adding basic support for OpenSSH CertificateFile support

small fix

communicator/ssh/connect_test.go

@@ -0,0 +1,73 @@
+package ssh_test
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"os/user"
+	"testing"
+	"time"
+
+	helperssh "github.com/hashicorp/packer/helper/ssh"
+	"golang.org/x/crypto/ssh"
+)
+
+func getIdentityCertFile() (certSigner ssh.Signer, err error) {
+	usr, _ := user.Current()
+	privateKeyFile := usr.HomeDir + "/.ssh/id_ed25519"
+	certificateFile := usr.HomeDir + "/.ssh/id_ed25519-cert.pub"
+
+	return helperssh.FileSignerWithCert(privateKeyFile, certificateFile)
+}
+
+func TestConnectFunc(t *testing.T) {
+	{
+		if os.Getenv("PACKER_ACC") == "" {
+			t.Skip("This test is only run with PACKER_ACC=1")
+		}
+
+		const host = "mybastionhost.com:2222"
+
+		certSigner, err := getIdentityCertFile()
+		if err != nil {
+			panic(fmt.Errorf("we have an error %v", err))
+		}
+
+		publicKeys := ssh.PublicKeys(certSigner)
+		usr, _ := user.Current()
+
+		config := &ssh.ClientConfig{
+			User: usr.Username,
+			Auth: []ssh.AuthMethod{
+				publicKeys,
+			},
+			HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+			Timeout:         30 * time.Second,
+		}
+
+		println("Dialing", config.User)
+		connection, err := ssh.Dial("tcp", host, config)
+
+		if err != nil {
+			log.Fatal("Failed to dial ", err)
+			return
+		}
+
+		session, err := connection.NewSession()
+		if err != nil {
+			log.Fatal("Failed to create session: ", err)
+			return
+		}
+		defer session.Close()
+
+		var stdoutBuf bytes.Buffer
+		session.Stdout = &stdoutBuf
+
+		err = session.Run("ls")
+		if err != nil {
+			log.Fatal("Failed to ls")
+		}
+		fmt.Println(stdoutBuf.String())
+	}
+}

helper/communicator/config.go

@@ -111,6 +111,10 @@ type SSH struct {
 	// The `~` can be used in path and will be expanded to the home directory
 	// of current user.
 	SSHPrivateKeyFile string `mapstructure:"ssh_private_key_file" undocumented:"true"`
+	// Path to user certificate used to authenticate with SSH.
+	// The `~` can be used in path and will be expanded to the
+	// home directory of current user.
+	SSHCertificateFile string `mapstructure:"ssh_certificate_file"`
 	// If `true`, a PTY will be requested for the SSH connection. This defaults
 	// to `false`.
 	SSHPty bool `mapstructure:"ssh_pty"`
@@ -148,6 +152,10 @@ type SSH struct {
 	// bastion host. The `~` can be used in path and will be expanded to the
 	// home directory of current user.
 	SSHBastionPrivateKeyFile string `mapstructure:"ssh_bastion_private_key_file"`
+	// Path to user certificate used to authenticate with bastion host.
+	// The `~` can be used in path and will be expanded to the
+	//home directory of current user.
+	SSHBastionCertificateFile string `mapstructure:"ssh_bastion_certificate_file"`
 	// `scp` or `sftp` - How to transfer files, Secure copy (default) or SSH
 	// File Transfer Protocol.
 	SSHFileTransferMethod string `mapstructure:"ssh_file_transfer_method"`
@@ -316,11 +324,29 @@ func (c *Config) SSHConfigFunc() func(multistep.StateBag) (*ssh.ClientConfig, er
 			privateKeys = append(privateKeys, c.SSHPrivateKey)
 		}
 
+		certPath := ""
+		if c.SSHCertificateFile != "" {
+			var err error
+			certPath, err = packer.ExpandUser(c.SSHCertificateFile)
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		for _, key := range privateKeys {
+
 			signer, err := ssh.ParsePrivateKey(key)
 			if err != nil {
 				return nil, fmt.Errorf("Error on parsing SSH private key: %s", err)
 			}
+
+			if certPath != "" {
+				signer, err = helperssh.ReadCertificate(certPath, signer)
+				if err != nil {
+					return nil, err
+				}
+			}
+
 			sshConfig.Auth = append(sshConfig.Auth, ssh.PublicKeys(signer))
 		}
 
@@ -431,6 +457,11 @@ func (c *Config) prepareSSH(ctx *interpolate.Context) []error {
 		if c.SSHBastionPrivateKeyFile == "" && c.SSHPrivateKeyFile != "" {
 			c.SSHBastionPrivateKeyFile = c.SSHPrivateKeyFile
 		}
+
+		if c.SSHBastionCertificateFile == "" && c.SSHCertificateFile != "" {
+			c.SSHBastionCertificateFile = c.SSHCertificateFile
+		}
+
 	}
 
 	if c.SSHProxyHost != "" {
@@ -462,9 +493,23 @@ func (c *Config) prepareSSH(ctx *interpolate.Context) []error {
 		} else if _, err := os.Stat(path); err != nil {
 			errs = append(errs, fmt.Errorf(
 				"ssh_private_key_file is invalid: %s", err))
-		} else if _, err := helperssh.FileSigner(path); err != nil {
-			errs = append(errs, fmt.Errorf(
-				"ssh_private_key_file is invalid: %s", err))
+		} else {
+			if c.SSHCertificateFile != "" {
+				certPath, err := packer.ExpandUser(c.SSHCertificateFile)
+				if err != nil {
+					errs = append(errs, fmt.Errorf("invalid identity certificate: #{err}"))
+				}
+
+				if _, err := helperssh.FileSignerWithCert(path, certPath); err != nil {
+					errs = append(errs, fmt.Errorf(
+						"ssh_private_key_file is invalid: %s", err))
+				}
+			} else {
+				if _, err := helperssh.FileSigner(path); err != nil {
+					errs = append(errs, fmt.Errorf(
+						"ssh_private_key_file is invalid: %s", err))
+				}
+			}
 		}
 	}
 
@@ -480,9 +525,22 @@ func (c *Config) prepareSSH(ctx *interpolate.Context) []error {
 			} else if _, err := os.Stat(path); err != nil {
 				errs = append(errs, fmt.Errorf(
 					"ssh_bastion_private_key_file is invalid: %s", err))
-			} else if _, err := helperssh.FileSigner(path); err != nil {
-				errs = append(errs, fmt.Errorf(
-					"ssh_bastion_private_key_file is invalid: %s", err))
+			} else {
+				if c.SSHBastionCertificateFile != "" {
+					certPath, err := packer.ExpandUser(c.SSHBastionCertificateFile)
+					if err != nil {
+						errs = append(errs, fmt.Errorf("invalid identity certificate: #{err}"))
+					}
+					if _, err := helperssh.FileSignerWithCert(path, certPath); err != nil {
+						errs = append(errs, fmt.Errorf(
+							"ssh_bastion_private_key_file is invalid: %s", err))
+					}
+				} else {
+					if _, err := helperssh.FileSigner(path); err != nil {
+						errs = append(errs, fmt.Errorf(
+							"ssh_bastion_private_key_file is invalid: %s", err))
+					}
+				}
 			}
 		}
 	}

helper/communicator/config.hcl2spec.go

@@ -20,6 +20,7 @@ type FlatConfig struct {
 	SSHCiphers                []string `mapstructure:"ssh_ciphers" cty:"ssh_ciphers" hcl:"ssh_ciphers"`
 	SSHClearAuthorizedKeys    *bool    `mapstructure:"ssh_clear_authorized_keys" cty:"ssh_clear_authorized_keys" hcl:"ssh_clear_authorized_keys"`
 	SSHPrivateKeyFile         *string  `mapstructure:"ssh_private_key_file" undocumented:"true" cty:"ssh_private_key_file" hcl:"ssh_private_key_file"`
+	SSHCertificateFile        *string  `mapstructure:"ssh_certificate_file" cty:"ssh_certificate_file" hcl:"ssh_certificate_file"`
 	SSHPty                    *bool    `mapstructure:"ssh_pty" cty:"ssh_pty" hcl:"ssh_pty"`
 	SSHTimeout                *string  `mapstructure:"ssh_timeout" cty:"ssh_timeout" hcl:"ssh_timeout"`
 	SSHWaitTimeout            *string  `mapstructure:"ssh_wait_timeout" undocumented:"true" cty:"ssh_wait_timeout" hcl:"ssh_wait_timeout"`
@@ -33,6 +34,7 @@ type FlatConfig struct {
 	SSHBastionPassword        *string  `mapstructure:"ssh_bastion_password" cty:"ssh_bastion_password" hcl:"ssh_bastion_password"`
 	SSHBastionInteractive     *bool    `mapstructure:"ssh_bastion_interactive" cty:"ssh_bastion_interactive" hcl:"ssh_bastion_interactive"`
 	SSHBastionPrivateKeyFile  *string  `mapstructure:"ssh_bastion_private_key_file" cty:"ssh_bastion_private_key_file" hcl:"ssh_bastion_private_key_file"`
+	SSHBastionCertificateFile *string  `mapstructure:"ssh_bastion_certificate_file" cty:"ssh_bastion_certificate_file" hcl:"ssh_bastion_certificate_file"`
 	SSHFileTransferMethod     *string  `mapstructure:"ssh_file_transfer_method" cty:"ssh_file_transfer_method" hcl:"ssh_file_transfer_method"`
 	SSHProxyHost              *string  `mapstructure:"ssh_proxy_host" cty:"ssh_proxy_host" hcl:"ssh_proxy_host"`
 	SSHProxyPort              *int     `mapstructure:"ssh_proxy_port" cty:"ssh_proxy_port" hcl:"ssh_proxy_port"`
@@ -78,6 +80,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"ssh_ciphers":                  &hcldec.AttrSpec{Name: "ssh_ciphers", Type: cty.List(cty.String), Required: false},
 		"ssh_clear_authorized_keys":    &hcldec.AttrSpec{Name: "ssh_clear_authorized_keys", Type: cty.Bool, Required: false},
 		"ssh_private_key_file":         &hcldec.AttrSpec{Name: "ssh_private_key_file", Type: cty.String, Required: false},
+		"ssh_certificate_file":         &hcldec.AttrSpec{Name: "ssh_certificate_file", Type: cty.String, Required: false},
 		"ssh_pty":                      &hcldec.AttrSpec{Name: "ssh_pty", Type: cty.Bool, Required: false},
 		"ssh_timeout":                  &hcldec.AttrSpec{Name: "ssh_timeout", Type: cty.String, Required: false},
 		"ssh_wait_timeout":             &hcldec.AttrSpec{Name: "ssh_wait_timeout", Type: cty.String, Required: false},
@@ -91,6 +94,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"ssh_bastion_password":         &hcldec.AttrSpec{Name: "ssh_bastion_password", Type: cty.String, Required: false},
 		"ssh_bastion_interactive":      &hcldec.AttrSpec{Name: "ssh_bastion_interactive", Type: cty.Bool, Required: false},
 		"ssh_bastion_private_key_file": &hcldec.AttrSpec{Name: "ssh_bastion_private_key_file", Type: cty.String, Required: false},
+		"ssh_bastion_certificate_file": &hcldec.AttrSpec{Name: "ssh_bastion_certificate_file", Type: cty.String, Required: false},
 		"ssh_file_transfer_method":     &hcldec.AttrSpec{Name: "ssh_file_transfer_method", Type: cty.String, Required: false},
 		"ssh_proxy_host":               &hcldec.AttrSpec{Name: "ssh_proxy_host", Type: cty.String, Required: false},
 		"ssh_proxy_port":               &hcldec.AttrSpec{Name: "ssh_proxy_port", Type: cty.Number, Required: false},
@@ -127,6 +131,7 @@ type FlatSSH struct {
 	SSHCiphers                []string `mapstructure:"ssh_ciphers" cty:"ssh_ciphers" hcl:"ssh_ciphers"`
 	SSHClearAuthorizedKeys    *bool    `mapstructure:"ssh_clear_authorized_keys" cty:"ssh_clear_authorized_keys" hcl:"ssh_clear_authorized_keys"`
 	SSHPrivateKeyFile         *string  `mapstructure:"ssh_private_key_file" undocumented:"true" cty:"ssh_private_key_file" hcl:"ssh_private_key_file"`
+	SSHCertificateFile        *string  `mapstructure:"ssh_certificate_file" cty:"ssh_certificate_file" hcl:"ssh_certificate_file"`
 	SSHPty                    *bool    `mapstructure:"ssh_pty" cty:"ssh_pty" hcl:"ssh_pty"`
 	SSHTimeout                *string  `mapstructure:"ssh_timeout" cty:"ssh_timeout" hcl:"ssh_timeout"`
 	SSHWaitTimeout            *string  `mapstructure:"ssh_wait_timeout" undocumented:"true" cty:"ssh_wait_timeout" hcl:"ssh_wait_timeout"`
@@ -140,6 +145,7 @@ type FlatSSH struct {
 	SSHBastionPassword        *string  `mapstructure:"ssh_bastion_password" cty:"ssh_bastion_password" hcl:"ssh_bastion_password"`
 	SSHBastionInteractive     *bool    `mapstructure:"ssh_bastion_interactive" cty:"ssh_bastion_interactive" hcl:"ssh_bastion_interactive"`
 	SSHBastionPrivateKeyFile  *string  `mapstructure:"ssh_bastion_private_key_file" cty:"ssh_bastion_private_key_file" hcl:"ssh_bastion_private_key_file"`
+	SSHBastionCertificateFile *string  `mapstructure:"ssh_bastion_certificate_file" cty:"ssh_bastion_certificate_file" hcl:"ssh_bastion_certificate_file"`
 	SSHFileTransferMethod     *string  `mapstructure:"ssh_file_transfer_method" cty:"ssh_file_transfer_method" hcl:"ssh_file_transfer_method"`
 	SSHProxyHost              *string  `mapstructure:"ssh_proxy_host" cty:"ssh_proxy_host" hcl:"ssh_proxy_host"`
 	SSHProxyPort              *int     `mapstructure:"ssh_proxy_port" cty:"ssh_proxy_port" hcl:"ssh_proxy_port"`
@@ -174,6 +180,7 @@ func (*FlatSSH) HCL2Spec() map[string]hcldec.Spec {
 		"ssh_ciphers":                  &hcldec.AttrSpec{Name: "ssh_ciphers", Type: cty.List(cty.String), Required: false},
 		"ssh_clear_authorized_keys":    &hcldec.AttrSpec{Name: "ssh_clear_authorized_keys", Type: cty.Bool, Required: false},
 		"ssh_private_key_file":         &hcldec.AttrSpec{Name: "ssh_private_key_file", Type: cty.String, Required: false},
+		"ssh_certificate_file":         &hcldec.AttrSpec{Name: "ssh_certificate_file", Type: cty.String, Required: false},
 		"ssh_pty":                      &hcldec.AttrSpec{Name: "ssh_pty", Type: cty.Bool, Required: false},
 		"ssh_timeout":                  &hcldec.AttrSpec{Name: "ssh_timeout", Type: cty.String, Required: false},
 		"ssh_wait_timeout":             &hcldec.AttrSpec{Name: "ssh_wait_timeout", Type: cty.String, Required: false},
@@ -187,6 +194,7 @@ func (*FlatSSH) HCL2Spec() map[string]hcldec.Spec {
 		"ssh_bastion_password":         &hcldec.AttrSpec{Name: "ssh_bastion_password", Type: cty.String, Required: false},
 		"ssh_bastion_interactive":      &hcldec.AttrSpec{Name: "ssh_bastion_interactive", Type: cty.Bool, Required: false},
 		"ssh_bastion_private_key_file": &hcldec.AttrSpec{Name: "ssh_bastion_private_key_file", Type: cty.String, Required: false},
+		"ssh_bastion_certificate_file": &hcldec.AttrSpec{Name: "ssh_bastion_certificate_file", Type: cty.String, Required: false},
 		"ssh_file_transfer_method":     &hcldec.AttrSpec{Name: "ssh_file_transfer_method", Type: cty.String, Required: false},
 		"ssh_proxy_host":               &hcldec.AttrSpec{Name: "ssh_proxy_host", Type: cty.String, Required: false},
 		"ssh_proxy_port":               &hcldec.AttrSpec{Name: "ssh_proxy_port", Type: cty.Number, Required: false},

helper/communicator/config_test.go

@@ -139,6 +139,30 @@ func TestConfig_winrm_use_ntlm(t *testing.T) {
 
 }
 
+func TestSSHBastion(t *testing.T) {
+	c := &Config{
+		Type: "ssh",
+		SSH: SSH{
+			SSHUsername:        "root",
+			SSHBastionHost:     "mybastionhost.company.com",
+			SSHBastionPassword: "test",
+		},
+	}
+
+	if err := c.Prepare(testContext(t)); len(err) > 0 {
+		t.Fatalf("bad: %#v", err)
+	}
+
+	if c.SSHBastionCertificateFile != "" {
+		t.Fatalf("Identity certificate somehow set")
+	}
+
+	if c.SSHPrivateKeyFile != "" {
+		t.Fatalf("Private key file somehow set")
+	}
+
+}
+
 func TestSSHConfigFunc(t *testing.T) {
 	state := new(multistep.BasicStateBag)
 
@@ -170,7 +194,9 @@ func TestSSHConfigFunc(t *testing.T) {
 	if sshConfig.Config.Ciphers[0] != "partycipher" {
 		t.Fatalf("ssh_ciphers should be a direct passthrough.")
 	}
-
+	if c.SSHCertificateFile != "" {
+		t.Fatalf("Identity certificate somehow set")
+	}
 }
 
 func TestConfig_winrm(t *testing.T) {

helper/communicator/step_connect_ssh.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"golang.org/x/crypto/ssh/terminal"
 	"io"
 	"log"
 	"net"
@@ -12,6 +11,8 @@ import (
 	"strings"
 	"time"
 
+	"golang.org/x/crypto/ssh/terminal"
+
 	"github.com/hashicorp/packer/communicator/ssh"
 	"github.com/hashicorp/packer/helper/multistep"
 	helperssh "github.com/hashicorp/packer/helper/ssh"
@@ -277,12 +278,23 @@ func sshBastionConfig(config *Config) (*gossh.ClientConfig, error) {
 				"Error expanding path for SSH bastion private key: %s", err)
 		}
 
-		signer, err := helperssh.FileSigner(path)
-		if err != nil {
-			return nil, err
+		if config.SSHBastionCertificateFile != "" {
+			identityPath, err := packer.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))
 		}
-
-		auth = append(auth, gossh.PublicKeys(signer))
 	}
 
 	if config.SSHBastionAgentAuth {

helper/ssh/ssh.go

@@ -5,12 +5,12 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"time"
 
 	"golang.org/x/crypto/ssh"
 )
 
-// FileSigner returns an ssh.Signer for a key file.
-func FileSigner(path string) (ssh.Signer, error) {
+func parseKeyFile(path string) ([]byte, error) {
 	f, err := os.Open(path)
 	if err != nil {
 		return nil, err
@@ -34,6 +34,16 @@ func FileSigner(path string) (ssh.Signer, error) {
 			"Failed to read key '%s': password protected keys are\n"+
 				"not supported. Please decrypt the key prior to use.", path)
 	}
+	return keyBytes, nil
+}
+
+// FileSigner returns an ssh.Signer for a key file.
+func FileSigner(path string) (ssh.Signer, error) {
+
+	keyBytes, err := parseKeyFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("Error setting up SSH config: %s", err)
+	}
 
 	signer, err := ssh.ParsePrivateKey(keyBytes)
 	if err != nil {
@@ -42,3 +52,64 @@ func FileSigner(path string) (ssh.Signer, error) {
 
 	return signer, nil
 }
+
+func ReadCertificate(certificatePath string, keySigner ssh.Signer) (ssh.Signer, error) {
+
+	if certificatePath == "" {
+		return keySigner, fmt.Errorf("no certificate file provided")
+	}
+
+	// Load the certificate
+	cert, err := ioutil.ReadFile(certificatePath)
+	if err != nil {
+		return nil, fmt.Errorf("unable to read certificate file: %v", err)
+	}
+
+	pk, _, _, _, err := ssh.ParseAuthorizedKey(cert)
+	if err != nil {
+		return nil, fmt.Errorf("unable to parse public key: %v", err)
+	}
+
+	certificate, ok := pk.(*ssh.Certificate)
+
+	if !ok {
+		return nil, fmt.Errorf("Error loading certificate")
+	}
+
+	err = checkValidCert(certificate)
+
+	if err != nil {
+		return nil, fmt.Errorf("%s not a valid cert: %v", certificatePath, err)
+	}
+
+	certSigner, err := ssh.NewCertSigner(certificate, keySigner)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create cert signer: %v", err)
+	}
+
+	return certSigner, nil
+}
+
+// FileSigner returns an ssh.Signer for a key file.
+func FileSignerWithCert(path string, certificatePath string) (ssh.Signer, error) {
+
+	keySigner, err := FileSigner(path)
+
+	if err != nil {
+		return nil, err
+	}
+	return ReadCertificate(certificatePath, keySigner)
+}
+
+func checkValidCert(cert *ssh.Certificate) error {
+	const CertTimeInfinity = 1<<64 - 1
+	unixNow := time.Now().Unix()
+
+	if after := int64(cert.ValidAfter); after < 0 || unixNow < int64(cert.ValidAfter) {
+		return fmt.Errorf("ssh: cert is not yet valid")
+	}
+	if before := int64(cert.ValidBefore); cert.ValidBefore != uint64(CertTimeInfinity) && (unixNow >= before || before < 0) {
+		return fmt.Errorf("ssh: cert has expired")
+	}
+	return nil
+}