Change to use arc4random_buf(3) if available

Signed-off-by: OBATA Akio <obache@wizdas.com>
(cherry picked from commit 027c45db6f)

config.h.cmake

@@ -185,6 +185,7 @@
 
 #cmakedefine HAVE_ARC4RANDOM 1
 #cmakedefine DEV_RANDOM "@DEV_RANDOM@"
+#cmakedefine HAVE_ARC4RANDOM_BUF 1
 
 #cmakedefine USE_PAM 1
 #cmakedefine TDM_PAM_SERVICE "@TDM_PAM_SERVICE@"

tdm/ConfigureChecks.cmake

@@ -98,6 +98,7 @@ if( NOT HAVE_ARC4RANDOM )
       set( DEV_RANDOM "/dev/random" CACHE INTERNAL "" FORCE )
     endif( )
 endif (NOT HAVE_ARC4RANDOM)
+check_function_exists( arc4random_buf HAVE_ARC4RANDOM_BUF )
 
 # Xau
 pkg_search_module( XAU xau )

tdm/backend/genauth.c

@@ -432,7 +432,10 @@ AddPreGetEntropy( void )
 int
 GenerateAuthData( char *auth, int len )
 {
-#ifdef HAVE_ARC4RANDOM
+#ifdef HAVE_ARC4RANDOM_BUF
+	arc4random_buf((void*)auth, (size_t)len);
+	return 1;
+#elif defined(HAVE_ARC4RANDOM)
 	int i;
 	unsigned *rnd = (unsigned *)auth;
 	if (sizeof(unsigned) == 4)