647 lines
15 KiB
Go
647 lines
15 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssh
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// Session implements an interactive session described in
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// "RFC 4254, section 6".
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"sync"
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)
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type Signal string
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// POSIX signals as listed in RFC 4254 Section 6.10.
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const (
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SIGABRT Signal = "ABRT"
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SIGALRM Signal = "ALRM"
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SIGFPE Signal = "FPE"
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SIGHUP Signal = "HUP"
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SIGILL Signal = "ILL"
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SIGINT Signal = "INT"
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SIGKILL Signal = "KILL"
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SIGPIPE Signal = "PIPE"
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SIGQUIT Signal = "QUIT"
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SIGSEGV Signal = "SEGV"
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SIGTERM Signal = "TERM"
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SIGUSR1 Signal = "USR1"
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SIGUSR2 Signal = "USR2"
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)
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var signals = map[Signal]int{
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SIGABRT: 6,
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SIGALRM: 14,
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SIGFPE: 8,
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SIGHUP: 1,
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SIGILL: 4,
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SIGINT: 2,
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SIGKILL: 9,
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SIGPIPE: 13,
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SIGQUIT: 3,
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SIGSEGV: 11,
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SIGTERM: 15,
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}
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type TerminalModes map[uint8]uint32
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// POSIX terminal mode flags as listed in RFC 4254 Section 8.
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const (
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tty_OP_END = 0
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VINTR = 1
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VQUIT = 2
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VERASE = 3
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VKILL = 4
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VEOF = 5
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VEOL = 6
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VEOL2 = 7
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VSTART = 8
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VSTOP = 9
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VSUSP = 10
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VDSUSP = 11
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VREPRINT = 12
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VWERASE = 13
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VLNEXT = 14
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VFLUSH = 15
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VSWTCH = 16
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VSTATUS = 17
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VDISCARD = 18
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IGNPAR = 30
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PARMRK = 31
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INPCK = 32
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ISTRIP = 33
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INLCR = 34
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IGNCR = 35
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ICRNL = 36
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IUCLC = 37
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IXON = 38
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IXANY = 39
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IXOFF = 40
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IMAXBEL = 41
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ISIG = 50
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ICANON = 51
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XCASE = 52
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ECHO = 53
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ECHOE = 54
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ECHOK = 55
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ECHONL = 56
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NOFLSH = 57
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TOSTOP = 58
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IEXTEN = 59
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ECHOCTL = 60
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ECHOKE = 61
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PENDIN = 62
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OPOST = 70
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OLCUC = 71
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ONLCR = 72
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OCRNL = 73
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ONOCR = 74
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ONLRET = 75
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CS7 = 90
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CS8 = 91
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PARENB = 92
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PARODD = 93
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TTY_OP_ISPEED = 128
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TTY_OP_OSPEED = 129
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)
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// A Session represents a connection to a remote command or shell.
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type Session struct {
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// Stdin specifies the remote process's standard input.
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// If Stdin is nil, the remote process reads from an empty
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// bytes.Buffer.
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Stdin io.Reader
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// Stdout and Stderr specify the remote process's standard
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// output and error.
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//
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// If either is nil, Run connects the corresponding file
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// descriptor to an instance of ioutil.Discard. There is a
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// fixed amount of buffering that is shared for the two streams.
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// If either blocks it may eventually cause the remote
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// command to block.
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Stdout io.Writer
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Stderr io.Writer
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ch Channel // the channel backing this session
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started bool // true once Start, Run or Shell is invoked.
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copyFuncs []func() error
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errors chan error // one send per copyFunc
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// true if pipe method is active
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stdinpipe, stdoutpipe, stderrpipe bool
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// stdinPipeWriter is non-nil if StdinPipe has not been called
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// and Stdin was specified by the user; it is the write end of
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// a pipe connecting Session.Stdin to the stdin channel.
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stdinPipeWriter io.WriteCloser
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exitStatus chan error
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}
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// SendRequest sends an out-of-band channel request on the SSH channel
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// underlying the session.
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func (s *Session) SendRequest(name string, wantReply bool, payload []byte) (bool, error) {
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return s.ch.SendRequest(name, wantReply, payload)
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}
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func (s *Session) Close() error {
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return s.ch.Close()
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}
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// RFC 4254 Section 6.4.
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type setenvRequest struct {
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Name string
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Value string
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}
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// Setenv sets an environment variable that will be applied to any
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// command executed by Shell or Run.
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func (s *Session) Setenv(name, value string) error {
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msg := setenvRequest{
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Name: name,
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Value: value,
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}
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ok, err := s.ch.SendRequest("env", true, Marshal(&msg))
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if err == nil && !ok {
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err = errors.New("ssh: setenv failed")
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}
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return err
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}
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// RFC 4254 Section 6.2.
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type ptyRequestMsg struct {
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Term string
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Columns uint32
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Rows uint32
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Width uint32
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Height uint32
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Modelist string
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}
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// RequestPty requests the association of a pty with the session on the remote host.
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func (s *Session) RequestPty(term string, h, w int, termmodes TerminalModes) error {
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var tm []byte
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for k, v := range termmodes {
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kv := struct {
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Key byte
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Val uint32
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}{k, v}
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tm = append(tm, Marshal(&kv)...)
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}
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tm = append(tm, tty_OP_END)
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req := ptyRequestMsg{
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Term: term,
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Columns: uint32(w),
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Rows: uint32(h),
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Width: uint32(w * 8),
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Height: uint32(h * 8),
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Modelist: string(tm),
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}
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ok, err := s.ch.SendRequest("pty-req", true, Marshal(&req))
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if err == nil && !ok {
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err = errors.New("ssh: pty-req failed")
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}
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return err
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}
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// RFC 4254 Section 6.5.
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type subsystemRequestMsg struct {
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Subsystem string
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}
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// RequestSubsystem requests the association of a subsystem with the session on the remote host.
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// A subsystem is a predefined command that runs in the background when the ssh session is initiated
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func (s *Session) RequestSubsystem(subsystem string) error {
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msg := subsystemRequestMsg{
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Subsystem: subsystem,
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}
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ok, err := s.ch.SendRequest("subsystem", true, Marshal(&msg))
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if err == nil && !ok {
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err = errors.New("ssh: subsystem request failed")
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}
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return err
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}
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// RFC 4254 Section 6.7.
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type ptyWindowChangeMsg struct {
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Columns uint32
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Rows uint32
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Width uint32
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Height uint32
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}
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// WindowChange informs the remote host about a terminal window dimension change to h rows and w columns.
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func (s *Session) WindowChange(h, w int) error {
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req := ptyWindowChangeMsg{
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Columns: uint32(w),
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Rows: uint32(h),
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Width: uint32(w * 8),
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Height: uint32(h * 8),
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}
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_, err := s.ch.SendRequest("window-change", false, Marshal(&req))
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return err
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}
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// RFC 4254 Section 6.9.
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type signalMsg struct {
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Signal string
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}
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// Signal sends the given signal to the remote process.
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// sig is one of the SIG* constants.
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func (s *Session) Signal(sig Signal) error {
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msg := signalMsg{
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Signal: string(sig),
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}
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_, err := s.ch.SendRequest("signal", false, Marshal(&msg))
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return err
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}
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// RFC 4254 Section 6.5.
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type execMsg struct {
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Command string
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}
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// Start runs cmd on the remote host. Typically, the remote
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// server passes cmd to the shell for interpretation.
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// A Session only accepts one call to Run, Start or Shell.
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func (s *Session) Start(cmd string) error {
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if s.started {
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return errors.New("ssh: session already started")
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}
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req := execMsg{
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Command: cmd,
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}
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ok, err := s.ch.SendRequest("exec", true, Marshal(&req))
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if err == nil && !ok {
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err = fmt.Errorf("ssh: command %v failed", cmd)
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}
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if err != nil {
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return err
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}
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return s.start()
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}
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// Run runs cmd on the remote host. Typically, the remote
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// server passes cmd to the shell for interpretation.
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// A Session only accepts one call to Run, Start, Shell, Output,
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// or CombinedOutput.
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//
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// The returned error is nil if the command runs, has no problems
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// copying stdin, stdout, and stderr, and exits with a zero exit
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// status.
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//
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// If the remote server does not send an exit status, an error of type
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// *ExitMissingError is returned. If the command completes
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// unsuccessfully or is interrupted by a signal, the error is of type
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// *ExitError. Other error types may be returned for I/O problems.
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func (s *Session) Run(cmd string) error {
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err := s.Start(cmd)
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if err != nil {
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return err
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}
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return s.Wait()
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}
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// Output runs cmd on the remote host and returns its standard output.
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func (s *Session) Output(cmd string) ([]byte, error) {
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if s.Stdout != nil {
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return nil, errors.New("ssh: Stdout already set")
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}
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var b bytes.Buffer
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s.Stdout = &b
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err := s.Run(cmd)
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return b.Bytes(), err
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}
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type singleWriter struct {
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b bytes.Buffer
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mu sync.Mutex
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}
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func (w *singleWriter) Write(p []byte) (int, error) {
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w.mu.Lock()
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defer w.mu.Unlock()
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return w.b.Write(p)
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}
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// CombinedOutput runs cmd on the remote host and returns its combined
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// standard output and standard error.
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func (s *Session) CombinedOutput(cmd string) ([]byte, error) {
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if s.Stdout != nil {
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return nil, errors.New("ssh: Stdout already set")
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}
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if s.Stderr != nil {
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return nil, errors.New("ssh: Stderr already set")
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}
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var b singleWriter
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s.Stdout = &b
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s.Stderr = &b
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err := s.Run(cmd)
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return b.b.Bytes(), err
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}
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// Shell starts a login shell on the remote host. A Session only
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// accepts one call to Run, Start, Shell, Output, or CombinedOutput.
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func (s *Session) Shell() error {
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if s.started {
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return errors.New("ssh: session already started")
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}
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ok, err := s.ch.SendRequest("shell", true, nil)
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if err == nil && !ok {
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return errors.New("ssh: could not start shell")
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}
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if err != nil {
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return err
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}
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return s.start()
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}
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func (s *Session) start() error {
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s.started = true
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type F func(*Session)
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for _, setupFd := range []F{(*Session).stdin, (*Session).stdout, (*Session).stderr} {
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setupFd(s)
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}
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s.errors = make(chan error, len(s.copyFuncs))
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for _, fn := range s.copyFuncs {
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go func(fn func() error) {
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s.errors <- fn()
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}(fn)
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}
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return nil
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}
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// Wait waits for the remote command to exit.
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//
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// The returned error is nil if the command runs, has no problems
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// copying stdin, stdout, and stderr, and exits with a zero exit
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// status.
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//
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// If the remote server does not send an exit status, an error of type
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// *ExitMissingError is returned. If the command completes
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// unsuccessfully or is interrupted by a signal, the error is of type
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// *ExitError. Other error types may be returned for I/O problems.
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func (s *Session) Wait() error {
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if !s.started {
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return errors.New("ssh: session not started")
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}
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waitErr := <-s.exitStatus
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if s.stdinPipeWriter != nil {
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s.stdinPipeWriter.Close()
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}
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var copyError error
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for _ = range s.copyFuncs {
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if err := <-s.errors; err != nil && copyError == nil {
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copyError = err
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}
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}
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if waitErr != nil {
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return waitErr
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}
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return copyError
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}
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func (s *Session) wait(reqs <-chan *Request) error {
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wm := Waitmsg{status: -1}
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// Wait for msg channel to be closed before returning.
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for msg := range reqs {
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switch msg.Type {
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case "exit-status":
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wm.status = int(binary.BigEndian.Uint32(msg.Payload))
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case "exit-signal":
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var sigval struct {
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Signal string
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CoreDumped bool
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Error string
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Lang string
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}
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if err := Unmarshal(msg.Payload, &sigval); err != nil {
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return err
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}
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// Must sanitize strings?
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wm.signal = sigval.Signal
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wm.msg = sigval.Error
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wm.lang = sigval.Lang
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default:
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// This handles keepalives and matches
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// OpenSSH's behaviour.
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if msg.WantReply {
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msg.Reply(false, nil)
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}
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}
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}
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if wm.status == 0 {
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return nil
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}
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if wm.status == -1 {
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// exit-status was never sent from server
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if wm.signal == "" {
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// signal was not sent either. RFC 4254
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// section 6.10 recommends against this
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// behavior, but it is allowed, so we let
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// clients handle it.
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return &ExitMissingError{}
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}
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wm.status = 128
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if _, ok := signals[Signal(wm.signal)]; ok {
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wm.status += signals[Signal(wm.signal)]
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}
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}
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return &ExitError{wm}
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}
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// ExitMissingError is returned if a session is torn down cleanly, but
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// the server sends no confirmation of the exit status.
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type ExitMissingError struct{}
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func (e *ExitMissingError) Error() string {
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return "wait: remote command exited without exit status or exit signal"
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}
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func (s *Session) stdin() {
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if s.stdinpipe {
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return
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}
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var stdin io.Reader
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if s.Stdin == nil {
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stdin = new(bytes.Buffer)
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} else {
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r, w := io.Pipe()
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go func() {
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_, err := io.Copy(w, s.Stdin)
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w.CloseWithError(err)
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}()
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stdin, s.stdinPipeWriter = r, w
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}
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s.copyFuncs = append(s.copyFuncs, func() error {
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_, err := io.Copy(s.ch, stdin)
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if err1 := s.ch.CloseWrite(); err == nil && err1 != io.EOF {
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err = err1
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}
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return err
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})
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}
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func (s *Session) stdout() {
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if s.stdoutpipe {
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return
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}
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if s.Stdout == nil {
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s.Stdout = ioutil.Discard
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}
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s.copyFuncs = append(s.copyFuncs, func() error {
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_, err := io.Copy(s.Stdout, s.ch)
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return err
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})
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}
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func (s *Session) stderr() {
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if s.stderrpipe {
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return
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}
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if s.Stderr == nil {
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s.Stderr = ioutil.Discard
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}
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s.copyFuncs = append(s.copyFuncs, func() error {
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_, err := io.Copy(s.Stderr, s.ch.Stderr())
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return err
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})
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}
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// sessionStdin reroutes Close to CloseWrite.
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type sessionStdin struct {
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io.Writer
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ch Channel
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}
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func (s *sessionStdin) Close() error {
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return s.ch.CloseWrite()
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}
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// StdinPipe returns a pipe that will be connected to the
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// remote command's standard input when the command starts.
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func (s *Session) StdinPipe() (io.WriteCloser, error) {
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if s.Stdin != nil {
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return nil, errors.New("ssh: Stdin already set")
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}
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if s.started {
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return nil, errors.New("ssh: StdinPipe after process started")
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}
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s.stdinpipe = true
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return &sessionStdin{s.ch, s.ch}, nil
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}
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// StdoutPipe returns a pipe that will be connected to the
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// remote command's standard output when the command starts.
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// There is a fixed amount of buffering that is shared between
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// stdout and stderr streams. If the StdoutPipe reader is
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// not serviced fast enough it may eventually cause the
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// remote command to block.
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func (s *Session) StdoutPipe() (io.Reader, error) {
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if s.Stdout != nil {
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return nil, errors.New("ssh: Stdout already set")
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}
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if s.started {
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return nil, errors.New("ssh: StdoutPipe after process started")
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}
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s.stdoutpipe = true
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return s.ch, nil
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}
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// StderrPipe returns a pipe that will be connected to the
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// remote command's standard error when the command starts.
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// There is a fixed amount of buffering that is shared between
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// stdout and stderr streams. If the StderrPipe reader is
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|
// 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
|
|
}
|