Return the auth challenge in the WWW-Authenticate when auth fails

src/Ocelot/Authentication/Middleware/AuthenticationMiddleware.cs

@@ -36,6 +36,7 @@ public async Task Invoke(HttpContext httpContext)
 
             if (result.Principal?.Identity == null)
             {
+                await ChallengeAsync(httpContext, downstreamRoute, result);
                 SetUnauthenticatedError(httpContext, path, null);
                 return;
             }
@@ -49,6 +50,7 @@ public async Task Invoke(HttpContext httpContext)
                 return;
             }
 
+            await ChallengeAsync(httpContext, downstreamRoute, result);
             SetUnauthenticatedError(httpContext, path, httpContext.User.Identity.Name);
         }
 
@@ -59,6 +61,18 @@ private void SetUnauthenticatedError(HttpContext httpContext, string path, strin
             httpContext.Items.SetError(error);
         }
 
+        private async Task ChallengeAsync(HttpContext context, DownstreamRoute route, AuthenticateResult status)
+        {
+            // Perform a challenge. This populates the WWW-Authenticate header on the response
+            await context.ChallengeAsync(route.AuthenticationOptions.AuthenticationProviderKey); // TODO Read failed scheme from auth result
+
+            // Since the response gets re-created down the pipeline, we store the challenge in the Items, so we can re-apply it when sending the response
+            if (context.Response.Headers.TryGetValue("WWW-Authenticate", out var authenticateHeader))
+            {
+                context.Items.SetAuthChallenge(authenticateHeader);
+            }
+        }
+
         private async Task<AuthenticateResult> AuthenticateAsync(HttpContext context, DownstreamRoute route)
         {
             var options = route.AuthenticationOptions;

src/Ocelot/Middleware/HttpItemsExtensions.cs

@@ -43,6 +43,12 @@ public static void SetError(this IDictionary<object, object> input, Error error)
             input.Upsert("Errors", errors);
         }
 
+        public static void SetAuthChallenge(this IDictionary<object, object> input, string challengeString) =>
+            input.Upsert("AuthChallenge", challengeString);
+
+        public static string AuthChallenge(this IDictionary<object, object> input) =>
+            input.Get<string>("AuthChallenge");
+
         public static void SetIInternalConfiguration(this IDictionary<object, object> input, IInternalConfiguration config)
         {
             input.Upsert("IInternalConfiguration", config);

src/Ocelot/Multiplexer/MultiplexingMiddleware.cs

@@ -1,22 +1,22 @@
-using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Primitives;
 using Newtonsoft.Json.Linq;
-using Ocelot.Configuration;
+using Ocelot.Configuration;
 using Ocelot.Configuration.File;
-using Ocelot.DownstreamRouteFinder.UrlMatcher;
-using Ocelot.Logging;
-using Ocelot.Middleware;
+using Ocelot.DownstreamRouteFinder.UrlMatcher;
+using Ocelot.Logging;
+using Ocelot.Middleware;
 using System.Collections;
 using Route = Ocelot.Configuration.Route;
-
+
 namespace Ocelot.Multiplexer;
 
 public class MultiplexingMiddleware : OcelotMiddleware
 {
     private readonly RequestDelegate _next;
     private readonly IResponseAggregatorFactory _factory;
     private const string RequestIdString = "RequestId";
-
+
     public MultiplexingMiddleware(RequestDelegate next,
         IOcelotLoggerFactory loggerFactory,
         IResponseAggregatorFactory factory)
@@ -25,7 +25,7 @@ public MultiplexingMiddleware(RequestDelegate next,
         _factory = factory;
         _next = next;
     }
-
+
     public async Task Invoke(HttpContext httpContext)
     {
         var downstreamRouteHolder = httpContext.Items.DownstreamRouteHolder();
@@ -38,37 +38,37 @@ public async Task Invoke(HttpContext httpContext)
             await ProcessSingleRouteAsync(httpContext, downstreamRoutes[0]);
             return;
         }
-
+
         // Case 2: if no downstream routes
         if (downstreamRoutes.Count == 0)
         {
             return;
         }
-
+
         // Case 3: if multiple downstream routes
         var routeKeysConfigs = route.DownstreamRouteConfig;
         if (routeKeysConfigs == null || routeKeysConfigs.Count == 0)
         {
             await ProcessRoutesAsync(httpContext, route);
             return;
         }
-
+
         // Case 4: if multiple downstream routes with route keys
         var mainResponseContext = await ProcessMainRouteAsync(httpContext, downstreamRoutes[0]);
         if (mainResponseContext == null)
         {
             return;
         }
-
+
         var responsesContexts = await ProcessRoutesWithRouteKeysAsync(httpContext, downstreamRoutes, routeKeysConfigs, mainResponseContext);
         if (responsesContexts.Length == 0)
         {
             return;
         }
-
+
         await MapResponsesAsync(httpContext, route, mainResponseContext, responsesContexts);
     }
-
+
     /// <summary>
     /// Helper method to determine if only the first downstream route should be processed.
     /// It is the case if the request is a websocket request or if there is only one downstream route.
@@ -78,7 +78,7 @@ public async Task Invoke(HttpContext httpContext)
     /// <returns>True if only the first downstream route should be processed.</returns>
     private static bool ShouldProcessSingleRoute(HttpContext context, ICollection routes)
         => context.WebSockets.IsWebSocketRequest || routes.Count == 1;
-
+
     /// <summary>
     /// Processing a single downstream route (no route keys).
     /// In that case, no need to make copies of the http context.
@@ -89,9 +89,10 @@ private static bool ShouldProcessSingleRoute(HttpContext context, ICollection ro
     protected virtual Task ProcessSingleRouteAsync(HttpContext context, DownstreamRoute route)
     {
         context.Items.UpsertDownstreamRoute(route);
+        context.Items.SetAuthChallenge(/*finished*/context.Items.AuthChallenge());
         return _next.Invoke(context);
     }
-
+
     /// <summary>
     /// Processing the downstream routes (no route keys).
     /// </summary>
@@ -105,7 +106,7 @@ private async Task ProcessRoutesAsync(HttpContext context, Route route)
         var contexts = await Task.WhenAll(tasks);
         await MapAsync(context, route, new(contexts));
     }
-
+
     /// <summary>
     /// When using route keys, the first route is the main route and the rest are additional routes.
     /// Since we need to break if the main route response is null, we must process the main route first.
@@ -119,7 +120,7 @@ private async Task<HttpContext> ProcessMainRouteAsync(HttpContext context, Downs
         await _next.Invoke(context);
         return context;
     }
-
+
     /// <summary>
     /// Processing the downstream routes with route keys except the main route that has already been processed.
     /// </summary>
@@ -133,7 +134,7 @@ protected virtual async Task<HttpContext[]> ProcessRoutesWithRouteKeysAsync(Http
         var processing = new List<Task<HttpContext>>();
         var content = await mainResponse.Items.DownstreamResponse().Content.ReadAsStringAsync();
         var jObject = JToken.Parse(content);
-
+
         foreach (var downstreamRoute in routes.Skip(1))
         {
             var matchAdvancedAgg = routeKeysConfigs.FirstOrDefault(q => q.RouteKey == downstreamRoute.Key);
@@ -142,13 +143,13 @@ protected virtual async Task<HttpContext[]> ProcessRoutesWithRouteKeysAsync(Http
                 processing.AddRange(ProcessRouteWithComplexAggregation(matchAdvancedAgg, jObject, context, downstreamRoute));
                 continue;
             }
-
+
             processing.Add(ProcessRouteAsync(context, downstreamRoute));
         }
-
+
         return await Task.WhenAll(processing);
     }
-
+
     /// <summary>
     /// Mapping responses.
     /// </summary>
@@ -158,7 +159,7 @@ private Task MapResponsesAsync(HttpContext context, Route route, HttpContext mai
         contexts.AddRange(responsesContexts);
         return MapAsync(context, route, contexts);
     }
-
+
     /// <summary>
     /// Processing a route with aggregation.
     /// </summary>
@@ -173,7 +174,7 @@ private IEnumerable<Task<HttpContext>> ProcessRouteWithComplexAggregation(Aggreg
             tPnv.Add(new PlaceholderNameAndValue('{' + matchAdvancedAgg.Parameter + '}', value));
             processing.Add(ProcessRouteAsync(httpContext, downstreamRoute, tPnv));
         }
-
+
         return processing;
     }
 
@@ -186,11 +187,11 @@ private async Task<HttpContext> ProcessRouteAsync(HttpContext sourceContext, Dow
         var newHttpContext = await CreateThreadContextAsync(sourceContext, route);
         CopyItemsToNewContext(newHttpContext, sourceContext, placeholders);
         newHttpContext.Items.UpsertDownstreamRoute(route);
-
+
         await _next.Invoke(newHttpContext);
         return newHttpContext;
     }
-
+
     /// <summary>
     /// Copying some needed parameters to the Http context items.
     /// </summary>
@@ -247,7 +248,7 @@ protected virtual async Task<HttpContext> CreateThreadContextAsync(HttpContext s
         target.Response.RegisterForDisposeAsync(bodyStream); // manage Stream lifetime by HttpResponse object
         return target;
     }
-
+
     protected virtual Task MapAsync(HttpContext httpContext, Route route, List<HttpContext> contexts)
     {
         if (route.DownstreamRoute.Count == 1)
@@ -282,4 +283,4 @@ protected virtual async Task<Stream> CloneRequestBodyAsync(HttpRequest request,
 
         return targetBuffer;
     }
-}
+}

src/Ocelot/Responder/HttpContextResponder.cs

@@ -77,6 +77,9 @@ public async Task SetErrorResponseOnContext(HttpContext context, DownstreamRespo
         }
     }
 
+    public void SetAuthChallengeOnContext(HttpContext context, string challenge)
+        => AddHeaderIfDoesntExist(context, new Header("WWW-Authenticate", new[] { challenge }));
+
     private static void SetStatusCode(HttpContext context, int statusCode)
     {
         if (!context.Response.HasStarted)

src/Ocelot/Responder/IHttpResponder.cs

@@ -1,6 +1,6 @@
 using Microsoft.AspNetCore.Http;
 using Ocelot.Middleware;
-
+
 namespace Ocelot.Responder
 {
     public interface IHttpResponder
@@ -10,5 +10,7 @@ public interface IHttpResponder
         void SetErrorResponseOnContext(HttpContext context, int statusCode);
 
         Task SetErrorResponseOnContext(HttpContext context, DownstreamResponse response);
+
+        void SetAuthChallengeOnContext(HttpContext context, string challenge);
     }
 }

src/Ocelot/Responder/Middleware/ResponderMiddleware.cs

@@ -61,13 +61,20 @@ private async Task SetErrorResponse(HttpContext context, List<Error> errors)
             var statusCode = _codeMapper.Map(errors);
             _responder.SetErrorResponseOnContext(context, statusCode);
 
-            if (errors.All(e => e.Code != OcelotErrorCode.QuotaExceededError))
+            if (errors.Any(e => e.Code == OcelotErrorCode.QuotaExceededError))
             {
-                return;
+                var downstreamResponse = context.Items.DownstreamResponse();
+                await _responder.SetErrorResponseOnContext(context, downstreamResponse);
             }
 
-            var downstreamResponse = context.Items.DownstreamResponse();
-            await _responder.SetErrorResponseOnContext(context, downstreamResponse);
+            if (errors.Any(e => e.Code == OcelotErrorCode.UnauthenticatedError))
+            {
+                var challenge = context.Items.AuthChallenge();
+                if (!string.IsNullOrEmpty(challenge))
+                {
+                    _responder.SetAuthChallengeOnContext(context, challenge);
+                }
+            }
         }
     }
 }

test/Ocelot.AcceptanceTests/Authentication/AuthenticationTests.cs

@@ -2,6 +2,8 @@
 using IdentityServer4.Models;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Ocelot.DependencyInjection;
 
 namespace Ocelot.AcceptanceTests.Authentication
 {
@@ -112,6 +114,40 @@ public void Should_return_201_using_identity_server_reference_token()
                 .BDDfy();
         }
 
+        [Fact]
+        [Trait("Feat", "1387")]
+        public void Should_return_www_authenticate_header_on_401()
+        {
+            var port = PortFinder.GetRandomPort();
+            var route = GivenDefaultAuthRoute(port);
+            var configuration = GivenConfiguration(route);
+            this.Given(x => GivenThereIsAConfiguration(configuration))
+                .And(x => GivenOcelotIsRunningWithJwtAuth("Test"))
+                .And(x => GivenIHaveNoTokenForMyRequest())
+                .When(x => WhenIGetUrlOnTheApiGateway("/"))
+                .Then(x => ThenTheStatusCodeShouldBe(HttpStatusCode.Unauthorized))
+                .And(x => ThenTheResponseShouldContainAuthChallenge())
+                .BDDfy();
+        }
+        private void GivenOcelotIsRunningWithJwtAuth(string authenticationProviderKey)
+        {
+            GivenOcelotIsRunningWithServices(WithJwtBearer);
+            void WithJwtBearer(IServiceCollection s)
+            {
+                s.AddAuthentication().AddJwtBearer(authenticationProviderKey, options => { });
+                s.AddOcelot();
+            }
+        }
+        private void GivenIHaveNoTokenForMyRequest()
+        {
+            _ocelotClient.DefaultRequestHeaders.Authorization = null;
+        }
+        private void ThenTheResponseShouldContainAuthChallenge()
+        {
+            _response.Headers.TryGetValues("WWW-Authenticate", out var headerValue).ShouldBeTrue();
+            headerValue.ShouldNotBeEmpty();
+        }
+
         [IgnorePublicMethod]
         public async Task GivenThereIsAnIdentityServerOn(string url, AccessTokenType tokenType)
         {