upstream commit

When updating hostkeys, accept RSA keys if
HostkeyAlgorithms contains any RSA keytype. Previously, ssh could ignore RSA
keys when any of the ssh-rsa-sha2-* methods was enabled in HostkeyAlgorithms
nit ssh-rsa (SHA1 signatures) was not. bz#2650 reported by Luis Ressel; ok
dtucker@

Upstream-ID: c5e8cfee15c42f4a05d126158a0766ea06da79d2

1 files changed, 22 insertions, 5 deletions

diff --git a/clientloop.c b/clientloop.c
index c6a41386d..064816234 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.290 2017/01/29 21:35:23 dtucker Exp $ */
+/* $OpenBSD: clientloop.c,v 1.291 2017/03/10 05:01:13 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2391,6 +2391,26 @@ client_global_hostkeys_private_confirm(int type, u_int32_t seq, void *_ctx)
 }
 
 /*
+ * Returns non-zero if the key is accepted by HostkeyAlgorithms.
+ * Made slightly less trivial by the multiple RSA signature algorithm names.
+ */
+static int
+key_accepted_by_hostkeyalgs(const struct sshkey *key)
+{
+        const char *ktype = sshkey_ssh_name(key);
+        const char *hostkeyalgs = options.hostkeyalgorithms != NULL ?
+            options.hostkeyalgorithms : KEX_DEFAULT_PK_ALG;
+
+        if (key == NULL || key->type == KEY_UNSPEC)
+                return 0;
+        if (key->type == KEY_RSA &&
+            (match_pattern_list("rsa-sha2-256", hostkeyalgs, 0) == 1 ||
+            match_pattern_list("rsa-sha2-512", hostkeyalgs, 0) == 1))
+                return 1;
+        return match_pattern_list(ktype, hostkeyalgs, 0) == 1;
+}
+
+/*
  * Handle hostkeys-00@openssh.com global request to inform the client of all
  * the server's hostkeys. The keys are checked against the user's
  * HostkeyAlgorithms preference before they are accepted.
@@ -2436,10 +2456,7 @@ client_input_hostkeys(void)
                     sshkey_type(key), fp);
                 free(fp);
 
-                /* Check that the key is accepted in HostkeyAlgorithms */
-                if (match_pattern_list(sshkey_ssh_name(key),
-                    options.hostkeyalgorithms ? options.hostkeyalgorithms :
-                    KEX_DEFAULT_PK_ALG, 0) != 1) {
+                if (!key_accepted_by_hostkeyalgs(key)) {
                         debug3("%s: %s key not permitted by HostkeyAlgorithms",
                             __func__, sshkey_ssh_name(key));
                         continue;