terraform/communicator/ssh/communicator.go

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package ssh
import (
"bufio"
"bytes"
"context"
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"math/rand"
"net"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
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"time"
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"github.com/hashicorp/errwrap"
"github.com/hashicorp/terraform/communicator/remote"
"github.com/hashicorp/terraform/provisioners"
"github.com/zclconf/go-cty/cty"
"golang.org/x/crypto/ssh"
"golang.org/x/crypto/ssh/agent"
_ "github.com/hashicorp/terraform/internal/logging"
)
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
)
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// Communicator represents the SSH communicator
type Communicator struct {
connInfo *connectionInfo
client *ssh.Client
config *sshConfig
conn net.Conn
cancelKeepAlive context.CancelFunc
lock sync.Mutex
}
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type sshConfig struct {
// The configuration of the Go SSH connection
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config *ssh.ClientConfig
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// 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.
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connection func() (net.Conn, error)
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// noPty, if true, will not request a pty from the remote end.
noPty bool
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// 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
}
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// New creates a new communicator implementation over SSH.
func New(v cty.Value) (*Communicator, error) {
connInfo, err := parseConnectionInfo(v)
if err != nil {
return nil, err
}
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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())))
}
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comm := &Communicator{
connInfo: connInfo,
config: config,
}
return comm, nil
}
// Connect implementation of communicator.Communicator interface
func (c *Communicator) Connect(o provisioners.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"+
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" Password: %t\n"+
" Private key: %t\n"+
" Certificate: %t\n"+
" SSH Agent: %t\n"+
" Checking Host Key: %t\n"+
" Target Platform: %s\n",
c.connInfo.Host, c.connInfo.User,
c.connInfo.Password != "",
c.connInfo.PrivateKey != "",
c.connInfo.Certificate != "",
c.connInfo.Agent,
c.connInfo.HostKey != "",
c.connInfo.TargetPlatform,
))
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)
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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 {
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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.client.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")
// We want a local copy of the ssh client pointer, so that a reconnect
// doesn't race with the running keep-alive loop.
sshClient := c.client
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 := sshClient.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
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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
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func (c *Communicator) Timeout() time.Duration {
return c.connInfo.TimeoutVal
}
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// 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
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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 && c.connInfo.TargetPlatform != TargetPlatformWindows {
// 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
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func (c *Communicator) Upload(path string, input io.Reader) error {
// The target directory and file for talking the SCP protocol
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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
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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)
}
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return c.scpSession("scp -vt "+targetDir, scpFunc)
}
// UploadScript implementation of communicator.Communicator interface
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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) != "#!" && c.connInfo.TargetPlatform != TargetPlatformWindows {
script.WriteString(DefaultShebang)
}
script.ReadFrom(reader)
if err := c.Upload(path, &script); err != nil {
return err
}
if c.connInfo.TargetPlatform != TargetPlatformWindows {
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
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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)
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}
// Trailing slash, so only upload the contents
return uploadEntries()
}
return c.scpSession("scp -rvt "+dst, scpFunc)
}
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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
}
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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
}
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// 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()
}