shorten: Use a checked bytestream reader for the wave header

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/shorten.c

@@ -202,31 +202,34 @@ static int decode_wave_header(AVCodecContext *avctx, const uint8_t *header,
 {
     int len;
     short wave_format;
+    GetByteContext gb;
 
-    if (bytestream_get_le32(&header) != MKTAG('R', 'I', 'F', 'F')) {
+    bytestream2_init(&gb, header, header_size);
+
+    if (bytestream2_get_le32(&gb) != MKTAG('R', 'I', 'F', 'F')) {
         av_log(avctx, AV_LOG_ERROR, "missing RIFF tag\n");
         return AVERROR_INVALIDDATA;
     }
 
-    header += 4; /* chunk size */
+    bytestream2_skip(&gb, 4); /* chunk size */
 
-    if (bytestream_get_le32(&header) != MKTAG('W', 'A', 'V', 'E')) {
+    if (bytestream2_get_le32(&gb) != MKTAG('W', 'A', 'V', 'E')) {
         av_log(avctx, AV_LOG_ERROR, "missing WAVE tag\n");
         return AVERROR_INVALIDDATA;
     }
 
-    while (bytestream_get_le32(&header) != MKTAG('f', 'm', 't', ' ')) {
-        len     = bytestream_get_le32(&header);
-        header += len;
+    while (bytestream2_get_le32(&gb) != MKTAG('f', 'm', 't', ' ')) {
+        len = bytestream2_get_le32(&gb);
+        bytestream2_skip(&gb, len);
     }
-    len = bytestream_get_le32(&header);
+    len = bytestream2_get_le32(&gb);
 
     if (len < 16) {
         av_log(avctx, AV_LOG_ERROR, "fmt chunk was too short\n");
         return AVERROR_INVALIDDATA;
     }
 
-    wave_format = bytestream_get_le16(&header);
+    wave_format = bytestream2_get_le16(&gb);
 
     switch (wave_format) {
     case WAVE_FORMAT_PCM:
@@ -236,11 +239,11 @@ static int decode_wave_header(AVCodecContext *avctx, const uint8_t *header,
         return AVERROR(ENOSYS);
     }
 
-    header += 2;        // skip channels    (already got from shorten header)
-    avctx->sample_rate = bytestream_get_le32(&header);
-    header += 4;        // skip bit rate    (represents original uncompressed bit rate)
-    header += 2;        // skip block align (not needed)
-    avctx->bits_per_coded_sample = bytestream_get_le16(&header);
+    bytestream2_skip(&gb, 2); // skip channels    (already got from shorten header)
+    avctx->sample_rate = bytestream2_get_le32(&gb);
+    bytestream2_skip(&gb, 4); // skip bit rate    (represents original uncompressed bit rate)
+    bytestream2_skip(&gb, 2); // skip block align (not needed)
+    avctx->bits_per_coded_sample = bytestream2_get_le16(&gb);
 
     if (avctx->bits_per_coded_sample != 16) {
         av_log(avctx, AV_LOG_ERROR, "unsupported number of bits per sample\n");