fix(ssh): allow multiplexed connection

ssh/server/channels/session.go

@@ -175,21 +175,6 @@ func DefaultSessionHandler(opts DefaultSessionHandlerOptions) gliderssh.ChannelH
 
 				switch req.Type {
 				case ShellRequestType, ExecRequestType, SubsystemRequestType:
-					// Once the session has been set up, a program is started at the remote end.  The program can be a
-					// shell, an application program, or a subsystem with a host-independent name.  **Only one of these
-					// requests can succeed per channel.**
-					//
-					// https://www.rfc-editor.org/rfc/rfc4254#section-6.5
-					if sess.Handled {
-						logger.Warn("fail to start a new session before ending the previous one")
-
-						if err := req.Reply(false, nil); err != nil {
-							logger.WithError(err).Error("failed to reply the client when data pipe already started")
-						}
-
-						continue
-					}
-
 					if err := req.Reply(ok, nil); err != nil {
 						logger.WithError(err).Error("failed to reply the client with right response for pipe request type")
 
@@ -209,7 +194,7 @@ func DefaultSessionHandler(opts DefaultSessionHandlerOptions) gliderssh.ChannelH
 					// encrypted tunnel.
 					//
 					// https://www.rfc-editor.org/rfc/rfc4254#section-6.5
-					go pipe(ctx, sess, client, agent, req.Type, opts)
+					go pipe(sess, client, agent, req.Type, opts)
 				case PtyRequestType:
 					var pty session.Pty
 

ssh/server/channels/utils.go

@@ -5,26 +5,14 @@ import (
 	"io"
 	"sync"
 
-	gliderssh "github.com/gliderlabs/ssh"
 	"github.com/shellhub-io/shellhub/pkg/envs"
 	"github.com/shellhub-io/shellhub/pkg/models"
 	"github.com/shellhub-io/shellhub/ssh/session"
 	log "github.com/sirupsen/logrus"
 	gossh "golang.org/x/crypto/ssh"
 )
 
-func pipe(ctx gliderssh.Context, sess *session.Session, client gossh.Channel, agent gossh.Channel, req string, opts DefaultSessionHandlerOptions) {
-	defer func() {
-		ctx.Lock()
-		sess.Handled = false
-		ctx.Unlock()
-	}()
-
-	// NOTICE: avoid multiple pipe data in same channel due to protocol limitaion.
-	ctx.Lock()
-	sess.Handled = true
-	ctx.Unlock()
-
+func pipe(sess *session.Session, client gossh.Channel, agent gossh.Channel, req string, opts DefaultSessionHandlerOptions) {
 	defer log.
 		WithFields(log.Fields{"session": sess.UID, "sshid": sess.SSHID}).
 		Trace("data pipe between client and agent has done")

ssh/session/session.go

@@ -54,8 +54,6 @@ type Data struct {
 	Lookup map[string]string
 	// Pty is the PTY dimension.
 	Pty Pty
-	// Handled check if the session is already handling a "shell", "exec" or a "subsystem".
-	Handled bool
 }
 
 // TODO: implement [io.Read] and [io.Write] on session to simplify the data piping.