ffv1dec: check that global parameters do not change in version 0/1

Such changes are neither allowed nor supported

Found-by: ami_stuff
Bug-Id: CVE-2013-7020
CC: libav-stable@libav.org
Signed-off-by: Anton Khirnov <anton@khirnov.net>
(cherry picked from commit da7d839a0d3ec40423a665dc85e0cfaed3f92eb8)
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Conflicts:
	libavcodec/ffv1dec.c

1 files changed, 36 insertions, 11 deletions

diff --git a/libavcodec/ffv1.c b/libavcodec/ffv1.c
index 917f40d1bc..5e798883b6 100644
--- a/libavcodec/ffv1.c
+++ b/libavcodec/ffv1.c
@@ -1518,20 +1518,45 @@ static int read_header(FFV1Context *f){
     memset(state, 128, sizeof(state));
 
     if(f->version < 2){
-        f->version= get_symbol(c, state, 0);
-        f->ac= f->avctx->coder_type= get_symbol(c, state, 0);
-        if(f->ac>1){
-            for(i=1; i<256; i++){
-                f->state_transition[i]= get_symbol(c, state, 1) + c->one_state[i];
-            }
+        int chroma_h_shift, chroma_v_shift, colorspace, bits_per_raw_sample;
+        unsigned v = get_symbol(c, state, 0);
+        if (v > 1) {
+            av_log(f->avctx, AV_LOG_ERROR,
+                   "invalid version %d in version 1 header\n", v);
+            return AVERROR_INVALIDDATA;
         }
-        f->colorspace= get_symbol(c, state, 0); //YUV cs type
-        if(f->version>0)
-            f->avctx->bits_per_raw_sample= get_symbol(c, state, 0);
+        f->version = v;
+
+        f->ac = f->avctx->coder_type = get_symbol(c, state, 0);
+
+        if (f->ac > 1) {
+            for (i = 1; i < 256; i++)
+                f->state_transition[i] =
+                    get_symbol(c, state, 1) + c->one_state[i];
+        }
+
+        colorspace          = get_symbol(c, state, 0); //YUV cs type
+        bits_per_raw_sample = f->version > 0 ? get_symbol(c, state, 0) : f->avctx->bits_per_raw_sample;
         get_rac(c, state); //no chroma = false
-        f->chroma_h_shift= get_symbol(c, state, 0);
-        f->chroma_v_shift= get_symbol(c, state, 0);
+        chroma_h_shift      = get_symbol(c, state, 0);
+        chroma_v_shift      = get_symbol(c, state, 0);
         get_rac(c, state); //transparency plane
+
+        if (f->plane_count) {
+            if (colorspace          != f->colorspace                 ||
+                bits_per_raw_sample != f->avctx->bits_per_raw_sample ||
+                chroma_h_shift      != f->chroma_h_shift             ||
+                chroma_v_shift      != f->chroma_v_shift) {
+                av_log(f->avctx, AV_LOG_ERROR, "Invalid change of global parameters\n");
+                return AVERROR_INVALIDDATA;
+            }
+        }
+
+        f->colorspace                 = colorspace;
+        f->avctx->bits_per_raw_sample = bits_per_raw_sample;
+        f->chroma_h_shift             = chroma_h_shift;
+        f->chroma_v_shift             = chroma_v_shift;
+
         f->plane_count= 2;
     }