Re: [FFmpeg-devel] [PATCH 1/5] avformat/mov: We do not support creation times of 300 billion years ago

From: Marton Balint <cus@passwd.hu>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 1/5] avformat/mov: We do not support creation times of 300 billion years ago
Date: Sun, 28 May 2023 20:53:49 +0200 (CEST)
Message-ID: <9b48247-5fc5-7824-5da9-823d34919252@passwd.hu> (raw)
In-Reply-To: <20230525214019.29048-1-michael@niedermayer.cc>

On Thu, 25 May 2023, Michael Niedermayer wrote:

> Fixes: signed integer overflow: -9223372036854775808 - 2082844800 cannot be represented in type 'long'
> Fixes: 58384/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-6428383700713472
>
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
> libavformat/mov.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 9fdeef057e..3e2c4bc10d 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -1530,6 +1530,10 @@ static void mov_metadata_creation_time(MOVContext *c, AVIOContext *pb, AVDiction
>         }
>     }
>     if (time) {
> +        if (time < INT64_MIN + 2082844800) {
> +            av_log(c->fc, AV_LOG_DEBUG, "creation_time predates big bang\n");
> +            return;
> +        }

Actually creation_time is unsigned, so it cannot be negative. I suggest 
you simply reject everyting less than 0 here. You should also move the 
check to the version == 1 case, because only that can read a "negative" 
value.

Regards,
Marton
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