FAB-1259 Create Basic Common GRPC Server

This is the initial phase of creating a common
GRPC server object to handle common operations such
as TLS.

This change set provides a basic GRPC server object and
functions to create plain and TLS enabled GRPC servers

Fixes FAB-1259

Change-Id: Ic63bec9e8747083016dbcddab06f1061903d5a59
Signed-off-by: Gari Singh <gari.r.singh@gmail.com>

core/comm/server.go

@@ -0,0 +1,200 @@
+/*
+Copyright IBM Corp. 2016 All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+		 http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package comm
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"net"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+)
+
+//GRPCServer defines an interface representing a GRPC-based server
+type GRPCServer interface {
+	//Address returns the listen address for the GRPCServer
+	Address() string
+	//Start starts the underlying grpc.Server
+	Start() error
+	//Stop stops the underlying grpc.Server
+	Stop()
+	//Server returns the grpc.Server instance for the GRPCServer
+	Server() *grpc.Server
+	//Listener returns the net.Listener instance for the GRPCServer
+	Listener() net.Listener
+	//ServerCertificate returns the tls.Certificate used by the grpc.Server
+	ServerCertificate() tls.Certificate
+	//TLSEnabled is a flag indicating whether or not TLS is enabled for this GRPCServer instance
+	TLSEnabled() bool
+}
+
+type grpcServerImpl struct {
+	//Listen address for the server specified as hostname:port
+	address string
+	//Listener for handling network requests
+	listener net.Listener
+	//GRPC server
+	server *grpc.Server
+	//Certificate presented by the server for TLS communication
+	serverCertificate tls.Certificate
+	//Key used by the server for TLS communication
+	serverKeyPEM []byte
+	//List of certificate authorities to optionally pass to the client during the TLS handshake
+	serverRootCAs []tls.Certificate
+	//List of certificate authorities to be used to authenticate clients if client authentication is required
+	clientRootCAs *x509.CertPool
+	//Is TLS enabled?
+	tlsEnabled bool
+}
+
+/*
+NewGRPCServer creates a new implementation of a GRPCServer given a listen address.
+In order to enable TLS, serverKey and ServerCertificate are required.
+
+Parameters:
+	address:  Listen address to use formatted as hostname:port
+	serverKey:  PEM-encoded private key to be used by the server for TLS communication
+	serverCertificate:  PEM-encoded X509 public key to be used by the server for TLS communication
+	serverRootCAs:  (optional) Set of PEM-encoded X509 certificate authorities to optionally send as part of
+					the server handshake
+	clientRootCAs:  (optional) Set of PEM-encoded X509 certificate authorities to use when verifying client
+					certificates
+*/
+func NewGRPCServer(address string, serverKey []byte, serverCertificate []byte, serverRootCAs [][]byte,
+	clientRootCAs [][]byte) (GRPCServer, error) {
+
+	if address == "" {
+		return nil, errors.New("Missing address parameter")
+	}
+	//create our listener
+	lis, err := net.Listen("tcp", address)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return NewGRPCServerFromListener(lis, serverKey, serverCertificate, serverRootCAs, clientRootCAs)
+
+}
+
+/*
+NewGRPCServerFromListener creates a new implementation of a GRPCServer given an existing Listener instance.
+In order to enable TLS, serverKey and ServerCertificate are required.
+
+Parameters:
+	listener:  Listener to use
+	serverKey:  PEM-encoded private key to be used by the server for TLS communication
+	serverCertificate:  PEM-encoded X509 public key to be used by the server for TLS communication
+	serverRootCAs:  (optional) Set of PEM-encoded X509 certificate authorities to optionally send as part of
+					the server handshake
+	clientRootCAs:  (optional) Set of PEM-encoded X509 certificate authorities to use when verifying client
+					certificates
+*/
+func NewGRPCServerFromListener(listener net.Listener, serverKey []byte, serverCertificate []byte,
+	serverRootCAs [][]byte, clientRootCAs [][]byte) (GRPCServer, error) {
+
+	grpcServer := &grpcServerImpl{
+		address:  listener.Addr().String(),
+		listener: listener,
+	}
+
+	//set up our server options
+	var serverOpts []grpc.ServerOption
+	//check for TLS parameters
+	if serverKey != nil || serverCertificate != nil {
+		//both are required
+		if serverKey != nil && serverCertificate != nil {
+			grpcServer.tlsEnabled = true
+			//load server public and private keys
+			cert, err := tls.X509KeyPair(serverCertificate, serverKey)
+			if err != nil {
+				return nil, err
+			}
+			grpcServer.serverCertificate = cert
+
+			//set up our TLS config
+
+			//base server certificate
+			certificates := []tls.Certificate{grpcServer.serverCertificate}
+
+			/**
+			//if we have server root CAs append them
+			if len(serverRootCAs) > 0 {
+				//certificates = append(certificates, serverRootCAs...)
+			}
+
+			//if we have client root CAs, create a certPool
+			if len(clientRootCAs) > 0 {
+				grpcServer.clientRootCAs = x509.NewCertPool()
+			}
+			*/
+			tlsConfig := &tls.Config{
+				Certificates: certificates,
+			}
+
+			//create credentials
+			creds := credentials.NewTLS(tlsConfig)
+
+			//add to server options
+			serverOpts = append(serverOpts, grpc.Creds(creds))
+
+		} else {
+			return nil, errors.New("Both serverKey and serverCertificate are required in order to enable TLS")
+		}
+	}
+
+	grpcServer.server = grpc.NewServer(serverOpts...)
+
+	return grpcServer, nil
+}
+
+//Address returns the listen address for this GRPCServer instance
+func (gServer *grpcServerImpl) Address() string {
+	return gServer.address
+}
+
+//Listener returns the net.Listener for the GRPCServer instance
+func (gServer *grpcServerImpl) Listener() net.Listener {
+	return gServer.listener
+}
+
+//Server returns the grpc.Server for the GRPCServer instance
+func (gServer *grpcServerImpl) Server() *grpc.Server {
+	return gServer.server
+}
+
+//ServerCertificate returns the tls.Certificate used by the grpc.Server
+func (gServer *grpcServerImpl) ServerCertificate() tls.Certificate {
+	return gServer.serverCertificate
+}
+
+//TLSEnabled is a flag indicating whether or not TLS is enabled for the GRPCServer instance
+func (gServer *grpcServerImpl) TLSEnabled() bool {
+	return gServer.tlsEnabled
+}
+
+//Start starts the underlying grpc.Server
+func (gServer *grpcServerImpl) Start() error {
+	return gServer.server.Serve(gServer.listener)
+}
+
+//Stop stops the underlying grpc.Server
+func (gServer *grpcServerImpl) Stop() {
+	gServer.server.Stop()
+}