Re: [FFmpeg-devel] [PATCH 3/6] avformat/jpegxl_anim_dec: add FF_JPEGXL_CONTAINER_SIGNATURE_LE

[Michael Niedermayer <michael@niedermayer.cc>]

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On Sun, Jun 18, 2023 at 06:57:58PM -0400, Leo Izen wrote:
> On 6/18/23 17:50, Michael Niedermayer wrote:
> > Fixes: out of array read
> > Fixes: 59828/clusterfuzz-testcase-minimized-ffmpeg_dem_JPEGXL_ANIM_fuzzer-5029813220671488
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >   libavformat/jpegxl_anim_dec.c | 13 +++++++------
> >   1 file changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/libavformat/jpegxl_anim_dec.c b/libavformat/jpegxl_anim_dec.c
> > index c62b596f76..7e4d39385c 100644
> > --- a/libavformat/jpegxl_anim_dec.c
> > +++ b/libavformat/jpegxl_anim_dec.c
> > @@ -108,7 +108,7 @@ static int jpegxl_collect_codestream_header(const uint8_t *input_buffer, int inp
> >   static int jpegxl_anim_probe(const AVProbeData *p)
> >   {
> > -    uint8_t buffer[4096];
> > +    uint8_t buffer[4096 + AV_INPUT_BUFFER_PADDING_SIZE];
> >       int copied;
> >       /* this is a raw codestream */
> > @@ -123,7 +123,7 @@ static int jpegxl_anim_probe(const AVProbeData *p)
> >       if (AV_RL64(p->buf) != FF_JPEGXL_CONTAINER_SIGNATURE_LE)
> >           return 0;
> > -    if (jpegxl_collect_codestream_header(p->buf, p->buf_size, buffer, sizeof(buffer), &copied) <= 0 || copied <= 0)
> > +    if (jpegxl_collect_codestream_header(p->buf, p->buf_size, buffer, sizeof(buffer) - AV_INPUT_BUFFER_PADDING_SIZE, &copied) <= 0 || copied <= 0)
> >           return 0;
> >       if (ff_jpegxl_verify_codestream_header(buffer, copied, 0) >= 1)
> > @@ -138,7 +138,8 @@ static int jpegxl_anim_read_header(AVFormatContext *s)
> >       AVIOContext *pb = s->pb;
> >       AVStream *st;
> >       int offset = 0;
> > -    uint8_t head[256];
> > +    uint8_t head[256 + AV_INPUT_BUFFER_PADDING_SIZE];
> > +    const int sizeofhead = sizeof(head) - AV_INPUT_BUFFER_PADDING_SIZE;
> >       int headsize = 0;
> >       int ctrl;
> >       AVRational tb;
> > @@ -147,7 +148,7 @@ static int jpegxl_anim_read_header(AVFormatContext *s)
> >       uint64_t sig16 = avio_rl16(pb);
> >       if (sig16 == FF_JPEGXL_CODESTREAM_SIGNATURE_LE) {
> >           AV_WL16(head, sig16);
> > -        headsize = avio_read(s->pb, head + 2, sizeof(head) - 2);
> > +        headsize = avio_read(s->pb, head + 2, sizeofhead - 2);
> >           if (headsize < 0)
> >               return headsize;
> >           headsize += 2;
> > @@ -178,10 +179,10 @@ static int jpegxl_anim_read_header(AVFormatContext *s)
> >                   if (av_buffer_realloc(&ctx->initial, ctx->initial->size + read) < 0)
> >                       return AVERROR(ENOMEM);
> >               }
> > -            jpegxl_collect_codestream_header(buf, read, head + headsize, sizeof(head) - headsize, &copied);
> > +            jpegxl_collect_codestream_header(buf, read, head + headsize, sizeofhead - headsize, &copied);
> >               memcpy(ctx->initial->data + (ctx->initial->size - read), buf, read);
> >               headsize += copied;
> > -            if (headsize >= sizeof(head) || read < sizeof(buf))
> > +            if (headsize >= sizeofhead || read < sizeof(buf))
> >                   break;
> >           }
> >       }
> 

> What's with the commit message? Seems unrelated to the change.

Must be some copy and paste mistake



[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle

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