4 files changed, 124 insertions, 15 deletions

diff --git a/ChangeLog b/ChangeLog
index d53270d4e..546671bf0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+20020731
+ - (bal) OpenBSD CVS Sync
+   - markus@cvs.openbsd.org 2002/07/24 16:11:18
+     [hostfile.c hostfile.h sshconnect.c]
+     print out all known keys for a host if we get a unknown host key,
+     see discussion at http://marc.theaimsgroup.com/?t=101069210100016&r=1&w=4
+
+     the ssharp mitm tool attacks users in a similar way, so i'd like to
+     pointed out again:
+        A MITM attack is always possible if the ssh client prints:
+        The authenticity of host 'bla' can't be established.
+     (protocol version 2 with pubkey authentication allows you to detect
+     MITM attacks)
+
 20020730
  - (bal) [uidswap.c] SCO compile correction by gert@greenie.muc.de
 
@@ -1465,4 +1479,4 @@
  - (stevesk) entropy.c: typo in debug message
  - (djm) ssh-keygen -i needs seeded RNG; report from markus@
 
-$Id: ChangeLog,v 1.2409 2002/07/30 19:32:07 mouring Exp $
+$Id: ChangeLog,v 1.2410 2002/08/01 01:21:56 mouring Exp $
diff --git a/hostfile.c b/hostfile.c
index cefff8d62..dcee03448 100644
--- a/hostfile.c
+++ b/hostfile.c
@@ -36,7 +36,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: hostfile.c,v 1.29 2001/12/18 10:04:21 jakob Exp $");
+RCSID("$OpenBSD: hostfile.c,v 1.30 2002/07/24 16:11:18 markus Exp $");
 
 #include "packet.h"
 #include "match.h"
@@ -91,11 +91,14 @@ hostfile_check_key(int bits, Key *key, const char *host, const char *filename, i
  * in the list of our known hosts. Returns HOST_OK if the host is known and
  * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
  * if the host is known but used to have a different host key.
+ *
+ * If no 'key' has been specified and a key of type 'keytype' is known
+ * for the specified host, then HOST_FOUND is returned.
  */
 
-HostStatus
-check_host_in_hostfile(const char *filename, const char *host, Key *key,
-    Key *found, int *numret)
+static HostStatus
+check_host_in_hostfile_by_key_or_type(const char *filename,
+    const char *host, Key *key, int keytype, Key *found, int *numret)
 {
         FILE *f;
         char line[8192];
@@ -105,8 +108,7 @@ check_host_in_hostfile(const char *filename, const char *host, Key *key,
         HostStatus end_return;
 
         debug3("check_host_in_hostfile: filename %s", filename);
-        if (key == NULL)
-                fatal("no key to look up");
+
         /* Open the file containing the list of known hosts. */
         f = fopen(filename, "r");
         if (!f)
@@ -147,12 +149,20 @@ check_host_in_hostfile(const char *filename, const char *host, Key *key,
                  */
                 if (!hostfile_read_key(&cp, &kbits, found))
                         continue;
-                if (!hostfile_check_key(kbits, found, host, filename, linenum))
-                        continue;
 
                 if (numret != NULL)
                         *numret = linenum;
 
+                if (key == NULL) {
+                        /* we found a key of the requested type */
+                        if (found->type == keytype)
+                                return HOST_FOUND;
+                        continue;
+                }
+
+                if (!hostfile_check_key(kbits, found, host, filename, linenum))
+                        continue;
+
                 /* Check if the current key is the same as the given key. */
                 if (key_equal(key, found)) {
                         /* Ok, they match. */
@@ -177,6 +187,24 @@ check_host_in_hostfile(const char *filename, const char *host, Key *key,
         return end_return;
 }
 
+HostStatus
+check_host_in_hostfile(const char *filename, const char *host, Key *key,
+    Key *found, int *numret)
+{
+        if (key == NULL)
+                fatal("no key to look up");
+        return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
+            found, numret));
+}
+
+int
+lookup_key_in_hostfile_by_type(const char *filename, const char *host,
+    int keytype, Key *found, int *numret)
+{
+        return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
+            keytype, found, numret) == HOST_FOUND);
+}
+
 /*
  * Appends an entry to the host file.  Returns false if the entry could not
  * be appended.
diff --git a/hostfile.h b/hostfile.h
index 0244fdb53..063732421 100644
--- a/hostfile.h
+++ b/hostfile.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: hostfile.h,v 1.10 2001/12/18 10:04:21 jakob Exp $     */
+/*      $OpenBSD: hostfile.h,v 1.11 2002/07/24 16:11:18 markus Exp $    */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -15,12 +15,14 @@
 #define HOSTFILE_H
 
 typedef enum {
-        HOST_OK, HOST_NEW, HOST_CHANGED
+        HOST_OK, HOST_NEW, HOST_CHANGED, HOST_FOUND,
 }       HostStatus;
 
 int      hostfile_read_key(char **, u_int *, Key *);
 HostStatus
 check_host_in_hostfile(const char *, const char *, Key *, Key *, int *);
 int      add_host_to_hostfile(const char *, const char *, Key *);
+int     
+lookup_key_in_hostfile_by_type(const char *, const char *, int , Key *, int *);
 
 #endif
diff --git a/sshconnect.c b/sshconnect.c
index 9f8458dc7..8599684e5 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -13,7 +13,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: sshconnect.c,v 1.131 2002/07/12 13:29:09 itojun Exp $");
+RCSID("$OpenBSD: sshconnect.c,v 1.132 2002/07/24 16:11:18 markus Exp $");
 
 #include <openssl/bn.h>
 
@@ -46,6 +46,8 @@ extern uid_t original_effective_uid;
 #define INET6_ADDRSTRLEN 46
 #endif
 
+static int show_other_keys(const char *, Key *);
+
 /*
  * Connect to the given ssh server using a proxy command.
  */
@@ -494,7 +496,7 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
         int salen;
         char ntop[NI_MAXHOST];
         char msg[1024];
-        int len, host_line, ip_line;
+        int len, host_line, ip_line, has_keys;
         const char *host_file = NULL, *ip_file = NULL;
 
         /*
@@ -638,14 +640,19 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
                             "have requested strict checking.", type, host);
                         goto fail;
                 } else if (options.strict_host_key_checking == 2) {
+                        has_keys = show_other_keys(host, host_key);
                         /* The default */
                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
                         snprintf(msg, sizeof(msg),
                             "The authenticity of host '%.200s (%s)' can't be "
-                            "established.\n"
+                            "established%s\n"
                             "%s key fingerprint is %s.\n"
                             "Are you sure you want to continue connecting "
-                            "(yes/no)? ", host, ip, type, fp);
+                            "(yes/no)? ",
+                             host, ip,
+                             has_keys ? ",\nbut keys of different type are already "
+                             "known for this host." : ".",
+                             type, fp);
                         xfree(fp);
                         if (!confirm(msg))
                                 goto fail;
@@ -748,6 +755,9 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
                  * accept the authentication.
                  */
                 break;
+        case HOST_FOUND:
+                fatal("internal error");
+                break;
         }
 
         if (options.check_host_ip && host_status != HOST_CHANGED &&
@@ -859,3 +869,58 @@ ssh_put_password(char *password)
         memset(padded, 0, size);
         xfree(padded);
 }
+
+static int
+show_key_from_file(const char *file, const char *host, int keytype)
+{
+        Key *found;
+        char *fp;
+        int line, ret;
+
+        found = key_new(keytype);
+        if ((ret = lookup_key_in_hostfile_by_type(file, host,
+            keytype, found, &line))) {
+                fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
+                log("WARNING: %s key found for host %s\n"
+                    "in file %s line %d with\n"
+                    "%s key fingerprint %s.",
+                    key_type(found), host, file, line,
+                    key_type(found), fp);
+                xfree(fp);
+        }
+        key_free(found);
+        return (ret);
+}
+
+/* print all known host keys for a given host, but skip keys of given type */
+static int
+show_other_keys(const char *host, Key *key)
+{
+        int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
+        int i, found = 0;
+
+        for (i = 0; type[i] != -1; i++) {
+                if (type[i] == key->type)
+                        continue;
+                if (type[i] != KEY_RSA1 &&
+                    show_key_from_file(options.user_hostfile2, host, type[i])) {
+                        found = 1;
+                        continue;
+                }
+                if (type[i] != KEY_RSA1 &&
+                    show_key_from_file(options.system_hostfile2, host, type[i])) {
+                        found = 1;
+                        continue;
+                }
+                if (show_key_from_file(options.user_hostfile, host, type[i])) {
+                        found = 1;
+                        continue;
+                }
+                if (show_key_from_file(options.system_hostfile, host, type[i])) {
+                        found = 1;
+                        continue;
+                }
+                debug2("no key of type %d for host %s", type[i], host);
+        }
+        return (found);
+}