- djm@cvs.openbsd.org 2010/11/29 23:45:51

     [auth.c hostfile.c hostfile.h ssh.c ssh_config.5 sshconnect.c]
     [sshconnect.h sshconnect2.c]
     automatically order the hostkeys requested by the client based on
     which hostkeys are already recorded in known_hosts. This avoids
     hostkey warnings when connecting to servers with new ECDSA keys
     that are preferred by default; with markus@

9 files changed, 452 insertions, 291 deletions

diff --git a/ChangeLog b/ChangeLog
index 44e45eb8a..6ee7c0014 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -38,6 +38,13 @@
      [authfile.c]
      correctly load comment for encrypted rsa1 keys;
      report/fix Joachim Schipper; ok djm@
+   - djm@cvs.openbsd.org 2010/11/29 23:45:51
+     [auth.c hostfile.c hostfile.h ssh.c ssh_config.5 sshconnect.c]
+     [sshconnect.h sshconnect2.c]
+     automatically order the hostkeys requested by the client based on
+     which hostkeys are already recorded in known_hosts. This avoids
+     hostkey warnings when connecting to servers with new ECDSA keys
+     that are preferred by default; with markus@
 
 20101124
  - (dtucker) [platform.c session.c] Move the getluid call out of session.c and
diff --git a/auth.c b/auth.c
index 6fe1b21a4..33680b91b 100644
--- a/auth.c
+++ b/auth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.c,v 1.90 2010/11/23 02:35:50 djm Exp $ */
+/* $OpenBSD: auth.c,v 1.91 2010/11/29 23:45:51 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -379,16 +379,15 @@ HostStatus
 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
     const char *sysfile, const char *userfile)
 {
-        Key *found;
         char *user_hostfile;
         struct stat st;
         HostStatus host_status;
+        struct hostkeys *hostkeys;
+        const struct hostkey_entry *found;
 
-        /* Check if we know the host and its host key. */
-        found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
-        host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
-
-        if (host_status != HOST_OK && userfile != NULL) {
+        hostkeys = init_hostkeys();
+        load_hostkeys(hostkeys, host, sysfile);
+        if (userfile != NULL) {
                 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
                 if (options.strict_modes &&
                     (stat(user_hostfile, &st) == 0) &&
@@ -401,16 +400,23 @@ check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
                             user_hostfile);
                 } else {
                         temporarily_use_uid(pw);
-                        host_status = check_host_in_hostfile(user_hostfile,
-                            host, key, found, NULL);
+                        load_hostkeys(hostkeys, host, user_hostfile);
                         restore_uid();
                 }
                 xfree(user_hostfile);
         }
-        key_free(found);
+        host_status = check_key_in_hostkeys(hostkeys, key, &found);
+        if (host_status == HOST_REVOKED)
+                error("WARNING: revoked key for %s attempted authentication",
+                    found->host);
+        else if (host_status == HOST_OK)
+                debug("%s: key for %s found at %s:%ld", __func__,
+                    found->host, found->file, found->line);
+        else
+                debug("%s: key for host %s not found", __func__, host);
+
+        free_hostkeys(hostkeys);
 
-        debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
-            "ok" : "not found", host);
         return host_status;
 }
 
diff --git a/hostfile.c b/hostfile.c
index afab6dad1..9145529cb 100644
--- a/hostfile.c
+++ b/hostfile.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: hostfile.c,v 1.48 2010/03/04 10:36:03 djm Exp $ */
+/* $OpenBSD: hostfile.c,v 1.49 2010/11/29 23:45:51 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -56,6 +56,12 @@
 #include "key.h"
 #include "hostfile.h"
 #include "log.h"
+#include "misc.h"
+
+struct hostkeys {
+        struct hostkey_entry *entries;
+        u_int num_entries;
+};
 
 static int
 extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
@@ -164,26 +170,28 @@ hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
 
         /* Return results. */
         *cpp = cp;
-        *bitsp = key_size(ret);
+        if (bitsp != NULL)
+                *bitsp = key_size(ret);
         return 1;
 }
 
 static int
-hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
+hostfile_check_key(int bits, const Key *key, const char *host,
+    const char *filename, u_long linenum)
 {
         if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
                 return 1;
         if (bits != BN_num_bits(key->rsa->n)) {
-                logit("Warning: %s, line %d: keysize mismatch for host %s: "
+                logit("Warning: %s, line %lu: keysize mismatch for host %s: "
                     "actual %d vs. announced %d.",
                     filename, linenum, host, BN_num_bits(key->rsa->n), bits);
-                logit("Warning: replace %d with %d in %s, line %d.",
+                logit("Warning: replace %d with %d in %s, line %lu.",
                     bits, BN_num_bits(key->rsa->n), filename, linenum);
         }
         return 1;
 }
 
-static enum { MRK_ERROR, MRK_NONE, MRK_REVOKE, MRK_CA }
+static HostkeyMarker
 check_markers(char **cpp)
 {
         char marker[32], *sp, *cp = *cpp;
@@ -218,49 +226,32 @@ check_markers(char **cpp)
         return ret;
 }
 
-/*
- * Checks whether the given host (which must be in all lowercase) is already
- * 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.
- */
+struct hostkeys *
+init_hostkeys(void)
+{
+        struct hostkeys *ret = xcalloc(1, sizeof(*ret));
 
-static HostStatus
-check_host_in_hostfile_by_key_or_type(const char *filename,
-    const char *host, const Key *key, int keytype, Key *found,
-    int want_revocation, int *numret)
+        ret->entries = NULL;
+        return ret;
+}
+
+void
+load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path)
 {
         FILE *f;
         char line[8192];
-        int want, have, linenum = 0, want_cert = key_is_cert(key);
-        u_int kbits;
+        u_long linenum = 0, num_loaded = 0;
         char *cp, *cp2, *hashed_host;
-        HostStatus end_return;
-
-        debug3("check_host_in_hostfile: host %s filename %s", host, filename);
-
-        if (want_revocation && (key == NULL || keytype != 0 || found != NULL))
-                fatal("%s: invalid arguments", __func__);
-
-        /* Open the file containing the list of known hosts. */
-        f = fopen(filename, "r");
-        if (!f)
-                return HOST_NEW;
-
-        /*
-         * Return value when the loop terminates.  This is set to
-         * HOST_CHANGED if we have seen a different key for the host and have
-         * not found the proper one.
-         */
-        end_return = HOST_NEW;
-
-        /* Go through the file. */
-        while (fgets(line, sizeof(line), f)) {
+        HostkeyMarker marker;
+        Key *key;
+        int kbits;
+
+        if ((f = fopen(path, "r")) == NULL)
+                return;
+        debug3("%s: loading entries for host \"%.100s\" from file \"%s\"",
+            __func__, host, path);
+        while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) {
                 cp = line;
-                linenum++;
 
                 /* Skip any leading whitespace, comments and empty lines. */
                 for (; *cp == ' ' || *cp == '\t'; cp++)
@@ -268,19 +259,11 @@ check_host_in_hostfile_by_key_or_type(const char *filename,
                 if (!*cp || *cp == '#' || *cp == '\n')
                         continue;
 
-                if (want_revocation)
-                        want = MRK_REVOKE;
-                else if (want_cert)
-                        want = MRK_CA;
-                else
-                        want = MRK_NONE;
-
-                if ((have = check_markers(&cp)) == MRK_ERROR) {
-                        verbose("%s: invalid marker at %s:%d",
-                            __func__, filename, linenum);
-                        continue;
-                } else if (want != have)
+                if ((marker = check_markers(&cp)) == MRK_ERROR) {
+                        verbose("%s: invalid marker at %s:%lu",
+                            __func__, path, linenum);
                         continue;
+                }
 
                 /* Find the end of the host name portion. */
                 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
@@ -292,8 +275,8 @@ check_host_in_hostfile_by_key_or_type(const char *filename,
                                 continue;
                         hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
                         if (hashed_host == NULL) {
-                                debug("Invalid hashed host line %d of %s",
-                                    linenum, filename);
+                                debug("Invalid hashed host line %lu of %s",
+                                    linenum, path);
                                 continue;
                         }
                         if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
@@ -303,98 +286,166 @@ check_host_in_hostfile_by_key_or_type(const char *filename,
                 /* Got a match.  Skip host name. */
                 cp = cp2;
 
-                if (want_revocation)
-                        found = key_new(KEY_UNSPEC);
-
                 /*
                  * Extract the key from the line.  This will skip any leading
                  * whitespace.  Ignore badly formatted lines.
                  */
-                if (!hostfile_read_key(&cp, &kbits, found))
+                key = key_new(KEY_UNSPEC);
+                if (!hostfile_read_key(&cp, &kbits, key)) {
+                        key_free(key);
+                        key = key_new(KEY_RSA1);
+                        if (!hostfile_read_key(&cp, &kbits, key)) {
+                                key_free(key);
+                                continue;
+                        }
+                }
+                if (!hostfile_check_key(kbits, key, host, path, linenum))
                         continue;
 
-                if (numret != NULL)
-                        *numret = linenum;
+                debug3("%s: found %skey type %s in file %s:%lu", __func__,
+                    marker == MRK_NONE ? "" :
+                    (marker == MRK_CA ? "ca " : "revoked "),
+                    key_type(key), path, linenum);
+                hostkeys->entries = xrealloc(hostkeys->entries,
+                    hostkeys->num_entries + 1, sizeof(*hostkeys->entries));
+                hostkeys->entries[hostkeys->num_entries].host = xstrdup(host);
+                hostkeys->entries[hostkeys->num_entries].file = xstrdup(path);
+                hostkeys->entries[hostkeys->num_entries].line = linenum;
+                hostkeys->entries[hostkeys->num_entries].key = key;
+                hostkeys->entries[hostkeys->num_entries].marker = marker;
+                hostkeys->num_entries++;
+                num_loaded++;
+        }
+        debug3("%s: loaded %lu keys", __func__, num_loaded);
+        return;
+}       
 
-                if (key == NULL) {
-                        /* we found a key of the requested type */
-                        if (found->type == keytype) {
-                                fclose(f);
-                                return HOST_FOUND;
-                        }
-                        continue;
-                }
+void
+free_hostkeys(struct hostkeys *hostkeys)
+{
+        u_int i;
+
+        for (i = 0; i < hostkeys->num_entries; i++) {
+                xfree(hostkeys->entries[i].host);
+                xfree(hostkeys->entries[i].file);
+                key_free(hostkeys->entries[i].key);
+                bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
+        }
+        if (hostkeys->entries != NULL)
+                xfree(hostkeys->entries);
+        hostkeys->entries = NULL;
+        hostkeys->num_entries = 0;
+        xfree(hostkeys);
+}
 
-                if (!hostfile_check_key(kbits, found, host, filename, linenum))
+static int
+check_key_not_revoked(struct hostkeys *hostkeys, Key *k)
+{
+        int is_cert = key_is_cert(k);
+        u_int i;
+
+        for (i = 0; i < hostkeys->num_entries; i++) {
+                if (hostkeys->entries[i].marker != MRK_REVOKE)
                         continue;
+                if (key_equal_public(k, hostkeys->entries[i].key))
+                        return -1;
+                if (is_cert &&
+                    key_equal_public(k->cert->signature_key,
+                    hostkeys->entries[i].key))
+                        return -1;
+        }
+        return 0;
+}
 
-                if (want_revocation) {
-                        if (key_is_cert(key) &&
-                            key_equal_public(key->cert->signature_key, found)) {
-                                verbose("check_host_in_hostfile: revoked CA "
-                                    "line %d", linenum);
-                                key_free(found);
-                                return HOST_REVOKED;
-                        }
-                        if (key_equal_public(key, found)) {
-                                verbose("check_host_in_hostfile: revoked key "
-                                    "line %d", linenum);
-                                key_free(found);
-                                return HOST_REVOKED;
-                        }
-                        key_free(found);
+/*
+ * Match keys against a specified key, or look one up by key type.
+ *
+ * If looking for a keytype (key == NULL) and one is found then return
+ * HOST_FOUND, otherwise HOST_NEW.
+ *
+ * If looking for a key (key != NULL):
+ *  1. If the key is a cert and a matching CA is found, return HOST_OK
+ *  2. If the key is not a cert and a matching key is found, return HOST_OK
+ *  3. If no key matches but a key with a different type is found, then
+ *     return HOST_CHANGED
+ *  4. If no matching keys are found, then return HOST_NEW.
+ *
+ * Finally, check any found key is not revoked.
+ */
+static HostStatus
+check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
+    Key *k, int keytype, const struct hostkey_entry **found)
+{
+        u_int i;
+        HostStatus end_return = HOST_NEW;
+        int want_cert = key_is_cert(k);
+        HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
+        int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2;
+
+        if (found != NULL)
+                *found = NULL;
+
+        for (i = 0; i < hostkeys->num_entries; i++) {
+                if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1)
+                        continue;
+                if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1)
                         continue;
+                if (hostkeys->entries[i].marker != want_marker)
+                        continue;
+                if (k == NULL) {
+                        if (hostkeys->entries[i].key->type != keytype)
+                                continue;
+                        end_return = HOST_FOUND;
+                        if (found != NULL)
+                                *found = hostkeys->entries + i;
+                        k = hostkeys->entries[i].key;
+                        break;
                 }
-
-                /* Check if the current key is the same as the given key. */
-                if (want_cert && key_equal(key->cert->signature_key, found)) {
-                        /* Found CA cert for key */
-                        debug3("check_host_in_hostfile: CA match line %d",
-                            linenum);
-                        fclose(f);
-                        return HOST_OK;
-                } else if (!want_cert && key_equal(key, found)) {
-                        /* Found identical key */
-                        debug3("check_host_in_hostfile: match line %d", linenum);
-                        fclose(f);
-                        return HOST_OK;
+                if (want_cert) {
+                        if (key_equal_public(k->cert->signature_key,
+                            hostkeys->entries[i].key)) {
+                                /* A matching CA exists */
+                                end_return = HOST_OK;
+                                if (found != NULL)
+                                        *found = hostkeys->entries + i;
+                                break;
+                        }
+                } else {
+                        if (key_equal(k, hostkeys->entries[i].key)) {
+                                end_return = HOST_OK;
+                                if (found != NULL)
+                                        *found = hostkeys->entries + i;
+                                break;
+                        }
+                        /* A non-maching key exists */
+                        end_return = HOST_CHANGED;
+                        if (found != NULL)
+                                *found = hostkeys->entries + i;
                 }
-                /*
-                 * They do not match.  We will continue to go through the
-                 * file; however, we note that we will not return that it is
-                 * new.
-                 */
-                end_return = HOST_CHANGED;
         }
-        /* Clear variables and close the file. */
-        fclose(f);
-
-        /*
-         * Return either HOST_NEW or HOST_CHANGED, depending on whether we
-         * saw a different key for the host.
-         */
+        if (check_key_not_revoked(hostkeys, k) != 0) {
+                end_return = HOST_REVOKED;
+                if (found != NULL)
+                        *found = NULL;
+        }
         return end_return;
 }
-
+        
 HostStatus
-check_host_in_hostfile(const char *filename, const char *host, const Key *key,
-    Key *found, int *numret)
+check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key,
+    const struct hostkey_entry **found)
 {
         if (key == NULL)
                 fatal("no key to look up");
-        if (check_host_in_hostfile_by_key_or_type(filename, host,
-            key, 0, NULL, 1, NULL) == HOST_REVOKED)
-                return HOST_REVOKED;
-        return check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
-            found, 0, numret);
+        return check_hostkeys_by_key_or_type(hostkeys, key, 0, found);
 }
 
 int
-lookup_key_in_hostfile_by_type(const char *filename, const char *host,
-    int keytype, Key *found, int *numret)
+lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
+    const struct hostkey_entry **found)
 {
-        return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
-            keytype, found, 0, numret) == HOST_FOUND);
+        return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype,
+            found) == HOST_FOUND);
 }
 
 /*
diff --git a/hostfile.h b/hostfile.h
index 1d460c1a9..d84d422ff 100644
--- a/hostfile.h
+++ b/hostfile.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: hostfile.h,v 1.18 2010/03/04 10:36:03 djm Exp $ */
+/* $OpenBSD: hostfile.h,v 1.19 2010/11/29 23:45:51 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -18,12 +18,30 @@ typedef enum {
         HOST_OK, HOST_NEW, HOST_CHANGED, HOST_REVOKED, HOST_FOUND
 }       HostStatus;
 
+typedef enum {
+        MRK_ERROR, MRK_NONE, MRK_REVOKE, MRK_CA
+}       HostkeyMarker;
+
+struct hostkey_entry {
+        char *host;
+        char *file;
+        u_long line;
+        Key *key;
+        HostkeyMarker marker;
+};
+struct hostkeys;
+
+struct hostkeys *init_hostkeys(void);
+void     load_hostkeys(struct hostkeys *, const char *, const char *);
+void     free_hostkeys(struct hostkeys *);
+
+HostStatus check_key_in_hostkeys(struct hostkeys *, Key *,
+    const struct hostkey_entry **);
+int      lookup_key_in_hostkeys_by_type(struct hostkeys *, int,
+    const struct hostkey_entry **);
+
 int      hostfile_read_key(char **, u_int *, Key *);
-HostStatus check_host_in_hostfile(const char *, const char *,
-            const Key *, Key *, int *);
-int     add_host_to_hostfile(const char *, const char *, const Key *, int);
-int     lookup_key_in_hostfile_by_type(const char *, const char *,
-            int, Key *, int *);
+int      add_host_to_hostfile(const char *, const char *, const Key *, int);
 
 #define HASH_MAGIC      "|1|"
 #define HASH_DELIM      '|'
diff --git a/ssh.c b/ssh.c
index f413f8a5c..ec690ae38 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.354 2010/11/13 23:27:50 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.355 2010/11/29 23:45:51 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -880,7 +880,7 @@ main(int ac, char **av)
 
         /* Log into the remote system.  Never returns if the login fails. */
         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr,
-            pw, timeout_ms);
+            options.port, pw, timeout_ms);
 
         if (packet_connection_is_on_socket()) {
                 verbose("Authenticated to %s ([%s]:%d).", host,
diff --git a/ssh_config.5 b/ssh_config.5
index a51a37dde..5c6673de3 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh_config.5,v 1.144 2010/11/15 07:40:14 jmc Exp $
-.Dd $Mdocdate: November 15 2010 $
+.\" $OpenBSD: ssh_config.5,v 1.145 2010/11/29 23:45:51 djm Exp $
+.Dd $Mdocdate: November 29 2010 $
 .Dt SSH_CONFIG 5
 .Os
 .Sh NAME
@@ -555,6 +555,9 @@ ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,
 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
 ssh-rsa,ssh-dss
 .Ed
+.Pp
+If hostkeys are known for the destination host then this default is modified
+to prefer their algorithms.
 .It Cm HostKeyAlias
 Specifies an alias that should be used instead of the
 real host name when looking up or saving the host key
diff --git a/sshconnect.c b/sshconnect.c
index 78068c602..064bb74b3 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.228 2010/10/06 21:10:21 djm Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.229 2010/11/29 23:45:51 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -75,7 +75,7 @@ extern char *__progname;
 extern uid_t original_real_uid;
 extern uid_t original_effective_uid;
 
-static int show_other_keys(const char *, Key *);
+static int show_other_keys(struct hostkeys *, Key *);
 static void warn_changed_key(Key *);
 
 /*
@@ -607,6 +607,79 @@ check_host_cert(const char *host, const Key *host_key)
         return 1;
 }
 
+static int
+sockaddr_is_local(struct sockaddr *hostaddr)
+{
+        switch (hostaddr->sa_family) {
+        case AF_INET:
+                return (ntohl(((struct sockaddr_in *)hostaddr)->
+                    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
+        case AF_INET6:
+                return IN6_IS_ADDR_LOOPBACK(
+                    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
+        default:
+                return 0;
+        }
+}
+
+/*
+ * Prepare the hostname and ip address strings that are used to lookup
+ * host keys in known_hosts files. These may have a port number appended.
+ */
+void
+get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
+    u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
+{
+        char ntop[NI_MAXHOST];
+        socklen_t addrlen;
+
+        switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
+        case -1:
+                addrlen = 0;
+                break;
+        case AF_INET:
+                addrlen = sizeof(struct sockaddr_in);
+                break;
+        case AF_INET6:
+                addrlen = sizeof(struct sockaddr_in6);
+                break;
+        default:
+                addrlen = sizeof(struct sockaddr);
+                break;
+        }
+
+        /*
+         * We don't have the remote ip-address for connections
+         * using a proxy command
+         */
+        if (hostfile_ipaddr != NULL) {
+                if (options.proxy_command == NULL) {
+                        if (getnameinfo(hostaddr, addrlen,
+                            ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
+                        fatal("check_host_key: getnameinfo failed");
+                        *hostfile_ipaddr = put_host_port(ntop, port);
+                } else {
+                        *hostfile_ipaddr = xstrdup("<no hostip for proxy "
+                            "command>");
+                }
+        }
+
+        /*
+         * Allow the user to record the key under a different name or
+         * differentiate a non-standard port.  This is useful for ssh
+         * tunneling over forwarded connections or if you run multiple
+         * sshd's on different ports on the same machine.
+         */
+        if (hostfile_hostname != NULL) {
+                if (options.host_key_alias != NULL) {
+                        *hostfile_hostname = xstrdup(options.host_key_alias);
+                        debug("using hostkeyalias: %s", *hostfile_hostname);
+                } else {
+                        *hostfile_hostname = put_host_port(hostname, port);
+                }
+        }
+}
+
 /*
  * check whether the supplied host key is valid, return -1 if the key
  * is not valid. the user_hostfile will not be updated if 'readonly' is true.
@@ -616,21 +689,21 @@ check_host_cert(const char *host, const Key *host_key)
 #define ROQUIET 2
 static int
 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
-    Key *host_key, int readonly, const char *user_hostfile,
-    const char *system_hostfile)
+    Key *host_key, int readonly, char *user_hostfile,
+    char *system_hostfile)
 {
-        Key *file_key, *raw_key = NULL;
+        Key *raw_key = NULL;
         const char *type;
         char *ip = NULL, *host = NULL;
         char hostline[1000], *hostp, *fp, *ra;
         HostStatus host_status;
         HostStatus ip_status;
-        int r, want_cert, local = 0, host_ip_differ = 0;
-        int salen;
-        char ntop[NI_MAXHOST];
+        int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
+        int local = sockaddr_is_local(hostaddr);
         char msg[1024];
-        int len, host_line, ip_line, cancelled_forwarding = 0;
-        const char *host_file = NULL, *ip_file = NULL;
+        int len, cancelled_forwarding = 0;
+        struct hostkeys *host_hostkeys, *ip_hostkeys;
+        const struct hostkey_entry *host_found, *ip_found;
 
         /*
          * Force accepting of the host key for loopback/localhost. The
@@ -640,23 +713,6 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
          * essentially disables host authentication for localhost; however,
          * this is probably not a real problem.
          */
-        /**  hostaddr == 0! */
-        switch (hostaddr->sa_family) {
-        case AF_INET:
-                local = (ntohl(((struct sockaddr_in *)hostaddr)->
-                    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
-                salen = sizeof(struct sockaddr_in);
-                break;
-        case AF_INET6:
-                local = IN6_IS_ADDR_LOOPBACK(
-                    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
-                salen = sizeof(struct sockaddr_in6);
-                break;
-        default:
-                local = 0;
-                salen = sizeof(struct sockaddr_storage);
-                break;
-        }
         if (options.no_host_authentication_for_localhost == 1 && local &&
             options.host_key_alias == NULL) {
                 debug("Forcing accepting of host key for "
@@ -665,17 +721,10 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
         }
 
         /*
-         * We don't have the remote ip-address for connections
-         * using a proxy command
+         * Prepare the hostname and address strings used for hostkey lookup.
+         * In some cases, these will have a port number appended.
          */
-        if (options.proxy_command == NULL) {
-                if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
-                    NULL, 0, NI_NUMERICHOST) != 0)
-                        fatal("check_host_key: getnameinfo failed");
-                ip = put_host_port(ntop, port);
-        } else {
-                ip = xstrdup("<no hostip for proxy command>");
-        }
+        get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
 
         /*
          * Turn off check_host_ip if the connection is to localhost, via proxy
@@ -685,74 +734,52 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
             strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
                 options.check_host_ip = 0;
 
-        /*
-         * Allow the user to record the key under a different name or
-         * differentiate a non-standard port.  This is useful for ssh
-         * tunneling over forwarded connections or if you run multiple
-         * sshd's on different ports on the same machine.
-         */
-        if (options.host_key_alias != NULL) {
-                host = xstrdup(options.host_key_alias);
-                debug("using hostkeyalias: %s", host);
-        } else {
-                host = put_host_port(hostname, port);
+        host_hostkeys = init_hostkeys();
+        load_hostkeys(host_hostkeys, host, user_hostfile);
+        load_hostkeys(host_hostkeys, host, system_hostfile);
+
+        ip_hostkeys = NULL;
+        if (!want_cert && options.check_host_ip) {
+                ip_hostkeys = init_hostkeys();
+                load_hostkeys(ip_hostkeys, ip, user_hostfile);
+                load_hostkeys(ip_hostkeys, ip, system_hostfile);
         }
 
  retry:
+        /* Reload these as they may have changed on cert->key downgrade */
         want_cert = key_is_cert(host_key);
         type = key_type(host_key);
 
         /*
-         * Store the host key from the known host file in here so that we can
-         * compare it with the key for the IP address.
-         */
-        file_key = key_new(key_is_cert(host_key) ? KEY_UNSPEC : host_key->type);
-
-        /*
          * Check if the host key is present in the user's list of known
          * hosts or in the systemwide list.
          */
-        host_file = user_hostfile;
-        host_status = check_host_in_hostfile(host_file, host, host_key,
-            file_key, &host_line);
-        if (host_status == HOST_NEW) {
-                host_file = system_hostfile;
-                host_status = check_host_in_hostfile(host_file, host, host_key,
-                    file_key, &host_line);
-        }
+        host_status = check_key_in_hostkeys(host_hostkeys, host_key,
+            &host_found);
+
         /*
          * Also perform check for the ip address, skip the check if we are
          * localhost, looking for a certificate, or the hostname was an ip
          * address to begin with.
          */
-        if (!want_cert && options.check_host_ip) {
-                Key *ip_key = key_new(host_key->type);
-
-                ip_file = user_hostfile;
-                ip_status = check_host_in_hostfile(ip_file, ip, host_key,
-                    ip_key, &ip_line);
-                if (ip_status == HOST_NEW) {
-                        ip_file = system_hostfile;
-                        ip_status = check_host_in_hostfile(ip_file, ip,
-                            host_key, ip_key, &ip_line);
-                }
+        if (!want_cert && ip_hostkeys != NULL) {
+                ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
+                    &ip_found);
                 if (host_status == HOST_CHANGED &&
-                    (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
+                    (ip_status != HOST_CHANGED || 
+                    (ip_found != NULL &&
+                    !key_equal(ip_found->key, host_found->key))))
                         host_ip_differ = 1;
-
-                key_free(ip_key);
         } else
                 ip_status = host_status;
 
-        key_free(file_key);
-
         switch (host_status) {
         case HOST_OK:
                 /* The host is known and the key matches. */
                 debug("Host '%.200s' is known and matches the %s host %s.",
                     host, type, want_cert ? "certificate" : "key");
-                debug("Found %s in %s:%d",
-                    want_cert ? "CA key" : "key", host_file, host_line);
+                debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
+                    host_found->file, host_found->line);
                 if (want_cert && !check_host_cert(hostname, host_key))
                         goto fail;
                 if (options.check_host_ip && ip_status == HOST_NEW) {
@@ -803,7 +830,7 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                 } else if (options.strict_host_key_checking == 2) {
                         char msg1[1024], msg2[1024];
 
-                        if (show_other_keys(host, host_key))
+                        if (show_other_keys(host_hostkeys, host_key))
                                 snprintf(msg1, sizeof(msg1),
                                     "\nbut keys of different type are already"
                                     " known for this host.");
@@ -844,8 +871,7 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                  * local known_hosts file.
                  */
                 if (options.check_host_ip && ip_status == HOST_NEW) {
-                        snprintf(hostline, sizeof(hostline), "%s,%s",
-                            host, ip);
+                        snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
                         hostp = hostline;
                         if (options.hash_known_hosts) {
                                 /* Add hash of host and IP separately */
@@ -899,8 +925,8 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                          * all hosts that one might visit.
                          */
                         debug("Host certificate authority does not "
-                            "match %s in %s:%d", CA_MARKER,
-                            host_file, host_line);
+                            "match %s in %s:%lu", CA_MARKER,
+                            host_found->file, host_found->line);
                         goto fail;
                 }
                 if (readonly == ROQUIET)
@@ -922,13 +948,15 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                         error("DNS SPOOFING is happening or the IP address for the host");
                         error("and its host key have changed at the same time.");
                         if (ip_status != HOST_NEW)
-                                error("Offending key for IP in %s:%d", ip_file, ip_line);
+                                error("Offending key for IP in %s:%lu",
+                                    ip_found->file, ip_found->line);
                 }
                 /* The host key has changed. */
                 warn_changed_key(host_key);
                 error("Add correct host key in %.100s to get rid of this message.",
                     user_hostfile);
-                error("Offending key in %s:%d", host_file, host_line);
+                error("Offending %s key in %s:%lu", key_type(host_found->key),
+                    host_found->file, host_found->line);
 
                 /*
                  * If strict host key checking is in use, the user will have
@@ -1013,13 +1041,13 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                 snprintf(msg, sizeof(msg),
                     "Warning: the %s host key for '%.200s' "
                     "differs from the key for the IP address '%.128s'"
-                    "\nOffending key for IP in %s:%d",
-                    type, host, ip, ip_file, ip_line);
+                    "\nOffending key for IP in %s:%lu",
+                    type, host, ip, ip_found->file, ip_found->line);
                 if (host_status == HOST_OK) {
                         len = strlen(msg);
                         snprintf(msg + len, sizeof(msg) - len,
-                            "\nMatching host key in %s:%d",
-                            host_file, host_line);
+                            "\nMatching host key in %s:%lu",
+                            host_found->file, host_found->line);
                 }
                 if (options.strict_host_key_checking == 1) {
                         logit("%s", msg);
@@ -1037,6 +1065,10 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 
         xfree(ip);
         xfree(host);
+        if (host_hostkeys != NULL)
+                free_hostkeys(host_hostkeys);
+        if (ip_hostkeys != NULL)
+                free_hostkeys(ip_hostkeys);
         return 0;
 
 fail:
@@ -1056,6 +1088,10 @@ fail:
                 key_free(raw_key);
         xfree(ip);
         xfree(host);
+        if (host_hostkeys != NULL)
+                free_hostkeys(host_hostkeys);
+        if (ip_hostkeys != NULL)
+                free_hostkeys(ip_hostkeys);
         return -1;
 }
 
@@ -1065,6 +1101,11 @@ verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
 {
         struct stat st;
         int flags = 0;
+        char *fp;
+
+        fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
+        debug("Server host key: %s %s", key_type(host_key), fp);
+        xfree(fp);
 
         /* XXX certs are not yet supported for DNS */
         if (!key_is_cert(host_key) && options.verify_host_key_dns &&
@@ -1108,7 +1149,7 @@ verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
  */
 void
 ssh_login(Sensitive *sensitive, const char *orighost,
-    struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
+    struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
 {
         char *host, *cp;
         char *server_user, *local_user;
@@ -1131,7 +1172,7 @@ ssh_login(Sensitive *sensitive, const char *orighost,
         /* key exchange */
         /* authenticate user */
         if (compat20) {
-                ssh_kex2(host, hostaddr);
+                ssh_kex2(host, hostaddr, port);
                 ssh_userauth2(local_user, server_user, host, sensitive);
         } else {
                 ssh_kex(host, hostaddr);
@@ -1158,61 +1199,35 @@ ssh_put_password(char *password)
         xfree(padded);
 }
 
-static int
-show_key_from_file(const char *file, const char *host, int keytype)
-{
-        Key *found;
-        char *fp, *ra;
-        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);
-                ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART);
-                logit("WARNING: %s key found for host %s\n"
-                    "in %s:%d\n"
-                    "%s key fingerprint %s.\n%s\n",
-                    key_type(found), host, file, line,
-                    key_type(found), fp, ra);
-                xfree(ra);
-                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)
+show_other_keys(struct hostkeys *hostkeys, Key *key)
 {
         int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1};
-        int i, found = 0;
+        int i, ret = 0;
+        char *fp, *ra;
+        const struct hostkey_entry *found;
 
         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;
+                if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
                         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);
+                fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
+                ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
+                logit("WARNING: %s key found for host %s\n"
+                    "in %s:%lu\n"
+                    "%s key fingerprint %s.",
+                    key_type(found->key),
+                    found->host, found->file, found->line,
+                    key_type(found->key), fp);
+                if (options.visual_host_key)
+                        logit("%s", ra);
+                xfree(ra);
+                xfree(fp);
+                ret = 1;
         }
-        return (found);
+        return ret;
 }
 
 static void
diff --git a/sshconnect.h b/sshconnect.h
index 69163afbc..fd7f7f7c6 100644
--- a/sshconnect.h
+++ b/sshconnect.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.h,v 1.26 2010/10/06 06:39:28 djm Exp $ */
+/* $OpenBSD: sshconnect.h,v 1.27 2010/11/29 23:45:51 djm Exp $ */
 
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
@@ -36,15 +36,18 @@ ssh_connect(const char *, struct sockaddr_storage *, u_short, int, int,
     int *, int, int, const char *);
 void     ssh_kill_proxy_command(void);
 
-void
-ssh_login(Sensitive *, const char *, struct sockaddr *, struct passwd *, int);
+void     ssh_login(Sensitive *, const char *, struct sockaddr *, u_short,
+    struct passwd *, int);
 
 void     ssh_exchange_identification(int);
 
 int      verify_host_key(char *, struct sockaddr *, Key *);
 
+void     get_hostfile_hostname_ipaddr(char *, struct sockaddr *, u_short,
+    char **, char **);
+
 void     ssh_kex(char *, struct sockaddr *);
-void     ssh_kex2(char *, struct sockaddr *);
+void     ssh_kex2(char *, struct sockaddr *, u_short);
 
 void     ssh_userauth1(const char *, const char *, char *, Sensitive *);
 void     ssh_userauth2(const char *, const char *, char *, Sensitive *);
diff --git a/sshconnect2.c b/sshconnect2.c
index 6fe356cca..3cb9b101c 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.185 2010/09/22 05:01:29 djm Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.186 2010/11/29 23:45:51 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -69,6 +69,7 @@
 #include "msg.h"
 #include "pathnames.h"
 #include "uidswap.h"
+#include "hostfile.h"
 #include "schnorr.h"
 #include "jpake.h"
 
@@ -101,8 +102,60 @@ verify_host_key_callback(Key *hostkey)
         return 0;
 }
 
+static char *
+order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
+{
+        char *oavail, *avail, *first, *last, *alg, *hostname, *ret;
+        size_t maxlen;
+        struct hostkeys *hostkeys;
+        int ktype;
+
+        /* Find all hostkeys for this hostname */
+        get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
+        hostkeys = init_hostkeys();
+        load_hostkeys(hostkeys, hostname, options.user_hostfile2);
+        load_hostkeys(hostkeys, hostname, options.system_hostfile2);
+        load_hostkeys(hostkeys, hostname, options.user_hostfile);
+        load_hostkeys(hostkeys, hostname, options.system_hostfile);
+
+        oavail = avail = xstrdup(KEX_DEFAULT_PK_ALG);
+        maxlen = strlen(avail) + 1;
+        first = xmalloc(maxlen);
+        last = xmalloc(maxlen);
+        *first = *last = '\0';
+
+#define ALG_APPEND(to, from) \
+        do { \
+                if (*to != '\0') \
+                        strlcat(to, ",", maxlen); \
+                strlcat(to, from, maxlen); \
+        } while (0)
+
+        while ((alg = strsep(&avail, ",")) && *alg != '\0') {
+                if ((ktype = key_type_from_name(alg)) == KEY_UNSPEC)
+                        fatal("%s: unknown alg %s", __func__, alg);
+                if (lookup_key_in_hostkeys_by_type(hostkeys,
+                    key_type_plain(ktype), NULL))
+                        ALG_APPEND(first, alg);
+                else
+                        ALG_APPEND(last, alg);
+        }
+#undef ALG_APPEND
+        xasprintf(&ret, "%s%s%s", first, *first == '\0' ? "" : ",", last);
+        if (*first != '\0')
+                debug3("%s: prefer hostkeyalgs: %s", __func__, first);
+
+        xfree(first);
+        xfree(last);
+        xfree(hostname);
+        xfree(oavail);
+        free_hostkeys(hostkeys);
+
+        return ret;
+}
+
 void
-ssh_kex2(char *host, struct sockaddr *hostaddr)
+ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 {
         Kex *kex;
 
@@ -135,6 +188,11 @@ ssh_kex2(char *host, struct sockaddr *hostaddr)
         if (options.hostkeyalgorithms != NULL)
                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
                     options.hostkeyalgorithms;
+        else {
+                /* Prefer algorithms that we already have keys for */
+                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
+                    order_hostkeyalgs(host, hostaddr, port);
+        }
         if (options.kex_algorithms != NULL)
                 myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;