upstream: add CASignatureAlgorithms option for the client, allowing

it to specify which signature algorithms may be used by CAs when signing
certificates. Useful if you want to ban RSA/SHA1; ok markus@

OpenBSD-Commit-ID: 9159e5e9f67504829bf53ff222057307a6e3230f

1 files changed, 13 insertions, 4 deletions

diff --git a/sshconnect.c b/sshconnect.c
index 78813c164..6d819279e 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.304 2018/07/27 05:34:42 dtucker Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.305 2018/09/20 03:30:44 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -734,19 +734,28 @@ confirm(const char *prompt)
 }
 
 static int
-check_host_cert(const char *host, const struct sshkey *host_key)
+check_host_cert(const char *host, const struct sshkey *key)
 {
         const char *reason;
+        int r;
 
-        if (sshkey_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
+        if (sshkey_cert_check_authority(key, 1, 0, host, &reason) != 0) {
                 error("%s", reason);
                 return 0;
         }
-        if (sshbuf_len(host_key->cert->critical) != 0) {
+        if (sshbuf_len(key->cert->critical) != 0) {
                 error("Certificate for %s contains unsupported "
                     "critical options(s)", host);
                 return 0;
         }
+        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));
+                return 0;
+        }
+
         return 1;
 }