| // 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" |
| "errors" |
| "fmt" |
| "io" |
| "io/ioutil" |
| ) |
| |
| 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" |
| ) |
| |
| // 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 |
| |
| *clientChan // the channel backing this session |
| |
| started bool // true once Start, Run or Shell is invoked. |
| closeAfterWait []io.Closer |
| copyFuncs []func() error |
| errch chan error // one send per copyFunc |
| } |
| |
| // RFC 4254 Section 6.4. |
| type setenvRequest struct { |
| PeersId uint32 |
| Request string |
| WantReply bool |
| 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 { |
| req := setenvRequest{ |
| PeersId: s.peersId, |
| Request: "env", |
| WantReply: true, |
| Name: name, |
| Value: value, |
| } |
| if err := s.writePacket(marshal(msgChannelRequest, req)); err != nil { |
| return err |
| } |
| return s.waitForResponse() |
| } |
| |
| // An empty mode list, see RFC 4254 Section 8. |
| var emptyModelist = "\x00" |
| |
| // RFC 4254 Section 6.2. |
| type ptyRequestMsg struct { |
| PeersId uint32 |
| Request string |
| WantReply bool |
| 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) error { |
| req := ptyRequestMsg{ |
| PeersId: s.peersId, |
| Request: "pty-req", |
| WantReply: true, |
| Term: term, |
| Columns: uint32(w), |
| Rows: uint32(h), |
| Width: uint32(w * 8), |
| Height: uint32(h * 8), |
| Modelist: emptyModelist, |
| } |
| if err := s.writePacket(marshal(msgChannelRequest, req)); err != nil { |
| return err |
| } |
| return s.waitForResponse() |
| } |
| |
| // RFC 4254 Section 6.9. |
| type signalMsg struct { |
| PeersId uint32 |
| Request string |
| WantReply bool |
| 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 { |
| req := signalMsg{ |
| PeersId: s.peersId, |
| Request: "signal", |
| WantReply: false, |
| Signal: string(sig), |
| } |
| return s.writePacket(marshal(msgChannelRequest, req)) |
| } |
| |
| // RFC 4254 Section 6.5. |
| type execMsg struct { |
| PeersId uint32 |
| Request string |
| WantReply bool |
| 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{ |
| PeersId: s.peersId, |
| Request: "exec", |
| WantReply: true, |
| Command: cmd, |
| } |
| if err := s.writePacket(marshal(msgChannelRequest, req)); err != nil { |
| return err |
| } |
| if err := s.waitForResponse(); err != nil { |
| return fmt.Errorf("ssh: could not execute command %s: %v", cmd, err) |
| } |
| return s.start() |
| } |
| |
| // Run runs cmd on the remote host and waits for it to terminate. |
| // 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) Run(cmd string) error { |
| err := s.Start(cmd) |
| if err != nil { |
| return err |
| } |
| return s.Wait() |
| } |
| |
| // Shell starts a login shell on the remote host. A Session only |
| // accepts one call to Run, Start or Shell. |
| func (s *Session) Shell() error { |
| if s.started { |
| return errors.New("ssh: session already started") |
| } |
| req := channelRequestMsg{ |
| PeersId: s.peersId, |
| Request: "shell", |
| WantReply: true, |
| } |
| if err := s.writePacket(marshal(msgChannelRequest, req)); err != nil { |
| return err |
| } |
| if err := s.waitForResponse(); err != nil { |
| return fmt.Errorf("ssh: cound not execute shell: %v", err) |
| } |
| return s.start() |
| } |
| |
| func (s *Session) waitForResponse() error { |
| msg := <-s.msg |
| switch msg.(type) { |
| case *channelRequestSuccessMsg: |
| return nil |
| case *channelRequestFailureMsg: |
| return errors.New("request failed") |
| } |
| return fmt.Errorf("unknown packet %T received: %v", msg, msg) |
| } |
| |
| func (s *Session) start() error { |
| s.started = true |
| |
| type F func(*Session) error |
| for _, setupFd := range []F{(*Session).stdin, (*Session).stdout, (*Session).stderr} { |
| if err := setupFd(s); err != nil { |
| return err |
| } |
| } |
| |
| s.errch = make(chan error, len(s.copyFuncs)) |
| for _, fn := range s.copyFuncs { |
| go func(fn func() error) { |
| s.errch <- fn() |
| }(fn) |
| } |
| return nil |
| } |
| |
| // Wait waits for the remote command to exit. |
| func (s *Session) Wait() error { |
| if !s.started { |
| return errors.New("ssh: session not started") |
| } |
| waitErr := s.wait() |
| |
| var copyError error |
| for _ = range s.copyFuncs { |
| if err := <-s.errch; err != nil && copyError == nil { |
| copyError = err |
| } |
| } |
| for _, fd := range s.closeAfterWait { |
| fd.Close() |
| } |
| if waitErr != nil { |
| return waitErr |
| } |
| return copyError |
| } |
| |
| func (s *Session) wait() error { |
| for { |
| switch msg := (<-s.msg).(type) { |
| case *channelRequestMsg: |
| // TODO(dfc) improve this behavior to match os.Waitmsg |
| switch msg.Request { |
| case "exit-status": |
| d := msg.RequestSpecificData |
| status := int(d[0])<<24 | int(d[1])<<16 | int(d[2])<<8 | int(d[3]) |
| if status > 0 { |
| return fmt.Errorf("remote process exited with %d", status) |
| } |
| return nil |
| case "exit-signal": |
| // TODO(dfc) make a more readable error message |
| return fmt.Errorf("%v", msg.RequestSpecificData) |
| default: |
| return fmt.Errorf("wait: unexpected channel request: %v", msg) |
| } |
| default: |
| return fmt.Errorf("wait: unexpected packet %T received: %v", msg, msg) |
| } |
| } |
| panic("unreachable") |
| } |
| |
| func (s *Session) stdin() error { |
| if s.Stdin == nil { |
| s.Stdin = new(bytes.Buffer) |
| } |
| s.copyFuncs = append(s.copyFuncs, func() error { |
| _, err := io.Copy(s.clientChan.stdin, s.Stdin) |
| if err1 := s.clientChan.stdin.Close(); err == nil { |
| err = err1 |
| } |
| return err |
| }) |
| return nil |
| } |
| |
| func (s *Session) stdout() error { |
| if s.Stdout == nil { |
| s.Stdout = ioutil.Discard |
| } |
| s.copyFuncs = append(s.copyFuncs, func() error { |
| _, err := io.Copy(s.Stdout, s.clientChan.stdout) |
| return err |
| }) |
| return nil |
| } |
| |
| func (s *Session) stderr() error { |
| if s.Stderr == nil { |
| s.Stderr = ioutil.Discard |
| } |
| s.copyFuncs = append(s.copyFuncs, func() error { |
| _, err := io.Copy(s.Stderr, s.clientChan.stderr) |
| return err |
| }) |
| return nil |
| } |
| |
| // 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") |
| } |
| pr, pw := io.Pipe() |
| s.Stdin = pr |
| s.closeAfterWait = append(s.closeAfterWait, pr) |
| return pw, 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 enought it may eventually cause the |
| // remote command to block. |
| func (s *Session) StdoutPipe() (io.ReadCloser, 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") |
| } |
| pr, pw := io.Pipe() |
| s.Stdout = pw |
| s.closeAfterWait = append(s.closeAfterWait, pw) |
| return pr, 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 enought it may eventually cause the |
| // remote command to block. |
| func (s *Session) StderrPipe() (io.ReadCloser, 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") |
| } |
| pr, pw := io.Pipe() |
| s.Stderr = pw |
| s.closeAfterWait = append(s.closeAfterWait, pw) |
| return pr, nil |
| } |
| |
| // TODO(dfc) add Output and CombinedOutput helpers |
| |
| // NewSession returns a new interactive session on the remote host. |
| func (c *ClientConn) NewSession() (*Session, error) { |
| ch := c.newChan(c.transport) |
| if err := c.writePacket(marshal(msgChannelOpen, channelOpenMsg{ |
| ChanType: "session", |
| PeersId: ch.id, |
| PeersWindow: 1 << 14, |
| MaxPacketSize: 1 << 15, // RFC 4253 6.1 |
| })); err != nil { |
| c.chanlist.remove(ch.id) |
| return nil, err |
| } |
| if err := ch.waitForChannelOpenResponse(); err != nil { |
| c.chanlist.remove(ch.id) |
| return nil, fmt.Errorf("ssh: unable to open session: %v", err) |
| } |
| return &Session{ |
| clientChan: ch, |
| }, nil |
| } |