[Gen-art] Gen-ART review of draft-ietf-sip-dtls-srtp-framework-05.txt

I am the assigned Gen-ART reviewer for
draft-ietf-sip-dtls-srtp-framework-05.txt

For background on Gen-ART, please see the FAQ at
<http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html>.

Please resolve these comments along with any other Last Call comments
you may receive.

Summary: This draft is almost ready for publication as Proposed 
Standard, but I have a few comments.

Substantial
===========

Section 8.1: Responder identity

When Bob does not respond with an UPDATE message, his identity is not 
integrity protected. The draft states that in such case, a MITM attacker 
may tamper with the fingerprint but Bob would be aware of this. It is 
not clear to me how Bob would be aware of this. Consider the scenario 
where an attacker Eve (who can attack both the signaling and media 
paths) has switched Bob's key fingerprint with hers. She can receive 
encrypted media coming from Alice, decrypt it for her own use and 
re-encrypt it for Bob and send it to him. How will Bob detect this 
tampering?

Minor
=====

* draft-ietf-avt-dtls-srtp-05 needs to become a Normative reference 
instead of an informative reference. Section 6.10 has the following text

"Implementations of this specification MUST support DTLS-SRTP"

making it impossible to implement this spec without implementing 
DTLS-SRTP. This will also lead to a downref that needs to be called out.

* Section 7: Call flow with STUN

"Message (6):  STUN connectivity-check response Bob -> Alice"

Bob is responding to Message 5 instead of Message 3 as stated in the 
text. Please replace.

Editorial
=========

* SBC (expand at first use) : Probably add reference to 
draft-ietf-sipping-sbc-funcs-07

* Section 6.10: s/less highly optimized/less optimized/

Typos
=====
Section 1 Para 4: s/sigaling/signaling/

Section 6.7.2: s/appopriate/appropriate/

Section 6.9 Title: s/Encryptions/Encryption/

Section 7 Para 3: s/especialy/especially/

Section 8.6 para 2: s/taht/that/

Appendix A.3. : s/Reusage/Reuse/

Appendix A.18. : s/Negotation/Negotiation/

Cheers
Suresh

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