- deraadt@cvs.openbsd.org 2005/02/25 13:29:30

[openssh.git] / openbsd-compat / bsd-arc4random.c

diff --git a/openbsd-compat/bsd-arc4random.c b/openbsd-compat/bsd-arc4random.c
index 5cbb233afe5151b5c4df6b5d82f1e7da25692f47..d45fb182a6fb9725bb8794d7f7b947a8bf2f6c7a 100644 (file)
--- a/openbsd-compat/bsd-arc4random.c
+++ b/openbsd-compat/bsd-arc4random.c
@@ -15,9 +15,13 @@
  */
 
 #include "includes.h"
-#include "log.h"
 
-RCSID("$Id$");
+#include <sys/types.h>
+
+#include <string.h>
+#include <stdarg.h>
+
+#include "log.h"
 
 #ifndef HAVE_ARC4RANDOM
 
@@ -34,7 +38,8 @@ RCSID("$Id$");
 static int rc4_ready = 0;
 static RC4_KEY rc4;
 
-unsigned int arc4random(void)
+unsigned int
+arc4random(void)
 {
        unsigned int r = 0;
        static int first_time = 1;
@@ -53,16 +58,25 @@ unsigned int arc4random(void)
        return(r);
 }
 
-void arc4random_stir(void)
+void
+arc4random_stir(void)
 {
        unsigned char rand_buf[SEED_SIZE];
+       int i;
 
        memset(&rc4, 0, sizeof(rc4));
        if (RAND_bytes(rand_buf, sizeof(rand_buf)) <= 0)
                fatal("Couldn't obtain random bytes (error %ld)",
                    ERR_get_error());
        RC4_set_key(&rc4, sizeof(rand_buf), rand_buf);
-       RC4(&rc4, sizeof(rand_buf), rand_buf, rand_buf);
+
+       /*
+        * Discard early keystream, as per recommendations in:
+        * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
+        */
+       for(i = 0; i <= 256; i += sizeof(rand_buf))
+               RC4(&rc4, sizeof(rand_buf), rand_buf, rand_buf);
+
        memset(rand_buf, 0, sizeof(rand_buf));
 
        rc4_ready = REKEY_BYTES;