<?php
/**
* Zend Framework
*
* LICENSE
*
* This source file is subject to the new BSD license that is bundled
* with this package in the file LICENSE.txt.
* It is also available through the world-wide-web at this URL:
* http://framework.zend.com/license/new-bsd
* If you did not receive a copy of the license and are unable to
* obtain it through the world-wide-web, please send an email
* to license@zend.com so we can send you a copy immediately.
*
* @category Zend
* @package Zend_InfoCard
* @subpackage Zend_InfoCard_Xml_Security
* @copyright Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
* @version $Id: Security.php 24594 2012-01-05 21:27:01Z matthew $
*/
/**
* Zend_InfoCard_Xml_Security_Transform
*/
require_once 'Zend/InfoCard/Xml/Security/Transform.php';
/**
*
* @category Zend
* @package Zend_InfoCard
* @subpackage Zend_InfoCard_Xml_Security
* @copyright Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
*/
class Zend_InfoCard_Xml_Security
{
/**
* ASN.1 type INTEGER class
*/
const ASN_TYPE_INTEGER = 0x02;
/**
* ASN.1 type BIT STRING class
*/
const ASN_TYPE_BITSTRING = 0x03;
/**
* ASN.1 type SEQUENCE class
*/
const ASN_TYPE_SEQUENCE = 0x30;
/**
* The URI for Canonical Method C14N Exclusive
*/
const CANONICAL_METHOD_C14N_EXC = 'http://www.w3.org/2001/10/xml-exc-c14n#';
/**
* The URI for Signature Method SHA1
*/
const SIGNATURE_METHOD_SHA1 = 'http://www.w3.org/2000/09/xmldsig#rsa-sha1';
/**
* The URI for Digest Method SHA1
*/
const DIGEST_METHOD_SHA1 = 'http://www.w3.org/2000/09/xmldsig#sha1';
/**
* The Identifier for RSA Keys
*/
const RSA_KEY_IDENTIFIER = '300D06092A864886F70D0101010500';
/**
* Constructor (disabled)
*
* @return void
*/
private function __construct()
{
}
/**
* Validates the signature of a provided XML block
*
* @param string $strXMLInput An XML block containing a Signature
* @return bool True if the signature validated, false otherwise
* @throws Zend_InfoCard_Xml_Security_Exception
*/
static public function validateXMLSignature($strXMLInput)
{
if(!extension_loaded('openssl')) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("You must have the openssl extension installed to use this class");
}
$sxe = simplexml_load_string($strXMLInput);
if(!isset($sxe->Signature)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Could not identify XML Signature element");
}
if(!isset($sxe->Signature->SignedInfo)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Signature is missing a SignedInfo block");
}
if(!isset($sxe->Signature->SignatureValue)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Signature is missing a SignatureValue block");
}
if(!isset($sxe->Signature->KeyInfo)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Signature is missing a KeyInfo block");
}
if(!isset($sxe->Signature->KeyInfo->KeyValue)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Signature is missing a KeyValue block");
}
switch((string)$sxe->Signature->SignedInfo->CanonicalizationMethod['Algorithm']) {
case self::CANONICAL_METHOD_C14N_EXC:
$cMethod = (string)$sxe->Signature->SignedInfo->CanonicalizationMethod['Algorithm'];
break;
default:
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Unknown or unsupported CanonicalizationMethod Requested");
break;
}
switch((string)$sxe->Signature->SignedInfo->SignatureMethod['Algorithm']) {
case self::SIGNATURE_METHOD_SHA1:
$sMethod = (string)$sxe->Signature->SignedInfo->SignatureMethod['Algorithm'];
break;
default:
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Unknown or unsupported SignatureMethod Requested");
break;
}
switch((string)$sxe->Signature->SignedInfo->Reference->DigestMethod['Algorithm']) {
case self::DIGEST_METHOD_SHA1:
$dMethod = (string)$sxe->Signature->SignedInfo->Reference->DigestMethod['Algorithm'];
break;
default:
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Unknown or unsupported DigestMethod Requested");
break;
}
$base64DecodeSupportsStrictParam = version_compare(PHP_VERSION, '5.2.0', '>=');
if ($base64DecodeSupportsStrictParam) {
$dValue = base64_decode((string)$sxe->Signature->SignedInfo->Reference->DigestValue, true);
} else {
$dValue = base64_decode((string)$sxe->Signature->SignedInfo->Reference->DigestValue);
}
if ($base64DecodeSupportsStrictParam) {
$signatureValue = base64_decode((string)$sxe->Signature->SignatureValue, true);
} else {
$signatureValue = base64_decode((string)$sxe->Signature->SignatureValue);
}
$transformer = new Zend_InfoCard_Xml_Security_Transform();
foreach($sxe->Signature->SignedInfo->Reference->Transforms->children() as $transform) {
$transformer->addTransform((string)$transform['Algorithm']);
}
$transformed_xml = $transformer->applyTransforms($strXMLInput);
$transformed_xml_binhash = pack("H*", sha1($transformed_xml));
if(!self::_secureStringCompare($transformed_xml_binhash, $dValue)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Locally Transformed XML does not match XML Document. Cannot Verify Signature");
}
$public_key = null;
switch(true) {
case isset($sxe->Signature->KeyInfo->KeyValue->X509Certificate):
$certificate = (string)$sxe->Signature->KeyInfo->KeyValue->X509Certificate;
$pem = "-----BEGIN CERTIFICATE-----\n" .
wordwrap($certificate, 64, "\n", true) .
"\n-----END CERTIFICATE-----";
$public_key = openssl_pkey_get_public($pem);
if(!$public_key) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Unable to extract and prcoess X509 Certificate from KeyValue");
}
break;
case isset($sxe->Signature->KeyInfo->KeyValue->RSAKeyValue):
if(!isset($sxe->Signature->KeyInfo->KeyValue->RSAKeyValue->Modulus) ||
!isset($sxe->Signature->KeyInfo->KeyValue->RSAKeyValue->Exponent)) {
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("RSA Key Value not in Modulus/Exponent form");
}
$modulus = base64_decode((string)$sxe->Signature->KeyInfo->KeyValue->RSAKeyValue->Modulus);
$exponent = base64_decode((string)$sxe->Signature->KeyInfo->KeyValue->RSAKeyValue->Exponent);
$pem_public_key = self::_getPublicKeyFromModExp($modulus, $exponent);
$public_key = openssl_pkey_get_public ($pem_public_key);
break;
default:
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Unable to determine or unsupported representation of the KeyValue block");
}
$transformer = new Zend_InfoCard_Xml_Security_Transform();
$transformer->addTransform((string)$sxe->Signature->SignedInfo->CanonicalizationMethod['Algorithm']);
// The way we are doing our XML processing requires that we specifically add this
// (even though it's in the <Signature> parent-block).. otherwise, our canonical form
// fails signature verification
$sxe->Signature->SignedInfo->addAttribute('xmlns', 'http://www.w3.org/2000/09/xmldsig#');
$canonical_signedinfo = $transformer->applyTransforms($sxe->Signature->SignedInfo->asXML());
if(@openssl_verify($canonical_signedinfo, $signatureValue, $public_key)) {
return (string)$sxe->Signature->SignedInfo->Reference['URI'];
}
return false;
}
/**
* Transform an RSA Key in Modulus/Exponent format into a PEM encoding and
* return an openssl resource for it
*
* @param string $modulus The RSA Modulus in binary format
* @param string $exponent The RSA exponent in binary format
* @return string The PEM encoded version of the key
*/
static protected function _getPublicKeyFromModExp($modulus, $exponent)
{
$modulusInteger = self::_encodeValue($modulus, self::ASN_TYPE_INTEGER);
$exponentInteger = self::_encodeValue($exponent, self::ASN_TYPE_INTEGER);
$modExpSequence = self::_encodeValue($modulusInteger . $exponentInteger, self::ASN_TYPE_SEQUENCE);
$modExpBitString = self::_encodeValue($modExpSequence, self::ASN_TYPE_BITSTRING);
$binRsaKeyIdentifier = pack( "H*", self::RSA_KEY_IDENTIFIER );
$publicKeySequence = self::_encodeValue($binRsaKeyIdentifier . $modExpBitString, self::ASN_TYPE_SEQUENCE);
$publicKeyInfoBase64 = base64_encode( $publicKeySequence );
$publicKeyString = "-----BEGIN PUBLIC KEY-----\n";
$publicKeyString .= wordwrap($publicKeyInfoBase64, 64, "\n", true);
$publicKeyString .= "\n-----END PUBLIC KEY-----\n";
return $publicKeyString;
}
/**
* Encode a limited set of data types into ASN.1 encoding format
* which is used in X.509 certificates
*
* @param string $data The data to encode
* @param const $type The encoding format constant
* @return string The encoded value
* @throws Zend_InfoCard_Xml_Security_Exception
*/
static protected function _encodeValue($data, $type)
{
// Null pad some data when we get it (integer values > 128 and bitstrings)
if( (($type == self::ASN_TYPE_INTEGER) && (ord($data) > 0x7f)) ||
($type == self::ASN_TYPE_BITSTRING)) {
$data = "\0$data";
}
$len = strlen($data);
// encode the value based on length of the string
// I'm fairly confident that this is by no means a complete implementation
// but it is enough for our purposes
switch(true) {
case ($len < 128):
return sprintf("%c%c%s", $type, $len, $data);
case ($len < 0x0100):
return sprintf("%c%c%c%s", $type, 0x81, $len, $data);
case ($len < 0x010000):
return sprintf("%c%c%c%c%s", $type, 0x82, $len / 0x0100, $len % 0x0100, $data);
default:
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Could not encode value");
}
require_once 'Zend/InfoCard/Xml/Security/Exception.php';
throw new Zend_InfoCard_Xml_Security_Exception("Invalid code path");
}
/**
* Securely compare two strings for equality while avoided C level memcmp()
* optimisations capable of leaking timing information useful to an attacker
* attempting to iteratively guess the unknown string (e.g. password) being
* compared against.
*
* @param string $a
* @param string $b
* @return bool
*/
static protected function _secureStringCompare($a, $b)
{
if (strlen($a) !== strlen($b)) {
return false;
}
$result = 0;
for ($i = 0; $i < strlen($a); $i++) {
$result |= ord($a[$i]) ^ ord($b[$i]);
}
return $result == 0;
}
}