677 lines
24 KiB
PHP
677 lines
24 KiB
PHP
<?php
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/*
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* PHP Encryption Library
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* Copyright (c) 2014, Taylor Hornby
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Web: https://defuse.ca/secure-php-encryption.htm
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* GitHub: https://github.com/defuse/php-encryption
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*
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* WARNING: This encryption library is not a silver bullet. It only provides
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* symmetric encryption given a uniformly random key. This means you MUST NOT
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* use an ASCII string like a password as the key parameter, it MUST be
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* a uniformly random key generated by CreateNewRandomKey(). If you want to
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* encrypt something with a password, apply a password key derivation function
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* like PBKDF2 or scrypt with a random salt to generate a key.
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*
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* WARNING: Error handling is very important, especially for crypto code!
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*
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* How to use this code:
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*
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* Generating a Key
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* ----------------
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* try {
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* $key = Crypto::CreateNewRandomKey();
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* // WARNING: Do NOT encode $key with bin2hex() or base64_encode(),
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* // they may leak the key to the attacker through side channels.
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* } catch (CryptoTestFailedException $ex) {
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* die('Cannot safely create a key');
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* } catch (CannotPerformOperationException $ex) {
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* die('Cannot safely create a key');
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* }
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*
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* Encrypting a Message
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* --------------------
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* $message = "ATTACK AT DAWN";
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* try {
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* $ciphertext = Crypto::Encrypt($message, $key);
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* } catch (CryptoTestFailedException $ex) {
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* die('Cannot safely perform encryption');
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* } catch (CannotPerformOperationException $ex) {
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* die('Cannot safely perform decryption');
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* }
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*
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* Decrypting a Message
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* --------------------
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* try {
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* $decrypted = Crypto::Decrypt($ciphertext, $key);
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* } catch (InvalidCiphertextException $ex) { // VERY IMPORTANT
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* // Either:
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* // 1. The ciphertext was modified by the attacker,
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* // 2. The key is wrong, or
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* // 3. $ciphertext is not a valid ciphertext or was corrupted.
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* // Assume the worst.
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* die('DANGER! DANGER! The ciphertext has been tampered with!');
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* } catch (CryptoTestFailedException $ex) {
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* die('Cannot safely perform encryption');
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* } catch (CannotPerformOperationException $ex) {
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* die('Cannot safely perform decryption');
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* }
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*/
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/*
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* Raised by Decrypt() when one of the following conditions are met:
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* - The key is wrong.
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* - The ciphertext is invalid or not in the correct format.
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* - The attacker modified the ciphertext.
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*/
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class InvalidCiphertextException extends Exception {}
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/* If you see these, it means it is NOT SAFE to do encryption on your system. */
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class CannotPerformOperationException extends Exception {}
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class CryptoTestFailedException extends Exception {}
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class Crypto
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{
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// Ciphertext format: [____HMAC____][____IV____][____CIPHERTEXT____].
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/* Do not change these constants! */
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const CIPHER = MCRYPT_RIJNDAEL_128;
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const KEY_BYTE_SIZE = 16;
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const CIPHER_MODE = 'cbc';
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const HASH_FUNCTION = 'sha256';
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const MAC_BYTE_SIZE = 32;
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const ENCRYPTION_INFO = 'DefusePHP|KeyForEncryption';
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const AUTHENTICATION_INFO = 'DefusePHP|KeyForAuthentication';
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/*
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* Use this to generate a random encryption key.
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*/
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public static function CreateNewRandomKey()
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{
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Crypto::RuntimeTest();
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return self::SecureRandom(self::KEY_BYTE_SIZE);
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}
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/*
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* Encrypts a message.
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* $plaintext is the message to encrypt.
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* $key is the encryption key, a value generated by CreateNewRandomKey().
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* You MUST catch exceptions thrown by this function. See docs above.
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*/
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public static function Encrypt($plaintext, $key)
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{
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Crypto::RuntimeTest();
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if (self::our_strlen($key) !== self::KEY_BYTE_SIZE)
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{
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throw new CannotPerformOperationException("Bad key.");
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}
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// Generate a sub-key for encryption.
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$keysize = self::KEY_BYTE_SIZE;
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$ekey = self::HKDF(self::HASH_FUNCTION, $key, $keysize, self::ENCRYPTION_INFO);
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// Generate a random initialization vector.
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self::EnsureFunctionExists("mcrypt_get_iv_size");
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$ivsize = mcrypt_get_iv_size(self::CIPHER, self::CIPHER_MODE);
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if ($ivsize === FALSE || $ivsize <= 0) {
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throw new CannotPerformOperationException();
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}
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$iv = self::SecureRandom($ivsize);
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$ciphertext = $iv . self::PlainEncrypt($plaintext, $ekey, $iv);
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// Generate a sub-key for authentication and apply the HMAC.
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$akey = self::HKDF(self::HASH_FUNCTION, $key, self::KEY_BYTE_SIZE, self::AUTHENTICATION_INFO);
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$auth = hash_hmac(self::HASH_FUNCTION, $ciphertext, $akey, true);
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$ciphertext = $auth . $ciphertext;
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return $ciphertext;
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}
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/*
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* Decrypts a ciphertext.
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* $ciphertext is the ciphertext to decrypt.
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* $key is the key that the ciphertext was encrypted with.
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* You MUST catch exceptions thrown by this function. See docs above.
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*/
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public static function Decrypt($ciphertext, $key)
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{
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Crypto::RuntimeTest();
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// Extract the HMAC from the front of the ciphertext.
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if (self::our_strlen($ciphertext) <= self::MAC_BYTE_SIZE) {
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throw new InvalidCiphertextException();
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}
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$hmac = self::our_substr($ciphertext, 0, self::MAC_BYTE_SIZE);
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if ($hmac === FALSE) {
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throw new CannotPerformOperationException();
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}
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$ciphertext = self::our_substr($ciphertext, self::MAC_BYTE_SIZE);
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if ($ciphertext === FALSE) {
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throw new CannotPerformOperationException();
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}
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// Regenerate the same authentication sub-key.
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$akey = self::HKDF(self::HASH_FUNCTION, $key, self::KEY_BYTE_SIZE, self::AUTHENTICATION_INFO);
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if (self::VerifyHMAC($hmac, $ciphertext, $akey))
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{
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// Regenerate the same encryption sub-key.
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$keysize = self::KEY_BYTE_SIZE;
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$ekey = self::HKDF(self::HASH_FUNCTION, $key, $keysize, self::ENCRYPTION_INFO);
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// Extract the initialization vector from the ciphertext.
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self::EnsureFunctionExists("mcrypt_get_iv_size");
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$ivsize = mcrypt_get_iv_size(self::CIPHER, self::CIPHER_MODE);
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if ($ivsize === FALSE || $ivsize <= 0) {
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throw new CannotPerformOperationException();
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}
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if (self::our_strlen($ciphertext) <= $ivsize) {
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throw new InvalidCiphertextException();
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}
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$iv = self::our_substr($ciphertext, 0, $ivsize);
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if ($iv === FALSE) {
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throw new CannotPerformOperationException();
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}
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$ciphertext = self::our_substr($ciphertext, $ivsize);
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if ($ciphertext === FALSE) {
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throw new CannotPerformOperationException();
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}
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$plaintext = self::PlainDecrypt($ciphertext, $ekey, $iv);
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return $plaintext;
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}
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else
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{
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/*
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* We throw an exception instead of returning FALSE because we want
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* a script that doesn't handle this condition to CRASH, instead
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* of thinking the ciphertext decrypted to the value FALSE.
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*/
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throw new InvalidCiphertextException();
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}
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}
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/*
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* Runs tests.
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* Raises CannotPerformOperationException or CryptoTestFailedException if
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* one of the tests fail. If any tests fails, your system is not capable of
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* performing encryption, so make sure you fail safe in that case.
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*/
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public static function RuntimeTest()
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{
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// 0: Tests haven't been run yet.
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// 1: Tests have passed.
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// 2: Tests are running right now.
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// 3: Tests have failed.
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static $test_state = 0;
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if ($test_state === 1 || $test_state === 2) {
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return;
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}
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try {
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$test_state = 2;
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self::AESTestVector();
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self::HMACTestVector();
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self::HKDFTestVector();
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self::TestEncryptDecrypt();
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if (self::our_strlen(Crypto::CreateNewRandomKey()) != self::KEY_BYTE_SIZE) {
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throw new CryptoTestFailedException();
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}
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if (self::ENCRYPTION_INFO == self::AUTHENTICATION_INFO) {
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throw new CryptoTestFailedException();
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}
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} catch (CryptoTestFailedException $ex) {
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// Do this, otherwise it will stay in the "tests are running" state.
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$test_state = 3;
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throw $ex;
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}
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// Change this to '0' make the tests always re-run (for benchmarking).
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$test_state = 1;
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}
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/*
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* Never call this method directly!
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*/
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private static function PlainEncrypt($plaintext, $key, $iv)
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{
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self::EnsureFunctionExists("mcrypt_module_open");
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$crypt = mcrypt_module_open(self::CIPHER, "", self::CIPHER_MODE, "");
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if ($crypt === FALSE) {
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throw new CannotPerformOperationException();
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}
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// Pad the plaintext to a multiple of the block size.
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self::EnsureFunctionExists("mcrypt_enc_get_block_size");
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$block = mcrypt_enc_get_block_size($crypt);
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$pad = $block - (self::our_strlen($plaintext) % $block);
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$plaintext .= str_repeat(chr($pad), $pad);
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self::EnsureFunctionExists("mcrypt_generic_init");
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$ret = mcrypt_generic_init($crypt, $key, $iv);
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if ($ret !== 0) {
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throw new CannotPerformOperationException();
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}
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self::EnsureFunctionExists("mcrypt_generic");
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$ciphertext = mcrypt_generic($crypt, $plaintext);
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self::EnsureFunctionExists("mcrypt_generic_deinit");
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$ret = mcrypt_generic_deinit($crypt);
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if ($ret !== TRUE) {
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throw new CannotPerformOperationException();
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}
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self::EnsureFunctionExists("mcrypt_module_close");
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$ret = mcrypt_module_close($crypt);
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if ($ret !== TRUE) {
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throw new CannotPerformOperationException();
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}
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return $ciphertext;
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}
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/*
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* Never call this method directly!
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*/
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private static function PlainDecrypt($ciphertext, $key, $iv)
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{
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self::EnsureFunctionExists("mcrypt_module_open");
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$crypt = mcrypt_module_open(self::CIPHER, "", self::CIPHER_MODE, "");
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if ($crypt === FALSE) {
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throw new CannotPerformOperationException();
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}
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self::EnsureFunctionExists("mcrypt_enc_get_block_size");
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$block = mcrypt_enc_get_block_size($crypt);
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self::EnsureFunctionExists("mcrypt_generic_init");
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$ret = mcrypt_generic_init($crypt, $key, $iv);
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if ($ret !== 0) {
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throw new CannotPerformOperationException();
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}
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self::EnsureFunctionExists("mdecrypt_generic");
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$plaintext = mdecrypt_generic($crypt, $ciphertext);
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self::EnsureFunctionExists("mcrypt_generic_deinit");
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$ret = mcrypt_generic_deinit($crypt);
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if ($ret !== TRUE) {
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throw new CannotPerformOperationException();
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}
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self::EnsureFunctionExists("mcrypt_module_close");
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$ret = mcrypt_module_close($crypt);
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if ($ret !== TRUE) {
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throw new CannotPerformOperationException();
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}
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// Remove the padding.
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$pad = ord($plaintext[self::our_strlen($plaintext) - 1]);
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if ($pad <= 0 || $pad > $block) {
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throw new CannotPerformOperationException();
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}
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$plaintext = self::our_substr($plaintext, 0, self::our_strlen($plaintext) - $pad);
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if ($plaintext === FALSE) {
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throw new CannotPerformOperationException();
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}
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return $plaintext;
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}
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/*
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* Returns a random binary string of length $octets bytes.
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*/
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private static function SecureRandom($octets)
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{
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self::EnsureFunctionExists("mcrypt_create_iv");
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$random = mcrypt_create_iv($octets, MCRYPT_DEV_URANDOM);
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if ($random === FALSE) {
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throw new CannotPerformOperationException();
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} else {
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return $random;
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}
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}
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/*
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* Use HKDF to derive multiple keys from one.
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* http://tools.ietf.org/html/rfc5869
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*/
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private static function HKDF($hash, $ikm, $length, $info = '', $salt = NULL)
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{
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// Find the correct digest length as quickly as we can.
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$digest_length = self::MAC_BYTE_SIZE;
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if ($hash != self::HASH_FUNCTION) {
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$digest_length = self::our_strlen(hash_hmac($hash, '', '', true));
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}
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// Sanity-check the desired output length.
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if (empty($length) || !is_int($length) ||
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$length < 0 || $length > 255 * $digest_length) {
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throw new CannotPerformOperationException();
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}
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// "if [salt] not provided, is set to a string of HashLen zeroes."
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if (is_null($salt)) {
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$salt = str_repeat("\x00", $digest_length);
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}
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// HKDF-Extract:
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// PRK = HMAC-Hash(salt, IKM)
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// The salt is the HMAC key.
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$prk = hash_hmac($hash, $ikm, $salt, true);
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// HKDF-Expand:
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// This check is useless, but it serves as a reminder to the spec.
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if (self::our_strlen($prk) < $digest_length) {
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throw new CannotPerformOperationException();
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}
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// T(0) = ''
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$t = '';
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$last_block = '';
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for ($block_index = 1; self::our_strlen($t) < $length; $block_index++) {
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// T(i) = HMAC-Hash(PRK, T(i-1) | info | 0x??)
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$last_block = hash_hmac(
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$hash,
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$last_block . $info . chr($block_index),
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$prk,
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true
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);
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// T = T(1) | T(2) | T(3) | ... | T(N)
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$t .= $last_block;
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}
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// ORM = first L octets of T
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$orm = self::our_substr($t, 0, $length);
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if ($orm === FALSE) {
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throw new CannotPerformOperationException();
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}
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return $orm;
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}
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private static function VerifyHMAC($correct_hmac, $message, $key)
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{
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$message_hmac = hash_hmac(self::HASH_FUNCTION, $message, $key, true);
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// We can't just compare the strings with '==', since it would make
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// timing attacks possible. We could use the XOR-OR constant-time
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// comparison algorithm, but I'm not sure if that's good enough way up
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// here in an interpreted language. So we use the method of HMACing the
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// strings we want to compare with a random key, then comparing those.
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// NOTE: This leaks information when the strings are not the same
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// length, but they should always be the same length here. Enforce it:
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if (self::our_strlen($correct_hmac) !== self::our_strlen($message_hmac)) {
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throw new CannotPerformOperationException();
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}
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$blind = self::CreateNewRandomKey();
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$message_compare = hash_hmac(self::HASH_FUNCTION, $message_hmac, $blind);
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$correct_compare = hash_hmac(self::HASH_FUNCTION, $correct_hmac, $blind);
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return $correct_compare === $message_compare;
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}
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private static function TestEncryptDecrypt()
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{
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$key = Crypto::CreateNewRandomKey();
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$data = "EnCrYpT EvErYThInG\x00\x00";
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// Make sure encrypting then decrypting doesn't change the message.
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$ciphertext = Crypto::Encrypt($data, $key);
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try {
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$decrypted = Crypto::Decrypt($ciphertext, $key);
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} catch (InvalidCiphertextException $ex) {
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// It's important to catch this and change it into a
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// CryptoTestFailedException, otherwise a test failure could trick
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// the user into thinking it's just an invalid ciphertext!
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throw new CryptoTestFailedException();
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}
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if($decrypted !== $data)
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{
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throw new CryptoTestFailedException();
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}
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// Modifying the ciphertext: Appending a string.
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try {
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Crypto::Decrypt($ciphertext . "a", $key);
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throw new CryptoTestFailedException();
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} catch (InvalidCiphertextException $e) { /* expected */ }
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// Modifying the ciphertext: Changing an IV byte.
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try {
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$ciphertext[0] = chr((ord($ciphertext[0]) + 1) % 256);
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Crypto::Decrypt($ciphertext, $key);
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throw new CryptoTestFailedException();
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} catch (InvalidCiphertextException $e) { /* expected */ }
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// Decrypting with the wrong key.
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$key = Crypto::CreateNewRandomKey();
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$data = "abcdef";
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$ciphertext = Crypto::Encrypt($data, $key);
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$wrong_key = Crypto::CreateNewRandomKey();
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try {
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Crypto::Decrypt($ciphertext, $wrong_key);
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throw new CryptoTestFailedException();
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} catch (InvalidCiphertextException $e) { /* expected */ }
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// Ciphertext too small (shorter than HMAC).
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$key = Crypto::CreateNewRandomKey();
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$ciphertext = str_repeat("A", self::MAC_BYTE_SIZE - 1);
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try {
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Crypto::Decrypt($ciphertext, $key);
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throw new CryptoTestFailedException();
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} catch (InvalidCiphertextException $e) { /* expected */ }
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}
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private static function HKDFTestVector()
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{
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// HKDF test vectors from RFC 5869
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// Test Case 1
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$ikm = str_repeat("\x0b", 22);
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$salt = self::hexToBytes("000102030405060708090a0b0c");
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$info = self::hexToBytes("f0f1f2f3f4f5f6f7f8f9");
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$length = 42;
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$okm = self::hexToBytes(
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"3cb25f25faacd57a90434f64d0362f2a" .
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"2d2d0a90cf1a5a4c5db02d56ecc4c5bf" .
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"34007208d5b887185865"
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);
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$computed_okm = self::HKDF("sha256", $ikm, $length, $info, $salt);
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if ($computed_okm !== $okm) {
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throw new CryptoTestFailedException();
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}
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// Test Case 7
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$ikm = str_repeat("\x0c", 22);
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$length = 42;
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$okm = self::hexToBytes(
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"2c91117204d745f3500d636a62f64f0a" .
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"b3bae548aa53d423b0d1f27ebba6f5e5" .
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"673a081d70cce7acfc48"
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);
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$computed_okm = self::HKDF("sha1", $ikm, $length);
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if ($computed_okm !== $okm) {
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throw new CryptoTestFailedException();
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}
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}
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private static function HMACTestVector()
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{
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// HMAC test vector From RFC 4231 (Test Case 1)
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$key = str_repeat("\x0b", 20);
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$data = "Hi There";
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$correct = "b0344c61d8db38535ca8afceaf0bf12b881dc200c9833da726e9376c2e32cff7";
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if (hash_hmac(self::HASH_FUNCTION, $data, $key) != $correct) {
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throw new CryptoTestFailedException();
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}
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}
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private static function AESTestVector()
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{
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// AES CBC mode test vector from NIST SP 800-38A
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$key = self::hexToBytes("2b7e151628aed2a6abf7158809cf4f3c");
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$iv = self::hexToBytes("000102030405060708090a0b0c0d0e0f");
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$plaintext = self::hexToBytes(
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"6bc1bee22e409f96e93d7e117393172a" .
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"ae2d8a571e03ac9c9eb76fac45af8e51" .
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"30c81c46a35ce411e5fbc1191a0a52ef" .
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"f69f2445df4f9b17ad2b417be66c3710"
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);
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$ciphertext = self::hexToBytes(
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"7649abac8119b246cee98e9b12e9197d" .
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"5086cb9b507219ee95db113a917678b2" .
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"73bed6b8e3c1743b7116e69e22229516" .
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"3ff1caa1681fac09120eca307586e1a7" .
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/* Block due to padding. Not from NIST test vector.
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Padding Block: 10101010101010101010101010101010
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Ciphertext: 3ff1caa1681fac09120eca307586e1a7
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(+) 2fe1dab1780fbc19021eda206596f1b7
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AES 8cb82807230e1321d3fae00d18cc2012
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*/
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"8cb82807230e1321d3fae00d18cc2012"
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);
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$computed_ciphertext = self::PlainEncrypt($plaintext, $key, $iv);
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if ($computed_ciphertext !== $ciphertext) {
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throw new CryptoTestFailedException();
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}
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$computed_plaintext = self::PlainDecrypt($ciphertext, $key, $iv);
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if ($computed_plaintext !== $plaintext) {
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throw new CryptoTestFailedException();
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}
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}
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/* WARNING: Do not call this function on secrets. It creates side channels. */
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private static function hexToBytes($hex_string)
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{
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return pack("H*", $hex_string);
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}
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private static function EnsureFunctionExists($name)
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{
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if (!function_exists($name)) {
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throw new CannotPerformOperationException();
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}
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}
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/*
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* We need these strlen() and substr() functions because when
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* 'mbstring.func_overload' is set in php.ini, the standard strlen() and
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* substr() are replaced by mb_strlen() and mb_substr().
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*/
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private static function our_strlen($str)
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{
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if (function_exists('mb_strlen')) {
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$length = mb_strlen($str, '8bit');
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if ($length === FALSE) {
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throw new CannotPerformOperationException();
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}
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return $length;
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} else {
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return strlen($str);
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}
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}
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private static function our_substr($str, $start, $length = NULL)
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{
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if (function_exists('mb_substr'))
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{
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// mb_substr($str, 0, NULL, '8bit') returns an empty string on PHP
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// 5.3, so we have to find the length ourselves.
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if (!isset($length)) {
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if ($start >= 0) {
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$length = self::our_strlen($str) - $start;
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} else {
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$length = -$start;
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}
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}
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return mb_substr($str, $start, $length, '8bit');
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}
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// Unlike mb_substr(), substr() doesn't accept NULL for length
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if (isset($length)) {
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return substr($str, $start, $length);
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} else {
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return substr($str, $start);
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}
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}
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}
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/*
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* We want to catch all uncaught exceptions that come from the Crypto class,
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* since by default, PHP will leak the key in the stack trace from an uncaught
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* exception. This is a really ugly hack, but I think it's justified.
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*
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* Everything up to handler() getting called should be reliable, so this should
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* reliably suppress the stack traces. The rest is just a bonus so that we don't
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* make it impossible to debug other exceptions.
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*
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* This bit of code was adapted from: http://stackoverflow.com/a/7939492
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*/
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class CryptoExceptionHandler
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{
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private $rethrow = NULL;
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public function __construct()
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{
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set_exception_handler([$this, "handler"]);
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}
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public function handler($ex)
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{
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if (
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$ex instanceof InvalidCiphertextException ||
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$ex instanceof CannotPerformOperationException ||
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$ex instanceof CryptoTestFailedException
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) {
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echo "FATAL ERROR: Uncaught crypto exception. Suppresssing output.\n";
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} else {
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/* Re-throw the exception in the destructor. */
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$this->rethrow = $ex;
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}
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}
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public function __destruct() {
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if ($this->rethrow) {
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throw $this->rethrow;
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}
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}
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}
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$crypto_exception_handler_object_dont_touch_me = new CryptoExceptionHandler();
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