aboutsummaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/crypto/ssh/session.go
blob: d3321f6b784b580fddbd7d3f1d4a6ca21b42e497 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ssh

// Session implements an interactive session described in
// "RFC 4254, section 6".

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"sync"
)

type Signal string

// POSIX signals as listed in RFC 4254 Section 6.10.
const (
	SIGABRT Signal = "ABRT"
	SIGALRM Signal = "ALRM"
	SIGFPE  Signal = "FPE"
	SIGHUP  Signal = "HUP"
	SIGILL  Signal = "ILL"
	SIGINT  Signal = "INT"
	SIGKILL Signal = "KILL"
	SIGPIPE Signal = "PIPE"
	SIGQUIT Signal = "QUIT"
	SIGSEGV Signal = "SEGV"
	SIGTERM Signal = "TERM"
	SIGUSR1 Signal = "USR1"
	SIGUSR2 Signal = "USR2"
)

var signals = map[Signal]int{
	SIGABRT: 6,
	SIGALRM: 14,
	SIGFPE:  8,
	SIGHUP:  1,
	SIGILL:  4,
	SIGINT:  2,
	SIGKILL: 9,
	SIGPIPE: 13,
	SIGQUIT: 3,
	SIGSEGV: 11,
	SIGTERM: 15,
}

type TerminalModes map[uint8]uint32

// POSIX terminal mode flags as listed in RFC 4254 Section 8.
const (
	tty_OP_END    = 0
	VINTR         = 1
	VQUIT         = 2
	VERASE        = 3
	VKILL         = 4
	VEOF          = 5
	VEOL          = 6
	VEOL2         = 7
	VSTART        = 8
	VSTOP         = 9
	VSUSP         = 10
	VDSUSP        = 11
	VREPRINT      = 12
	VWERASE       = 13
	VLNEXT        = 14
	VFLUSH        = 15
	VSWTCH        = 16
	VSTATUS       = 17
	VDISCARD      = 18
	IGNPAR        = 30
	PARMRK        = 31
	INPCK         = 32
	ISTRIP        = 33
	INLCR         = 34
	IGNCR         = 35
	ICRNL         = 36
	IUCLC         = 37
	IXON          = 38
	IXANY         = 39
	IXOFF         = 40
	IMAXBEL       = 41
	ISIG          = 50
	ICANON        = 51
	XCASE         = 52
	ECHO          = 53
	ECHOE         = 54
	ECHOK         = 55
	ECHONL        = 56
	NOFLSH        = 57
	TOSTOP        = 58
	IEXTEN        = 59
	ECHOCTL       = 60
	ECHOKE        = 61
	PENDIN        = 62
	OPOST         = 70
	OLCUC         = 71
	ONLCR         = 72
	OCRNL         = 73
	ONOCR         = 74
	ONLRET        = 75
	CS7           = 90
	CS8           = 91
	PARENB        = 92
	PARODD        = 93
	TTY_OP_ISPEED = 128
	TTY_OP_OSPEED = 129
)

// A Session represents a connection to a remote command or shell.
type Session struct {
	// Stdin specifies the remote process's standard input.
	// If Stdin is nil, the remote process reads from an empty
	// bytes.Buffer.
	Stdin io.Reader

	// Stdout and Stderr specify the remote process's standard
	// output and error.
	//
	// If either is nil, Run connects the corresponding file
	// descriptor to an instance of ioutil.Discard. There is a
	// fixed amount of buffering that is shared for the two streams.
	// If either blocks it may eventually cause the remote
	// command to block.
	Stdout io.Writer
	Stderr io.Writer

	ch        Channel // the channel backing this session
	started   bool    // true once Start, Run or Shell is invoked.
	copyFuncs []func() error
	errors    chan error // one send per copyFunc

	// true if pipe method is active
	stdinpipe, stdoutpipe, stderrpipe bool

	// stdinPipeWriter is non-nil if StdinPipe has not been called
	// and Stdin was specified by the user; it is the write end of
	// a pipe connecting Session.Stdin to the stdin channel.
	stdinPipeWriter io.WriteCloser

	exitStatus chan error
}

// SendRequest sends an out-of-band channel request on the SSH channel
// underlying the session.
func (s *Session) SendRequest(name string, wantReply bool, payload []byte) (bool, error) {
	return s.ch.SendRequest(name, wantReply, payload)
}

func (s *Session) Close() error {
	return s.ch.Close()
}

// RFC 4254 Section 6.4.
type setenvRequest struct {
	Name  string
	Value string
}

// Setenv sets an environment variable that will be applied to any
// command executed by Shell or Run.
func (s *Session) Setenv(name, value string) error {
	msg := setenvRequest{
		Name:  name,
		Value: value,
	}
	ok, err := s.ch.SendRequest("env", true, Marshal(&msg))
	if err == nil && !ok {
		err = errors.New("ssh: setenv failed")
	}
	return err
}

// RFC 4254 Section 6.2.
type ptyRequestMsg struct {
	Term     string
	Columns  uint32
	Rows     uint32
	Width    uint32
	Height   uint32
	Modelist string
}

// RequestPty requests the association of a pty with the session on the remote host.
func (s *Session) RequestPty(term string, h, w int, termmodes TerminalModes) error {
	var tm []byte
	for k, v := range termmodes {
		kv := struct {
			Key byte
			Val uint32
		}{k, v}

		tm = append(tm, Marshal(&kv)...)
	}
	tm = append(tm, tty_OP_END)
	req := ptyRequestMsg{
		Term:     term,
		Columns:  uint32(w),
		Rows:     uint32(h),
		Width:    uint32(w * 8),
		Height:   uint32(h * 8),
		Modelist: string(tm),
	}
	ok, err := s.ch.SendRequest("pty-req", true, Marshal(&req))
	if err == nil && !ok {
		err = errors.New("ssh: pty-req failed")
	}
	return err
}

// RFC 4254 Section 6.5.
type subsystemRequestMsg struct {
	Subsystem string
}

// RequestSubsystem requests the association of a subsystem with the session on the remote host.
// A subsystem is a predefined command that runs in the background when the ssh session is initiated
func (s *Session) RequestSubsystem(subsystem string) error {
	msg := subsystemRequestMsg{
		Subsystem: subsystem,
	}
	ok, err := s.ch.SendRequest("subsystem", true, Marshal(&msg))
	if err == nil && !ok {
		err = errors.New("ssh: subsystem request failed")
	}
	return err
}

// RFC 4254 Section 6.7.
type ptyWindowChangeMsg struct {
	Columns uint32
	Rows    uint32
	Width   uint32
	Height  uint32
}

// WindowChange informs the remote host about a terminal window dimension change to h rows and w columns.
func (s *Session) WindowChange(h, w int) error {
	req := ptyWindowChangeMsg{
		Columns: uint32(w),
		Rows:    uint32(h),
		Width:   uint32(w * 8),
		Height:  uint32(h * 8),
	}
	_, err := s.ch.SendRequest("window-change", false, Marshal(&req))
	return err
}

// RFC 4254 Section 6.9.
type signalMsg struct {
	Signal string
}

// Signal sends the given signal to the remote process.
// sig is one of the SIG* constants.
func (s *Session) Signal(sig Signal) error {
	msg := signalMsg{
		Signal: string(sig),
	}

	_, err := s.ch.SendRequest("signal", false, Marshal(&msg))
	return err
}

// RFC 4254 Section 6.5.
type execMsg struct {
	Command string
}

// Start runs cmd on the remote host. Typically, the remote
// server passes cmd to the shell for interpretation.
// A Session only accepts one call to Run, Start or Shell.
func (s *Session) Start(cmd string) error {
	if s.started {
		return errors.New("ssh: session already started")
	}
	req := execMsg{
		Command: cmd,
	}

	ok, err := s.ch.SendRequest("exec", true, Marshal(&req))
	if err == nil && !ok {
		err = fmt.Errorf("ssh: command %v failed", cmd)
	}
	if err != nil {
		return err
	}
	return s.start()
}

// Run runs cmd on the remote host. Typically, the remote
// server passes cmd to the shell for interpretation.
// A Session only accepts one call to Run, Start, Shell, Output,
// or CombinedOutput.
//
// The returned error is nil if the command runs, has no problems
// copying stdin, stdout, and stderr, and exits with a zero exit
// status.
//
// If the remote server does not send an exit status, an error of type
// *ExitMissingError is returned. If the command completes
// unsuccessfully or is interrupted by a signal, the error is of type
// *ExitError. Other error types may be returned for I/O problems.
func (s *Session) Run(cmd string) error {
	err := s.Start(cmd)
	if err != nil {
		return err
	}
	return s.Wait()
}

// Output runs cmd on the remote host and returns its standard output.
func (s *Session) Output(cmd string) ([]byte, error) {
	if s.Stdout != nil {
		return nil, errors.New("ssh: Stdout already set")
	}
	var b bytes.Buffer
	s.Stdout = &b
	err := s.Run(cmd)
	return b.Bytes(), err
}

type singleWriter struct {
	b  bytes.Buffer
	mu sync.Mutex
}

func (w *singleWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	return w.b.Write(p)
}

// CombinedOutput runs cmd on the remote host and returns its combined
// standard output and standard error.
func (s *Session) CombinedOutput(cmd string) ([]byte, error) {
	if s.Stdout != nil {
		return nil, errors.New("ssh: Stdout already set")
	}
	if s.Stderr != nil {
		return nil, errors.New("ssh: Stderr already set")
	}
	var b singleWriter
	s.Stdout = &b
	s.Stderr = &b
	err := s.Run(cmd)
	return b.b.Bytes(), err
}

// Shell starts a login shell on the remote host. A Session only
// accepts one call to Run, Start, Shell, Output, or CombinedOutput.
func (s *Session) Shell() error {
	if s.started {
		return errors.New("ssh: session already started")
	}

	ok, err := s.ch.SendRequest("shell", true, nil)
	if err == nil && !ok {
		return errors.New("ssh: could not start shell")
	}
	if err != nil {
		return err
	}
	return s.start()
}

func (s *Session) start() error {
	s.started = true

	type F func(*Session)
	for _, setupFd := range []F{(*Session).stdin, (*Session).stdout, (*Session).stderr} {
		setupFd(s)
	}

	s.errors = make(chan error, len(s.copyFuncs))
	for _, fn := range s.copyFuncs {
		go func(fn func() error) {
			s.errors <- fn()
		}(fn)
	}
	return nil
}

// Wait waits for the remote command to exit.
//
// The returned error is nil if the command runs, has no problems
// copying stdin, stdout, and stderr, and exits with a zero exit
// status.
//
// If the remote server does not send an exit status, an error of type
// *ExitMissingError is returned. If the command completes
// unsuccessfully or is interrupted by a signal, the error is of type
// *ExitError. Other error types may be returned for I/O problems.
func (s *Session) Wait() error {
	if !s.started {
		return errors.New("ssh: session not started")
	}
	waitErr := <-s.exitStatus

	if s.stdinPipeWriter != nil {
		s.stdinPipeWriter.Close()
	}
	var copyError error
	for range s.copyFuncs {
		if err := <-s.errors; err != nil && copyError == nil {
			copyError = err
		}
	}
	if waitErr != nil {
		return waitErr
	}
	return copyError
}

func (s *Session) wait(reqs <-chan *Request) error {
	wm := Waitmsg{status: -1}
	// Wait for msg channel to be closed before returning.
	for msg := range reqs {
		switch msg.Type {
		case "exit-status":
			wm.status = int(binary.BigEndian.Uint32(msg.Payload))
		case "exit-signal":
			var sigval struct {
				Signal     string
				CoreDumped bool
				Error      string
				Lang       string
			}
			if err := Unmarshal(msg.Payload, &sigval); err != nil {
				return err
			}

			// Must sanitize strings?
			wm.signal = sigval.Signal
			wm.msg = sigval.Error
			wm.lang = sigval.Lang
		default:
			// This handles keepalives and matches
			// OpenSSH's behaviour.
			if msg.WantReply {
				msg.Reply(false, nil)
			}
		}
	}
	if wm.status == 0 {
		return nil
	}
	if wm.status == -1 {
		// exit-status was never sent from server
		if wm.signal == "" {
			// signal was not sent either.  RFC 4254
			// section 6.10 recommends against this
			// behavior, but it is allowed, so we let
			// clients handle it.
			return &ExitMissingError{}
		}
		wm.status = 128
		if _, ok := signals[Signal(wm.signal)]; ok {
			wm.status += signals[Signal(wm.signal)]
		}
	}

	return &ExitError{wm}
}

// ExitMissingError is returned if a session is torn down cleanly, but
// the server sends no confirmation of the exit status.
type ExitMissingError struct{}

func (e *ExitMissingError) Error() string {
	return "wait: remote command exited without exit status or exit signal"
}

func (s *Session) stdin() {
	if s.stdinpipe {
		return
	}
	var stdin io.Reader
	if s.Stdin == nil {
		stdin = new(bytes.Buffer)
	} else {
		r, w := io.Pipe()
		go func() {
			_, err := io.Copy(w, s.Stdin)
			w.CloseWithError(err)
		}()
		stdin, s.stdinPipeWriter = r, w
	}
	s.copyFuncs = append(s.copyFuncs, func() error {
		_, err := io.Copy(s.ch, stdin)
		if err1 := s.ch.CloseWrite(); err == nil && err1 != io.EOF {
			err = err1
		}
		return err
	})
}

func (s *Session) stdout() {
	if s.stdoutpipe {
		return
	}
	if s.Stdout == nil {
		s.Stdout = ioutil.Discard
	}
	s.copyFuncs = append(s.copyFuncs, func() error {
		_, err := io.Copy(s.Stdout, s.ch)
		return err
	})
}

func (s *Session) stderr() {
	if s.stderrpipe {
		return
	}
	if s.Stderr == nil {
		s.Stderr = ioutil.Discard
	}
	s.copyFuncs = append(s.copyFuncs, func() error {
		_, err := io.Copy(s.Stderr, s.ch.Stderr())
		return err
	})
}

// sessionStdin reroutes Close to CloseWrite.
type sessionStdin struct {
	io.Writer
	ch Channel
}

func (s *sessionStdin) Close() error {
	return s.ch.CloseWrite()
}

// StdinPipe returns a pipe that will be connected to the
// remote command's standard input when the command starts.
func (s *Session) StdinPipe() (io.WriteCloser, error) {
	if s.Stdin != nil {
		return nil, errors.New("ssh: Stdin already set")
	}
	if s.started {
		return nil, errors.New("ssh: StdinPipe after process started")
	}
	s.stdinpipe = true
	return &sessionStdin{s.ch, s.ch}, nil
}

// StdoutPipe returns a pipe that will be connected to the
// remote command's standard output when the command starts.
// There is a fixed amount of buffering that is shared between
// stdout and stderr streams. If the StdoutPipe reader is
// not serviced fast enough it may eventually cause the
// remote command to block.
func (s *Session) StdoutPipe() (io.Reader, error) {
	if s.Stdout != nil {
		return nil, errors.New("ssh: Stdout already set")
	}
	if s.started {
		return nil, errors.New("ssh: StdoutPipe after process started")
	}
	s.stdoutpipe = true
	return s.ch, nil
}

// StderrPipe returns a pipe that will be connected to the
// remote command's standard error when the command starts.
// There is a fixed amount of buffering that is shared between
// stdout and stderr streams. If the StderrPipe reader is
// not serviced fast enough it may eventually cause the
// remote command to block.
func (s *Session) StderrPipe() (io.Reader, error) {
	if s.Stderr != nil {
		return nil, errors.New("ssh: Stderr already set")
	}
	if s.started {
		return nil, errors.New("ssh: StderrPipe after process started")
	}
	s.stderrpipe = true
	return s.ch.Stderr(), nil
}

// newSession returns a new interactive session on the remote host.
func newSession(ch Channel, reqs <-chan *Request) (*Session, error) {
	s := &Session{
		ch: ch,
	}
	s.exitStatus = make(chan error, 1)
	go func() {
		s.exitStatus <- s.wait(reqs)
	}()

	return s, nil
}

// An ExitError reports unsuccessful completion of a remote command.
type ExitError struct {
	Waitmsg
}

func (e *ExitError) Error() string {
	return e.Waitmsg.String()
}

// Waitmsg stores the information about an exited remote command
// as reported by Wait.
type Waitmsg struct {
	status int
	signal string
	msg    string
	lang   string
}

// ExitStatus returns the exit status of the remote command.
func (w Waitmsg) ExitStatus() int {
	return w.status
}

// Signal returns the exit signal of the remote command if
// it was terminated violently.
func (w Waitmsg) Signal() string {
	return w.signal
}

// Msg returns the exit message given by the remote command
func (w Waitmsg) Msg() string {
	return w.msg
}

// Lang returns the language tag. See RFC 3066
func (w Waitmsg) Lang() string {
	return w.lang
}

func (w Waitmsg) String() string {
	str := fmt.Sprintf("Process exited with status %v", w.status)
	if w.signal != "" {
		str += fmt.Sprintf(" from signal %v", w.signal)
	}
	if w.msg != "" {
		str += fmt.Sprintf(". Reason was: %v", w.msg)
	}
	return str
}