【发布时间】：2018-09-05 05:42:44
【问题描述】：
我是这里的服务提供商，我使用 C#。我的客户在允许用户访问我的服务之前发送我试图验证的 SAML 响应。对于这个特定的客户端，它会在这一行抛出无法转换的错误，
SAMLAssertion samlAssertion = new SAMLAssertion((XmlElement)(samlResponse.Assertions[0]));
这里的 samlResponse 是 SAMLResponse 的一个对象。断言存在于 samlResponse 中，但它无法将该断言强制转换为 XmlElement。 错误，
无法转换类型的对象 'ComponentSpace.SAML2.Assertions.SAMLAssertion' 键入 'System.Xml.XmlElement'。
这是包含我从客户那里得到的签名断言的 saml 响应，
<saml2p:Response xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol" Destination="My Webseite URL to receive SAML Response" ID="_3fe7259adc56de5d" IssueInstant="2018-02-20T21:00:57.313Z" Version="2.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"><saml2:Issuer xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity">IDP URL</saml2:Issuer><ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" /><ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" /><ds:Reference URI="#_3fe7259adc56de5d"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" /><ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"><ec:InclusiveNamespaces xmlns:ec="http://www.w3.org/2001/10/xml-exc-c14n#" PrefixList="xs" /></ds:Transform></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" /><ds:DigestValue>tuVNmHfn7RPXI1j0bzpoNuzJUXY=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>wOPI5Bjp+NUstb0udKkXslqTS4jZbvWBPj/trdTXHGq343ECWQQRFUsOfoWrFLwKvsfVqcBpMGYnICs4xS+BZU4jGktakyck0xRcRlROaIGeAZY0Ywran821h9CUdLntNqNTGrj5zyPpWGBvmvmr74oVFUo/LmPctuMWLOTfmA2n3b6VrG1YG5YEDb9VodoSWxjyKJNmZNFSriWX79U+WkTw1N3h6z4BryJwMbsMeIQN9TkwkL/qzBKSt5z1+gF54KBBm4GvJ59+Ko8mt0TflJsmSVsxq68eyqvBZp6hvDVMbNC1JRim4q+BHRU3C1OANCHM4ZUOhpKdG7Xo2VHLXw==</ds:SignatureValue><ds:KeyInfo><ds:X509Data><ds:X509Certificate>Certificate </ds:X509Certificate></ds:X509Data></ds:KeyInfo></ds:Signature><saml2p:Status><saml2p:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success" /></saml2p:Status><saml2:Assertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" ID="_3fd1bf8e757aecea" IssueInstant="2018-02-20T21:00:57.313Z" Version="2.0"><saml2:Issuer Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity">IDP URL</saml2:Issuer><saml2:Subject><saml2:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">110015</saml2:NameID><saml2:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer"><saml2:SubjectConfirmationData NotOnOrAfter="2018-02-20T21:03:57.313Z" Recipient="My Webseite to receive saml response" /></saml2:SubjectConfirmation></saml2:Subject><saml2:Conditions NotBefore="2018-02-20T20:57:57.313Z" NotOnOrAfter="2018-02-20T21:03:57.313Z"><saml2:AudienceRestriction><saml2:Audience>My website url to receive saml response</saml2:Audience></saml2:AudienceRestriction></saml2:Conditions><saml2:AuthnStatement AuthnInstant="2018-02-20T20:57:57.313Z" SessionIndex="_3fd1bf8e757aecea"><saml2:SubjectLocality Address="216.6.202.133" /><saml2:AuthnContext><saml2:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport</saml2:AuthnContextClassRef></saml2:AuthnContext></saml2:AuthnStatement><saml2:AttributeStatement><saml2:Attribute FriendlyName="NameID" Name="NameId" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:basic"><saml2:AttributeValue xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="xs:string">110015</saml2:AttributeValue></saml2:Attribute></saml2:AttributeStatement></saml2:Assertion></saml2p:Response>
PS：我使用来自https://www.samltool.com/generic_sso_res.php 的签名断言样本测试了 saml 响应，并且使用相同的代码可以正常工作。
【问题讨论】：