[FFmpeg-devel] [PATCH 1/3] avformat/dashdec: fail on probing non mpd file extension

[James Almer]

On 5/6/2023 10:25 AM, Michael Niedermayer wrote:
> Its unexpected that a .avi or other "standard" file turns into a playlist.
> The goal of this patch is to avoid this unexpected behavior and possible
> privacy or security differences.
> 
> This is similar to the same change to hls
> 
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>   libavformat/dashdec.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
> index 29d4680c68..294e14150d 100644
> --- a/libavformat/dashdec.c
> +++ b/libavformat/dashdec.c
> @@ -2336,10 +2336,13 @@ static int dash_probe(const AVProbeData *p)
>           av_stristr(p->buf, "dash:profile:isoff-live:2011") ||
>           av_stristr(p->buf, "dash:profile:isoff-live:2012") ||
>           av_stristr(p->buf, "dash:profile:isoff-main:2011") ||
> -        av_stristr(p->buf, "3GPP:PSS:profile:DASH1")) {
> -        return AVPROBE_SCORE_MAX;
> -    }
> -    if (av_stristr(p->buf, "dash:profile")) {
> +        av_stristr(p->buf, "3GPP:PSS:profile:DASH1") ||
> +        av_stristr(p->buf, "dash:profile")) {
> +        if (!av_match_ext(p->filename, "mpd")) {
> +            av_log(NULL, AV_LOG_ERROR, "Not detecting dash with non standard extension\n");
> +            return 0;
> +        }
> +
>           return AVPROBE_SCORE_MAX;
>       }

Failing because it didn't match an extensions sort of goes against the 
point of probing, which even has a low score return value that's 
basically "it matched extension" as a sort of last resort.

I'd say wrap this in a FF_COMPLIANCE_STRICT check (since i assume the 
spec does state mpd must be the extension), but i think we have no 
access to the AVFormatContext here?