Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03
"Martin Thomson" <mt@lowentropy.net> Sun, 03 March 2019 23:09 UTC
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Date: Sun, 03 Mar 2019 18:09:09 -0500
From: Martin Thomson <mt@lowentropy.net>
To: Bo Burman <bo.burman@ericsson.com>, mmusic <mmusic@ietf.org>
Cc: "draft-ietf-mmusic-sdp-uks@ietf.org" <draft-ietf-mmusic-sdp-uks@ietf.org>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/mmusic/G03hznmn5SlmOtZFd5LGrB5JrtA>
Subject: Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03
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Thanks Bo, I've updated the combined review PR: https://github.com/martinthomson/sdp-uks/pull/9 With just the changes discussed: https://github.com/martinthomson/sdp-uks/pull/9/commits/82645026faa84cd1124ba2dcfda07f341175d364 On Sat, Mar 2, 2019, at 01:29, Bo Burman wrote: > Thanks, I believe that addresses almost all of my concerns (see also inline). > > Just a final nit for section 4.1 (also listed in the below); > "...Once the second session completes, Mallory might cause DTLS packets > > sent by Norma to Patsy to be dropped. It is likely that these DTLS packets will > > be discarded by Patsy as Patsy will already have a successful DTLS connection > > established." > [BoB] I think there can still be confusion what you mean with "Once the > second session completes"; suggest changing to "Once the second session > is established", if that was the intention. > Also, a couple of sentences before "Though Patsy...", there's one too > many "is complete" in this sentence: "Once signaling is complete on a > session, ostensibly between Mallory and Norma, is complete." > > Cheers, > /Bo > > > -----Original Message----- > > From: Martin Thomson <mt@lowentropy.net> > > Sent: den 1 mars 2019 07:04 > > To: Bo Burman <bo.burman@ericsson.com>; mmusic <mmusic@ietf.org> > > Cc: draft-ietf-mmusic-sdp-uks@ietf.org > > Subject: Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 > > > > Thanks for reviewing Bo, > > > > I've got the changes I've made up at > > https://github.com/martinthomson/sdp-uks/pull/7 > > > > The changes look like a lot, but that is mostly because of some reordering of > > text. I've reworded a few things to improve clarity. I appreciate having a > > new set of eyes on this. I find I tend to miss places where the text assumes > > too much prior knowledge. > > > > I'll put a second PR up for Flemming's review shortly. That will stack on top of > > this one. > > > > On Tue, Feb 26, 2019, at 00:23, Bo Burman wrote: > > > Hi Martin, > > > > > > I've now also reviewed this and have a set of comments and questions, > > > after taking Magnus' comments and your suggested edits in response to > > > that into account: > > > > > > Section 2.1: > > > * In bullet 2, "complete communications" is slightly unclear (more so > > > if "complete" is used in other contexts further down in the text). Do > > > you with "complete" mean "accept", or perhaps "accept setting up"? > > > > Yes, I can see how this could be confusing. Reworded to: > > > > "2. No entity will successfully establish a session with a peer unless they are > > willing to participate in a session with that peer." > [BoB] OK, good. > > > > > > * Don't understand what is meant with "...second condition..."; is it > > > bullet #2, or is it referring to "...joining two separate sessions"? > > > > Bullet 2, but see below. > > > > > * Also don't really understand in what way that second condition is > > > "not necessary"; to limit the attacker capabilities (related to bullet > > > #2), for the attacker to join two sessions, or something else like > > > "for the attack to succeed"? > > > > > > * Just to confirm, does "removing this constraint" refer to removing > > > use of an identity binding? > > > > Does this make more sense? > > > > "Systems that rely on strong identity bindings, such as those defined in > > {{WEBRTC}} or {{!SIP-ID}}, have a different threat model, which admits the > > possibility of attack by an entity with access to the signaling channel. > > Attacks under these conditions are more feasible as an attacker is assumed > > to be able to both observe and modify signaling messages." > [BoB] Yes, that's much better. > > > > > > Section 3: > > > * Is the "victim" of the first paragraph the same or another victim > > > compared to the one mentioned in the next paragraph? > > > > > > * Is "another entity of the attacker's choice" also to be considered a victim? > > > > Yes, there are really two victims here, so I've reworded to use first victim and > > second victim. > > > > "An attacker causes an > > identity binding to be created that binds an identity they control to the > > fingerprint of a first victim. > > > > "An attacker can thereby cause a second victim to believe that they are > > communicating with an attacker-controlled identity, when they are really > > talking to the first victim. The attacker only needs to create an identity > > assertion that covers a certificate fingerprint of the first victim." > [BoB] OK > > > > > > * The last paragraph in section 3, just before section 3.1 "The same > > > technique..." seems a bit misplaced, after text talking about a > > > solution. Should it perhaps be moved just before the paragraph "The > > > problem..." in section 3? Or, is this "same technique" referring to > > > what is described in section 4? > > > > Yes, this was a little light. I've moved it up with the attack synopsis. > > > > "A variation on the same technique can be used to cause both victims to both > > believe they are talking to the attacker when they are talking to each other. > > In this case, the attacker performs the identity misbinding once for each > > victim." > [BoB] OK > > > > > > Section 4: > > > * First sentence, "similar attack"; similar to what? > > > > Yeah, that lost context. How about: > > > > "Even where the integrity of session signaling can be relied upon, an attacker > > might still be able to create a session where there is confusion about the > > communicating endpoints by substituting the fingerprint of a communicating > > endpoint." > [BoB] OK > > > > > > Section 4.1: > > > * Believe it would be helpful for the reader to better understand why > > > "Mallory has no real interest in seeing that session complete" > > > > The next sentence is intended to explain this point: Mallory needs Patsy to > > maintain her end of the communications, lest Norma believe that the session > > is broken. > > > > > * Same sentence, does "session complete" mean "session setup > > complete"? > > > I first interpreted "complete" as "conclude" in the meaning "terminate"
- [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Magnus Westerlund
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Magnus Westerlund
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Bo Burman
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Bo Burman
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Bo Burman
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Paul Kyzivat
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Flemming Andreasen
- Re: [MMUSIC] WGLC on draft-ietf-mmusic-sdp-uks-03 Martin Thomson