1 files changed, 38 insertions, 19 deletions

diff --git a/sshd.c b/sshd.c
index d46e4aa8b..02fe2ec42 100644
--- a/sshd.c
+++ b/sshd.c
@@ -40,7 +40,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: sshd.c,v 1.158 2001/01/28 10:37:26 markus Exp $");
+RCSID("$OpenBSD: sshd.c,v 1.159 2001/01/29 19:47:31 markus Exp $");
 
 #include <openssl/dh.h>
 #include <openssl/bn.h>
@@ -1186,6 +1186,7 @@ do_ssh1_kex(void)
 {
         int i, len;
         int plen, slen;
+        int rsafail = 0;
         BIGNUM *session_key_int;
         u_char session_key[SSH_SESSION_KEY_LENGTH];
         u_char cookie[8];
@@ -1296,7 +1297,7 @@ do_ssh1_kex(void)
          * with larger modulus first).
          */
         if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
-                /* Private key has bigger modulus. */
+                /* Server key has bigger modulus. */
                 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
                     BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
                         fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
@@ -1305,10 +1306,12 @@ do_ssh1_kex(void)
                             BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
                             SSH_KEY_BITS_RESERVED);
                 }
-                rsa_private_decrypt(session_key_int, session_key_int,
-                    sensitive_data.server_key->rsa);
-                rsa_private_decrypt(session_key_int, session_key_int,
-                    sensitive_data.ssh1_host_key->rsa);
+                if (rsa_private_decrypt(session_key_int, session_key_int,
+                    sensitive_data.server_key->rsa) <= 0)
+                        rsafail++;
+                if (rsa_private_decrypt(session_key_int, session_key_int,
+                    sensitive_data.ssh1_host_key->rsa) <= 0)
+                        rsafail++;
         } else {
                 /* Host key has bigger modulus (or they are equal). */
                 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
@@ -1319,10 +1322,12 @@ do_ssh1_kex(void)
                             BN_num_bits(sensitive_data.server_key->rsa->n),
                             SSH_KEY_BITS_RESERVED);
                 }
-                rsa_private_decrypt(session_key_int, session_key_int,
-                    sensitive_data.ssh1_host_key->rsa);
-                rsa_private_decrypt(session_key_int, session_key_int,
-                    sensitive_data.server_key->rsa);
+                if (rsa_private_decrypt(session_key_int, session_key_int,
+                    sensitive_data.ssh1_host_key->rsa) < 0)
+                        rsafail++;
+                if (rsa_private_decrypt(session_key_int, session_key_int,
+                    sensitive_data.server_key->rsa) < 0)
+                        rsafail++;
         }
 
         compute_session_id(session_id, cookie,
@@ -1337,15 +1342,29 @@ do_ssh1_kex(void)
          * least significant 256 bits of the integer; the first byte of the
          * key is in the highest bits.
          */
-        BN_mask_bits(session_key_int, sizeof(session_key) * 8);
-        len = BN_num_bytes(session_key_int);
-        if (len < 0 || len > sizeof(session_key))
-                fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
-                    get_remote_ipaddr(),
-                    len, sizeof(session_key));
-        memset(session_key, 0, sizeof(session_key));
-        BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
-
+        if (!rsafail) {
+                BN_mask_bits(session_key_int, sizeof(session_key) * 8);
+                len = BN_num_bytes(session_key_int);
+                if (len < 0 || len > sizeof(session_key)) {
+                        error("do_connection: bad session key len from %s: "
+                            "session_key_int %d > sizeof(session_key) %d",
+                            get_remote_ipaddr(), len, sizeof(session_key));
+                        rsafail++;
+                } else {
+                        memset(session_key, 0, sizeof(session_key));
+                        BN_bn2bin(session_key_int,
+                            session_key + sizeof(session_key) - len);
+                }
+        }
+        if (rsafail) {
+                log("do_connection: generating a fake encryption key");
+                for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
+                        if (i % 4 == 0)
+                                rand = arc4random();
+                        session_key[i] = rand & 0xff;
+                        rand >>= 8;
+                }
+        }
         /* Destroy the decrypted integer.  It is no longer needed. */
         BN_clear_free(session_key_int);