Support subsystem

_examples/ssh-sftp/sftp.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"github.com/gliderlabs/ssh"
+	"github.com/pkg/sftp"
+	"io"
+	"io/ioutil"
+	"log"
+)
+
+func SftpHandler(sess ssh.Session) {
+	debugStream := ioutil.Discard
+	serverOptions := []sftp.ServerOption{
+		sftp.WithDebug(debugStream),
+	}
+	server, err := sftp.NewServer(
+		sess,
+		serverOptions...,
+	)
+	if err != nil {
+		log.Printf("sftp server init error: %s\n", err)
+		return
+	}
+	if err := server.Serve(); err == io.EOF {
+		server.Close()
+		fmt.Println("sftp client exited session.")
+	} else if err != nil {
+		fmt.Println("sftp server completed with error:", err)
+	}
+
+}
+
+func main() {
+	srv := ssh.Server{
+		Addr:              ":2223",
+		SubsystemHandlers: map[string]ssh.SubsystemHandler{},
+	}
+	srv.SetSubsystemHandler("sftp", SftpHandler)
+	log.Fatal(srv.ListenAndServe())
+}

server.go

@@ -40,6 +40,8 @@ type Server struct {
 	channelHandlers map[string]channelHandler
 	requestHandlers map[string]RequestHandler
 
+	SubsystemHandlers map[string]SubsystemHandler
+
 	listenerWg sync.WaitGroup
 	mu         sync.Mutex
 	listeners  map[net.Listener]struct{}
@@ -381,3 +383,7 @@ func (srv *Server) trackConn(c *gossh.ServerConn, add bool) {
 		srv.connWg.Done()
 	}
 }
+
+func (srv *Server) SetSubsystemHandler(name string, handler SubsystemHandler) {
+	srv.SubsystemHandlers[name] = handler
+}

session.go

@@ -1,7 +1,6 @@
 package ssh
 
 import (
-	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -90,6 +89,8 @@ func sessionHandler(srv *Server, conn *gossh.ServerConn, newChan gossh.NewChanne
 		ptyCb:     srv.PtyCallback,
 		sessReqCb: srv.SessionRequestCallback,
 		ctx:       ctx,
+
+		subsystemHandlers: srv.SubsystemHandlers,
 	}
 	sess.handleRequests(reqs)
 }
@@ -110,21 +111,24 @@ type session struct {
 	ctx       Context
 	sigCh     chan<- Signal
 	sigBuf    []Signal
+
+	subsystemHandlers map[string]SubsystemHandler
 }
 
 func (sess *session) Write(p []byte) (n int, err error) {
-	if sess.pty != nil {
-		m := len(p)
-		// normalize \n to \r\n when pty is accepted.
-		// this is a hardcoded shortcut since we don't support terminal modes.
-		p = bytes.Replace(p, []byte{'\n'}, []byte{'\r', '\n'}, -1)
-		p = bytes.Replace(p, []byte{'\r', '\r', '\n'}, []byte{'\r', '\n'}, -1)
-		n, err = sess.Channel.Write(p)
-		if n > m {
-			n = m
-		}
-		return
-	}
+	// If change the \n to \r\n, then zmodem(rzsz) will be error
+	//if sess.pty != nil {
+	//	m := len(p)
+	//	// normalize \n to \r\n when pty is accepted.
+	//	// this is a hardcoded shortcut since we don't support terminal modes.
+	//	p = bytes.Replace(p, []byte{'\n'}, []byte{'\r', '\n'}, -1)
+	//	p = bytes.Replace(p, []byte{'\r', '\r', '\n'}, []byte{'\r', '\n'}, -1)
+	//	n, err = sess.Channel.Write(p)
+	//	if n > m {
+	//		n = m
+	//	}
+	//	return
+	//}
 	return sess.Channel.Write(p)
 }
 
@@ -292,6 +296,21 @@ func (sess *session) handleRequests(reqs <-chan *gossh.Request) {
 			// TODO: option/callback to allow agent forwarding
 			SetAgentRequested(sess.ctx)
 			req.Reply(true, nil)
+		case "subsystem":
+			subname := string(req.Payload[4:])
+			handler, ok := sess.subsystemHandlers[subname]
+			if !ok {
+				req.Reply(false, nil)
+				continue
+			}
+			sess.handled = true
+			req.Reply(true, nil)
+
+			go func() {
+				handler(sess)
+				sess.Exit(0)
+			}()
+
 		default:
 			// TODO: debug log
 			req.Reply(false, nil)

ssh.go

@@ -35,6 +35,9 @@ type Option func(*Server) error
 // Handler is a callback for handling established SSH sessions.
 type Handler func(Session)
 
+// SubsystemHandler is a callback for handling session subsystem request
+type SubsystemHandler func(Session)
+
 // PublicKeyHandler is a callback for performing public key authentication.
 type PublicKeyHandler func(ctx Context, key PublicKey) bool