[Webkit-unassigned] [Bug 169681] New: [WebRTC] SDP sess-id in the "o=" line should be a value between 0 and LLONG_MAX.

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Mar 15 09:36:24 PDT 2017


            Bug ID: 169681
           Summary: [WebRTC] SDP sess-id in the "o=" line should be a
                    value between 0 and LLONG_MAX.
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: clopez at igalia.com
                CC: alex at igalia.com, bugs-noreply at webkitgtk.org

For the origin ("o=") line of the SDP
    o=<username> <sess-id> <sess-version> <nettype> <addrtype> <unicast-address>

RFC 3264 says:
    The numeric value of the session id and version in the o line MUST be representable with a 64 bit signed integer. 
    The initial value of the version MUST be less than (2**62)-1, to avoid rollovers.

RFC 4566 defines both values as:
    sess-id =             1*DIGIT
                         ;should be unique for this username/host
    sess-version =        1*DIGIT

    According to the ABNF grammar defined in RFC 5234:
        1*DIGIT means at least one ([1-inf]) numeric characters [0-9].

    So, this means this values should be an integer value >= 0.

The combination says only values from 0 - 2^63-1 pass both tests for the session-id and values from 0 - 2^62-1 for the version.

Therefore I understand the following:

 - We should use int64_t for representing both values (sess-id and sess-version).
 - The session-id value generated must be an integer inside [0 - 2^63-1]
 - The version value generated must be an integer inside [0 - 2^62-1]

Right now we are using uint_64t for the session id, and for the initial session id value we generate a random number that sometimes exceeds LLONG_MAX.

And when that happens firefox rejects our SDP offer.

I observed that firefox gives this fatal error on AppRTC when we generate a session-id bigger than LLONG_MAX
    setRemoteDescription: InvalidSessionDescriptionError: Failed to parse SDP: SDP Parse Error on line 2:  Invalid owner session id specified for o=.


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