over the hash of Handshake Context + Certificate.
be used with any permitted hash algorithm, subject to restrictions
in the certificate, if any. RSA signatures MUST be based on
RSASSA-PSS, regardless of whether RSASSA-PKCS-v1_5 appears in
"signature_algorithms". SHA-1 MUST NOT be used in any signatures
in CertificateVerify, regardless of whether SHA-1 appears in
"signature_algorithms".
6.3.8. Server Finished Finished
A MAC over the hash of Handshake Context + Certificate +
CertificateVerify using a MAC key derived from the base key.
Because the CertificateVerify signs the Handshake Context +
Certificate and the Finished MACs the Handshake Context + Certificate
+ CertificateVerify, this is mostly equivalent to keeping a running
hash of the handshake messages (exactly so in the pure 1-RTT cases).
Note, however, that subsequent post-handshake authentications do not
include each other, just the messages through the end of the main
handshake.
The following table defines the Handshake Context and MAC Key for
each scenario:
+----------------+-----------------------------------------+--------+
| Mode | Handshake Context | Base |
| | | Key |
+----------------+-----------------------------------------+--------+
| 0-RTT | ClientHello + ServerConfiguration + | xSS |
| | Server Certificate + CertificateRequest | |
| | (where ServerConfiguration, etc. are | |
| | from the previous handshake) | |
| | | |
| 1-RTT (Server) | ClientHello ... ServerConfiguration | master |
| | | secret |
| | | |
| 1-RTT (Client) | ClientHello ... ServerFinished | master |
| | | secret |
| | | |
| Post-Handshake | ClientHello ... ClientFinished + | master |
| | CertificateRequest | secret |
+----------------+-----------------------------------------+--------+
Note 1: The ServerConfiguration, CertificateRequest, and Server
Certificate in the 0-RTT case are the messages from the handshake
where the ServerConfiguration was established.
Note 2: The Handshake Context for the last three rows does not
include any 0-RTT handshake messages, regardless of whether 0-RTT
is used.
6.3.4.1. Certificate
When this message will be sent: When this message will be sent:
The Server's Finished message is the final message sent by the The server MUST send a Certificate message whenever the agreed-
server and is essential for providing authentication of the server upon key exchange method uses certificates for authentication
side of the handshake and computed keys. (this includes all key exchange methods defined in this document
except PSK).
The client MUST send a Certificate message whenever the server has
requested client authentication via a CertificateRequest message
(Section 6.3.3.2) or when the EarlyDataType provided with the
server configuration indicates a need for client authentication.
This message is only sent if the server requests a certificate via
one of these mechanisms. If no suitable certificate is available,
the client MUST send a Certificate message containing no
certificates (i.e., with the "certificate_list" field having
length 0).
Meaning of this message: Meaning of this message:
Recipients of Finished messages MUST verify that the contents are This message conveys the endpoint's certificate chain to the peer.
correct. Once a side has sent its Finished message and received
and validated the Finished message from its peer, it may begin to The certificate MUST be appropriate for the negotiated cipher
send and receive application data over the connection. This data suite's key exchange algorithm and any negotiated extensions.
will be protected under keys derived from the ephemeral secret
(see Section 7).
Structure of this message: Structure of this message:
opaque ASN1Cert<1..2^24-1>;
struct { struct {
opaque verify_data[verify_data_length]; opaque certificate_request_context<0..255>;
} Finished; ASN1Cert certificate_list<0..2^24-1>;
} Certificate;
The verify_data value is computed as follows: certificate_request_context:
If this message is in response to a CertificateRequest, the value
if certificate_request_context in that message. Otherwise, in the
case of server authentication or client authentication in 0-RTT,
this field SHALL be zero length.
verify_data certificate_list
HMAC(finished_secret, finished_label + '\0' + handshake_hash) This is a sequence (chain) of certificates. The sender's
where HMAC [RFC2104] uses the Hash algorithm for the handshake. certificate MUST come first in the list. Each following
See Section 7.2.1 for the definition of handshake_hash. certificate SHOULD directly certify one preceding it. Because
certificate validation requires that trust anchors be distributed
independently, a certificate that specifies a trust anchor MAY be
omitted from the chain, provided that supported peers are known to
possess any omitted certificates.
finished_label Note: Prior to TLS 1.3, "certificate_list" ordering required each
For Finished messages sent by the client, the string "client certificate to certify the one immediately preceding it, however some
finished". For Finished messages sent by the server, the string implementations allowed some flexibility. Servers sometimes send
"server finished". both a current and deprecated intermediate for transitional purposes,
and others are simply configured incorrectly, but these cases can
nonetheless be validated properly. For maximum compatibility, all
implementations SHOULD be prepared to handle potentially extraneous
certificates and arbitrary orderings from any TLS version, with the
exception of the end-entity certificate which MUST be first.
In previous versions of TLS, the verify_data was always 12 octets The server's certificate list MUST always be non-empty. A client
long. In the current version of TLS, it is the size of the HMAC will MAY send an empty certificate list if it does not have an
output for the Hash used for the handshake. appropriate certificate to send in response to the server's
authentication request.
Note: Alerts and any other record types are not handshake messages 6.3.4.1.1. Server Certificate Selection
and are not included in the hash computations. Also, HelloRequest
messages and the Finished message are omitted from handshake hashes.
6.3.9. Client Certificate The following rules apply to the certificates sent by the server:
When this message will be sent: - The certificate type MUST be X.509v3 [RFC5280], unless explicitly
negotiated otherwise (e.g., [RFC5081]).
This message is the first handshake message the client can send - The server's end-entity certificate's public key (and associated
after receiving the server's Finished. This message is only sent restrictions) MUST be compatible with the selected key exchange
if the server requests a certificate. If no suitable certificate algorithm.
is available, the client MUST send a certificate message
containing no certificates. That is, the certificate_list
structure has a length of zero. If the client does not send any
certificates, the server MAY at its discretion either continue the
handshake without client authentication, or respond with a fatal
"handshake_failure" alert. Also, if some aspect of the
certificate chain was unacceptable (e.g., it was not signed by a
known, trusted CA), the server MAY at its discretion either
continue the handshake (considering the client unauthenticated) or
send a fatal alert.
Client certificates are sent using the Certificate structure +----------------------+---------------------------+
defined in Section 6.3.4. | Key Exchange Alg. | Certificate Key Type |
+----------------------+---------------------------+
| DHE_RSA or ECDHE_RSA | RSA public key |
| | |
| ECDHE_ECDSA | ECDSA or EdDSA public key |
+----------------------+---------------------------+
Meaning of this message: - The certificate MUST allow the key to be used for signing (i.e.,
the digitalSignature bit MUST be set if the Key Usage extension is
present) with a signature scheme and hash algorithm pair indicated
in the client's "signature_algorithms" extension.
This message conveys the client's certificate chain to the server; - An ECDSA or EdDSA public key MUST use a curve and point format
the server will use it when verifying the CertificateVerify supported by the client, as described in [RFC4492].
message (when the client authentication is based on signing). The
certificate MUST be appropriate for the negotiated cipher suite's - The "server_name" and "trusted_ca_keys" extensions [RFC6066] are
key exchange algorithm, and any negotiated extensions. used to guide certificate selection. As servers MAY require the
presence of the "server_name" extension, clients SHOULD send this
extension.
All certificates provided by the server MUST be signed by a hash/
signature algorithm pair that appears in the "signature_algorithms"
extension provided by the client, if they are able to provide such a
chain (see Section 6.3.2.1). Certificates that are self-signed or
certificates that are expected to be trust anchors are not validated
as part of the chain and therefore MAY be signed with any algorithm.
If the server cannot produce a certificate chain that is signed only
via the indicated supported pairs, then it SHOULD continue the
handshake by sending the client a certificate chain of its choice
that may include algorithms that are not known to be supported by the
client. This fallback chain MAY use the deprecated SHA-1 hash
algorithm only if the "signature_algorithms" extension provided by
the client permits it. If the client cannot construct an acceptable
chain using the provided certificates and decides to abort the
handshake, then it MUST send an "unsupported_certificate" alert
message and close the connection.
If the server has multiple certificates, it chooses one of them based
on the above-mentioned criteria (in addition to other criteria, such
as transport layer endpoint, local configuration and preferences).
As cipher suites that specify new key exchange methods are specified
for the TLS protocol, they will imply the certificate format and the
required encoded keying information.
6.3.4.1.2. Client Certificate Selection
The following rules apply to certificates sent by the client:
In particular: In particular:
- The certificate type MUST be X.509v3 [RFC5280], unless explicitly - The certificate type MUST be X.509v3 [RFC5280], unless explicitly
negotiated otherwise (e.g., [RFC5081]). negotiated otherwise (e.g., [RFC5081]).
- If the certificate_authorities list in the certificate request - If the certificate_authorities list in the certificate request
message was non-empty, one of the certificates in the certificate message was non-empty, one of the certificates in the certificate
chain SHOULD be issued by one of the listed CAs. chain SHOULD be issued by one of the listed CAs.
- The certificates MUST be signed using an acceptable hash/ - The certificates MUST be signed using an acceptable hash/
signature algorithm pair, as described in Section 6.3.5. Note signature algorithm pair, as described in Section 6.3.3.2. Note
that this relaxes the constraints on certificate-signing that this relaxes the constraints on certificate-signing
algorithms found in prior versions of TLS. algorithms found in prior versions of TLS.
- If the certificate_extensions list in the certificate request - If the certificate_extensions list in the certificate request
message was non-empty, the end-entity certificate MUST match the message was non-empty, the end-entity certificate MUST match the
extension OIDs recognized by the client, as described in extension OIDs recognized by the client, as described in
Section 6.3.5. Section 6.3.3.2.
Note that, as with the server certificate, there are certificates Note that, as with the server certificate, there are certificates
that use algorithms/algorithm combinations that cannot be currently that use algorithm combinations that cannot be currently used with
used with TLS. TLS.
6.3.10. Client Certificate Verify 6.3.4.1.3. Receiving a Certificate Message
In general, detailed certificate validation procedures are out of
scope for TLS (see [RFC5280]). This section provides TLS-specific
requirements.
If server supplies an empty Certificate message, the client MUST
terminate the handshake with a fatal "decode_error" alert.
If the client does not send any certificates, the server MAY at its
discretion either continue the handshake without client
authentication, or respond with a fatal "handshake_failure" alert.
Also, if some aspect of the certificate chain was unacceptable (e.g.,
it was not signed by a known, trusted CA), the server MAY at its
discretion either continue the handshake (considering the client
unauthenticated) or send a fatal alert.
Any endpoint receiving any certificate signed using any signature
algorithm using an MD5 hash MUST send a "bad_certificate" alert
message and close the connection.
SHA-1 is deprecated and therefore NOT RECOMMENDED. Endpoints that
reject certification paths due to use of a deprecated hash MUST send
a fatal "bad_certificate" alert message before closing the
connection. All endpoints are RECOMMENDED to transition to SHA-256
or better as soon as possible to maintain interoperability with
implementations currently in the process of phasing out SHA-1
support.
Note that a certificate containing a key for one signature algorithm
MAY be signed using a different signature algorithm (for instance, an
RSA key signed with a ECDSA key).
6.3.4.2. Certificate Verify
When this message will be sent: When this message will be sent:
This message is used to provide explicit verification of a client This message is used to provide explicit proof that an endpoint
certificate. This message is only sent following a client possesses the private key corresponding to its certificate and
certificate that has signing capability (i.e., all certificates also provides integrity for the handshake up to this point.
except those containing fixed Diffie-Hellman parameters). When Servers MUST send this message when using a cipher suite which is
sent, it MUST immediately follow the client's Certificate message. authenticated via a certificate. Clients MUST send this message
The contents of the message are computed as described in whenever authenticating via a Certificate (i.e., when the
Section 6.3.7, except that the context string is "TLS 1.3, client Certificate message is non-empty). When sent, this message MUST
CertificateVerify". appear immediately after the Certificate Message and immediately
prior to the Finished message.
The hash and signature algorithms used in the signature MUST be Structure of this message:
one of those present in the supported_signature_algorithms field
of the CertificateRequest message. In addition, the hash and struct {
signature algorithms MUST be compatible with the key in the digitally-signed struct {
client's end-entity certificate. RSA keys MAY be used with any opaque hashed_data[hash_length];
permitted hash algorithm, subject to restrictions in the };
certificate, if any. RSA signatures MUST be based on RSASSA-PSS, } CertificateVerify;
regardless of whether RSASSA-PKCS-v1_5 appears in Where hashed_data is the hash output described in Section 6.3.4,
namely Hash(Handshake Context + Certificate).
The context string for a server signature is "TLS 1.3, server
CertificateVerify" and for a client signature is "TLS 1.3, client
CertificateVerify". A hash of the handshake messages is signed
rather than the messages themselves because the digitally-signed
format requires padding and context bytes at the beginning of the
input. Thus, by signing a digest of the messages, an
implementation need only maintain one running hash per hash type
for CertificateVerify, Finished and other messages.
If sent by a server, the signature algorithm and hash algorithm
MUST be a pair offered in the client's "signature_algorithms"
extension unless no valid certificate chain can be produced
without unsupported algorithms (see Section 6.3.2.1). Note that
there is a possibility for inconsistencies here. For instance,
the client might offer ECDHE_ECDSA key exchange but omit any ECDSA
and EdDSA pairs from its "signature_algorithms" extension. In
order to negotiate correctly, the server MUST check any candidate
cipher suites against the "signature_algorithms" extension before
selecting them. This is somewhat inelegant but is a compromise
designed to minimize changes to the original cipher suite design.
If sent by a client, the hash and signature algorithms used in the
signature MUST be one of those present in the
supported_signature_algorithms field of the CertificateRequest
message.
In addition, the hash and signature algorithms MUST be compatible
with the key in the sender's end-entity certificate. RSA keys MAY
be used with any permitted hash algorithm, subject to restrictions
in the certificate, if any. RSA signatures MUST be based on
RSASSA-PSS, regardless of whether RSASSA-PKCS-v1_5 appears in
"signature_algorithms". SHA-1 MUST NOT be used in any signatures "signature_algorithms". SHA-1 MUST NOT be used in any signatures
in CertificateVerify, regardless of whether SHA-1 appears in in CertificateVerify, regardless of whether SHA-1 appears in
"signature_algorithms". "signature_algorithms".
6.3.11. New Session Ticket Message Note: when used with non-certificate-based handshakes (e.g., PSK),
the client's signature does not cover the server's certificate
directly, although it does cover the server's Finished message, which
transitively includes the server's certificate when the PSK derives
from a certificate-authenticated handshake. [PSK-FINISHED] describes
a concrete attack on this mode if the Finished is omitted from the
signature. It is unsafe to use certificate-based client
authentication when the client might potentially share the same PSK/
key-id pair with two different endpoints. In order to ensure this,
implementations MUST NOT mix certificate-based client authentication
with pure PSK modes (i.e., those where the PSK was not derived from a
previous non-PSK handshake).
6.3.4.3. Finished
When this message will be sent:
The Finished message is the final message in the authentication
block. It is essential for providing authentication of the
handshake and of the computed keys.
Meaning of this message:
Recipients of Finished messages MUST verify that the contents are
correct. Once a side has sent its Finished message and received
and validated the Finished message from its peer, it may begin to
send and receive application data over the connection. This data
will be protected under keys derived from the ephemeral secret
(see Section 7).
The key used to compute the finished message is computed from the
Base key defined in Section 6.3.4 using HKDF (see Section 7.1).
Specifically:
client_finished_key =
HKDF-Expand-Label(BaseKey, "client finished", "", L)
server_finished_key =
HKDF-Expand-Label(BaseKey, "server finished", "", L)
Structure of this message:
struct {
opaque verify_data[verify_data_length];
} Finished;
The verify_data value is computed as follows:
verify_data =
HMAC(finished_key, Hash(
Handshake Context + Certificate* + CertificateVerify*
))
* Only included if present.
Where HMAC [RFC2104] uses the Hash algorithm for the handshake. As
noted above: the HMAC input can generally be implemented by a running
hash, i.e., just the handshake hash at this point.
In previous versions of TLS, the verify_data was always 12 octets
long. In the current version of TLS, it is the size of the HMAC
output for the Hash used for the handshake.
Note: Alerts and any other record types are not handshake messages
and are not included in the hash computations.
6.3.5. Post-Handshake Messages
TLS also allows other messages to be sent after the main handshake.
These message use a handshake content type and are encrypted under
the application traffic key.
6.3.5.1. New Session Ticket Message
After the server has received the client Finished message, it MAY After the server has received the client Finished message, it MAY
send a NewSessionTicket message. This message MUST be sent before send a NewSessionTicket message. This message creates a pre-shared
the server sends any application data traffic, and is encrypted under key (PSK) binding between the resumption master secret and the ticket
the application traffic key. This message creates a pre-shared key
(PSK) binding between the resumption master secret and the ticket
label. The client MAY use this PSK for future handshakes by label. The client MAY use this PSK for future handshakes by
including it in the "pre_shared_key" extension in its ClientHello including it in the "pre_shared_key" extension in its ClientHello
(Section 6.3.2.4) and supplying a suitable PSK cipher suite. (Section 6.3.2.4) and supplying a suitable PSK cipher suite.
struct { struct {
uint32 ticket_lifetime_hint; uint32 ticket_lifetime_hint;
opaque ticket<0..2^16-1>; opaque ticket<0..2^16-1>;
} NewSessionTicket; } NewSessionTicket;
ticket_lifetime_hint ticket_lifetime_hint
skipping to change at page 68, line 9 skipping to change at page 72, line 9
The ticket itself is an opaque label. It MAY either be a database The ticket itself is an opaque label. It MAY either be a database
lookup key or a self-encrypted and self-authenticated value. lookup key or a self-encrypted and self-authenticated value.
Section 4 of [RFC5077] describes a recommended ticket construction Section 4 of [RFC5077] describes a recommended ticket construction
mechanism. mechanism.
[[TODO: Should we require that tickets be bound to the existing [[TODO: Should we require that tickets be bound to the existing
symmetric cipher suite. See the TODO above about early_data and symmetric cipher suite. See the TODO above about early_data and
PSK.??] PSK.??]
6.3.5.2. Post-Handshake Authentication
The server is permitted to request client authentication at any time
after the handshake has completed by sending a CertificateRequest
message. The client SHOULD respond with the appropriate
Authentication messages. If the client chooses to authenticate, it
MUST send Certificate, CertificateVerify, and Finished. If it
declines, it MUST send a Certificate message containing no
certificates followed by Finished.
Note: Because client authentication may require prompting the user,
servers MUST be prepared for some delay, including receiving an
arbitrary number of other messages between sending the
CertificateRequest and receiving a response. In addition, clients
which receive multiple CertificateRequests in close succession MAY
respond to them in a different order than they were received (the
certificate_request_context value allows the server to disambiguate
the responses).
6.3.5.3. Key and IV Update
struct {} KeyUpdate;
The KeyUpdate handshake message is used to indicate that the sender
is updating its sending cryptographic keys. This message can be sent
by the server after sending its first flight and the client after
sending its second flight. Implementations that receive a KeyUpdate
message prior to receiving a Finished message as part of the 1-RTT
handshake MUST generate a fatal "unexpected_message" alert. After
sending a KeyUpdate message, the sender SHALL send all its traffic
using the next generation of keys, computed as described in
Section 7.2. Upon receiving a KeyUpdate, the receiver MUST update
their receiving keys and if they have not already updated their
sending state up to or past the then current receiving generation
MUST send their own KeyUpdate prior to sending any other messages.
This mechanism allows either side to force an update to the entire
connection. Note that implementations may receive an arbitrary
number of messages between sending a KeyUpdate and receiving the
peer's KeyUpdate because those messages may already be in flight.
Note that if implementations independently send their own KeyUpdates
and they cross in flight, this only results in an update of one
generation; when each side receives the other side's update it just
updates its receive keys and notes that the generations match and
thus no send update is needed.
Note that the side which sends its KeyUpdate first needs to retain
the traffic keys (though not the traffic secret) for the previous
generation of keys until it receives the KeyUpdate from the other
side.
7. Cryptographic Computations 7. Cryptographic Computations
In order to begin connection protection, the TLS Record Protocol In order to begin connection protection, the TLS Record Protocol
requires specification of a suite of algorithms, a master secret, and requires specification of a suite of algorithms, a master secret, and
the client and server random values. The authentication, key the client and server random values. The authentication, key
exchange, and record protection algorithms are determined by the exchange, and record protection algorithms are determined by the
cipher_suite selected by the server and revealed in the ServerHello cipher_suite selected by the server and revealed in the ServerHello
message. The random values are exchanged in the hello messages. All message. The random values are exchanged in the hello messages. All
that remains is to calculate the key schedule. that remains is to calculate the key schedule.
7.1. Key Schedule 7.1. Key Schedule
The TLS handshake establishes secret keying material which is then The TLS handshake establishes secret keying material which is then
used to protect traffic. This keying material is derived from the used to protect traffic. This keying material is derived from the
two input secret values: Static Secret (SS) and Ephemeral Secret two input secret values: Static Secret (SS) and Ephemeral Secret
(ES). (ES).
The exact source of each of these secrets depends on the operational The exact source of each of these secrets depends on the operational
mode (DHE, ECDHE, PSK, etc.) and is summarized in the table below: mode (DHE, ECDHE, PSK, etc.) and is summarized in the table below:
Key Exchange Static Secret (SS) Ephemeral Secret (ES) +-----------------+------------------------+------------------------+
------------ ------------------ --------------------- | Key Exchange | Static Secret (SS) | Ephemeral Secret (ES) |
(EC)DHE Client ephemeral Client ephemeral +-----------------+------------------------+------------------------+
(full handshake) w/ server ephemeral w/ server ephemeral | (EC)DHE (full | Client ephemeral w/ | Client ephemeral w/ |
| handshake) | server ephemeral | server ephemeral |
(EC)DHE Client ephemeral Client ephemeral | | | |
(w/ 0-RTT) w/ server static w/ server ephemeral | (EC)DHE (w/ | Client ephemeral w/ | Client ephemeral w/ |
| 0-RTT) | server static | server ephemeral |
PSK Pre-Shared Key Pre-shared key | | | |
| PSK | Pre-Shared Key | Pre-shared key |
PSK + (EC)DHE Pre-Shared Key Client ephemeral | | | |
w/ server ephemeral | PSK + (EC)DHE | Pre-Shared Key | Client ephemeral w/ |
| | | server ephemeral |
+-----------------+------------------------+------------------------+
These shared secret values are used to generate cryptographic keys as These shared secret values are used to generate cryptographic keys as
shown below. shown below.
The derivation process is as follows, where L denotes the length of The derivation process is as follows, where L denotes the length of
the underlying hash function for HKDF [RFC5869]. SS and ES denote the underlying hash function for HKDF [RFC5869]. SS and ES denote
the sources from the table above. Whilst SS and ES may be the same the sources from the table above.
in some cases, the extracted xSS and xES will not.
HKDF-Expand-Label(Secret, Label, HashValue, Length) = HKDF-Expand-Label(Secret, Label, HashValue, Length) =
HKDF-Expand(Secret, HkdfLabel, Length) HKDF-Expand(Secret, HkdfLabel, Length)
Where HkdfLabel is specified as: Where HkdfLabel is specified as:
struct HkdfLabel { struct HkdfLabel {
uint16 length; uint16 length;
opaque hash_value<0..255>;
opaque label<9..255>; opaque label<9..255>;
opaque hash_value<0..255>;
}; };
Where: Where:
- HkdfLabel.length is Length - HkdfLabel.length is Length
- HkdfLabel.hash_value is HashValue.
- HkdfLabel.label is "TLS 1.3, " + Label - HkdfLabel.label is "TLS 1.3, " + Label
- HkdfLabel.hash_value is HashValue.
1. xSS = HKDF-Extract(0, SS). Note that HKDF-Extract always 1. xSS = HKDF-Extract(0, SS). Note that HKDF-Extract always
produces a value the same length as the underlying hash produces a value the same length as the underlying hash
function. function.
2. xES = HKDF-Extract(0, ES) 2. xES = HKDF-Extract(0, ES)
3. mSS = HKDF-Expand-Label(xSS, "expanded static secret", 3. mSS = HKDF-Expand-Label(xSS, "expanded static secret",
handshake_hash, L) handshake_hash, L)
4. mES = HKDF-Expand-Label(xES, "expanded ephemeral secret", 4. mES = HKDF-Expand-Label(xES, "expanded ephemeral secret",
handshake_hash, L) handshake_hash, L)
5. master_secret = HKDF-Extract(mSS, mES) 5. master_secret = HKDF-Extract(mSS, mES)
6. finished_secret = HKDF-Expand-Label(xSS, 6. traffic_secret_0 = HKDF-Expand-Label(master_secret,
"finished secret", "traffic secret",
handshake_hash, L) handshake_hash, L)
Where handshake_hash includes all the messages in the Where handshake_hash includes all messages up through the
client's first flight and the server's flight, excluding server CertificateVerify message, but not including any
the Finished messages (which are never included in the 0-RTT handshake messages (the server's Finished is not
hashes). included because the master_secret is need to compute
the finished key). [[OPEN ISSUE: Should we be including
0-RTT handshake messages here and below?.
https://github.com/tlswg/tls13-spec/issues/351
]] At this point,
SS, ES, xSS, xES, mSS, and mSS SHOULD be securely deleted,
along with any ephemeral (EC)DH secrets.
5. resumption_secret = HKDF-Expand-Label(master_secret, 7. resumption_secret = HKDF-Expand-Label(master_secret,
"resumption master secret" "resumption master secret"
session_hash, L) handshake_hash, L)
Where session_hash is as defined in {{the-handshake-hash}}.
6. exporter_secret = HKDF-Expand-Label(master_secret, 8. exporter_secret = HKDF-Expand-Label(master_secret,
"exporter master secret", "exporter master secret",
session_hash, L) handshake_hash, L)
Where session_hash is the session hash as defined in Where handshake_hash contains the entire handshake up to
{{the-handshake-hash}} (i.e., the entire handshake except and including the client's Finished, but not including
for Finished). any 0-RTT handshake messages or post-handshake messages.
AT this point master_secret SHOULD be securely deleted.
The traffic keys are computed from xSS, xES, and the master_secret as The traffic keys are computed from xSS, xES, and the traffic_secret
described in Section 7.2 below. as described in Section 7.3 below. The traffic_secret may be updated
throughout the connection as described in Section 7.2.
Note: although the steps above are phrased as individual HKDF-Extract Note: although the steps above are phrased as individual HKDF-Extract
and HKDF-Expand operations, because each HKDF-Expand operation is and HKDF-Expand operations, because each HKDF-Expand operation is
paired with an HKDF-Extract, it is possible to implement this key paired with an HKDF-Extract, it is possible to implement this key
schedule with a black-box HKDF API, albeit at some loss of efficiency schedule with a black-box HKDF API, albeit at some loss of efficiency
as some HKDF-Extract operations will be repeated. as some HKDF-Extract operations will be repeated.
7.2. Traffic Key Calculation 7.2. Updating Traffic Keys and IVs
[[OPEN ISSUE: This needs to be revised. Most likely we'll extract Once the handshake is complete, it is possible for either side to
each key component separately. See https://github.com/tlswg/tls13- update its sending traffic keys using the KeyUpdate handshake message
spec/issues/5]] Section 6.3.5.3. The next generation of traffic keys is computed by
generating traffic_secret_N+1 from traffic_secret_N as described in
this section then re-deriving the traffic keys as described in
Section 7.3.
The Record Protocol requires an algorithm to generate keys required The next-generation traffic_secret is computed as:
by the current connection state (see Appendix A.5) from the security
parameters provided by the handshake protocol.
The traffic key computation takes four input values and returns a key traffic_secret_N+1 = HKDF-Expand-Label(traffic_secret_N, "traffic
block of sufficient size to produce the needed traffic keys: secret", "", L)
- A secret value Once traffic_secret_N+1 and its associated traffic keys have been
computed, implementations SHOULD delete traffic_secret_N. Once the
directional keys are no longer needed, they SHOULD be deleted as
well.
- A string label that indicates the purpose of keys being generated. 7.3. Traffic Key Calculation
- The current handshake hash. The traffic keying material is generated from the following input
values:
- The total length in octets of the key block. - A secret value
The keying material is computed using: - A phase value indicating the phase of the protocol the keys are
being generated for.
key_block = HKDF-Expand-Label(Secret, Label, - A purpose value indicating the specific value being generated
handshake_hash,
total_length)
The key_block is partitioned as follows: - The length of the key.
client_write_key[SecurityParameters.enc_key_length] - The handshake context which is used to generate the keys.
server_write_key[SecurityParameters.enc_key_length]
client_write_IV[SecurityParameters.iv_length]
server_write_IV[SecurityParameters.iv_length]
The following table describes the inputs to the key calculation for The keying material is computed using:
each class of traffic keys:
Record Type Secret Label Handshake Hash key = HKDF-Expand-Label(Secret,
----------- ------ ----- --------------- phase + ", " + purpose,
Early data xSS "early data key expansion" ClientHello handshake_context,
key_length)
Handshake xES "handshake key expansion" ClientHello... The following table describes the inputs to the key calculation for
ServerHello each class of traffic keys:
Application master "application data key expansion" All handshake +-------------+---------+-----------------+-------------------------+
secret messages but | Record Type | Secret | Label | Handshake Context |
Finished +-------------+---------+-----------------+-------------------------+
(session_hash) | 0-RTT | xSS | "early | ClientHello + |
| Handshake | | handshake key | ServerConfiguration + |
| | | expansion" | Server Certificate |
| | | | |
| 0-RTT | xSS | "early | ClientHello + |
| Application | | application | ServerConfiguration + |
| | | data key | Server Certificate |
| | | expansion" | |
| | | | |
| Handshake | xES | "handshake key | ClientHello... |
| | | expansion" | ServerHello |
| | | | |
| Application | traffic | "application | ClientHello... Server |
| Data | secret | data key | Finished |
| | | expansion" | |
+-------------+---------+-----------------+-------------------------+
7.2.1. The Handshake Hash The following table indicates the purpose values for each type of
key:
handshake_hash = Hash( +------------------+--------------------+
Hash(handshake_messages) || | Key Type | Purpose |
Hash(configuration) +------------------+--------------------+
) | Client Write Key | "client write key" |
| | |
| Server Write Key | "server write key" |
| | |
| Client Write IV | "client write IV" |
| | |
| Server Write IV | "server write IV" |
+------------------+--------------------+
handshake_messages All the traffic keying material is recomputed whenever the underlying
All handshake messages sent or received, starting at ClientHello Secret changes (e.g., when changing from the handshake to application
up to the present time, with the exception of the Finished data keys or upon a key update).
message, including the type and length fields of the handshake
messages. This is the concatenation of all the exchanged
Handshake structures in plaintext form (even if they were
encrypted on the wire).
configuration 7.3.1. The Handshake Hash
When 0-RTT is in use (Section 6.3.2.5) this contains the
concatenation of the ServerConfiguration and Certificate messages
from the handshake where the configuration was established
(including the type and length fields). Note that this requires
the client and server to memorize these values.
This final value of the handshake hash is referred to as the "session The handshake hash is defined as the hash of all handshake messages
hash" because it contains all the handshake messages required to sent or received, starting at ClientHello up to the present time,
establish the session. Note that if client authentication is not with the exception of the client's 0-RTT authentication messages
used, then the session hash is complete at the point when the server (Certificate, CertificateVerify, and Finished) including the type and
has sent its first flight. Otherwise, it is only complete when the length fields of the handshake messages. This is the concatenation
client has sent its first flight, as it covers the client's the exchanged Handshake structures in plaintext form (even if they
Certificate and CertificateVerify. were encrypted on the wire). [[OPEN ISSUE: See
https://github.com/tlswg/tls13-spec/issues/351 for the question of
whether the 0-RTT handshake messages are hashed.]]
7.2.2. Diffie-Hellman 7.3.2. Diffie-Hellman
A conventional Diffie-Hellman computation is performed. The A conventional Diffie-Hellman computation is performed. The
negotiated key (Z) is used as the shared secret, and is used in the negotiated key (Z) is used as the shared secret, and is used in the
key schedule as specified above. Leading bytes of Z that contain all key schedule as specified above. Leading bytes of Z that contain all
zero bits are stripped before it is used as the input to HKDF. zero bits are stripped before it is used as the input to HKDF.
7.2.3. Elliptic Curve Diffie-Hellman 7.3.3. Elliptic Curve Diffie-Hellman
All ECDH calculations (including parameter and key generation as well For secp256r1, secp384r1 and secp521r1, ECDH calculations (including
as the shared secret calculation) are performed according to [6] parameter and key generation as well as the shared secret
using the ECKAS-DH1 scheme with the identity map as key derivation calculation) are performed according to [IEEE1363] using the ECKAS-
function (KDF), so that the shared secret is the x-coordinate of the DH1 scheme with the identity map as key derivation function (KDF), so
ECDH shared secret elliptic curve point represented as an octet that the shared secret is the x-coordinate of the ECDH shared secret
string. Note that this octet string (Z in IEEE 1363 terminology) as elliptic curve point represented as an octet string. Note that this
output by FE2OSP, the Field Element to Octet String Conversion octet string (Z in IEEE 1363 terminology) as output by FE2OSP, the
Primitive, has constant length for any given field; leading zeros Field Element to Octet String Conversion Primitive, has constant
found in this octet string MUST NOT be truncated. length for any given field; leading zeros found in this octet string
MUST NOT be truncated.
(Note that this use of the identity KDF is a technicality. The (Note that this use of the identity KDF is a technicality. The
complete picture is that ECDH is employed with a non-trivial KDF complete picture is that ECDH is employed with a non-trivial KDF
because TLS does not directly use this secret for anything other than because TLS does not directly use this secret for anything other than
for computing other secrets.) for computing other secrets.)
ECDH functions are used as follows:
- The public key to put into ECPoint.point structure is the result
of applying the ECDH function to the secret key of appropriate
length (into scalar input) and the standard public basepoint (into
u-coordinate point input).
- The ECDH shared secret is the result of applying ECDH function to
the secret key (into scalar input) and the peer's public key (into
u-coordinate point input). The output is used raw, with no
processing.
For X25519 and X448, see [I-D.irtf-cfrg-curves].
8. Mandatory Algorithms 8. Mandatory Algorithms
8.1. MTI Cipher Suites 8.1. MTI Cipher Suites
In the absence of an application profile standard specifying In the absence of an application profile standard specifying
otherwise, a TLS-compliant application MUST implement the following otherwise, a TLS-compliant application MUST implement the following
cipher suites: cipher suites:
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
These cipher suites MUST support both digital signatures and key These cipher suites MUST support both digital signatures and key
exchange with secp256r1 (NIST P-256) and SHOULD support key exchange exchange with secp256r1 (NIST P-256) and SHOULD support key exchange
with X25519 [I-D.irtf-cfrg-curves]. with X25519 [I-D.irtf-cfrg-curves].
A TLS-compliant application SHOULD implement the following cipher A TLS-compliant application SHOULD implement the following cipher
suites: suites:
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305 TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
8.2. MTI Extensions 8.2. MTI Extensions
In the absence of an application profile standard specifying In the absence of an application profile standard specifying
otherwise, a TLS-compliant application MUST implement the following otherwise, a TLS-compliant application MUST implement the following
TLS extensions: TLS extensions:
- Signature Algorithms ("signature_algorithms"; Section 6.3.2.1) - Signature Algorithms ("signature_algorithms"; Section 6.3.2.1)
- Negotiated Groups ("supported_groups"; Section 6.3.2.2) - Negotiated Groups ("supported_groups"; Section 6.3.2.2)
- Key Share ("key_share"; Section 6.3.2.3) - Key Share ("key_share"; Section 6.3.2.3)
- Pre-Shared Key Extension ("pre_shared_key"; Section 6.3.2.4) - Pre-Shared Key ("pre_shared_key"; Section 6.3.2.4)
- Server Name Indication ("server_name"; Section 3 of [RFC6066]) - Server Name Indication ("server_name"; Section 3 of [RFC6066])
All implementations MUST send and use these extensions when offering All implementations MUST send and use these extensions when offering
applicable cipher suites: applicable cipher suites:
- "signature_algorithms" is REQUIRED for certificate authenticated - "signature_algorithms" is REQUIRED for certificate authenticated
cipher suites cipher suites
- "supported_groups" and "key_share" are REQUIRED for DHE or ECDHE - "supported_groups" and "key_share" are REQUIRED for DHE or ECDHE
skipping to change at page 73, line 40 skipping to change at page 79, line 43
Additionally, all implementations MUST support use of the Additionally, all implementations MUST support use of the
"server_name" extension with applications capable of using it. "server_name" extension with applications capable of using it.
Servers MAY require clients to send a valid "server_name" extension. Servers MAY require clients to send a valid "server_name" extension.
Servers requiring this extension SHOULD respond to a ClientHello Servers requiring this extension SHOULD respond to a ClientHello
lacking a "server_name" extension with a fatal "missing_extension" lacking a "server_name" extension with a fatal "missing_extension"
alert. alert.
Some of these extensions exist only for the client to provide Some of these extensions exist only for the client to provide
additional data to the server in a backwards-compatible way and thus additional data to the server in a backwards-compatible way and thus
have no meaning when sent from a server. The client-only extensions have no meaning when sent from a server. The client-only extensions
defined in this document are: "Signature Algorithms" & "Negotiated defined in this document are: "signature_algorithms" &
Groups". Servers MUST NOT send these extensions. Clients receiving "supported_groups". Servers MUST NOT send these extensions. Clients
any of these extensions MUST respond with a fatal receiving any of these extensions MUST respond with a fatal
"unsupported_extension" alert and close the connection. "unsupported_extension" alert and close the connection.
9. Application Data Protocol 9. Application Data Protocol
Application data messages are carried by the record layer and are Application data messages are carried by the record layer and are
fragmented and encrypted based on the current connection state. The fragmented and encrypted based on the current connection state. The
messages are treated as transparent data to the record layer. messages are treated as transparent data to the record layer.
10. Security Considerations 10. Security Considerations
Security issues are discussed throughout this memo, especially in Security issues are discussed throughout this memo, especially in
Appendices B, C, and D. Appendices B, C, and D.
11. IANA Considerations 11. IANA Considerations
[[TODO: Update https://github.com/tlswg/tls13-spec/issues/62]]
[[TODO: Rename "RSA" in TLS SignatureAlgorithm Registry to RSASSA- [[TODO: Rename "RSA" in TLS SignatureAlgorithm Registry to RSASSA-
PKCS1-v1_5 ]] PKCS1-v1_5 ]]
This document uses several registries that were originally created in This document uses several registries that were originally created in
[RFC4346]. IANA has updated these to reference this document. The [RFC4346]. IANA has updated these to reference this document. The
registries and their allocation policies (unchanged from [RFC4346]) registries and their allocation policies are below:
are listed below.
- TLS Cipher Suite Registry: Future values with the first byte in - TLS Cipher Suite Registry: Values with the first byte in the range
the range 0-191 (decimal) inclusive are assigned via Standards 0-254 (decimal) are assigned via Specification Required [RFC2434].
Action [RFC2434]. Values with the first byte in the range 192-254
(decimal) are assigned via Specification Required [RFC2434].
Values with the first byte 255 (decimal) are reserved for Private Values with the first byte 255 (decimal) are reserved for Private
Use [RFC2434]. Use [RFC2434]. IANA [SHALL add/has added] a "Recommended" column
to the cipher suite registry. All cipher suites listed in
Appendix A.4 are marked as "Yes". All other cipher suites are
marked as "No". IANA [SHALL add/has added] add a note to this
column reading:
Cipher suites marked as "Yes" are those allocated via Standards
Track RFCs. Cipher suites marked as "No" are not; cipher
suites marked "No" range from "good" to "bad" from a
cryptographic standpoint.
- TLS ContentType Registry: Future values are allocated via - TLS ContentType Registry: Future values are allocated via
Standards Action [RFC2434]. Standards Action [RFC2434].
- TLS Alert Registry: Future values are allocated via Standards - TLS Alert Registry: Future values are allocated via Standards
Action [RFC2434]. Action [RFC2434].
- TLS HandshakeType Registry: Future values are allocated via - TLS HandshakeType Registry: Future values are allocated via
Standards Action [RFC2434]. Standards Action [RFC2434].
This document also uses a registry originally created in [RFC4366]. This document also uses a registry originally created in [RFC4366].
IANA has updated it to reference this document. The registry and its IANA has updated it to reference this document. The registry and its
allocation policy (unchanged from [RFC4366]) is listed below: allocation policy is listed below:
- TLS ExtensionType Registry: Future values are allocated via IETF
Consensus [RFC2434]. IANA has updated this registry to include
the "signature_algorithms" extension and its corresponding value
(see Section 6.3.2).
This document also uses two registries originally created in - TLS ExtensionType Registry: Values with the first byte in the
[RFC4492]. IANA [should update/has updated] it to reference this range 0-254 (decimal) are assigned via Specification Required
document. The registries and their allocation policies are listed [RFC2434]. Values with the first byte 255 (decimal) are reserved
below. for Private Use [RFC2434]. IANA [SHALL update/has updated] this
registry to include the "key_share", "pre_shared_key", and
"early_data" extensions as defined in this document.
- TLS NamedCurve registry: Future values are allocated via IETF IANA [shall update/has updated] this registry to include a "TLS
Consensus [RFC2434]. 1.3" column with the following four values: "Client", indicating
that the server shall not send them. "Clear", indicating that
they shall be in the ServerHello. "Encrypted", indicating that
they shall be in the EncryptedExtensions block, and "No"
indicating that they are not used in TLS 1.3. This column [shall
be/has been] initially populated with the values in this document.
IANA [shall update/has updated] this registry to add a
"Recommended" column. IANA [shall/has] initially populated this
column with the values in the table below. This table has been
generated by marking Standards Track RFCs as "Yes" and all others
as "No".
- TLS ECPointFormat Registry: Future values are allocated via IETF +-------------------------------------------+------------+----------+
Consensus [RFC2434]. | Extension | Recommende | TLS 1.3 |
| | d | |
+-------------------------------------------+------------+----------+
| server_name [RFC6066] | Yes | Encrypte |
| | | d |
| | | |
| max_fragment_length [RFC6066] | Yes | Encrypte |
| | | d |
| | | |
| client_certificate_url [RFC6066] | Yes | Encrypte |
| | | d |
| | | |
| trusted_ca_keys [RFC6066] | Yes | Encrypte |
| | | d |
| | | |
| truncated_hmac [RFC6066] | Yes | No |
| | | |
| status_request [RFC6066] | Yes | No |
| | | |
| user_mapping [RFC4681] | Yes | Encrypte |
| | | d |
| | | |
| client_authz [RFC5878] | No | Encrypte |
| | | d |
| | | |
| server_authz [RFC5878] | No | Encrypte |
| | | d |
| | | |
| cert_type [RFC6091] | Yes | Encrypte |
| | | d |
| | | |
| supported_groups [RFC-ietf-tls- | Yes | Client |
| negotiated-ff-dhe] | | |
| | | |
| ec_point_formats [RFC4492] | Yes | No |
| | | |
| srp [RFC5054] | No | No |
| | | |
| signature_algorithms [RFC5246] | Yes | Client |
| | | |
| use_srtp [RFC5764] | Yes | Encrypte |
| | | d |
| | | |
| heartbeat [RFC6520] | Yes | Encrypte |
| | | d |
| | | |
| application_layer_protocol_negotiation[RF | Yes | Encrypte |
| C7301] | | d |
| | | |
| status_request_v2 [RFC6961] | Yes | Encrypte |
| | | d |
| | | |
| signed_certificate_timestamp [RFC6962] | No | Encrypte |
| | | d |
| | | |
| client_certificate_type [RFC7250] | Yes | Encrypte |
| | | d |
| | | |
| server_certificate_type [RFC7250] | Yes | Encrypte |
| | | d |
| | | |
| padding [RFC7685] | Yes | Client |
| | | |
| encrypt_then_mac [RFC7366] | Yes | No |
| | | |
| extended_master_secret [RFC7627] | Yes | No |
| | | |
| SessionTicket TLS [RFC4507] | Yes | No |
| | | |
| renegotiation_info [RFC5746] | Yes | No |
| | | |
| key_share [[this document]] | Yes | Clear |
| | | |
| pre_shared_key [[this document]] | Yes | Clear |
| | | |
| early_data [[this document]] | Yes | Clear |
+-------------------------------------------+------------+----------+
In addition, this document defines two new registries to be This document reuses two registries defined in [RFC5246].
maintained by IANA:
- TLS SignatureAlgorithm Registry: The registry has been initially - TLS SignatureAlgorithm Registry: The registry has been initially
populated with the values described in Section 6.3.2.1. Future populated with the values described in Section 6.3.2.1. Future
values in the range 0-63 (decimal) inclusive are assigned via values in the range 0-63 (decimal) inclusive are assigned via
Standards Action [RFC2434]. Values in the range 64-223 (decimal) Standards Action [RFC2434]. Values in the range 64-223 (decimal)
inclusive are assigned via Specification Required [RFC2434]. inclusive are assigned via Specification Required [RFC2434].
Values from 224-255 (decimal) inclusive are reserved for Private Values from 224-255 (decimal) inclusive are reserved for Private
Use [RFC2434]. Use [RFC2434].
- TLS HashAlgorithm Registry: The registry has been initially - TLS HashAlgorithm Registry: The registry has been initially
populated with the values described in Section 6.3.2.1. Future populated with the values described in Section 6.3.2.1. Future
values in the range 0-63 (decimal) inclusive are assigned via values in the range 0-63 (decimal) inclusive are assigned via
Standards Action [RFC2434]. Values in the range 64-223 (decimal) Standards Action [RFC2434]. Values in the range 64-223 (decimal)
inclusive are assigned via Specification Required [RFC2434]. inclusive are assigned via Specification Required [RFC2434].
Values from 224-255 (decimal) inclusive are reserved for Private Values from 224-255 (decimal) inclusive are reserved for Private
Use [RFC2434]. Use [RFC2434].
In addition, this document defines a new registry to be maintained by
IANA.
- TLS ConfigurationExtensionType Registry: Values with the first
byte in the range 0-254 (decimal) are assigned via Specification
Required [RFC2434]. Values with the first byte 255 (decimal) are
reserved for Private Use [RFC2434]. This registry SHALL have a
"Recommended" column. The registry [shall be/ has been] initially
populated with the values described in Section 6.3.3.3, with all
values marked with "Recommended" value "Yes".
12. References 12. References
12.1. Normative References 12.1. Normative References
[AES] National Institute of Standards and Technology, [AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard "Specification for the Advanced Encryption Standard
(AES)", NIST FIPS 197, November 2001. (AES)", NIST FIPS 197, November 2001.
[DH] Diffie, W. and M. Hellman, "New Directions in [DH] Diffie, W. and M. Hellman, "New Directions in
Cryptography", IEEE Transactions on Information Theory, Cryptography", IEEE Transactions on Information Theory,
V.IT-22 n.6 , June 1977. V.IT-22 n.6 , June 1977.
[I-D.ietf-tls-chacha20-poly1305] [I-D.ietf-tls-chacha20-poly1305]
Langley, A., Chang, W., Mavrogiannopoulos, N., Langley, A., Chang, W., Mavrogiannopoulos, N.,
Strombergson, J., and S. Josefsson, "The ChaCha20-Poly1305 Strombergson, J., and S. Josefsson, "ChaCha20-Poly1305
AEAD Cipher for Transport Layer Security", draft-ietf-tls- Cipher Suites for Transport Layer Security (TLS)", draft-
chacha20-poly1305-00 (work in progress), June 2015. ietf-tls-chacha20-poly1305-04 (work in progress), December
2015.
[I-D.irtf-cfrg-curves] [I-D.irtf-cfrg-curves]
Langley, A. and M. Hamburg, "Elliptic Curves for Langley, A. and M. Hamburg, "Elliptic Curves for
Security", draft-irtf-cfrg-curves-08 (work in progress), Security", draft-irtf-cfrg-curves-11 (work in progress),
September 2015. October 2015.
[I-D.irtf-cfrg-eddsa]
Josefsson, S. and I. Liusvaara, "Edwards-curve Digital
Signature Algorithm (EdDSA)", draft-irtf-cfrg-eddsa-01
(work in progress), December 2015.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, DOI Hashing for Message Authentication", RFC 2104,
10.17487/RFC2104, February 1997, DOI 10.17487/RFC2104, February 1997,
<http://www.rfc-editor.org/info/rfc2104>. <http://www.rfc-editor.org/info/rfc2104>.
[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, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434, DOI IANA Considerations Section in RFCs", RFC 2434,
10.17487/RFC2434, October 1998, DOI 10.17487/RFC2434, October 1998,
<http://www.rfc-editor.org/info/rfc2434>. <http://www.rfc-editor.org/info/rfc2434>.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography [RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February
2003, <http://www.rfc-editor.org/info/rfc3447>. 2003, <http://www.rfc-editor.org/info/rfc3447>.
[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,
<http://www.rfc-editor.org/info/rfc5280>. <http://www.rfc-editor.org/info/rfc5280>.
[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois [RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
Counter Mode (GCM) Cipher Suites for TLS", RFC 5288, DOI Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
10.17487/RFC5288, August 2008, DOI 10.17487/RFC5288, August 2008,
<http://www.rfc-editor.org/info/rfc5288>. <http://www.rfc-editor.org/info/rfc5288>.
[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA- [RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
256/384 and AES Galois Counter Mode (GCM)", RFC 5289, DOI 256/384 and AES Galois Counter Mode (GCM)", RFC 5289,
10.17487/RFC5289, August 2008, DOI 10.17487/RFC5289, August 2008,
<http://www.rfc-editor.org/info/rfc5289>. <http://www.rfc-editor.org/info/rfc5289>.
[RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/ Key Derivation Function (HKDF)", RFC 5869,
RFC5869, May 2010, DOI 10.17487/RFC5869, May 2010,
<http://www.rfc-editor.org/info/rfc5869>. <http://www.rfc-editor.org/info/rfc5869>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066, DOI Extensions: Extension Definitions", RFC 6066,
10.17487/RFC6066, January 2011, DOI 10.17487/RFC6066, January 2011,
<http://www.rfc-editor.org/info/rfc6066>. <http://www.rfc-editor.org/info/rfc6066>.
[RFC6209] Kim, W., Lee, J., Park, J., and D. Kwon, "Addition of the [RFC6209] Kim, W., Lee, J., Park, J., and D. Kwon, "Addition of the
ARIA Cipher Suites to Transport Layer Security (TLS)", RFC ARIA Cipher Suites to Transport Layer Security (TLS)",
6209, DOI 10.17487/RFC6209, April 2011, RFC 6209, DOI 10.17487/RFC6209, April 2011,
<http://www.rfc-editor.org/info/rfc6209>. <http://www.rfc-editor.org/info/rfc6209>.
[RFC6367] Kanno, S. and M. Kanda, "Addition of the Camellia Cipher [RFC6367] Kanno, S. and M. Kanda, "Addition of the Camellia Cipher
Suites to Transport Layer Security (TLS)", RFC 6367, DOI Suites to Transport Layer Security (TLS)", RFC 6367,
10.17487/RFC6367, September 2011, DOI 10.17487/RFC6367, September 2011,
<http://www.rfc-editor.org/info/rfc6367>. <http://www.rfc-editor.org/info/rfc6367>.
[RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for [RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for
Transport Layer Security (TLS)", RFC 6655, DOI 10.17487/ Transport Layer Security (TLS)", RFC 6655,
RFC6655, July 2012, DOI 10.17487/RFC6655, July 2012,
<http://www.rfc-editor.org/info/rfc6655>. <http://www.rfc-editor.org/info/rfc6655>.
[RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES- [RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES-
CCM Elliptic Curve Cryptography (ECC) Cipher Suites for CCM Elliptic Curve Cryptography (ECC) Cipher Suites for
TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014, TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014,
<http://www.rfc-editor.org/info/rfc7251>. <http://www.rfc-editor.org/info/rfc7251>.
[SHS] National Institute of Standards and Technology, U.S. [SHS] National Institute of Standards and Technology, U.S.
Department of Commerce, "Secure Hash Standard", NIST FIPS Department of Commerce, "Secure Hash Standard", NIST FIPS
PUB 180-4, March 2012. PUB 180-4, March 2012.
skipping to change at page 77, line 46 skipping to change at page 85, line 51
(ECDSA)", ANSI X9.62, 1998. (ECDSA)", ANSI X9.62, 1998.
12.2. Informative References 12.2. Informative References
[DSS] National Institute of Standards and Technology, U.S. [DSS] National Institute of Standards and Technology, U.S.
Department of Commerce, "Digital Signature Standard, Department of Commerce, "Digital Signature Standard,
version 4", NIST FIPS PUB 186-4, 2013. version 4", NIST FIPS PUB 186-4, 2013.
[ECDSA] American National Standards Institute, "Public Key [ECDSA] American National Standards Institute, "Public Key
Cryptography for the Financial Services Industry: The Cryptography for the Financial Services Industry: The
Elliptic Curve Digital Signature Algorithm (ECDSA)", ANSI Elliptic Curve Digital Signature Algorithm (ECDSA)",
ANS X9.62-2005, November 2005. ANSI ANS X9.62-2005, November 2005.
[FI06] "Bleichenbacher's RSA signature forgery based on [FI06] "Bleichenbacher's RSA signature forgery based on
implementation error", August 2006, <http://www.imc.org/ implementation error", August 2006, <https://www.ietf.org/
ietf-openpgp/mail-archive/msg14307.html>. mail-archive/web/openpgp/current/msg00999.html>.
[GCM] Dworkin, M., "Recommendation for Block Cipher Modes of [GCM] Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Galois/Counter Mode (GCM) and GMAC", NIST Operation: Galois/Counter Mode (GCM) and GMAC",
Special Publication 800-38D, November 2007. NIST Special Publication 800-38D, November 2007.
[I-D.ietf-tls-negotiated-ff-dhe] [I-D.ietf-tls-negotiated-ff-dhe]
Gillmor, D., "Negotiated Finite Field Diffie-Hellman Gillmor, D., "Negotiated Finite Field Diffie-Hellman
Ephemeral Parameters for TLS", draft-ietf-tls-negotiated- Ephemeral Parameters for TLS", draft-ietf-tls-negotiated-
ff-dhe-10 (work in progress), June 2015. ff-dhe-10 (work in progress), June 2015.
[IEEE1363]
IEEE, "Standard Specifications for Public Key
Cryptography", IEEE 1363 , 2000.
[PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate [PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate
Syntax Standard, version 1.5", November 1993. Syntax Standard, version 1.5", November 1993.
[PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message [PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message
Syntax Standard, version 1.5", November 1993. Syntax Standard, version 1.5", November 1993.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC [PSK-FINISHED]
793, DOI 10.17487/RFC0793, September 1981, Cremers, C., Horvat, M., van der Merwe, T., and S. Scott,
"Revision 10: possible attack if client authentication is
allowed during PSK", 2015, <https://www.ietf.org/mail-
archive/web/tls/current/msg18215.html>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>. <http://www.rfc-editor.org/info/rfc793>.
[RFC1948] Bellovin, S., "Defending Against Sequence Number Attacks", [RFC1948] Bellovin, S., "Defending Against Sequence Number Attacks",
RFC 1948, DOI 10.17487/RFC1948, May 1996, RFC 1948, DOI 10.17487/RFC1948, May 1996,
<http://www.rfc-editor.org/info/rfc1948>. <http://www.rfc-editor.org/info/rfc1948>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>. <http://www.rfc-editor.org/info/rfc4086>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key [RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", RFC Ciphersuites for Transport Layer Security (TLS)",
4279, DOI 10.17487/RFC4279, December 2005, RFC 4279, DOI 10.17487/RFC4279, December 2005,
<http://www.rfc-editor.org/info/rfc4279>. <http://www.rfc-editor.org/info/rfc4279>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI [RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
10.17487/RFC4302, December 2005, DOI 10.17487/RFC4302, December 2005,
<http://www.rfc-editor.org/info/rfc4302>. <http://www.rfc-editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
4303, DOI 10.17487/RFC4303, December 2005, RFC 4303, DOI 10.17487/RFC4303, December 2005,
<http://www.rfc-editor.org/info/rfc4303>. <http://www.rfc-editor.org/info/rfc4303>.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, DOI 10.17487/ (TLS) Protocol Version 1.1", RFC 4346,
RFC4346, April 2006, DOI 10.17487/RFC4346, April 2006,
<http://www.rfc-editor.org/info/rfc4346>. <http://www.rfc-editor.org/info/rfc4346>.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., [RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
and T. Wright, "Transport Layer Security (TLS) and T. Wright, "Transport Layer Security (TLS)
Extensions", RFC 4366, DOI 10.17487/RFC4366, April 2006, Extensions", RFC 4366, DOI 10.17487/RFC4366, April 2006,
<http://www.rfc-editor.org/info/rfc4366>. <http://www.rfc-editor.org/info/rfc4366>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, DOI for Transport Layer Security (TLS)", RFC 4492,
10.17487/RFC4492, May 2006, DOI 10.17487/RFC4492, May 2006,
<http://www.rfc-editor.org/info/rfc4492>. <http://www.rfc-editor.org/info/rfc4492>.
[RFC4506] Eisler, M., Ed., "XDR: External Data Representation [RFC4506] Eisler, M., Ed., "XDR: External Data Representation
Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506, May Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506, May
2006, <http://www.rfc-editor.org/info/rfc4506>. 2006, <http://www.rfc-editor.org/info/rfc4506>.
[RFC4507] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 4507, DOI 10.17487/RFC4507, May
2006, <http://www.rfc-editor.org/info/rfc4507>.
[RFC4681] Santesson, S., Medvinsky, A., and J. Ball, "TLS User
Mapping Extension", RFC 4681, DOI 10.17487/RFC4681,
October 2006, <http://www.rfc-editor.org/info/rfc4681>.
[RFC5054] Taylor, D., Wu, T., Mavrogiannopoulos, N., and T. Perrin,
"Using the Secure Remote Password (SRP) Protocol for TLS
Authentication", RFC 5054, DOI 10.17487/RFC5054, November
2007, <http://www.rfc-editor.org/info/rfc5054>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without "Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077, Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <http://www.rfc-editor.org/info/rfc5077>. January 2008, <http://www.rfc-editor.org/info/rfc5077>.
[RFC5081] Mavrogiannopoulos, N., "Using OpenPGP Keys for Transport [RFC5081] Mavrogiannopoulos, N., "Using OpenPGP Keys for Transport
Layer Security (TLS) Authentication", RFC 5081, DOI Layer Security (TLS) Authentication", RFC 5081,
10.17487/RFC5081, November 2007, DOI 10.17487/RFC5081, November 2007,
<http://www.rfc-editor.org/info/rfc5081>. <http://www.rfc-editor.org/info/rfc5081>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<http://www.rfc-editor.org/info/rfc5116>. <http://www.rfc-editor.org/info/rfc5116>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/ (TLS) Protocol Version 1.2", RFC 5246,
RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
"Transport Layer Security (TLS) Renegotiation Indication
Extension", RFC 5746, DOI 10.17487/RFC5746, February 2010,
<http://www.rfc-editor.org/info/rfc5746>.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer (SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May
2010, <http://www.rfc-editor.org/info/rfc5763>. 2010, <http://www.rfc-editor.org/info/rfc5763>.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764,
DOI 10.17487/RFC5764, May 2010,
<http://www.rfc-editor.org/info/rfc5764>.
[RFC5878] Brown, M. and R. Housley, "Transport Layer Security (TLS)
Authorization Extensions", RFC 5878, DOI 10.17487/RFC5878,
May 2010, <http://www.rfc-editor.org/info/rfc5878>.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010, for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<http://www.rfc-editor.org/info/rfc5929>. <http://www.rfc-editor.org/info/rfc5929>.
[RFC6091] Mavrogiannopoulos, N. and D. Gillmor, "Using OpenPGP Keys
for Transport Layer Security (TLS) Authentication",
RFC 6091, DOI 10.17487/RFC6091, February 2011,
<http://www.rfc-editor.org/info/rfc6091>.
[RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer [RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer
(SSL) Version 2.0", RFC 6176, DOI 10.17487/RFC6176, March (SSL) Version 2.0", RFC 6176, DOI 10.17487/RFC6176, March
2011, <http://www.rfc-editor.org/info/rfc6176>. 2011, <http://www.rfc-editor.org/info/rfc6176>.
[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520,
DOI 10.17487/RFC6520, February 2012,
<http://www.rfc-editor.org/info/rfc6520>.
[RFC6961] Pettersen, Y., "The Transport Layer Security (TLS)
Multiple Certificate Status Request Extension", RFC 6961,
DOI 10.17487/RFC6961, June 2013,
<http://www.rfc-editor.org/info/rfc6961>.
[RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate
Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
<http://www.rfc-editor.org/info/rfc6962>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <http://www.rfc-editor.org/info/rfc7250>. June 2014, <http://www.rfc-editor.org/info/rfc7250>.
[RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, DOI [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
10.17487/RFC7465, February 2015, "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <http://www.rfc-editor.org/info/rfc7301>.
[RFC7366] Gutmann, P., "Encrypt-then-MAC for Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", RFC 7366, DOI 10.17487/RFC7366, September 2014,
<http://www.rfc-editor.org/info/rfc7366>.
[RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465,
DOI 10.17487/RFC7465, February 2015,
<http://www.rfc-editor.org/info/rfc7465>. <http://www.rfc-editor.org/info/rfc7465>.
[RFC7568] Barnes, R., Thomson, M., Pironti, A., and A. Langley, [RFC7568] Barnes, R., Thomson, M., Pironti, A., and A. Langley,
"Deprecating Secure Sockets Layer Version 3.0", RFC 7568, "Deprecating Secure Sockets Layer Version 3.0", RFC 7568,
DOI 10.17487/RFC7568, June 2015, DOI 10.17487/RFC7568, June 2015,
<http://www.rfc-editor.org/info/rfc7568>. <http://www.rfc-editor.org/info/rfc7568>.
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A., [RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
Langley, A., and M. Ray, "Transport Layer Security (TLS) Langley, A., and M. Ray, "Transport Layer Security (TLS)
Session Hash and Extended Master Secret Extension", RFC Session Hash and Extended Master Secret Extension",
7627, DOI 10.17487/RFC7627, September 2015, RFC 7627, DOI 10.17487/RFC7627, September 2015,
<http://www.rfc-editor.org/info/rfc7627>. <http://www.rfc-editor.org/info/rfc7627>.
[RFC7685] Langley, A., "A Transport Layer Security (TLS) ClientHello
Padding Extension", RFC 7685, DOI 10.17487/RFC7685,
October 2015, <http://www.rfc-editor.org/info/rfc7685>.
[RSA] Rivest, R., Shamir, A., and L. Adleman, "A Method for [RSA] Rivest, R., Shamir, A., and L. Adleman, "A Method for
Obtaining Digital Signatures and Public-Key Obtaining Digital Signatures and Public-Key
Cryptosystems", Communications of the ACM v. 21, n. 2, pp. Cryptosystems", Communications of the ACM v. 21, n. 2, pp.
120-126., February 1978. 120-126., February 1978.
[SSL2] Netscape Communications Corp., "The SSL Protocol", [SSL2] Netscape Communications Corp., "The SSL Protocol",
February 1995. February 1995.
[SSL3] Freier, A., Karlton, P., and P. Kocher, "The SSL 3.0 [SSL3] Freier, A., Karlton, P., and P. Kocher, "The SSL 3.0
Protocol", November 1996. Protocol", November 1996.
skipping to change at page 81, line 10 skipping to change at page 91, line 10
12.3. URIs 12.3. URIs
[1] mailto:tls@ietf.org [1] mailto:tls@ietf.org
Appendix A. Protocol Data Structures and Constant Values Appendix A. Protocol Data Structures and Constant Values
This section describes protocol types and constants. Values listed This section describes protocol types and constants. Values listed
as _RESERVED were used in previous versions of TLS and are listed as _RESERVED were used in previous versions of TLS and are listed
here for completeness. TLS 1.3 implementations MUST NOT send them here for completeness. TLS 1.3 implementations MUST NOT send them
but may receive them from older TLS implementations. but might receive them from older TLS implementations.
A.1. Record Layer A.1. Record Layer
struct { struct {
uint8 major; uint8 major;
uint8 minor; uint8 minor;
} ProtocolVersion; } ProtocolVersion;
enum { enum {
invalid_RESERVED(0), invalid_RESERVED(0),
change_cipher_spec_RESERVED(20), change_cipher_spec_RESERVED(20),
alert(21), alert(21),
handshake(22), handshake(22),
application_data(23), application_data(23)
early_handshake(25),
(255) (255)
} ContentType; } ContentType;
struct { struct {
ContentType type; ContentType type;
ProtocolVersion record_version = { 3, 1 }; /* TLS v1.x */ ProtocolVersion record_version = { 3, 1 }; /* TLS v1.x */
uint16 length; uint16 length;
opaque fragment[TLSPlaintext.length]; opaque fragment[TLSPlaintext.length];
} TLSPlaintext; } TLSPlaintext;
skipping to change at page 82, line 8 skipping to change at page 92, line 8
ContentType type; ContentType type;
uint8 zeros[length_of_padding]; uint8 zeros[length_of_padding];
} fragment; } fragment;
} TLSCiphertext; } TLSCiphertext;
A.2. Alert Messages A.2. Alert Messages
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
end_of_early_data(1),
unexpected_message(10), /* fatal */ unexpected_message(10), /* fatal */
bad_record_mac(20), /* fatal */ bad_record_mac(20), /* fatal */
decryption_failed_RESERVED(21), /* fatal */ decryption_failed_RESERVED(21), /* fatal */
record_overflow(22), /* fatal */ record_overflow(22), /* fatal */
decompression_failure_RESERVED(30), /* fatal */ decompression_failure_RESERVED(30), /* fatal */
handshake_failure(40), /* fatal */ handshake_failure(40), /* fatal */
no_certificate_RESERVED(41), /* fatal */ no_certificate_RESERVED(41), /* fatal */
bad_certificate(42), bad_certificate(42),
unsupported_certificate(43), unsupported_certificate(43),
certificate_revoked(44), certificate_revoked(44),
skipping to change at page 83, line 19 skipping to change at page 93, line 22
hello_retry_request(6), hello_retry_request(6),
encrypted_extensions(8), encrypted_extensions(8),
certificate(11), certificate(11),
server_key_exchange_RESERVED(12), server_key_exchange_RESERVED(12),
certificate_request(13), certificate_request(13),
server_hello_done_RESERVED(14), server_hello_done_RESERVED(14),
certificate_verify(15), certificate_verify(15),
client_key_exchange_RESERVED(16), client_key_exchange_RESERVED(16),
server_configuration(17), server_configuration(17),
finished(20), finished(20),
key_update(24),
(255) (255)
} HandshakeType; } HandshakeType;
struct { struct {
HandshakeType msg_type; /* handshake type */ HandshakeType msg_type; /* handshake type */
uint24 length; /* bytes in message */ uint24 length; /* bytes in message */
select (HandshakeType) { select (HandshakeType) {
case client_hello: ClientHello; case client_hello: ClientHello;
case server_hello: ServerHello; case server_hello: ServerHello;
case hello_retry_request: HelloRetryRequest; case hello_retry_request: HelloRetryRequest;
case encrypted_extensions: EncryptedExtensions; case encrypted_extensions: EncryptedExtensions;
case certificate_request: CertificateRequest;
case server_configuration:ServerConfiguration; case server_configuration:ServerConfiguration;
case certificate: Certificate; case certificate: Certificate;
case certificate_request: CertificateRequest;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case finished: Finished; case finished: Finished;
case session_ticket: NewSessionTicket; case session_ticket: NewSessionTicket;
case key_update: KeyUpdate;
} body; } body;
} Handshake; } Handshake;
A.3.1. Hello Messages A.3.1. Key Exchange Messages
uint8 CipherSuite[2]; /* Cryptographic suite selector */ struct {
opaque random_bytes[32];
} Random;
enum { null(0), (255) } CompressionMethod; uint8 CipherSuite[2]; /* Cryptographic suite selector */
struct { struct {
ProtocolVersion client_version = { 3, 4 }; /* TLS v1.3 */ ProtocolVersion client_version = { 3, 4 }; /* TLS v1.3 */
Random random; Random random;
SessionID session_id; opaque legacy_session_id<0..32>;
CipherSuite cipher_suites<2..2^16-2>; CipherSuite cipher_suites<2..2^16-2>;
CompressionMethod compression_methods<1..2^8-1>; opaque legacy_compression_methods<1..2^8-1>;
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
} ClientHello; } ClientHello;
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
CipherSuite cipher_suite; CipherSuite cipher_suite;
select (extensions_present) { select (extensions_present) {
case false: case false:
struct {}; struct {};
case true: case true:
skipping to change at page 84, line 40 skipping to change at page 94, line 45
enum { enum {
supported_groups(10), supported_groups(10),
signature_algorithms(13), signature_algorithms(13),
early_data(TBD), early_data(TBD),
pre_shared_key(TBD), pre_shared_key(TBD),
key_share(TBD), key_share(TBD),
(65535) (65535)
} ExtensionType; } ExtensionType;
struct {
NamedGroup group;
opaque key_exchange<1..2^16-1>;
} KeyShareEntry;
struct {
select (role) {
case client:
KeyShareEntry client_shares<4..2^16-1>;
case server:
KeyShareEntry server_share;
}
} KeyShare;
opaque dh_Y<1..2^16-1>;
opaque point <1..2^8-1>;
opaque psk_identity<0..2^16-1>; opaque psk_identity<0..2^16-1>;
struct { struct {
select (Role) { select (Role) {
case client: case client:
psk_identity identities<2..2^16-1>; psk_identity identities<2..2^16-1>;
case server: case server:
psk_identity identity; psk_identity identity;
} }
} PreSharedKeyExtension; } PreSharedKeyExtension;
enum { client_authentication(1), early_data(2),
client_authentication_and_data(3), (255) } EarlyDataType;
struct { struct {
select (Role) { select (Role) {
case client: case client:
opaque configuration_id<1..2^16-1>; opaque configuration_id<1..2^16-1>;
CipherSuite cipher_suite; CipherSuite cipher_suite;
Extension extensions<0..2^16-1>; Extension extensions<0..2^16-1>;
opaque context<0..255>; opaque context<0..255>;
EarlyDataType type;
case server: case server:
struct {}; struct {};
} }
} EarlyDataIndication; } EarlyDataIndication;
struct {
Extension extensions<0..2^16-1>;
} EncryptedExtensions;
enum { (65535) } ConfigurationExtensionType;
struct {
ConfigurationExtensionType extension_type;
opaque extension_data<0..2^16-1>;
} ConfigurationExtension;
struct {
opaque configuration_id<1..2^16-1>;
uint32 expiration_date;
NamedGroup group;
opaque server_key<1..2^16-1>;
EarlyDataType early_data_type;
ConfigurationExtension extensions<0..2^16-1>;
} ServerConfiguration;
A.3.1.1. Signature Algorithm Extension A.3.1.1. Signature Algorithm Extension
enum { enum {
none(0), none(0),
md5_RESERVED(1), md5_RESERVED(1),
sha1(2), sha1(2),
sha224_RESERVED(3), sha224_RESERVED(3),
sha256(4), sha384(5), sha512(6), sha256(4), sha384(5), sha512(6),
(255) (255)
} HashAlgorithm; } HashAlgorithm;
enum { enum {
anonymous_RESERVED(0), anonymous_RESERVED(0),
rsa(1), rsa(1),
dsa(2), dsa(2),
ecdsa(3), ecdsa(3),
rsapss(4), rsapss(4),
eddsa(5),
(255) (255)
} SignatureAlgorithm; } SignatureAlgorithm;
struct { struct {
HashAlgorithm hash; HashAlgorithm hash;
SignatureAlgorithm signature; SignatureAlgorithm signature;
} SignatureAndHashAlgorithm; } SignatureAndHashAlgorithm;
SignatureAndHashAlgorithm SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>; supported_signature_algorithms<2..2^16-2>;
skipping to change at page 86, line 31 skipping to change at page 97, line 4
struct { struct {
HashAlgorithm hash; HashAlgorithm hash;
SignatureAlgorithm signature; SignatureAlgorithm signature;
} SignatureAndHashAlgorithm; } SignatureAndHashAlgorithm;
SignatureAndHashAlgorithm SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>; supported_signature_algorithms<2..2^16-2>;
A.3.1.2. Named Group Extension A.3.1.2. Named Group Extension
enum { enum {
// Elliptic Curve Groups. // Elliptic Curve Groups.
obsolete_RESERVED (1..22), obsolete_RESERVED (1..22),
secp256r1 (23), secp384r1 (24), secp521r1 (25), secp256r1 (23), secp384r1 (24), secp521r1 (25),
// ECDH functions.
ecdh_x25519 (29), ecdh_x448 (30),
// Signature-only curves.
eddsa_ed25519 (31), eddsa_ed448 (32),
// Finite Field Groups. // Finite Field Groups.
ffdhe2048 (256), ffdhe3072 (257), ffdhe4096 (258), ffdhe2048 (256), ffdhe3072 (257), ffdhe4096 (258),
ffdhe6144 (259), ffdhe8192 (260), ffdhe6144 (259), ffdhe8192 (260),
// Reserved Code Points. // Reserved Code Points.
ffdhe_private_use (0x01FC..0x01FF), ffdhe_private_use (0x01FC..0x01FF),
ecdhe_private_use (0xFE00..0xFEFF), ecdhe_private_use (0xFE00..0xFEFF),
obsolete_RESERVED (0xFF01..0xFF02), obsolete_RESERVED (0xFF01..0xFF02),
(0xFFFF) (0xFFFF)
} NamedGroup; } NamedGroup;
skipping to change at page 87, line 15 skipping to change at page 97, line 40
Values within "obsolete_RESERVED" ranges were used in previous Values within "obsolete_RESERVED" ranges were used in previous
versions of TLS and MUST NOT be offered or negotiated by TLS 1.3 versions of TLS and MUST NOT be offered or negotiated by TLS 1.3
implementations. The obsolete curves have various known/theoretical implementations. The obsolete curves have various known/theoretical
weaknesses or have had very little usage, in some cases only due to weaknesses or have had very little usage, in some cases only due to
unintentional server configuration issues. They are no longer unintentional server configuration issues. They are no longer
considered appropriate for general use and should be assumed to be considered appropriate for general use and should be assumed to be
potentially unsafe. The set of curves specified here is sufficient potentially unsafe. The set of curves specified here is sufficient
for interoperability with all currently deployed and properly for interoperability with all currently deployed and properly
configured TLS implementations. configured TLS implementations.
A.3.2. Key Exchange Messages A.3.1.3. Deprecated Extensions
struct { The following extensions are no longer applicable to TLS 1.3,
NamedGroup group; although TLS 1.3 clients MAY send them if they are willing to
opaque key_exchange<1..2^16-1>; negotiate them with prior versions of TLS. TLS 1.3 servers MUST
} KeyShareEntry; ignore these extensions if they are negotiating TLS 1.3:
truncated_hmac [RFC6066], srp [RFC5054], encrypt_then_mac [RFC7366],
extended_master_secret [RFC7627], SessionTicket [RFC5077], and
renegotiation_info [RFC5746].
struct { A.3.2. Server Parameters Messages
select (role) {
case client:
KeyShareEntry client_shares<4..2^16-1>;
case server: struct {
KeyShareEntry server_share; Extension extensions<0..2^16-1>;
} } EncryptedExtensions;
} KeyShare;
opaque dh_Y<1..2^16-1>; opaque DistinguishedName<1..2^16-1>;
opaque point <1..2^8-1>; struct {
opaque certificate_extension_oid<1..2^8-1>;
opaque certificate_extension_values<0..2^16-1>;
} CertificateExtension;
struct {
opaque certificate_request_context<0..2^8-1>;
SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>;
DistinguishedName certificate_authorities<0..2^16-1>;
CertificateExtension certificate_extensions<0..2^16-1>;
} CertificateRequest;
enum { (65535) } ConfigurationExtensionType;
enum { client_authentication(1), early_data(2),
client_authentication_and_data(3), (255) } EarlyDataType;
struct {
ConfigurationExtensionType extension_type;
opaque extension_data<0..2^16-1>;
} ConfigurationExtension;
struct {
opaque configuration_id<1..2^16-1>;
uint32 expiration_date;
KeyShareEntry static_key_share;
EarlyDataType early_data_type;
ConfigurationExtension extensions<0..2^16-1>;
} ServerConfiguration;
A.3.3. Authentication Messages A.3.3. Authentication Messages
opaque ASN1Cert<1..2^24-1>; opaque ASN1Cert<1..2^24-1>;
struct { struct {
opaque certificate_request_context<0..255>;
ASN1Cert certificate_list<0..2^24-1>; ASN1Cert certificate_list<0..2^24-1>;
} Certificate; } Certificate;
opaque DistinguishedName<1..2^16-1>;
struct {
opaque certificate_extension_oid<1..2^8-1>;
opaque certificate_extension_values<0..2^16-1>;
} CertificateExtension;
struct {
SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>;
DistinguishedName certificate_authorities<0..2^16-1>;
CertificateExtension certificate_extensions<0..2^16-1>;
} CertificateRequest;
struct { struct {
digitally-signed struct { digitally-signed struct {
opaque handshake_hash[hash_length]; opaque hashed_data[hash_length];
}; };
} CertificateVerify; } CertificateVerify;
A.3.4. Handshake Finalization Messages
struct { struct {
opaque verify_data[verify_data_length]; opaque verify_data[verify_data_length];
} Finished; } Finished;
A.3.5. Ticket Establishment A.3.4. Ticket Establishment
struct { struct {
uint32 ticket_lifetime_hint; uint32 ticket_lifetime_hint;
opaque ticket<0..2^16-1>; opaque ticket<0..2^16-1>;
} NewSessionTicket; } NewSessionTicket;
A.4. Cipher Suites A.4. Cipher Suites
A cipher suite defines a cipher specification supported in TLS and A cipher suite defines a cipher specification supported in TLS and
negotiated via hello messages in the TLS handshake. Cipher suite negotiated via hello messages in the TLS handshake. Cipher suite
names follow a general naming convention composed of a series of names follow a general naming convention composed of a series of
component algorithm names separated by underscores: component algorithm names separated by underscores:
CipherSuite TLS_KEA_SIGN_WITH_CIPHER_HASH = VALUE; CipherSuite TLS_KEA_SIGN_WITH_CIPHER_HASH = VALUE;
+-----------+-------------------------------------------------+
Component Contents | Component | Contents |
TLS The string "TLS" +-----------+-------------------------------------------------+
KEA The key exchange algorithm | TLS | The string "TLS" |
SIGN The signature algorithm | | |
WITH The string "WITH" | KEA | The key exchange algorithm |
CIPHER The symmetric cipher used for record protection | | |
HASH The hash algorithm used with HKDF | SIGN | The signature algorithm |
VALUE The two byte ID assigned for this cipher suite | | |
| WITH | The string "WITH" |
| | |
| CIPHER | The symmetric cipher used for record protection |
| | |
| HASH | The hash algorithm used with HKDF |
| | |
| VALUE | The two byte ID assigned for this cipher suite |
+-----------+-------------------------------------------------+
The "CIPHER" component commonly has sub-components used to designate The "CIPHER" component commonly has sub-components used to designate
the cipher name, bits, and mode, if applicable. For example, the cipher name, bits, and mode, if applicable. For example,
"AES_256_GCM" represents 256-bit AES in the GCM mode of operation. "AES_256_GCM" represents 256-bit AES in the GCM mode of operation.
Cipher suite names that lack a "HASH" value that are defined for use Cipher suite names that lack a "HASH" value that are defined for use
with TLS 1.2 or later use the SHA-256 hash algorithm by default. with TLS 1.2 or later use the SHA-256 hash algorithm by default.
The primary key exchange algorithm used in TLS is Ephemeral Diffie- The primary key exchange algorithm used in TLS is Ephemeral Diffie-
Hellman [DH]. The finite field based version is denoted "DHE" and Hellman [DH]. The finite field based version is denoted "DHE" and
the elliptic curve based version is denoted "ECDHE". Prior versions the elliptic curve based version is denoted "ECDHE". Prior versions
skipping to change at page 89, line 36 skipping to change at page 101, line 5
supported by TLS 1.3. supported by TLS 1.3.
See the definitions of each cipher suite in its specification See the definitions of each cipher suite in its specification
document for the full details of each combination of algorithms that document for the full details of each combination of algorithms that
is specified. is specified.
The following is a list of standards track server-authenticated (and The following is a list of standards track server-authenticated (and
optionally client-authenticated) cipher suites which are currently optionally client-authenticated) cipher suites which are currently
available in TLS 1.3: available in TLS 1.3:
Cipher Suite Name Value Specification +-------------------------------+----------+------------------------+
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 {0x00,0x9E} [RFC5288] | Cipher Suite Name | Value | Specification |
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 {0x00,0x9F} [RFC5288] +-------------------------------+----------+------------------------+
TLS_DHE_RSA_WITH_AES_128_CCM {0xC0,0x9E} [RFC6655] | TLS_DHE_RSA_WITH_AES_128_GCM_ | {0x00,0x | [RFC5288] |
TLS_DHE_RSA_WITH_AES_256_CCM {0xC0,0x9F} [RFC6655] | SHA256 | 9E} | |
TLS_DHE_RSA_WITH_AES_128_CCM_8 {0xC0,0xA2} [RFC6655] | | | |
TLS_DHE_RSA_WITH_AES_256_CCM_8 {0xC0,0xA3} [RFC6655] | TLS_DHE_RSA_WITH_AES_256_GCM_ | {0x00,0x | [RFC5288] |
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305 {TBD,TBD} [I-D.ietf-tls-chacha20-poly1305] | SHA384 | 9F} | |
TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 {TBD,TBD} [I-D.ietf-tls-chacha20-poly1305] | | | |
TLS_DHE_RSA_WITH_CHACHA20_POLY1305 {TBD,TBD} [I-D.ietf-tls-chacha20-poly1305] | TLS_ECDHE_ECDSA_WITH_AES_128_ | {0xC0,0x | [RFC5289] |
| GCM_SHA256 | 2B} | |
[[TODO: CHACHA20_POLY1305 cipher suite IDs are TBD.]] | | | |
| TLS_ECDHE_ECDSA_WITH_AES_256_ | {0xC0,0x | [RFC5289] |
The following is a list of non-standards track server-authenticated | GCM_SHA384 | 2C} | |
(and optionally client-authenticated) cipher suites which are | | | |
currently available in TLS 1.3: | TLS_ECDHE_RSA_WITH_AES_128_GC | {0xC0,0x | [RFC5289] |
| M_SHA256 | 2F} | |
Cipher Suite Name Value Specification | | | |
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 {0xC0,0x2B} [RFC5289] | TLS_ECDHE_RSA_WITH_AES_256_GC | {0xC0,0x | [RFC5289] |
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 {0xC0,0x2C} [RFC5289] | M_SHA384 | 30} | |
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 {0xC0,0x2F} [RFC5289] | | | |
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 {0xC0,0x30} [RFC5289] | TLS_DHE_RSA_WITH_AES_128_CCM | {0xC0,0x | [RFC6655] |
TLS_ECDHE_ECDSA_WITH_AES_128_CCM {0xC0,0xAC} [RFC7251] | | 9E} | |
TLS_ECDHE_ECDSA_WITH_AES_256_CCM {0xC0,0xAD} [RFC7251] | | | |
TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 {0xC0,0xAE} [RFC7251] | TLS_DHE_RSA_WITH_AES_256_CCM | {0xC0,0x | [RFC6655] |
TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8 {0xC0,0xAF} [RFC7251] | | 9F} | |
TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256 {0xC0,0x52} [RFC6209] | | | |
TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384 {0xC0,0x53} [RFC6209] | TLS_DHE_RSA_WITH_AES_128_CCM_ | {0xC0,0x | [RFC6655] |
TLS_ECDHE_ECDSA_WITH_ARIA_128_GCM_SHA256 {0xC0,0x5C} [RFC6209] | 8 | A2} | |
TLS_ECDHE_ECDSA_WITH_ARIA_256_GCM_SHA384 {0xC0,0x5D} [RFC6209] | | | |
TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256 {0xC0,0x60} [RFC6209] | TLS_DHE_RSA_WITH_AES_256_CCM_ | {0xC0,0x | [RFC6655] |
TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384 {0xC0,0x61} [RFC6209] | 8 | A3} | |
TLS_DHE_RSA_WITH_CAMELLIA_128_GCM_SHA256 {0xC0,0x7C} [RFC6367] | | | |
TLS_DHE_RSA_WITH_CAMELLIA_256_GCM_SHA384 {0xC0,0x7D} [RFC6367] | TLS_ECDHE_RSA_WITH_CHACHA20_P | {TBD,TBD | [I-D.ietf-tls-chacha20 |
TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_GCM_SHA256 {0xC0,0x86} [RFC6367] | OLY1305_SHA256 | } | -poly1305] |
TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_GCM_SHA384 {0xC0,0x87} [RFC6367] | | | |
TLS_ECDHE_RSA_WITH_CAMELLIA_128_GCM_SHA256 {0xC0,0x8A} [RFC6367] | TLS_ECDHE_ECDSA_WITH_CHACHA20 | {TBD,TBD | [I-D.ietf-tls-chacha20 |
TLS_ECDHE_RSA_WITH_CAMELLIA_256_GCM_SHA384 {0xC0,0x8B} [RFC6367] | _POLY1305_SHA256 | } | -poly1305] |
| | | |
| TLS_DHE_RSA_WITH_CHACHA20_POL | {TBD,TBD | [I-D.ietf-tls-chacha20 |
| Y1305_SHA256 | } | -poly1305] |
+-------------------------------+----------+------------------------+
ECDHE AES GCM is not yet standards track, however it is already [[TODO: CHACHA20_POLY1305_SHA256 cipher suite IDs are TBD.]]
widely deployed.
Note: In the case of the CCM mode of AES, two variations exist: Note: ECDHE AES GCM was not yet standards track prior to the
"CCM_8" which uses an 8-bit authentication tag and "CCM" which uses a publication of this specification. This document promotes it to
16-bit authentication tag. Both use the default hash, SHA-256. Standards Track.
All cipher suites in this section are specified for use with both TLS All cipher suites in this section are specified for use with both TLS
1.2 and TLS 1.3, as well as the corresponding versions of DTLS. (see 1.2 and TLS 1.3, as well as the corresponding versions of DTLS. (see
Appendix C) Appendix C)
New cipher suite values are assigned by IANA as described in New cipher suite values are assigned by IANA as described in
Section 11. Section 11.
A.4.1. Unauthenticated Operation A.4.1. Unauthenticated Operation
Previous versions of TLS offered explicitly unauthenticated cipher Previous versions of TLS offered explicitly unauthenticated cipher
suites base on anonymous Diffie-Hellman. These cipher suites have suites based on anonymous Diffie-Hellman. These cipher suites have
been deprecated in TLS 1.3. However, it is still possible to been deprecated in TLS 1.3. However, it is still possible to
negotiate cipher suites that do not provide verifiable server negotiate cipher suites that do not provide verifiable server
authentication by serveral methods, including: authentication by several methods, including:
- Raw public keys [RFC7250]. - Raw public keys [RFC7250].
- Using a public key contained in a certificate but without - Using a public key contained in a certificate but without
validation of the certificate chain or any of its contents. validation of the certificate chain or any of its contents.
Either technique used alone is are vulnerable to man-in-the-middle Either technique used alone is are vulnerable to man-in-the-middle
attacks and therefore unsafe for general use. However, it is also attacks and therefore unsafe for general use. However, it is also
possible to bind such connections to an external authentication possible to bind such connections to an external authentication
mechanism via out-of-band validation of the server's public key, mechanism via out-of-band validation of the server's public key,
skipping to change at page 91, line 51 skipping to change at page 103, line 34
} SecurityParameters; } SecurityParameters;
A.6. Changes to RFC 4492 A.6. Changes to RFC 4492
RFC 4492 [RFC4492] adds Elliptic Curve cipher suites to TLS. This RFC 4492 [RFC4492] adds Elliptic Curve cipher suites to TLS. This
document changes some of the structures used in that document. This document changes some of the structures used in that document. This
section details the required changes for implementors of both RFC section details the required changes for implementors of both RFC
4492 and TLS 1.2. Implementors of TLS 1.2 who are not implementing 4492 and TLS 1.2. Implementors of TLS 1.2 who are not implementing
RFC 4492 do not need to read this section. RFC 4492 do not need to read this section.
This document adds a "signature_algorithm" field to the digitally- This document adds an "algorithm" field to the digitally-signed
signed element in order to identify the signature and digest element in order to identify the signature and digest algorithms used
algorithms used to create a signature. This change applies to to create a signature. This change applies to digital signatures
digital signatures formed using ECDSA as well, thus allowing ECDSA formed using ECDSA as well, thus allowing ECDSA signatures to be used
signatures to be used with digest algorithms other than SHA-1, with digest algorithms other than SHA-1, provided such use is
provided such use is compatible with the certificate and any compatible with the certificate and any restrictions imposed by
restrictions imposed by future revisions of [RFC5280]. future revisions of [RFC5280].
As described in Section 6.3.4, the restrictions on the signature As described in Section 6.3.4.1.1, the restrictions on the signature
algorithms used to sign certificates are no longer tied to the cipher algorithms used to sign certificates are no longer tied to the cipher
suite. Thus, the restrictions on the algorithm used to sign suite. Thus, the restrictions on the algorithm used to sign
certificates specified in Sections 2 and 3 of RFC 4492 are also certificates specified in Sections 2 and 3 of RFC 4492 are also
relaxed. As in this document, the restrictions on the keys in the relaxed. As in this document, the restrictions on the keys in the
end-entity certificate remain. end-entity certificate remain.
Appendix B. Implementation Notes Appendix B. Implementation Notes
The TLS protocol cannot prevent many common security mistakes. This The TLS protocol cannot prevent many common security mistakes. This
section provides several recommendations to assist implementors. section provides several recommendations to assist implementors.
skipping to change at page 93, line 10 skipping to change at page 104, line 41
messages. Certificates should always be verified to ensure proper messages. Certificates should always be verified to ensure proper
signing by a trusted Certificate Authority (CA). The selection and signing by a trusted Certificate Authority (CA). The selection and
addition of trusted CAs should be done very carefully. Users should addition of trusted CAs should be done very carefully. Users should
be able to view information about the certificate and root CA. be able to view information about the certificate and root CA.
B.3. Cipher Suite Support B.3. Cipher Suite Support
TLS supports a range of key sizes and security levels, including some TLS supports a range of key sizes and security levels, including some
that provide no or minimal security. A proper implementation will that provide no or minimal security. A proper implementation will
probably not support many cipher suites. Applications SHOULD also probably not support many cipher suites. Applications SHOULD also
enforce minimum and maximum key sizes. For example, certificate enforce minimum and maximum key sizes. For example, certification
chains containing keys or signatures weaker than 2048-bit RSA or paths containing keys or signatures weaker than 2048-bit RSA or
224-bit ECDSA are not appropriate for secure applications. See also 224-bit ECDSA are not appropriate for secure applications. See also
Appendix C.3. Appendix C.3.
B.4. Implementation Pitfalls B.4. Implementation Pitfalls
Implementation experience has shown that certain parts of earlier TLS Implementation experience has shown that certain parts of earlier TLS
specifications are not easy to understand, and have been a source of specifications are not easy to understand, and have been a source of
interoperability and security problems. Many of these areas have interoperability and security problems. Many of these areas have
been clarified in this document, but this appendix contains a short been clarified in this document, but this appendix contains a short
list of the most important things that require special attention from list of the most important things that require special attention from
skipping to change at page 93, line 37 skipping to change at page 105, line 20
multiple TLS records (see Section 5.2.1)? Including corner cases multiple TLS records (see Section 5.2.1)? Including corner cases
like a ClientHello that is split to several small fragments? Do like a ClientHello that is split to several small fragments? Do
you fragment handshake messages that exceed the maximum fragment you fragment handshake messages that exceed the maximum fragment
size? In particular, the certificate and certificate request size? In particular, the certificate and certificate request
handshake messages can be large enough to require fragmentation. handshake messages can be large enough to require fragmentation.
- Do you ignore the TLS record layer version number in all TLS - Do you ignore the TLS record layer version number in all TLS
records? (see Appendix C) records? (see Appendix C)
- Have you ensured that all support for SSL, RC4, EXPORT ciphers, - Have you ensured that all support for SSL, RC4, EXPORT ciphers,
and MD5 (via the Signature Algorithms extension) is completely and MD5 (via the "signature_algorithm" extension) is completely
removed from all possible configurations that support TLS 1.3 or removed from all possible configurations that support TLS 1.3 or
later, and that attempts to use these obsolete capabilities fail later, and that attempts to use these obsolete capabilities fail
correctly? (see Appendix C) correctly? (see Appendix C)
- Do you handle TLS extensions in ClientHello correctly, including - Do you handle TLS extensions in ClientHello correctly, including
omitting the extensions field completely? omitting the extensions field completely?
- When the server has requested a client certificate, but no - When the server has requested a client certificate, but no
suitable certificate is available, do you correctly send an empty suitable certificate is available, do you correctly send an empty
Certificate message, instead of omitting the whole message (see Certificate message, instead of omitting the whole message (see
Section 6.3.9)? Section 6.3.4.1.2)?
- When processing the plaintext fragment produced by AEAD-Decrypt - When processing the plaintext fragment produced by AEAD-Decrypt
and scanning from the end for the ContentType, do you avoid and scanning from the end for the ContentType, do you avoid
scanning past the start of the cleartext in the event that the scanning past the start of the cleartext in the event that the
peer has sent a malformed plaintext of all-zeros? peer has sent a malformed plaintext of all-zeros?
Cryptographic details: Cryptographic details:
- What countermeasures do you use to prevent timing attacks against - What countermeasures do you use to prevent timing attacks against
RSA signing operations [TIMING]? RSA signing operations [TIMING]?
- When verifying RSA signatures, do you accept both NULL and missing - When verifying RSA signatures, do you accept both NULL and missing
parameters (see Section 4.9)? Do you verify that the RSA padding parameters (see Section 4.8)? Do you verify that the RSA padding
doesn't have additional data after the hash value? [FI06] doesn't have additional data after the hash value? [FI06]
- When using Diffie-Hellman key exchange, do you correctly strip - When using Diffie-Hellman key exchange, do you correctly strip
leading zero bytes from the negotiated key (see Section 7.2.2)? leading zero bytes from the negotiated key (see Section 7.3.2)?
- Does your TLS client check that the Diffie-Hellman parameters sent - Does your TLS client check that the Diffie-Hellman parameters sent
by the server are acceptable (see Appendix D.1.1.1)? by the server are acceptable (see Appendix D.1.1.1)?
- Do you use a strong and, most importantly, properly seeded random - Do you use a strong and, most importantly, properly seeded random
number generator (see Appendix B.1) Diffie-Hellman private values, number generator (see Appendix B.1) Diffie-Hellman private values,
the ECDSA "k" parameter, and other security-critical values? the ECDSA "k" parameter, and other security-critical values?
Appendix C. Backward Compatibility Appendix C. Backward Compatibility
skipping to change at page 94, line 50 skipping to change at page 106, line 33
and its value MUST be ignored by all implementations. Version and its value MUST be ignored by all implementations. Version
negotiation is performed using only the handshake versions. negotiation is performed using only the handshake versions.
(ClientHello.client_version & ServerHello.server_version) In order to (ClientHello.client_version & ServerHello.server_version) In order to
maximize interoperability with older endpoints, implementations that maximize interoperability with older endpoints, implementations that
negotiate the use of TLS 1.0-1.2 SHOULD set the record layer version negotiate the use of TLS 1.0-1.2 SHOULD set the record layer version
number to the negotiated version for the ServerHello and all records number to the negotiated version for the ServerHello and all records
thereafter. thereafter.
For maximum compatibility with previously non-standard behavior and For maximum compatibility with previously non-standard behavior and
misconfigured deployments, all implementations SHOULD support misconfigured deployments, all implementations SHOULD support
validation of certificate chains based on the expectations in this validation of certification paths based on the expectations in this
document, even when handling prior TLS versions' handshakes. (see document, even when handling prior TLS versions' handshakes. (see
Section 6.3.4) Section 6.3.4.1.1)
C.1. Negotiating with an older server C.1. Negotiating with an older server
A TLS 1.3 client who wishes to negotiate with such older servers will A TLS 1.3 client who wishes to negotiate with such older servers will
send a normal TLS 1.3 ClientHello containing { 3, 4 } (TLS 1.3) in send a normal TLS 1.3 ClientHello containing { 3, 4 } (TLS 1.3) in
ClientHello.client_version. If the server does not support this ClientHello.client_version. If the server does not support this
version it will respond with a ServerHello containing an older version it will respond with a ServerHello containing an older
version number. If the client agrees to use this version, the version number. If the client agrees to use this version, the
negotiation will proceed as appropriate for the negotiated protocol. negotiation will proceed as appropriate for the negotiated protocol.
A client resuming a session SHOULD initiate the connection using the A client resuming a session SHOULD initiate the connection using the
skipping to change at page 97, line 38 skipping to change at page 109, line 24
leading to an acceptable certificate authority. Similarly, leading to an acceptable certificate authority. Similarly,
authenticated clients must supply an acceptable certificate to the authenticated clients must supply an acceptable certificate to the
server. Each party is responsible for verifying that the other's server. Each party is responsible for verifying that the other's
certificate is valid and has not expired or been revoked. certificate is valid and has not expired or been revoked.
[[TODO: Rewrite this because the master_secret is not used this way [[TODO: Rewrite this because the master_secret is not used this way
any more after Hugo's changes.]] The general goal of the key exchange any more after Hugo's changes.]] The general goal of the key exchange
process is to create a master_secret known to the communicating process is to create a master_secret known to the communicating
parties and not to attackers (see Section 7.1). The master_secret is parties and not to attackers (see Section 7.1). The master_secret is
required to generate the Finished messages and record protection keys required to generate the Finished messages and record protection keys
(see Section 6.3.8 and Section 7.2). By sending a correct Finished (see Section 6.3.4.3 and Section 7.3). By sending a correct Finished
message, parties thus prove that they know the correct master_secret. message, parties thus prove that they know the correct master_secret.
D.1.1.1. Diffie-Hellman Key Exchange with Authentication D.1.1.1. Diffie-Hellman Key Exchange with Authentication
When Diffie-Hellman key exchange is used, the client and server use When Diffie-Hellman key exchange is used, the client and server use
the KeyShare extension to send temporary Diffie-Hellman parameters. the "key_share" extension to send temporary Diffie-Hellman
The signature in the certificate verify message (if present) covers parameters. The signature in the certificate verify message (if
the entire handshake up to that point and thus attests the present) covers the entire handshake up to that point and thus
certificate holder's desire to use the the ephemeral DHE keys. attests the certificate holder's desire to use the the ephemeral DHE
keys.
Peers SHOULD validate each other's public key Y (dh_Ys offered by the Peers SHOULD validate each other's public key Y (dh_Ys offered by the
server or DH_Yc offered by the client) by ensuring that 1 < Y < p-1. server or DH_Yc offered by the client) by ensuring that 1 < Y < p-1.
This simple check ensures that the remote peer is properly behaved This simple check ensures that the remote peer is properly behaved
and isn't forcing the local system into a small subgroup. and isn't forcing the local system into a small subgroup.
Additionally, using a fresh key for each handshake provides Perfect Additionally, using a fresh key for each handshake provides Perfect
Forward Secrecy. Implementations SHOULD generate a new X for each Forward Secrecy. Implementations SHOULD generate a new X for each
handshake when using DHE cipher suites. handshake when using DHE cipher suites.
D.1.2. Version Rollback Attacks D.1.2. Version Rollback Attacks
Because TLS includes substantial improvements over SSL Version 2.0, Because TLS includes substantial improvements over SSL Version 2.0,
skipping to change at page 99, line 15 skipping to change at page 110, line 49
detected. Since sequence numbers are 64 bits long, they should never detected. Since sequence numbers are 64 bits long, they should never
overflow. Messages from one party cannot be inserted into the overflow. Messages from one party cannot be inserted into the
other's output, since they use independent keys. other's output, since they use independent keys.
D.3. Denial of Service D.3. Denial of Service
TLS is susceptible to a number of denial-of-service (DoS) attacks. TLS is susceptible to a number of denial-of-service (DoS) attacks.
In particular, an attacker who initiates a large number of TCP In particular, an attacker who initiates a large number of TCP
connections can cause a server to consume large amounts of CPU doing connections can cause a server to consume large amounts of CPU doing
asymmetric crypto operations. However, because TLS is generally used asymmetric crypto operations. However, because TLS is generally used
over TCP, it is difficult for the attacker to hide his point of over TCP, it is difficult for the attacker to hide their point of
origin if proper TCP SYN randomization is used [RFC1948] by the TCP origin if proper TCP SYN randomization is used [RFC1948] by the TCP
stack. stack.
Because TLS runs over TCP, it is also susceptible to a number of DoS Because TLS runs over TCP, it is also susceptible to a number of DoS
attacks on individual connections. In particular, attackers can attacks on individual connections. In particular, attackers can
forge RSTs, thereby terminating connections, or forge partial TLS forge RSTs, thereby terminating connections, or forge partial TLS
records, thereby causing the connection to stall. These attacks records, thereby causing the connection to stall. These attacks
cannot in general be defended against by a TCP-using protocol. cannot in general be defended against by a TCP-using protocol.
Implementors or users who are concerned with this class of attack Implementors or users who are concerned with this class of attack
should use IPsec AH [RFC4302] or ESP [RFC4303]. should use IPsec AH [RFC4302] or ESP [RFC4303].
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The discussion list for the IETF TLS working group is located at the The discussion list for the IETF TLS working group is located at the
e-mail address tls@ietf.org [1]. Information on the group and e-mail address tls@ietf.org [1]. Information on the group and
information on how to subscribe to the list is at information on how to subscribe to the list is at
https://www1.ietf.org/mailman/listinfo/tls https://www1.ietf.org/mailman/listinfo/tls
Archives of the list can be found at: https://www.ietf.org/mail- Archives of the list can be found at: https://www.ietf.org/mail-
archive/web/tls/current/index.html archive/web/tls/current/index.html
Appendix F. Contributors Appendix F. Contributors
Martin Abadi - Martin Abadi
University of California, Santa Cruz University of California, Santa Cruz
abadi@cs.ucsc.edu abadi@cs.ucsc.edu
Christopher Allen (co-editor of TLS 1.0) - Christopher Allen (co-editor of TLS 1.0)
Alacrity Ventures Alacrity Ventures
ChristopherA@AlacrityManagement.com ChristopherA@AlacrityManagement.com
Steven M. Bellovin - Steven M. Bellovin
Columbia University Columbia University
smb@cs.columbia.edu smb@cs.columbia.edu
Benjamin Beurdouche - Benjamin Beurdouche
- Karthikeyan Bhargavan (co-author of [RFC7627])
INRIA
karthikeyan.bhargavan@inria.fr
Karthikeyan Bhargavan (co-author of [RFC7627]) - Simon Blake-Wilson (co-author of [RFC4492])
INRIA BCI
karthikeyan.bhargavan@inria.fr sblakewilson@bcisse.com
Simon Blake-Wilson (co-author of [RFC4492]) - Nelson Bolyard (co-author of [RFC4492])
BCI Sun Microsystems, Inc.
sblakewilson@bcisse.com nelson@bolyard.com
Nelson Bolyard - Ran Canetti
Sun Microsystems, Inc. IBM
nelson@bolyard.com (co-author of [RFC4492]) canetti@watson.ibm.com
Ran Canetti - Pete Chown
IBM Skygate Technology Ltd
canetti@watson.ibm.com pc@skygate.co.uk
Pete Chown - Antoine Delignat-Lavaud (co-author of [RFC7627])
Skygate Technology Ltd INRIA
pc@skygate.co.uk antoine.delignat-lavaud@inria.fr
Antoine Delignat-Lavaud (co-author of [RFC7627]) - Tim Dierks (co-editor of TLS 1.0, 1.1, and 1.2)
INRIA Independent
antoine.delignat-lavaud@inria.fr tim@dierks.org
Tim Dierks (co-editor of TLS 1.0, 1.1, and 1.2) - Taher Elgamal
Independent Securify
tim@dierks.org taher@securify.com
Taher Elgamal - Pasi Eronen
Securify Nokia
taher@securify.com pasi.eronen@nokia.com
Pasi Eronen
Nokia
pasi.eronen@nokia.com
Anil Gangolli - Cedric Fournet
anil@busybuddha.org Microsoft
fournet@microsoft.com
David M. Garrett - Anil Gangolli
anil@busybuddha.org
Vipul Gupta (co-author of [RFC4492]) - David M. Garrett
Sun Microsystems Laboratories
vipul.gupta@sun.com
Chris Hawk (co-author of [RFC4492]) - Vipul Gupta (co-author of [RFC4492])
Corriente Networks LLC Sun Microsystems Laboratories
chris@corriente.net vipul.gupta@sun.com
Kipp Hickman - Chris Hawk (co-author of [RFC4492])
Corriente Networks LLC
chris@corriente.net
Alfred Hoenes - Kipp Hickman
David Hopwood - Alfred Hoenes
Independent Consultant
david.hopwood@blueyonder.co.uk
Daniel Kahn Gillmor - David Hopwood
ACLU Independent Consultant
dkg@fifthhorseman.net david.hopwood@blueyonder.co.uk
Phil Karlton (co-author of SSL 3.0) - Daniel Kahn Gillmor
ACLU
dkg@fifthhorseman.net
Paul Kocher (co-author of SSL 3.0) - Phil Karlton (co-author of SSL 3.0)
Cryptography Research
paul@cryptography.com
Hugo Krawczyk - Paul Kocher (co-author of SSL 3.0)
IBM Cryptography Research
hugo@ee.technion.ac.il paul@cryptography.com
Adam Langley (co-author of [RFC7627]) - Hugo Krawczyk
Google IBM
agl@google.com hugo@ee.technion.ac.il
Ilari Liusvaara - Adam Langley (co-author of [RFC7627])
ilari.liusvaara@elisanet.fi Google
agl@google.com
Jan Mikkelsen - Ilari Liusvaara
Transactionware Independent
janm@transactionware.com ilariliusvaara@welho.com
Bodo Moeller (co-author of [RFC4492]) - Jan Mikkelsen
Google Transactionware
bodo@openssl.org janm@transactionware.com
Erik Nygren - Bodo Moeller (co-author of [RFC4492])
Akamai Technologies Google
erik+ietf@nygren.org bodo@openssl.org
Magnus Nystrom - Erik Nygren
RSA Security Akamai Technologies
magnus@rsasecurity.com erik+ietf@nygren.org
Alfredo Pironti (co-author of [RFC7627]) - Magnus Nystrom
INRIA RSA Security
alfredo.pironti@inria.fr magnus@rsasecurity.com
Andrei Popov - Alfredo Pironti (co-author of [RFC7627])
Microsoft INRIA
andrei.popov@microsoft.com alfredo.pironti@inria.fr
Marsh Ray (co-author of [RFC7627]) - Andrei Popov
Microsoft Microsoft
maray@microsoft.com andrei.popov@microsoft.com
Robert Relyea - Marsh Ray (co-author of [RFC7627])
Netscape Communications Microsoft
relyea@netscape.com maray@microsoft.com
Jim Roskind - Robert Relyea
Netscape Communications Netscape Communications
jar@netscape.com relyea@netscape.com
Michael Sabin - Jim Roskind
Netscape Communications
jar@netscape.com
Dan Simon - Michael Sabin
Microsoft, Inc.
dansimon@microsoft.com
Bjoern Tackmann - Dan Simon
University of California, San Diego Microsoft, Inc.
btackmann@eng.ucsd.edu dansimon@microsoft.com
Martin Thomson - Bjoern Tackmann
Mozilla University of California, San Diego
mt@mozilla.com btackmann@eng.ucsd.edu
Tom Weinstein
Hoeteck Wee - Martin Thomson
Ecole Normale Superieure, Paris Mozilla
hoeteck@alum.mit.edu mt@mozilla.com
Tim Wright - Tom Weinstein
Vodafone
timothy.wright@vodafone.com - Hoeteck Wee
Ecole Normale Superieure, Paris
hoeteck@alum.mit.edu
- Tim Wright
Vodafone
timothy.wright@vodafone.com
Author's Address Author's Address
Eric Rescorla Eric Rescorla
RTFM, Inc. RTFM, Inc.
EMail: ekr@rtfm.com EMail: ekr@rtfm.com
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