From 98963f2771f4ee7ac6c278a1b80f5c5e7ebfaa7d Mon Sep 17 00:00:00 2001
From: jim-p <jimp@pfsense.org>
Date: Mon, 10 Oct 2011 17:18:22 -0400
Subject: Add GUI option to limit the certificate depth allowed when OpenVPN
 clients are connecting.

---
 etc/inc/openvpn.inc                  | 18 +++++++++
 etc/inc/openvpn.tls-verify.php       | 77 ++++++++++++++++++++++++++++++++++++
 usr/local/www/vpn_openvpn_server.php | 30 ++++++++++++++
 3 files changed, 125 insertions(+)
 create mode 100644 etc/inc/openvpn.tls-verify.php

diff --git a/etc/inc/openvpn.inc b/etc/inc/openvpn.inc
index 74b640a..7408d50 100644
--- a/etc/inc/openvpn.inc
+++ b/etc/inc/openvpn.inc
@@ -71,6 +71,14 @@ $openvpn_dev_mode = array("tun", "tap");
 $openvpn_dh_lengths = array(
 	1024, 2048, 4096 );
 
+$openvpn_cert_depths = array(
+	1 => "One (Client+Server)",
+	2 => "Two (Client+Intermediate+Server)",
+	3 => "Three (Client+2xIntermediate+Server)",
+	4 => "Four (Client+3xIntermediate+Server)",
+	5 => "Five (Client+4xIntermediate+Server)"
+);
+
 $openvpn_server_modes = array(
 	'p2p_tls' => gettext("Peer to Peer ( SSL/TLS )"),
 	'p2p_shared_key' => gettext("Peer to Peer ( Shared Key )"),
@@ -447,6 +455,16 @@ function openvpn_reconfigure($mode, $settings) {
 				}
 				break;
 		}
+		if (is_numeric($settings['cert_depth'])) {
+			$sed = "";
+			$cert = lookup_cert($settings['certref']);
+			$servercn = cert_get_cn($cert['crt']);
+			$sed .= "\$server_cn = \"{$servercn}\";\\\n";
+			$sed .= "\$allowed_depth = {$settings['cert_depth']};\\\n";
+			mwexec("/bin/cat /etc/inc/openvpn.tls-verify.php | /usr/bin/sed 's/\/\/<template>/{$sed}/g' >  {$g['varetc_path']}/openvpn/{$mode_id}.tls-verify.php");
+			mwexec("/bin/chmod a+x {$g['varetc_path']}/openvpn/{$mode_id}.tls-verify.php");
+			$conf .= "tls-verify {$g['varetc_path']}/openvpn/{$mode_id}.tls-verify.php\n";
+		}
 
 		// The local port to listen on
 		$conf .= "lport {$settings['local_port']}\n";
diff --git a/etc/inc/openvpn.tls-verify.php b/etc/inc/openvpn.tls-verify.php
new file mode 100644
index 0000000..dd01645
--- /dev/null
+++ b/etc/inc/openvpn.tls-verify.php
@@ -0,0 +1,77 @@
+#!/usr/local/bin/php -f
+<?php
+/* $Id$ */
+/*
+	openvpn.tls-verify.php
+
+	Copyright (C) 2011 Jim Pingle
+	All rights reserved.
+
+	Redistribution and use in source and binary forms, with or without
+	modification, are permitted provided that the following conditions are met:
+
+	1. Redistributions of source code must retain the above copyright notice,
+	   this list of conditions and the following disclaimer.
+
+	2. Redistributions in binary form must reproduce the above copyright
+	   notice, this list of conditions and the following disclaimer in the
+	   documentation and/or other materials provided with the distribution.
+
+	THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+	INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+	AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+	AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+	OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+	SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+	INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+	CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+	ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+	POSSIBILITY OF SUCH DAMAGE.
+
+	DISABLE_PHP_LINT_CHECKING
+*/
+/*
+	pfSense_BUILDER_BINARIES:	
+	pfSense_MODULE:	openvpn
+*/
+/*
+ * OpenVPN calls this script to validate a certificate
+ *  This script is called ONCE per DEPTH of the certificate chain
+ *  Normal operation would have two runs - one for the server certificate
+ *  and one for the client certificate. Beyond that, you're dealing with
+ *  intermediates.
+ */
+
+require_once("globals.inc");
+require_once("config.inc");
+require_once("interfaces.inc");
+
+openlog("openvpn", LOG_ODELAY, LOG_AUTH);
+
+/* read data from command line */
+$cert_depth = intval($argv[1]);
+$cert_subject = $argv[2];
+
+/* Reserved for future use in case we decide to verify CNs and such as well
+$subj = explode("/", $cert_subject);
+foreach ($subj at $s) {
+	list($n, $v) = explode("=", $s);
+	if ($n == "CN")
+		$common_name = $v;
+}
+*/
+
+/* Replaced by sed with proper variables used below ( $server_cn and $allowed_depth ). */
+//<template>
+
+if (isset($allowed_depth) && ($cert_depth > $allowed_depth)) {
+	syslog(LOG_WARNING, "Certificate depth {$cert_depth} exceeded max allowed depth of {$allowed_depth}.\n");
+	exit(1);
+}
+
+// Debug
+syslog(LOG_WARNING, "Found certificate {$argv[2]} with depth {$cert_depth}\n");
+
+exit(0);
+
+?>
diff --git a/usr/local/www/vpn_openvpn_server.php b/usr/local/www/vpn_openvpn_server.php
index 0a50446..b70bbf3 100644
--- a/usr/local/www/vpn_openvpn_server.php
+++ b/usr/local/www/vpn_openvpn_server.php
@@ -123,6 +123,7 @@ if($_GET['act']=="edit"){
 			$pconfig['crlref'] = $a_server[$id]['crlref'];
 			$pconfig['certref'] = $a_server[$id]['certref'];
 			$pconfig['dh_length'] = $a_server[$id]['dh_length'];
+			$pconfig['cert_depth'] = $a_server[$id]['cert_depth'];
 			if ($pconfig['mode'] == "server_tls_user")
 				$pconfig['strictusercn'] = $a_server[$id]['strictusercn'];
 		} else
@@ -317,6 +318,7 @@ if ($_POST) {
 			$server['crlref'] = $pconfig['crlref'];
 			$server['certref'] = $pconfig['certref'];
 			$server['dh_length'] = $pconfig['dh_length'];
+			$server['cert_depth'] = $pconfig['cert_depth'];
 			if ($pconfig['mode'] == "server_tls_user")
 				$server['strictusercn'] = $pconfig['strictusercn'];
 		} else {
@@ -408,6 +410,7 @@ function mode_change() {
 			document.getElementById("tls_crl").style.display="";
 			document.getElementById("tls_cert").style.display="";
 			document.getElementById("tls_dh").style.display="";
+			document.getElementById("cert_depth").style.display="";
 			document.getElementById("strictusercn").style.display="none";
 			document.getElementById("psk").style.display="none";
 			break;
@@ -417,6 +420,7 @@ function mode_change() {
 			document.getElementById("tls_crl").style.display="";
 			document.getElementById("tls_cert").style.display="";
 			document.getElementById("tls_dh").style.display="";
+			document.getElementById("cert_depth").style.display="";
 			document.getElementById("strictusercn").style.display="";
 			document.getElementById("psk").style.display="none";
 			break;
@@ -426,6 +430,7 @@ function mode_change() {
 			document.getElementById("tls_crl").style.display="none";
 			document.getElementById("tls_cert").style.display="none";
 			document.getElementById("tls_dh").style.display="none";
+			document.getElementById("cert_depth").style.display="none";
 			document.getElementById("strictusercn").style.display="none";
 			document.getElementById("psk").style.display="";
 			break;
@@ -921,6 +926,31 @@ if ($savemsg)
 							</select>
 						</td>
 					</tr>
+					<tr id="cert_depth">
+						<td width="22%" valign="top" class="vncell"><?=gettext("Certificate Depth"); ?></td>
+						<td width="78%" class="vtable">
+							<table border="0" cellpadding="2" cellspacing="0">
+							<tr><td>
+							<select name="cert_depth" class="formselect">
+								<option value="">Do Not Check</option>
+								<?php
+									foreach ($openvpn_cert_depths as $depth => $depthdesc):
+									$selected = '';
+									if ($depth == $pconfig['cert_depth'])
+										$selected = ' selected';
+								?>
+								<option value="<?= $depth ?>" <?= $selected ?>><?= $depthdesc ?></option>
+								<?php endforeach; ?>
+							</select>
+							</td></tr>
+							<tr><td>
+							<span class="vexpl">
+								<?=gettext("When a certificate-based client logs in, do not accept certificates below this depth. Useful for denying certificates made with intermediate CAs generated from the same CA as the server."); ?>
+							</span>
+							</td></tr>
+							</table>
+						</td>
+					</tr>
 					<tr id="strictusercn">
 						<td width="22%" valign="top" class="vncell"><?=gettext("Strict User/CN Matching"); ?></td>
 						<td width="78%" class="vtable">
-- 
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