package ssh import ( "bufio" "bytes" "errors" "fmt" "io" "io/ioutil" "log" "net" "os" "path/filepath" "sync" "time" "golang.org/x/crypto/ssh" ) // RemoteCmd represents a remote command being prepared or run. type RemoteCmd struct { // Command is the command to run remotely. This is executed as if // it were a shell command, so you are expected to do any shell escaping // necessary. Command string // Stdin specifies the process's standard input. If Stdin is // nil, the process reads from an empty bytes.Buffer. Stdin io.Reader // Stdout and Stderr represent the process's standard output and // error. // // If either is nil, it will be set to ioutil.Discard. Stdout io.Writer Stderr io.Writer // This will be set to true when the remote command has exited. It // shouldn't be set manually by the user, but there is no harm in // doing so. Exited bool // Once Exited is true, this will contain the exit code of the process. ExitStatus int // Internal fields exitCh chan struct{} // This thing is a mutex, lock when making modifications concurrently sync.Mutex } // SetExited is a helper for setting that this process is exited. This // should be called by communicators who are running a remote command in // order to set that the command is done. func (r *RemoteCmd) SetExited(status int) { r.Lock() defer r.Unlock() if r.exitCh == nil { r.exitCh = make(chan struct{}) } r.Exited = true r.ExitStatus = status close(r.exitCh) } // Wait waits for the remote command to complete. func (r *RemoteCmd) Wait() { // Make sure our condition variable is initialized. r.Lock() if r.exitCh == nil { r.exitCh = make(chan struct{}) } r.Unlock() <-r.exitCh } type SSHCommunicator struct { client *ssh.Client config *Config conn net.Conn address string } // Config is the structure used to configure the SSH communicator. type Config struct { // The configuration of the Go SSH connection SSHConfig *ssh.ClientConfig // Connection returns a new connection. The current connection // in use will be closed as part of the Close method, or in the // case an error occurs. Connection func() (net.Conn, error) // NoPty, if true, will not request a pty from the remote end. NoPty bool } // New creates a new packer.Communicator implementation over SSH. This takes // an already existing TCP connection and SSH configuration. func New(address string, config *Config) (result *SSHCommunicator, err error) { // Establish an initial connection and connect result = &SSHCommunicator{ config: config, address: address, } if err = result.reconnect(); err != nil { result = nil return } return } func (c *SSHCommunicator) Start(cmd *RemoteCmd) (err error) { session, err := c.newSession() if err != nil { return } // Setup our session session.Stdin = cmd.Stdin session.Stdout = cmd.Stdout session.Stderr = cmd.Stderr if !c.config.NoPty { // Request a PTY termModes := ssh.TerminalModes{ ssh.ECHO: 0, // do not echo ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud } if err = session.RequestPty("xterm", 80, 40, termModes); err != nil { return } } log.Printf("starting remote command: %s", cmd.Command) err = session.Start(cmd.Command + "\n") if err != nil { return } // Start a goroutine to wait for the session to end and set the // exit boolean and status. go func() { defer session.Close() err := session.Wait() exitStatus := 0 if err != nil { exitErr, ok := err.(*ssh.ExitError) if ok { exitStatus = exitErr.ExitStatus() } } log.Printf("remote command exited with '%d': %s", exitStatus, cmd.Command) cmd.SetExited(exitStatus) }() return } func (c *SSHCommunicator) Upload(path string, input io.Reader) error { // The target directory and file for talking the SCP protocol targetDir := filepath.Dir(path) targetFile := filepath.Base(path) // On windows, filepath.Dir uses backslash separators (ie. "\tmp"). // This does not work when the target host is unix. Switch to forward slash // which works for unix and windows targetDir = filepath.ToSlash(targetDir) scpFunc := func(w io.Writer, stdoutR *bufio.Reader) error { return scpUploadFile(targetFile, input, w, stdoutR) } return c.scpSession("scp -vt "+targetDir, scpFunc) } func (c *SSHCommunicator) UploadDir(dst string, src string, excl []string) error { log.Printf("Upload dir '%s' to '%s'", src, dst) scpFunc := func(w io.Writer, r *bufio.Reader) error { uploadEntries := func() error { f, err := os.Open(src) if err != nil { return err } defer f.Close() entries, err := f.Readdir(-1) if err != nil { return err } return scpUploadDir(src, entries, w, r) } if src[len(src)-1] != '/' { log.Printf("No trailing slash, creating the source directory name") return scpUploadDirProtocol(filepath.Base(src), w, r, uploadEntries) } // Trailing slash, so only upload the contents return uploadEntries() } return c.scpSession("scp -rvt "+dst, scpFunc) } func (c *SSHCommunicator) Download(string, io.Writer) error { panic("not implemented yet") } func (c *SSHCommunicator) newSession() (session *ssh.Session, err error) { log.Println("opening new ssh session") if c.client == nil { err = errors.New("client not available") } else { session, err = c.client.NewSession() } if err != nil { log.Printf("ssh session open error: '%s', attempting reconnect", err) if err := c.reconnect(); err != nil { return nil, err } return c.client.NewSession() } return session, nil } func (c *SSHCommunicator) reconnect() (err error) { if c.conn != nil { c.conn.Close() } // Set the conn and client to nil since we'll recreate it c.conn = nil c.client = nil log.Printf("reconnecting to TCP connection for SSH") c.conn, err = c.config.Connection() if err != nil { // Explicitly set this to the REAL nil. Connection() can return // a nil implementation of net.Conn which will make the // "if c.conn == nil" check fail above. Read here for more information // on this psychotic language feature: // // http://golang.org/doc/faq#nil_error c.conn = nil log.Printf("reconnection error: %s", err) return } log.Printf("handshaking with SSH") sshConn, sshChan, req, err := ssh.NewClientConn(c.conn, c.address, c.config.SSHConfig) if err != nil { log.Printf("handshake error: %s", err) } if sshConn != nil { c.client = ssh.NewClient(sshConn, sshChan, req) } return } func (c *SSHCommunicator) scpSession(scpCommand string, f func(io.Writer, *bufio.Reader) error) error { session, err := c.newSession() if err != nil { return err } defer session.Close() // Get a pipe to stdin so that we can send data down stdinW, err := session.StdinPipe() if err != nil { return err } // We only want to close once, so we nil w after we close it, // and only close in the defer if it hasn't been closed already. defer func() { if stdinW != nil { stdinW.Close() } }() // Get a pipe to stdout so that we can get responses back stdoutPipe, err := session.StdoutPipe() if err != nil { return err } stdoutR := bufio.NewReader(stdoutPipe) // Set stderr to a bytes buffer stderr := new(bytes.Buffer) session.Stderr = stderr // Start the sink mode on the other side // TODO(mitchellh): There are probably issues with shell escaping the path log.Println("Starting remote scp process: ", scpCommand) if err := session.Start(scpCommand); err != nil { return err } // Call our callback that executes in the context of SCP. We ignore // EOF errors if they occur because it usually means that SCP prematurely // ended on the other side. log.Println("Started SCP session, beginning transfers...") if err := f(stdinW, stdoutR); err != nil && err != io.EOF { return err } // Close the stdin, which sends an EOF, and then set w to nil so that // our defer func doesn't close it again since that is unsafe with // the Go SSH package. log.Println("SCP session complete, closing stdin pipe.") stdinW.Close() stdinW = nil // Wait for the SCP connection to close, meaning it has consumed all // our data and has completed. Or has errored. log.Println("Waiting for SSH session to complete.") err = session.Wait() if err != nil { if exitErr, ok := err.(*ssh.ExitError); ok { // Otherwise, we have an ExitErorr, meaning we can just read // the exit status log.Printf("non-zero exit status: %d", exitErr.ExitStatus()) // If we exited with status 127, it means SCP isn't available. // Return a more descriptive error for that. if exitErr.ExitStatus() == 127 { return errors.New( "SCP failed to start. This usually means that SCP is not\n" + "properly installed on the remote system.") } } return err } log.Printf("scp stderr (length %d): %s", stderr.Len(), stderr.String()) return nil } // checkSCPStatus checks that a prior command sent to SCP completed // successfully. If it did not complete successfully, an error will // be returned. func checkSCPStatus(r *bufio.Reader) error { code, err := r.ReadByte() if err != nil { return err } if code != 0 { // Treat any non-zero (really 1 and 2) as fatal errors message, _, err := r.ReadLine() if err != nil { return fmt.Errorf("Error reading error message: %s", err) } return errors.New(string(message)) } return nil } func scpUploadFile(dst string, src io.Reader, w io.Writer, r *bufio.Reader) error { // Create a temporary file where we can copy the contents of the src // so that we can determine the length, since SCP is length-prefixed. tf, err := ioutil.TempFile("", "packer-upload") if err != nil { return fmt.Errorf("Error creating temporary file for upload: %s", err) } defer os.Remove(tf.Name()) defer tf.Close() log.Println("Copying input data into temporary file so we can read the length") if _, err := io.Copy(tf, src); err != nil { return err } // Sync the file so that the contents are definitely on disk, then // read the length of it. if err := tf.Sync(); err != nil { return fmt.Errorf("Error creating temporary file for upload: %s", err) } // Seek the file to the beginning so we can re-read all of it if _, err := tf.Seek(0, 0); err != nil { return fmt.Errorf("Error creating temporary file for upload: %s", err) } fi, err := tf.Stat() if err != nil { return fmt.Errorf("Error creating temporary file for upload: %s", err) } // Start the protocol log.Println("Beginning file upload...") fmt.Fprintln(w, "C0644", fi.Size(), dst) if err := checkSCPStatus(r); err != nil { return err } if _, err := io.Copy(w, tf); err != nil { return err } fmt.Fprint(w, "\x00") if err := checkSCPStatus(r); err != nil { return err } return nil } func scpUploadDirProtocol(name string, w io.Writer, r *bufio.Reader, f func() error) error { log.Printf("SCP: starting directory upload: %s", name) fmt.Fprintln(w, "D0755 0", name) err := checkSCPStatus(r) if err != nil { return err } if err := f(); err != nil { return err } fmt.Fprintln(w, "E") if err != nil { return err } return nil } func scpUploadDir(root string, fs []os.FileInfo, w io.Writer, r *bufio.Reader) error { for _, fi := range fs { realPath := filepath.Join(root, fi.Name()) // Track if this is actually a symlink to a directory. If it is // a symlink to a file we don't do any special behavior because uploading // a file just works. If it is a directory, we need to know so we // treat it as such. isSymlinkToDir := false if fi.Mode()&os.ModeSymlink == os.ModeSymlink { symPath, err := filepath.EvalSymlinks(realPath) if err != nil { return err } symFi, err := os.Lstat(symPath) if err != nil { return err } isSymlinkToDir = symFi.IsDir() } if !fi.IsDir() && !isSymlinkToDir { // It is a regular file (or symlink to a file), just upload it f, err := os.Open(realPath) if err != nil { return err } err = func() error { defer f.Close() return scpUploadFile(fi.Name(), f, w, r) }() if err != nil { return err } continue } // It is a directory, recursively upload err := scpUploadDirProtocol(fi.Name(), w, r, func() error { f, err := os.Open(realPath) if err != nil { return err } defer f.Close() entries, err := f.Readdir(-1) if err != nil { return err } return scpUploadDir(realPath, entries, w, r) }) if err != nil { return err } } return nil } // ConnectFunc is a convenience method for returning a function // that just uses net.Dial to communicate with the remote end that // is suitable for use with the SSH communicator configuration. func ConnectFunc(network, addr string) func() (net.Conn, error) { return func() (net.Conn, error) { c, err := net.DialTimeout(network, addr, 15*time.Second) if err != nil { return nil, err } if tcpConn, ok := c.(*net.TCPConn); ok { tcpConn.SetKeepAlive(true) } return c, nil } }