repro-run/runner/runner.go

package runner

import (
	"embed"
	"fmt"
	"io"
	"log"
	"os"
	"os/exec"
	"path"
	"strings"
)

//go:embed alpine/keys
var alpineKeys embed.FS

func Run(config Config, rootfs string, cache string, src string, w io.Writer) (err error) {
	if err = os.RemoveAll(rootfs); err != nil {
		return
	}

	if err = os.MkdirAll(path.Join(rootfs, "etc/apk/keys"), 0700); err != nil {
		return
	}
	if err = os.WriteFile(path.Join(rootfs, "etc/apk/repositories"), []byte(
		`https://dl-cdn.alpinelinux.org/alpine/v3.17/main
https://dl-cdn.alpinelinux.org/alpine/v3.17/community`), 0600); err != nil {
		return
	}

	if err = os.WriteFile(path.Join(rootfs, "etc/resolv.conf"), []byte(`nameserver 8.8.8.8`), 0644); err != nil {
		return
	}
	keys, err := alpineKeys.ReadDir("alpine/keys")
	if err != nil {
		return
	}
	for _, entry := range keys {
		o, err := os.Create(path.Join(rootfs, "etc/apk/keys/", entry.Name()))
		if err != nil {
			return err
		}
		s, err := alpineKeys.Open(path.Join("alpine/keys", entry.Name()))
		if err != nil {
			return err
		}
		if _, err = io.Copy(o, s); err != nil {
			return err
		}
	}

	if err = os.MkdirAll(path.Join(cache, "_var_cache_apk"), 0700); err != nil {
		return
	}
	if err = os.Symlink("/var/cache/apk", path.Join(rootfs, "etc/apk/cache")); err != nil {
		return
	}
	cmd := exec.Command("apk", "add",
		"--root", rootfs,
		"--initdb",
		"--cache-dir", path.Join(cache, "_var_cache_apk"),
		"apk-tools")
	if err = cmd.Run(); err != nil {
		return fmt.Errorf("apk add apk-tools: %w", err)
	}

	cached := append(config.Cache, "/var/cache/apk")
	var cachedParams []string
	for _, c := range cached {
		cacheDir := path.Join(cache, strings.ReplaceAll(c, "/", "_"))
		if err = os.MkdirAll(cacheDir, 0700); err != nil {
			return
		}
		cachedParams = append(cachedParams, "--bind", cacheDir, c)
	}

	tmp, err := os.MkdirTemp("", "repro-run-")
	if err != nil {
		return
	}
	defer os.RemoveAll(tmp)
	log.Println("/work = " + tmp)

	params := append(
		[]string{"--bind", rootfs, "/",
			"--ro-bind", src, "/src",
			"--dev-bind", "/dev", "/dev",
			"--bind", tmp, "/work",
			"--unshare-user", "--uid", "1000", "--gid", "1000",
			"--setenv", "HOME", "/home/repro",
			"--chdir", "/work",
		},
		cachedParams...)

	log.Println(strings.Join(params, " "))

	cmd = exec.Command("bwrap", append(params,
		"apk", "add", "--quiet", "busybox", "busybox-suid", "libc-utils", "alpine-baselayout", "alpine-conf", "alpine-release")...)
	cmd.Stdout = os.Stderr
	cmd.Stderr = os.Stderr
	if err = cmd.Run(); err != nil {
		return fmt.Errorf("bwrap apk add: %w", err)
	}
	cmd = exec.Command("bwrap", append(params,
		"--uid", "0",
		"adduser", "-u", "1000", "-D", "repro")...)
	cmd.Stdout = os.Stderr
	cmd.Stderr = os.Stderr
	if err = cmd.Run(); err != nil {
		return fmt.Errorf("bwrap adduser repro: %w", err)
	}

	cmd = exec.Command("bwrap", append(params, strings.Split(config.Command, " ")...)...)
	// cmd.Stdin = os.Stdin
	if w == nil {
		cmd.Stdout = os.Stdout
		cmd.Stderr = os.Stderr
	} else {
		cmd.Stdout = w
		cmd.Stderr = w
	}
	if err = cmd.Run(); err != nil {
		return fmt.Errorf("running Command: %w", err)
	}

	return
}

type Config struct {
	Command string
	Cache   []string
}