[FFmpeg-devel] [PATCH] avformat/hls: Fixes overwriting existing #EXT-X-PROGRAM-DATE-TIME value in HLS playlist
Vignesh Ravichandran
vignesh.ravichandran02 at gmail.com
Wed Nov 25 13:49:18 EET 2020
We could add a simple check like below to prevent it:
if (sscanf(ptr, "%d-%d-%dT%d:%d:%d.%lf", &y, &M, &d, &h, &m, &s, &ms) != 7)
{
ret = AVERROR_INVALIDDATA;
goto fail;
}
Please let me know.
Thanks,
Vignesh
On Wed, Nov 25, 2020 at 11:29 AM Steven Liu <lq at chinaffmpeg.org> wrote:
>
>
> > 2020年11月25日 下午1:16，Vignesh Ravichandran <
> vignesh.ravichandran02 at gmail.com> 写道：
> >
> > Bug ID: 8989
> >
> > This is is due to the following behavior in the current code:
> > 1. The initial_prog_date_time gets set to the current local time
> > 2. The existing playlist (.m3u8) file gets parsed and the segments
> present are added to the variant stream
> > 3. The new segment is created and added
> > 4. The existing segments and the new segment are written to the playlist
> file. The initial_prog_date_time from point 1 is used for calculating
> "#EXT-X-PROGRAM-DATE-TIME" for the segments, which results in incorrect
> "#EXT-X-PROGRAM-DATE-TIME" values for existing segments
> >
> > The following approach fixes this bug:
> > 1. Add a new variable "discont_program_date_time" of type double to
> HLSSegment struct
> > 2. Store the "EXT-X-PROGRAM-DATE-TIME" value from the existing segments
> in this variable
> > 3. When writing to playlist file if "discont_program_date_time" is set,
> then use that value for "EXT-X-PROGRAM-DATE-TIME" else use the value
> present in vs->initial_prog_date_time
> >
> > Signed-off-by: Vignesh Ravichandran <vignesh.ravichandran02 at gmail.com>
> > ---
> > libavformat/hlsenc.c | 35 +++++++++++++++++++++++++++++++----
> > 1 file changed, 31 insertions(+), 4 deletions(-)
> >
> > diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> > index cbfd8f7c0d..030a2d3b97 100644
> > --- a/libavformat/hlsenc.c
> > +++ b/libavformat/hlsenc.c
> > @@ -88,6 +88,7 @@ typedef struct HLSSegment {
> > char iv_string[KEYSIZE*2 + 1];
> >
> > struct HLSSegment *next;
> > + double discont_program_date_time;
> > } HLSSegment;
> >
> > typedef enum HLSFlags {
> > @@ -1124,6 +1125,7 @@ static int hls_append_segment(struct
> AVFormatContext *s, HLSContext *hls,
> > en->keyframe_size = vs->video_keyframe_size;
> > en->next = NULL;
> > en->discont = 0;
> > + en->discont_program_date_time = 0;
> >
> > if (vs->discontinuity) {
> > en->discont = 1;
> > @@ -1148,7 +1150,8 @@ static int hls_append_segment(struct
> AVFormatContext *s, HLSContext *hls,
> >
> > if (hls->max_nb_segments && vs->nb_entries >= hls->max_nb_segments) {
> > en = vs->segments;
> > - vs->initial_prog_date_time += en->duration;
> > + if (!en->next->discont_program_date_time &&
> !en->discont_program_date_time)
> > + vs->initial_prog_date_time += en->duration;
> > vs->segments = en->next;
> > if (en && hls->flags & HLS_DELETE_SEGMENTS &&
> > #if FF_API_HLS_WRAP
> > @@ -1182,6 +1185,8 @@ static int parse_playlist(AVFormatContext *s,
> const char *url, VariantStream *vs
> > char line[MAX_URL_SIZE];
> > const char *ptr;
> > const char *end;
> > + int is_discont_detected = 0;
> > + double discont_program_date_time = 0;
> >
> > if ((ret = ffio_open_whitelist(&in, url, AVIO_FLAG_READ,
> > &s->interrupt_callback, NULL,
> > @@ -1211,6 +1216,7 @@ static int parse_playlist(AVFormatContext *s,
> const char *url, VariantStream *vs
> > } else if (av_strstart(line, "#EXT-X-DISCONTINUITY", &ptr)) {
> > is_segment = 1;
> > vs->discontinuity = 1;
> > + is_discont_detected = 1;
> > } else if (av_strstart(line, "#EXTINF:", &ptr)) {
> > is_segment = 1;
> > vs->duration = atof(ptr);
> > @@ -1236,7 +1242,23 @@ static int parse_playlist(AVFormatContext *s,
> const char *url, VariantStream *vs
> > av_strlcpy(vs->iv_string, ptr,
> sizeof(vs->iv_string));
> > }
> > }
> > -
> > + } else if (av_strstart(line, "#EXT-X-PROGRAM-DATE-TIME:", &ptr)
> && is_discont_detected) {
> > + struct tm program_date_time;
> > + int y,M,d,h,m,s;
> > + double ms;
> > + sscanf(ptr, "%d-%d-%dT%d:%d:%d.%lf", &y, &M, &d, &h, &m,
> &s, &ms);
> What will happen if I modify the value of “EXT-X-PROGRAM-DATE-TIME” by
> hacker,
> For example:
> #EXT-X-PROGRAM-DATA-TIME: good-morning-ladies-and-gentlemen.
>
> > +
> > + program_date_time.tm_year = y - 1900;
> > + program_date_time.tm_mon = M - 1;
> > + program_date_time.tm_mday = d;
> > + program_date_time.tm_hour = h;
> > + program_date_time.tm_min = m;
> > + program_date_time.tm_sec = s;
> > + program_date_time.tm_isdst = -1;
> > +
> > + discont_program_date_time = mktime(&program_date_time);
> > + discont_program_date_time += (double)(ms / 1000);
> > + is_discont_detected = 0;
> > } else if (av_strstart(line, "#", NULL)) {
> > continue;
> > } else if (line[0]) {
> > @@ -1250,8 +1272,9 @@ static int parse_playlist(AVFormatContext *s,
> const char *url, VariantStream *vs
> > is_segment = 0;
> > new_start_pos = avio_tell(vs->avf->pb);
> > vs->size = new_start_pos - vs->start_pos;
> > - vs->initial_prog_date_time -= vs->duration; // this is
> a previously existing segment
> > ret = hls_append_segment(s, hls, vs, vs->duration,
> vs->start_pos, vs->size);
> > + vs->last_segment->discont_program_date_time =
> discont_program_date_time;
> > + discont_program_date_time += vs->duration;
> > if (ret < 0)
> > goto fail;
> > vs->start_pos = new_start_pos;
> > @@ -1572,7 +1595,11 @@ static int hls_window(AVFormatContext *s, int
> last, VariantStream *vs)
> > ret = ff_hls_write_file_entry(byterange_mode ? hls->m3u8_out :
> vs->out, en->discont, byterange_mode,
> > en->duration, hls->flags &
> HLS_ROUND_DURATIONS,
> > en->size, en->pos, hls->baseurl,
> > - en->filename, prog_date_time_p,
> en->keyframe_size, en->keyframe_pos, hls->flags & HLS_I_FRAMES_ONLY);
> > + en->filename,
> > + en->discont_program_date_time ?
> &en->discont_program_date_time : prog_date_time_p,
> > + en->keyframe_size,
> en->keyframe_pos, hls->flags & HLS_I_FRAMES_ONLY);
> > + if (en->discont_program_date_time)
> > + en->discont_program_date_time -= en->duration;
> > if (ret < 0) {
> > av_log(s, AV_LOG_WARNING, "ff_hls_write_file_entry get
> error\n");
> > }
> > --
> > 2.24.2 (Apple Git-127)
> >
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>
> Thanks
>
> Steven Liu
>
>
>
>
More information about the ffmpeg-devel
mailing list