Allow regenerating site secret

4 files changed, 174 insertions, 2 deletions

diff --git a/engine/classes/ElggCrypto.php b/engine/classes/ElggCrypto.php
new file mode 100644
index 000000000..364af4542
--- /dev/null
+++ b/engine/classes/ElggCrypto.php
@@ -0,0 +1,134 @@
+<?php
+/**
+ * ElggCrypto
+ *
+ * @package    Elgg.Core
+ * @subpackage Crypto
+ *
+ * @access private
+ */
+class ElggCrypto {
+
+	/**
+	 * Character set for temp passwords (no risk of embedded profanity/glyphs that look similar)
+	 */
+	const CHARS_PASSWORD = 'bcdfghjklmnpqrstvwxyz2346789';
+
+	/**
+	 * Returns a string of highly randomized bytes (over the full 8-bit range).
+	 *
+	 * This function is better than simply calling mt_rand() or any other built-in
+	 * PHP function because it can return a long string of bytes (compared to < 4
+	 * bytes normally from mt_rand()) and uses the best available pseudo-random
+	 * source.
+	 *
+	 * @param int $count The number of characters (bytes) to return in the string.
+	 * @return string
+	 *
+	 * @copyright Copyright 2001 - 2012 by the original authors
+	 *            https://github.com/drupal/drupal/blob/7.x/COPYRIGHT.txt
+	 * @license   https://github.com/drupal/drupal/blob/7.x/LICENSE.txt GPL 2
+	 *
+	 * @see https://github.com/drupal/drupal/blob/7.x/includes/bootstrap.inc#L1942
+	 */
+	public static function getRandomBytes($count)  {
+		// $random_state does not use drupal_static as it stores random bytes.
+		static $random_state, $bytes, $php_compatible;
+		// Initialize on the first call. The contents of $_SERVER includes a mix of
+		// user-specific and system information that varies a little with each page.
+		if (!isset($random_state)) {
+			$random_state = print_r($_SERVER, true);
+			if (function_exists('getmypid')) {
+				// Further initialize with the somewhat random PHP process ID.
+				$random_state .= getmypid();
+			}
+			$bytes = '';
+		}
+		if (strlen($bytes) < $count) {
+			// PHP versions prior 5.3.4 experienced openssl_random_pseudo_bytes()
+			// locking on Windows and rendered it unusable.
+			if (!isset($php_compatible)) {
+				$php_compatible = version_compare(PHP_VERSION, '5.3.4', '>=');
+			}
+			// /dev/urandom is available on many *nix systems and is considered the
+			// best commonly available pseudo-random source.
+			if ($fh = @fopen('/dev/urandom', 'rb')) {
+				// PHP only performs buffered reads, so in reality it will always read
+				// at least 4096 bytes. Thus, it costs nothing extra to read and store
+				// that much so as to speed any additional invocations.
+				$bytes .= fread($fh, max(4096, $count));
+				fclose($fh);
+			} elseif ($php_compatible && function_exists('openssl_random_pseudo_bytes')) {
+				// openssl_random_pseudo_bytes() will find entropy in a system-dependent
+				// way.
+				$bytes .= openssl_random_pseudo_bytes($count - strlen($bytes));
+			}
+			// If /dev/urandom is not available or returns no bytes, this loop will
+			// generate a good set of pseudo-random bytes on any system.
+			// Note that it may be important that our $random_state is passed
+			// through hash() prior to being rolled into $output, that the two hash()
+			// invocations are different, and that the extra input into the first one -
+			// the microtime() - is prepended rather than appended. This is to avoid
+			// directly leaking $random_state via the $output stream, which could
+			// allow for trivial prediction of further "random" numbers.
+			while (strlen($bytes) < $count) {
+				$random_state = hash('sha256', microtime() . mt_rand() . $random_state);
+				$bytes .= hash('sha256', mt_rand() . $random_state, true);
+			}
+		}
+		$output = substr($bytes, 0, $count);
+		$bytes = substr($bytes, $count);
+		return $output;
+	}
+
+	/**
+	 * Generate a random string of specified length.
+	 *
+	 * Uses supplied character list for generating the new string.
+	 * If no character list provided - uses Base64 URL character set.
+	 *
+	 * @param  int         $length Desired length of the string
+	 * @param  string|null $chars  Characters to be chosen from randomly. If not given, the Base64 URL
+	 *                             charset will be used.
+	 *
+	 * @return string The random string
+	 *
+	 * @throws InvalidArgumentException
+	 *
+	 * @copyright Copyright (c) 2005-2013 Zend Technologies USA Inc. (http://www.zend.com)
+	 * @license   http://framework.zend.com/license/new-bsd New BSD License
+	 *
+	 * @see https://github.com/zendframework/zf2/blob/master/library/Zend/Math/Rand.php#L179
+	 */
+	public static function getRandomString($length, $chars = null)
+	{
+		if ($length < 1) {
+			throw new InvalidArgumentException('Length should be >= 1');
+		}
+
+		if (empty($chars)) {
+			$numBytes = ceil($length * 0.75);
+			$bytes    = self::getRandomBytes($numBytes);
+			$string = substr(rtrim(base64_encode($bytes), '='), 0, $length);
+
+			// Base64 URL
+			return strtr($string, '+/', '-_');
+		}
+
+		$listLen = strlen($chars);
+
+		if ($listLen == 1) {
+			return str_repeat($chars, $length);
+		}
+
+		$bytes  = self::getRandomBytes($length);
+		$pos    = 0;
+		$result = '';
+		for ($i = 0; $i < $length; $i++) {
+			$pos     = ($pos + ord($bytes[$i])) % $listLen;
+			$result .= $chars[$pos];
+		}
+
+		return $result;
+	}
+}
diff --git a/engine/lib/actions.php b/engine/lib/actions.php
index 56936f582..8047914ac 100644
--- a/engine/lib/actions.php
+++ b/engine/lib/actions.php
@@ -364,16 +364,19 @@ function generate_action_token($timestamp) {
 }
 
 /**
- * Initialise the site secret hash.
+ * Initialise the site secret (32 bytes: "z" to indicate format + 186-bit key in Base64 URL).
  *
  * Used during installation and saves as a datalist.
  *
+ * Note: Old secrets were hex encoded.
+ *
  * @return mixed The site secret hash or false
  * @access private
  * @todo Move to better file.
  */
 function init_site_secret() {
-	$secret = md5(rand() . microtime());
+	$secret = 'z' . ElggCrypto::getRandomString(31);
+
 	if (datalist_set('__site_secret__', $secret)) {
 		return $secret;
 	}
@@ -400,6 +403,26 @@ function get_site_secret() {
 }
 
 /**
+ * Get the strength of the site secret
+ *
+ * @return string "strong", "moderate", or "weak"
+ * @access private
+ */
+function _elgg_get_site_secret_strength() {
+	$secret = get_site_secret();
+	if ($secret[0] !== 'z') {
+		$rand_max = getrandmax();
+		if ($rand_max < pow(2, 16)) {
+			return 'weak';
+		}
+		if ($rand_max < pow(2, 32)) {
+			return 'moderate';
+		}
+	}
+	return 'strong';
+}
+
+/**
  * Check if an action is registered and its script exists.
  *
  * @param string $action Action name
diff --git a/engine/lib/admin.php b/engine/lib/admin.php
index 7f82108c0..f36f29668 100644
--- a/engine/lib/admin.php
+++ b/engine/lib/admin.php
@@ -236,6 +236,7 @@ function admin_init() {
 	elgg_register_action('admin/site/update_advanced', '', 'admin');
 	elgg_register_action('admin/site/flush_cache', '', 'admin');
 	elgg_register_action('admin/site/unlock_upgrade', '', 'admin');
+	elgg_register_action('admin/site/regenerate_secret', '', 'admin');
 
 	elgg_register_action('admin/menu/save', '', 'admin');
 
@@ -291,6 +292,7 @@ function admin_init() {
 	elgg_register_admin_menu_item('configure', 'settings', null, 100);
 	elgg_register_admin_menu_item('configure', 'basic', 'settings', 10);
 	elgg_register_admin_menu_item('configure', 'advanced', 'settings', 20);
+	elgg_register_admin_menu_item('configure', 'advanced/site_secret', 'settings', 25);
 	elgg_register_admin_menu_item('configure', 'menu_items', 'appearance', 30);
 	elgg_register_admin_menu_item('configure', 'profile_fields', 'appearance', 40);
 	// default widgets is added via an event handler elgg_default_widgets_init() in widgets.php
diff --git a/engine/lib/upgrades/2013060900-1.8.15-site_secret-404fc165cf9e0ac9.php b/engine/lib/upgrades/2013060900-1.8.15-site_secret-404fc165cf9e0ac9.php
new file mode 100644
index 000000000..b5b614762
--- /dev/null
+++ b/engine/lib/upgrades/2013060900-1.8.15-site_secret-404fc165cf9e0ac9.php
@@ -0,0 +1,13 @@
+<?php
+/**
+ * Elgg 1.8.15 upgrade 2013060900
+ * site_secret
+ *
+ * Description
+ */
+
+$strength = _elgg_get_site_secret_strength();
+
+if ($strength !== 'strong') {
+	elgg_add_admin_notice('weak_site_key', elgg_echo("upgrade:site_secret_warning:$strength"));
+}