[FFmpeg-devel] [PATCH 13/21] avformat/matroskadec: Improve length check
michael at niedermayer.cc
Fri Apr 5 13:08:58 EEST 2019
On Wed, Mar 27, 2019 at 12:18:44PM +0100, Andreas Rheinhardt via ffmpeg-devel wrote:
> The earlier code had three flaws:
> 1. The case of an unknown-sized element inside a finite-sized element
> (which is against the specifications) was not caught.
> 2. The error message wasn't helpful: It compared the length of the child
> with the offset of the end of the parent and claimed that the first
> exceeds the latter, although that is not necessarily true.
> 3. Unknown-sized elements that are not parsed can't be skipped. Given
> that according to the Matroska specifications only the segment and the
> clusters can be of unknown-size, this is handled by not allowing any
> other units to have infinite size whereas the earlier code would seek
> back by 1 byte upon encountering an infinite-size element that ought
> to be skipped.
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at googlemail.com>
> libavformat/matroskadec.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
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