feat(ssh-key): support passphrases for --ssh-key options

1. Enter passphrase in cli prompt when running in interactive terminal.
2. Pass passhprase using `--ssh-key file://PASSPHRASE@FILEPATH` format (works only when `file://` schema has been specified).

Signed-off-by: Timofey Kirillov <timofey.kirillov@flant.com>

pkg/ssh_agent/ssh_agent.go

@@ -8,12 +8,15 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"strings"
 
 	uuid "github.com/satori/go.uuid"
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/crypto/ssh/agent"
+	"golang.org/x/crypto/ssh/terminal"
 
 	"github.com/werf/logboek"
+	secret_common "github.com/werf/werf/cmd/werf/helm/secret/common"
 	"github.com/werf/werf/pkg/util"
 	"github.com/werf/werf/pkg/werf"
 )
@@ -28,24 +31,93 @@ func setupProcessSSHAgent(sshAuthSock string) error {
 	return os.Setenv("SSH_AUTH_SOCK", SSHAuthSock)
 }
 
-func Init(ctx context.Context, keys []string) error {
-	for _, key := range keys {
-		if keyExists, err := util.FileExists(key); !keyExists {
-			return fmt.Errorf("specified ssh key %s does not exist", key)
-		} else if err != nil {
-			return fmt.Errorf("specified ssh key %s does not exist: %v", key, err)
+type sshKeyConfig struct {
+	FilePath   string
+	Passphrase []byte
+}
+
+type sshKey struct {
+	Config     sshKeyConfig
+	PrivateKey interface{}
+}
+
+func getSshKeyConfig(path string) (sshKeyConfig, error) {
+	var filePath string
+	var passphrase []byte
+
+	switch {
+	case strings.HasPrefix(path, "file://"):
+		userinfoWithPath := strings.TrimPrefix(path, "file://")
+
+		parts := strings.SplitN(userinfoWithPath, "@", 2)
+		passphrase = []byte(parts[0])
+		filePath = util.ExpandPath(parts[1])
+
+	default:
+		filePath = util.ExpandPath(path)
+	}
+
+	if keyExists, err := util.FileExists(filePath); !keyExists {
+		return sshKeyConfig{}, fmt.Errorf("specified ssh key does not exist")
+	} else if err != nil {
+		return sshKeyConfig{}, fmt.Errorf("specified ssh key does not exist: %w", err)
+	}
+
+	return sshKeyConfig{FilePath: filePath, Passphrase: passphrase}, nil
+}
+
+type loadSshKeysOptions struct {
+	WarnInvalidKeys bool
+}
+
+func loadSshKeys(ctx context.Context, configs []sshKeyConfig, opts loadSshKeysOptions) ([]sshKey, error) {
+	var res []sshKey
+
+	for _, cfg := range configs {
+		sshKey, err := parsePrivateSSHKey(cfg)
+		if err != nil {
+			if opts.WarnInvalidKeys {
+				logboek.Context(ctx).Warn().LogF("WARNING: unable to parse ssh key %s: %s\n", cfg.FilePath, err)
+				continue
+			} else {
+				return nil, fmt.Errorf("unable to parse ssh key %s: %s", cfg.FilePath, err)
+			}
 		}
+
+		res = append(res, sshKey)
 	}
 
-	if len(keys) > 0 {
-		agentSock, err := runSSHAgentWithKeys(ctx, keys)
+	return res, nil
+}
+
+func Init(ctx context.Context, userKeys []string) error {
+	var configs []sshKeyConfig
+
+	for _, key := range userKeys {
+		cfg, err := getSshKeyConfig(key)
 		if err != nil {
-			return fmt.Errorf("unable to run ssh agent with specified keys: %s", err)
+			return fmt.Errorf("unable to get ssh key %s config: %s", key, err)
 		}
-		if err := setupProcessSSHAgent(agentSock); err != nil {
-			return fmt.Errorf("unable to init ssh auth socket to %q: %s", agentSock, err)
+
+		configs = append(configs, cfg)
+	}
+
+	if len(configs) > 0 {
+		keys, err := loadSshKeys(ctx, configs, loadSshKeysOptions{})
+		if err != nil {
+			return fmt.Errorf("unable to load ssh keys: %s", err)
+		}
+
+		if len(keys) > 0 {
+			agentSock, err := runSSHAgentWithKeys(ctx, keys)
+			if err != nil {
+				return fmt.Errorf("unable to run ssh agent with specified keys: %s", err)
+			}
+			if err := setupProcessSSHAgent(agentSock); err != nil {
+				return fmt.Errorf("unable to init ssh auth socket to %q: %s", agentSock, err)
+			}
+			return nil
 		}
-		return nil
 	}
 
 	systemAgentSock := os.Getenv("SSH_AUTH_SOCK")
@@ -56,35 +128,23 @@ func Init(ctx context.Context, keys []string) error {
 		return nil
 	}
 
-	var defaultKeys []string
+	var defaultConfigs []*sshKeyConfig
 	for _, defaultFileName := range []string{"id_rsa", "id_dsa"} {
 		path := filepath.Join(os.Getenv("HOME"), ".ssh", defaultFileName)
 
 		if keyExists, _ := util.FileExists(path); keyExists {
-			defaultKeys = append(defaultKeys, path)
+			defaultConfigs = append(defaultConfigs, &sshKeyConfig{FilePath: path})
 		}
 	}
 
-	if len(defaultKeys) > 0 {
-		var validKeys []string
-
-		for _, key := range defaultKeys {
-			keyData, err := ioutil.ReadFile(key)
-			if err != nil {
-				logboek.Context(ctx).Warn().LogF("WARNING: cannot read default key %s: %s\n", key, err)
-				continue
-			}
-			_, err = ssh.ParseRawPrivateKey(keyData)
-			if err != nil {
-				logboek.Context(ctx).Warn().LogF("WARNING: default key %s validation error: %s\n", key, err)
-				continue
-			}
-
-			validKeys = append(validKeys, key)
+	if len(defaultConfigs) > 0 {
+		keys, err := loadSshKeys(ctx, configs, loadSshKeysOptions{WarnInvalidKeys: true})
+		if err != nil {
+			return fmt.Errorf("unable to load ssh keys: %s", err)
 		}
 
-		if len(validKeys) > 0 {
-			agentSock, err := runSSHAgentWithKeys(ctx, validKeys)
+		if len(keys) > 0 {
+			agentSock, err := runSSHAgentWithKeys(ctx, keys)
 			if err != nil {
 				return fmt.Errorf("unable to run ssh agent with specified keys: %s", err)
 			}
@@ -108,7 +168,7 @@ func Terminate() error {
 	return nil
 }
 
-func runSSHAgentWithKeys(ctx context.Context, keys []string) (string, error) {
+func runSSHAgentWithKeys(ctx context.Context, keys []sshKey) (string, error) {
 	agentSock, err := runSSHAgent(ctx)
 	if err != nil {
 		return "", fmt.Errorf("error running ssh agent: %s", err)
@@ -117,7 +177,7 @@ func runSSHAgentWithKeys(ctx context.Context, keys []string) (string, error) {
 	for _, key := range keys {
 		err := addSSHKey(ctx, agentSock, key)
 		if err != nil {
-			return "", fmt.Errorf("error adding ssh key %s: %s", key, err)
+			return "", fmt.Errorf("error adding ssh key: %s", err)
 		}
 	}
 
@@ -171,7 +231,7 @@ func runSSHAgent(ctx context.Context) (string, error) {
 	return sockPath, nil
 }
 
-func addSSHKey(ctx context.Context, authSock string, key string) error {
+func addSSHKey(ctx context.Context, authSock string, key sshKey) error {
 	conn, err := net.Dial("unix", authSock)
 	if err != nil {
 		return fmt.Errorf("error dialing with ssh agent %s: %s", authSock, err)
@@ -180,22 +240,52 @@ func addSSHKey(ctx context.Context, authSock string, key string) error {
 
 	agentClient := agent.NewClient(conn)
 
-	keyData, err := ioutil.ReadFile(key)
+	err = agentClient.Add(agent.AddedKey{PrivateKey: key.PrivateKey})
 	if err != nil {
-		return fmt.Errorf("error reading key file %s: %s", key, err)
+		return err
 	}
 
-	privateKey, err := ssh.ParseRawPrivateKey(keyData)
+	logboek.Context(ctx).Info().LogF("Added private key %s to ssh agent %s\n", key.Config.FilePath, authSock)
+
+	return nil
+}
+
+func parsePrivateSSHKey(cfg sshKeyConfig) (sshKey, error) {
+	keyData, err := ioutil.ReadFile(cfg.FilePath)
 	if err != nil {
-		return fmt.Errorf("error parsing private key %s: %s", key, err)
+		return sshKey{}, fmt.Errorf("error reading key file %q: %s", cfg.FilePath, err)
 	}
 
-	err = agentClient.Add(agent.AddedKey{PrivateKey: privateKey})
+	var privateKey interface{}
+
+	privateKey, err = ssh.ParseRawPrivateKey(keyData)
 	if err != nil {
-		return err
-	}
+		switch err.(type) {
+		case *ssh.PassphraseMissingError:
+			var passphrase []byte
+			if len(cfg.Passphrase) == 0 {
+				if terminal.IsTerminal(int(os.Stdin.Fd())) {
+					if data, err := secret_common.InputFromInteractiveStdin(fmt.Sprintf("Enter passphrase for ssh key %s: ", cfg.FilePath)); err != nil {
+						return sshKey{}, fmt.Errorf("error getting passphrase for ssh key %s: %s", cfg.FilePath, err)
+					} else {
+						passphrase = data
+					}
+				} else {
+					return sshKey{}, fmt.Errorf(`%w: please provide passphrase using --ssh-add="file://PASSPHRASE@FILEPATH" format`, err)
+				}
+			} else {
+				passphrase = cfg.Passphrase
+			}
 
-	logboek.Context(ctx).Info().LogF("Added private key %s to ssh agent %s\n", key, authSock)
+			privateKey, err = ssh.ParseRawPrivateKeyWithPassphrase(keyData, passphrase)
+			if err != nil {
+				return sshKey{}, fmt.Errorf("error parsing private key %s: %s", cfg.FilePath, err)
+			}
 
-	return nil
+		default:
+			return sshKey{}, fmt.Errorf("error parsing private key %s: %s", cfg.FilePath, err)
+		}
+	}
+
+	return sshKey{Config: cfg, PrivateKey: privateKey}, nil
 }