- markus@cvs.openbsd.org 2002/06/04 19:53:40

     [monitor.c]
     save the session id (hash) for ssh2 (it will be passed with the
     initial sign request) and verify that this value is used during
     authentication; ok provos@

1 files changed, 31 insertions, 7 deletions

diff --git a/monitor.c b/monitor.c
index 6fe0afd7e..a96ca04d5 100644
--- a/monitor.c
+++ b/monitor.c
@@ -25,7 +25,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: monitor.c,v 1.12 2002/06/04 19:42:35 markus Exp $");
+RCSID("$OpenBSD: monitor.c,v 1.13 2002/06/04 19:53:40 markus Exp $");
 
 #include <openssl/dh.h>
 
@@ -128,6 +128,8 @@ static int key_blobtype = MM_NOKEY;
 static u_char *hostbased_cuser = NULL;
 static u_char *hostbased_chost = NULL;
 static char *auth_method = "unknown";
+static int session_id2_len = 0;
+static u_char *session_id2 = NULL;
 
 struct mon_table {
         enum monitor_reqtype type;
@@ -454,6 +456,13 @@ mm_answer_sign(int socket, Buffer *m)
         if (datlen != 20)
                 fatal("%s: data length incorrect: %d", __FUNCTION__, datlen);
 
+        /* save session id, it will be passed on the first call */
+        if (session_id2_len == 0) {
+                session_id2_len = datlen;
+                session_id2 = xmalloc(session_id2_len);
+                memcpy(session_id2, p, session_id2_len);
+        }
+
         if ((key = get_hostkey_by_index(keyid)) == NULL)
                 fatal("%s: no hostkey from index %d", __FUNCTION__, keyid);
         if (key_sign(key, &signature, &siglen, p, datlen) < 0)
@@ -819,17 +828,25 @@ monitor_valid_userblob(u_char *data, u_int datalen)
         u_char *p;
         u_int len;
         int fail = 0;
-        int session_id2_len = 20 /*XXX should get from [net] */;
 
         buffer_init(&b);
         buffer_append(&b, data, datalen);
 
         if (datafellows & SSH_OLD_SESSIONID) {
+                p = buffer_ptr(&b);
+                len = buffer_len(&b);
+                if ((session_id2 == NULL) ||
+                    (len < session_id2_len) ||
+                    (memcmp(p, session_id2, session_id2_len) != 0))
+                        fail++;
                 buffer_consume(&b, session_id2_len);
         } else {
-                xfree(buffer_get_string(&b, &len));
-                if (len != session_id2_len)
+                p = buffer_get_string(&b, &len);
+                if ((session_id2 == NULL) ||
+                    (len != session_id2_len) ||
+                    (memcmp(p, session_id2, session_id2_len) != 0))
                         fail++;
+                xfree(p);
         }
         if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
                 fail++;
@@ -868,14 +885,17 @@ monitor_valid_hostbasedblob(u_char *data, u_int datalen, u_char *cuser,
         u_char *p;
         u_int len;
         int fail = 0;
-        int session_id2_len = 20 /*XXX should get from [net] */;
 
         buffer_init(&b);
         buffer_append(&b, data, datalen);
 
-        xfree(buffer_get_string(&b, &len));
-        if (len != session_id2_len)
+        p = buffer_get_string(&b, &len);
+        if ((session_id2 == NULL) ||
+            (len != session_id2_len) ||
+            (memcmp(p, session_id2, session_id2_len) != 0))
                 fail++;
+        xfree(p);
+
         if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
                 fail++;
         p = buffer_get_string(&b, NULL);
@@ -1334,6 +1354,10 @@ mm_get_kex(Buffer *m)
         kex = xmalloc(sizeof(*kex));
         memset(kex, 0, sizeof(*kex));
         kex->session_id = buffer_get_string(m, &kex->session_id_len);
+        if ((session_id2 == NULL) ||
+            (kex->session_id_len != session_id2_len) ||
+            (memcmp(kex->session_id, session_id2, session_id2_len) != 0))
+                fatal("mm_get_get: internal error: bad session id");
         kex->we_need = buffer_get_int(m);
         kex->server = 1;
         kex->hostkey_type = buffer_get_int(m);