more references.

Quickstart/Account/ExternalController.cs

@@ -0,0 +1,196 @@
+using IdentityModel;
+using IdentityServer4;
+using IdentityServer4.Events;
+using IdentityServer4.Services;
+using IdentityServer4.Stores;
+using IdentityServer4.Test;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Logging;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Claims;
+using System.Threading.Tasks;
+
+namespace IdentityServerHost.Quickstart.UI
+{
+    [SecurityHeaders]
+    [AllowAnonymous]
+    public class ExternalController : Controller
+    {
+        private readonly TestUserStore _users;
+        private readonly IIdentityServerInteractionService _interaction;
+        private readonly IClientStore _clientStore;
+        private readonly ILogger<ExternalController> _logger;
+        private readonly IEventService _events;
+
+        public ExternalController(
+            IIdentityServerInteractionService interaction,
+            IClientStore clientStore,
+            IEventService events,
+            ILogger<ExternalController> logger,
+            TestUserStore users = null)
+        {
+            // if the TestUserStore is not in DI, then we'll just use the global users collection
+            // this is where you would plug in your own custom identity management library (e.g. ASP.NET Identity)
+            _users = users ?? new TestUserStore(TestUsers.Users);
+
+            _interaction = interaction;
+            _clientStore = clientStore;
+            _logger = logger;
+            _events = events;
+        }
+
+        /// <summary>
+        /// initiate roundtrip to external authentication provider
+        /// </summary>
+        [HttpGet]
+        public IActionResult Challenge(string scheme, string returnUrl)
+        {
+            if (string.IsNullOrEmpty(returnUrl)) returnUrl = "~/";
+
+            // validate returnUrl - either it is a valid OIDC URL or back to a local page
+            if (Url.IsLocalUrl(returnUrl) == false && _interaction.IsValidReturnUrl(returnUrl) == false)
+            {
+                // user might have clicked on a malicious link - should be logged
+                throw new Exception("invalid return URL");
+            }
+            
+            // start challenge and roundtrip the return URL and scheme 
+            var props = new AuthenticationProperties
+            {
+                RedirectUri = Url.Action(nameof(Callback)), 
+                Items =
+                {
+                    { "returnUrl", returnUrl }, 
+                    { "scheme", scheme },
+                }
+            };
+
+            return Challenge(props, scheme);
+            
+        }
+
+        /// <summary>
+        /// Post processing of external authentication
+        /// </summary>
+        [HttpGet]
+        public async Task<IActionResult> Callback()
+        {
+            // read external identity from the temporary cookie
+            var result = await HttpContext.AuthenticateAsync(IdentityServerConstants.ExternalCookieAuthenticationScheme);
+            if (result?.Succeeded != true)
+            {
+                throw new Exception("External authentication error");
+            }
+
+            if (_logger.IsEnabled(LogLevel.Debug))
+            {
+                var externalClaims = result.Principal.Claims.Select(c => $"{c.Type}: {c.Value}");
+                _logger.LogDebug("External claims: {@claims}", externalClaims);
+            }
+
+            // lookup our user and external provider info
+            var (user, provider, providerUserId, claims) = FindUserFromExternalProvider(result);
+            if (user == null)
+            {
+                // this might be where you might initiate a custom workflow for user registration
+                // in this sample we don't show how that would be done, as our sample implementation
+                // simply auto-provisions new external user
+                user = AutoProvisionUser(provider, providerUserId, claims);
+            }
+
+            // this allows us to collect any additional claims or properties
+            // for the specific protocols used and store them in the local auth cookie.
+            // this is typically used to store data needed for signout from those protocols.
+            var additionalLocalClaims = new List<Claim>();
+            var localSignInProps = new AuthenticationProperties();
+            ProcessLoginCallback(result, additionalLocalClaims, localSignInProps);
+            
+            // issue authentication cookie for user
+            var isuser = new IdentityServerUser(user.SubjectId)
+            {
+                DisplayName = user.Username,
+                IdentityProvider = provider,
+                AdditionalClaims = additionalLocalClaims
+            };
+
+            await HttpContext.SignInAsync(isuser, localSignInProps);
+
+            // delete temporary cookie used during external authentication
+            await HttpContext.SignOutAsync(IdentityServerConstants.ExternalCookieAuthenticationScheme);
+
+            // retrieve return URL
+            var returnUrl = result.Properties.Items["returnUrl"] ?? "~/";
+
+            // check if external login is in the context of an OIDC request
+            var context = await _interaction.GetAuthorizationContextAsync(returnUrl);
+            await _events.RaiseAsync(new UserLoginSuccessEvent(provider, providerUserId, user.SubjectId, user.Username, true, context?.Client.ClientId));
+
+            if (context != null)
+            {
+                if (context.IsNativeClient())
+                {
+                    // The client is native, so this change in how to
+                    // return the response is for better UX for the end user.
+                    return this.LoadingPage("Redirect", returnUrl);
+                }
+            }
+
+            return Redirect(returnUrl);
+        }
+
+        private (TestUser user, string provider, string providerUserId, IEnumerable<Claim> claims) FindUserFromExternalProvider(AuthenticateResult result)
+        {
+            var externalUser = result.Principal;
+
+            // try to determine the unique id of the external user (issued by the provider)
+            // the most common claim type for that are the sub claim and the NameIdentifier
+            // depending on the external provider, some other claim type might be used
+            var userIdClaim = externalUser.FindFirst(JwtClaimTypes.Subject) ??
+                              externalUser.FindFirst(ClaimTypes.NameIdentifier) ??
+                              throw new Exception("Unknown userid");
+
+            // remove the user id claim so we don't include it as an extra claim if/when we provision the user
+            var claims = externalUser.Claims.ToList();
+            claims.Remove(userIdClaim);
+
+            var provider = result.Properties.Items["scheme"];
+            var providerUserId = userIdClaim.Value;
+
+            // find external user
+            var user = _users.FindByExternalProvider(provider, providerUserId);
+
+            return (user, provider, providerUserId, claims);
+        }
+
+        private TestUser AutoProvisionUser(string provider, string providerUserId, IEnumerable<Claim> claims)
+        {
+            var user = _users.AutoProvisionUser(provider, providerUserId, claims.ToList());
+            return user;
+        }
+
+        // if the external login is OIDC-based, there are certain things we need to preserve to make logout work
+        // this will be different for WS-Fed, SAML2p or other protocols
+        private void ProcessLoginCallback(AuthenticateResult externalResult, List<Claim> localClaims, AuthenticationProperties localSignInProps)
+        {
+            // if the external system sent a session id claim, copy it over
+            // so we can use it for single sign-out
+            var sid = externalResult.Principal.Claims.FirstOrDefault(x => x.Type == JwtClaimTypes.SessionId);
+            if (sid != null)
+            {
+                localClaims.Add(new Claim(JwtClaimTypes.SessionId, sid.Value));
+            }
+
+            // if the external provider issued an id_token, we'll keep it for signout
+            var idToken = externalResult.Properties.GetTokenValue("id_token");
+            if (idToken != null)
+            {
+                localSignInProps.StoreTokens(new[] { new AuthenticationToken { Name = "id_token", Value = idToken } });
+            }
+        }
+    }
+}