- 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

diff --git a/ChangeLog b/ChangeLog
index 9b842257e4070ffeab66433e9ba70b94052cd6fd..e08bba778a1c926e831d7d5136d28986a2c4b6b2 100644 (file)
--- 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"

diff --git a/kex.c b/kex.c
index 8097ab0f26348633d9e6bab58298b9d96b27995c..194a865ad9dfa7797e747c0631c3e3b463c6795c 100644 (file)
--- 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();