3 files changed, 31 insertions, 6 deletions

diff --git a/hostfile.c b/hostfile.c
index a4a355972..a91dbbd94 100644
--- a/hostfile.c
+++ b/hostfile.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: hostfile.c,v 1.79 2020/03/06 18:25:12 markus Exp $ */
+/* $OpenBSD: hostfile.c,v 1.80 2020/05/13 09:52:41 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -406,6 +406,18 @@ lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
             found) == HOST_FOUND);
 }
 
+int
+lookup_marker_in_hostkeys(struct hostkeys *hostkeys, int want_marker)
+{
+        u_int i;
+
+        for (i = 0; i < hostkeys->num_entries; i++) {
+                if (hostkeys->entries[i].marker == (HostkeyMarker)want_marker)
+                        return 1;
+        }
+        return 0;
+}
+
 static int
 write_host_entry(FILE *f, const char *host, const char *ip,
     const struct sshkey *key, int store_hash)
diff --git a/hostfile.h b/hostfile.h
index bd2104373..49fcbb7e8 100644
--- a/hostfile.h
+++ b/hostfile.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: hostfile.h,v 1.24 2015/02/16 22:08:57 djm Exp $ */
+/* $OpenBSD: hostfile.h,v 1.25 2020/05/13 09:52:41 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -39,6 +39,7 @@ HostStatus check_key_in_hostkeys(struct hostkeys *, struct sshkey *,
     const struct hostkey_entry **);
 int      lookup_key_in_hostkeys_by_type(struct hostkeys *, int,
     const struct hostkey_entry **);
+int      lookup_marker_in_hostkeys(struct hostkeys *, int);
 
 int      hostfile_read_key(char **, u_int *, struct sshkey *);
 int      add_host_to_hostfile(const char *, const char *,
diff --git a/sshconnect2.c b/sshconnect2.c
index 1a6545edf..08b4f8550 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.321 2020/04/17 03:38:47 djm Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.322 2020/05/13 09:52:41 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -135,11 +135,23 @@ order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
                 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
                         fatal("%s: unknown alg %s", __func__, alg);
+                /*
+                 * If we have a @cert-authority marker in known_hosts then
+                 * prefer all certificate algorithms.
+                 */
+                if (sshkey_type_is_cert(ktype) &&
+                    lookup_marker_in_hostkeys(hostkeys, MRK_CA)) {
+                        ALG_APPEND(first, alg);
+                        continue;
+                }
+                /* If the key appears in known_hosts then prefer it */
                 if (lookup_key_in_hostkeys_by_type(hostkeys,
-                    sshkey_type_plain(ktype), NULL))
+                    sshkey_type_plain(ktype), NULL)) {
                         ALG_APPEND(first, alg);
-                else
-                        ALG_APPEND(last, alg);
+                        continue;
+                }
+                /* Otherwise, put it last */
+                ALG_APPEND(last, alg);
         }
 #undef ALG_APPEND
         xasprintf(&ret, "%s%s%s", first,