draft-ietf-kitten-tls-channel-bindings-for-tls13-08.txt   draft-ietf-kitten-tls-channel-bindings-for-tls13-09.txt 
Transport Layer Security S. Whited Transport Layer Security S. Whited
Internet-Draft 26 May 2021 Internet-Draft 1 October 2021
Updates: 5801, 5802, 5929, 8446 (if approved) Updates: 5801, 5802, 5929, 8446 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: 27 November 2021 Expires: 4 April 2022
Channel Bindings for TLS 1.3 Channel Bindings for TLS 1.3
draft-ietf-kitten-tls-channel-bindings-for-tls13-08 draft-ietf-kitten-tls-channel-bindings-for-tls13-09
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. Furthermore it updates the "default" channel binding to the Binding. Furthermore it updates the "default" channel binding to the
new binding for versions of TLS greater than 1.2. This document new binding for versions of TLS greater than 1.2. This document
updates RFC5801, RFC5802, RFC5929, and RFC8446. updates RFC5801, RFC5802, RFC5929, and RFC8446.
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
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 27 November 2021. This Internet-Draft will expire on 4 April 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Terminology . . . . . . . . . . . . . . . 2 1.1. Conventions and Terminology . . . . . . . . . . . . . . . 2
2. The 'tls-exporter' Channel Binding Type . . . . . . . . . . . 2 2. The 'tls-exporter' Channel Binding Type . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3
3.1. Use with Legacy TLS . . . . . . . . . . . . . . . . . . . 3 3.1. Use with Legacy TLS . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. Registration of Channel Binding Type . . . . . . . . . . 3 4.1. Registration of Channel Binding Type . . . . . . . . . . 4
4.2. Registration of Channel Binding TLS Exporter Label . . . 4 4.2. Registration of Channel Binding TLS Exporter Label . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 4 5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 5 5.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
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]. While TLS 1.3 uses a complete transcript hash
1.3 (see [RFC8446] section C.5). To facilitate channel binding with akin to the extended master secret procedures, the safety of channel
TLS 1.3, a new channel binding type is needed. bindings with TLS 1.3 was not analyzed as part of the core protocol
work, and so the specification of channel bindings for TLS 1.3 was
deferred. [RFC8446] section C.5 notes the lack of channel bindings
for TLS 1.3; as this document defines such channel bindings, it
updates [RFC8446] to note that this gap has been filled.
Furthermore, this document updates [RFC5929] by adding an additional
unique channel binding type that replaces some usage of "tls-unique".
1.1. Conventions and Terminology 1.1. Conventions and Terminology
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
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Length: 32 bytes. Length: 32 bytes.
SCRAM [RFC5802] and GSS-API over SASL [RFC5801] define "tls-unique" SCRAM [RFC5802] and GSS-API over SASL [RFC5801] define "tls-unique"
as the default channel binding to use over TLS. As "tls-unique" is as the default channel binding to use over TLS. As "tls-unique" is
not defined for TLS 1.3 (and greater), this document updates not defined for TLS 1.3 (and greater), this document updates
[RFC5801] and [RFC5802] to use "tls-exporter" as the default channel [RFC5801] and [RFC5802] to use "tls-exporter" as the default channel
binding over TLS 1.3 (and greater). binding over TLS 1.3 (and greater).
3. Security Considerations 3. Security Considerations
Channel bindings do not leak secret information about the channel and The channel binding type defined in this document is constructed so
are considered public. Implementations MUST NOT use the channel that disclosure of the channel binding data does not leak secret
binding to protect secret information. information about the TLS channel and does not affect the security of
the TLS channel. Implementations MUST NOT use the channel 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. Use with Legacy TLS
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 [RFC7627] and the Security Considerations
[RFC5705]. section of [RFC5705].
When TLS renegotiation is enabled the "tls-exporter" channel binding When TLS renegotiation is enabled on a connection the "tls-exporter"
type is not defined and implementations MUST NOT support it. channel binding type is not defined for that connection and
implementations MUST NOT 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.
The derived data MUST NOT be used for any purpose other than channel The derived data MUST NOT be used for any purpose other than channel
bindings as described in [RFC5056]. bindings as described in [RFC5056].
4. IANA Considerations 4. IANA Considerations
4.1. Registration of Channel Binding Type 4.1. Registration of Channel Binding Type
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This document adds the following registration in the "Channel-Binding This document adds the following registration in the "Channel-Binding
Types" registry: Types" registry:
Subject: Registration of channel binding tls-exporter Subject: Registration of channel binding tls-exporter
Channel binding unique prefix: tls-exporter Channel binding unique prefix: tls-exporter
Channel binding type: unique Channel binding type: unique
Channel type: TLS [RFC8446] Channel type: TLS [RFC8446]
Published specification: draft-ietf-kitten-tls-channel-bindings-for- Published specification: draft-ietf-kitten-tls-channel-bindings-for-
tls13-08 tls13-09
Channel binding is secret: no Channel binding is secret: no
Description: The EKM value obtained from the current TLS connection. Description: The EKM value obtained from the current TLS connection.
Intended usage: COMMON Intended usage: COMMON
Person and email address to contact for further information: Sam Person and email address to contact for further information: Sam
Whited <sam@samwhited.com>. Whited <sam@samwhited.com>.
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