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

[Leo Izen <leo.izen@gmail.com>]

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.

- Leo Izen

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