openvpn: fix config handling on PHP 7.1 #1733

The day has come that this "bootstrap" logic broke horribly,
preventing us from upgrading to PHP 7.1 with the initial 17.7.

Add a config_read_array() function that emulates *all* potentially
required steps and grabs the array reference so that the code can
be migrated easily.

Hopefully this also works on PHP 7.0.  ;)

(cherry picked from commit 4c179c23)

src/etc/inc/config.inc

@@ -278,6 +278,22 @@ function cleanup_backups()
     }
 }
 
+function &config_read_array()
+{
+    global $config;
+
+    $current = &$config;
+
+    foreach (func_get_args() as $key) {
+        if (!isset($current[$key]) || !is_array($current[$key])) {
+            $current[$key] = array();
+        }
+        $current = &$current[$key];
+    }
+
+    return $current;
+}
+
 function make_config_revision_entry($desc = '')
 {
     if (!empty($_SESSION['Username'])) {

src/www/vpn_openvpn_client.php

@@ -32,11 +32,7 @@ require_once("plugins.inc.d/openvpn.inc");
 require_once("services.inc");
 require_once("interfaces.inc");
 
-if (!isset($config['openvpn']['openvpn-client'])) {
-    $config['openvpn']['openvpn-client'] = array();
-}
-
-$a_client = &$config['openvpn']['openvpn-client'];
+$a_client = &config_read_array('openvpn', 'openvpn-client');
 
 $vpnid = 0;
 $act = null;

src/www/vpn_openvpn_csc.php

@@ -32,7 +32,6 @@ require_once("plugins.inc.d/openvpn.inc");
 require_once("services.inc");
 require_once("interfaces.inc");
 
-// define all fields used in this form
 $all_form_fields = "custom_options,disable,common_name,block,description
     ,tunnel_network,tunnel_networkv6,local_network,local_networkv6,remote_network
     ,remote_networkv6,gwredir,push_reset,dns_domain,dns_server1
@@ -40,11 +39,7 @@ $all_form_fields = "custom_options,disable,common_name,block,description
     ,netbios_enable,netbios_ntype,netbios_scope,wins_server1
     ,wins_server2,ovpn_servers";
 
-// read config.
-if (!isset($config['openvpn']['openvpn-csc'])) {
-    $config['openvpn']['openvpn-csc'] = array();
-}
-$a_csc = &$config['openvpn']['openvpn-csc'];
+$a_csc = &config_read_array('openvpn', 'openvpn-csc');
 
 $vpnid = 0;
 $act=null;

src/www/vpn_openvpn_server.php

@@ -32,10 +32,7 @@ require_once("plugins.inc.d/openvpn.inc");
 require_once("services.inc");
 require_once("interfaces.inc");
 
-if (!isset($config['openvpn']['openvpn-server'])) {
-    $config['openvpn']['openvpn-server'] = array();
-}
-$a_server = &$config['openvpn']['openvpn-server'];
+$a_server = &config_read_array('openvpn', 'openvpn-server');
 
 $act = null;
 if ($_SERVER['REQUEST_METHOD'] === 'GET') {