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step_connect_ssh.go
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step_connect_ssh.go
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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package communicator
import (
"context"
"errors"
"fmt"
"golang.org/x/term"
"io"
"log"
"net"
"os"
"strings"
"time"
helperssh "github.com/hashicorp/packer-plugin-sdk/communicator/ssh"
"github.com/hashicorp/packer-plugin-sdk/multistep"
packersdk "github.com/hashicorp/packer-plugin-sdk/packer"
"github.com/hashicorp/packer-plugin-sdk/pathing"
"github.com/hashicorp/packer-plugin-sdk/sdk-internals/communicator/ssh"
gossh "golang.org/x/crypto/ssh"
"golang.org/x/crypto/ssh/agent"
"golang.org/x/net/proxy"
)
// StepConnectSSH is a step that only connects to SSH.
//
// In general, you should use StepConnect.
type StepConnectSSH struct {
// All the fields below are documented on StepConnect
Config *Config
Host func(multistep.StateBag) (string, error)
SSHConfig func(multistep.StateBag) (*gossh.ClientConfig, error)
SSHPort func(multistep.StateBag) (int, error)
}
func (s *StepConnectSSH) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction {
ui := state.Get("ui").(packersdk.Ui)
var comm packersdk.Communicator
var err error
subCtx, cancel := context.WithCancel(ctx)
waitDone := make(chan bool, 1)
go func() {
ui.Say("Waiting for SSH to become available...")
comm, err = s.waitForSSH(state, subCtx)
cancel() // just to make 'possible context leak' analysis happy
waitDone <- true
}()
log.Printf("[INFO] Waiting for SSH, up to timeout: %s", s.Config.SSHTimeout)
timeout := make(<-chan time.Time)
if s.Config.SSHTimeout > 0 {
timeout = time.After(s.Config.SSHTimeout)
}
for {
// Wait for either SSH to become available, a timeout to occur,
// or an interrupt to come through.
select {
case <-waitDone:
if err != nil {
ui.Error(fmt.Sprintf("Error waiting for SSH: %s", err))
state.Put("error", err)
return multistep.ActionHalt
}
ui.Say("Connected to SSH!")
state.Put("communicator", comm)
return multistep.ActionContinue
case <-timeout:
err := fmt.Errorf("Timeout waiting for SSH.")
state.Put("error", err)
ui.Error(err.Error())
cancel()
return multistep.ActionHalt
case <-ctx.Done():
// The step sequence was cancelled, so cancel waiting for SSH
// and just start the halting process.
cancel()
log.Println("[WARN] Interrupt detected, quitting waiting for SSH.")
return multistep.ActionHalt
case <-time.After(1 * time.Second):
}
}
}
func (s *StepConnectSSH) Cleanup(multistep.StateBag) {
}
func (s *StepConnectSSH) waitForSSH(state multistep.StateBag, ctx context.Context) (packersdk.Communicator, error) {
// Determine if we're using a bastion host, and if so, retrieve
// that configuration. This configuration doesn't change so we
// do this one before entering the retry loop.
var bProto, bAddr string
var bConf *gossh.ClientConfig
var pAddr string
var pAuth *proxy.Auth
if s.Config.SSHBastionHost != "" {
// The protocol is hardcoded for now, but may be configurable one day
bProto = "tcp"
bAddr = fmt.Sprintf(
"%s:%d", s.Config.SSHBastionHost, s.Config.SSHBastionPort)
conf, err := sshBastionConfig(s.Config)
if err != nil {
return nil, fmt.Errorf("Error configuring bastion: %s", err)
}
bConf = conf
}
if s.Config.SSHProxyHost != "" {
pAddr = fmt.Sprintf("%s:%d", s.Config.SSHProxyHost, s.Config.SSHProxyPort)
if s.Config.SSHProxyUsername != "" {
pAuth = new(proxy.Auth)
pAuth.User = s.Config.SSHProxyUsername
pAuth.Password = s.Config.SSHProxyPassword
}
}
handshakeAttempts := 0
var comm packersdk.Communicator
first := true
for {
// Don't check for cancel or wait on first iteration
if !first {
select {
case <-ctx.Done():
log.Println("[DEBUG] SSH wait cancelled. Exiting loop.")
return nil, errors.New("SSH wait cancelled")
case <-time.After(5 * time.Second):
}
}
first = false
// First we request the TCP connection information
host, err := s.Host(state)
if err != nil {
log.Printf("[DEBUG] Error getting SSH address: %s", err)
continue
}
// store host and port in config so we can access them from provisioners
s.Config.SSHHost = host
port := s.Config.SSHPort
if s.SSHPort != nil {
port, err = s.SSHPort(state)
if err != nil {
log.Printf("[DEBUG] Error getting SSH port: %s", err)
continue
}
s.Config.SSHPort = port
}
state.Put("communicator_config", s.Config)
// Retrieve the SSH configuration
sshConfig, err := s.SSHConfig(state)
if err != nil {
log.Printf("[DEBUG] Error getting SSH config: %s", err)
continue
}
// Attempt to connect to SSH port
var connFunc func() (net.Conn, error)
address := fmt.Sprintf("%s:%d", host, port)
if bAddr != "" {
log.Printf("[INFO] connecting with SSH to host %s through bastion at %s",
address, bAddr)
// We're using a bastion host, so use the bastion connfunc
connFunc = ssh.BastionConnectFunc(
bProto, bAddr, bConf, "tcp", address)
} else if pAddr != "" {
// Connect via SOCKS5 proxy
connFunc = ssh.ProxyConnectFunc(pAddr, pAuth, "tcp", address)
} else {
// No bastion host, connect directly
connFunc = ssh.ConnectFunc("tcp", address)
}
nc, err := connFunc()
if err != nil {
log.Printf("[DEBUG] TCP connection to SSH ip/port failed: %s", err)
continue
}
nc.Close()
// Parse out all the requested Port Tunnels that will go over our SSH connection
var tunnels []ssh.TunnelSpec
for _, v := range s.Config.SSHLocalTunnels {
t, err := helperssh.ParseTunnelArgument(v, ssh.LocalTunnel)
if err != nil {
return nil, fmt.Errorf(
"Error parsing port forwarding: %s", err)
}
tunnels = append(tunnels, t)
}
for _, v := range s.Config.SSHRemoteTunnels {
t, err := helperssh.ParseTunnelArgument(v, ssh.RemoteTunnel)
if err != nil {
return nil, fmt.Errorf(
"Error parsing port forwarding: %s", err)
}
tunnels = append(tunnels, t)
}
// Then we attempt to connect via SSH
config := &ssh.Config{
Connection: connFunc,
SSHConfig: sshConfig,
Pty: s.Config.SSHPty,
DisableAgentForwarding: s.Config.SSHDisableAgentForwarding,
UseSftp: s.Config.SSHFileTransferMethod == "sftp",
KeepAliveInterval: s.Config.SSHKeepAliveInterval,
Timeout: s.Config.SSHReadWriteTimeout,
Tunnels: tunnels,
}
log.Printf("[INFO] Attempting SSH connection to %s...", address)
comm, err = ssh.New(address, config)
if err != nil {
log.Printf("[DEBUG] SSH handshake err: %s", err)
// Only count this as an attempt if we were able to attempt
// to authenticate. Note this is very brittle since it depends
// on the string of the error... but I don't see any other way.
if strings.Contains(err.Error(), "authenticate") {
log.Printf(
"[DEBUG] Detected authentication error. Increasing handshake attempts.")
err = fmt.Errorf("Packer experienced an authentication error "+
"when trying to connect via SSH. This can happen if your "+
"username/password are wrong. You may want to double-check"+
" your credentials as part of your debugging process. "+
"original error: %s",
err)
handshakeAttempts += 1
}
if s.Config.SSHHandshakeAttempts > 0 &&
handshakeAttempts >= s.Config.SSHHandshakeAttempts {
return nil, err
}
// Try to connect via SSH a handful of times. We sleep here
// so we don't get a ton of authentication errors back to back.
time.Sleep(2 * time.Second)
continue
}
break
}
return comm, nil
}
func sshBastionConfig(config *Config) (*gossh.ClientConfig, error) {
auth := make([]gossh.AuthMethod, 0, 2)
if config.SSHBastionInteractive {
var c io.ReadWriteCloser
if term.IsTerminal(int(os.Stdin.Fd())) {
c = os.Stdin
} else {
tty, err := os.Open("/dev/tty")
if err != nil {
return nil, err
}
defer tty.Close()
c = tty
}
auth = append(auth, gossh.KeyboardInteractive(ssh.KeyboardInteractive(c)))
}
if config.SSHBastionPassword != "" {
auth = append(auth,
gossh.Password(config.SSHBastionPassword),
gossh.KeyboardInteractive(
ssh.PasswordKeyboardInteractive(config.SSHBastionPassword)))
}
if config.SSHBastionPrivateKeyFile != "" {
path, err := pathing.ExpandUser(config.SSHBastionPrivateKeyFile)
if err != nil {
return nil, fmt.Errorf(
"Error expanding path for SSH bastion private key: %s", err)
}
if config.SSHBastionCertificateFile != "" {
identityPath, err := pathing.ExpandUser(config.SSHBastionCertificateFile)
if err != nil {
return nil, fmt.Errorf("Error expanding path for SSH bastion identity certificate: %s", err)
}
signer, err := helperssh.FileSignerWithCert(path, identityPath)
if err != nil {
return nil, err
}
auth = append(auth, gossh.PublicKeys(signer))
} else {
signer, err := helperssh.FileSigner(path)
if err != nil {
return nil, err
}
auth = append(auth, gossh.PublicKeys(signer))
}
}
if config.SSHBastionAgentAuth {
authSock := os.Getenv("SSH_AUTH_SOCK")
if authSock == "" {
return nil, fmt.Errorf("SSH_AUTH_SOCK is not set")
}
sshAgent, err := net.Dial("unix", authSock)
if err != nil {
return nil, fmt.Errorf("Cannot connect to SSH Agent socket %q: %s", authSock, err)
}
auth = append(auth, gossh.PublicKeysCallback(agent.NewClient(sshAgent).Signers))
}
return &gossh.ClientConfig{
User: config.SSHBastionUsername,
Auth: auth,
HostKeyCallback: gossh.InsecureIgnoreHostKey(),
}, nil
}