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0, 'Trying to increment a nonce by a nonpositive amount' ); Core::ensureTrue( $inc <= PHP_INT_MAX - 255, 'Integer overflow may occur' ); /* * We start at the rightmost byte (big-endian) * So, too, does OpenSSL: http://stackoverflow.com/a/3146214/2224584 */ for ($i = Core::BLOCK_BYTE_SIZE - 1; $i >= 0; --$i) { $sum = \ord($ctr[$i]) + $inc; /* Detect integer overflow and fail. */ Core::ensureTrue(\is_int($sum), 'Integer overflow in CTR mode nonce increment'); $ctr[$i] = \pack('C', $sum & 0xFF); $inc = $sum >> 8; } return $ctr; } /** * Returns a random byte string of the specified length. * * @param int $octets * * @throws Ex\EnvironmentIsBrokenException * * @return string */ public static function secureRandom($octets) { self::ensureFunctionExists('random_bytes'); try { return \random_bytes($octets); } catch (\Exception $ex) { throw new Ex\EnvironmentIsBrokenException( 'Your system does not have a secure random number generator.' ); } } /** * Computes the HKDF key derivation function specified in * http://tools.ietf.org/html/rfc5869. * * @param string $hash Hash Function * @param string $ikm Initial Keying Material * @param int $length How many bytes? * @param string $info What sort of key are we deriving? * @param string $salt * * @throws Ex\EnvironmentIsBrokenException * @psalm-suppress UndefinedFunction - We're checking if the function exists first. * * @return string */ public static function HKDF($hash, $ikm, $length, $info = '', $salt = null) { static $nativeHKDF = null; if ($nativeHKDF === null) { $nativeHKDF = \is_callable('\\hash_hkdf'); } if ($nativeHKDF) { if (\is_null($salt)) { $salt = ''; } return \hash_hkdf($hash, $ikm, $length, $info, $salt); } $digest_length = Core::ourStrlen(\hash_hmac($hash, '', '', true)); // Sanity-check the desired output length. Core::ensureTrue( !empty($length) && \is_int($length) && $length >= 0 && $length <= 255 * $digest_length, 'Bad output length requested of HDKF.' ); // "if [salt] not provided, is set to a string of HashLen zeroes." if (\is_null($salt)) { $salt = \str_repeat("\x00", $digest_length); } // HKDF-Extract: // PRK = HMAC-Hash(salt, IKM) // The salt is the HMAC key. $prk = \hash_hmac($hash, $ikm, $salt, true); // HKDF-Expand: // This check is useless, but it serves as a reminder to the spec. Core::ensureTrue(Core::ourStrlen($prk) >= $digest_length); // T(0) = '' $t = ''; $last_block = ''; for ($block_index = 1; Core::ourStrlen($t) < $length; ++$block_index) { // T(i) = HMAC-Hash(PRK, T(i-1) | info | 0x??) $last_block = \hash_hmac( $hash, $last_block . $info . \chr($block_index), $prk, true ); // T = T(1) | T(2) | T(3) | ... | T(N) $t .= $last_block; } // ORM = first L octets of T /** @var string $orm */ $orm = Core::ourSubstr($t, 0, $length); Core::ensureTrue(\is_string($orm)); return $orm; } /** * Checks if two equal-length strings are the same without leaking * information through side channels. * * @param string $expected * @param string $given * * @throws Ex\EnvironmentIsBrokenException * * @return bool */ public static function hashEquals($expected, $given) { static $native = null; if ($native === null) { $native = \function_exists('hash_equals'); } if ($native) { return \hash_equals($expected, $given); } // We can't just compare the strings with '==', since it would make // timing attacks possible. We could use the XOR-OR constant-time // comparison algorithm, but that may not be a reliable defense in an // interpreted language. So we use the approach of HMACing both strings // with a random key and comparing the HMACs. // We're not attempting to make variable-length string comparison // secure, as that's very difficult. Make sure the strings are the same // length. Core::ensureTrue(Core::ourStrlen($expected) === Core::ourStrlen($given)); $blind = Core::secureRandom(32); $message_compare = \hash_hmac(Core::HASH_FUNCTION_NAME, $given, $blind); $correct_compare = \hash_hmac(Core::HASH_FUNCTION_NAME, $expected, $blind); return $correct_compare === $message_compare; } /** * Throws an exception if the constant doesn't exist. * * @param string $name * @return void * * @throws Ex\EnvironmentIsBrokenException */ public static function ensureConstantExists($name) { Core::ensureTrue( \defined($name), 'Constant '.$name.' does not exists' ); } /** * Throws an exception if the function doesn't exist. * * @param string $name * @return void * * @throws Ex\EnvironmentIsBrokenException */ public static function ensureFunctionExists($name) { Core::ensureTrue( \function_exists($name), 'function '.$name.' does not exists' ); } /** * Throws an exception if the condition is false. * * @param bool $condition * @param string $message * @return void * * @throws Ex\EnvironmentIsBrokenException */ public static function ensureTrue($condition, $message = '') { if (!$condition) { throw new Ex\EnvironmentIsBrokenException($message); } } /* * We need these strlen() and substr() functions because when * 'mbstring.func_overload' is set in php.ini, the standard strlen() and * substr() are replaced by mb_strlen() and mb_substr(). */ /** * Computes the length of a string in bytes. * * @param string $str * * @throws Ex\EnvironmentIsBrokenException * * @return int */ public static function ourStrlen($str) { static $exists = null; if ($exists === null) { $exists = \extension_loaded('mbstring') && \ini_get('mbstring.func_overload') !== false && (int)\ini_get('mbstring.func_overload') & MB_OVERLOAD_STRING; } if ($exists) { $length = \mb_strlen($str, '8bit'); Core::ensureTrue($length !== false); return $length; } else { return \strlen($str); } } /** * Behaves roughly like the function substr() in PHP 7 does. * * @param string $str * @param int $start * @param int $length * * @throws Ex\EnvironmentIsBrokenException * * @return string|bool */ public static function ourSubstr($str, $start, $length = null) { static $exists = null; if ($exists === null) { $exists = \extension_loaded('mbstring') && \ini_get('mbstring.func_overload') !== false && (int)\ini_get('mbstring.func_overload') & MB_OVERLOAD_STRING; } // This is required to make mb_substr behavior identical to substr. // Without this, mb_substr() would return false, contra to what the // PHP documentation says (it doesn't say it can return false.) $input_len = Core::ourStrlen($str); if ($start === $input_len && !$length) { return ''; } if ($start > $input_len) { return false; } // mb_substr($str, 0, NULL, '8bit') returns an empty string on PHP 5.3, // so we have to find the length ourselves. Also, substr() doesn't // accept null for the length. if (! isset($length)) { if ($start >= 0) { $length = $input_len - $start; } else { $length = -$start; } } if ($length < 0) { throw new \InvalidArgumentException( "Negative lengths are not supported with ourSubstr." ); } if ($exists) { $substr = \mb_substr($str, $start, $length, '8bit'); // At this point there are two cases where mb_substr can // legitimately return an empty string. Either $length is 0, or // $start is equal to the length of the string (both mb_substr and // substr return an empty string when this happens). It should never // ever return a string that's longer than $length. if (Core::ourStrlen($substr) > $length || (Core::ourStrlen($substr) === 0 && $length !== 0 && $start !== $input_len)) { throw new Ex\EnvironmentIsBrokenException( 'Your version of PHP has bug #66797. Its implementation of mb_substr() is incorrect. See the details here: https://bugs.php.net/bug.php?id=66797' ); } return $substr; } return \substr($str, $start, $length); } /** * Computes the PBKDF2 password-based key derivation function. * * The PBKDF2 function is defined in RFC 2898. Test vectors can be found in * RFC 6070. This implementation of PBKDF2 was originally created by Taylor * Hornby, with improvements from http://www.variations-of-shadow.com/. * * @param string $algorithm The hash algorithm to use. Recommended: SHA256 * @param string $password The password. * @param string $salt A salt that is unique to the password. * @param int $count Iteration count. Higher is better, but slower. Recommended: At least 1000. * @param int $key_length The length of the derived key in bytes. * @param bool $raw_output If true, the key is returned in raw binary format. Hex encoded otherwise. * * @throws Ex\EnvironmentIsBrokenException * * @return string A $key_length-byte key derived from the password and salt. */ public static function pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output = false) { // Type checks: if (! \is_string($algorithm)) { throw new \InvalidArgumentException( 'pbkdf2(): algorithm must be a string' ); } if (! \is_string($password)) { throw new \InvalidArgumentException( 'pbkdf2(): password must be a string' ); } if (! \is_string($salt)) { throw new \InvalidArgumentException( 'pbkdf2(): salt must be a string' ); } // Coerce strings to integers with no information loss or overflow $count += 0; $key_length += 0; $algorithm = \strtolower($algorithm); Core::ensureTrue( \in_array($algorithm, \hash_algos(), true), 'Invalid or unsupported hash algorithm.' ); // Whitelist, or we could end up with people using CRC32. $ok_algorithms = [ 'sha1', 'sha224', 'sha256', 'sha384', 'sha512', 'ripemd160', 'ripemd256', 'ripemd320', 'whirlpool', ]; Core::ensureTrue( \in_array($algorithm, $ok_algorithms, true), 'Algorithm is not a secure cryptographic hash function.' ); Core::ensureTrue($count > 0 && $key_length > 0, 'Invalid PBKDF2 parameters.'); if (\function_exists('hash_pbkdf2')) { // The output length is in NIBBLES (4-bits) if $raw_output is false! if (! $raw_output) { $key_length = $key_length * 2; } return \hash_pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output); } $hash_length = Core::ourStrlen(\hash($algorithm, '', true)); $block_count = \ceil($key_length / $hash_length); $output = ''; for ($i = 1; $i <= $block_count; $i++) { // $i encoded as 4 bytes, big endian. $last = $salt . \pack('N', $i); // first iteration $last = $xorsum = \hash_hmac($algorithm, $last, $password, true); // perform the other $count - 1 iterations for ($j = 1; $j < $count; $j++) { /** * @psalm-suppress InvalidOperand */ $xorsum ^= ($last = \hash_hmac($algorithm, $last, $password, true)); } $output .= $xorsum; } if ($raw_output) { return (string) Core::ourSubstr($output, 0, $key_length); } else { return Encoding::binToHex((string) Core::ourSubstr($output, 0, $key_length)); } } }