Added IdentityFile support for SSH executor

docs/configuration/advanced-configuration.md

@@ -173,10 +173,11 @@ This defines the SSH connection parameters.
 
 | Parameter  | Explanation |
 | ---------- | ----------- |
-| `host`     | where to connect (overriden when using `docker-ssh`) |
+| `host`     | where to connect (overridden when using `docker-ssh`) |
 | `port`     | specify port, default: 22 |
 | `user`     | specify user |
 | `password` | specify password |
+| `identity_file` | specify file path to SSH private key (id_rsa, id_dsa or id_edcsa). The file needs to be stored unencrypted |
 
 Example:
 
@@ -186,6 +187,7 @@ Example:
   port = "22"
   user = "root"
   password = "production-server-password"
+  identity_file = "
 ```
 
 ### Note

ssh/ssh_command.go

@@ -9,6 +9,7 @@ import (
 	"code.google.com/p/go.crypto/ssh"
 
 	"gitlab.com/gitlab-org/gitlab-ci-multi-runner/helpers"
+	"io/ioutil"
 )
 
 type Command struct {
@@ -25,14 +26,31 @@ type Command struct {
 	client *ssh.Client
 }
 
-func (s *Command) getSSHAuthMethods() []ssh.AuthMethod {
+func (s *Command) getSSHKey(identityFile string) (key ssh.Signer, err error) {
+	buf, err := ioutil.ReadFile(identityFile)
+	if err != nil {
+		return nil, err
+	}
+	key, err = ssh.ParsePrivateKey(buf)
+	return key, err
+}
+
+func (s *Command) getSSHAuthMethods() ([]ssh.AuthMethod, error) {
 	var methods []ssh.AuthMethod
 
 	if s.Password != nil {
 		methods = append(methods, ssh.Password(*s.Password))
 	}
 
-	return methods
+	if s.IdentityFile != nil {
+		key, err := s.getSSHKey(*s.IdentityFile)
+		if err != nil {
+			return nil, err
+		}
+		methods = append(methods, ssh.PublicKeys(key))
+	}
+
+	return methods, nil
 }
 
 func (s *Command) Connect() error {
@@ -40,9 +58,14 @@ func (s *Command) Connect() error {
 	user := helpers.StringOrDefault(s.User, "root")
 	port := helpers.StringOrDefault(s.Port, "22")
 
+	methods, err := s.getSSHAuthMethods()
+	if err != nil {
+		return err
+	}
+
 	config := &ssh.ClientConfig{
 		User: user,
-		Auth: s.getSSHAuthMethods(),
+		Auth: methods,
 	}
 
 	connectRetries := s.ConnectRetries

ssh/ssh_config.go

 package ssh
 
 type Config struct {
-	User     *string `toml:"user" json:"user"`
-	Password *string `toml:"password" json:"password"`
-	Host     *string `toml:"host" json:"host"`
-	Port     *string `toml:"port" json:"port"`
+	User         *string `toml:"user" json:"user"`
+	Password     *string `toml:"password" json:"password"`
+	Host         *string `toml:"host" json:"host"`
+	Port         *string `toml:"port" json:"port"`
+	IdentityFile *string `toml:"identity_file" json:"identity_file"`
 }