[FFmpeg-devel] [PATCH 1/2] avutil/random_seed: use arc4random() when available

[Ganesh Ajjanagadde]

arc4random() was designed as a superior interface for system random
number generation, designed for OpenBSD. It is thus an improvement to
use it whenever available.

As a side note, this may or may not get included in glibc, and there is
a proposal to create a posix_random family based on these ideas:
http://austingroupbugs.net/view.php?id=859.

Untested as I lack OpenBSD.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
---
 configure               | 2 ++
 libavutil/random_seed.c | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/configure b/configure
index 7530c88..e676269 100755
--- a/configure
+++ b/configure
@@ -1840,6 +1840,7 @@ MATH_FUNCS="
 SYSTEM_FUNCS="
     access
     aligned_malloc
+    arc4random
     clock_gettime
     closesocket
     CommandLineToArgvW
@@ -5218,6 +5219,7 @@ check_func  ${malloc_prefix}memalign            && enable memalign
 check_func  ${malloc_prefix}posix_memalign      && enable posix_memalign
 
 check_func  access
+check_func  arc4random
 check_func_headers time.h clock_gettime || { check_func_headers time.h clock_gettime -lrt && add_extralibs -lrt && LIBRT="-lrt"; }
 check_func  fcntl
 check_func  fork
diff --git a/libavutil/random_seed.c b/libavutil/random_seed.c
index 8aa8c38..205a636 100644
--- a/libavutil/random_seed.c
+++ b/libavutil/random_seed.c
@@ -121,6 +121,10 @@ uint32_t av_get_random_seed(void)
     }
 #endif
 
+#if HAVE_ARC4RANDOM
+    return arc4random();
+#endif
+
     if (read_random(&seed, "/dev/urandom") == sizeof(seed))
         return seed;
     if (read_random(&seed, "/dev/random")  == sizeof(seed))
-- 
2.6.3