[FFmpeg-devel] [PATCH v3] avcodec/dovi_rpu: verify RPU data CRC32

[quietvoid <tcchlisop0@gmail.com>]

The Dolby Vision RPU contains a CRC32 to validate the payload against.
The implementation is CRC32/MPEG-2.

The CRC is only verified with the AV_EF_CRCCHECK flag.

Signed-off-by: quietvoid <tcChlisop0@gmail.com>
---
 libavcodec/dovi_rpu.c | 46 ++++++++++++++++++++++++++++++++++++++++---
 libavcodec/dovi_rpu.h |  3 ++-
 libavcodec/hevcdec.c  |  3 ++-
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/libavcodec/dovi_rpu.c b/libavcodec/dovi_rpu.c
index dd38936552..1dfeee7564 100644
--- a/libavcodec/dovi_rpu.c
+++ b/libavcodec/dovi_rpu.c
@@ -22,6 +22,7 @@
  */
 
 #include "libavutil/buffer.h"
+#include "libavutil/crc.h"
 
 #include "dovi_rpu.h"
 #include "golomb.h"
@@ -191,13 +192,17 @@ static inline int64_t get_se_coef(GetBitContext *gb, const AVDOVIRpuDataHeader *
         }                                                                       \
     } while (0)
 
-int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size)
+int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size,
+                      int err_recognition)
 {
     AVDOVIRpuDataHeader *hdr = &s->header;
     GetBitContext *gb = &(GetBitContext){0};
     DOVIVdrRef *vdr;
     int ret;
 
+    size_t actual_rpu_size;
+    uint8_t trailing_zeroes = 0;
+
     uint8_t nal_prefix;
     uint8_t rpu_type;
     uint8_t vdr_seq_info_present;
@@ -205,7 +210,22 @@ int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size)
     uint8_t use_prev_vdr_rpu;
     uint8_t use_nlq;
     uint8_t profile;
-    if ((ret = init_get_bits8(gb, rpu, rpu_size)) < 0)
+
+    uint32_t rpu_data_crc32;
+    uint32_t computed_crc32;
+
+    for (int i = rpu_size - 1; i > 0; i--) {
+        if (!rpu[i]) {
+            trailing_zeroes++;
+        } else {
+            break;
+        }
+    }
+
+    actual_rpu_size = rpu_size - trailing_zeroes;
+
+    /* Exclude trailing byte (0x80) from reader */
+    if ((ret = init_get_bits8(gb, rpu, actual_rpu_size - 1)) < 0)
         return ret;
 
     /* RPU header, common values */
@@ -440,7 +460,27 @@ int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size)
         color->source_diagonal = get_bits(gb, 10);
     }
 
-    /* FIXME: verify CRC32, requires implementation of AV_CRC_32_MPEG_2 */
+    if (!(err_recognition & AV_EF_CRCCHECK))
+        return 0;
+
+    /* Skip unsupported until CRC32 */
+    skip_bits_long(gb, get_bits_left(gb) - 32);
+
+    rpu_data_crc32 = get_bits_long(gb, 32);
+
+    /* Verify CRC32, buffer excludes the prefix, CRC32 and trailing byte */
+    computed_crc32 = av_bswap32(av_crc(av_crc_get_table(AV_CRC_32_IEEE),
+                                       -1, rpu + 1, actual_rpu_size - 6));
+
+    if (rpu_data_crc32 != computed_crc32) {
+        av_log(s->logctx, AV_LOG_ERROR,
+               "RPU CRC mismatch! Expected %"PRIu32", received %"PRIu32"\n",
+               rpu_data_crc32, computed_crc32);
+
+        if (err_recognition & AV_EF_EXPLODE)
+            goto fail;
+    }
+
     return 0;
 
 fail:
diff --git a/libavcodec/dovi_rpu.h b/libavcodec/dovi_rpu.h
index f6ca5bbbc5..2b993a72c6 100644
--- a/libavcodec/dovi_rpu.h
+++ b/libavcodec/dovi_rpu.h
@@ -77,7 +77,8 @@ void ff_dovi_update_cfg(DOVIContext *s, const AVDOVIDecoderConfigurationRecord *
  *
  * Returns 0 or an error code.
  */
-int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size);
+int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size,
+                      int err_recognition);
 
 /**
  * Attach the decoded AVDOVIMetadata as side data to an AVFrame.
diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index df40c91ba6..81b1a84625 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -3182,7 +3182,8 @@ static int decode_nal_units(HEVCContext *s, const uint8_t *buf, int length)
             return AVERROR(ENOMEM);
         memcpy(s->rpu_buf->data, nal->raw_data + 2, nal->raw_size - 2);
 
-        ret = ff_dovi_rpu_parse(&s->dovi_ctx, nal->data + 2, nal->size - 2);
+        ret = ff_dovi_rpu_parse(&s->dovi_ctx, nal->data + 2, nal->size - 2,
+                                s->avctx->err_recognition);
         if (ret < 0) {
             av_buffer_unref(&s->rpu_buf);
             av_log(s->avctx, AV_LOG_WARNING, "Error parsing DOVI NAL unit.\n");
-- 
2.41.0

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