From b64faeb5eda7eff8210c754d00464f9fe9d23de5 Mon Sep 17 00:00:00 2001
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Fri, 17 Jun 2016 05:03:40 +0000
Subject: upstream commit

ban AuthenticationMethods="" and accept
AuthenticationMethods=any for the default behaviour of not requiring multiple
authentication

bz#2398 from Jakub Jelen; ok dtucker@

Upstream-ID: fabd7f44d59e4518d241d0d01e226435cc23cf27
---
 servconf.c    | 34 +++++++++++++++++++++++++++++++---
 sshd_config.5 | 17 +++++++++++------
 2 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/servconf.c b/servconf.c
index 1cb45f536..a411bfb6e 100644
--- a/servconf.c
+++ b/servconf.c
@@ -1,5 +1,5 @@
 
-/* $OpenBSD: servconf.c,v 1.290 2016/05/04 14:00:09 dtucker Exp $ */
+/* $OpenBSD: servconf.c,v 1.291 2016/06/17 05:03:40 djm Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -381,6 +381,14 @@ fill_default_server_options(ServerOptions *options)
 		CLEAR_ON_NONE(options->host_cert_files[i]);
 #undef CLEAR_ON_NONE
 
+	/* Similar handling for AuthenticationMethods=any */
+	if (options->num_auth_methods == 1 &&
+	    strcmp(options->auth_methods[0], "any") == 0) {
+		free(options->auth_methods[0]);
+		options->auth_methods[0] = NULL;
+		options->num_auth_methods = 0;
+	}
+
 #ifndef HAVE_MMAP
 	if (use_privsep && options->compression == 1) {
 		error("This platform does not support both privilege "
@@ -1804,21 +1812,39 @@ process_server_config_line(ServerOptions *options, char *line,
 
 	case sAuthenticationMethods:
 		if (options->num_auth_methods == 0) {
+			value = 0; /* seen "any" pseudo-method */
 			while ((arg = strdelim(&cp)) && *arg != '\0') {
 				if (options->num_auth_methods >=
 				    MAX_AUTH_METHODS)
 					fatal("%s line %d: "
 					    "too many authentication methods.",
 					    filename, linenum);
-				if (auth2_methods_valid(arg, 0) != 0)
+				if (strcmp(arg, "any") == 0) {
+					if (options->num_auth_methods > 0) {
+						fatal("%s line %d: \"any\" "
+						    "must appear alone in "
+						    "AuthenticationMethods",
+						    filename, linenum);
+					}
+					value = 1;
+				} else if (value) {
+					fatal("%s line %d: \"any\" must appear "
+					    "alone in AuthenticationMethods",
+					    filename, linenum);
+				} else if (auth2_methods_valid(arg, 0) != 0) {
 					fatal("%s line %d: invalid "
 					    "authentication method list.",
 					    filename, linenum);
+				}
 				if (!*activep)
 					continue;
 				options->auth_methods[
 				    options->num_auth_methods++] = xstrdup(arg);
 			}
+			if (options->num_auth_methods == 0) {
+				fatal("%s line %d: no AuthenticationMethods "
+				    "specified", filename, linenum);
+			}
 		}
 		return 0;
 
@@ -2195,11 +2221,13 @@ dump_cfg_strarray_oneline(ServerOpCodes code, u_int count, char **vals)
 {
 	u_int i;
 
-	if (count <= 0)
+	if (count <= 0 && code != sAuthenticationMethods)
 		return;
 	printf("%s", lookup_opcode_name(code));
 	for (i = 0; i < count; i++)
 		printf(" %s",  vals[i]);
+	if (code == sAuthenticationMethods && count == 0)
+		printf(" any");
 	printf("\n");
 }
 
diff --git a/sshd_config.5 b/sshd_config.5
index 479fa38eb..690797958 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: sshd_config.5,v 1.223 2016/05/04 14:29:58 markus Exp $
-.Dd $Mdocdate: May 4 2016 $
+.\" $OpenBSD: sshd_config.5,v 1.224 2016/06/17 05:03:40 djm Exp $
+.Dd $Mdocdate: June 17 2016 $
 .Dt SSHD_CONFIG 5
 .Os
 .Sh NAME
@@ -189,9 +189,12 @@ for more information on patterns.
 Specifies the authentication methods that must be successfully completed
 for a user to be granted access.
 This option must be followed by one or more comma-separated lists of
-authentication method names.
-Successful authentication requires completion of every method in at least
-one of these lists.
+authentication method names, or by the single string
+.Dq any
+to indicate the default behaviour of accepting any single authentication
+methods.
+if the default is overridden, then successful authentication requires
+completion of every method in at least one of these lists.
 .Pp
 For example, an argument of
 .Dq publickey,password publickey,keyboard-interactive
@@ -231,7 +234,9 @@ This option will yield a fatal
 error if enabled if protocol 1 is also enabled.
 Note that each authentication method listed should also be explicitly enabled
 in the configuration.
-The default is not to require multiple authentication; successful completion
+The default
+.Dq any
+is not to require multiple authentication; successful completion
 of a single authentication method is sufficient.
 .It Cm AuthorizedKeysCommand
 Specifies a program to be used to look up the user's public keys.
-- 
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