Re: [FFmpeg-devel] [PATCH] fftools/ffmpeg: avoid possible invalid reads with short -tag values

[James Almer <jamrial@gmail.com>]

On 4/13/2023 11:14 AM, James Almer wrote:
> On 4/13/2023 10:59 AM, Anton Khirnov wrote:
>> Fixes #10319.

Should also fix #10309 i think.

>> ---
>>   fftools/ffmpeg_demux.c    | 8 ++++++--
>>   fftools/ffmpeg_mux_init.c | 7 +++++--
>>   2 files changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c
>> index b9849d1669..d89e28b9f6 100644
>> --- a/fftools/ffmpeg_demux.c
>> +++ b/fftools/ffmpeg_demux.c
>> @@ -736,8 +736,12 @@ static void add_input_streams(const 
>> OptionsContext *o, Demuxer *d)
>>           MATCH_PER_STREAM_OPT(codec_tags, str, codec_tag, ic, st);
>>           if (codec_tag) {
>>               uint32_t tag = strtol(codec_tag, &next, 0);
>> -            if (*next)
>> -                tag = AV_RL32(codec_tag);
>> +            if (*next) {
>> +                uint8_t buf[4] = { 0 };
>> +                memcpy(buf, codec_tag, FFMIN(sizeof(buf), 
>> strlen(codec_tag)));
>> +                tag = AV_RL32(buf);
>> +            }
>> +
>>               st->codecpar->codec_tag = tag;
>>           }
>> diff --git a/fftools/ffmpeg_mux_init.c b/fftools/ffmpeg_mux_init.c
>> index 62e5643a04..aab423464c 100644
>> --- a/fftools/ffmpeg_mux_init.c
>> +++ b/fftools/ffmpeg_mux_init.c
>> @@ -610,8 +610,11 @@ static OutputStream *new_output_stream(Muxer 
>> *mux, const OptionsContext *o,
>>       MATCH_PER_STREAM_OPT(codec_tags, str, codec_tag, oc, st);
>>       if (codec_tag) {
>>           uint32_t tag = strtol(codec_tag, &next, 0);
>> -        if (*next)
>> -            tag = AV_RL32(codec_tag);
>> +        if (*next) {
>> +            uint8_t buf[4] = { 0 };
>> +            memcpy(buf, codec_tag, FFMIN(sizeof(buf), 
>> strlen(codec_tag)));
>> +            tag = AV_RL32(buf);
>> +        }
>>           ost->st->codecpar->codec_tag = tag;
>>           if (ost->enc_ctx)
>>               ost->enc_ctx->codec_tag = tag;
> 
> LGTM.
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