upstream: revert kex->flags cert hostkey downgrade back to a plain

key (commitid VtF8vozGOF8DMKVg). We now do this a simpler way that needs less
plumbing.

ok markus@

OpenBSD-Commit-ID: fb92d25b216bff8c136da818ac2221efaadf18ed

1 files changed, 12 insertions, 43 deletions

diff --git a/sshconnect.c b/sshconnect.c
index ba07a5ff..4591e6a6 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.336 2020/10/07 02:20:35 djm Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.337 2020/10/07 02:22:23 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -694,10 +694,6 @@ get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
 /*
  * check whether the supplied host key is valid, return -1 if the key
  * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
- *
- * If cert_fallbackp is not NULL then will attempt to convert certificate host
- * keys to plain keys if no certificate match was found and will return
- * non-zero via *cert_fallbackp if this fall-back was used.
  */
 #define RDRW	0
 #define RDONLY	1
@@ -706,7 +702,7 @@ static int
 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
     struct sshkey *host_key, int readonly,
     char **user_hostfiles, u_int num_user_hostfiles,
-    char **system_hostfiles, u_int num_system_hostfiles, int *cert_fallbackp)
+    char **system_hostfiles, u_int num_system_hostfiles)
 {
 	HostStatus host_status;
 	HostStatus ip_status;
@@ -717,15 +713,12 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 	const char *type;
 	const struct hostkey_entry *host_found, *ip_found;
 	int len, cancelled_forwarding = 0, confirmed;
-	int local = sockaddr_is_local(hostaddr), cert_fallback = 0;
+	int local = sockaddr_is_local(hostaddr);
 	int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
 	int hostkey_trusted = 0; /* Known or explicitly accepted by user */
 	struct hostkeys *host_hostkeys, *ip_hostkeys;
 	u_int i;
 
-	if (cert_fallbackp != NULL)
-		*cert_fallbackp = 0;
-
 	/*
 	 * Force accepting of the host key for loopback/localhost. The
 	 * problem is that if the home directory is NFS-mounted to multiple
@@ -841,15 +834,9 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 		if (options.host_key_alias == NULL && port != 0 &&
 		    port != SSH_DEFAULT_PORT) {
 			debug("checking without port identifier");
-			/*
-			 * NB. do not perform cert->key fallback in this
-			 * recursive call. Fallback will only be performed in
-			 * the top-level call.
-			 */
 			if (check_host_key(hostname, hostaddr, 0, host_key,
 			    ROQUIET, user_hostfiles, num_user_hostfiles,
-			    system_hostfiles, num_system_hostfiles,
-			    NULL) == 0) {
+			    system_hostfiles, num_system_hostfiles) == 0) {
 				debug("found matching key w/out port");
 				break;
 			}
@@ -1126,13 +1113,10 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 		free_hostkeys(host_hostkeys);
 	if (ip_hostkeys != NULL)
 		free_hostkeys(ip_hostkeys);
-	if (cert_fallbackp != NULL)
-		*cert_fallbackp = cert_fallback;
 	return 0;
 
 fail:
-	if (cert_fallbackp != NULL && want_cert &&
-	    host_status != HOST_REVOKED) {
+	if (want_cert && host_status != HOST_REVOKED) {
 		/*
 		 * No matching certificate. Downgrade cert to raw key and
 		 * search normally.
@@ -1144,7 +1128,6 @@ fail:
 		if ((r = sshkey_drop_cert(raw_key)) != 0)
 			fatal("Couldn't drop certificate: %s", ssh_err(r));
 		host_key = raw_key;
-		cert_fallback = 1;
 		goto retry;
 	}
 	sshkey_free(raw_key);
@@ -1157,24 +1140,15 @@ fail:
 	return -1;
 }
 
-/*
- * returns 0 if key verifies or -1 if key does NOT verify.
- *
- * If the host key was a certificate that was downgraded to a plain key in
- * the process of matching, then cert_fallbackp will be non-zero.
- */
+/* returns 0 if key verifies or -1 if key does NOT verify */
 int
-verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key,
-    int *cert_fallbackp)
+verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key)
 {
 	u_int i;
-	int r = -1, flags = 0, cert_fallback = 0;
+	int r = -1, flags = 0;
 	char valid[64], *fp = NULL, *cafp = NULL;
 	struct sshkey *plain = NULL;
 
-	if (cert_fallbackp != NULL)
-		*cert_fallbackp = 0;
-
 	if ((fp = sshkey_fingerprint(host_key,
 	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
 		error("%s: fingerprint host key: %s", __func__, ssh_err(r));
@@ -1265,20 +1239,15 @@ verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key,
 	}
 	r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
 	    options.user_hostfiles, options.num_user_hostfiles,
-	    options.system_hostfiles, options.num_system_hostfiles,
-	    &cert_fallback);
+	    options.system_hostfiles, options.num_system_hostfiles);
 
 out:
 	sshkey_free(plain);
 	free(fp);
 	free(cafp);
-	if (r == 0) {
-		if (host_key != NULL) {
-			sshkey_free(previous_host_key);
-			r = sshkey_from_private(host_key, &previous_host_key);
-		}
-		if (r == 0 && cert_fallbackp != NULL)
-			*cert_fallbackp = cert_fallback;
+	if (r == 0 && host_key != NULL) {
+		sshkey_free(previous_host_key);
+		r = sshkey_from_private(host_key, &previous_host_key);
 	}
 
 	return r;