upstream: Add server debugging for hostbased auth.

auth_debug_add queues messages about the auth process which is sent to
the client after successful authentication.  This also sends those to
the server debug log to aid in debugging.  From bz#3507, ok djm@

OpenBSD-Commit-ID: 46ff67518cccf9caf47e06393e2a121ee5aa258a

auth-rhosts.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth-rhosts.c,v 1.56 2022/02/23 21:21:49 djm Exp $ */
+/* $OpenBSD: auth-rhosts.c,v 1.57 2022/12/09 00:17:40 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <[email protected]>
  * Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
@@ -19,6 +19,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 
+#include <errno.h>
 #include <fcntl.h>
 #ifdef HAVE_NETGROUP_H
 # include <netgroup.h>
@@ -283,6 +284,7 @@ auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
 		xasprintf(&path, "%s/%s",
 		    pw->pw_dir, rhosts_files[rhosts_file_index]);
 		if (stat(path, &st) == -1) {
+			debug3_f("stat %s: %s", path, strerror(errno));
 			free(path);
 			continue;
 		}

auth.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.c,v 1.158 2022/06/03 04:47:21 djm Exp $ */
+/* $OpenBSD: auth.c,v 1.159 2022/12/09 00:17:40 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -571,14 +571,13 @@ auth_debug_add(const char *fmt,...)
 	va_list args;
 	int r;
 
-	if (auth_debug == NULL)
-		return;
-
 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
-	if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
-		fatal_fr(r, "sshbuf_put_cstring");
+	debug3("%s", buf);
+	if (auth_debug != NULL)
+		if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
+			fatal_fr(r, "sshbuf_put_cstring");
 }
 
 void