[FFmpeg-devel] [PATCH 1/2] avcodec/wrapped_avframe: implement wrapped_avframe decoder

[wm4]

On Tue, 10 Nov 2015 14:31:26 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Tue, Nov 10, 2015 at 04:54:17PM +0700, Muhammad Faiz wrote:
> > On Mon, Nov 9, 2015 at 11:22 PM, wm4 <nfxjfg at googlemail.com> wrote:  
> > > On Mon, 9 Nov 2015 08:03:54 -0800
> > > Muhammad Faiz <mfcc64 at gmail.com> wrote:
> > >  
> > >> From 4dcbda2e585404d2d79d5afcdc13fcb699f6f158 Mon Sep 17 00:00:00 2001
> > >> From: Muhammad Faiz <mfcc64 at gmail.com>
> > >> Date: Mon, 9 Nov 2015 15:55:13 +0700
> > >> Subject: [PATCH 1/2] avcodec/wrapped_avframe: implement wrapped_avframe
> > >>  decoder
> > >>
> > >> fix ticket #4985
> > >> for use in avdevice/lavfi
> > >> ---
> > >>  libavcodec/Makefile          |  1 +
> > >>  libavcodec/allcodecs.c       |  2 +-
> > >>  libavcodec/version.h         |  2 +-
> > >>  libavcodec/wrapped_avframe.c | 32 ++++++++++++++++++++++++++++++++
> > >>  4 files changed, 35 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> > >> index 68a573f..c60d512 100644
> > >> --- a/libavcodec/Makefile
> > >> +++ b/libavcodec/Makefile
> > >> @@ -577,6 +577,7 @@ OBJS-$(CONFIG_WMV2_ENCODER)            += wmv2enc.o wmv2.o \
> > >>                                            msmpeg4.o msmpeg4enc.o msmpeg4data.o
> > >>  OBJS-$(CONFIG_WNV1_DECODER)            += wnv1.o
> > >>  OBJS-$(CONFIG_WS_SND1_DECODER)         += ws-snd1.o
> > >> +OBJS-$(CONFIG_WRAPPED_AVFRAME_DECODER) += wrapped_avframe.o
> > >>  OBJS-$(CONFIG_WRAPPED_AVFRAME_ENCODER) += wrapped_avframe.o
> > >>  OBJS-$(CONFIG_XAN_DPCM_DECODER)        += dpcm.o
> > >>  OBJS-$(CONFIG_XAN_WC3_DECODER)         += xan.o
> > >> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> > >> index 9f60d7c..3260927 100644
> > >> --- a/libavcodec/allcodecs.c
> > >> +++ b/libavcodec/allcodecs.c
> > >> @@ -342,7 +342,7 @@ void avcodec_register_all(void)
> > >>      REGISTER_DECODER(VP9,               vp9);
> > >>      REGISTER_DECODER(VQA,               vqa);
> > >>      REGISTER_DECODER(WEBP,              webp);
> > >> -    REGISTER_ENCODER(WRAPPED_AVFRAME,   wrapped_avframe);
> > >> +    REGISTER_ENCDEC (WRAPPED_AVFRAME,   wrapped_avframe);
> > >>      REGISTER_ENCDEC (WMV1,              wmv1);
> > >>      REGISTER_ENCDEC (WMV2,              wmv2);
> > >>      REGISTER_DECODER(WMV3,              wmv3);
> > >> diff --git a/libavcodec/version.h b/libavcodec/version.h
> > >> index 1e21f15..5eecf5b 100644
> > >> --- a/libavcodec/version.h
> > >> +++ b/libavcodec/version.h
> > >> @@ -29,7 +29,7 @@
> > >>  #include "libavutil/version.h"
> > >>
> > >>  #define LIBAVCODEC_VERSION_MAJOR  57
> > >> -#define LIBAVCODEC_VERSION_MINOR  15
> > >> +#define LIBAVCODEC_VERSION_MINOR  16
> > >>  #define LIBAVCODEC_VERSION_MICRO 100
> > >>
> > >>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> > >> diff --git a/libavcodec/wrapped_avframe.c b/libavcodec/wrapped_avframe.c
> > >> index 13c8d8a..185a1a2 100644
> > >> --- a/libavcodec/wrapped_avframe.c
> > >> +++ b/libavcodec/wrapped_avframe.c
> > >> @@ -32,6 +32,8 @@
> > >>  #include "libavutil/buffer.h"
> > >>  #include "libavutil/pixdesc.h"
> > >>
> > >> +#if CONFIG_WRAPPED_AVFRAME_ENCODER
> > >> +
> > >>  static void wrapped_avframe_release_buffer(void *unused, uint8_t *data)
> > >>  {
> > >>      AVFrame *frame = (AVFrame *)data;
> > >> @@ -71,3 +73,33 @@ AVCodec ff_wrapped_avframe_encoder = {
> > >>      .encode2        = wrapped_avframe_encode,
> > >>      .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
> > >>  };
> > >> +
> > >> +#endif
> > >> +
> > >> +#if CONFIG_WRAPPED_AVFRAME_DECODER
> > >> +
> > >> +static int wrapped_avframe_decode(AVCodecContext *avctx, void *data,
> > >> +                                  int *got_frame, AVPacket *avpkt)
> > >> +{
> > >> +    int ret;
> > >> +
> > >> +    if (avpkt->size != sizeof(AVFrame))
> > >> +        return AVERROR(EINVAL);
> > >> +
> > >> +    if ((ret = av_frame_ref((AVFrame *) data, (AVFrame *) avpkt->data)) < 0)
> > >> +        return ret;
> > >> +
> > >> +    *got_frame = 1;
> > >> +    return avpkt->size;
> > >> +}
> > >> +
> > >> +AVCodec ff_wrapped_avframe_decoder = {
> > >> +    .name           = "wrapped_avframe",
> > >> +    .long_name      = NULL_IF_CONFIG_SMALL("AVFrame to AVPacket passthrough"),
> > >> +    .type           = AVMEDIA_TYPE_VIDEO,
> > >> +    .id             = AV_CODEC_ID_WRAPPED_AVFRAME,
> > >> +    .decode         = wrapped_avframe_decode,
> > >> +    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
> > >> +};
> > >> +
> > >> +#endif  
> > >
> > > This is very dangerous. You get potentially security relevant bad
> > > behavior if you get anyone to force a demuxer/decoder on an untrusted
> > > input file.  
> > 
> > OK, this makes segfault on my machine (120 = sizeof(AVFrame)/4 on my machine)
> > ffmpeg -codec wrapped_avframe  -pixel_format rgba -f rawvideo -s 120x1
> > -i input.mkv -f null -y /dev/null  
> 
> maybe in addition to any other saftey features
> "-codec wrapped_avframe" could be checked for and forbidden in
> libavformat, or does this have any safe use ?

You could argue that API users can expect that there will be no
security or stability issues even if they let an user decide with which
codec to initialize a AVCodecContext.

I'm unsure to what extent we want to fulfill such expectations.