1 files changed, 643 insertions, 412 deletions
diff --git a/engine/lib/sessions.php b/engine/lib/sessions.php
index 02a3e06ca..e3d5ce9cd 100644
--- a/engine/lib/sessions.php
+++ b/engine/lib/sessions.php
@@ -1,425 +1,656 @@
-<?php
-
-	/**
-	 * Elgg session management
-	 * Functions to manage logins
-	 * 
-	 * @package Elgg
-	 * @subpackage Core
-	 * @license http://www.gnu.org/licenses/old-licenses/gpl-2.0.html GNU Public License version 2
-	 * @author Curverider Ltd
-	 * @copyright Curverider Ltd 2008
-	 * @link http://elgg.org/
-	 */
-
-	/**
-	 * Returns whether or not the user is currently logged in
-	 *
-	 * @uses $_SESSION
-	 * @return true|false
-	 */
-		function isloggedin() {
-			
-			if (!is_installed()) return false;
-			if ((isset($_SESSION['guid'])) && ($_SESSION['guid'] > 0) && (isset($_SESSION['id'])) && ($_SESSION['id'] > 0) )
-			
-				return true;
-			return false;
-			
-		}
-
-	/**
-	 * Returns whether or not the user is currently logged in and that they are an admin user.
-	 *
-	 * @uses $_SESSION
-	 * @uses isloggedin()
-	 * @return true|false
-	 */
-		function isadminloggedin()
-		{
-			if ((isloggedin()) && (($_SESSION['user']->admin || $_SESSION['user']->siteadmin)))
-				return true;
-				
-			return false;
-		}
-		
-	/**
-	 * Perform standard authentication with a given username and password.
-	 * Returns an ElggUser object for use with login.
-	 *
-	 * @see login
-	 * @param string $username The username, optionally (for standard logins)
-	 * @param string $password The password, optionally (for standard logins)
-	 * @return ElggUser|false The authenticated user object, or false on failure.
-	 */
-		
-		function authenticate($username, $password) {
-            
-			if (pam_authenticate(array('username' => $username, 'password' => $password)))
-				return get_user_by_username($username);
-            
-            return false;
-			
-		}
-		
-		/**
-		 * Hook into the PAM system which accepts a username and password and attempts to authenticate
-		 * it against a known user.
-		 *
-		 * @param array $credentials Associated array of credentials passed to pam_authenticate. This function expects
-		 * 		'username' and 'password' (cleartext).
-		 */
-		function pam_auth_userpass($credentials = NULL)
-		{
-			if (is_array($credentials) && ($credentials['username']) && ($credentials['password']))
-			{
-				//$dbpassword = md5($credentials['password']);
-            
-				
-	            if ($user = get_user_by_username($credentials['username'])) {
-	            	// Let admins log in without validating their email, but normal users must have validated their email
-					if ((!$user->admin) && (!$user->validated) && (!$user->admin_created))
-						return false;
-	          	
-	                 if ($user->password == generate_user_password($user, $credentials['password'])) {
-	                 	return true;
-	                 }
-	            }
-			}
-			
-			return false;
-		}
-		
-	/**
-	 * Logs in a specified ElggUser. For standard registration, use in conjunction
-	 * with authenticate.
-	 * 
-	 * @see authenticate
-	 * @param ElggUser $user A valid Elgg user object
-	 * @param boolean $persistent Should this be a persistent login?
-	 * @return true|false Whether login was successful
-	 */
-		function login(ElggUser $user, $persistent = false) {
-            
-            global $CONFIG;
-          
-            $_SESSION['user'] = $user;
-            $_SESSION['guid'] = $user->getGUID();
-            $_SESSION['id'] = $_SESSION['guid'];
-            $_SESSION['username'] = $user->username;
-            $_SESSION['name'] = $user->name;
-                     
-            $code = (md5($user->name . $user->username . time() . rand()));
-
-            $user->code = md5($code);
-            
-            $_SESSION['code'] = $code;
-            
-            if (($persistent))
-				setcookie("elggperm", $code, (time()+(86400 * 30)),"/");
-         
-            if (!$user->save() || !trigger_elgg_event('login','user',$user)) {
-            	unset($_SESSION['username']);
-	            unset($_SESSION['name']);
-	            unset($_SESSION['code']);
-	            unset($_SESSION['guid']);
-	            unset($_SESSION['id']);
-	            unset($_SESSION['user']);
-	            setcookie("elggperm", "", (time()-(86400 * 30)),"/");
-            	return false;
-            }
-            
-            // Users privilege has been elevated, so change the session id (help prevent session hijacking)
-	        session_regenerate_id(); 
-
-			return true;
-				
-		}
-        
-	/**
-	 * Log the current user out
-	 *
-	 * @return true|false
-	 */
-		function logout() {
-            global $CONFIG;
-
-            if (isset($_SESSION['user'])) {
-            	if (!trigger_elgg_event('logout','user',$_SESSION['user'])) return false;
-            	$_SESSION['user']->code = "";
-            	$_SESSION['user']->save();
-            }
-            
-            unset($_SESSION['username']);
-            unset($_SESSION['name']);
-            unset($_SESSION['code']);
-            unset($_SESSION['guid']);
-            unset($_SESSION['id']);
-            unset($_SESSION['user']);
-            
-            setcookie("elggperm", "", (time()-(86400 * 30)),"/");
-            
-            session_destroy();
-            
-            return true;
-        }
-        
-        function get_session_fingerprint()
-        {
-        	global $CONFIG;
-        	
-        	return md5($_SERVER['HTTP_USER_AGENT'] );
-        }
-		
-	/**
-	 * Initialises the system session and potentially logs the user in
-	 * 
-	 * This function looks for:
-	 * 
-	 * 1. $_SESSION['id'] - if not present, we're logged out, and this is set to 0
-	 * 2. The cookie 'elggperm' - if present, checks it for an authentication token, validates it, and potentially logs the user in 
-	 *
-	 * @uses $_SESSION
-	 * @param unknown_type $event
-	 * @param unknown_type $object_type
-	 * @param unknown_type $object
-	 */
-		function session_init($event, $object_type, $object) {
-			
-			global $DB_PREFIX, $CONFIG;
-			
-			if (!is_db_installed()) return false;
-			
-			// Use database for sessions
-			$DB_PREFIX = $CONFIG->dbprefix; // HACK to allow access to prefix after object distruction
-			session_set_save_handler("__elgg_session_open", "__elgg_session_close", "__elgg_session_read", "__elgg_session_write", "__elgg_session_destroy", "__elgg_session_gc");
-				
-			session_name('Elgg');
-	        session_start();
-	        
-	        // Do some sanity checking by generating a fingerprint (makes some XSS attacks harder)
-	        if (isset($_SESSION['__elgg_fingerprint']))
-			{
-			    if ($_SESSION['__elgg_fingerprint'] != get_session_fingerprint())
-			    {
-			    	session_destroy();
-			    	return false;
-			    }
-			}
-			else
-			{
-			    $_SESSION['__elgg_fingerprint'] = get_session_fingerprint();
-			}
-			
-			// Generate a simple token
-			if (!isset($_SESSION['__elgg_session'])) $_SESSION['__elgg_session'] = md5(microtime().rand());
-	        
-	        if (empty($_SESSION['guid'])) {
-	            if (isset($_COOKIE['elggperm'])) {            
-	                $code = $_COOKIE['elggperm'];
-	                $code = md5($code);
-	                $_SESSION['guid'] = 0;
-	                $_SESSION['id'] = 0;
-	                // $_SESSION['user'] = new ElggDummy();
-	                if ($user = get_user_by_code($code)) {
-                    	$_SESSION['user'] = $user;
-                        $_SESSION['id'] = $user->getGUID();
-                        $_SESSION['guid'] = $_SESSION['id'];
-                        $_SESSION['code'] = $_COOKIE['elggperm'];
-	                }
-	            } else {
-	            	//$_SESSION['user'] = new ElggDummy();
-	                $_SESSION['id'] = 0;
-	                $_SESSION['guid'] = 0;
-	                $_SESSION['code'] = "";
-	            }
-	        } else {
-	            if (!empty($_SESSION['code'])) {
-	                $code = md5($_SESSION['code']);
-	                if ($user = get_user_by_code($code)) {
-	                	$_SESSION['user'] = $user;
-	                	$_SESSION['id'] = $user->getGUID();
-                        $_SESSION['guid'] = $_SESSION['id'];
-	                } else {
-	                	unset($_SESSION['user']);
-	                	// $_SESSION['user'] = new ElggDummy();
-	                	$_SESSION['guid'] = 0;
-	                	$_SESSION['id'] = 0;
-	                	$_SESSION['code'] = "";
-	                }
-	            } else {
-	            	//$_SESSION['user'] = new ElggDummy();
-	            	$_SESSION['guid'] = 0;
-	                $_SESSION['id'] = 0;
-	                $_SESSION['code'] = "";
-	            }
-	        }
-	        if ($_SESSION['id'] > 0) {
-	            set_last_action($_SESSION['id']);
-	        }
-	        
-	        register_action("login",true);
-    		register_action("logout");
-    		
-    		// Register a default PAM handler
-    		register_pam_handler('pam_auth_userpass');
-    		
-    		return true;
-	        
-		}
-
-	/**
-	 * Used at the top of a page to mark it as logged in users only.
-	 *
-	 */
-		function gatekeeper() {
-			if (!isloggedin()) {
-				$_SESSION['last_forward_from'] = current_page_url();
-				forward();
-			}
-		}
-		
-		/**
-		 * Used at the top of a page to mark it as logged in admin or siteadmin only.
-		 *
-		 */
-		function admin_gatekeeper()
-		{
-			gatekeeper();
-			if (!$_SESSION['user']->admin && !$_SESSION['user']->siteadmin) {
-				$_SESSION['last_forward_from'] = current_page_url();
-				forward();
+<?php
+
+/**
+ * Elgg session management
+ * Functions to manage logins
+ *
+ * @package Elgg.Core
+ * @subpackage Session
+ */
+
+/** Elgg magic session */
+global $SESSION;
+
+/**
+ * Return the current logged in user, or NULL if no user is logged in.
+ *
+ * If no user can be found in the current session, a plugin
+ * hook - 'session:get' 'user' to give plugin authors another
+ * way to provide user details to the ACL system without touching the session.
+ *
+ * @return ElggUser
+ */
+function elgg_get_logged_in_user_entity() {
+	global $SESSION;
+
+	if (isset($SESSION)) {
+		return $SESSION['user'];
+	}
+
+	return NULL;
+}
+
+/**
+ * Return the current logged in user by id.
+ *
+ * @see elgg_get_logged_in_user_entity()
+ * @return int
+ */
+function elgg_get_logged_in_user_guid() {
+	$user = elgg_get_logged_in_user_entity();
+	if ($user) {
+		return $user->guid;
+	}
+
+	return 0;
+}
+
+/**
+ * Returns whether or not the user is currently logged in
+ *
+ * @return bool
+ */
+function elgg_is_logged_in() {
+	$user = elgg_get_logged_in_user_entity();
+
+	if ((isset($user)) && ($user instanceof ElggUser) && ($user->guid > 0)) {
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * Returns whether or not the user is currently logged in and that they are an admin user.
+ *
+ * @return bool
+ */
+function elgg_is_admin_logged_in() {
+	$user = elgg_get_logged_in_user_entity();
+
+	if ((elgg_is_logged_in()) && $user->isAdmin()) {
+		return TRUE;
+	}
+
+	return FALSE;
+}
+
+/**
+ * Check if the given user has full access.
+ *
+ * @todo: Will always return full access if the user is an admin.
+ *
+ * @param int $user_guid The user to check
+ *
+ * @return bool
+ * @since 1.7.1
+ */
+function elgg_is_admin_user($user_guid) {
+	global $CONFIG;
+
+	$user_guid = (int)$user_guid;
+
+	// cannot use magic metadata here because of recursion
+
+	// must support the old way of getting admin from metadata
+	// in order to run the upgrade to move it into the users table.
+	$version = (int) datalist_get('version');
+
+	if ($version < 2010040201) {
+		$admin = get_metastring_id('admin');
+		$yes = get_metastring_id('yes');
+		$one = get_metastring_id('1');
+
+		$query = "SELECT * FROM {$CONFIG->dbprefix}users_entity as e,
+			{$CONFIG->dbprefix}metadata as md
+			WHERE (
+				md.name_id = '$admin'
+				AND md.value_id IN ('$yes', '$one')
+				AND e.guid = md.entity_guid
+				AND e.guid = {$user_guid}
+				AND e.banned = 'no'
+			)";
+	} else {
+		$query = "SELECT * FROM {$CONFIG->dbprefix}users_entity as e
+			WHERE (
+				e.guid = {$user_guid}
+				AND e.admin = 'yes'
+			)";
+	}
+
+	// normalizing the results from get_data()
+	// See #1242
+	$info = get_data($query);
+	if (!((is_array($info) && count($info) < 1) || $info === FALSE)) {
+		return TRUE;
+	}
+	return FALSE;
+}
+
+/**
+ * Perform user authentication with a given username and password.
+ *
+ * @warning This returns an error message on failure. Use the identical operator to check
+ * for access: if (true === elgg_authenticate()) { ... }.
+ *
+ *
+ * @see login
+ *
+ * @param string $username The username
+ * @param string $password The password
+ *
+ * @return true|string True or an error message on failure
+ * @access private
+ */
+function elgg_authenticate($username, $password) {
+	$pam = new ElggPAM('user');
+	$credentials = array('username' => $username, 'password' => $password);
+	$result = $pam->authenticate($credentials);
+	if (!$result) {
+		return $pam->getFailureMessage();
+	}
+	return true;
+}
+
+/**
+ * Hook into the PAM system which accepts a username and password and attempts to authenticate
+ * it against a known user.
+ *
+ * @param array $credentials Associated array of credentials passed to
+ *                           Elgg's PAM system. This function expects
+ *                           'username' and 'password' (cleartext).
+ *
+ * @return bool
+ * @throws LoginException
+ * @access private
+ */
+function pam_auth_userpass(array $credentials = array()) {
+
+	if (!isset($credentials['username']) || !isset($credentials['password'])) {
+		return false;
+	}
+
+	$user = get_user_by_username($credentials['username']);
+	if (!$user) {
+		throw new LoginException(elgg_echo('LoginException:UsernameFailure'));
+	}
+
+	if (check_rate_limit_exceeded($user->guid)) {
+		throw new LoginException(elgg_echo('LoginException:AccountLocked'));
+	}
+
+	if ($user->password !== generate_user_password($user, $credentials['password'])) {
+		log_login_failure($user->guid);
+		throw new LoginException(elgg_echo('LoginException:PasswordFailure'));
+	}
+
+	return true;
+}
+
+/**
+ * Log a failed login for $user_guid
+ *
+ * @param int $user_guid User GUID
+ *
+ * @return bool
+ */
+function log_login_failure($user_guid) {
+	$user_guid = (int)$user_guid;
+	$user = get_entity($user_guid);
+
+	if (($user_guid) && ($user) && ($user instanceof ElggUser)) {
+		$fails = (int)$user->getPrivateSetting("login_failures");
+		$fails++;
+
+		$user->setPrivateSetting("login_failures", $fails);
+		$user->setPrivateSetting("login_failure_$fails", time());
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * Resets the fail login count for $user_guid
+ *
+ * @param int $user_guid User GUID
+ *
+ * @return bool true on success (success = user has no logged failed attempts)
+ */
+function reset_login_failure_count($user_guid) {
+	$user_guid = (int)$user_guid;
+	$user = get_entity($user_guid);
+
+	if (($user_guid) && ($user) && ($user instanceof ElggUser)) {
+		$fails = (int)$user->getPrivateSetting("login_failures");
+
+		if ($fails) {
+			for ($n = 1; $n <= $fails; $n++) {
+				$user->removePrivateSetting("login_failure_$n");
 			}
-		}
-		
-		/**
-		 * DB Based session handling code.
-		 */
-		function __elgg_session_open($save_path, $session_name)
-		{
-			global $sess_save_path;
-			$sess_save_path = $save_path;
-			
-			return true;
-		}
-		
-		/**
-		 * DB Based session handling code.
-		 */
-		function __elgg_session_close()
-		{
+
+			$user->removePrivateSetting("login_failures");
+
 			return true;
 		}
-		
-		/**
-		 * DB Based session handling code.
-		 */
-		function __elgg_session_read($id)
-		{
-			global $DB_PREFIX;
-			
-			$id = sanitise_string($id);
-			
-			try {		
-				$result = get_data_row("SELECT * from {$DB_PREFIX}users_sessions where session='$id'");			
-				
-				if ($result)
-					return (string)$result->data;
-					
-			} catch (DatabaseException $e) {
-				
-				// Fall back to file store in this case, since this likely means that the database hasn't been upgraded
-				global $sess_save_path;
-
-				$sess_file = "$sess_save_path/sess_$id";			
-				return (string) @file_get_contents($sess_file);
-			}
-				
-			return '';
-		}
-		
-		/**
-		 * DB Based session handling code.
-		 */
-		function __elgg_session_write($id, $sess_data)
-		{
-			global $DB_PREFIX;
-			
-			$id = sanitise_string($id);			
+
+		// nothing to reset
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * Checks if the rate limit of failed logins has been exceeded for $user_guid.
+ *
+ * @param int $user_guid User GUID
+ *
+ * @return bool on exceeded limit.
+ */
+function check_rate_limit_exceeded($user_guid) {
+	// 5 failures in 5 minutes causes temporary block on logins
+	$limit = 5;
+	$user_guid = (int)$user_guid;
+	$user = get_entity($user_guid);
+
+	if (($user_guid) && ($user) && ($user instanceof ElggUser)) {
+		$fails = (int)$user->getPrivateSetting("login_failures");
+		if ($fails >= $limit) {
+			$cnt = 0;
 			$time = time();
-			
-			try {
-				$sess_data_sanitised = sanitise_string($sess_data);
+			for ($n = $fails; $n > 0; $n--) {
+				$f = $user->getPrivateSetting("login_failure_$n");
+				if ($f > $time - (60 * 5)) {
+					$cnt++;
+				}
 
-				if (insert_data("REPLACE INTO {$DB_PREFIX}users_sessions (session, ts, data) VALUES ('$id', '$time', '$sess_data_sanitised')")!==false)
+				if ($cnt == $limit) {
+					// Limit reached
 					return true;
-					
-			} catch (DatabaseException $e) {
-				// Fall back to file store in this case, since this likely means that the database hasn't been upgraded
-				global $sess_save_path;
-
-  				$sess_file = "$sess_save_path/sess_$id";
-  				if ($fp = @fopen($sess_file, "w")) {
-    				$return = fwrite($fp, $sess_data);
-    				fclose($fp);
-    				return $return;
-  				}
-  				
-  				else
-  					error_log('marcus FAILED TO WRITe ' . print_r($CONFIG, true));
+				}
 			}
-			
-			return false;
 		}
-		
-		/**
-		 * DB Based session handling code.
-		 */
-		function __elgg_session_destroy($id)
-		{
-			global $DB_PREFIX;
-			
-			$id = sanitise_string($id);
-
-			try {		
-				return (bool)delete_data("DELETE from {$DB_PREFIX}users_sessions where session='$id'");
-			} catch (DatabaseException $e) {
-				// Fall back to file store in this case, since this likely means that the database hasn't been upgraded
-				global $sess_save_path;
-
-				$sess_file = "$sess_save_path/sess_$id";
-				return(@unlink($sess_file));
-			}
-			
+	}
+
+	return false;
+}
+
+/**
+ * Logs in a specified ElggUser. For standard registration, use in conjunction
+ * with elgg_authenticate.
+ *
+ * @see elgg_authenticate
+ *
+ * @param ElggUser $user       A valid Elgg user object
+ * @param boolean  $persistent Should this be a persistent login?
+ *
+ * @return true or throws exception
+ * @throws LoginException
+ */
+function login(ElggUser $user, $persistent = false) {
+	// User is banned, return false.
+	if ($user->isBanned()) {
+		throw new LoginException(elgg_echo('LoginException:BannedUser'));
+	}
+
+	$_SESSION['user'] = $user;
+	$_SESSION['guid'] = $user->getGUID();
+	$_SESSION['id'] = $_SESSION['guid'];
+	$_SESSION['username'] = $user->username;
+	$_SESSION['name'] = $user->name;
+
+	// if remember me checked, set cookie with token and store token on user
+	if (($persistent)) {
+		$code = (md5($user->name . $user->username . time() . rand()));
+		$_SESSION['code'] = $code;
+		$user->code = md5($code);
+		setcookie("elggperm", $code, (time() + (86400 * 30)), "/");
+	}
+
+	if (!$user->save() || !elgg_trigger_event('login', 'user', $user)) {
+		unset($_SESSION['username']);
+		unset($_SESSION['name']);
+		unset($_SESSION['code']);
+		unset($_SESSION['guid']);
+		unset($_SESSION['id']);
+		unset($_SESSION['user']);
+		setcookie("elggperm", "", (time() - (86400 * 30)), "/");
+		throw new LoginException(elgg_echo('LoginException:Unknown'));
+	}
+
+	// Users privilege has been elevated, so change the session id (prevents session fixation)
+	session_regenerate_id();
+
+	// Update statistics
+	set_last_login($_SESSION['guid']);
+	reset_login_failure_count($user->guid); // Reset any previous failed login attempts
+
+	// if memcache is enabled, invalidate the user in memcache @see https://github.com/Elgg/Elgg/issues/3143
+	if (is_memcache_available()) {
+		// this needs to happen with a shutdown function because of the timing with set_last_login()
+		register_shutdown_function("_elgg_invalidate_memcache_for_entity", $_SESSION['guid']);
+	}
+	
+	return true;
+}
+
+/**
+ * Log the current user out
+ *
+ * @return bool
+ */
+function logout() {
+	if (isset($_SESSION['user'])) {
+		if (!elgg_trigger_event('logout', 'user', $_SESSION['user'])) {
 			return false;
 		}
-		
-		/**
-		 * DB Based session handling code.
-		 */
-		function __elgg_session_gc($maxlifetime)
-		{
-			global $DB_PREFIX;
-			
-			$life = time()-$maxlifetime;
-
-			try {
-				return (bool)delete_data("DELETE from {$DB_PREFIX}users_sessions where ts<'$life'");
-			} catch (DatabaseException $e) {
-				// Fall back to file store in this case, since this likely means that the database hasn't been upgraded
-				global $sess_save_path;
-
-				foreach (glob("$sess_save_path/sess_*") as $filename) {
-					if (filemtime($filename) < $life) {
-						@unlink($filename);
-					}
-				}
+		$_SESSION['user']->code = "";
+		$_SESSION['user']->save();
+	}
+
+	unset($_SESSION['username']);
+	unset($_SESSION['name']);
+	unset($_SESSION['code']);
+	unset($_SESSION['guid']);
+	unset($_SESSION['id']);
+	unset($_SESSION['user']);
+
+	setcookie("elggperm", "", (time() - (86400 * 30)), "/");
+
+	// pass along any messages
+	$old_msg = $_SESSION['msg'];
+
+	session_destroy();
+
+	// starting a default session to store any post-logout messages.
+	_elgg_session_boot(NULL, NULL, NULL);
+	$_SESSION['msg'] = $old_msg;
+
+	return TRUE;
+}
+
+/**
+ * Initialises the system session and potentially logs the user in
+ *
+ * This function looks for:
+ *
+ * 1. $_SESSION['id'] - if not present, we're logged out, and this is set to 0
+ * 2. The cookie 'elggperm' - if present, checks it for an authentication
+ * token, validates it, and potentially logs the user in
+ *
+ * @uses $_SESSION
+ *
+ * @return bool
+ * @access private
+ */
+function _elgg_session_boot() {
+	global $DB_PREFIX, $CONFIG;
+
+	// Use database for sessions
+	// HACK to allow access to prefix after object destruction
+	$DB_PREFIX = $CONFIG->dbprefix;
+	if ((!isset($CONFIG->use_file_sessions))) {
+		session_set_save_handler("_elgg_session_open",
+			"_elgg_session_close",
+			"_elgg_session_read",
+			"_elgg_session_write",
+			"_elgg_session_destroy",
+			"_elgg_session_gc");
+	}
+
+	session_name('Elgg');
+	session_start();
+
+	// Generate a simple token (private from potentially public session id)
+	if (!isset($_SESSION['__elgg_session'])) {
+		$_SESSION['__elgg_session'] = md5(microtime() . rand());
+	}
+
+	// test whether we have a user session
+	if (empty($_SESSION['guid'])) {
+
+		// clear session variables before checking cookie
+		unset($_SESSION['user']);
+		unset($_SESSION['id']);
+		unset($_SESSION['guid']);
+		unset($_SESSION['code']);
+
+		// is there a remember me cookie
+		if (isset($_COOKIE['elggperm'])) {
+			// we have a cookie, so try to log the user in
+			$code = $_COOKIE['elggperm'];
+			$code = md5($code);
+			if ($user = get_user_by_code($code)) {
+				// we have a user, log him in
+				$_SESSION['user'] = $user;
+				$_SESSION['id'] = $user->getGUID();
+				$_SESSION['guid'] = $_SESSION['id'];
+				$_SESSION['code'] = $_COOKIE['elggperm'];
 			}
-			
+		}
+	} else {
+		// we have a session and we have already checked the fingerprint
+		// reload the user object from database in case it has changed during the session
+		if ($user = get_user($_SESSION['guid'])) {
+			$_SESSION['user'] = $user;
+			$_SESSION['id'] = $user->getGUID();
+			$_SESSION['guid'] = $_SESSION['id'];
+		} else {
+			// user must have been deleted with a session active
+			unset($_SESSION['user']);
+			unset($_SESSION['id']);
+			unset($_SESSION['guid']);
+			unset($_SESSION['code']);
+		}
+	}
+
+	if (isset($_SESSION['guid'])) {
+		set_last_action($_SESSION['guid']);
+	}
+
+	elgg_register_action('login', '', 'public');
+	elgg_register_action('logout');
+
+	// Register a default PAM handler
+	register_pam_handler('pam_auth_userpass');
+
+	// Initialise the magic session
+	global $SESSION;
+	$SESSION = new ElggSession();
+
+	// Finally we ensure that a user who has been banned with an open session is kicked.
+	if ((isset($_SESSION['user'])) && ($_SESSION['user']->isBanned())) {
+		session_destroy();
+		return false;
+	}
+
+	return true;
+}
+
+/**
+ * Used at the top of a page to mark it as logged in users only.
+ *
+ * @return void
+ */
+function gatekeeper() {
+	if (!elgg_is_logged_in()) {
+		$_SESSION['last_forward_from'] = current_page_url();
+		register_error(elgg_echo('loggedinrequired'));
+		forward('', 'login');
+	}
+}
+
+/**
+ * Used at the top of a page to mark it as logged in admin or siteadmin only.
+ *
+ * @return void
+ */
+function admin_gatekeeper() {
+	gatekeeper();
+
+	if (!elgg_is_admin_logged_in()) {
+		$_SESSION['last_forward_from'] = current_page_url();
+		register_error(elgg_echo('adminrequired'));
+		forward('', 'admin');
+	}
+}
+
+/**
+ * Handles opening a session in the DB
+ *
+ * @param string $save_path    The path to save the sessions
+ * @param string $session_name The name of the session
+ *
+ * @return true
+ * @todo Document
+ * @access private
+ */
+function _elgg_session_open($save_path, $session_name) {
+	global $sess_save_path;
+	$sess_save_path = $save_path;
+
+	return true;
+}
+
+/**
+ * Closes a session
+ *
+ * @todo implement
+ * @todo document
+ *
+ * @return true
+ * @access private
+ */
+function _elgg_session_close() {
+	return true;
+}
+
+/**
+ * Read the session data from DB failing back to file.
+ *
+ * @param string $id The session ID
+ *
+ * @return string
+ * @access private
+ */
+function _elgg_session_read($id) {
+	global $DB_PREFIX;
+
+	$id = sanitise_string($id);
+
+	try {
+		$result = get_data_row("SELECT * from {$DB_PREFIX}users_sessions where session='$id'");
+
+		if ($result) {
+			return (string)$result->data;
+		}
+
+	} catch (DatabaseException $e) {
+
+		// Fall back to file store in this case, since this likely means
+		// that the database hasn't been upgraded
+		global $sess_save_path;
+
+		$sess_file = "$sess_save_path/sess_$id";
+		return (string) @file_get_contents($sess_file);
+	}
+
+	return '';
+}
+
+/**
+ * Write session data to the DB falling back to file.
+ *
+ * @param string $id        The session ID
+ * @param mixed  $sess_data Session data
+ *
+ * @return bool
+ * @access private
+ */
+function _elgg_session_write($id, $sess_data) {
+	global $DB_PREFIX;
+
+	$id = sanitise_string($id);
+	$time = time();
+
+	try {
+		$sess_data_sanitised = sanitise_string($sess_data);
+
+		$q = "REPLACE INTO {$DB_PREFIX}users_sessions
+			(session, ts, data) VALUES
+			('$id', '$time', '$sess_data_sanitised')";
+
+		if (insert_data($q) !== false) {
 			return true;
 		}
-		
-		register_elgg_event_handler("boot","system","session_init",1);
-
-
-?>
-\ No newline at end of file
+	} catch (DatabaseException $e) {
+		// Fall back to file store in this case, since this likely means
+		// that the database hasn't been upgraded
+		global $sess_save_path;
+
+		$sess_file = "$sess_save_path/sess_$id";
+		if ($fp = @fopen($sess_file, "w")) {
+			$return = fwrite($fp, $sess_data);
+			fclose($fp);
+			return $return;
+		}
+	}
+
+	return false;
+}
+
+/**
+ * Destroy a DB session, falling back to file.
+ *
+ * @param string $id Session ID
+ *
+ * @return bool
+ * @access private
+ */
+function _elgg_session_destroy($id) {
+	global $DB_PREFIX;
+
+	$id = sanitise_string($id);
+
+	try {
+		return (bool)delete_data("DELETE from {$DB_PREFIX}users_sessions where session='$id'");
+	} catch (DatabaseException $e) {
+		// Fall back to file store in this case, since this likely means that
+		// the database hasn't been upgraded
+		global $sess_save_path;
+
+		$sess_file = "$sess_save_path/sess_$id";
+		return @unlink($sess_file);
+	}
+}
+
+/**
+ * Perform garbage collection on session table / files
+ *
+ * @param int $maxlifetime Max age of a session
+ *
+ * @return bool
+ * @access private
+ */
+function _elgg_session_gc($maxlifetime) {
+	global $DB_PREFIX;
+
+	$life = time() - $maxlifetime;
+
+	try {
+		return (bool)delete_data("DELETE from {$DB_PREFIX}users_sessions where ts<'$life'");
+	} catch (DatabaseException $e) {
+		// Fall back to file store in this case, since this likely means that the database
+		// hasn't been upgraded
+		global $sess_save_path;
+
+		foreach (glob("$sess_save_path/sess_*") as $filename) {
+			if (filemtime($filename) < $life) {
+				@unlink($filename);
+			}
+		}
+	}
+
+	return true;
+}