SignatureDescription could not be created for the signature algorithm supplied

[Calvin Pang]

I could get the SAML response,

when hit the code samlResponse.IsValid(), then i got the error message as below :

SignatureDescription could not be created for the signature algorithm suppliedSystem.Security.Cryptography.CryptographicException: SignatureDescription could not be created for the signature algorithm supplied.
at System.Security.Cryptography.Xml.SignedXml.CheckSignedInfo(AsymmetricAlgorithm key)
at System.Security.Cryptography.Xml.SignedXml.CheckSignature(AsymmetricAlgorithm key)
at System.Security.Cryptography.Xml.SignedXml.CheckSignature(X509Certificate2 certificate, Boolean verifySignatureOnly)
at Testing.Security.SAML.SSOSignIn.Response.IsValid()

could you please help.
Thank you.

[Alexander Yumashev]

Which .NET version you're on?

[Calvin Pang]

.NetFramework 4.5.2

[Calvin Pang]

I had comment the code signedXml.CheckSignature(_certificate, true) and its work as expected .

do we really need the checkSignature ? what will happen if we don't checkSignature ?

[Alexander Yumashev]

1. Please consider upgrading to 4.7.2 or later
2. Yes you do need it otherwise how do you verify that the response is really from the real provider, not a MITM attacker

[Calvin Pang]

I had solved the issue. just add this line.
CryptoConfig.AddAlgorithm(typeof(RSAPKCS1SHA256SignatureDescription), "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256");

the solution can be found in below links :
https://stackoverflow.com/questions/16728558/signed-xml-signature-verification-for-sso-saml-using-sha256

Thank you.