[FFmpeg-devel] [PATCH] avformat/dashdec: only limit DASH manifest size according to AVBprint limits

[Steven Liu]

Jan Ekström <jeebjp at gmail.com> 于2020年9月4日周五 上午2:33写道：
>
> Currently the API is internally limited to unsigned integers, so if we
> limit the file size as well as the amount to read to UINT_MAX - 1, we
> do not require additional limiting to be performed on the values.
>
> This change is based on the fact that initially the 8*1024 value added
> in 96d70694aea64616c68db8be306c159c73fb3980 was only for the case where
> the file size was not known. It was not a maximum file size limit.
>
> In 29121188983932f79aef8501652630d322a9974c this was reworked to be
> a maximum manifest file size limit, while its commit message appears
> to only note that it added support for larger manifest file sizes.
>
> This should enable various unfortunately large MPEG-DASH manifests,
> such as Youtube's multi-megabyte live stream archives to load up
> as well as bring back the original intent of the logic.
> ---
>  libavformat/dashdec.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
> index c5a5ff607b..1e9985f32c 100644
> --- a/libavformat/dashdec.c
> +++ b/libavformat/dashdec.c
> @@ -29,7 +29,7 @@
>  #include "dash.h"
>
>  #define INITIAL_BUFFER_SIZE 32768
> -#define MAX_MANIFEST_SIZE 50 * 1024
> +#define MAX_BPRINT_READ_SIZE (UINT_MAX - 1)
>  #define DEFAULT_MANIFEST_SIZE 8 * 1024
>
>  struct fragment {
> @@ -1256,14 +1256,16 @@ static int parse_manifest(AVFormatContext *s, const char *url, AVIOContext *in)
>      }
>
>      filesize = avio_size(in);
> -    if (filesize > MAX_MANIFEST_SIZE) {
> +    filesize = filesize > 0 ? filesize : DEFAULT_MANIFEST_SIZE;
> +
> +    if (filesize > MAX_BPRINT_READ_SIZE) {
>          av_log(s, AV_LOG_ERROR, "Manifest too large: %"PRId64"\n", filesize);
>          return AVERROR_INVALIDDATA;
>      }
>
> -    av_bprint_init(&buf, (filesize > 0) ? filesize + 1 : DEFAULT_MANIFEST_SIZE, AV_BPRINT_SIZE_UNLIMITED);
> +    av_bprint_init(&buf, filesize + 1, AV_BPRINT_SIZE_UNLIMITED);
>
> -    if ((ret = avio_read_to_bprint(in, &buf, MAX_MANIFEST_SIZE)) < 0 ||
> +    if ((ret = avio_read_to_bprint(in, &buf, MAX_BPRINT_READ_SIZE)) < 0 ||
>          !avio_feof(in) ||
>          (filesize = buf.len) == 0) {
>          av_log(s, AV_LOG_ERROR, "Unable to read to manifest '%s'\n", url);
> --
> 2.26.2
>
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Not proficient in English, but code looks ok. :D


Thanks jeeb


Steven