[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 15:57:46 EET 2020
Sure, how about the snippet below:
regex_t regex;
regcomp(®ex,
"([12][0-9]{3}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])T([01][1-9]|2[0-3]):([0-5][0-9]):([0-5][0-9]).([0-9]{3}))",
REG_EXTENDED);
if (regexec(®ex, ptr, 0, NULL, 0) == REG_NOMATCH) {
ret = AVERROR_INVALIDDATA;
goto fail;
}
On Wed, Nov 25, 2020 at 5:31 PM Steven Liu <lq at chinaffmpeg.org> wrote:
>
>
> > 2020年11月25日 下午7:49，Vignesh Ravichandran <
> vignesh.ravichandran02 at gmail.com> 写道：
> >
> > 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.
> Not sure this is better way, what about validate the string of the
> "#EXT-X-PROGRAM-DATE-TIME” values？
> >
> >
> > 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)
> >>>
> >>> _______________________________________________
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> >>> ffmpeg-devel at ffmpeg.org
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> >>>
> >>> To unsubscribe, visit link above, or email
> >>> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
> >>
> >> Thanks
> >>
> >> Steven Liu
> >>
> >>
> >>
> >>
> > _______________________________________________
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> > 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
>
>
>
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