packer-cn/communicator/ssh/communicator.go

589 lines
14 KiB
Go
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package ssh
import (
"bufio"
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"bytes"
"errors"
"fmt"
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"github.com/mitchellh/packer/packer"
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"golang.org/x/crypto/ssh"
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"golang.org/x/crypto/ssh/agent"
"io"
"io/ioutil"
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"log"
"net"
"os"
"path/filepath"
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"strconv"
"sync"
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)
type comm 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)
// Pty, if true, will request a pty from the remote end.
Pty bool
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}
// 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 *comm, err error) {
// Establish an initial connection and connect
result = &comm{
config: config,
address: address,
}
if err = result.reconnect(); err != nil {
result = nil
return
}
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return
}
func (c *comm) Start(cmd *packer.RemoteCmd) (err error) {
session, err := c.newSession()
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if err != nil {
return
}
// Setup our session
session.Stdin = cmd.Stdin
session.Stdout = cmd.Stdout
session.Stderr = cmd.Stderr
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if c.config.Pty {
// 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
}
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if err = session.RequestPty("xterm", 80, 40, termModes); err != nil {
return
}
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}
log.Printf("starting remote command: %s", cmd.Command)
err = session.Start(cmd.Command + "\n")
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if err != nil {
return
}
// A channel to keep track of our done state
doneCh := make(chan struct{})
sessionLock := new(sync.Mutex)
timedOut := false
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// Start a goroutine to wait for the session to end and set the
// exit boolean and status.
go func() {
defer session.Close()
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err := session.Wait()
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exitStatus := 0
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if err != nil {
exitErr, ok := err.(*ssh.ExitError)
if ok {
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exitStatus = exitErr.ExitStatus()
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}
}
sessionLock.Lock()
defer sessionLock.Unlock()
if timedOut {
// We timed out, so set the exit status to -1
exitStatus = -1
}
log.Printf("remote command exited with '%d': %s", exitStatus, cmd.Command)
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cmd.SetExited(exitStatus)
close(doneCh)
}()
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return
}
func (c *comm) Upload(path string, input io.Reader, fi *os.FileInfo) error {
// The target directory and file for talking the SCP protocol
target_dir := filepath.Dir(path)
target_file := filepath.Base(path)
// On windows, filepath.Dir uses backslash seperators (ie. "\tmp").
// This does not work when the target host is unix. Switch to forward slash
// which works for unix and windows
target_dir = filepath.ToSlash(target_dir)
scpFunc := func(w io.Writer, stdoutR *bufio.Reader) error {
return scpUploadFile(target_file, input, w, stdoutR, fi)
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}
return c.scpSession("scp -vt "+target_dir, scpFunc)
}
func (c *comm) 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")
fi, err := os.Stat(src)
if err != nil {
return err
}
return scpUploadDirProtocol(filepath.Base(src), w, r, uploadEntries, fi)
} else {
// Trailing slash, so only upload the contents
return uploadEntries()
}
}
return c.scpSession("scp -rvt "+dst, scpFunc)
}
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func (c *comm) Download(path string, output io.Writer) error {
scpFunc := func(w io.Writer, stdoutR *bufio.Reader) error {
fmt.Fprint(w, "\x00")
// read file info
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fi, err := stdoutR.ReadString('\n')
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if err != nil {
return err
}
if len(fi) < 0 {
return fmt.Errorf("empty response from server")
}
switch fi[0] {
case '\x01', '\x02':
return fmt.Errorf("%s", fi[1:len(fi)])
case 'C':
case 'D':
return fmt.Errorf("remote file is directory")
default:
return fmt.Errorf("unexpected server response (%x)", fi[0])
}
var mode string
var size int64
n, err := fmt.Sscanf(fi, "%6s %d ", &mode, &size)
if err != nil || n != 2 {
return fmt.Errorf("can't parse server response (%s)", fi)
}
if size < 0 {
return fmt.Errorf("negative file size")
}
fmt.Fprint(w, "\x00")
if _, err := io.CopyN(output, stdoutR, size); err != nil {
return err
}
fmt.Fprint(w, "\x00")
if err := checkSCPStatus(stdoutR); err != nil {
return err
}
return nil
}
return c.scpSession("scp -vf "+strconv.Quote(path), scpFunc)
}
func (c *comm) 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 {
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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 *comm) 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)
}
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c.connectToAgent()
return
}
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func (c *comm) connectToAgent() {
if c.client == nil {
return
}
// open connection to the local agent
socketLocation := os.Getenv("SSH_AUTH_SOCK")
if socketLocation == "" {
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log.Printf("[INFO] no local agent socket, will not connect agent")
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return
}
agentConn, err := net.Dial("unix", socketLocation)
if err != nil {
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log.Printf("[ERROR] could not connect to local agent socket: %s", socketLocation)
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return
}
// create agent and add in auth
forwardingAgent := agent.NewClient(agentConn)
if forwardingAgent == nil {
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log.Printf("[ERROR] Could not create agent client")
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agentConn.Close()
return
}
// add callback for forwarding agent to SSH config
// XXX - might want to handle reconnects appending multiple callbacks
auth := ssh.PublicKeysCallback(forwardingAgent.Signers)
c.config.SSHConfig.Auth = append(c.config.SSHConfig.Auth, auth)
agent.ForwardToAgent(c.client, forwardingAgent)
// Setup a session to request agent forwarding
session, err := c.newSession()
if err != nil {
return
}
defer session.Close()
err = agent.RequestAgentForwarding(session)
if err != nil {
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log.Printf("[ERROR] RequestAgentForwarding: %#v", err)
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return
}
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log.Printf("[INFO] agent forwarding enabled")
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return
}
func (c *comm) 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
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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, fi *os.FileInfo) error {
var mode os.FileMode
var size int64
if fi != nil && (*fi).Mode().IsRegular() {
mode = (*fi).Mode().Perm()
size = (*fi).Size()
} else {
// 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()
mode = 0644
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)
}
tfi, err := tf.Stat()
if err != nil {
return fmt.Errorf("Error creating temporary file for upload: %s", err)
}
size = tfi.Size()
src = tf
}
// Start the protocol
perms := fmt.Sprintf("C%04o", mode)
log.Printf("[DEBUG] Uploading %s: perms=%s size=%d", dst, perms, size)
fmt.Fprintln(w, perms, size, dst)
if err := checkSCPStatus(r); err != nil {
return err
}
if _, err := io.CopyN(w, src, size); 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, fi os.FileInfo) error {
log.Printf("SCP: starting directory upload: %s", name)
mode := fi.Mode().Perm()
perms := fmt.Sprintf("D%04o 0", mode)
fmt.Fprintln(w, perms, 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
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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)
}()
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)
}, fi)
if err != nil {
return err
}
}
return nil
}