[libav-bugs] [Bug 803] New: libav supposedly hangs if RTSP session id contains $ or +

bugzilla at aruru.libav.org bugzilla at aruru.libav.org
Thu Jan 15 20:51:06 CET 2015


https://bugzilla.libav.org/show_bug.cgi?id=803

            Bug ID: 803
           Summary: libav supposedly hangs if RTSP session id contains $
                    or +
           Product: Libav
           Version: git HEAD
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: ---
         Component: general
          Assignee: bugzilla at libav.org
          Reporter: sebras at hotmail.com

GStreamer got a ​bug report (https://bugzilla.gnome.org/show_bug.cgi?id=643812)
a while back where christian mentioned that ffmpeg hangs when RTSP session ids
in gst-rtsp-server contain $ or +. Our assumption is that the same bug exists
in libav, please have a look.

Now, ​RFC 2326 (https://tools.ietf.org/html/rfc2326#page-16) actually does not
state that characters can or should be URI-escaped in a session id, only that
linear whitespace should be. However whitespace is not among the allowed
characters in a session id, and neither is % which would be the result of
URI-escaping.

Therefore GStreamer recently accepted a ​patch
(https://bugzilla.gnome.org/show_bug.cgi?id=742869) to refrain from
URI-escaping the session id in the RTSP session header. Instead the argument is
that libav should not hang if it encounters $ or + in the header. While I have
not reproduced this myself I'm CCing christian who reported it. Finally I did
quickly look at the RTSP header parsing code in libav and I fail to find any
code that actually cares about the session id's constituing characters.

Perhaps the problem with $ is that the session id is mixed up with the $ used
to separate multiple channels multiplexed over the same RTSP TCP connection?
I'm far from certain about this, but at least it is part of the parsing and
uses the same character as delimiter.

christian if you can still reproduce this, please chime in here and help out in
getting a better fix for this problem.

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