Re: [FFmpeg-devel] [PATCH RFC] avformat/hls: check IV size inside EXT-X-KEY

[Steven Liu <lingjiujianke@gmail.com>]

Zhao Zhili <quinkblack@foxmail.com> 于2022年4月12日周二 16:28写道：
>
> IV should always be 128 bits. If the IV attribute was truncated
> inside EXT-X-KEY, padding on the left which is the same as when
> using sequence number as IV.
> ---
> I'm not sure which method is better: do padding or just return
> AVERROR_INVALIDDATA?
>
>  libavformat/hls.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/libavformat/hls.c b/libavformat/hls.c
> index 83ff4cc607..a7b632c20e 100644
> --- a/libavformat/hls.c
> +++ b/libavformat/hls.c
> @@ -810,7 +810,13 @@ static int parse_playlist(HLSContext *c, const char *url,
>              if (!strcmp(info.method, "SAMPLE-AES"))
>                  key_type = KEY_SAMPLE_AES;
>              if (!av_strncasecmp(info.iv, "0x", 2)) {
> -                ff_hex_to_data(iv, info.iv + 2);
> +                int n = ff_hex_to_data(iv, info.iv + 2);
> +                if (n < sizeof(iv)) {
> +                    av_log(c->ctx, AV_LOG_WARNING,
> +                           "Incomplete IV %s, padding on the left\n", info.iv);
> +                    memmove(iv + sizeof(iv) - n, iv, n);
> +                    memset(iv, 0, sizeof(iv) - n);
> +                }
>                  has_iv = 1;
>              }
>              av_strlcpy(key, info.uri, sizeof(key));
> --
> 2.31.1
>
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LGTM


Thanks
Steven
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