feature: add chroot provision step in chroot builder

builder/osc/chroot/builder.go

@@ -261,6 +261,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		},
 		&StepMountExtra{},
 		&StepCopyFiles{},
+		&StepChrootProvision{},
 	)
 
 	// Run!

builder/osc/chroot/communicator.go

@@ -0,0 +1,142 @@
+package chroot
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"github.com/hashicorp/packer/packer"
+	"github.com/hashicorp/packer/packer/tmp"
+)
+
+// Communicator is a special communicator that works by executing
+// commands locally but within a chroot.
+type Communicator struct {
+	Chroot     string
+	CmdWrapper CommandWrapper
+}
+
+func (c *Communicator) Start(cmd *packer.RemoteCmd) error {
+	// need extra escapes for the command since we're wrapping it in quotes
+	cmd.Command = strconv.Quote(cmd.Command)
+	command, err := c.CmdWrapper(
+		fmt.Sprintf("chroot %s /bin/sh -c %s", c.Chroot, cmd.Command))
+	if err != nil {
+		return err
+	}
+
+	localCmd := ShellCommand(command)
+	localCmd.Stdin = cmd.Stdin
+	localCmd.Stdout = cmd.Stdout
+	localCmd.Stderr = cmd.Stderr
+	log.Printf("Executing: %s %#v", localCmd.Path, localCmd.Args)
+	if err := localCmd.Start(); err != nil {
+		return err
+	}
+
+	go func() {
+		exitStatus := 0
+		if err := localCmd.Wait(); err != nil {
+			if exitErr, ok := err.(*exec.ExitError); ok {
+				exitStatus = 1
+
+				// There is no process-independent way to get the REAL
+				// exit status so we just try to go deeper.
+				if status, ok := exitErr.Sys().(syscall.WaitStatus); ok {
+					exitStatus = status.ExitStatus()
+				}
+			}
+		}
+
+		log.Printf(
+			"Chroot execution exited with '%d': '%s'",
+			exitStatus, cmd.Command)
+		cmd.SetExited(exitStatus)
+	}()
+
+	return nil
+}
+
+func (c *Communicator) Upload(dst string, r io.Reader, fi *os.FileInfo) error {
+	dst = filepath.Join(c.Chroot, dst)
+	log.Printf("Uploading to chroot dir: %s", dst)
+	tf, err := tmp.File("packer-amazon-chroot")
+	if err != nil {
+		return fmt.Errorf("Error preparing shell script: %s", err)
+	}
+	defer os.Remove(tf.Name())
+
+	if _, err := io.Copy(tf, r); err != nil {
+		return err
+	}
+
+	cpCmd, err := c.CmdWrapper(fmt.Sprintf("cp %s %s", tf.Name(), dst))
+	if err != nil {
+		return err
+	}
+
+	return ShellCommand(cpCmd).Run()
+}
+
+func (c *Communicator) UploadDir(dst string, src string, exclude []string) error {
+	// If src ends with a trailing "/", copy from "src/." so that
+	// directory contents (including hidden files) are copied, but the
+	// directory "src" is omitted.  BSD does this automatically when
+	// the source contains a trailing slash, but linux does not.
+	if src[len(src)-1] == '/' {
+		src = src + "."
+	}
+
+	// TODO: remove any file copied if it appears in `exclude`
+	chrootDest := filepath.Join(c.Chroot, dst)
+
+	log.Printf("Uploading directory '%s' to '%s'", src, chrootDest)
+	cpCmd, err := c.CmdWrapper(fmt.Sprintf("cp -R '%s' %s", src, chrootDest))
+	if err != nil {
+		return err
+	}
+
+	var stderr bytes.Buffer
+	cmd := ShellCommand(cpCmd)
+	cmd.Env = append(cmd.Env, "LANG=C")
+	cmd.Env = append(cmd.Env, os.Environ()...)
+	cmd.Stderr = &stderr
+	err = cmd.Run()
+	if err == nil {
+		return err
+	}
+
+	if strings.Contains(stderr.String(), "No such file") {
+		// This just means that the directory was empty. Just ignore it.
+		return nil
+	}
+
+	return err
+}
+
+func (c *Communicator) DownloadDir(src string, dst string, exclude []string) error {
+	return fmt.Errorf("DownloadDir is not implemented for amazon-chroot")
+}
+
+func (c *Communicator) Download(src string, w io.Writer) error {
+	src = filepath.Join(c.Chroot, src)
+	log.Printf("Downloading from chroot dir: %s", src)
+	f, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if _, err := io.Copy(w, f); err != nil {
+		return err
+	}
+
+	return nil
+}

builder/osc/chroot/step_chroot_provision.go

@@ -0,0 +1,37 @@
+package chroot
+
+import (
+	"context"
+	"log"
+
+	"github.com/hashicorp/packer/helper/multistep"
+	"github.com/hashicorp/packer/packer"
+)
+
+// StepChrootProvision provisions the instance within a chroot.
+type StepChrootProvision struct {
+}
+
+func (s *StepChrootProvision) Run(_ context.Context, state multistep.StateBag) multistep.StepAction {
+	hook := state.Get("hook").(packer.Hook)
+	mountPath := state.Get("mount_path").(string)
+	ui := state.Get("ui").(packer.Ui)
+	wrappedCommand := state.Get("wrappedCommand").(CommandWrapper)
+
+	// Create our communicator
+	comm := &Communicator{
+		Chroot:     mountPath,
+		CmdWrapper: wrappedCommand,
+	}
+
+	// Provision
+	log.Println("Running the provision hook")
+	if err := hook.Run(packer.HookProvision, ui, comm, nil); err != nil {
+		state.Put("error", err)
+		return multistep.ActionHalt
+	}
+
+	return multistep.ActionContinue
+}
+
+func (s *StepChrootProvision) Cleanup(state multistep.StateBag) {}