nuv: check RTjpeg header for validity

CC: libav-stable@libav.org

libavcodec/nuv.c

@@ -184,17 +184,18 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     }
     if (c->codec_frameheader) {
         int w, h, q;
-        if (buf_size < 12) {
+        if (buf_size < RTJPEG_HEADER_SIZE || buf[4] != RTJPEG_HEADER_SIZE ||
+            buf[5] != RTJPEG_FILE_VERSION) {
             av_log(avctx, AV_LOG_ERROR, "invalid nuv video frame\n");
-            return -1;
+            return AVERROR_INVALIDDATA;
         }
         w = AV_RL16(&buf[6]);
         h = AV_RL16(&buf[8]);
         q = buf[10];
         if (!codec_reinit(avctx, w, h, q))
             return -1;
-        buf = &buf[12];
+        buf = &buf[RTJPEG_HEADER_SIZE];
-        buf_size -= 12;
+        buf_size -= RTJPEG_HEADER_SIZE;
     }
 
     if (keyframe && c->pic.data[0])

libavcodec/rtjpeg.h

@@ -25,6 +25,9 @@
 #include <stdint.h>
 #include "dsputil.h"
 
+#define RTJPEG_FILE_VERSION 0
+#define RTJPEG_HEADER_SIZE 12
+
 typedef struct {
     int w, h;
     DSPContext *dsp;