implement C# wrapping for plugin API

src/csharp/Grpc.Core/Credentials.cs

@@ -32,10 +32,17 @@
 #endregion
 
 using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
 using Grpc.Core.Internal;
+using Grpc.Core.Utils;
 
 namespace Grpc.Core
 {
+    // TODO: rename
+    public delegate Task AsyncAuthInterceptor(string authUri, Metadata metadata);
+
     /// <summary>
     /// Client-side credentials. Used for creation of a secure channel.
     /// </summary>
@@ -135,4 +142,49 @@ namespace Grpc.Core
             return CredentialsSafeHandle.CreateSslCredentials(rootCertificates, keyCertificatePair);
         }
     }
+
+    /// <summary>
+    /// Client-side credentials that delegate metadata based auth to an interceptor.
+    /// </summary>
+    public partial class MetadataCredentials : Credentials
+    {
+        readonly AsyncAuthInterceptor interceptor;
+
+        public MetadataCredentials(AsyncAuthInterceptor interceptor)
+        {
+            this.interceptor = interceptor;
+        }
+
+        internal override CredentialsSafeHandle ToNativeCredentials()
+        {
+            NativeMetadataCredentialsPlugin plugin = new NativeMetadataCredentialsPlugin(interceptor);
+            return plugin.Credentials;
+        }
+    }
+
+    public sealed class CompositeCredentials : Credentials
+    {
+        readonly List<Credentials> credentials;
+
+        public CompositeCredentials(params Credentials[] credentials)
+        {
+            Preconditions.CheckArgument(credentials.Length >= 2, "Composite credentials object can only be created from 2 or more credentials.");
+            this.credentials = new List<Credentials>(credentials);
+        }
+
+        public static CompositeCredentials Create(params Credentials[] credentials)
+        {
+            return new CompositeCredentials(credentials);
+        }
+
+        internal override CredentialsSafeHandle ToNativeCredentials()
+        {
+            var nativeComposite = credentials[0].ToNativeCredentials();
+            for (int i = 1; i < credentials.Count; i++)
+            {
+                nativeComposite = CredentialsSafeHandle.CreateComposite(nativeComposite, credentials[i].ToNativeCredentials());
+            }
+            return nativeComposite;
+        }
+    }
 }

src/csharp/Grpc.Core/Grpc.Core.csproj

@@ -49,6 +49,7 @@
     <Compile Include="AsyncDuplexStreamingCall.cs" />
     <Compile Include="AsyncServerStreamingCall.cs" />
     <Compile Include="IClientStreamWriter.cs" />
+    <Compile Include="Internal\NativeMetadataCredentialsPlugin.cs" />
     <Compile Include="Internal\INativeCall.cs" />
     <Compile Include="IServerStreamWriter.cs" />
     <Compile Include="IAsyncStreamWriter.cs" />

src/csharp/Grpc.Core/Internal/CredentialsSafeHandle.cs

@@ -43,6 +43,9 @@ namespace Grpc.Core.Internal
         [DllImport("grpc_csharp_ext.dll", CharSet = CharSet.Ansi)]
         static extern CredentialsSafeHandle grpcsharp_ssl_credentials_create(string pemRootCerts, string keyCertPairCertChain, string keyCertPairPrivateKey);
 
+        [DllImport("grpc_csharp_ext.dll")]
+        static extern CredentialsSafeHandle grpcsharp_composite_credentials_create(CredentialsSafeHandle creds1, CredentialsSafeHandle creds2);
+
         [DllImport("grpc_csharp_ext.dll")]
         static extern void grpcsharp_credentials_release(IntPtr credentials);
 
@@ -69,6 +72,11 @@ namespace Grpc.Core.Internal
             }
         }
 
+        public static CredentialsSafeHandle CreateComposite(CredentialsSafeHandle creds1, CredentialsSafeHandle creds2)
+        {
+            return grpcsharp_composite_credentials_create(creds1, creds2);
+        }
+
         protected override bool ReleaseHandle()
         {
             grpcsharp_credentials_release(handle);

src/csharp/Grpc.Core/Internal/NativeMetadataCredentialsPlugin.cs

@@ -0,0 +1,112 @@
+#region Copyright notice and license
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Grpc.Core.Logging;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core.Internal
+{
+    internal delegate void NativeMetadataInterceptor(IntPtr statePtr, IntPtr serviceUrlPtr, IntPtr callbackPtr, IntPtr userDataPtr, bool isDestroy);
+
+    internal class NativeMetadataCredentialsPlugin
+    {
+        const string GetMetadataExceptionMsg = "Exception occured in metadata credentials plugin.";
+        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<NativeMetadataCredentialsPlugin>();
+
+        [DllImport("grpc_csharp_ext.dll")]
+        static extern CredentialsSafeHandle grpcsharp_metadata_credentials_create_from_plugin(NativeMetadataInterceptor interceptor);
+        
+        [DllImport("grpc_csharp_ext.dll", CharSet = CharSet.Ansi)]
+        static extern void grpcsharp_metadata_credentials_notify_from_plugin(IntPtr callbackPtr, IntPtr userData, MetadataArraySafeHandle metadataArray, StatusCode statusCode, string errorDetails);
+
+        AsyncAuthInterceptor interceptor;
+        GCHandle gcHandle;
+        NativeMetadataInterceptor nativeInterceptor;
+        CredentialsSafeHandle credentials;
+
+        public NativeMetadataCredentialsPlugin(AsyncAuthInterceptor interceptor)
+        {
+            this.interceptor = Preconditions.CheckNotNull(interceptor, "interceptor");
+            this.nativeInterceptor = NativeMetadataInterceptorHandler;
+
+            // Make sure the callback doesn't get garbage collected until it is destroyed.
+            this.gcHandle = GCHandle.Alloc(this.nativeInterceptor, GCHandleType.Normal);
+            this.credentials = grpcsharp_metadata_credentials_create_from_plugin(nativeInterceptor);
+        }
+
+        public CredentialsSafeHandle Credentials
+        {
+            get { return credentials; }
+        }
+
+        private void NativeMetadataInterceptorHandler(IntPtr statePtr, IntPtr serviceUrlPtr, IntPtr callbackPtr, IntPtr userDataPtr, bool isDestroy)
+        {
+            if (isDestroy)
+            {
+                gcHandle.Free();
+                return;
+            }
+
+            try
+            {
+                string serviceUrl = Marshal.PtrToStringAnsi(serviceUrlPtr);
+                StartGetMetadata(serviceUrl, callbackPtr, userDataPtr);
+            }
+            catch (Exception e)
+            {
+                grpcsharp_metadata_credentials_notify_from_plugin(callbackPtr, userDataPtr, null, StatusCode.Unknown, GetMetadataExceptionMsg);
+                Logger.Error(e, GetMetadataExceptionMsg);
+            }
+        }
+
+        private async void StartGetMetadata(string serviceUrl, IntPtr callbackPtr, IntPtr userDataPtr)
+        {
+            try
+            {
+                var metadata = new Metadata();
+                await interceptor(serviceUrl, metadata);
+                using (var metadataArray = MetadataArraySafeHandle.Create(metadata))
+                {
+                    grpcsharp_metadata_credentials_notify_from_plugin(callbackPtr, userDataPtr, metadataArray, StatusCode.OK, null);
+                }
+            }
+            catch (Exception e)
+            {
+                grpcsharp_metadata_credentials_notify_from_plugin(callbackPtr, userDataPtr, null, StatusCode.Unknown, GetMetadataExceptionMsg);
+                Logger.Error(e, GetMetadataExceptionMsg);
+            }
+        }
+    }
+}

src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj

@@ -96,6 +96,7 @@
     <Compile Include="Empty.cs" />
     <Compile Include="Messages.cs" />
     <Compile Include="InteropClientServerTest.cs" />
+    <Compile Include="MetadataCredentialsTest.cs" />
     <Compile Include="TestServiceImpl.cs" />
     <Compile Include="InteropServer.cs" />
     <Compile Include="InteropClient.cs" />

src/csharp/Grpc.IntegrationTesting/MetadataCredentialsTest.cs

@@ -0,0 +1,100 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Utils;
+using Grpc.Testing;
+using NUnit.Framework;
+
+namespace Grpc.IntegrationTesting
+{
+    public class MetadataCredentialsTest
+    {
+        const string Host = "localhost";
+        Server server;
+        Channel channel;
+        TestService.ITestServiceClient client;
+
+        [TestFixtureSetUp]
+        public void Init()
+        {
+            var serverCredentials = new SslServerCredentials(new[] { new KeyCertificatePair(
+                File.ReadAllText(TestCredentials.ServerCertChainPath),
+                File.ReadAllText(TestCredentials.ServerPrivateKeyPath)) });
+            server = new Server
+            {
+                Services = { TestService.BindService(new TestServiceImpl()) },
+                Ports = { { Host, ServerPort.PickUnused, serverCredentials } }
+            };
+            server.Start();
+
+            var options = new List<ChannelOption>
+            {
+                new ChannelOption(ChannelOptions.SslTargetNameOverride, TestCredentials.DefaultHostOverride)
+            };
+
+            var asyncAuthInterceptor = new AsyncAuthInterceptor(async (authUri, metadata) =>
+            {
+                await Task.Delay(100);  // make sure the operation is asynchronous.
+                metadata.Add("authorization", "SECRET_TOKEN");
+            });
+
+            var clientCredentials = CompositeCredentials.Create(
+                new SslCredentials(File.ReadAllText(TestCredentials.ClientCertAuthorityPath)),
+                new MetadataCredentials(asyncAuthInterceptor)
+            );
+            channel = new Channel(Host, server.Ports.Single().BoundPort, clientCredentials, options);
+            client = TestService.NewClient(channel);
+        }
+
+        [TestFixtureTearDown]
+        public void Cleanup()
+        {
+            channel.ShutdownAsync().Wait();
+            server.ShutdownAsync().Wait();
+        }
+
+        [Test]
+        public void MetadataCredentials()
+        {
+            var response = client.UnaryCall(new SimpleRequest { ResponseSize = 10 });
+            Assert.AreEqual(10, response.Payload.Body.Length);
+        }
+    }
+}

src/csharp/ext/grpc_csharp_ext.c

@@ -68,7 +68,7 @@ grpc_byte_buffer *string_to_byte_buffer(const char *buffer, size_t len) {
 /*
  * Helper to maintain lifetime of batch op inputs and store batch op outputs.
  */
-typedef struct gprcsharp_batch_context {
+typedef struct grpcsharp_batch_context {
   grpc_metadata_array send_initial_metadata;
   grpc_byte_buffer *send_message;
   struct {
@@ -892,6 +892,45 @@ grpcsharp_server_add_secure_http2_port(grpc_server *server, const char *addr,
   return grpc_server_add_secure_http2_port(server, addr, creds);
 }
 
+GPR_EXPORT grpc_credentials *GPR_CALLTYPE grpcsharp_composite_credentials_create(
+	grpc_credentials *creds1,
+	grpc_credentials *creds2) {
+	return grpc_composite_credentials_create(creds1, creds2, NULL);
+}
+
+/* Metadata credentials plugin */
+
+GPR_EXPORT void GPR_CALLTYPE grpcsharp_metadata_credentials_notify_from_plugin(
+	void *callback_ptr, void *user_data, grpc_metadata_array *metadata,
+	grpc_status_code status, const char *error_details) {
+	grpc_credentials_plugin_metadata_cb cb = (grpc_credentials_plugin_metadata_cb)callback_ptr;
+	cb(user_data, metadata->metadata, metadata->count, status, error_details);
+}
+
+typedef void(GPR_CALLTYPE *grpcsharp_metadata_interceptor_func)(
+	void *state, const char *service_url, void *callback_ptr,
+	void *user_data, gpr_int32 is_destroy);
+
+static void grpcsharp_get_metadata_handler(void *state, const char *service_url,
+	grpc_credentials_plugin_metadata_cb cb, void *user_data) {
+	grpcsharp_metadata_interceptor_func interceptor = (grpcsharp_metadata_interceptor_func)state;
+	interceptor(state, service_url, (void*)cb, user_data, 0);
+}
+
+static void grpcsharp_metadata_credentials_destroy_handler(void *state) {
+	grpcsharp_metadata_interceptor_func interceptor = (grpcsharp_metadata_interceptor_func)state;
+	interceptor(state, NULL, NULL, NULL, 1);
+}
+
+GPR_EXPORT grpc_credentials *GPR_CALLTYPE grpcsharp_metadata_credentials_create_from_plugin(
+	grpcsharp_metadata_interceptor_func metadata_interceptor) {
+  grpc_metadata_credentials_plugin plugin;
+  plugin.get_metadata = grpcsharp_get_metadata_handler;
+  plugin.destroy = grpcsharp_metadata_credentials_destroy_handler;
+  plugin.state = metadata_interceptor;
+  return grpc_metadata_credentials_create_from_plugin(plugin, NULL);
+}
+
 /* Logging */
 
 typedef void(GPR_CALLTYPE *grpcsharp_log_func)(const char *file, gpr_int32 line,