* @author Chris Steipp
* @file
*/
+
use MediaWiki\MediaWikiServices;
class MWCryptHKDF {
- /**
- * Singleton instance for public use
- */
- protected static $singleton = null;
-
- /**
- * The persistant cache
- */
- protected $cache = null;
-
- /**
- * Cache key we'll use for our salt
- */
- protected $cacheKey = null;
-
- /**
- * The hash algorithm being used
- */
- protected $algorithm = null;
-
- /**
- * binary string, the salt for the HKDF
- */
- protected $salt;
-
- /**
- * The pseudorandom key
- */
- private $prk;
-
- /**
- * The secret key material. This must be kept secret to preserve
- * the security properties of this RNG.
- */
- private $skm;
-
- /**
- * The last block (K(i)) of the most recent expanded key
- */
- protected $lastK;
-
- /**
- * a "context information" string CTXinfo (which may be null)
- * See http://eprint.iacr.org/2010/264.pdf Section 4.1
- */
- protected $context = [];
-
- /**
- * Round count is computed based on the hash'es output length,
- * which neither php nor openssl seem to provide easily.
- */
- public static $hashLength = [
- 'md5' => 16,
- 'sha1' => 20,
- 'sha224' => 28,
- 'sha256' => 32,
- 'sha384' => 48,
- 'sha512' => 64,
- 'ripemd128' => 16,
- 'ripemd160' => 20,
- 'ripemd256' => 32,
- 'ripemd320' => 40,
- 'whirlpool' => 64,
- ];
-
- /**
- * @param string $secretKeyMaterial
- * @param string $algorithm Name of hashing algorithm
- * @param BagOStuff $cache
- * @param string|array $context Context to mix into HKDF context
- * @throws MWException
- */
- public function __construct( $secretKeyMaterial, $algorithm, $cache, $context ) {
- if ( strlen( $secretKeyMaterial ) < 16 ) {
- throw new MWException( "MWCryptHKDF secret was too short." );
- }
- $this->skm = $secretKeyMaterial;
- $this->algorithm = $algorithm;
- $this->cache = $cache;
- $this->salt = ''; // Initialize a blank salt, see getSaltUsingCache()
- $this->prk = '';
- $this->context = is_array( $context ) ? $context : [ $context ];
-
- // To prevent every call from hitting the same memcache server, pick
- // from a set of keys to use. mt_rand is only use to pick a random
- // server, and does not affect the security of the process.
- $this->cacheKey = wfMemcKey( 'HKDF', mt_rand( 0, 16 ) );
- }
-
- /**
- * Save the last block generated, so the next user will compute a different PRK
- * from the same SKM. This should keep things unpredictable even if an attacker
- * is able to influence CTXinfo.
- */
- function __destruct() {
- if ( $this->lastK ) {
- $this->cache->set( $this->cacheKey, $this->lastK );
- }
- }
-
- /**
- * MW specific salt, cached from last run
- * @return string Binary string
- */
- protected function getSaltUsingCache() {
- if ( $this->salt == '' ) {
- $lastSalt = $this->cache->get( $this->cacheKey );
- if ( $lastSalt === false ) {
- // If we don't have a previous value to use as our salt, we use
- // 16 bytes from MWCryptRand, which will use a small amount of
- // entropy from our pool. Note, "XTR may be deterministic or keyed
- // via an optional “salt value” (i.e., a non-secret random
- // value)..." - http://eprint.iacr.org/2010/264.pdf. However, we
- // use a strongly random value since we can.
- $lastSalt = MWCryptRand::generate( 16 );
- }
- // Get a binary string that is hashLen long
- $this->salt = hash( $this->algorithm, $lastSalt, true );
- }
- return $this->salt;
- }
-
/**
* Return a singleton instance, based on the global configs.
- * @return self
- * @throws MWException
+ * @return CryptHKDF
*/
protected static function singleton() {
- global $wgHKDFAlgorithm, $wgHKDFSecret, $wgSecretKey;
-
- $secret = $wgHKDFSecret ?: $wgSecretKey;
- if ( !$secret ) {
- throw new MWException( "Cannot use MWCryptHKDF without a secret." );
- }
-
- // In HKDF, the context can be known to the attacker, but this will
- // keep simultaneous runs from producing the same output.
- $context = [];
- $context[] = microtime();
- $context[] = getmypid();
- $context[] = gethostname();
-
- // Setup salt cache
- $cache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
- if ( $cache instanceof EmptyBagOStuff ) {
- // Use APC, or fallback to the main cache if it isn't setup
- $cache = ObjectCache::getLocalClusterInstance();
- }
-
- if ( is_null( self::$singleton ) ) {
- self::$singleton = new self( $secret, $wgHKDFAlgorithm, $cache, $context );
- }
-
- return self::$singleton;
- }
-
- /**
- * Produce $bytes of secure random data. As a side-effect,
- * $this->lastK is set to the last hashLen block of key material.
- * @param int $bytes Number of bytes of data
- * @param string $context Context to mix into CTXinfo
- * @return string Binary string of length $bytes
- */
- protected function realGenerate( $bytes, $context = '' ) {
-
- if ( $this->prk === '' ) {
- $salt = $this->getSaltUsingCache();
- $this->prk = self::HKDFExtract(
- $this->algorithm,
- $salt,
- $this->skm
- );
- }
-
- $CTXinfo = implode( ':', array_merge( $this->context, [ $context ] ) );
-
- return self::HKDFExpand(
- $this->algorithm,
- $this->prk,
- $CTXinfo,
- $bytes,
- $this->lastK
- );
+ return MediaWikiServices::getInstance()->getCryptHKDF();
}
/**
* From http://eprint.iacr.org/2010/264.pdf:
*
* The scheme HKDF is specifed as:
- * HKDF(XTS, SKM, CTXinfo, L) = K(1) || K(2) || ... || K(t)
+ * HKDF(XTS, SKM, CTXinfo, L) = K(1) || K(2) || ... || K(t)
* where the values K(i) are defined as follows:
- * PRK = HMAC(XTS, SKM)
- * K(1) = HMAC(PRK, CTXinfo || 0);
- * K(i+1) = HMAC(PRK, K(i) || CTXinfo || i), 1 <= i < t;
+ * PRK = HMAC(XTS, SKM)
+ * K(1) = HMAC(PRK, CTXinfo || 0);
+ * K(i+1) = HMAC(PRK, K(i) || CTXinfo || i), 1 <= i < t;
* where t = [L/k] and the value K(t) is truncated to its first d = L mod k bits;
* the counter i is non-wrapping and of a given fixed size, e.g., a single byte.
* Note that the length of the HMAC output is the same as its key length and therefore
* @return string Cryptographically secure pseudorandom binary string
*/
public static function HKDF( $hash, $ikm, $salt, $info, $L ) {
- $prk = self::HKDFExtract( $hash, $salt, $ikm );
- $okm = self::HKDFExpand( $hash, $prk, $info, $L );
- return $okm;
- }
-
- /**
- * Extract the PRK, PRK = HMAC(XTS, SKM)
- * Note that the hmac is keyed with XTS (the salt),
- * and the SKM (source key material) is the "data".
- *
- * @param string $hash The hashing function to use (e.g., sha256)
- * @param string $salt The salt to add to the ikm, to get the prk
- * @param string $ikm The input keying material
- * @return string Binary string (pseudorandm key) used as input to HKDFExpand
- */
- private static function HKDFExtract( $hash, $salt, $ikm ) {
- return hash_hmac( $hash, $ikm, $salt, true );
- }
-
- /**
- * Expand the key with the given context
- *
- * @param string $hash Hashing Algorithm
- * @param string $prk A pseudorandom key of at least HashLen octets
- * (usually, the output from the extract step)
- * @param string $info Optional context and application specific information
- * (can be a zero-length string)
- * @param int $bytes Length of output keying material in bytes
- * (<= 255*HashLen)
- * @param string &$lastK Set by this function to the last block of the expansion.
- * In MediaWiki, this is used to seed future Extractions.
- * @return string Cryptographically secure random string $bytes long
- * @throws MWException
- */
- private static function HKDFExpand( $hash, $prk, $info, $bytes, &$lastK = '' ) {
- $hashLen = MWCryptHKDF::$hashLength[$hash];
- $rounds = ceil( $bytes / $hashLen );
- $output = '';
-
- if ( $bytes > 255 * $hashLen ) {
- throw new MWException( "Too many bytes requested from HDKFExpand" );
- }
-
- // K(1) = HMAC(PRK, CTXinfo || 1);
- // K(i) = HMAC(PRK, K(i-1) || CTXinfo || i); 1 < i <= t;
- for ( $counter = 1; $counter <= $rounds; ++$counter ) {
- $lastK = hash_hmac(
- $hash,
- $lastK . $info . chr( $counter ),
- $prk,
- true
- );
- $output .= $lastK;
- }
-
- return substr( $output, 0, $bytes );
+ return CryptHKDF::HKDF( $hash, $ikm, $salt, $info, $L );
}
/**
* @return string Binary string of length $bytes
*/
public static function generate( $bytes, $context ) {
- return self::singleton()->realGenerate( $bytes, $context );
+ return self::singleton()->generate( $bytes, $context );
}
/**
*/
public static function generateHex( $chars, $context = '' ) {
$bytes = ceil( $chars / 2 );
- $hex = bin2hex( self::singleton()->realGenerate( $bytes, $context ) );
+ $hex = bin2hex( self::singleton()->generate( $bytes, $context ) );
return substr( $hex, 0, $chars );
}
dépôts / lhc / web / wiklou.git / blobdiff