[PATCH] Mp4: fixed potential overflow in ngx_http_mp4_crop_stts_data()

[Roman Arutyunyan]

On Tue, May 31, 2022 at 12:05:13AM +0300, Maxim Dounin wrote:
> # HG changeset patch
> # User Maxim Dounin <mdounin at mdounin.ru>
> # Date 1653942033 -10800
> #      Mon May 30 23:20:33 2022 +0300
> # Node ID d5363be9fa61e0327574b8aa1342c874efd027b0
> # Parent  cd40709c91e245036e7f71a6c3e5190d9533be75
> Mp4: fixed potential overflow in ngx_http_mp4_crop_stts_data().
> 
> Both "count" and "duration" variables are 32-bit, so their product might
> potentially overflow.  It is used to reduce 64-bit start_time variable,
> and with very large start_time this can result in incorrect seeking.
> 
> Found by Coverity (CID 1499904).
> 
> diff --git a/src/http/modules/ngx_http_mp4_module.c b/src/http/modules/ngx_http_mp4_module.c
> --- a/src/http/modules/ngx_http_mp4_module.c
> +++ b/src/http/modules/ngx_http_mp4_module.c
> @@ -2331,7 +2331,7 @@ ngx_http_mp4_crop_stts_data(ngx_http_mp4
>          }
>  
>          start_sample += count;
> -        start_time -= count * duration;
> +        start_time -= (uint64_t) count * duration;
>          entries--;
>          entry++;
>      }

Looks fine