- djm@cvs.openbsd.org 2014/04/01 03:34:10
[sshconnect.c]
When using VerifyHostKeyDNS with a DNSSEC resolver, down-convert any
certificate keys to plain keys and attempt SSHFP resolution.
Prevents a server from skipping SSHFP lookup and forcing a new-hostkey
dialog by offering only certificate keys.
Reported by mcv21 AT cam.ac.uk
diff --git a/sshconnect.c b/sshconnect.c
index 573d7a8..ca6e4cc 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.246 2014/02/06 22:21:01 djm Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.247 2014/04/01 03:34:10 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1219,29 +1219,39 @@
{
int flags = 0;
char *fp;
+ Key *plain = NULL;
fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
debug("Server host key: %s %s", key_type(host_key), fp);
free(fp);
- /* XXX certs are not yet supported for DNS */
- if (!key_is_cert(host_key) && options.verify_host_key_dns &&
- verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
- if (flags & DNS_VERIFY_FOUND) {
-
- if (options.verify_host_key_dns == 1 &&
- flags & DNS_VERIFY_MATCH &&
- flags & DNS_VERIFY_SECURE)
- return 0;
-
- if (flags & DNS_VERIFY_MATCH) {
- matching_host_key_dns = 1;
- } else {
- warn_changed_key(host_key);
- error("Update the SSHFP RR in DNS with the new "
- "host key to get rid of this message.");
+ if (options.verify_host_key_dns) {
+ /*
+ * XXX certs are not yet supported for DNS, so downgrade
+ * them and try the plain key.
+ */
+ plain = key_from_private(host_key);
+ if (key_is_cert(plain))
+ key_drop_cert(plain);
+ if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
+ if (flags & DNS_VERIFY_FOUND) {
+ if (options.verify_host_key_dns == 1 &&
+ flags & DNS_VERIFY_MATCH &&
+ flags & DNS_VERIFY_SECURE) {
+ key_free(plain);
+ return 0;
+ }
+ if (flags & DNS_VERIFY_MATCH) {
+ matching_host_key_dns = 1;
+ } else {
+ warn_changed_key(plain);
+ error("Update the SSHFP RR in DNS "
+ "with the new host key to get rid "
+ "of this message.");
+ }
}
}
+ key_free(plain);
}
return check_host_key(host, hostaddr, options.port, host_key, RDRW,