draft-ietf-kitten-tls-channel-bindings-for-tls13-03.txt   draft-ietf-kitten-tls-channel-bindings-for-tls13-04.txt 
Transport Layer Security S. Whited Transport Layer Security S. Whited
Internet-Draft 15 March 2021 Internet-Draft May 25, 2021
Updates: 5802, 8446 (if approved) Updates: 5802,5929,8446 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: 16 September 2021 Expires: November 26, 2021
Channel Bindings for TLS 1.3 Channel Bindings for TLS 1.3
draft-ietf-kitten-tls-channel-bindings-for-tls13-03 draft-ietf-kitten-tls-channel-bindings-for-tls13-04
Abstract Abstract
This document defines a channel binding type, tls-exporter, that is This document defines a channel binding type, tls-exporter, that is
compatible with TLS 1.3 in accordance with RFC 5056, On Channel compatible with TLS 1.3 in accordance with RFC 5056, On Channel
Binding. Binding. Furthermore it updates the "default" channel binding to the
new binding for versions of TLS greater than 1.2. This document
updates [RFC5802], [RFC5929], and [RFC8446].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Terminology . . . . . . . . . . . . . . . 2
2. The 'tls-exporter' Channel Binding Type . . . . . . . . . . . 2
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3
3.1. Use with Legacy TLS . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4.1. Registration of Channel Binding Type . . . . . . . . . . 3
4.2. Registration of Channel Binding TLS Exporter Label . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1.
The "unique" channel binding types defined in [RFC5929] were found to The "unique" channel binding types defined in [RFC5929] were found to
be vulnerable to the "triple handshake vulnerability" be vulnerable to the "triple handshake vulnerability"
[TRIPLE-HANDSHAKE] without the extended master secret extension [TRIPLE-HANDSHAKE] without the extended master secret extension
defined in [RFC7627]. Because of this they were not defined for TLS defined in [RFC7627]. Because of this they were not defined for TLS
1.3 (see [RFC8446] section C.5). To facilitate channel binding with 1.3 (see [RFC8446] section C.5). To facilitate channel binding with
TLS 1.3, a new channel binding type is needed. TLS 1.3, a new channel binding type is needed.
1.1. Conventions and Terminology 1.1.
Throughout this document the acronym "EKM" is used to refer to Throughout this document the acronym "EKM" is used to refer to
Exported Keying Material as defined in [RFC5705]. Exported Keying Material as defined in [RFC5705].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. The 'tls-exporter' Channel Binding Type 2.
Channel binding mechanisms are not useful until TLS implementations Channel binding mechanisms are not useful until TLS implementations
expose the required data. To facilitate this, "tls-exporter" uses expose the required data. To facilitate this, "tls-exporter" uses
exported keying material (EKM) which is already widely exposed by TLS exported keying material (EKM) which is already widely exposed by TLS
implementations. The EKM is obtained using the keying material implementations. The EKM is obtained using the keying material
exporters for TLS as defined in [RFC5705] and [RFC8446] section 7.5 exporters for TLS as defined in [RFC5705] and [RFC8446] section 7.5
by supplying the following inputs: by supplying the following inputs:
Label: The ASCII string "EXPORTER-Channel-Binding" with no In previous versions of TLS the "tls-unique" channel binding type was
terminating NUL. defined as the default channel binding if no mechanism was defined
for negotiating a different channel binding. Because "tls-unique" is
Context value: Empty context value. not defined for TLS 1.3, the default channel binding mechanism for
TLS versions 1.3 and greater
Length: 32 bytes. be "tls-exporter".
3. Security Considerations 3.
Channel bindings do not leak secret information about the channel and Channel bindings do not leak secret information about the channel and
are considered public. Implementations MUST NOT use the channel are considered public. Implementations MUST NOT use the channel
binding to protect secret information. binding to protect secret information.
The Security Considerations sections of [RFC5056], [RFC5705], and The Security Considerations sections of [RFC5056], [RFC5705], and
[RFC8446] apply to this document. [RFC8446] apply to this document.
3.1. Use with Legacy TLS 3.1.
While it is possible to use this channel binding mechanism with TLS While it is possible to use this channel binding mechanism with TLS
versions below 1.3, extra precaution must be taken to ensure that the versions below 1.3, extra precaution must be taken to ensure that the
chosen cipher suites always result in unique master secrets. For chosen cipher suites always result in unique master secrets. For
more information see the Security Considerations section of more information see the Security Considerations section of
[RFC5705]. [RFC5705].
When TLS renegotiation is enabled the "tls-exporter" channel binding When TLS renegotiation is enabled the "tls-exporter" channel binding
type is not defined and implementations MUST NOT support it. type is not defined and implementations
support it.
In general, users wishing to take advantage of channel binding should In general, users wishing to take advantage of channel binding should
upgrade to TLS 1.3 or later. upgrade to TLS 1.3 or later.
4. IANA Considerations The derived data
4.1. Registration of Channel Binding Type
This document adds the following registration in the "Channel-Binding
Types" registry:
Subject: Registration of channel binding tls-exporter
Channel binding unique prefix: tls-exporter
Channel binding type: unique
Channel type: TLS [RFC8446]
Published specification: draft-ietf-kitten-tls-channel-bindings-for-
tls13-03
Channel binding is secret: no
Description: The EKM value obtained from the current TLS connection.
Intended usage: COMMON be used for any purpose other than channel bindings as described in
Person and email address to contact for further information: Sam [RFC5056].
Whited <sam@samwhited.com>.
Owner/Change controller name and email address: IESG. 4.
Expert reviewer name and contact information: IETF KITTEN or TLS WG 4.1.
(kitten@ietf.org or tls@ietf.org, failing that, ietf@ietf.org).
Note: See the published specification for advice on the This document adds the following registration in the "Channel-Binding
applicability of this channel binding type. Types" registry:
4.2. Registration of Channel Binding TLS Exporter Label 4.2.
This document adds the following registration in the "TLS Exporter This document adds the following registration in the "TLS Exporter
Labels" registry: Labels" registry:
Value: EXPORTER-Channel-Binding
DTLS-OK: Y
Recommended: N
Reference: This document
5. References 5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5056] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
<https://www.rfc-editor.org/info/rfc5056>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <https://www.rfc-editor.org/info/rfc5705>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
5.2. Informative References
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<https://www.rfc-editor.org/info/rfc5929>.
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
Langley, A., and M. Ray, "Transport Layer Security (TLS)
Session Hash and Extended Master Secret Extension",
RFC 7627, DOI 10.17487/RFC7627, September 2015,
<https://www.rfc-editor.org/info/rfc7627>.
[TRIPLE-HANDSHAKE]
Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti,
A., and P. Strub, "Password Storage", March 2014,
<https://www.mitls.org/pages/attacks/3SHAKE>.
Author's Address Author's Address
Sam Whited Sam Whited
Atlanta, GA Atlanta GA
United States of America USA
Email: sam@samwhited.com Email: sam@samwhited.com
URI: https://blog.samwhited.com/ URI: https://blog.samwhited.com/
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