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POSecure cookies in PHP sessions
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copied!<p>I have developed a PHP session class and tested it using a few examples (see source code below). It appears to be okay. Now I would like to make this session somehow "secure". I found some sample code which is meant to encrypt a cookie (in Courioso's book Expert PHP and MySQL). Here is this code snippet.</p> <p>Code for encrypted cookie</p> <pre><code>$cookieData = serialize($user); $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC); srand(); $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND); $encryptedData = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $secret, $cookieData, MCRYPT_MODE_CBC, $iv); setcookie('user', base64_encode).':'.$iv); </code></pre> <p>and a similar code for decrypting the cookie</p> <p>My first question is: can I trust this code. I.e. is it really secure? (I tried some other code samples of that book and found them rather buggy).</p> <p>I do not fully understand how the code for encrypting a cookie could be embedded into my session class (either the code above - or any other cookie encryption code). Should I replace the cookie which is automatically generated by PHP (PHPSESSID) or should generate a new cookie and encrypt this custom cookie? (My guess is the second is true, but I would like to be sure).</p> <p>How is the protection via encrypted cookies meant to work? I imagine the following attack: (1) if the attacker get somehow the cookie in his hand he just replies with the same cookie. Okay. he does not have the password but he has the encrypted password. Later I check only if the encrypted password is okay. So if the attacker has the cookie: game over - no matter if the cookie contains the password or "only" the encrypted password. Correct? (2) Okay this problem can be solved using a cyphered transmission like SSL. But then I think if I use SLL than the transmission is anyway cyphered. I don't need to cypher the password a second time using the encryption function. Correct?</p> <p>Here is the code for the session class I have already.</p> <p>Thanks</p> <pre><code><?php class SessionClass { private static $_instance; public static function getInstance() { if (!(self::$_instance instanceof self)) { self::$_instance = new self(); } return self::$_instance; } // getInstance public function __construct() { session_set_save_handler( array($this, "open"), array($this, "close"), array($this, "read"), array($this, "write"), array($this, "destroy"), array($this, "gc") ); $createTable = "CREATE TABLE IF NOT EXISTS `session`( ". "`sessionID` VARCHAR(128), ". "`data` MEDIUMBLOB, ". "`timestamp` INT, ". "`ip` VARCHAR(15), ". "PRIMARY KEY (`sessionID` ), ". "KEY (`timestamp`, `sessionID`))"; mysql_query($createTable); } // construct public function __destruct() { session_write_close(); } public function open ($path, $id) { // do nothing return (true); } public function close() { // do nothing return (true); } public function read($id) { $escapedID = mysql_escape_string($id); $query = sprintf("SELECT * FROM session WHERE sessionID = '%s'", $escapedID); $res = mysql_query($query); if ((!$res) || (!mysql_num_rows($res))) { $timestamp = time(); $query = sprintf("INSERT INTO session (sessionID, timestamp) VALUES ('%s', %s)", $escapedID, $timestamp); mysql_query($query); return ''; } elseif (($row = mysql_fetch_assoc($res))) { $query = "UPDATE session SET timestamp = "; $query .= time(); $query .= sprintf (" WHERE sessionID = '%s'", $escapedID); mysql_query($query); return $row['data']; } // elseif return ""; } // read public function write($id, $data) { $query = "REPLACE INTO session (sessionID, data, ip, timestamp) "; $query .= sprintf("VALUES ('%s', '%s', '%s', %s)", mysql_escape_string($id), mysql_escape_string($data), $_SERVER['REMOTE_ADDR'], time()); mysql_query($query); return (true); } // write public function destroy($id) { $escapedID = mysql_escape_string($id); $query = sprintf("DELETE FROM session WHERE sessionID = %s", $escapedID); $res = mysql_query($query); return (mysql_affected_rows($res) == 1); } // destroy public function gc($lifetime) { $query = "DELETE FROM session WHERE "; $query = sprintf("%s - timestamp > %s", time(), $lifetime); mysql_query($query); return (true); } // gc } // SessionClass </code></pre>

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