upstream: disable UpdateHostkeys when a wildcard hostname pattern

is encountered or when a certificate host key is in use. feedback/ok markus@

OpenBSD-Commit-ID: b6e5575af7e6732322be82ec299e09051a5413bd

diff --git a/clientloop.c b/clientloop.c
index 60b46d1616c8afc8171d2977b1e45436673367ba..de13adab9e54afc563d49e954a8810fbad12dcbe 100644 (file)
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.346 2020/09/16 03:07:31 dtucker Exp $ */
+/* $OpenBSD: clientloop.c,v 1.347 2020/10/03 08:12:59 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1828,6 +1828,10 @@ struct hostkeys_update_ctx {
         */
        struct sshkey **old_keys;
        size_t nold;
+
+       /* Various special cases. */
+       int wildcard_hostspec;  /* saw wildcard or pattern-list host name */
+       int ca_available;       /* saw CA key for this host */
 };
 
 static void
@@ -1859,6 +1863,21 @@ hostkeys_find(struct hostkey_foreach_line *l, void *_ctx)
        if (l->status != HKF_STATUS_MATCHED || l->key == NULL)
                return 0;
 
+       if (l->marker == MRK_REVOKE)
+               return 0;
+       if (l->marker == MRK_CA) {
+               ctx->ca_available = 1;
+               return 0;
+       }
+
+       /* UpdateHostkeys is skipped for wildcard host names */
+       if (strchr(l->hosts, '*') != NULL ||
+           strchr(l->hosts, ',') != NULL) {
+               debug3("%s: hostkeys file %s:%ld contains wildcard or pattern",
+                    __func__, l->path, l->linenum);
+               ctx->wildcard_hostspec = 1;
+       }
+
        /* Mark off keys we've already seen for this host */
        for (i = 0; i < ctx->nkeys; i++) {
                if (sshkey_equal(l->key, ctx->keys[i])) {
@@ -2204,7 +2223,17 @@ client_input_hostkeys(struct ssh *ssh)
        debug3("%s: %zu keys from server: %zu new, %zu retained. %zu to remove",
            __func__, ctx->nkeys, ctx->nnew, ctx->nkeys - ctx->nnew, ctx->nold);
 
-       if (ctx->nnew == 0 && ctx->nold != 0) {
+       if (ctx->wildcard_hostspec && (ctx->nnew != 0 || ctx->nold != 0)) {
+               debug("%s: wildcard known hosts name found, "
+                   "skipping UserKnownHostsFile update", __func__);
+               goto out;
+       } else if (sshkey_type_is_cert(ssh->kex->hostkey_type) &&
+           ctx->ca_available &&
+           (ssh->kex->flags & KEX_HOSTCERT_CONVERT) == 0) {
+               debug("%s: server offered certificate host key, "
+                   "skipping UserKnownHostsFile update", __func__);
+               goto out;
+       } else if (ctx->nnew == 0 && ctx->nold != 0) {
                /* We have some keys to remove. Just do it. */
                update_known_hosts(ctx);
        } else if (ctx->nnew != 0) {