An ICE Option for MESSAGE-INTEGRITY-SHA256

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Table of Contents

1. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

2. Introduction

Interactive Connectivity Establishment (ICE) [RFC8445] uses STUN [RFC8489] with short-term credentials for connectivity checks. However, ICE assumes a single MESSAGE-INTEGRITY algorithm (SHA-1) and does not provide a mechanism for hash agility.¶

STUN defines a mechanism for hash agility and requires usages to define their own negotiation method as described in Section 16.3 of [RFC8489].¶

This document updates ICE by defining an ICE option "mi256" that signals support for MESSAGE-INTEGRITY-SHA256 and specifies how it is used for connectivity checks.¶

3. ICE Option

This document defines a new ICE option "mi256" following the procedures in [RFC8839] which indiciates support for the comprehension-required MESSAGE-INTEGRITY-SHA256 STUN attribute.¶

When the "mi256" ice-option is supported by both agents, all STUN transactions in the ICE session¶

• MUST include the MESSAGE-INTEGRITY-SHA256 attribute and¶

• MUST NOT include the MESSAGE-INTEGRITY attribute.¶

Truncation is not permitted.¶

4. Peer-reflexive candidates

STUN Binding requests using MESSAGE-INTEGRITY-SHA256 for authentication can arrive at the offerer before the SDP answer containing the ice-options attribute.¶

If the request verifies correctly using the expected ICE short term credential, the agent infers that the peer supports the "mi256" ICE option semantics for the current ICE session.¶

5. Security Considerations

This document improves the security of ICE by enabling the use of SHA-256 instead of SHA-1 for message integrity.¶

6. IANA Considerations

This document requests that IANA make the following registrations:¶

7. 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/rfc/rfc2119>.

[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/rfc/rfc8174>.

[RFC8445]

Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal", RFC 8445, DOI 10.17487/RFC8445, July 2018, <https://www.rfc-editor.org/rfc/rfc8445>.

[RFC8489]

Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing, D., Mahy, R., and P. Matthews, "Session Traversal Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489, February 2020, <https://www.rfc-editor.org/rfc/rfc8489>.

[RFC8839]

Petit-Huguenin, M., Nandakumar, S., Holmberg, C., Keränen, A., and R. Shpount, "Session Description Protocol (SDP) Offer/Answer Procedures for Interactive Connectivity Establishment (ICE)", RFC 8839, DOI 10.17487/RFC8839, January 2021, <https://www.rfc-editor.org/rfc/rfc8839>.

Authors' Addresses