Subject: [stir] [Technical Errata Reported] RFC8224 (5390)

From: RFC Errata System <[email-masked]>
Date: Thu, 14 Jun 2018 12:52:46 -0700 (PDT)

The following errata report has been submitted for RFC8224,
"Authenticated Identity Management in the Session Initiation Protocol (SIP)".

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You may review the report below and at:
http://www.rfc-editor.org/errata/eid5390

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Type: Technical
Reported by: Invalid restriction on when to add "mky" <[email-masked]>

Section: 12.1

Original Text
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When signing a request that contains a fingerprint of keying material
in SDP for DTLS-SRTP [RFC5763], this mechanism always provides a
signature over that fingerprint. 

Corrected Text
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When signing a request that contains a fingerprint
of keying material in SDP, this mechanism always 
provides a signature over that fingerprint. 

Notes
-----
Attack vector described in 12.1 to justify addition of "mky" is applicable for scenarios, where a fingerprint in SDP is used for reasons other than DTLS-STRP as well. 
Use of fingerprint for MSRP per RFCRFC4975 is an example of this.

>From RFC4975:

14.4.  Using TLS in Peer-to-Peer Mode

   TLS can be used with a self-signed certificate as long as there is a
   mechanism for both sides to ascertain that the other side used the
   correct certificate.  When used with SDP and SIP, the correct
   certificate can be verified by passing a fingerprint of the
   certificate in the SDP and ensuring that the SDP has suitable
   integrity protection.  When SIP is used to transport the SDP, the
   integrity can be provided by the SIP Identity mechanism [17].  The
   rest of this section describes the details of this approach.

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RFC8224 (draft-ietf-stir-rfc4474bis-16)
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Title               : Authenticated Identity Management in the Session Initiation Protocol (SIP)
Publication Date    : February 2018
Author(s)           : J. Peterson, C. Jennings, E. Rescorla, C. Wendt
Category            : PROPOSED STANDARD
Source              : Secure Telephone Identity Revisited
Area                : Applications and Real-Time
Stream              : IETF
Verifying Party     : IESG