added support for 2-way RPC sessions. closes #1

client.go

@@ -1,6 +1,7 @@
 package sshrpc
 
 import (
+	"log"
 	"net/rpc"
 
 	"golang.org/x/crypto/ssh"
@@ -12,6 +13,7 @@ type Client struct {
 	Config      *ssh.ClientConfig
 	ChannelName string
 	sshClient   *ssh.Client
+	RPCServer   *rpc.Server
 }
 
 // NewClient returns a new Client to handle RPC requests.
@@ -24,7 +26,7 @@ func NewClient() *Client {
 		},
 	}
 
-	return &Client{nil, config, DefaultRPCChannel, nil}
+	return &Client{nil, config, DefaultRPCChannel, nil, rpc.NewServer()}
 
 }
 
@@ -37,37 +39,27 @@ func (c *Client) Connect(address string) {
 	}
 	c.sshClient = sshClient
 
+	c.openRPCServerChannel(c.ChannelName + "-reverse")
+
 	// Each ClientConn can support multiple channels
-	channel, err := c.openRPCChannel(c.ChannelName)
+	channel, err := openRPCClientChannel(c.sshClient.Conn, c.ChannelName)
 	if err != nil {
 		panic("Failed to create channel: " + err.Error())
 	}
 
 	c.Client = rpc.NewClient(channel)
 
-	return
 }
 
-// openRPCChannel opens an SSH RPC channel and makes an ssh subsystem request to trigger remote RPC server start
-func (c *Client) openRPCChannel(channelName string) (ssh.Channel, error) {
-	channel, in, err := c.sshClient.OpenChannel(channelName, nil)
+// openRPCClientChannel opens an SSH RPC channel and makes an ssh subsystem request to trigger remote RPC server start
+func openRPCClientChannel(conn ssh.Conn, channelName string) (ssh.Channel, error) {
+	channel, in, err := conn.OpenChannel(channelName, nil)
 	if err != nil {
 		return nil, err
 	}
 
 	// SSH Documentation states that this go channel of requests needs to be serviced
-	go func(reqs <-chan *ssh.Request) error {
-		for msg := range reqs {
-			switch msg.Type {
-
-			default:
-				if msg.WantReply {
-					msg.Reply(false, nil)
-				}
-			}
-		}
-		return nil
-	}(in)
+	go ssh.DiscardRequests(in)
 
 	var msg struct {
 		Subsystem string
@@ -81,3 +73,63 @@ func (c *Client) openRPCChannel(channelName string) (ssh.Channel, error) {
 
 	return channel, nil
 }
+
+func (c *Client) openRPCServerChannel(channelName string) error {
+	subChannel := c.sshClient.HandleChannelOpen(channelName)
+	go func(chans <-chan ssh.NewChannel) {
+
+		for newChannel := range chans {
+
+			/* Don't need to check, already know what channel type is coming in
+			// Check the type of channel
+			if t := newChannel.ChannelType(); t != channelName {
+				newChannel.Reject(ssh.UnknownChannelType, fmt.Sprintf("unknown channel type: %s", t))
+				continue
+			}
+			*/
+			acceptRPCServerRequest(c.RPCServer, newChannel)
+		}
+	}(subChannel)
+	return nil
+}
+
+func acceptRPCServerRequest(rpcServer *rpc.Server, newChannel ssh.NewChannel) {
+	channel, requests, err := newChannel.Accept()
+	if err != nil {
+		log.Printf("could not accept channel (%s)", err)
+		return
+	}
+	log.Printf("Accepted channel")
+
+	// Channels can have out-of-band requests
+	go func(in <-chan *ssh.Request) {
+		for req := range in {
+			ok := false
+			switch req.Type {
+
+			case "subsystem":
+				ok = true
+				log.Printf("subsystem '%s'", req.Payload)
+				switch string(req.Payload[4:]) {
+				//RPCSubsystem Request made indicates client desires RPC Server access
+				case RPCSubsystem:
+					go rpcServer.ServeConn(channel)
+					log.Printf("Started SSH RPC")
+				default:
+					log.Printf("Unknown subsystem: %s", req.Payload)
+				}
+
+			}
+			if !ok {
+				log.Printf("declining %s request...", req.Type)
+			}
+			req.Reply(ok, nil)
+		}
+
+	}(requests)
+}
+
+// Wait allows clients also acting as an RPC server to detect when the ssh connection ends
+func (c *Client) Wait() error {
+	return c.sshClient.Conn.Wait()
+}

server.go

@@ -20,6 +20,8 @@ type Server struct {
 	*rpc.Server
 	Config      *ssh.ServerConfig
 	ChannelName string
+	RPCClient   *rpc.Client
+	sshConn     ssh.Conn
 }
 
 // NewServer returns a new Server to handle incoming SSH and RPC requests.
@@ -32,7 +34,7 @@ func NewServer() *Server {
 			return nil, fmt.Errorf("password rejected for %q", c.User())
 		},
 	}
-	return &Server{rpc.NewServer(), c, DefaultRPCChannel}
+	return &Server{rpc.NewServer(), c, DefaultRPCChannel, nil, nil}
 
 }
 
@@ -55,6 +57,7 @@ func (s *Server) StartServer(address string) {
 		}
 		// Before use, a handshake must be performed on the incoming net.Conn.
 		sshConn, chans, reqs, err := ssh.NewServerConn(tcpConn, s.Config)
+		s.sshConn = sshConn
 		if err != nil {
 			log.Printf("failed to handshake (%s)", err)
 			continue
@@ -65,6 +68,7 @@ func (s *Server) StartServer(address string) {
 		go s.handleRequests(reqs)
 		// Accept all channels
 		go s.handleChannels(chans)
+
 	}
 }
 
@@ -107,6 +111,14 @@ func (s *Server) handleChannels(chans <-chan ssh.NewChannel) {
 					case RPCSubsystem:
 						go s.ServeConn(channel)
 						log.Printf("Started SSH RPC")
+						// triggers reverse RPC connection as well
+						clientChannel, err := openRPCClientChannel(s.sshConn, s.ChannelName+"-reverse")
+						if err != nil {
+							log.Printf("Failed to create client channel: " + err.Error())
+							continue
+						}
+						s.RPCClient = rpc.NewClient(clientChannel)
+						log.Printf("Started SSH RPC client")
 					default:
 						log.Printf("Unknown subsystem: %s", req.Payload)
 					}