IdentityServer4-I- Basic Setup for ASP.NET WEB API Project

 1. Create a new ASP.NET WEB API Project

2. Add the IdentityServer4 package from nuget. 

3.  Add the following in startup.cs

        public void ConfigureServices(IServiceCollection services)

        {

            services.AddControllers();

            services.AddIdentityServer()

                .AddInMemoryClients(new List<Client>())

                .AddInMemoryIdentityResources(new List<IdentityResource>())

                .AddInMemoryApiResources(new List<ApiResource>())

                .AddInMemoryApiScopes(new List<ApiScope>())

                .AddTestUsers(new List<TestUser>())

                .AddDeveloperSigningCredential();

        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)

        {

            if (env.IsDevelopment())

            {

                app.UseDeveloperExceptionPage();

            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>

            {

                endpoints.MapControllers();

            });

            app.UseIdentityServer();

        }

4. Run the web api. 

5. Assuming the development server hosts the wep api on the url https://localhost:44327, 

browse to the endpoint https://localhost:44327/.well-known/openid-configuration

You should get the following response: 

The same response if seen through POSTMAN (GET request) looks like:
{
    "issuer": "https://localhost:44327",
    "jwks_uri": "https://localhost:44327/.well-known/openid-configuration/jwks",
    "authorization_endpoint": "https://localhost:44327/connect/authorize",
    "token_endpoint": "https://localhost:44327/connect/token",
    "userinfo_endpoint": "https://localhost:44327/connect/userinfo",
    "end_session_endpoint": "https://localhost:44327/connect/endsession",
    "check_session_iframe": "https://localhost:44327/connect/checksession",
    "revocation_endpoint": "https://localhost:44327/connect/revocation",
    "introspection_endpoint": "https://localhost:44327/connect/introspect",
    "device_authorization_endpoint": "https://localhost:44327/connect/deviceauthorization",
    "frontchannel_logout_supported": true,
    "frontchannel_logout_session_supported": true,
    "backchannel_logout_supported": true,
    "backchannel_logout_session_supported": true,
    "scopes_supported": [
        "openid",
        "profile",
        "offline_access"
    ],
    "claims_supported": [
        "sub",
        "name",
        "family_name",
        "given_name",
        "middle_name",
        "nickname",
        "preferred_username",
        "profile",
        "picture",
        "website",
        "gender",
        "birthdate",
        "zoneinfo",
        "locale",
        "updated_at"
    ],
    "grant_types_supported": [
        "authorization_code",
        "client_credentials",
        "refresh_token",
        "implicit",
        "password",
        "urn:ietf:params:oauth:grant-type:device_code"
    ],
    "response_types_supported": [
        "code",
        "token",
        "id_token",
        "id_token token",
        "code id_token",
        "code token",
        "code id_token token"
    ],
    "response_modes_supported": [
        "form_post",
        "query",
        "fragment"
    ],
    "token_endpoint_auth_methods_supported": [
        "client_secret_basic",
        "client_secret_post"
    ],
    "id_token_signing_alg_values_supported": [
        "RS256"
    ],
    "subject_types_supported": [
        "public"
    ],
    "code_challenge_methods_supported": [
        "plain",
        "S256"
    ],
    "request_parameter_supported": true
}

You can also try /connect/token endpoint which is actually a POST endpoint with many parameters, but you should get Invalid Request indicating that the server is running.

For rest of the endpoints /connect/authorize, /connect/introspect we need to add client, user , identity and api resources which we will see in the next post.