upstream: Add sshd_config CASignatureAlgorithms option to allow

control over which signature algorithms a CA may use when signing
certificates. In particular, this allows a sshd to ban certificates signed
with RSA/SHA1.

ok markus@

OpenBSD-Commit-ID: b05c86ef8b52b913ed48d54a9b9c1a7714d96bac

1 files changed, 8 insertions, 2 deletions

diff --git a/auth2-pubkey.c b/auth2-pubkey.c
index f9e4e2e7f..2fb5950ea 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.85 2018/08/28 12:25:53 mestre Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.86 2018/09/20 03:28:06 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -137,7 +137,13 @@ userauth_pubkey(struct ssh *ssh)
                     __func__, sshkey_ssh_name(key));
                 goto done;
         }
-
+        if ((r = sshkey_check_cert_sigtype(key,
+            options.ca_sign_algorithms)) != 0) {
+                logit("%s: certificate signature algorithm %s: %s", __func__,
+                    (key->cert == NULL || key->cert->signature_type == NULL) ?
+                    "(null)" : key->cert->signature_type, ssh_err(r));
+                goto done;
+        }
         key_s = format_key(key);
         if (sshkey_is_cert(key))
                 ca_s = format_key(key->cert->signature_key);