[PATCH:libXdmcp] Use arc4random when available to produce the XDM-AUTHENTICATION1 key

[Matthieu Herrb]

arc4random() and associated functions can be found in libbsd on
GNU/Linux systems.

Signed-off-by: Matthieu Herrb <matthieu.herrb at laas.fr>
---
 Key.c        | 10 ++++++++++
 configure.ac |  3 ++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git Key.c Key.c
index aa4add6..a09b316 100644
--- Key.c
+++ Key.c
@@ -32,6 +32,11 @@ in this Software without prior written authorization from The Open Group.
 #include <X11/Xmd.h>
 #include <X11/Xdmcp.h>
 
+#ifdef HAVE_LIBBSD
+#include <bsd/stdlib.h> /* for arc4random_buf() */
+#endif
+
+#ifndef HAVE_ARC4RANDOM_BUF
 static void
 getbits (long data, unsigned char *dst)
 {
@@ -40,6 +45,7 @@ getbits (long data, unsigned char *dst)
     dst[2] = (data >> 16) & 0xff;
     dst[3] = (data >> 24) & 0xff;
 }
+#endif
 
 #define Time_t time_t
 
@@ -59,6 +65,7 @@ getbits (long data, unsigned char *dst)
 void
 XdmcpGenerateKey (XdmAuthKeyPtr key)
 {
+#ifndef HAVE_ARC4RANDOM_BUF
     long    lowbits, highbits;
 
     srandom ((int)getpid() ^ time((Time_t *)0));
@@ -66,6 +73,9 @@ XdmcpGenerateKey (XdmAuthKeyPtr key)
     highbits = random ();
     getbits (lowbits, key->data);
     getbits (highbits, key->data + 4);
+#else
+    arc4random_buf(key->data, 8);
+#endif
 }
 
 int
diff --git configure.ac configure.ac
index 08c046a..d8ddfae 100644
--- configure.ac
+++ configure.ac
@@ -53,7 +53,8 @@ AC_PROG_LN_S
 AC_SEARCH_LIBS([recvfrom],[socket])
 
 # Checks for library functions.
-AC_CHECK_FUNCS([srand48 lrand48])
+AC_CHECK_LIB([bsd], [arc4random_buf])
+AC_CHECK_FUNCS([srand48 lrand48 arc4random_buf])
 
 # Obtain compiler/linker options for depedencies
 PKG_CHECK_MODULES(XDMCP, xproto)
-- 
1.8.3.1