--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/http_authentication/http_authentication.php	Thu Jan 04 15:50:29 2018 -0500
@@ -0,0 +1,106 @@
+<?php
+
+/**
+ * HTTP Basic Authentication
+ *
+ * Make use of an existing HTTP authentication and perform login with the existing user credentials
+ *
+ * Configuration:
+ * // redirect the client to this URL after logout. This page is then responsible to clear HTTP auth
+ * $config['logout_url'] = 'http://server.tld/logout.html';
+ *
+ * See logout.html (in this directory) for an example how HTTP auth can be cleared.
+ *
+ * For other configuration options, see config.inc.php.dist!
+ *
+ * @license GNU GPLv3+
+ * @author Thomas Bruederli
+ */
+class http_authentication extends rcube_plugin
+{
+    private $redirect_query;
+
+    function init()
+    {
+        $this->add_hook('startup', array($this, 'startup'));
+        $this->add_hook('authenticate', array($this, 'authenticate'));
+        $this->add_hook('logout_after', array($this, 'logout'));
+        $this->add_hook('login_after', array($this, 'login'));
+    }
+
+    function startup($args)
+    {
+        if (!empty($_SERVER['PHP_AUTH_USER'])) {
+            $rcmail = rcmail::get_instance();
+            $rcmail->add_shutdown_function(array('http_authentication', 'shutdown'));
+
+            // handle login action
+            if (empty($_SESSION['user_id'])) {
+                $args['action']         = 'login';
+                $this->redirect_query   = $_SERVER['QUERY_STRING'];
+            }
+            // Set user password in session (see shutdown() method for more info)
+            else if (!empty($_SESSION['user_id']) && empty($_SESSION['password'])
+                     && !empty($_SERVER['PHP_AUTH_PW'])) {
+                $_SESSION['password'] = $rcmail->encrypt($_SERVER['PHP_AUTH_PW']);
+            }
+        }
+
+        return $args;
+    }
+
+    function authenticate($args)
+    {
+        // Load plugin's config file
+        $this->load_config();
+
+        $host = rcmail::get_instance()->config->get('http_authentication_host');
+        if (is_string($host) && trim($host) !== '' && empty($args['host']))
+            $args['host'] = rcube_utils::idn_to_ascii(rcube_utils::parse_host($host));
+
+        // Allow entering other user data in login form,
+        // e.g. after log out (#1487953)
+        if (!empty($args['user'])) {
+            return $args;
+        }
+
+        if (!empty($_SERVER['PHP_AUTH_USER'])) {
+            $args['user'] = $_SERVER['PHP_AUTH_USER'];
+            if (!empty($_SERVER['PHP_AUTH_PW']))
+                $args['pass'] = $_SERVER['PHP_AUTH_PW'];
+        }
+
+        $args['cookiecheck'] = false;
+        $args['valid'] = true;
+
+        return $args;
+    }
+
+    function logout($args)
+    {
+        // redirect to configured URL in order to clear HTTP auth credentials
+        if (!empty($_SERVER['PHP_AUTH_USER']) && $args['user'] == $_SERVER['PHP_AUTH_USER']) {
+            if ($url = rcmail::get_instance()->config->get('logout_url')) {
+                header("Location: $url", true, 307);
+            }
+        }
+    }
+
+    function shutdown()
+    {
+        // There's no need to store password (even if encrypted) in session
+        // We'll set it back on startup (#1486553)
+        rcmail::get_instance()->session->remove('password');
+    }
+
+    function login($args)
+    {
+        // Redirect to the previous QUERY_STRING
+        if($this->redirect_query){
+            header('Location: ./?' . $this->redirect_query);
+            exit;
+        }
+        return $args;
+    }
+}
+