Initial commit

application/commands/telnet.go

@@ -0,0 +1,204 @@
+// Sshwifty - A Web SSH client
+//
+// Copyright (C) 2019 Rui NI <nirui@gmx.com>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package commands
+
+import (
+	"errors"
+	"io"
+	"sync"
+	"time"
+
+	"github.com/niruix/sshwifty/application/command"
+	"github.com/niruix/sshwifty/application/log"
+	"github.com/niruix/sshwifty/application/network"
+	"github.com/niruix/sshwifty/application/rw"
+)
+
+// Errors
+var (
+	ErrTelnetUnableToReceiveRemoteConn = errors.New(
+		"Unable to acquire remote connection handle")
+)
+
+// Error codes
+const (
+	TelnetRequestErrorBadRemoteAddress = command.StreamError(0x01)
+)
+
+// Server signal codes
+const (
+	TelnetServerRemoteBand    = 0x00
+	TelnetServerDialFailed    = 0x01
+	TelnetServerDialConnected = 0x02
+)
+
+type telnetClient struct {
+	l           log.Logger
+	w           command.StreamResponder
+	dial        network.Dial
+	remoteChan  chan io.WriteCloser
+	remoteConn  io.WriteCloser
+	closeWait   sync.WaitGroup
+	dialTimeout time.Duration
+}
+
+func newTelnet(
+	l log.Logger,
+	w command.StreamResponder,
+	dial network.Dial,
+) command.FSMMachine {
+	return &telnetClient{
+		l:           l,
+		w:           w,
+		dial:        dial,
+		remoteChan:  make(chan io.WriteCloser, 1),
+		remoteConn:  nil,
+		closeWait:   sync.WaitGroup{},
+		dialTimeout: 10 * time.Second,
+	}
+}
+
+func (d *telnetClient) Bootup(
+	r *rw.LimitedReader,
+	b []byte) (command.FSMState, command.FSMError) {
+	addr, addrErr := ParseAddress(r.Read, b)
+
+	if addrErr != nil {
+		return nil, command.ToFSMError(
+			addrErr, TelnetRequestErrorBadRemoteAddress)
+	}
+
+	// TODO: Test whether or not the address is allowed
+
+	d.closeWait.Add(1)
+	go d.remote(addr.String())
+
+	return d.client, command.NoFSMError()
+}
+
+func (d *telnetClient) remote(addr string) {
+	defer func() {
+		d.w.Signal(command.HeaderClose)
+
+		close(d.remoteChan)
+		d.closeWait.Done()
+	}()
+
+	buf := [4096]byte{}
+
+	clientConn, clientConnErr := d.dial("tcp", addr, d.dialTimeout)
+
+	if clientConnErr != nil {
+		errLen := copy(
+			buf[d.w.HeaderSize():], clientConnErr.Error()) + d.w.HeaderSize()
+		d.w.SendManual(TelnetServerDialFailed, buf[:errLen])
+
+		return
+	}
+
+	defer clientConn.Close()
+
+	clientConnErr = d.w.SendManual(
+		TelnetServerDialConnected,
+		buf[:d.w.HeaderSize()],
+	)
+
+	if clientConnErr != nil {
+		return
+	}
+
+	d.remoteChan <- clientConn
+
+	for {
+		rLen, rErr := clientConn.Read(buf[d.w.HeaderSize():])
+
+		if rErr != nil {
+			return
+		}
+
+		wErr := d.w.SendManual(
+			TelnetServerRemoteBand, buf[:rLen+d.w.HeaderSize()])
+
+		if wErr != nil {
+			return
+		}
+	}
+}
+
+func (d *telnetClient) getRemote() (io.WriteCloser, error) {
+	if d.remoteConn != nil {
+		return d.remoteConn, nil
+	}
+
+	remoteConn, ok := <-d.remoteChan
+
+	if !ok {
+		return nil, ErrTelnetUnableToReceiveRemoteConn
+	}
+
+	d.remoteConn = remoteConn
+
+	return d.remoteConn, nil
+}
+
+func (d *telnetClient) client(
+	f *command.FSM,
+	r *rw.LimitedReader,
+	h command.StreamHeader,
+	b []byte,
+) error {
+	remoteConn, remoteConnErr := d.getRemote()
+
+	if remoteConnErr != nil {
+		return remoteConnErr
+	}
+
+	// All Telnet requests are in-band, so we just directly send them all
+	// to the server
+	for !r.Completed() {
+		rBuf, rErr := r.Buffered()
+
+		if rErr != nil {
+			return rErr
+		}
+
+		_, wErr := remoteConn.Write(rBuf)
+
+		if wErr != nil {
+			return wErr
+		}
+	}
+
+	return nil
+}
+
+func (d *telnetClient) Close() error {
+	remoteConn, remoteConnErr := d.getRemote()
+
+	if remoteConnErr == nil {
+		remoteConn.Close()
+	}
+
+	d.closeWait.Wait()
+
+	return nil
+}
+
+func (d *telnetClient) Release() error {
+	return nil
+}