Add SSH backend (#861)

Add SSH backend that runs commands via SSH.

Close #848

pipeline/backend/ssh/ssh.go

@@ -0,0 +1,153 @@
+package ssh
+
+import (
+	"context"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/melbahja/goph"
+
+	"github.com/woodpecker-ci/woodpecker/pipeline/backend/types"
+	"github.com/woodpecker-ci/woodpecker/shared/constant"
+)
+
+type ssh struct {
+	cmd        *goph.Cmd
+	output     io.ReadCloser
+	client     *goph.Client
+	workingdir string
+}
+
+type readCloser struct {
+	io.Reader
+}
+
+func (c readCloser) Close() error {
+	return nil
+}
+
+// make sure local implements Engine
+var _ types.Engine = &ssh{}
+
+// New returns a new ssh Engine.
+func New() types.Engine {
+	return &ssh{}
+}
+
+func (e *ssh) Name() string {
+	return "ssh"
+}
+
+func (e *ssh) IsAvailable() bool {
+	return os.Getenv("WOODPECKER_BACKEND_SSH_KEY") != "" || os.Getenv("WOODPECKER_BACKEND_SSH_PASSWORD") != ""
+}
+
+func (e *ssh) Load() error {
+	cmd, err := e.client.Command("/bin/env", "mktemp", "-d", "-p", "/tmp", "woodpecker-ssh-XXXXXXXXXX")
+	if err != nil {
+		return err
+	}
+
+	dir, err := cmd.Output()
+	if err != nil {
+		return err
+	}
+
+	e.workingdir = string(dir)
+	address := os.Getenv("WOODPECKER_BACKEND_SSH_ADDRESS")
+	if address == "" {
+		return fmt.Errorf("missing SSH address")
+	}
+	user := os.Getenv("WOODPECKER_BACKEND_SSH_USER")
+	if user == "" {
+		return fmt.Errorf("missing SSH user")
+	}
+	var auth goph.Auth
+	if file, has := os.LookupEnv("WOODPECKER_BACKEND_SSH_KEY"); has {
+		var err error
+		auth, err = goph.Key(file, os.Getenv("WOODPECKER_BACKEND_SSH_KEY_PASSWORD"))
+		if err != nil {
+			return err
+		}
+	} else {
+		auth = goph.Password(os.Getenv("WOODPECKER_BACKEND_SSH_PASSWORD"))
+	}
+	client, err := goph.New(user, address, auth)
+	if err != nil {
+		return err
+	}
+	e.client = client
+	return nil
+}
+
+// Setup the pipeline environment.
+func (e *ssh) Setup(ctx context.Context, proc *types.Config) error {
+	return nil
+}
+
+// Exec the pipeline step.
+func (e *ssh) Exec(ctx context.Context, proc *types.Step) error {
+	// Get environment variables
+	Command := []string{}
+	for a, b := range proc.Environment {
+		if a != "HOME" && a != "SHELL" { // Don't override $HOME and $SHELL
+			Command = append(Command, a+"="+b)
+		}
+	}
+
+	if proc.Image == constant.DefaultCloneImage {
+		// Default clone step
+		Command = append(Command, "CI_WORKSPACE="+e.workingdir+"/"+proc.Environment["CI_REPO"])
+		Command = append(Command, "plugin-git")
+	} else {
+		// Use "image name" as run command
+		Command = append(Command, proc.Image[18:len(proc.Image)-7])
+		Command = append(Command, "-c")
+
+		// Decode script and delete initial lines
+		// Deleting the initial lines removes netrc support but adds compatibility for more shells like fish
+		Script, _ := base64.RawStdEncoding.DecodeString(proc.Environment["CI_SCRIPT"])
+		Command = append(Command, "cd "+e.workingdir+"/"+proc.Environment["CI_REPO"]+" && "+string(Script)[strings.Index(string(Script), "\n\n")+2:])
+	}
+
+	// Prepare command
+	var err error
+	e.cmd, err = e.client.CommandContext(ctx, "/bin/env", Command...)
+	if err != nil {
+		return err
+	}
+
+	// Get output and redirect Stderr to Stdout
+	std, _ := e.cmd.StdoutPipe()
+	e.output = readCloser{std}
+	e.cmd.Stderr = e.cmd.Stdout
+
+	return e.cmd.Start()
+}
+
+// Wait for the pipeline step to complete and returns
+// the completion results.
+func (e *ssh) Wait(context.Context, *types.Step) (*types.State, error) {
+	return &types.State{
+		Exited: true,
+	}, e.cmd.Wait()
+}
+
+// Tail the pipeline step logs.
+func (e *ssh) Tail(context.Context, *types.Step) (io.ReadCloser, error) {
+	return e.output, nil
+}
+
+// Destroy the pipeline environment.
+func (e *ssh) Destroy(context.Context, *types.Config) error {
+	e.client.Close()
+	sftp, err := e.client.NewSftp()
+	if err != nil {
+		return err
+	}
+
+	return sftp.RemoveDirectory(e.workingdir)
+}