Merge pull request #186 from iamqizhao/master

Allow some handshaking between client and server before rpc happens.

clientconn.go

@@ -104,6 +104,15 @@ func WithDialer(f func(addr string, timeout time.Duration) (net.Conn, error)) Di
 	}
 }
 
+// WithHandshaker returns a DialOption that specifies a function to perform some handshaking
+// with the server. It is typically used to negotiate the wire protocol version and security
+// protocol with the server.
+func WithHandshaker(h func(conn net.Conn) (credentials.TransportAuthenticator, error)) DialOption {
+	return func(o *dialOptions) {
+		o.copts.Handshaker = h
+	}
+}
+
 // Dial creates a client connection the given target.
 // TODO(zhaoq): Have an option to make Dial return immediately without waiting
 // for connection to complete.

credentials/credentials.go

@@ -70,8 +70,19 @@ type Credentials interface {
 	GetRequestMetadata(ctx context.Context) (map[string]string, error)
 }
 
-// TransportAuthenticator defines the common interface all supported transport
-// authentication protocols (e.g., TLS, SSL) must implement.
+// ProtocolInfo provides information regarding the gRPC wire protocol version,
+// security protocol, security protocol version in use, etc.
+type ProtocolInfo struct {
+	// ProtocolVersion is the gRPC wire protocol version.
+	ProtocolVersion string
+	// SecurityProtocol is the security protocol in use.
+	SecurityProtocol string
+	// SecurityVersion is the security protocol version.
+	SecurityVersion string
+}
+
+// TransportAuthenticator defines the common interface for all the live gRPC wire
+// protocols and supported transport security protocols (e.g., TLS, SSL).
 type TransportAuthenticator interface {
 	// Handshake does the authentication handshake specified by the corresponding
 	// authentication protocol on rawConn.
@@ -79,6 +90,8 @@ type TransportAuthenticator interface {
 	// NewListener creates a listener which accepts connections with requested
 	// authentication handshake.
 	NewListener(lis net.Listener) net.Listener
+	// Info provides the ProtocolInfo of this TransportAuthenticator.
+	Info() ProtocolInfo
 	Credentials
 }
 
@@ -88,6 +101,13 @@ type tlsCreds struct {
 	config tls.Config
 }
 
+func (c *tlsCreds) Info() ProtocolInfo {
+	return ProtocolInfo{
+		SecurityProtocol: "tls",
+		SecurityVersion:  "1.2",
+	}
+}
+
 // GetRequestMetadata returns nil, nil since TLS credentials does not have
 // metadata.
 func (c *tlsCreds) GetRequestMetadata(ctx context.Context) (map[string]string, error) {

transport/http2_client.go

@@ -111,6 +111,17 @@ func newHTTP2Client(addr string, opts *ConnectOptions) (_ ClientTransport, err e
 	if connErr != nil {
 		return nil, ConnectionErrorf("transport: %v", connErr)
 	}
+	// Perform handshake if opts.Handshaker is set.
+	if opts.Handshaker != nil {
+		auth, err := opts.Handshaker(conn)
+		if err != nil {
+			return nil, ConnectionErrorf("transport: handshaking failed %v", err)
+		}
+		// Prepend the resulting authenticator to opts.AuthOptions.
+		if auth != nil {
+			opts.AuthOptions = append([]credentials.Credentials{auth}, opts.AuthOptions...)
+		}
+	}
 	for _, c := range opts.AuthOptions {
 		if ccreds, ok := c.(credentials.TransportAuthenticator); ok {
 			scheme = "https"

transport/transport.go

@@ -316,6 +316,7 @@ func NewServerTransport(protocol string, conn net.Conn, maxStreams uint32) (Serv
 // ConnectOptions covers all relevant options for dialing a server.
 type ConnectOptions struct {
 	Dialer      func(string, time.Duration) (net.Conn, error)
+	Handshaker  func(conn net.Conn) (credentials.TransportAuthenticator, error)
 	AuthOptions []credentials.Credentials
 	Timeout     time.Duration
 }