[FFmpeg-devel] [PATCH] avformat/hls: Fixes overwriting existing #EXT-X-PROGRAM-DATE-TIME value in HLS playlist
Vignesh Ravichandran
vignesh.ravichandran02 at gmail.com
Thu Nov 26 06:43:39 EET 2020
This check may not be enough. The below values would pass the check which
should not be the case:
20-11-26T08:34:00.000
2020-11-26T8:34:00.000
2020-11-26T08:60:00.000
2020-11-26T08:60:0.000
2020-13-26T08:34:00.000
The regex check approach mentioned earlier checks:
1. The value is in "YYYY-MM-DDThh:mm:ss.SSS" format (
https://tools.ietf.org/html/draft-pantos-http-live-streaming-23#section-4.3.2.6
)
2. The values for YYYY, MM, DD, hh, mm, ss, SSS are valid. For example: the
check would fail for MM = 00
On Thu, Nov 26, 2020 at 8:00 AM Steven Liu <lq at chinaffmpeg.org> wrote:
>
>
> > 2020年11月25日 下午9:57，Vignesh Ravichandran <
> vignesh.ravichandran02 at gmail.com> 写道：
> >
> > 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;
> > }
>
> Define a new function to check the value:
> 1. Split the string by ‘-‘
> 2. Check every value splited by ‘-‘
> 3. If the value is int, that is correct result.
> 4. Else not.
> >
> > 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)
> >>>>>
> >>>>> _______________________________________________
> >>>>> 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
> >>>>
> >>>>
> >>>>
> >>>>
> >>> _______________________________________________
> >>> 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
> >>
> >>
> >>
> >> _______________________________________________
> >> 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".
> > _______________________________________________
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> >
> > To unsubscribe, visit link above, or email
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>
> Thanks
>
> Steven Liu
>
>
>
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