omadec: check GEOB sizes against buffer size

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: David Goldwich <david.goldwich@gmail.com>
CC:libav-stable@libav.org
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/omadec.c

@@ -237,6 +237,11 @@ static int decrypt_init(AVFormatContext *s, ID3v2ExtraMeta *em, uint8_t *header)
         av_log(s, AV_LOG_ERROR, "Invalid encryption header\n");
         return AVERROR_INVALIDDATA;
     }
+    if (OMA_ENC_HEADER_SIZE + oc->k_size + oc->e_size + oc->i_size + 8 > geob->datasize ||
+        OMA_ENC_HEADER_SIZE + 48 > geob->datasize) {
+        av_log(s, AV_LOG_ERROR, "Too little GEOB data\n");
+        return AVERROR_INVALIDDATA;
+    }
     oc->rid = AV_RB32(&gdata[OMA_ENC_HEADER_SIZE + 28]);
     av_log(s, AV_LOG_DEBUG, "RID: %.8x\n", oc->rid);