#776 Show some JwtBearer errors in response headers

src/Microsoft.AspNetCore.Authentication.JwtBearer/Events/JwtBearerChallengeContext.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Authentication;
@@ -16,5 +17,10 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         }
 
         public AuthenticationProperties Properties { get; }
+
+        /// <summary>
+        /// Any failures encountered during the authentication process.
+        /// </summary>
+        public Exception AuthenticateFailure { get; set; }
     }
 }

src/Microsoft.AspNetCore.Authentication.JwtBearer/JwtBearerHandler.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Security.Claims;
+using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
@@ -103,7 +104,8 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
                             Logger.TokenValidationFailed(token, ex);
 
                             // Refresh the configuration for exceptions that may be caused by key rollovers. The user can also request a refresh in the event.
-                            if (Options.RefreshOnIssuerKeyNotFound && ex.GetType().Equals(typeof(SecurityTokenSignatureKeyNotFoundException)))
+                            if (Options.RefreshOnIssuerKeyNotFound && Options.ConfigurationManager != null
+                                && ex is SecurityTokenSignatureKeyNotFoundException)
                             {
                                 Options.ConfigurationManager.RequestRefresh();
                             }
@@ -183,7 +185,12 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
         protected override async Task<bool> HandleUnauthorizedAsync(ChallengeContext context)
         {
-            var eventContext = new JwtBearerChallengeContext(Context, Options, new AuthenticationProperties(context.Properties));
+            var authResult = await HandleAuthenticateOnceAsync();
+
+            var eventContext = new JwtBearerChallengeContext(Context, Options, new AuthenticationProperties(context.Properties))
+            {
+                AuthenticateFailure = authResult?.Failure,
+            };
             await Options.Events.Challenge(eventContext);
             if (eventContext.HandledResponse)
             {
@@ -195,11 +202,94 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
             }
 
             Response.StatusCode = 401;
-            Response.Headers.Append(HeaderNames.WWWAuthenticate, Options.Challenge);
+
+            var errorDescription = CreateErrorDescription(eventContext.AuthenticateFailure);
+
+            if (errorDescription.Length == 0)
+            {
+                Response.Headers.Append(HeaderNames.WWWAuthenticate, Options.Challenge);
+            }
+            else
+            {
+                // https://tools.ietf.org/html/rfc6750#section-3.1
+                // WWW-Authenticate: Bearer realm="example", error="invalid_token", error_description="The access token expired"
+                var builder = new StringBuilder(Options.Challenge);
+                if (Options.Challenge.IndexOf(" ", StringComparison.Ordinal) > 0)
+                {
+                    // Only add a comma after the first param, if any
+                    builder.Append(',');
+                }
+                builder.Append(" error=\"invalid_token\", error_description=\"");
+                builder.Append(errorDescription);
+                builder.Append('\"');
+
+                Response.Headers.Append(HeaderNames.WWWAuthenticate, builder.ToString());
+            }
 
             return false;
         }
 
+        private static string CreateErrorDescription(Exception authFailure)
+        {
+            if (authFailure == null)
+            {
+                return string.Empty;
+            }
+
+            IEnumerable<Exception> exceptions;
+            if (authFailure is AggregateException)
+            {
+                var agEx = authFailure as AggregateException;
+                exceptions = agEx.InnerExceptions;
+            }
+            else
+            {
+                exceptions = new[] { authFailure };
+            }
+
+            var messages = new List<string>();
+
+            foreach (var ex in exceptions)
+            {
+                // Order sensitive, some of these exceptions derive from others
+                // and we want to display the most specific message possible.
+                if (ex is SecurityTokenInvalidAudienceException)
+                {
+                    messages.Add("The audience is invalid");
+                }
+                else if (ex is SecurityTokenInvalidIssuerException)
+                {
+                    messages.Add("The issuer is invalid");
+                }
+                else if (ex is SecurityTokenNoExpirationException)
+                {
+                    messages.Add("The token has no expiration");
+                }
+                else if (ex is SecurityTokenInvalidLifetimeException)
+                {
+                    messages.Add("The token lifetime is invalid");
+                }
+                else if (ex is SecurityTokenNotYetValidException)
+                {
+                    messages.Add("The token is not valid yet");
+                }
+                else if (ex is SecurityTokenExpiredException)
+                {
+                    messages.Add("The token is expired");
+                }
+                else if (ex is SecurityTokenSignatureKeyNotFoundException)
+                {
+                    messages.Add("The signature key was not found");
+                }
+                else if (ex is SecurityTokenInvalidSignatureException)
+                {
+                    messages.Add("The signature is invalid");
+                }
+            }
+
+            return string.Join("; ", messages);
+        }
+
         protected override Task HandleSignOutAsync(SignOutContext context)
         {
             throw new NotSupportedException();

src/Microsoft.AspNetCore.Authentication.OpenIdConnect/OpenIdConnectHandler.cs

@@ -575,7 +575,7 @@ namespace Microsoft.AspNetCore.Authentication.OpenIdConnect
                 Logger.ExceptionProcessingMessage(exception);
 
                 // Refresh the configuration for exceptions that may be caused by key rollovers. The user can also request a refresh in the event.
-                if (Options.RefreshOnIssuerKeyNotFound && exception.GetType().Equals(typeof(SecurityTokenSignatureKeyNotFoundException)))
+                if (Options.RefreshOnIssuerKeyNotFound && exception is SecurityTokenSignatureKeyNotFoundException)
                 {
                     if (Options.ConfigurationManager != null)
                     {

test/Microsoft.AspNetCore.Authentication.Test/JwtBearer/JwtBearerMiddlewareTests.cs

@@ -2,9 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
+using System.Linq;
 using System.Net;
 using System.Net.Http;
+using System.Reflection;
 using System.Security.Claims;
 using System.Threading.Tasks;
 using System.Xml.Linq;
@@ -30,7 +31,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var options = new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
                 Authority = "https://login.windows.net/tushartest.onmicrosoft.com",
                 Audience = "https://TusharTest.onmicrosoft.com/TodoListService-ManualJwt"
             };
@@ -45,10 +45,7 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         [Fact]
         public async Task SignInThrows()
         {
-            var server = CreateServer(new JwtBearerOptions
+            var server = CreateServer(new JwtBearerOptions());
-            {
-                AutomaticAuthenticate = true
-            });
             var transaction = await server.SendAsync("https://example.com/signIn");
             Assert.Equal(HttpStatusCode.OK, transaction.Response.StatusCode);
         }
@@ -56,10 +53,7 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         [Fact]
         public async Task SignOutThrows()
         {
-            var server = CreateServer(new JwtBearerOptions
+            var server = CreateServer(new JwtBearerOptions());
-            {
-                AutomaticAuthenticate = true
-            });
             var transaction = await server.SendAsync("https://example.com/signOut");
             Assert.Equal(HttpStatusCode.OK, transaction.Response.StatusCode);
         }
@@ -70,7 +64,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var server = CreateServer(new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
                 Events = new JwtBearerEvents()
                 {
                     OnMessageReceived = context =>
@@ -117,10 +110,7 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         [Fact]
         public async Task UnrecognizedTokenReceived()
         {
-            var server = CreateServer(new JwtBearerOptions
+            var server = CreateServer(new JwtBearerOptions());
-            {
-                AutomaticAuthenticate = true
-            });
 
             var response = await SendAsync(server, "http://example.com/oauth", "Bearer someblob");
             Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
@@ -130,16 +120,67 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         [Fact]
         public async Task InvalidTokenReceived()
         {
-            var options = new JwtBearerOptions
+            var options = new JwtBearerOptions();
-            {
-                AutomaticAuthenticate = true
-            };
             options.SecurityTokenValidators.Clear();
             options.SecurityTokenValidators.Add(new InvalidTokenValidator());
             var server = CreateServer(options);
 
             var response = await SendAsync(server, "http://example.com/oauth", "Bearer someblob");
             Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
+            Assert.Equal("Bearer", response.Response.Headers.WwwAuthenticate.First().ToString());
+            Assert.Equal("", response.ResponseText);
+        }
+
+        [Theory]
+        [InlineData(typeof(SecurityTokenInvalidAudienceException), "The audience is invalid")]
+        [InlineData(typeof(SecurityTokenInvalidIssuerException), "The issuer is invalid")]
+        [InlineData(typeof(SecurityTokenNoExpirationException), "The token has no expiration")]
+        [InlineData(typeof(SecurityTokenInvalidLifetimeException), "The token lifetime is invalid")]
+        [InlineData(typeof(SecurityTokenNotYetValidException), "The token is not valid yet")]
+        [InlineData(typeof(SecurityTokenExpiredException), "The token is expired")]
+        [InlineData(typeof(SecurityTokenInvalidSignatureException), "The signature is invalid")]
+        [InlineData(typeof(SecurityTokenSignatureKeyNotFoundException), "The signature key was not found")]
+        public async Task ExceptionReportedInHeaderForAuthenticationFailures(Type errorType, string message)
+        {
+            var options = new JwtBearerOptions();
+            options.SecurityTokenValidators.Clear();
+            options.SecurityTokenValidators.Add(new InvalidTokenValidator(errorType));
+            var server = CreateServer(options);
+
+            var response = await SendAsync(server, "http://example.com/oauth", "Bearer someblob");
+            Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
+            Assert.Equal($"Bearer error=\"invalid_token\", error_description=\"{message}\"", response.Response.Headers.WwwAuthenticate.First().ToString());
+            Assert.Equal("", response.ResponseText);
+        }
+
+        [Theory]
+        [InlineData(typeof(ArgumentException))]
+        public async Task ExceptionNotReportedInHeaderForOtherFailures(Type errorType)
+        {
+            var options = new JwtBearerOptions();
+            options.SecurityTokenValidators.Clear();
+            options.SecurityTokenValidators.Add(new InvalidTokenValidator(errorType));
+            var server = CreateServer(options);
+
+            var response = await SendAsync(server, "http://example.com/oauth", "Bearer someblob");
+            Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
+            Assert.Equal("Bearer", response.Response.Headers.WwwAuthenticate.First().ToString());
+            Assert.Equal("", response.ResponseText);
+        }
+
+        [Fact]
+        public async Task ExceptionsReportedInHeaderForMultipleAuthenticationFailures()
+        {
+            var options = new JwtBearerOptions();
+            options.SecurityTokenValidators.Clear();
+            options.SecurityTokenValidators.Add(new InvalidTokenValidator(typeof(SecurityTokenInvalidAudienceException)));
+            options.SecurityTokenValidators.Add(new InvalidTokenValidator(typeof(SecurityTokenSignatureKeyNotFoundException)));
+            var server = CreateServer(options);
+
+            var response = await SendAsync(server, "http://example.com/oauth", "Bearer someblob");
+            Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
+            Assert.Equal($"Bearer error=\"invalid_token\", error_description=\"The audience is invalid; The signature key was not found\"",
+                response.Response.Headers.WwwAuthenticate.First().ToString());
             Assert.Equal("", response.ResponseText);
         }
 
@@ -148,7 +189,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var options = new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
                 Events = new JwtBearerEvents()
                 {
                     OnTokenValidated = context =>
@@ -185,7 +225,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var options = new JwtBearerOptions()
             {
-                AutomaticAuthenticate = true,
                 Events = new JwtBearerEvents()
                 {
                     OnMessageReceived = context =>
@@ -233,7 +272,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var server = CreateServer(new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
                 Events = new JwtBearerEvents()
                 {
                     OnMessageReceived = context =>
@@ -266,7 +304,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var options = new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
                 Events = new JwtBearerEvents()
                 {
                     OnTokenValidated = context =>
@@ -298,7 +335,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var options = new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
                 Events = new JwtBearerEvents()
                 {
                     OnTokenValidated = context =>
@@ -330,8 +366,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             var server = CreateServer(new JwtBearerOptions
             {
-                AutomaticAuthenticate = true,
-                AutomaticChallenge = true,
                 Events = new JwtBearerEvents()
                 {
                     OnChallenge = context =>
@@ -352,8 +386,16 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         {
             public InvalidTokenValidator()
             {
+                ExceptionType = typeof(SecurityTokenException);
             }
 
+            public InvalidTokenValidator(Type exceptionType)
+            {
+                ExceptionType = exceptionType;
+            }
+
+            public Type ExceptionType { get; set; }
+
             public bool CanValidateToken => true;
 
             public int MaximumTokenSizeInBytes
@@ -366,7 +408,9 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
             public ClaimsPrincipal ValidateToken(string securityToken, TokenValidationParameters validationParameters, out SecurityToken validatedToken)
             {
-                throw new SecurityTokenException("InvalidToken");
+                var constructor = ExceptionType.GetTypeInfo().GetConstructor(new[] { typeof(string) });
+                var exception = (Exception)constructor.Invoke(new[] { ExceptionType.Name });
+                throw exception;
             }
         }