Verify signature on SAML assertion

Question

I've already asked this question on StackOverflow (http://stackoverflow.com/questions/25394137/verify-signature-on-saml-assertion), but I'm hoping to get a better response here. I'm trying to validate some SAML that looks like this:
<samlp2:Response Destination="http://www.testhabaGoba.com" ID="ResponseId_934151edfe060ceec3067670c2f0f1ea" IssueInstant="2013-09-24T14:33:29.507Z" Version="2.0" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:samlp2="urn:oasis:names:tc:SAML:2.0:protocol">
<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
</ds:Signature>
<saml2:Assertion ID="SamlAssertion-05fd8af7f2c9972e69cdbca612d3f3b8" IssueInstant="2013-09-24T14:33:29.496Z" Version="2.0" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">
<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
</ds:Signature>
</saml2:Assertion>
</samlp2:Response>
The signature on the response always passes, but the signature on the assertion always fails. Even when I use a SAML that doesn't sign the response the assertion signature fails. Here's a condensed version of the code I'm using:
foreach (XmlElement node in xmlDoc.SelectNodes("//*[local-name()='Signature']"))
{// Verify this Signature block
SignedXml signedXml = new SignedXml(node.ParentNode as XmlElement);
signedXml.LoadXml(node);
KeyInfoX509Data x509Data = signedXml.Signature.KeyInfo.OfType<KeyInfoX509Data>().First();
// Verify certificate
X509Certificate2 cert = x509Data.Certificates[0] as X509Certificate2;
log.Info(string.Format("Cert s/n: {0}", cert.SerialNumber));
VerifyX509Chain(cert);// Custom method
// Check for approval
X509Store store = new X509Store(StoreName.TrustedPublisher, StoreLocation.LocalMachine);
store.Open(OpenFlags.ReadOnly);
X509Certificate2Collection collection = store.Certificates.Find(X509FindType.FindBySerialNumber, cert.SerialNumber, true);
Debug.Assert(collection.Count == 1);// Standing in for brevity
// Verify signature
signedXml.CheckSignature(cert, true);
Everything works except the CheckSignature method. It's the only thing that fails and it always fails the SAML assertion. What am I doing wrong?

Answer 1

Hello Matthew T. Ricks,
Personally after reading your post I don't think this issue is related to this forum "Discuss and ask questions about the C# programming language, IDE, libraries, samples, and tools."
The problem is due to SAML assertion fail and I read something like this
http://docs.oracle.com/cd/E21455_01/common/tutorials/authn_saml_xml_sig.html to konw what is SAML and how it works. I will recommend you consult SAML related forum to ask this question.
Regards,
Barry
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