[FFmpeg-devel] [PATCH 1/3] avformat/mov: Increase support for common encryption.

[James Almer]

On 1/5/2018 4:49 PM, Jacob Trimble wrote:
> diff --git a/libavutil/aes_ctr.c b/libavutil/aes_ctr.c
> index e9c568fe0d..6ed69c8e10 100644
> --- a/libavutil/aes_ctr.c
> +++ b/libavutil/aes_ctr.c
> @@ -38,10 +38,9 @@ struct AVAESCTR *av_aes_ctr_alloc(void)
>      return av_mallocz(sizeof(struct AVAESCTR));
>  }
>  
> -void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
> +void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
>  {
> -    memcpy(a->counter, iv, AES_CTR_IV_SIZE);
> -    memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
> +    memcpy(a->counter, iv, sizeof(a->counter));
>      a->block_offset = 0;
>  }
>  
> @@ -52,12 +51,14 @@ const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
>  
>  void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
>  {
> -    uint32_t iv[2];
> +    uint32_t iv[4];
>  
>      iv[0] = av_get_random_seed();
>      iv[1] = av_get_random_seed();
> +    iv[2] = 0;
> +    iv[3] = 0;
>  
> -    av_aes_ctr_set_iv(a, (uint8_t*)iv);
> +    av_aes_ctr_set_full_iv(a, (uint8_t*)iv);
>  }
>  
>  int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
> diff --git a/libavutil/aes_ctr.h b/libavutil/aes_ctr.h
> index f596fa6a46..5995b37bec 100644
> --- a/libavutil/aes_ctr.h
> +++ b/libavutil/aes_ctr.h
> @@ -67,9 +67,9 @@ const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a);
>  void av_aes_ctr_set_random_iv(struct AVAESCTR *a);
>  
>  /**
> - * Forcefully change the iv
> + * Forcefully change the "full" 16-byte iv, including the counter
>   */
> -void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv);
> +void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv);
>  
>  /**
>   * Increment the top 64 bit of the iv (performed after each frame)

You can't remove API just like that without a deprecation period.
Add a new av_aes_ctr_set_full_iv() function, and either leave
av_aes_ctr_set_iv() alone or deprecate it if it effectively becomes
superfluous after adding the new function.

Also, this patch needs to be split in three. One for the aes_crt
changes, one for the encryption_info changes, and one for mov changes,
with a minor libavutil version bump for the former two, and the
corresponding APIChanges entry.
Alternatively, you could also squash the new encryption_info API from
this patch into the one that actually introduces the entire feature.