[FFmpeg-devel,2/2] avcodec/zmbv: Check that the decompressed data is large enough to contain MVs or an intra frame

Submitted by Michael Niedermayer on Sept. 17, 2018, 7:34 p.m.

Details

Message ID 20180917193400.3276-2-michael@niedermayer.cc
State New
Headers show

Commit Message

Michael Niedermayer Sept. 17, 2018, 7:34 p.m.
Fixes: Timeout
Fixes: 10182/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZMBV_fuzzer-6245951174344704

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/zmbv.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Comments

Paul B Mahol Sept. 17, 2018, 7:39 p.m.
On 9/17/18, Michael Niedermayer <michael@niedermayer.cc> wrote:
> Fixes: Timeout
> Fixes:
> 10182/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZMBV_fuzzer-6245951174344704
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/zmbv.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/zmbv.c b/libavcodec/zmbv.c
> index 177993d0a6..0c2daf47c2 100644
> --- a/libavcodec/zmbv.c
> +++ b/libavcodec/zmbv.c
> @@ -409,6 +409,7 @@ static int decode_frame(AVCodecContext *avctx, void
> *data, int *got_frame, AVPac
>      int zret = Z_OK; // Zlib return code
>      int len = buf_size;
>      int hi_ver, lo_ver, ret;
> +    int min_size;
>
>      /* parse header */
>      if (len < 1)
> @@ -510,7 +511,11 @@ static int decode_frame(AVCodecContext *avctx, void
> *data, int *got_frame, AVPac
>          memset(c->prev, 0, avctx->width * avctx->height * (c->bpp / 8));
>          c->decode_intra= decode_intra;
>      }
> -
> +    if (c->flags & ZMBV_KEYFRAME) {
> +        min_size = avctx->width * avctx->height * (c->bpp / 8);

Do you have proof this is really minimal possible thing zlib can
compress single frame?
If not, Drop. It.

> +    } else {
> +        min_size = (c->bx * c->by * 2 + 3) & ~3;
> +    }
>      if (!c->decode_intra) {
>          av_log(avctx, AV_LOG_ERROR, "Error! Got no format or no
> keyframe!\n");
>          return AVERROR_INVALIDDATA;
> @@ -539,6 +544,10 @@ static int decode_frame(AVCodecContext *avctx, void
> *data, int *got_frame, AVPac
>          }
>          c->decomp_len = c->zstream.total_out;
>      }
> +    if (min_size > c->decomp_len) {
> +        av_log(avctx, AV_LOG_ERROR, "input too small\n");
> +        return AVERROR_INVALIDDATA;
> +    }
>      if (c->flags & ZMBV_KEYFRAME) {
>          frame->key_frame = 1;
>          frame->pict_type = AV_PICTURE_TYPE_I;
> --
> 2.18.0
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
Michael Niedermayer Sept. 17, 2018, 9:51 p.m.
On Mon, Sep 17, 2018 at 09:34:00PM +0200, Michael Niedermayer wrote:
> Fixes: Timeout
> Fixes: 10182/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZMBV_fuzzer-6245951174344704
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/zmbv.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)

will submit a slightly different solution based on discussion with
durandal on IRC

[...]

Patch hide | download patch | download mbox

diff --git a/libavcodec/zmbv.c b/libavcodec/zmbv.c
index 177993d0a6..0c2daf47c2 100644
--- a/libavcodec/zmbv.c
+++ b/libavcodec/zmbv.c
@@ -409,6 +409,7 @@  static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
     int zret = Z_OK; // Zlib return code
     int len = buf_size;
     int hi_ver, lo_ver, ret;
+    int min_size;
 
     /* parse header */
     if (len < 1)
@@ -510,7 +511,11 @@  static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
         memset(c->prev, 0, avctx->width * avctx->height * (c->bpp / 8));
         c->decode_intra= decode_intra;
     }
-
+    if (c->flags & ZMBV_KEYFRAME) {
+        min_size = avctx->width * avctx->height * (c->bpp / 8);
+    } else {
+        min_size = (c->bx * c->by * 2 + 3) & ~3;
+    }
     if (!c->decode_intra) {
         av_log(avctx, AV_LOG_ERROR, "Error! Got no format or no keyframe!\n");
         return AVERROR_INVALIDDATA;
@@ -539,6 +544,10 @@  static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
         }
         c->decomp_len = c->zstream.total_out;
     }
+    if (min_size > c->decomp_len) {
+        av_log(avctx, AV_LOG_ERROR, "input too small\n");
+        return AVERROR_INVALIDDATA;
+    }
     if (c->flags & ZMBV_KEYFRAME) {
         frame->key_frame = 1;
         frame->pict_type = AV_PICTURE_TYPE_I;