Subject: [Sipbrandy] Eric Rescorla's No Objection on draft-ietf-sipbrandy-rtpsec-07: (with COMMENT)

From: Datatracker on behalf of Eric Rescorla <[email-masked]>
Date: Wed, 06 Mar 2019 10:47:21 -0800

Eric Rescorla has entered the following ballot position for
draft-ietf-sipbrandy-rtpsec-07: No Objection

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COMMENT:
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Rich version of this review at:
https://mozphab-ietf.devsvcdev.mozaws.net/D4970

IMPORTANT
S 4.1.
>   
>   4.1.  Credentials
>   
>      In order to implement the authentication service function in the user
>      agent, SIP endpoints will need to acquire the credentials needed to
>      sign for their own identity.  That identity is typically carried in

How do relying parties determine whether the certificate is attached
to an intermediary or the client.

S 4.1.
>      possession certificates similar to those used in the email world
>      could be offered for SIP, either for greenfield identifiers or for
>      telephone numbers, this specification does not require their use.
>   
>      For users who do not possess such certificates, DTLS-SRTP [RFC5763]
>      permits the use of self-signed keys.  This profile of STIR employs

This doesn't seem quite right. DTLS-SRTP uses self-signed certs that
go in a fingerprint which is then transitively signed by the cert via
STIR

COMMENTS
S 1.
>      Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14
>   
>   1.  Introduction
>   
>      The Session Initiation Protocol (SIP) [RFC3261] includes a suite of
>      security services, ranging from Digest authentication for

Nit: maybe "including". Ranging is an odd phrase with three things

S 1.
>      available, such as Secure RTP [RFC3711].  However, the practices
>      needed to bind security at the media layer to security at the SIP
>      layer, to provide an assurance that protection is in place all the
>      way up the stack, rely on a great many external security mechanisms
>      and practices, and require a central point of documentation to
>      explain their optimal use as a best practice.

This sentence is kind of run-on.

S 1.
>      and practices, and require a central point of documentation to
>      explain their optimal use as a best practice.
>   
>      Revelations about widespread pervasive monitoring of the Internet
>      have led to a reevaluation of the threat model for Internet
>      communications [RFC7258].  In order to maximize the use of security

I don't actually agree that this is a reevaluation. 3552 already told
you what you needed to know here.

S 3.1.
>      STIR generates a signature over certain features of SIP requests,
>      including header field values that contain an identity for the
>      originator of the request, such as the From header field or P-
>      Asserted-Identity field, and also over the media keys in SDP if they
>      are present.  As currently defined, STIR only provides a signature
>      over the "a=fingerprint" attribute, which is a key fingerprint

Not "only" because you just said that it covered other things. Maybe
"in additon"

S 3.1.
>      Asserted-Identity field, and also over the media keys in SDP if they
>      are present.  As currently defined, STIR only provides a signature
>      over the "a=fingerprint" attribute, which is a key fingerprint
>      utilized by DTLS-SRTP [RFC5763]; consequently, STIR only offers
>      comprehensive protection for SIP sessions, in concert with SDP and
>      SRTP, when DTLS-SRTP is the media security service.  The underlying

I would remove the commas around , in concert,..