Fix allocator service tls auth for C# client and add a C# sample

cmd/allocator/main.go

@@ -185,22 +185,42 @@ func (h *serviceHandler) getServerOptions() []grpc.ServerOption {
 	}
 
 	cfg := &tls.Config{
-		Certificates: []tls.Certificate{tlsCer},
-		ClientAuth:   tls.RequireAndVerifyClientCert,
-		GetConfigForClient: func(*tls.ClientHelloInfo) (*tls.Config, error) {
-			h.certMutex.RLock()
-			defer h.certMutex.RUnlock()
-			return &tls.Config{
-				Certificates: []tls.Certificate{tlsCer},
-				ClientAuth:   tls.RequireAndVerifyClientCert,
-				ClientCAs:    h.caCertPool,
-			}, nil
-		},
+		Certificates:          []tls.Certificate{tlsCer},
+		ClientAuth:            tls.RequireAnyClientCert,
+		VerifyPeerCertificate: h.verifyClientCertificate,
 	}
 	// Add options for creds and OpenCensus stats handler to enable stats and tracing.
 	return []grpc.ServerOption{grpc.Creds(credentials.NewTLS(cfg)), grpc.StatsHandler(&ocgrpc.ServerHandler{})}
 }
 
+// verifyClientCertificate verifies that the client certificate is accepted
+// This method is used as GetConfigForClient is cross lang incompatible.
+func (h *serviceHandler) verifyClientCertificate(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
+	opts := x509.VerifyOptions{
+		Roots:         h.caCertPool,
+		CurrentTime:   time.Now(),
+		Intermediates: x509.NewCertPool(),
+		KeyUsages:     []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+	}
+
+	for _, cert := range rawCerts[1:] {
+		opts.Intermediates.AppendCertsFromPEM(cert)
+	}
+
+	c, err := x509.ParseCertificate(rawCerts[0])
+	if err != nil {
+		return errors.New("bad client certificate: " + err.Error())
+	}
+
+	h.certMutex.RLock()
+	defer h.certMutex.RUnlock()
+	_, err = c.Verify(opts)
+	if err != nil {
+		return errors.New("failed to verify client certificate: " + err.Error())
+	}
+	return nil
+}
+
 // Set up our client which we will use to call the API
 func getClients() (*kubernetes.Clientset, *versioned.Clientset, error) {
 	// Create the in-cluster config

cmd/allocator/main_test.go

@@ -15,6 +15,8 @@ package main
 
 import (
 	"context"
+	"crypto/x509"
+	"encoding/pem"
 	"io/ioutil"
 	"net/http"
 	"os"
@@ -133,6 +135,38 @@ func TestBadReturnType(t *testing.T) {
 	assert.Contains(t, st.Message(), "internal server error")
 }
 
+func TestVerifyClientCertificateSucceeds(t *testing.T) {
+	t.Parallel()
+
+	crt := []byte(clientCert)
+	certPool := x509.NewCertPool()
+	assert.True(t, certPool.AppendCertsFromPEM(crt))
+
+	h := serviceHandler{
+		caCertPool: certPool,
+	}
+
+	block, _ := pem.Decode(crt)
+	input := [][]byte{block.Bytes}
+	assert.Nil(t, h.verifyClientCertificate(input, nil),
+		"verifyClientCertificate failed.")
+}
+
+func TestVerifyClientCertificateFails(t *testing.T) {
+	t.Parallel()
+
+	crt := []byte(clientCert)
+	certPool := x509.NewCertPool()
+	h := serviceHandler{
+		caCertPool: certPool,
+	}
+
+	block, _ := pem.Decode(crt)
+	input := [][]byte{block.Bytes}
+	assert.Error(t, h.verifyClientCertificate(input, nil),
+		"verifyClientCertificate() succeeded, expected error.")
+}
+
 func TestGettingCaCert(t *testing.T) {
 	t.Parallel()
 

examples/allocator-client-csharp/Program.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using System.IO;
+using Grpc.Core;
+using V1Alpha1;
+using System.Net.Http;
+
+namespace AllocatorClient
+{
+    class Program
+    {
+        static async Task Main(string[] args)
+        {
+            if (args.Length < 6) {
+                throw new Exception("Arguments are missing. Expecting: <private key> <public key> <server CA> <external IP> <namepace> <enable multi-cluster>");
+            }
+
+            string clientKey    = File.ReadAllText(args[0]);
+            string clientCert   = File.ReadAllText(args[1]);
+            string serverCa     = File.ReadAllText(args[2]);
+            string externalIp   = args[3];
+            string namespaceArg = args[4];
+            bool   multicluster = bool.Parse(args[5]);
+
+            var creds = new SslCredentials(serverCa, new KeyCertificatePair(clientCert, clientKey));
+            var channel = new Channel(externalIp + ":443", creds);
+            var client = new AllocationService.AllocationServiceClient(channel);
+
+           try {
+                var response = await client.AllocateAsync(new AllocationRequest { 
+                    Namespace = namespaceArg,
+                    MultiClusterSetting = new V1Alpha1.MultiClusterSetting {
+                        Enabled = multicluster,
+                    }
+                });
+                Console.WriteLine(response);
+            } 
+            catch(RpcException e)
+            {
+                Console.WriteLine($"gRPC error: {e}");
+            }
+        }
+    }
+}

examples/allocator-client-csharp/README.md

@@ -0,0 +1,19 @@
+# A sample Allocator service C# client
+
+This sample serves as a gRPC C# client sample code for agones-allocator gRPC service.
+
+Follow instructions in [Allocator Service](https://agones.dev/site/docs/advanced/allocator-service) to set up client and server certificate.
+
+Run the following to allocate a game server:
+```
+#!/bin/bash
+
+NAMESPACE=default # replace with any namespace
+EXTERNAL_IP=`kubectl get services agones-allocator -n agones-system -o jsonpath='{.status.loadBalancer.ingress[0].ip}'`
+KEY_FILE=client.key
+CERT_FILE=client.crt
+TLS_CA_FILE=ca.crt
+MULTICLUSTER_ENABLED=false
+
+dotnet run $KEY_FILE $CERT_FILE $TLS_CA_FILE $EXTERNAL_IP $NAMESPACE $MULTICLUSTER_ENABLED
+```

examples/allocator-client-csharp/allocator-client-csharp.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <RootNamespace>AllocatorClient</RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Google.Api.CommonProtos" Version="1.7.0" />
+    <PackageReference Include="Google.Protobuf" Version="3.11.2" />
+    <PackageReference Include="Grpc" Version="2.26.0" />
+    <PackageReference Include="Grpc.Core" Version="2.26.0" />
+    <PackageReference Include="Grpc.Tools" Version="2.26.0" PrivateAssets="all"/>
+  </ItemGroup>
+
+  <ItemGroup>
+    <Protobuf Include="allocation.proto" ProtoRoot="../../proto/allocation/v1alpha1;../../proto/googleapis" GrpcServices="Client"/>
+  </ItemGroup>
+</Project>

examples/allocator-client/main.go

@@ -34,7 +34,7 @@ func main() {
 	cacertFile := flag.String("cacert", "missing cacert", "the CA cert file for server signing certificate in PEM format")
 	externalIP := flag.String("ip", "missing external IP", "the external IP for allocator server")
 	namespace := flag.String("namespace", "default", "the game server kubernetes namespace")
-	multicluster := flag.Bool("multicluster", false, "enabling")
+	multicluster := flag.Bool("multicluster", false, "set to true to enable the multi-cluster allocation")
 
 	flag.Parse()
 

site/content/en/docs/Advanced/allocator-service.md

@@ -115,7 +115,8 @@ kubectl get pods -n agones-system -o=name | grep agones-allocator | xargs kubect
 
 ## Send allocation request
 
-Now the service is ready to accept requests from the client with the generated certificates. Create a [fleet](https://agones.dev/site/docs/getting-started/create-fleet/#1-create-a-fleet) and send a gRPC request to agones-allocator by providing the namespace to which the fleet is deployed. You can find the gRPC sample for sending allocation request at {{< ghlink href="examples/allocator-client/main.go" >}}allocator-client sample{{< /ghlink >}}.
+Now the service is ready to accept requests from the client with the generated certificates. Create a [fleet](https://agones.dev/site/docs/getting-started/create-fleet/#1-create-a-fleet) and send a gRPC request to agones-allocator. To start, take a look at the allocation gRPC client examples in {{< ghlink href="examples/allocator-client/main.go" >}}golang{{< /ghlink >}} and {{< ghlink href="examples/allocator-client-csharp/Program.cs" >}}C#{{< /ghlink >}} languages. In the following, the {{< ghlink href="examples/allocator-client/main.go" >}}golang gRPC client example{{< /ghlink >}} is used to allocate a Game Server in the default namespace.
+
 
 ```bash
 #!/bin/bash