in _ssh_order_hostkeyalgs() consider ECDSA curve type when arranging

the hostkey algorithms. AFAIK this code is unused in OpenSSH, but I
guess others are using it

based on GHPR387 from Pawel Jakub Dawidek

diff --git a/usr.bin/ssh/ssh_api.c b/usr.bin/ssh/ssh_api.c
index 1a83880..fd02d70 100644 (file)
--- a/usr.bin/ssh/ssh_api.c
+++ b/usr.bin/ssh/ssh_api.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh_api.c,v 1.31 2024/09/09 02:39:57 djm Exp $ */
+/* $OpenBSD: ssh_api.c,v 1.32 2024/10/18 05:14:51 djm Exp $ */
 /*
  * Copyright (c) 2012 Markus Friedl.  All rights reserved.
  *
@@ -526,7 +526,7 @@ _ssh_order_hostkeyalgs(struct ssh *ssh)
        char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
        char **proposal;
        size_t maxlen;
-       int ktype, r;
+       int ktype, nid, r;
 
        /* XXX we de-serialize ssh->kex->my, modify it, and change it */
        if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
@@ -545,15 +545,20 @@ _ssh_order_hostkeyalgs(struct ssh *ssh)
        while ((alg = strsep(&avail, ",")) && *alg != '\0') {
                if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
                        continue;
+               nid = sshkey_ecdsa_nid_from_name(alg);
                TAILQ_FOREACH(k, &ssh->public_keys, next) {
-                       if (k->key->type == ktype ||
-                           (sshkey_is_cert(k->key) && k->key->type ==
-                           sshkey_type_plain(ktype))) {
-                               if (*replace != '\0')
-                                       strlcat(replace, ",", maxlen);
-                               strlcat(replace, alg, maxlen);
-                               break;
-                       }
+                       if (k->key->type != ktype &&
+                           (!sshkey_is_cert(k->key) ||
+                           k->key->type != sshkey_type_plain(ktype)))
+                               continue;
+                       if (sshkey_type_plain(k->key->type) == KEY_ECDSA &&
+                           k->key->ecdsa_nid != nid)
+                               continue;
+                       /* Candidate */
+                       if (*replace != '\0')
+                               strlcat(replace, ",", maxlen);
+                       strlcat(replace, alg, maxlen);
+                       break;
                }
        }
        if (*replace != '\0') {