terraform/communicator/ssh/provisioner.go

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package ssh
import (
"bytes"
"encoding/pem"
"errors"
"fmt"
"io/ioutil"
"log"
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"net"
"os"
"path/filepath"
"strings"
"time"
"github.com/hashicorp/terraform/communicator/shared"
"github.com/hashicorp/terraform/terraform"
"github.com/mitchellh/mapstructure"
"github.com/xanzy/ssh-agent"
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"golang.org/x/crypto/ssh"
"golang.org/x/crypto/ssh/agent"
"golang.org/x/crypto/ssh/knownhosts"
)
const (
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// DefaultUser is used if there is no user given
DefaultUser = "root"
// DefaultPort is used if there is no port given
DefaultPort = 22
// DefaultScriptPath is used as the path to copy the file to
// for remote execution if not provided otherwise.
DefaultScriptPath = "/tmp/terraform_%RAND%.sh"
// DefaultTimeout is used if there is no timeout given
DefaultTimeout = 5 * time.Minute
)
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// connectionInfo is decoded from the ConnInfo of the resource. These are the
// only keys we look at. If a PrivateKey is given, that is used instead
// of a password.
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type connectionInfo struct {
User string
Password string
PrivateKey string `mapstructure:"private_key"`
Certificate string `mapstructure:"certificate"`
Host string
HostKey string `mapstructure:"host_key"`
Port int
Agent bool
Timeout string
ScriptPath string `mapstructure:"script_path"`
TimeoutVal time.Duration `mapstructure:"-"`
BastionUser string `mapstructure:"bastion_user"`
BastionPassword string `mapstructure:"bastion_password"`
BastionPrivateKey string `mapstructure:"bastion_private_key"`
BastionCertificate string `mapstructure:"bastion_certificate"`
BastionHost string `mapstructure:"bastion_host"`
BastionHostKey string `mapstructure:"bastion_host_key"`
BastionPort int `mapstructure:"bastion_port"`
AgentIdentity string `mapstructure:"agent_identity"`
}
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// parseConnectionInfo is used to convert the ConnInfo of the InstanceState into
// a ConnectionInfo struct
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func parseConnectionInfo(s *terraform.InstanceState) (*connectionInfo, error) {
connInfo := &connectionInfo{}
decConf := &mapstructure.DecoderConfig{
WeaklyTypedInput: true,
Result: connInfo,
}
dec, err := mapstructure.NewDecoder(decConf)
if err != nil {
return nil, err
}
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if err := dec.Decode(s.Ephemeral.ConnInfo); err != nil {
return nil, err
}
// To default Agent to true, we need to check the raw string, since the
// decoded boolean can't represent "absence of config".
//
// And if SSH_AUTH_SOCK is not set, there's no agent to connect to, so we
// shouldn't try.
if s.Ephemeral.ConnInfo["agent"] == "" && os.Getenv("SSH_AUTH_SOCK") != "" {
connInfo.Agent = true
}
if connInfo.User == "" {
connInfo.User = DefaultUser
}
// Format the host if needed.
// Needed for IPv6 support.
connInfo.Host = shared.IpFormat(connInfo.Host)
if connInfo.Port == 0 {
connInfo.Port = DefaultPort
}
if connInfo.ScriptPath == "" {
connInfo.ScriptPath = DefaultScriptPath
}
if connInfo.Timeout != "" {
connInfo.TimeoutVal = safeDuration(connInfo.Timeout, DefaultTimeout)
} else {
connInfo.TimeoutVal = DefaultTimeout
}
// Default all bastion config attrs to their non-bastion counterparts
if connInfo.BastionHost != "" {
// Format the bastion host if needed.
// Needed for IPv6 support.
connInfo.BastionHost = shared.IpFormat(connInfo.BastionHost)
if connInfo.BastionUser == "" {
connInfo.BastionUser = connInfo.User
}
if connInfo.BastionPassword == "" {
connInfo.BastionPassword = connInfo.Password
}
if connInfo.BastionPrivateKey == "" {
connInfo.BastionPrivateKey = connInfo.PrivateKey
}
if connInfo.BastionCertificate == "" {
connInfo.BastionCertificate = connInfo.Certificate
}
if connInfo.BastionPort == 0 {
connInfo.BastionPort = connInfo.Port
}
}
return connInfo, nil
}
// safeDuration returns either the parsed duration or a default value
func safeDuration(dur string, defaultDur time.Duration) time.Duration {
d, err := time.ParseDuration(dur)
if err != nil {
log.Printf("Invalid duration '%s', using default of %s", dur, defaultDur)
return defaultDur
}
return d
}
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// prepareSSHConfig is used to turn the *ConnectionInfo provided into a
// usable *SSHConfig for client initialization.
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func prepareSSHConfig(connInfo *connectionInfo) (*sshConfig, error) {
sshAgent, err := connectToAgent(connInfo)
if err != nil {
return nil, err
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}
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host := fmt.Sprintf("%s:%d", connInfo.Host, connInfo.Port)
sshConf, err := buildSSHClientConfig(sshClientConfigOpts{
user: connInfo.User,
host: host,
privateKey: connInfo.PrivateKey,
password: connInfo.Password,
hostKey: connInfo.HostKey,
certificate: connInfo.Certificate,
sshAgent: sshAgent,
})
if err != nil {
return nil, err
}
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connectFunc := ConnectFunc("tcp", host)
var bastionConf *ssh.ClientConfig
if connInfo.BastionHost != "" {
bastionHost := fmt.Sprintf("%s:%d", connInfo.BastionHost, connInfo.BastionPort)
bastionConf, err = buildSSHClientConfig(sshClientConfigOpts{
user: connInfo.BastionUser,
host: bastionHost,
privateKey: connInfo.BastionPrivateKey,
password: connInfo.BastionPassword,
hostKey: connInfo.HostKey,
certificate: connInfo.BastionCertificate,
sshAgent: sshAgent,
})
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if err != nil {
return nil, err
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}
connectFunc = BastionConnectFunc("tcp", bastionHost, bastionConf, "tcp", host)
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}
config := &sshConfig{
config: sshConf,
connection: connectFunc,
sshAgent: sshAgent,
}
return config, nil
}
type sshClientConfigOpts struct {
privateKey string
password string
sshAgent *sshAgent
certificate string
user string
host string
hostKey string
}
func buildSSHClientConfig(opts sshClientConfigOpts) (*ssh.ClientConfig, error) {
hkCallback := ssh.InsecureIgnoreHostKey()
if opts.hostKey != "" {
// The knownhosts package only takes paths to files, but terraform
// generally wants to handle config data in-memory. Rather than making
// the known_hosts file an exception, write out the data to a temporary
// file to create the HostKeyCallback.
tf, err := ioutil.TempFile("", "tf-known_hosts")
if err != nil {
return nil, fmt.Errorf("failed to create temp known_hosts file: %s", err)
}
defer tf.Close()
defer os.RemoveAll(tf.Name())
// we mark this as a CA as well, but the host key fallback will still
// use it as a direct match if the remote host doesn't return a
// certificate.
if _, err := tf.WriteString(fmt.Sprintf("@cert-authority %s %s\n", opts.host, opts.hostKey)); err != nil {
return nil, fmt.Errorf("failed to write temp known_hosts file: %s", err)
}
tf.Sync()
hkCallback, err = knownhosts.New(tf.Name())
if err != nil {
return nil, err
}
}
conf := &ssh.ClientConfig{
HostKeyCallback: hkCallback,
User: opts.user,
}
if opts.privateKey != "" {
if opts.certificate != "" {
log.Println("using client certificate for authentication")
certSigner, err := signCertWithPrivateKey(opts.privateKey, opts.certificate)
if err != nil {
return nil, err
}
conf.Auth = append(conf.Auth, certSigner)
} else {
log.Println("using private key for authentication")
pubKeyAuth, err := readPrivateKey(opts.privateKey)
if err != nil {
return nil, err
}
conf.Auth = append(conf.Auth, pubKeyAuth)
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}
}
if opts.password != "" {
conf.Auth = append(conf.Auth, ssh.Password(opts.password))
conf.Auth = append(conf.Auth, ssh.KeyboardInteractive(
PasswordKeyboardInteractive(opts.password)))
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}
if opts.sshAgent != nil {
conf.Auth = append(conf.Auth, opts.sshAgent.Auth())
}
return conf, nil
}
// Create a Cert Signer and return ssh.AuthMethod
func signCertWithPrivateKey(pk string, certificate string) (ssh.AuthMethod, error) {
rawPk, err := ssh.ParseRawPrivateKey([]byte(pk))
if err != nil {
return nil, fmt.Errorf("failed to parse private key %q: %s", pk, err)
}
pcert, _, _, _, err := ssh.ParseAuthorizedKey([]byte(certificate))
if err != nil {
return nil, fmt.Errorf("failed to parse certificate %q: %s", certificate, err)
}
usigner, err := ssh.NewSignerFromKey(rawPk)
if err != nil {
return nil, fmt.Errorf("failed to create signer from raw private key %q: %s", rawPk, err)
}
ucertSigner, err := ssh.NewCertSigner(pcert.(*ssh.Certificate), usigner)
if err != nil {
return nil, fmt.Errorf("failed to create cert signer %q: %s", usigner, err)
}
return ssh.PublicKeys(ucertSigner), nil
}
func readPrivateKey(pk string) (ssh.AuthMethod, error) {
// We parse the private key on our own first so that we can
// show a nicer error if the private key has a password.
block, _ := pem.Decode([]byte(pk))
if block == nil {
return nil, errors.New("Failed to read ssh private key: no key found")
}
if block.Headers["Proc-Type"] == "4,ENCRYPTED" {
return nil, errors.New(
"Failed to read ssh private key: password protected keys are\n" +
"not supported. Please decrypt the key prior to use.")
}
signer, err := ssh.ParsePrivateKey([]byte(pk))
if err != nil {
return nil, fmt.Errorf("Failed to parse ssh private key: %s", err)
}
return ssh.PublicKeys(signer), nil
}
func connectToAgent(connInfo *connectionInfo) (*sshAgent, error) {
if connInfo.Agent != true {
// No agent configured
return nil, nil
}
agent, conn, err := sshagent.New()
if err != nil {
return nil, err
}
// connection close is handled over in Communicator
return &sshAgent{
agent: agent,
conn: conn,
id: connInfo.AgentIdentity,
}, nil
}
// A tiny wrapper around an agent.Agent to expose the ability to close its
// associated connection on request.
type sshAgent struct {
agent agent.Agent
conn net.Conn
id string
}
func (a *sshAgent) Close() error {
if a.conn == nil {
return nil
}
return a.conn.Close()
}
// make an attempt to either read the identity file or find a corresponding
// public key file using the typical openssh naming convention.
// This returns the public key in wire format, or nil when a key is not found.
func findIDPublicKey(id string) []byte {
for _, d := range idKeyData(id) {
signer, err := ssh.ParsePrivateKey(d)
if err == nil {
log.Println("[DEBUG] parsed id private key")
pk := signer.PublicKey()
return pk.Marshal()
}
// try it as a publicKey
pk, err := ssh.ParsePublicKey(d)
if err == nil {
log.Println("[DEBUG] parsed id public key")
return pk.Marshal()
}
// finally try it as an authorized key
pk, _, _, _, err = ssh.ParseAuthorizedKey(d)
if err == nil {
log.Println("[DEBUG] parsed id authorized key")
return pk.Marshal()
}
}
return nil
}
// Try to read an id file using the id as the file path. Also read the .pub
// file if it exists, as the id file may be encrypted. Return only the file
// data read. We don't need to know what data came from which path, as we will
// try parsing each as a private key, a public key and an authorized key
// regardless.
func idKeyData(id string) [][]byte {
idPath, err := filepath.Abs(id)
if err != nil {
return nil
}
var fileData [][]byte
paths := []string{idPath}
if !strings.HasSuffix(idPath, ".pub") {
paths = append(paths, idPath+".pub")
}
for _, p := range paths {
d, err := ioutil.ReadFile(p)
if err != nil {
log.Printf("[DEBUG] error reading %q: %s", p, err)
continue
}
log.Printf("[DEBUG] found identity data at %q", p)
fileData = append(fileData, d)
}
return fileData
}
// sortSigners moves a signer with an agent comment field matching the
// agent_identity to the head of the list when attempting authentication. This
// helps when there are more keys loaded in an agent than the host will allow
// attempts.
func (s *sshAgent) sortSigners(signers []ssh.Signer) {
if s.id == "" || len(signers) < 2 {
return
}
// if we can locate the public key, either by extracting it from the id or
// locating the .pub file, then we can more easily determine an exact match
idPk := findIDPublicKey(s.id)
// if we have a signer with a connect field that matches the id, send that
// first, otherwise put close matches at the front of the list.
head := 0
for i := range signers {
pk := signers[i].PublicKey()
k, ok := pk.(*agent.Key)
if !ok {
continue
}
// check for an exact match first
if bytes.Equal(pk.Marshal(), idPk) || s.id == k.Comment {
signers[0], signers[i] = signers[i], signers[0]
break
}
// no exact match yet, move it to the front if it's close. The agent
// may have loaded as a full filepath, while the config refers to it by
// filename only.
if strings.HasSuffix(k.Comment, s.id) {
signers[head], signers[i] = signers[i], signers[head]
head++
continue
}
}
ss := []string{}
for _, signer := range signers {
pk := signer.PublicKey()
k := pk.(*agent.Key)
ss = append(ss, k.Comment)
}
}
func (s *sshAgent) Signers() ([]ssh.Signer, error) {
signers, err := s.agent.Signers()
if err != nil {
return nil, err
}
s.sortSigners(signers)
return signers, nil
}
func (a *sshAgent) Auth() ssh.AuthMethod {
return ssh.PublicKeysCallback(a.Signers)
}
func (a *sshAgent) ForwardToAgent(client *ssh.Client) error {
return agent.ForwardToAgent(client, a.agent)
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}