IdentityServer4.WsFederation

Sample for implementing WS-Federation IdP support for IdentityServer4 with .NET core.

Overview

IdentityServer4 is designed to be extensible with custom protocol endpoints. This repo shows a simple implementation of WS-Federation IdP services. This is useful for connecting SharePoint or older ASP.NET relying parties to IdentityServer.

This is not supposed to be a generic WS-Federation implementation, but is rather a sample that you can use as a starting point to build your own WS-Federation support (or even for inspiration for integrating other custom protocols, which are not natively supported by IdentityServer4).

The following is a brief description of some technical points of interest. Feel free to amend this document if more details are needed.

.NET Support

The underlying WS-Federation classes use .NET Core.

WS-Federation endpoint

The WS-Federation endpoint (metadata, sign-in and out) is implemented via an MVC controller (~/wsfederation). This controller handles the WS-Federation protocol requests and redirects the user to the login page if needed.

The login page will then use the normal return URL mechanism to redirect back to the WS-Federation endpoint to create the protocol response.

Response generation

The SignInResponseGenerator class does the heavy lifting of creating the contents of the WS-Federation response:

• it calls the IdentityServer profile service to retrieve the configured claims for the relying party
• it tries to map the standard claim types to WS-* style claim types
• it creates the SAML 1.1/2.0 token
• it creates the RSTR (request security token response)

The outcome of these operations is a SignInResponseMessage object which then gets turned into a WS-Federation response and sent back to the relying party.

Configuration

For most parts, the WS-Federation endpoint can use the standard IdentityServer4 client configuration for relying parties. But there are also options available for setting WS-Federation specific options.

Defaults

You can configure global defaults in the WsFederationOptions class, e.g.:

• default token type (SAML 1.1 or SAML 2.0)
• default hashing and digest algorithms
• default SAML name identifier format
• default mappings from "short" claim types to WS-* claim types

Relying party configuration

The following client settings are used by the WS-Federation endpoint:

public static IEnumerable<Client> GetClients()
{
    return new[]
    {
        new Client
        {
            // realm identifier
            ClientId = "urn:owinrp",
            
            // must be set to WS-Federation
            ProtocolType = ProtocolTypes.WsFederation,

            // reply URL
            RedirectUris = { "http://localhost:10313/" },
            
            // signout cleanup url
            LogoutUri = "http://localhost:10313/home/signoutcleanup",
            
            // lifetime of SAML token
            IdentityTokenLifetime = 36000,

            // identity scopes - the associated claims will be used to call the profile service
            AllowedScopes = { "openid", "profile" }
        }
    };
}

WS-Federation specific relying party settings

If you want to deviate from the global defaults (e.g. set a different token type or claim mapping) for a specific relying party, you can define a RelyingParty object that uses the same realm name as the client ID used above.

This sample contains an in-memory relying party store that you can use to make these relying party specific settings available to the WS-Federation engine (using the AddInMemoryRelyingParty extension method). Otherwise, if you want to use your own store, you will need an implementation of IRelyingPartyStore.

Configuring IdentityServer

This repo contains an extension method for the IdentityServer builder object to register all the necessary services in DI, e.g.:

services.AddIdentityServer()
    .AddSigningCredential(cert)
    .AddInMemoryIdentityResources(Config.GetIdentityResources())
    .AddInMemoryApiResources(Config.GetApiResources())
    .AddInMemoryClients(Config.GetClients())
    .AddTestUsers(TestUsers.Users)
    .AddWsFederation()
    .AddInMemoryRelyingParties(Config.GetRelyingParties());

Connecting a relying party to the WS-Federation endpoint

Using Katana

Use the Katana WS-Federation middleware to point to the WS-Federation endpoint, e.g.:

public void Configuration(IAppBuilder app)
{
    app.UseCookieAuthentication(new CookieAuthenticationOptions
    {
        AuthenticationType = "Cookies"
    });

    app.UseWsFederationAuthentication(new WsFederationAuthenticationOptions
    {
        MetadataAddress = "http://localhost:5000/wsfederation",
        Wtrealm = "urn:owinrp",

        SignInAsAuthenticationType = "Cookies"
    });
}

SharePoint

see https://www.scottbrady91.com/Identity-Server/IdentityServer-4-SharePoint-Integration-using-WS-Federation