Merge pull request #10642 from owncloud/securityutils

Add some security utilities

3 files changed, 236 insertions, 0 deletions

diff --git a/lib/private/security/crypto.php b/lib/private/security/crypto.php
new file mode 100644
index 00000000000..6fdff8d92a2
--- /dev/null
+++ b/lib/private/security/crypto.php
@@ -0,0 +1,115 @@
+<?php
+/**
+ * Copyright (c) 2014 Lukas Reschke <lukas@owncloud.com>
+ * This file is licensed under the Affero General Public License version 3 or
+ * later.
+ * See the COPYING-README file.
+ */
+
+
+namespace OC\Security;
+
+use Crypt_AES;
+use Crypt_Hash;
+use OCP\Security\ICrypto;
+use OCP\Security\ISecureRandom;
+use OCP\Security\StringUtils;
+use OCP\IConfig;
+
+/**
+ * Class Crypto provides a high-level encryption layer using AES-CBC. If no key has been provided
+ * it will use the secret defined in config.php as key. Additionally the message will be HMAC'd.
+ *
+ * Usage:
+ * $encryptWithDefaultPassword = \OC::$server->getCrypto()->encrypt('EncryptedText');
+ * $encryptWithCustompassword = \OC::$server->getCrypto()->encrypt('EncryptedText', 'password');
+ *
+ * @package OC\Security
+ */
+class Crypto implements ICrypto {
+	/** @var Crypt_AES $cipher */
+	private $cipher;
+	/** @var int */
+	private $ivLength = 16;
+	/** @var IConfig */
+	private $config;
+	/** @var ISecureRandom */
+	private $random;
+
+	function __construct(IConfig $config, ISecureRandom $random) {
+		$this->cipher = new Crypt_AES();
+		$this->config = $config;
+		$this->random = $random;
+	}
+
+	/**
+	 * @param string $message The message to authenticate
+	 * @param string $password Password to use (defaults to `secret` in config.php)
+	 * @return string Calculated HMAC
+	 */
+	public function calculateHMAC($message, $password = '') {
+		if($password === '') {
+			$password = $this->config->getSystemValue('secret');
+		}
+
+		// Append an "a" behind the password and hash it to prevent reusing the same password as for encryption
+		$password = hash('sha512', $password . 'a');
+
+		$hash = new Crypt_Hash('sha512');
+		$hash->setKey($password);
+		return $hash->hash($message);
+	}
+
+	/**
+	 * Encrypts a value and adds an HMAC (Encrypt-Then-MAC)
+	 * @param string $plaintext
+	 * @param string $password Password to encrypt, if not specified the secret from config.php will be taken
+	 * @return string Authenticated ciphertext
+	 */
+	public function encrypt($plaintext, $password = '') {
+		if($password === '') {
+			$password = $this->config->getSystemValue('secret');
+		}
+		$this->cipher->setPassword($password);
+
+		$iv = $this->random->getLowStrengthGenerator()->generate($this->ivLength);
+		$this->cipher->setIV($iv);
+
+		$ciphertext = bin2hex($this->cipher->encrypt($plaintext));
+		$hmac = bin2hex($this->calculateHMAC($ciphertext.$iv, $password));
+
+		return $ciphertext.'|'.$iv.'|'.$hmac;
+	}
+
+	/**
+	 * Decrypts a value and verifies the HMAC (Encrypt-Then-Mac)
+	 * @param string $authenticatedCiphertext
+	 * @param string $password Password to encrypt, if not specified the secret from config.php will be taken
+	 * @return string plaintext
+	 * @throws \Exception If the HMAC does not match
+	 */
+	public function decrypt($authenticatedCiphertext, $password = '') {
+		if($password === '') {
+			$password = $this->config->getSystemValue('secret');
+		}
+		$this->cipher->setPassword($password);
+
+		$parts = explode('|', $authenticatedCiphertext);
+		if(sizeof($parts) !== 3) {
+			throw new \Exception('Authenticated ciphertext could not be decoded.');
+		}
+
+		$ciphertext = hex2bin($parts[0]);
+		$iv = $parts[1];
+		$hmac = hex2bin($parts[2]);
+
+		$this->cipher->setIV($iv);
+
+		if(!StringUtils::equals($this->calculateHMAC($parts[0].$parts[1], $password), $hmac)) {
+			throw new \Exception('HMAC does not match.');
+		}
+
+		return $this->cipher->decrypt($ciphertext);
+	}
+
+}
diff --git a/lib/private/security/securerandom.php b/lib/private/security/securerandom.php
new file mode 100644
index 00000000000..2402e863fb0
--- /dev/null
+++ b/lib/private/security/securerandom.php
@@ -0,0 +1,79 @@
+<?php
+/**
+ * Copyright (c) 2014 Lukas Reschke <lukas@owncloud.com>
+ * This file is licensed under the Affero General Public License version 3 or
+ * later.
+ * See the COPYING-README file.
+ */
+
+namespace OC\Security;
+
+use RandomLib;
+use Sabre\DAV\Exception;
+use OCP\Security\ISecureRandom;
+
+/**
+ * Class SecureRandom provides a layer around RandomLib to generate
+ * secure random strings.
+ *
+ * Usage:
+ * \OC::$server->getSecureRandom()->getMediumStrengthGenerator()->generate(10);
+ *
+ * @package OC\Security
+ */
+class SecureRandom implements ISecureRandom {
+
+	/** @var \RandomLib\Factory */
+	var $factory;
+	/** @var \RandomLib\Generator */
+	var $generator;
+
+	function __construct() {
+		$this->factory = new RandomLib\Factory;
+	}
+
+	/**
+	 * Convenience method to get a low strength random number generator.
+	 *
+	 * Low Strength should be used anywhere that random strings are needed
+	 * in a non-cryptographical setting. They are not strong enough to be
+	 * used as keys or salts. They are however useful for one-time use tokens.
+	 *
+	 * @return $this
+	 */
+	public function getLowStrengthGenerator() {
+		$this->generator = $this->factory->getLowStrengthGenerator();
+		return $this;
+	}
+
+	/**
+	 * Convenience method to get a medium strength random number generator.
+	 *
+	 * Medium Strength should be used for most needs of a cryptographic nature.
+	 * They are strong enough to be used as keys and salts. However, they do
+	 * take some time and resources to generate, so they should not be over-used
+	 *
+	 * @return $this
+	 */
+	public function getMediumStrengthGenerator() {
+		$this->generator = $this->factory->getMediumStrengthGenerator();
+		return $this;
+	}
+
+	/**
+	 * Generate a random string of specified length.
+	 * @param string $length The length of the generated string
+	 * @param string $characters An optional list of characters to use if no characterlist is
+	 * 							specified 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ./
+	 * 							is used.
+	 * @return string
+	 * @throws \Exception If the generator is not initialized.
+	 */
+	public function generate($length, $characters = '') {
+		if(is_null($this->generator)) {
+			throw new \Exception('Generator is not initialized.');
+		}
+
+		return $this->generator->generateString($length, $characters);
+	}
+}
diff --git a/lib/private/security/stringutils.php b/lib/private/security/stringutils.php
new file mode 100644
index 00000000000..33a3a708012
--- /dev/null
+++ b/lib/private/security/stringutils.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Copyright (c) 2014 Lukas Reschke <lukas@owncloud.com>
+ * This file is licensed under the Affero General Public License version 3 or
+ * later.
+ * See the COPYING-README file.
+ */
+
+namespace OC\Security;
+
+class StringUtils {
+
+	/**
+	 * Compares whether two strings are equal. To prevent guessing of the string
+	 * length this is done by comparing two hashes against each other and afterwards
+	 * a comparison of the real string to prevent against the unlikely chance of
+	 * collisions.
+	 *
+	 * Be aware that this function may leak whether the string to compare have a different
+	 * length.
+	 *
+	 * @param string $expected The expected value
+	 * @param string $input The input to compare against
+	 * @return bool True if the two strings are equal, otherwise false.
+	 */
+	public static function equals($expected, $input) {
+
+		if(function_exists('hash_equals')) {
+			return hash_equals($expected, $input);
+		}
+
+		$randomString = \OC::$server->getSecureRandom()->getLowStrengthGenerator()->generate(10);
+
+		if(hash('sha512', $expected.$randomString) === hash('sha512', $input.$randomString)) {
+			if($expected === $input) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+}
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