package ssh import ( "bufio" "bytes" "context" "errors" "fmt" "io" "io/ioutil" "log" "math/rand" "net" "os" "path/filepath" "strconv" "strings" "sync" "time" "github.com/hashicorp/errwrap" "github.com/hashicorp/terraform/communicator/remote" "github.com/hashicorp/terraform/terraform" "golang.org/x/crypto/ssh" "golang.org/x/crypto/ssh/agent" ) const ( // DefaultShebang is added at the top of a SSH script file DefaultShebang = "#!/bin/sh\n" ) var ( // randShared is a global random generator object that is shared. This must be // shared since it is seeded by the current time and creating multiple can // result in the same values. By using a shared RNG we assure different numbers // per call. randLock sync.Mutex randShared *rand.Rand // enable ssh keeplive probes by default keepAliveInterval = 2 * time.Second // max time to wait for for a KeepAlive response before considering the // connection to be dead. maxKeepAliveDelay = 120 * time.Second ) // Communicator represents the SSH communicator type Communicator struct { connInfo *connectionInfo client *ssh.Client config *sshConfig conn net.Conn address string cancelKeepAlive context.CancelFunc lock sync.Mutex } type sshConfig struct { // The configuration of the Go SSH connection config *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 // sshAgent is a struct surrounding the agent.Agent client and the net.Conn // to the SSH Agent. It is nil if no SSH agent is configured sshAgent *sshAgent } type fatalError struct { error } func (e fatalError) FatalError() error { return e.error } // New creates a new communicator implementation over SSH. func New(s *terraform.InstanceState) (*Communicator, error) { connInfo, err := parseConnectionInfo(s) if err != nil { return nil, err } config, err := prepareSSHConfig(connInfo) if err != nil { return nil, err } // Setup the random number generator once. The seed value is the // time multiplied by the PID. This can overflow the int64 but that // is okay. We multiply by the PID in case we have multiple processes // grabbing this at the same time. This is possible with Terraform and // if we communicate to the same host at the same instance, we could // overwrite the same files. Multiplying by the PID prevents this. randLock.Lock() defer randLock.Unlock() if randShared == nil { randShared = rand.New(rand.NewSource( time.Now().UnixNano() * int64(os.Getpid()))) } comm := &Communicator{ connInfo: connInfo, config: config, } return comm, nil } // Connect implementation of communicator.Communicator interface func (c *Communicator) Connect(o terraform.UIOutput) (err error) { // Grab a lock so we can modify our internal attributes c.lock.Lock() defer c.lock.Unlock() 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 if o != nil { o.Output(fmt.Sprintf( "Connecting to remote host via SSH...\n"+ " Host: %s\n"+ " User: %s\n"+ " Password: %t\n"+ " Private key: %t\n"+ " Certificate: %t\n"+ " SSH Agent: %t\n"+ " Checking Host Key: %t", c.connInfo.Host, c.connInfo.User, c.connInfo.Password != "", c.connInfo.PrivateKey != "", c.connInfo.Certificate != "", c.connInfo.Agent, c.connInfo.HostKey != "", )) if c.connInfo.BastionHost != "" { o.Output(fmt.Sprintf( "Using configured bastion host...\n"+ " Host: %s\n"+ " User: %s\n"+ " Password: %t\n"+ " Private key: %t\n"+ " Certificate: %t\n"+ " SSH Agent: %t\n"+ " Checking Host Key: %t", c.connInfo.BastionHost, c.connInfo.BastionUser, c.connInfo.BastionPassword != "", c.connInfo.BastionPrivateKey != "", c.connInfo.BastionCertificate != "", c.connInfo.Agent, c.connInfo.BastionHostKey != "", )) } } hostAndPort := fmt.Sprintf("%s:%d", c.connInfo.Host, c.connInfo.Port) log.Printf("[DEBUG] Connecting to %s for SSH", hostAndPort) 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("[ERROR] connection error: %s", err) return err } log.Printf("[DEBUG] Connection established. Handshaking for user %v", c.connInfo.User) sshConn, sshChan, req, err := ssh.NewClientConn(c.conn, hostAndPort, c.config.config) if err != nil { err = errwrap.Wrapf(fmt.Sprintf("SSH authentication failed (%s@%s): {{err}}", c.connInfo.User, hostAndPort), err) // While in theory this should be a fatal error, some hosts may start // the ssh service before it is properly configured, or before user // authentication data is available. // Log the error, and allow the provisioner to retry. log.Printf("[WARN] %s", err) return err } c.client = ssh.NewClient(sshConn, sshChan, req) if c.config.sshAgent != nil { log.Printf("[DEBUG] Telling SSH config to forward to agent") if err := c.config.sshAgent.ForwardToAgent(c.client); err != nil { return fatalError{err} } log.Printf("[DEBUG] Setting up a session to request agent forwarding") session, err := c.newSession() if err != nil { return err } defer session.Close() err = agent.RequestAgentForwarding(session) if err == nil { log.Printf("[INFO] agent forwarding enabled") } else { log.Printf("[WARN] error forwarding agent: %s", err) } } if err != nil { return err } if o != nil { o.Output("Connected!") } ctx, cancelKeepAlive := context.WithCancel(context.TODO()) c.cancelKeepAlive = cancelKeepAlive // Start a keepalive goroutine to help maintain the connection for // long-running commands. log.Printf("[DEBUG] starting ssh KeepAlives") go func() { defer cancelKeepAlive() // Along with the KeepAlives generating packets to keep the tcp // connection open, we will use the replies to verify liveness of the // connection. This will prevent dead connections from blocking the // provisioner indefinitely. respCh := make(chan error, 1) go func() { t := time.NewTicker(keepAliveInterval) defer t.Stop() for { select { case <-t.C: _, _, err := c.client.SendRequest("keepalive@terraform.io", true, nil) respCh <- err case <-ctx.Done(): return } } }() after := time.NewTimer(maxKeepAliveDelay) defer after.Stop() for { select { case err := <-respCh: if err != nil { log.Printf("[ERROR] ssh keepalive: %s", err) sshConn.Close() return } case <-after.C: // abort after too many missed keepalives log.Println("[ERROR] no reply from ssh server") sshConn.Close() return case <-ctx.Done(): return } if !after.Stop() { <-after.C } after.Reset(maxKeepAliveDelay) } }() return nil } // Disconnect implementation of communicator.Communicator interface func (c *Communicator) Disconnect() error { c.lock.Lock() defer c.lock.Unlock() if c.cancelKeepAlive != nil { c.cancelKeepAlive() } if c.config.sshAgent != nil { if err := c.config.sshAgent.Close(); err != nil { return err } } if c.conn != nil { conn := c.conn c.conn = nil return conn.Close() } return nil } // Timeout implementation of communicator.Communicator interface func (c *Communicator) Timeout() time.Duration { return c.connInfo.TimeoutVal } // ScriptPath implementation of communicator.Communicator interface func (c *Communicator) ScriptPath() string { randLock.Lock() defer randLock.Unlock() return strings.Replace( c.connInfo.ScriptPath, "%RAND%", strconv.FormatInt(int64(randShared.Int31()), 10), -1) } // Start implementation of communicator.Communicator interface func (c *Communicator) Start(cmd *remote.Cmd) error { cmd.Init() session, err := c.newSession() if err != nil { return err } // 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 err } } log.Printf("[DEBUG] starting remote command: %s", cmd.Command) err = session.Start(strings.TrimSpace(cmd.Command) + "\n") if err != nil { return err } // 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() } } cmd.SetExitStatus(exitStatus, err) log.Printf("[DEBUG] remote command exited with '%d': %s", exitStatus, cmd.Command) }() return nil } // Upload implementation of communicator.Communicator interface func (c *Communicator) 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) // Skip copying if we can get the file size directly from common io.Readers size := int64(0) switch src := input.(type) { case *os.File: fi, err := src.Stat() if err != nil { size = fi.Size() } case *bytes.Buffer: size = int64(src.Len()) case *bytes.Reader: size = int64(src.Len()) case *strings.Reader: size = int64(src.Len()) } scpFunc := func(w io.Writer, stdoutR *bufio.Reader) error { return scpUploadFile(targetFile, input, w, stdoutR, size) } return c.scpSession("scp -vt "+targetDir, scpFunc) } // UploadScript implementation of communicator.Communicator interface func (c *Communicator) UploadScript(path string, input io.Reader) error { reader := bufio.NewReader(input) prefix, err := reader.Peek(2) if err != nil { return fmt.Errorf("Error reading script: %s", err) } var script bytes.Buffer if string(prefix) != "#!" { script.WriteString(DefaultShebang) } script.ReadFrom(reader) if err := c.Upload(path, &script); err != nil { return err } var stdout, stderr bytes.Buffer cmd := &remote.Cmd{ Command: fmt.Sprintf("chmod 0777 %s", path), Stdout: &stdout, Stderr: &stderr, } if err := c.Start(cmd); err != nil { return fmt.Errorf( "Error chmodding script file to 0777 in remote "+ "machine: %s", err) } if err := cmd.Wait(); err != nil { return fmt.Errorf( "Error chmodding script file to 0777 in remote "+ "machine %v: %s %s", err, stdout.String(), stderr.String()) } return nil } // UploadDir implementation of communicator.Communicator interface func (c *Communicator) UploadDir(dst string, src string) error { log.Printf("[DEBUG] Uploading 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("[DEBUG] 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 *Communicator) newSession() (session *ssh.Session, err error) { log.Println("[DEBUG] opening new ssh session") if c.client == nil { err = errors.New("ssh client is not connected") } else { session, err = c.client.NewSession() } if err != nil { log.Printf("[WARN] ssh session open error: '%s', attempting reconnect", err) if err := c.Connect(nil); err != nil { return nil, err } return c.client.NewSession() } return session, nil } func (c *Communicator) 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("[DEBUG] 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("[DEBUG] 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("[DEBUG] 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("[DEBUG] Waiting for SSH session to complete.") err = session.Wait() // log any stderr before exiting on an error scpErr := stderr.String() if len(scpErr) > 0 { log.Printf("[ERROR] scp stderr: %q", stderr) } 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("[ERROR] %s", exitErr) // 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 } 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, size int64) error { if size == 0 { // 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("", "terraform-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("[DEBUG] 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) } src = tf size = fi.Size() } // Start the protocol log.Println("[DEBUG] Beginning file upload...") fmt.Fprintln(w, "C0644", size, dst) if err := checkSCPStatus(r); err != nil { return err } if _, err := io.Copy(w, src); 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("[DEBUG] 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, fi.Size()) }() 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 } } // BastionConnectFunc is a convenience method for returning a function // that connects to a host over a bastion connection. func BastionConnectFunc( bProto string, bAddr string, bConf *ssh.ClientConfig, proto string, addr string) func() (net.Conn, error) { return func() (net.Conn, error) { log.Printf("[DEBUG] Connecting to bastion: %s", bAddr) bastion, err := ssh.Dial(bProto, bAddr, bConf) if err != nil { return nil, fmt.Errorf("Error connecting to bastion: %s", err) } log.Printf("[DEBUG] Connecting via bastion (%s) to host: %s", bAddr, addr) conn, err := bastion.Dial(proto, addr) if err != nil { bastion.Close() return nil, err } // Wrap it up so we close both things properly return &bastionConn{ Conn: conn, Bastion: bastion, }, nil } } type bastionConn struct { net.Conn Bastion *ssh.Client } func (c *bastionConn) Close() error { c.Conn.Close() return c.Bastion.Close() }