[FFmpeg-devel] [PATCH 1/2] avformat/hlsenc: fall back to av_get_random_seed() when generating AES128 key

[James Almer]

On 7/2/2023 4:30 PM, Marton Balint wrote:
> It should be OK to use av_get_random_seed() to generate the key instead of
> using openSSL/Gcrypt functions. This removes the hard dependancy of those libs
> for key generation functionality.
> 
> Fixes ticket #10441.
> 
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>   libavformat/hlsenc.c | 18 ++++++++----------
>   1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index 1e0848ce3d..0b22c71186 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -40,6 +40,7 @@
>   #include "libavutil/intreadwrite.h"
>   #include "libavutil/opt.h"
>   #include "libavutil/log.h"
> +#include "libavutil/random_seed.h"
>   #include "libavutil/time.h"
>   #include "libavutil/time_internal.h"
>   
> @@ -710,18 +711,18 @@ fail:
>       return ret;
>   }
>   
> -static int randomize(uint8_t *buf, int len)
> +static void randomize(uint8_t *buf, int len)
>   {
>   #if CONFIG_GCRYPT
>       gcry_randomize(buf, len, GCRY_VERY_STRONG_RANDOM);
> -    return 0;
> +    return;
>   #elif CONFIG_OPENSSL
>       if (RAND_bytes(buf, len))
> -        return 0;
> -#else
> -    return AVERROR(ENOSYS);
> +        return;
>   #endif
> -    return AVERROR(EINVAL);
> +    av_assert0(len % 4 == 0);
> +    for (int i = 0; i < len; i += 4)
> +        AV_WB32(buf + i, av_get_random_seed());

Maybe instead use a PRNG, like the following:

AVLFG c;
av_lfg_init(&c, av_get_random_seed());
for (int i = 0; i < len; i += 4)
     AV_WB32(buf + i, av_lfg_get(&c));