[FFmpeg-devel] libavutil/encryption_info: Allow multiple init info.

[Michael Niedermayer]

On Mon, Apr 23, 2018 at 11:03:57AM -0700, Jacob Trimble wrote:
> While integrating my encryption info changes, I noticed a problem with
> the init info structs.  I implemented them as side-data on the Stream.
> But this means there can only be one per stream.  However, there can
> be multiple 'pssh' atoms in a single stream (e.g. for key rotation or
> multiple key systems). (sorry for not noticing sooner)
> 
> Attached is a patch to fix this by making the init info a
> singly-linked-list.  It is ABI compatible and is still easy to use and
> understand.  The alternative would be to break ABI and have the
> side-data methods return an array of pointers.  I could do that
> instead if that is preferable.

>  encryption_info.c |  154 +++++++++++++++++++++++++++++++++++-------------------
>  encryption_info.h |    5 +
>  2 files changed, 106 insertions(+), 53 deletions(-)
> e5eecc73a6997bbd11541771372d38ea9c3972a7  0001-libavutil-encryption_info-Allow-multiple-init-info.patch
> From bb941a77e882e93629d63d63059d0063b9519e29 Mon Sep 17 00:00:00 2001
> From: Jacob Trimble <modmaker at google.com>
> Date: Mon, 23 Apr 2018 10:33:58 -0700
> Subject: [PATCH] libavutil/encryption_info: Allow multiple init info.
> 
> It is possible for there to be multiple encryption init info structure.
> For example, to support multiple key systems or in key rotation.  This
> changes the AVEncryptionInitInfo struct to be a linked list so there
> can be multiple structs without breaking ABI.
> 
> Signed-off-by: Jacob Trimble <modmaker at google.com>
> ---
>  libavutil/encryption_info.c | 154 +++++++++++++++++++++++-------------
>  libavutil/encryption_info.h |   5 ++
>  2 files changed, 106 insertions(+), 53 deletions(-)
> 
> diff --git a/libavutil/encryption_info.c b/libavutil/encryption_info.c
> index 20a752d6b4..9935c10d74 100644
> --- a/libavutil/encryption_info.c
> +++ b/libavutil/encryption_info.c
> @@ -160,13 +160,16 @@ uint8_t *av_encryption_info_add_side_data(const AVEncryptionInfo *info, size_t *
>  }
>  
>  // The format of the AVEncryptionInitInfo side data:
> -// u32be system_id_size
> -// u32be num_key_ids
> -// u32be key_id_size
> -// u32be data_size
> -// u8[system_id_size] system_id
> -// u8[key_id_size][num_key_id] key_ids
> -// u8[data_size] data
> +// u32be init_info_count
> +// {
> +//   u32be system_id_size
> +//   u32be num_key_ids
> +//   u32be key_id_size
> +//   u32be data_size
> +//   u8[system_id_size] system_id
> +//   u8[key_id_size][num_key_id] key_ids
> +//   u8[data_size] data
> +// }[init_info_count]
>  
>  #define FF_ENCRYPTION_INIT_INFO_EXTRA 16
>  
> @@ -215,6 +218,7 @@ void av_encryption_init_info_free(AVEncryptionInitInfo *info)
>          for (i = 0; i < info->num_key_ids; i++) {
>              av_free(info->key_ids[i]);
>          }
> +        av_encryption_init_info_free(info->next);
>          av_free(info->system_id);
>          av_free(info->key_ids);
>          av_free(info->data);
> @@ -225,71 +229,115 @@ void av_encryption_init_info_free(AVEncryptionInitInfo *info)
>  AVEncryptionInitInfo *av_encryption_init_info_get_side_data(
>      const uint8_t *side_data, size_t side_data_size)
>  {
> -    AVEncryptionInitInfo *info;
> +    AVEncryptionInitInfo *ret = NULL, *info;
>      uint64_t system_id_size, num_key_ids, key_id_size, data_size, i;
> +    uint64_t init_info_count;
>  
> -    if (!side_data || side_data_size < FF_ENCRYPTION_INIT_INFO_EXTRA)
> -        return NULL;
> -
> -    system_id_size = AV_RB32(side_data);
[...]
> +    init_info_count = AV_RB32(side_data);

i may be missing something but this looks like the meaning of the first
field changes, this thus doesnt look compatible to me

also indention is quite inconsistent in the new code

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Many that live deserve death. And some that die deserve life. Can you give
it to them? Then do not be too eager to deal out death in judgement. For
even the very wise cannot see all ends. -- Gandalf
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