Not able to SignOut using Saml2 from Sustainsys - asp.net-core

Question

This should be redirecting my app to my AdFs signOut Page, and then redirect me back to my app.
However, it simply redirects me to my route "/logout".
Watching the log on my ADFS server nothing happens.
[AllowAnonymous]
[HttpGet]
[Route("api/logout")]
public async Task<IActionResult> Logout()
{
return SignOut(new AuthenticationProperties()
{
RedirectUri = "/logout"
},
Saml2Defaults.Scheme);
}
SignIn works fine. I even tried this same approach, but does not work. Here, the ReturnUrl method gets the location from HttpContext.Response.Header. When I try this for the logout, the location is always null.
[AllowAnonymous]
[HttpGet]
[Route("api/login")]
public async Task<string> LoginAdfs()
{
string redirectUri = _appSettings.Saml.SpEntityId;
await HttpContext.ChallengeAsync(new AuthenticationProperties
{
RedirectUri = string.Concat(redirectUri, "/autenticado")
});
return ReturnUrl();
}
Any idea what could be happening?
UPDATE 21/11/2019
Turns out the Saml2Handler is simply not trying to send the request to the server. I'm getting these messages on my output window:
Sustainsys.Saml2.AspNetCore2.Saml2Handler: Debug: Initiating logout, checking requirements for federated logout
Issuer of LogoutNameIdentifier claim (should be Idp entity id):
Issuer is a known Idp: False
Session index claim (should have a value):
Idp has SingleLogoutServiceUrl:
There is a signingCertificate in SPOptions: True
Idp configured to DisableOutboundLogoutRequests (should be false):
Sustainsys.Saml2.AspNetCore2.Saml2Handler: Information: Federated logout not possible, redirecting to post-logout
Here is my StartUp Configuration, I don't get what is wrong here:
ServiceCertificate se = new ServiceCertificate()
{
Certificate = new X509Certificate2(SpCert, "",X509KeyStorageFlags.MachineKeySet),
Use = CertificateUse.Signing
};
SPOptions sp = new SPOptions
{
AuthenticateRequestSigningBehavior = SigningBehavior.Never,
EntityId = new EntityId(SpEntityId),
ReturnUrl = new Uri("/login"),
NameIdPolicy = new Sustainsys.Saml2.Saml2P.Saml2NameIdPolicy(null, Sustainsys.Saml2.Saml2P.NameIdFormat.Unspecified),
};
sp.ServiceCertificates.Add(se);
IdentityProvider idp = new IdentityProvider(new EntityId(appSettings.Saml.EntityId), sp);
idp.Binding = Saml2BindingType.HttpPost;
idp.AllowUnsolicitedAuthnResponse = true;
//idp.WantAuthnRequestsSigned = true;
idp.SingleSignOnServiceUrl = new Uri("/login");
//idp.LoadMetadata = true;
idp.SigningKeys.AddConfiguredKey(new X509Certificate2(IdpCert));
idp.MetadataLocation = theMetadata;
idp.DisableOutboundLogoutRequests = true;

Answer 1

For the logout to work, two special claims "LogoutNameIdentifier" and "SessionIndex" (full names are http://Sustainsys.se/Saml2/LogoutNameIdentifier and http://Sustainsys.se/Saml2/SessionIndex need to be present on the user. Those carries information about the current session that the Saml2 library needs to be able to do a logout.
Now I don't see your entire Startup, so I cannot understand your application's flow. But those claims should be present in the identity returned by the library - possibly stored in an External cookie (if you are using asp.net identity). When your application then sets the application cookie those two claims must be carried over to the session identity.
Also you have actually disabled outbound logout with DisableOutboundLogoutRequests. But that's not the main problem here as your logs indicates that the required claims are not present.

Answer 2

From my own experience, the two claims, as mentioned by Anders Abel, should be present on the user. I had not seen these claims until I passed all of the claims along with the sign-in request. ASP.NET Core recreates the principal on SignInAsync and needs claims to be passed in with the request.
With the following, I am able to fulfill a SingleLogout with my service:
await HttpContext.SignInAsync(user.SubjectId, user.Username, props, user.Claims.ToArray());

Answer 3

what you are using as a service provider.