draft-ietf-kitten-tls-channel-bindings-for-tls13-09.txt   draft-ietf-kitten-tls-channel-bindings-for-tls13-10.txt 
Transport Layer Security S. Whited Transport Layer Security S. Whited
Internet-Draft 1 October 2021 Internet-Draft 15 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: 4 April 2022 Expires: 18 April 2022
Channel Bindings for TLS 1.3 Channel Bindings for TLS 1.3
draft-ietf-kitten-tls-channel-bindings-for-tls13-09 draft-ietf-kitten-tls-channel-bindings-for-tls13-10
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
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This Internet-Draft will expire on 4 April 2022. This Internet-Draft will expire on 18 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.
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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 . . . . . . . . . . . 3 2. The 'tls-exporter' Channel Binding Type . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 3. TLS 1.3 with SCRAM or GSS-API over SASL . . . . . . . . . . . 3
3.1. Use with Legacy TLS . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4.1. Use with Legacy TLS . . . . . . . . . . . . . . . . . . . 3
4.1. Registration of Channel Binding Type . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.2. Registration of Channel Binding TLS Exporter Label . . . 4 5.1. Registration of Channel Binding Type . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Registration of Channel Binding TLS Exporter Label . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 5 6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
The "unique" channel binding types defined in [RFC5929] were found to The "tls-unique" channel binding type defined in [RFC5929] was found
be vulnerable to the "triple handshake vulnerability" to 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]. While TLS 1.3 uses a complete transcript hash defined in [RFC7627]. While TLS 1.3 uses a complete transcript hash
akin to the extended master secret procedures, the safety of channel akin to the extended master secret procedures, the safety of channel
bindings with TLS 1.3 was not analyzed as part of the core protocol 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 work, and so the specification of channel bindings for TLS 1.3 was
deferred. [RFC8446] section C.5 notes the lack of channel bindings deferred. [RFC8446] section C.5 notes the lack of channel bindings
for TLS 1.3; as this document defines such channel bindings, it for TLS 1.3; as this document defines such channel bindings, it
updates [RFC8446] to note that this gap has been filled. updates [RFC8446] to note that this gap has been filled.
Furthermore, this document updates [RFC5929] by adding an additional Furthermore, this document updates [RFC5929] by adding an additional
unique channel binding type that replaces some usage of "tls-unique". unique channel binding type, "tls-exporter", 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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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 Label: The ASCII string "EXPORTER-Channel-Binding" with no
terminating NUL. terminating NUL.
Context value: Empty context value. Context value: Zero-length string.
Length: 32 bytes. Length: 32 bytes.
This channel binding mechanism is defined only when TLS cipher
negotiation results in unique master secrets, which is true of TLS
1.3 when renegotiation is disabled.
3. TLS 1.3 with SCRAM or GSS-API over SASL
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 4. Security Considerations
The channel binding type defined in this document is constructed so The channel binding type defined in this document is constructed so
that disclosure of the channel binding data does not leak secret that disclosure of the channel binding data does not leak secret
information about the TLS channel and does not affect the security of information about the TLS channel and does not affect the security of
the TLS channel. Implementations MUST NOT use the channel binding to the TLS channel.
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 4.1. 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 [RFC7627] and the Security Considerations more information see [RFC7627] and the Security Considerations
section of [RFC5705]. section of [RFC5705].
When TLS renegotiation is enabled on a connection the "tls-exporter" When TLS renegotiation is enabled on a connection the "tls-exporter"
channel binding type is not defined for that connection and channel binding type is not defined for that connection and
implementations MUST NOT support it. 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]. In particular, implementations
MUST NOT use channel binding as a secret key to protect privileged
information.
4. IANA Considerations 5. IANA Considerations
4.1. Registration of Channel Binding Type 5.1. Registration of Channel Binding Type
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-
tls13-09 tls13-10
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>.
Owner/Change controller name and email address: IESG. Owner/Change controller name and email address: IESG.
Expert reviewer name and contact information: IETF KITTEN or TLS WG Expert reviewer name and contact information: IETF KITTEN or TLS WG
(kitten@ietf.org or tls@ietf.org, failing that, ietf@ietf.org). (kitten@ietf.org or tls@ietf.org, failing that, ietf@ietf.org).
Note: See the published specification for advice on the Note: See the published specification for advice on the
applicability of this channel binding type. applicability of this channel binding type.
4.2. Registration of Channel Binding TLS Exporter Label 5.2. Registration of Channel Binding TLS Exporter Label
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 Value: EXPORTER-Channel-Binding
DTLS-OK: Y DTLS-OK: Y
Recommended: Y Recommended: Y
Reference: This document Reference: This document
5. References 6. References
5.1. Normative References 6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5056] Williams, N., "On the Use of Channel Bindings to Secure [RFC5056] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007, Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
<https://www.rfc-editor.org/info/rfc5056>. <https://www.rfc-editor.org/info/rfc5056>.
skipping to change at page 5, line 31 skipping to change at page 5, line 43
March 2010, <https://www.rfc-editor.org/info/rfc5705>. March 2010, <https://www.rfc-editor.org/info/rfc5705>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
5.2. Informative References 6.2. Informative References
[RFC5801] Josefsson, S. and N. Williams, "Using Generic Security [RFC5801] Josefsson, S. and N. Williams, "Using Generic Security
Service Application Program Interface (GSS-API) Mechanisms Service Application Program Interface (GSS-API) Mechanisms
in Simple Authentication and Security Layer (SASL): The in Simple Authentication and Security Layer (SASL): The
GS2 Mechanism Family", RFC 5801, DOI 10.17487/RFC5801, GS2 Mechanism Family", RFC 5801, DOI 10.17487/RFC5801,
July 2010, <https://www.rfc-editor.org/info/rfc5801>. July 2010, <https://www.rfc-editor.org/info/rfc5801>.
[RFC5802] Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams, [RFC5802] Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams,
"Salted Challenge Response Authentication Mechanism "Salted Challenge Response Authentication Mechanism
(SCRAM) SASL and GSS-API Mechanisms", RFC 5802, (SCRAM) SASL and GSS-API Mechanisms", RFC 5802,
 End of changes. 21 change blocks. 
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