[FFmpeg-devel] [PATCH 2/2] avcodec/utils: keep CORRUPT and TRUSTED packet flags when parsing packets

[Michael Niedermayer]

On Thu, Oct 11, 2018 at 12:50:53PM +0200, Michael Niedermayer wrote:
> On Wed, Oct 10, 2018 at 01:32:14AM +0200, Marton Balint wrote:
> > An FF_ macro got defined in avcodec.h to store the flags which need to be
> > propagated when parsers split packets so this won't be forgotten when a new
> > packet flag is introduced.
> > 
> > (I wonder if DISPOSABLE also fits here, or maybe some special handling is
> > needed like it is done for the keyframe flag?)
> > ---
> >  libavcodec/avcodec.h             | 9 ++++++++-
> >  libavcodec/version.h             | 2 +-
> >  libavformat/utils.c              | 2 +-
> >  tests/ref/fate/flv-demux         | 2 +-
> >  tests/ref/fate/iv8-demux         | 2 +-
> >  tests/ref/fate/segment-mp4-to-ts | 6 +++---
> >  tests/ref/fate/ts-demux          | 2 +-
> >  7 files changed, 16 insertions(+), 9 deletions(-)
> > 
> > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> > index 705a3ce4f3..9a3f9b6226 100644
> > --- a/libavcodec/avcodec.h
> > +++ b/libavcodec/avcodec.h
> > @@ -1493,7 +1493,14 @@ typedef struct AVPacket {
> >   * be discarded by the decoder.  I.e. Non-reference frames.
> >   */
> >  #define AV_PKT_FLAG_DISPOSABLE 0x0010
> > -
> > +/**
> > + * Packet flags which must always be kept when parsers split packets
> > + */
> > +#define FF_PKT_FLAGS_KEEP_WHEN_PARSING (\
> > +    AV_PKT_FLAG_CORRUPT | \
> > +    AV_PKT_FLAG_DISCARD | \
> > +    AV_PKT_FLAG_TRUSTED | \
> > +    0)
> >  
> >  enum AVSideDataParamChangeFlags {
> >      AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_COUNT  = 0x0001,
> > diff --git a/libavcodec/version.h b/libavcodec/version.h
> > index 97d134851f..79c5dc6773 100644
> > --- a/libavcodec/version.h
> > +++ b/libavcodec/version.h
> > @@ -29,7 +29,7 @@
> >  
> >  #define LIBAVCODEC_VERSION_MAJOR  58
> >  #define LIBAVCODEC_VERSION_MINOR  32
> > -#define LIBAVCODEC_VERSION_MICRO 100
> > +#define LIBAVCODEC_VERSION_MICRO 101
> >  
> >  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> >                                                 LIBAVCODEC_VERSION_MINOR, \
> > diff --git a/libavformat/utils.c b/libavformat/utils.c
> > index a8ac90213e..351bd88fa5 100644
> > --- a/libavformat/utils.c
> > +++ b/libavformat/utils.c
> > @@ -1511,7 +1511,7 @@ static int parse_packet(AVFormatContext *s, AVPacket *pkt, int stream_index)
> >          out_pkt.pts          = st->parser->pts;
> >          out_pkt.dts          = st->parser->dts;
> >          out_pkt.pos          = st->parser->pos;
> > -        out_pkt.flags       |= pkt->flags & AV_PKT_FLAG_DISCARD;
> > +        out_pkt.flags       |= pkt->flags & FF_PKT_FLAGS_KEEP_WHEN_PARSING;
> 
> I think this is wrong
> this looks like the packet flags are not passed through the parsers, so they would
> not neccessarily be attached to the correct packets, there could be a delay
> from a buffer ...
> 
> more so, these flags cannot be handled identically
> for example if there is output packet formed from concatenating a trusted and 
> untrusted input packet the output cannot be trusted because it is not just
> trusted data

btw, also consider 256 1 byte trusted packets, arbitrary combination of these
are not trusted, the order by which they are combined has to be trusted too


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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