Add a new IncludeErrorDetails option to prevent the JWT middleware from returning error/error_description

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

@@ -22,5 +22,25 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
         /// Any failures encountered during the authentication process.
         /// </summary>
         public Exception AuthenticateFailure { get; set; }
+
+        /// <summary>
+        /// Gets or sets the "error" value returned to the caller as part
+        /// of the WWW-Authenticate header. This property may be null when
+        /// <see cref="JwtBearerOptions.IncludeErrorDetails"/> is set to <c>false</c>.
+        /// </summary>
+        public string Error { get; set; }
+
+        /// <summary>
+        /// Gets or sets the "error_description" value returned to the caller as part
+        /// of the WWW-Authenticate header. This property may be null when
+        /// <see cref="JwtBearerOptions.IncludeErrorDetails"/> is set to <c>false</c>.
+        /// </summary>
+        public string ErrorDescription { get; set; }
+
+        /// <summary>
+        /// Gets or sets the "error_uri" value returned to the caller as part of the
+        /// WWW-Authenticate header. This property is always null unless explicitly set.
+        /// </summary>
+        public string ErrorUri { get; set; }
     }
 }

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

@@ -191,6 +191,14 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
             {
                 AuthenticateFailure = authResult?.Failure,
             };
+
+            // Avoid returning error=invalid_token if the error is not caused by an authentication failure (e.g missing token).
+            if (Options.IncludeErrorDetails && eventContext.AuthenticateFailure != null)
+            {
+                eventContext.Error = "invalid_token";
+                eventContext.ErrorDescription = CreateErrorDescription(eventContext.AuthenticateFailure);
+            }
+
             await Options.Events.Challenge(eventContext);
             if (eventContext.HandledResponse)
             {
@@ -203,9 +211,9 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
             Response.StatusCode = 401;
 
-            var errorDescription = CreateErrorDescription(eventContext.AuthenticateFailure);
+            if (string.IsNullOrEmpty(eventContext.Error) &&
-
+                string.IsNullOrEmpty(eventContext.ErrorDescription) &&
-            if (errorDescription.Length == 0)
+                string.IsNullOrEmpty(eventContext.ErrorUri))
             {
                 Response.Headers.Append(HeaderNames.WWWAuthenticate, Options.Challenge);
             }
@@ -219,9 +227,35 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
                     // Only add a comma after the first param, if any
                     builder.Append(',');
                 }
-                builder.Append(" error=\"invalid_token\", error_description=\"");
+                if (!string.IsNullOrEmpty(eventContext.Error))
-                builder.Append(errorDescription);
+                {
-                builder.Append('\"');
+                    builder.Append(" error=\"");
+                    builder.Append(eventContext.Error);
+                    builder.Append("\"");
+                }
+                if (!string.IsNullOrEmpty(eventContext.ErrorDescription))
+                {
+                    if (!string.IsNullOrEmpty(eventContext.Error))
+                    {
+                        builder.Append(",");
+                    }
+
+                    builder.Append(" error_description=\"");
+                    builder.Append(eventContext.ErrorDescription);
+                    builder.Append('\"');
+                }
+                if (!string.IsNullOrEmpty(eventContext.ErrorUri))
+                {
+                    if (!string.IsNullOrEmpty(eventContext.Error) ||
+                        !string.IsNullOrEmpty(eventContext.ErrorDescription))
+                    {
+                        builder.Append(",");
+                    }
+
+                    builder.Append(" error_uri=\"");
+                    builder.Append(eventContext.ErrorUri);
+                    builder.Append('\"');
+                }
 
                 Response.Headers.Append(HeaderNames.WWWAuthenticate, builder.ToString());
             }
@@ -231,11 +265,6 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
         private static string CreateErrorDescription(Exception authFailure)
         {
-            if (authFailure == null)
-            {
-                return string.Empty;
-            }
-
             IEnumerable<Exception> exceptions;
             if (authFailure is AggregateException)
             {

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

@@ -118,5 +118,12 @@ namespace Microsoft.AspNetCore.Builder
         /// <see cref="Http.Authentication.AuthenticationProperties"/> after a successful authorization.
         /// </summary>
         public bool SaveToken { get; set; } = true;
+
+        /// <summary>
+        /// Defines whether the token validation errors should be returned to the caller.
+        /// Enabled by default, this option can be disabled to prevent the JWT middleware
+        /// from returning an error and an error_description in the WWW-Authenticate header.
+        /// </summary>
+        public bool IncludeErrorDetails { get; set; } = true;
     }
 }

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

@@ -7,6 +7,7 @@ using System.Net;
 using System.Net.Http;
 using System.Reflection;
 using System.Security.Claims;
+using System.Text;
 using System.Threading.Tasks;
 using System.Xml.Linq;
 using Microsoft.AspNetCore.Builder;
@@ -127,7 +128,7 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
             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("Bearer error=\"invalid_token\"", response.Response.Headers.WwwAuthenticate.First().ToString());
             Assert.Equal("", response.ResponseText);
         }
 
@@ -164,7 +165,7 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
             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("Bearer error=\"invalid_token\"", response.Response.Headers.WwwAuthenticate.First().ToString());
             Assert.Equal("", response.ResponseText);
         }
 
@@ -179,11 +180,100 @@ namespace Microsoft.AspNetCore.Authentication.JwtBearer
 
             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\"",
+            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);
         }
 
+        [Theory]
+        [InlineData("custom_error", "custom_description", "custom_uri")]
+        [InlineData("custom_error", "custom_description", null)]
+        [InlineData("custom_error", null, null)]
+        [InlineData(null, "custom_description", "custom_uri")]
+        [InlineData(null, "custom_description", null)]
+        [InlineData(null, null, "custom_uri")]
+        public async Task ExceptionsReportedInHeaderExposesUserDefinedError(string error, string description, string uri)
+        {
+            var options = new JwtBearerOptions
+            {
+                Events = new JwtBearerEvents
+                {
+                    OnChallenge = context =>
+                    {
+                        context.Error = error;
+                        context.ErrorDescription = description;
+                        context.ErrorUri = uri;
+
+                        return Task.FromResult(0);
+                    }
+                }
+            };
+            var server = CreateServer(options);
+
+            var response = await SendAsync(server, "http://example.com/oauth", "Bearer someblob");
+            Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
+            Assert.Equal("", response.ResponseText);
+
+            var builder = new StringBuilder(options.Challenge);
+
+            if (!string.IsNullOrEmpty(error))
+            {
+                builder.Append(" error=\"");
+                builder.Append(error);
+                builder.Append("\"");
+            }
+            if (!string.IsNullOrEmpty(description))
+            {
+                if (!string.IsNullOrEmpty(error))
+                {
+                    builder.Append(",");
+                }
+
+                builder.Append(" error_description=\"");
+                builder.Append(description);
+                builder.Append('\"');
+            }
+            if (!string.IsNullOrEmpty(uri))
+            {
+                if (!string.IsNullOrEmpty(error) ||
+                    !string.IsNullOrEmpty(description))
+                {
+                    builder.Append(",");
+                }
+
+                builder.Append(" error_uri=\"");
+                builder.Append(uri);
+                builder.Append('\"');
+            }
+
+            Assert.Equal(builder.ToString(), response.Response.Headers.WwwAuthenticate.First().ToString());
+        }
+
+        [Fact]
+        public async Task ExceptionNotReportedInHeaderWhenIncludeErrorDetailsIsFalse()
+        {
+            var server = CreateServer(new JwtBearerOptions
+            {
+                IncludeErrorDetails = false
+            });
+
+            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 ExceptionNotReportedInHeaderWhenTokenWasMissing()
+        {
+            var server = CreateServer(new JwtBearerOptions());
+
+            var response = await SendAsync(server, "http://example.com/oauth");
+            Assert.Equal(HttpStatusCode.Unauthorized, response.Response.StatusCode);
+            Assert.Equal("Bearer", response.Response.Headers.WwwAuthenticate.First().ToString());
+            Assert.Equal("", response.ResponseText);
+        }
+
         [Fact]
         public async Task CustomTokenValidated()
         {