[nginx] Mp4: fixed potential overflow in ngx_http_mp4_crop_stts_data().

[Sergey Kandaurov]

details:   https://hg.nginx.org/nginx/rev/1afd19dc7161
branches:  
changeset: 8043:1afd19dc7161
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Tue Jun 07 21:58:52 2022 +0300
description:
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).

diffstat:

 src/http/modules/ngx_http_mp4_module.c |  2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diffs (12 lines):

diff -r c7e25324be11 -r 1afd19dc7161 src/http/modules/ngx_http_mp4_module.c
--- a/src/http/modules/ngx_http_mp4_module.c	Tue Jun 07 20:08:57 2022 +0400
+++ b/src/http/modules/ngx_http_mp4_module.c	Tue Jun 07 21:58:52 2022 +0300
@@ -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++;
     }