[FFmpeg-devel] [PATCH] avcodec/options_table: remove extradata_size from the AVOptions table

[Michael Niedermayer]

On Mon, Mar 09, 2015 at 01:27:58PM +0100, Lukasz Marek wrote:
> On 9 March 2015 at 12:19, Andreas Cadhalpun <
> andreas.cadhalpun at googlemail.com> wrote:
> 
> > On 09.03.2015 03:42, Michael Niedermayer wrote:
> >
> >> allowing access to the size but not the extradata itself is not useful
> >> and could lead to potential problems if writing happens through this field
> >>
> >> Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> >> ---
> >>   libavcodec/options_table.h |    1 -
> >>   1 file changed, 1 deletion(-)
> >>
> >> diff --git a/libavcodec/options_table.h b/libavcodec/options_table.h
> >> index 442b212..a906864 100644
> >> --- a/libavcodec/options_table.h
> >> +++ b/libavcodec/options_table.h
> >> @@ -103,7 +103,6 @@ static const AVOption avcodec_options[] = {
> >>   {"hex", "hex motion estimation", 0, AV_OPT_TYPE_CONST, {.i64 = ME_HEX
> >> }, INT_MIN, INT_MAX, V|E, "me_method" },
> >>   {"umh", "umh motion estimation", 0, AV_OPT_TYPE_CONST, {.i64 = ME_UMH
> >> }, INT_MIN, INT_MAX, V|E, "me_method" },
> >>   {"iter", "iter motion estimation", 0, AV_OPT_TYPE_CONST, {.i64 =
> >> ME_ITER }, INT_MIN, INT_MAX, V|E, "me_method" },
> >> -{"extradata_size", NULL, OFFSET(extradata_size), AV_OPT_TYPE_INT, {.i64
> >> = DEFAULT }, INT_MIN, INT_MAX},
> >>   {"time_base", NULL, OFFSET(time_base), AV_OPT_TYPE_RATIONAL, {.dbl =
> >> 0}, INT_MIN, INT_MAX},
> >>   {"g", "set the group of picture (GOP) size", OFFSET(gop_size),
> >> AV_OPT_TYPE_INT, {.i64 = 12 }, INT_MIN, INT_MAX, V|E},
> >>   {"ar", "set audio sampling rate (in Hz)", OFFSET(sample_rate),
> >> AV_OPT_TYPE_INT, {.i64 = DEFAULT }, 0, INT_MAX, A|D|E},
> >>
> >>
> > This looks very good, because it also fixes the ffm muxer to never create
> > files with extradata_size setting, but without extradata.
> >
> 
> Isn't it API break? Maybe it is better to have a look on asv1 or ffm muxer
> to fix problem itself, not to cover it.
> I can have a look on this today's evening.

you miss the problem, this is a demuxer side problem,
a attacker can at least crash your application no muxer side change
can fix this, the attacker has his own self written muxer that
produces a mallicious bitstream

of course you are correct that there is possibly also a problem on the
muxer side and that this too should be fixed but that is less
important.


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No snowflake in an avalanche ever feels responsible. -- Voltaire
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