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<?php |
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namespace Elgg\Database; |
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/** |
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* Manages a site-specific secret key, encoded as a 32 byte string "secret" |
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* |
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* The key can have two formats: |
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* - Since 1.8.17 all keys generated are Base64URL-encoded with the 1st character set to "z" so that |
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* the format can be recognized. With one character lost, this makes the keys effectively 186 bits. |
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* - Before 1.8.17 keys were hex-encoded (128 bits) but created from insufficiently random sources. |
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* |
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* The hex keys were created with rand() as the only decent source of entropy (the site's creation time |
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* is not too difficult to find). As such, systems with a low getrandmax() value created particularly |
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* weak keys. You can check key string using getStrength(). |
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* |
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* @access private |
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* |
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* @package Elgg.Core |
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* @subpackage Database |
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* @since 1.10.0 |
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*/ |
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class SiteSecret { |
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/** |
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* Initialise the site secret (32 bytes: "z" to indicate format + 186-bit key in Base64 URL). |
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* |
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* Used during installation and saves as a datalist. |
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* |
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* Note: Old secrets were hex encoded. |
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* |
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* @return mixed The site secret hash or false |
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* @access private |
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*/ |
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function init() { |
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$secret = 'z' . _elgg_services()->crypto->getRandomString(31); |
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if (_elgg_services()->datalist->set('__site_secret__', $secret)) { |
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return $secret; |
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} |
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return false; |
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} |
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/** |
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* Returns the site secret. |
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* |
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* Used to generate difficult to guess hashes for sessions and action tokens. |
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* |
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* @param bool $raw If true, a binary key will be returned |
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* |
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* @return string Site secret. |
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* @access private |
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*/ |
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function get($raw = false) { |
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$secret = _elgg_services()->datalist->get('__site_secret__'); |
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if (!$secret) { |
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$secret = init_site_secret(); |
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} |
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if ($raw) { |
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// try to return binary key |
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if ($secret[0] === 'z') { |
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// new keys are "z" + base64URL |
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$base64 = strtr(substr($secret, 1), '-_', '+/'); |
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$key = base64_decode($base64); |
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if ($key !== false) { |
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// on failure, at least return string key :/ |
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return $key; |
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} |
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} else { |
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// old keys are hex |
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return hex2bin($secret); |
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} |
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} |
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return $secret; |
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} |
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/** |
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* Get the strength of the site secret |
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* |
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* If "weak" or "moderate" is returned, this assumes we're running on the same system that created |
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* the key. |
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* |
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* @return string "strong", "moderate", or "weak" |
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* @access private |
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*/ |
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function getStrength() { |
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$secret = get_site_secret(); |
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if ($secret[0] !== 'z') { |
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$rand_max = getrandmax(); |
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if ($rand_max < pow(2, 16)) { |
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return 'weak'; |
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} |
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if ($rand_max < pow(2, 32)) { |
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return 'moderate'; |
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} |
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} |
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return 'strong'; |
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} |
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} |
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