Re: [MMUSIC] Handling of unverified data and media
Martin Thomson <martin.thomson@gmail.com> Fri, 10 March 2017 02:42 UTC
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From: Martin Thomson <martin.thomson@gmail.com>
Date: Fri, 10 Mar 2017 10:58:00 +1100
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To: Bernard Aboba <bernard.aboba@gmail.com>
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Cc: Flemming Andreasen <fandreas@cisco.com>, "hta@google.com" <hta@google.com>, mmusic WG <mmusic@ietf.org>
Subject: Re: [MMUSIC] Handling of unverified data and media
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I think that the data channel question is easy, anything other than a "no" is not acceptable. Data in that form enters the security boundary for an origin and it doesn't make any sense to risk attack there. (It's also likely unnecessary, if a half a round trip of signaling is slower than 5 round trips on the media path, then something is messed up.) I'm in two minds about the media part. For media, you could also reasonably make the same origin-purity argument. I'm inclined to say that. But we CAN isolate media from the origin (and we definitely should if we allow this). So, the media that arrives had to comply with your offer. The DTLS handshake also has to complete, which tells the receiver whether the media needs to be confidential or not (at which point you can disable this feature). It's also possible that a receiver can require that an ICE connectivity check was made (though this is inbound only, and I'm unclear on whether having received an inbound check would normally prevent the receiver from accepting a packet). All told, that's a lot of information about the negotiated session for an attacker to have. The odds of this being an attack would *seem* to be low. On the other hand, we don't assume confidentiality of signaling; the security model assumes that all this information is effectively public and the protection we have against attack is the certificate fingerprint. This would remove that protection, albeit for a short duration. I have an extra question: does anyone plan to implement this? It's non-trivial. I think that I know what I'd need to do in Firefox and it would be quite disruptive. Before committing to do that work (which I will leave to others closer to this to decide), I'd probably want more information on the actual advantage that it provides. On 10 March 2017 at 07:10, Bernard Aboba <bernard.aboba@gmail.com> wrote: > In the W3C WEBRTC WG, an issue has been submitted relating to playout of > unverified media: > https://github.com/w3c/webrtc-pc/issues/849 > > It has been suggested that if the browser is configured to do so, that > playout be allowed for a limited period (e.g. 5 seconds) prior to > fingerprint verification: > https://github.com/w3c/webrtc-pc/pull/1026 > > Section 6.2 of draft-ietf-mmusic-4572-update-13 contains the following text, > carried over from RFC 4572: > > Note that when the offer/answer model is being used, it is possible > for a media connection to outrace the answer back to the offerer. > Thus, if the offerer has offered a 'setup:passive' or 'setup:actpass' > role, it MUST (as specified in RFC 4145 [7]) begin listening for an > incoming connection as soon as it sends its offer. However, it MUST > NOT assume that the data transmitted over the TLS connection is valid > until it has received a matching fingerprint in an SDP answer. If > the fingerprint, once it arrives, does not match the client's > certificate, the server endpoint MUST terminate the media connection > with a bad_certificate error, as stated in the previous paragraph. > > Given the outstanding issue relating to handling of unverified media, the > Chairs of the W3C WEBRTC WG would like to request clarification from the > IETF MMUSIC WG as to the meaning of the "MUST NOT" in the above paragraph. > In particular, what is it permitted for an implementation to do with > received data and media prior to verification? For example: > > 1. May data received over the data channel be provided to the > application prior to verification? > a. If the answer to the above is "no", may unverified received data > be delivered by the DTLS transport to SCTP, which may buffer it? > 2. May received media be played out prior to verification? > > Bernard Aboba > On behalf of the W3C WEBRTC WG > > _______________________________________________ > mmusic mailing list > mmusic@ietf.org > https://www.ietf.org/mailman/listinfo/mmusic >
- [MMUSIC] Handling of unverified data and media Bernard Aboba
- Re: [MMUSIC] Handling of unverified data and media Martin Thomson
- Re: [MMUSIC] Handling of unverified data and media Roman Shpount
- Re: [MMUSIC] Handling of unverified data and media Eric Rescorla
- Re: [MMUSIC] Handling of unverified data and media Bernard Aboba
- Re: [MMUSIC] Handling of unverified data and media Eric Rescorla
- Re: [MMUSIC] Handling of unverified data and media Christer Holmberg
- Re: [MMUSIC] Handling of unverified data and media Iñaki Baz Castillo
- Re: [MMUSIC] Handling of unverified data and media Christer Holmberg
- Re: [MMUSIC] Handling of unverified data and media Iñaki Baz Castillo
- Re: [MMUSIC] Handling of unverified data and media Christer Holmberg
- Re: [MMUSIC] Handling of unverified data and media Cullen Jennings
- Re: [MMUSIC] Handling of unverified data and media Martin Thomson
- Re: [MMUSIC] Handling of unverified data and media Jonathan Lennox
- Re: [MMUSIC] Handling of unverified data and media Roman Shpount
- Re: [MMUSIC] Handling of unverified data and media Christer Holmberg
- Re: [MMUSIC] Handling of unverified data and media Jonathan Lennox
- Re: [MMUSIC] Handling of unverified data and media Christer Holmberg
- Re: [MMUSIC] Handling of unverified data and media Cullen Jennings
- Re: [MMUSIC] Handling of unverified data and media Peter Thatcher
- Re: [MMUSIC] Handling of unverified data and media Martin Thomson
- Re: [MMUSIC] Handling of unverified data and media Bernard Aboba
- Re: [MMUSIC] Handling of unverified data and media Martin Thomson
- Re: [MMUSIC] Handling of unverified data and media Peter Thatcher
- Re: [MMUSIC] Handling of unverified data and media Roman Shpount
- Re: [MMUSIC] Handling of unverified data and media Cullen Jennings
- Re: [MMUSIC] Handling of unverified data and media Cullen Jennings
- Re: [MMUSIC] Handling of unverified data and media Martin Thomson
- Re: [MMUSIC] Handling of unverified data and media Peter Thatcher
- Re: [MMUSIC] Handling of unverified data and media Roman Shpount
- Re: [MMUSIC] Handling of unverified data and media Peter Thatcher