- markus@cvs.openbsd.org 2002/03/26 23:14:51

     [kex.c]
     generate a new cookie for each SSH2_MSG_KEXINIT message we send out

2 files changed, 26 insertions, 9 deletions

diff --git a/ChangeLog b/ChangeLog
index 3bf991d65..7eb915bda 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -20,6 +20,9 @@
    - markus@cvs.openbsd.org 2002/03/26 23:13:03
      [auth-rsa.c]
      disallow RSA keys < 768 for protocol 1, too (rhosts-rsa and rsa auth)
+   - markus@cvs.openbsd.org 2002/03/26 23:14:51
+     [kex.c]
+     generate a new cookie for each SSH2_MSG_KEXINIT message we send out
 
 20020325
  - (stevesk) import OpenBSD <sys/tree.h> as "openbsd-compat/tree.h"
@@ -8083,4 +8086,4 @@
  - Wrote replacements for strlcpy and mkdtemp
  - Released 1.0pre1
 
-$Id: ChangeLog,v 1.1999 2002/03/27 17:38:43 mouring Exp $
+$Id: ChangeLog,v 1.2000 2002/03/27 17:42:57 mouring Exp $
diff --git a/kex.c b/kex.c
index 8097ab0f2..194a865ad 100644
--- a/kex.c
+++ b/kex.c
@@ -23,7 +23,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: kex.c,v 1.48 2002/03/18 17:50:31 provos Exp $");
+RCSID("$OpenBSD: kex.c,v 1.49 2002/03/26 23:14:51 markus Exp $");
 
 #include <openssl/crypto.h>
 
@@ -57,16 +57,15 @@ static void kex_choose_conf(Kex *);
 static void
 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
 {
-        u_int32_t rand = 0;
         int i;
 
         buffer_clear(b);
-        for (i = 0; i < KEX_COOKIE_LEN; i++) {
-                if (i % 4 == 0)
-                        rand = arc4random();
-                buffer_put_char(b, rand & 0xff);
-                rand >>= 8;
-        }
+        /*
+         * add a dummy cookie, the cookie will be overwritten by
+         * kex_send_kexinit(), each time a kexinit is set
+         */
+        for (i = 0; i < KEX_COOKIE_LEN; i++)
+                buffer_put_char(b, 0);
         for (i = 0; i < PROPOSAL_MAX; i++)
                 buffer_put_cstring(b, proposal[i]);
         buffer_put_char(b, 0);                  /* first_kex_packet_follows */
@@ -152,6 +151,10 @@ kex_finish(Kex *kex)
 void
 kex_send_kexinit(Kex *kex)
 {
+        u_int32_t rand = 0;
+        u_char *cookie;
+        int i;
+
         if (kex == NULL) {
                 error("kex_send_kexinit: no kex, cannot rekey");
                 return;
@@ -161,6 +164,17 @@ kex_send_kexinit(Kex *kex)
                 return;
         }
         kex->done = 0;
+
+        /* generate a random cookie */
+        if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
+                fatal("kex_send_kexinit: kex proposal too short");
+        cookie = buffer_ptr(&kex->my);
+        for (i = 0; i < KEX_COOKIE_LEN; i++) {
+                if (i % 4 == 0)
+                        rand = arc4random();
+                cookie[i] = rand;
+                rand >>= 8;
+        }
         packet_start(SSH2_MSG_KEXINIT);
         packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
         packet_send();