Using WIF to read a message whose signature doesn't have KeyInfo

Hi,

I'm using WIF to read a message whose signature doesn't have KeyInfo element

<Response ID="idc640375b45ac4293ae9a70bab7991991" Version="2.0" IssueInstant="2016-01-11T09:40:28.6192428Z" Destination="https://idp.example.local/..." InResponseTo="idd14f45aa327748269e2d4adba05e52cd" xmlns="urn:oasis:names:tc:SAML:2.0:protocol">
 <Issuer xmlns="urn:oasis:names:tc:SAML:2.0:assertion">https://samples.example.local/.../</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/2001/04/xmldsig-more#rsa-sha256" />
   <Reference URI="#idc640375b45ac4293ae9a70bab7991991">
    <Transforms>
     <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
     <Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
    </Transforms>
    <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" />
    <DigestValue>BvSo2SLM+rL+FCx9UwiWApIbT12/9ffKZbN9Iuc1O54=</DigestValue>
   </Reference>
  </SignedInfo>
  <SignatureValue>IkQ7iPrTPzmc+DWJ4J9AfBmZm1cOLrVQu2o6Dd0/jKvWp3xb8D1gNqrShHo57qx8t0cLatW2ZJvC/YtGCuXNUlm8VM7OTakn3rSBUJmY+5yWyhkD+EOPkBOZFoXYjQCtfLXaZhM8sYYeJnPEEpRF9Nl/Mop/15aQjbRczmiPiy0lgohMjF/TIQp401CUNbXcHsvUf+DDcTqNmUoyXE0cbrKr351bIqXsPLagQ7OW0nVDwD0B2s4uYkPR8ZJegaSma9keGI4fqRTteubRTznrxFdbi4yWof9McdlsYpzvaqIJsoQHSEpiKXeg1sK83KxLgMfHyRofznD7BW6iFhHAlA==</SignatureValue>
 </Signature>
 <Status>
  <StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success" />
 </Status>

WIF refuses to process the message and throws an exception:

[InvalidOperationException: ID3276: The signing credentials cannot be resolved because signed XML does not contain a SecurityKeyIdentifier.]
   System.IdentityModel.EnvelopedSignatureReader.ResolveSigningCredentials() +527
   System.IdentityModel.EnvelopedSignatureReader.OnEndOfRootElement() +55
   System.IdentityModel.EnvelopedSignatureReader.Read() +90
   System.Xml.XmlReader.ReadEndElement() +54

signature is valid: "XML Signature defines usage of the <ds:KeyInfo> element. SAML does not require the use of <ds:KeyInfo>, nor does it impose any restrictions on its use. Therefore, <ds:KeyInfo> MAY be absent."

Could anyone please show me if there is a workaround for this issue? Why does WIF enforce such a rule? To make the situation more frustrating, all the relevant classes are marked as internal which makes extending them impossible.

Thank you in advance,

Thuan.