From d32d45c350ac692db6397648d77b8b0d69ef7923 Mon Sep 17 00:00:00 2001 From: Derek Jones Date: Thu, 17 Jan 2008 19:21:03 +0000 Subject: fixed bug #3003 preventing encryption from working with modes other than MCRYPT_MODE_ECB. Also added some noise to the cipher so the IV can safely be transported along with the encrypted data. --- system/libraries/Encrypt.php | 77 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 75 insertions(+), 2 deletions(-) (limited to 'system/libraries') diff --git a/system/libraries/Encrypt.php b/system/libraries/Encrypt.php index e5ad78c11..5b2b7c017 100644 --- a/system/libraries/Encrypt.php +++ b/system/libraries/Encrypt.php @@ -249,7 +249,7 @@ class CI_Encrypt { { $init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode()); $init_vect = mcrypt_create_iv($init_size, MCRYPT_RAND); - return mcrypt_encrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect); + return $this->_add_cipher_noise($init_vect.mcrypt_encrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), $key); } // -------------------------------------------------------------------- @@ -264,13 +264,86 @@ class CI_Encrypt { */ function mcrypt_decode($data, $key) { + $data = $this->_remove_cipher_noise($data, $key); $init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode()); - $init_vect = mcrypt_create_iv($init_size, MCRYPT_RAND); + $init_vect = substr($data, 0, $init_size); + $data = substr($data, $init_size); return rtrim(mcrypt_decrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), "\0"); } // -------------------------------------------------------------------- + /** + * Adds permuted noise to the IV + encrypted data to protect + * against Man-in-the-middle attacks on CBC mode ciphers + * http://www.ciphersbyritter.com/GLOSSARY.HTM#IV + * + * Function description + * + * @access private + * @param string + * @param string + * @return string + */ + function _add_cipher_noise($data, $key) + { + $keyhash = $this->hash($key); + $keylen = strlen($keyhash); + $str = ''; + + for ($i = 0, $j = 0, $len = strlen($data); $i < $len; ++$i, ++$j) + { + if ($j >= $keylen) + { + $j = 0; + } + + $str .= chr((ord($data[$i]) + ord($keyhash[$j])) % 256); + } + + return $str; + } + + // -------------------------------------------------------------------- + + /** + * Removes permuted noise from the IV + encrypted data, reversing + * _add_cipher_noise() + * + * Function description + * + * @access public + * @param type + * @return type + */ + function _remove_cipher_noise($data, $key) + { + $keyhash = $this->hash($key); + $keylen = strlen($keyhash); + $str = ''; + + for ($i = 0, $j = 0, $len = strlen($data); $i < $len; ++$i, ++$j) + { + if ($j >= $keylen) + { + $j = 0; + } + + $temp = ord($data[$i]) - ord($keyhash[$j]); + + if ($temp < 0) + { + $temp = $temp + 256; + } + + $str .= chr($temp); + } + + return $str; + } + + // -------------------------------------------------------------------- + /** * Set the Mcrypt Cipher * -- cgit v1.2.3-24-g4f1b