ADFS ActAs token missing AuthnStatement

Question

I am trying to write a web application that calls a REST service. The REST service requires an OAuth token for the user. Using the username and password of the user I am able to get a SAML token (1st assertion below) that the OAuth STS is able to use to issue me a valid OAuth token. Because I am in a web application I would prefer to use an ActAs SAML token instead of prompting for the username and password of the user that has already authenticated with the domain (SSO). When I configure ADFS 2.0 to issue an ActAs token (2nd assertion below) it is missing the AuthnStatement part of the assertion. The OAuth STS is complaining about that. Contacting their support they tell me to configure ADFS 2.0 to include AuthnStatement in the assertion perhaps with a custom rule. The only difference in the current ADFS 2.0 configuration between these two is the Delegation Authorization tab. The only difference in the code is whose credentials are used (actual user vs. delegated user) and setting the ActAs property on the RST.

Is there a way to configure ADFS 2.0 to include this? I don't think a custom rule will do me any good since a custom rule will only create more claims and the AuthnStatement isn't a claim.

Code used to create the token:

var rst = new RequestSecurityToken
{
RequestType = "http://docs.oasis-open.org/ws-sx/ws-trust/200512/Issue",
AppliesTo = new EndpointReference("https://rpserver.mydomain.com/sap/bc/sec/oauth2/token"),
KeyType = "http://docs.oasis-open.org/ws-sx/ws-trust/200512/Bearer",
TokenType = "urn:oasis:names:tc:SAML:2.0:assertion",

//commented for actual user and uncommented for ActAs
//the token is from the actual user

//ActAs = new SecurityTokenElement(token)  
};

SAML token retrieved using the username and password of the actual user.

<Assertion ID="_d7ea7eb9-e9f6-45a8-95e4-76a53c151de5" IssueInstant="2014-06-18T12:49:32.815Z" Version="2.0" xmlns="urn:oasis:names:tc:SAML:2.0:assertion">
<Issuer>
http://adfsservername.mydomain.com/adfs/services/trust</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/2001/04/xmldsig-more#rsa-sha256" />
<ds:Reference URI="#_d7ea7eb9-e9f6-45a8-95e4-76a53c151de5">
<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#" />
</ds:Transforms>
<ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" />
<ds:DigestValue>
G4LDaRLEEgsKa1/kRwFo+X2BWv0z32Mi0QRym5GlteU=</ds:DigestValue>
</ds:Reference>
</ds:SignedInfo>
<ds:SignatureValue>
removed for clarity</ds:SignatureValue>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<ds:X509Data>
<ds:X509Certificate>
removed for clarity</ds:X509Certificate>
</ds:X509Data>
</KeyInfo>
</ds:Signature>
<Subject>
<NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">
USERIDGOESHERE</NameID>
<SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
<SubjectConfirmationData NotOnOrAfter="2014-06-18T12:54:32.815Z" />
</SubjectConfirmation>
</Subject>
<Conditions NotBefore="2014-06-18T12:49:32.794Z" NotOnOrAfter="2014-06-18T13:49:32.794Z">
<AudienceRestriction>
<Audience>
https://rpservername.mydomain.com/sap/bc/sec/oauth2/token</Audience>
</AudienceRestriction>
</Conditions>
<AttributeStatement>
<Attribute Name="http://schemas.xmlsoap.org/claims/CommonName">
<AttributeValue>
USERIDGOESHERE</AttributeValue>
</Attribute>
<Attribute Name="client_id">
<AttributeValue>
MLM_MAT_USER</AttributeValue>
</Attribute>
</AttributeStatement>
<AuthnStatement AuthnInstant="2014-06-18T12:49:32.721Z">
<AuthnContext>
<AuthnContextClassRef>
urn:oasis:names:tc:SAML:2.0:ac:classes:Password</AuthnContextClassRef>
</AuthnContext>
</AuthnStatement>
</Assertion>

SAML token retrieved using the username and password of a generic account using delegation.

<Assertion ID="_23107d88-d82d-4fa8-b12a-a447aeb6d5f2" IssueInstant="2014-06-18T12:26:03.005Z" Version="2.0" xmlns="urn:oasis:names:tc:SAML:2.0:assertion">
<Issuer>
http://adfsservername.mydomain.com/adfs/services/trust</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/2001/04/xmldsig-more#rsa-sha256" />
<ds:Reference URI="#_23107d88-d82d-4fa8-b12a-a447aeb6d5f2">
<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#" />
</ds:Transforms>
<ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" />
<ds:DigestValue>
sKf+1gtkbA9Hbk3H82j9dXf7zlebd3EOcrqlMyygpoY=</ds:DigestValue>
</ds:Reference>
</ds:SignedInfo>
<ds:SignatureValue>
removed for clarity</ds:SignatureValue>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<ds:X509Data>
<ds:X509Certificate>
removed for clarity</ds:X509Certificate>
</ds:X509Data>
</KeyInfo>
</ds:Signature>
<Subject>
<NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">
USERIDGOESHERE</NameID>
<SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
<SubjectConfirmationData NotOnOrAfter="2014-06-18T12:31:03.005Z" />
</SubjectConfirmation>
</Subject>
<Conditions NotBefore="2014-06-18T12:26:02.872Z" NotOnOrAfter="2014-06-18T13:26:02.872Z">
<AudienceRestriction>
<Audience>
https://rpservername.mydomain.com/sap/bc/sec/oauth2/token</Audience>
</AudienceRestriction>
</Conditions>
<AttributeStatement>
<Attribute Name="client_id">
<AttributeValue>
MLM_MAT_USER</AttributeValue>
</Attribute>
<Attribute Name="http://schemas.xmlsoap.org/ws/2009/09/identity/claims/actor">
<AttributeValue>
&lt;Actor&gt;&lt;Attribute Name="http://schemas.xmlsoap.org/claims/CommonName" xmlns="urn:oasis:names:tc:SAML:2.0:assertion"&gt;&lt;AttributeValue&gt;ACTORUSERIDGOESHERE&lt;/AttributeValue&gt;&lt;/Attribute&gt;&lt;Attribute Name="http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier" xmlns="urn:oasis:names:tc:SAML:2.0:assertion"&gt;&lt;AttributeValue&gt;ACTORUSERIDGOESHERE&lt;/AttributeValue&gt;&lt;/Attribute&gt;&lt;Attribute Name="client_id" xmlns="urn:oasis:names:tc:SAML:2.0:assertion"&gt;&lt;AttributeValue&gt;MLM_MAT_USER&lt;/AttributeValue&gt;&lt;/Attribute&gt;&lt;Attribute Name="http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationmethod" xmlns="urn:oasis:names:tc:SAML:2.0:assertion"&gt;&lt;AttributeValue&gt;http://schemas.microsoft.com/ws/2008/06/identity/authenticationmethod/password&lt;/AttributeValue&gt;&lt;/Attribute&gt;&lt;Attribute Name="http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationinstant" xmlns="urn:oasis:names:tc:SAML:2.0:assertion"&gt;&lt;AttributeValue a:type="tn:dateTime" xmlns:tn="http://www.w3.org/2001/XMLSchema" xmlns:a="http://www.w3.org/2001/XMLSchema-instance"&gt;2014-06-18T12:26:02.681Z&lt;/AttributeValue&gt;&lt;/Attribute&gt;&lt;/Actor&gt;</AttributeValue>
</Attribute>
</AttributeStatement>
</Assertion>

Answer 1

I contacted Microsoft support directly and here is the paraphrase. "It can't be done and it is by design that it can't be done."