Re: [FFmpeg-devel] [PATCH v2] avcodec/dovi_rpu: verify RPU data CRC32

From: quietvoid <tcchlisop0@gmail.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH v2] avcodec/dovi_rpu: verify RPU data CRC32
Date: Wed, 9 Aug 2023 13:47:34 -0400
Message-ID: <45a00076-f535-433b-931d-7e85c216bb82@gmail.com> (raw)
In-Reply-To: <b2deb32b-f24e-fa22-1e95-dc6151674166@gmail.com>

On 09/08/2023 13.08, James Almer wrote:
> On 8/9/2023 2:05 PM, quietvoid wrote:
>> 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 | 45 ++++++++++++++++++++++++++++++++++++++++---
>>   libavcodec/dovi_rpu.h |  3 ++-
>>   libavcodec/hevcdec.c  |  3 ++-
>>   3 files changed, 46 insertions(+), 5 deletions(-)
>>
>> diff --git a/libavcodec/dovi_rpu.c b/libavcodec/dovi_rpu.c
>> index dd38936552..9ada0aceec 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 +460,26 @@ 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 */
>> +    /* Skip unsupported until CRC32 */
>> +    skip_bits_long(gb, get_bits_left(gb) - 32);
>
> This can be done after the err_recognition check.
>
>> +
>> +    if (err_recognition & AV_EF_CRCCHECK) {
>
> Do instead
>
> if (!(err_recognition & AV_EF_CRCCHECK))
>     return 0;
>
> To remove one level of indentation.
Thanks, sent v3: 
https://ffmpeg.org/pipermail/ffmpeg-devel/2023-August/313141.html
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