适用于SAML的XML规范化

Question

我遇到了验证SAML 2.0 Assertion XML签名的问题.我正在使用simpleSAMLphp项目中的SAML2库,而后者又使用PHP xmlseclibs库来签名XML并验证签名.

我收到了我的合作伙伴的以下断言:

<saml:Assertion xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" Version="2.0" ID="_c43265fe-8cd5-410f-b63d-dac9f266d4c9" IssueInstant="2015-01-23T17:46:28.456Z"><saml:Issuer>uat.test.com/saml2.0</saml:Issuer><Signature xmlns="http://www.w3.org/2000/09/xmldsig#"><SignedInfo><CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/><Reference URI="#_c43265fe-8cd5-410f-b63d-dac9f266d4c9"><Transforms><Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/><Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"><InclusiveNamespaces xmlns="http://www.w3.org/2001/10/xml-exc-c14n#" PrefixList="#default saml ds xs xsi"/></Transform></Transforms><DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/><DigestValue>mFKEIdw+cEielORqscbHuAJhI58=</DigestValue></Reference></SignedInfo><SignatureValue>kEZHloxYJVqDg8oxLNpl+sbJYhv9r7yYU5yQi71gCNm/Cdtj9/P2LR5cnopKZZu+7j3PVimeZoir6RTTrdVKTLkp+PmvOmTlLH/LVtntQZ68TaUxUd3BvtQiKuJ8KFwWPmQ+W3RIKv4ySAsy6PUiWPcr8eIYpIiUA6rxCuSEpdA=</SignatureValue><KeyInfo><X509Data><X509Certificate>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</X509Certificate></X509Data></KeyInfo></Signature><saml:Subject><saml:NameID>000786320</saml:NameID><saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer"><saml:SubjectConfirmationData NotOnOrAfter="2015-01-23T17:51:28.471Z" Recipient="https://test.com/sso"/></saml:SubjectConfirmation></saml:Subject><saml:Conditions NotBefore="2015-01-23T17:41:28.456Z" NotOnOrAfter="2015-01-23T17:51:28.456Z"><saml:AudienceRestriction><saml:Audience>test.com:saml2.0</saml:Audience></saml:AudienceRestriction></saml:Conditions><saml:AuthnStatement AuthnInstant="2015-01-23T17:46:28.456Z" SessionIndex="SI-8bd89651-62da-4b7d-9a54-04eb2eb90784"><saml:AuthnContext><saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:Password</saml:AuthnContextClassRef></saml:AuthnContext></saml:AuthnStatement><saml:AttributeStatement><saml:Attribute Name="email" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic" FriendlyName="email"><saml:AttributeValue>invalidemail@invalid.com</saml:AttributeValue></saml:Attribute><saml:Attribute Name="firstName" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic" FriendlyName="firstName"><saml:AttributeValue>Diane</saml:AttributeValue></saml:Attribute><saml:Attribute Name="lastname" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic" FriendlyName="lastname"><saml:AttributeValue>Test</saml:AttributeValue></saml:Attribute><saml:Attribute Name="zipCode" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic" FriendlyName="zipCode"><saml:AttributeValue>02062</saml:AttributeValue></saml:Attribute><saml:Attribute Name="businessUnit" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic" FriendlyName="businessUnit"><saml:AttributeValue>78945</saml:AttributeValue></saml:Attribute><saml:Attribute Name="employeeID" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic" FriendlyName="employeeID"><saml:AttributeValue>000786320</saml:AttributeValue></saml:Attribute></saml:AttributeStatement></saml:Assertion>

签名元素请求独占的C14N规范化.该xmlseclibs库库canonicalizes此如下:

<saml:Assertion xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" ID="_c43265fe-8cd5-410f-b63d-dac9f266d4c9" IssueInstant="2015-01-23T17:46:28.456Z" Version="2.0"><saml:Issuer>uat.test.com/saml2.0</saml:Issuer><saml:Subject><saml:NameID>000786320</saml:NameID><saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer"><saml:SubjectConfirmationData NotOnOrAfter="2015-01-23T17:51:28.471Z" Recipient="https://test.com/sso"></saml:SubjectConfirmationData></saml:SubjectConfirmation></saml:Subject><saml:Conditions NotBefore="2015-01-23T17:41:28.456Z" NotOnOrAfter="2015-01-23T17:51:28.456Z"><saml:AudienceRestriction><saml:Audience>test.com:saml2.0</saml:Audience></saml:AudienceRestriction></saml:Conditions><saml:AuthnStatement AuthnInstant="2015-01-23T17:46:28.456Z" SessionIndex="SI-8bd89651-62da-4b7d-9a54-04eb2eb90784"><saml:AuthnContext><saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:Password</saml:AuthnContextClassRef></saml:AuthnContext></saml:AuthnStatement><saml:AttributeStatement><saml:Attribute FriendlyName="email" Name="email" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>invalidemail@invalid.com</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="firstName" Name="firstName" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>Diane</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="lastname" Name="lastname" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>Test</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="zipCode" Name="zipCode" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>02062</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="businessUnit" Name="businessUnit" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>78945</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="employeeID" Name="employeeID" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>000786320</saml:AttributeValue></saml:Attribute></saml:AttributeStatement></saml:Assertion>

然而,我的伙伴实际签署的元素是这样的:

<saml:Assertion xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" ID="_c43265fe-8cd5-410f-b63d-dac9f266d4c9" IssueInstant="2015-01-23T17:46:28.456Z" Version="2.0"><saml:Issuer>uat.test.com/saml2.0</saml:Issuer><saml:Subject><saml:NameID>000786320</saml:NameID><saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer"><saml:SubjectConfirmationData NotOnOrAfter="2015-01-23T17:51:28.471Z" Recipient="https://test.com/sso"></saml:SubjectConfirmationData></saml:SubjectConfirmation></saml:Subject><saml:Conditions NotBefore="2015-01-23T17:41:28.456Z" NotOnOrAfter="2015-01-23T17:51:28.456Z"><saml:AudienceRestriction><saml:Audience>test.com:saml2.0</saml:Audience></saml:AudienceRestriction></saml:Conditions><saml:AuthnStatement AuthnInstant="2015-01-23T17:46:28.456Z" SessionIndex="SI-8bd89651-62da-4b7d-9a54-04eb2eb90784"><saml:AuthnContext><saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:Password</saml:AuthnContextClassRef></saml:AuthnContext></saml:AuthnStatement><saml:AttributeStatement><saml:Attribute FriendlyName="email" Name="email" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>invalidemail@invalid.com</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="firstName" Name="firstName" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>Diane</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="lastname" Name="lastname" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>Test</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="zipCode" Name="zipCode" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>02062</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="businessUnit" Name="businessUnit" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>78945</saml:AttributeValue></saml:Attribute><saml:Attribute FriendlyName="employeeID" Name="employeeID" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml:AttributeValue>000786320</saml:AttributeValue></saml:Attribute></saml:AttributeStatement></saml:Assertion>

几乎相同,但没有xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"命名空间.该xsi命名空间中的签名变换元素中提到:<Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"><InclusiveNamespaces xmlns="http://www.w3.org/2001/10/xml-exc-c14n#" PrefixList="#default saml ds xs xsi"/></Transform>

由于签名中的SHA1摘要与在元素上计算的摘要xmlseclibs不匹配,因此SAML身份验证失败.

所以我想知道谁在这里是正确的 - 是否必须包含xsi命名空间(即使此命名空间中没有元素),因为它包含在InclusiveNamespaces中,或者如果不xmlseclibs包含,为什么包含该命名空间呢？C14N规范化？

Answer 1

实际上，一些进一步的调试表明问题出在 SAML2 库中的错误（它是 smipleSAMLphp 项目的一部分： https: //github.com/simplesamlphp/saml2）。

解密元素 SAML2 库时执行以下操作：

    $xml = '<root xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" '.
                 'xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">' .
        $decrypted .
        '</root>';
    $newDoc = new DOMDocument();

（参见https://github.com/simplesamlphp/saml2/blob/master/src/SAML2/Utils.php第 494 行）

这是一种解决方法，以防在仅序列化文档的子集进行加密时出现一些孤立元素。不幸的是，这会创建一个额外的命名空间，如果包含在 InclusiveNamespaces PrefixList 中，它xsi会出现在后续的规范化中。xsi

将其更改为：

    $xml = '<root xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">'.
        $decrypted .
        '</root>';
    $newDoc = new DOMDocument();

实际上对我来说确实有效。然而，这只是一个快速破解，并不理想，因为它可能会为不同的实现引入一些其他错误。我想需要与 simpleSAMLphp 库的创建者合作，找到一个更优雅的长期解决方案。