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resticinstaller.go
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resticinstaller.go
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package resticinstaller
import (
"archive/zip"
"bytes"
"compress/bzip2"
"context"
"crypto/sha256"
"encoding/hex"
"errors"
"fmt"
"io"
"net/http"
"os"
"path"
"runtime"
"strings"
"sync"
"github.com/garethgeorge/backrest/internal/config"
"go.uber.org/zap"
)
var (
ErrResticNotFound = errors.New("no restic binary")
)
var (
RequiredResticVersion = "0.16.4"
findResticMu sync.Mutex
didTryInstall bool
)
func resticBinName() string {
if runtime.GOOS == "windows" {
return fmt.Sprintf("restic-%v.exe", RequiredResticVersion)
}
return fmt.Sprintf("restic-%v", RequiredResticVersion)
}
func resticDownloadURL(version string) string {
if runtime.GOOS == "windows" {
// restic is only built for 386 and amd64 on Windows, default to amd64 for other platforms (e.g. arm64.)
arch := "amd64"
if runtime.GOARCH == "386" || runtime.GOARCH == "amd64" {
arch = runtime.GOARCH
}
return fmt.Sprintf("https://github.com/restic/restic/releases/download/v%v/restic_%v_windows_%v.zip", version, version, arch)
}
return fmt.Sprintf("https://github.com/restic/restic/releases/download/v%v/restic_%v_%v_%v.bz2", version, version, runtime.GOOS, runtime.GOARCH)
}
func hashDownloadURL(version string) string {
return fmt.Sprintf("https://github.com/restic/restic/releases/download/v%v/SHA256SUMS", version)
}
func sigDownloadURL(version string) string {
return fmt.Sprintf("https://github.com/restic/restic/releases/download/v%v/SHA256SUMS.asc", version)
}
// getURL downloads the given url and returns the response body as a string.
func getURL(url string) ([]byte, error) {
resp, err := http.Get(url)
if err != nil {
return nil, fmt.Errorf("http GET %v: %w", url, err)
}
defer resp.Body.Close()
var body bytes.Buffer
_, err = io.Copy(&body, resp.Body)
if err != nil {
return nil, fmt.Errorf("copy response body to buffer: %w", err)
}
return body.Bytes(), nil
}
func verify(sha256 string) error {
sha256sums, err := getURL(hashDownloadURL(RequiredResticVersion))
if err != nil {
return fmt.Errorf("get sha256sums: %w", err)
}
signature, err := getURL(sigDownloadURL(RequiredResticVersion))
if err != nil {
return fmt.Errorf("get signature: %w", err)
}
if ok, err := gpgVerify(sha256sums, signature); !ok || err != nil {
return fmt.Errorf("gpg verification failed: ok=%v err=%v", ok, err)
}
if !strings.Contains(string(sha256sums), sha256) {
fmt.Fprintf(os.Stderr, "sha256sums:\n%v\n", string(sha256sums))
return fmt.Errorf("sha256sums do not contain %v", sha256)
}
return nil
}
// downloadFile downloads a file from the given url and saves it to the given path. The sha256 checksum of the file is returned on success.
func downloadFile(url string, downloadPath string) (string, error) {
// Download ur as a file and save it to path
req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, url, nil)
if err != nil {
return "", err
}
req.Header.Set("Accept", "application/octet-stream")
resp, err := http.DefaultClient.Do(req)
if err != nil {
return "", fmt.Errorf("http GET %v: %w", url, err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return "", fmt.Errorf("http GET %v: %v", url, resp.Status)
}
body, err := io.ReadAll(resp.Body)
if err != nil {
return "", fmt.Errorf("read response body: %w", err)
}
hash := sha256.Sum256(body)
if strings.HasSuffix(url, ".bz2") {
zap.S().Infof("decompressing bz2 archive (size=%v)...", len(body))
body, err = io.ReadAll(bzip2.NewReader(bytes.NewReader(body)))
if err != nil {
return "", fmt.Errorf("bz2 decompress body: %w", err)
}
} else if strings.HasSuffix(url, ".zip") {
zap.S().Infof("decompressing zip archive (size=%v)...", len(body))
archive, err := zip.NewReader(bytes.NewReader(body), int64(len(body)))
if err != nil {
return "", fmt.Errorf("open zip archive: %w", err)
}
if len(archive.File) != 1 {
return "", fmt.Errorf("expected zip archive to contain exactly one file, got %v", len(archive.File))
}
f, err := archive.File[0].Open()
if err != nil {
return "", fmt.Errorf("open zip archive file %v: %w", archive.File[0].Name, err)
}
body, err = io.ReadAll(f)
if err != nil {
return "", fmt.Errorf("read zip archive file %v: %w", archive.File[0].Name, err)
}
}
out, err := os.Create(downloadPath)
if err != nil {
return "", fmt.Errorf("create file %v: %w", downloadPath, err)
}
defer out.Close()
if err != nil {
return "", fmt.Errorf("create file %v: %w", downloadPath, err)
}
_, err = io.Copy(out, bytes.NewReader(body))
if err != nil {
return "", fmt.Errorf("copy response body to file %v: %w", downloadPath, err)
}
return hex.EncodeToString(hash[:]), nil
}
func installResticIfNotExists(resticInstallPath string) error {
// withFlock is used to ensure tests pass; when running on CI multiple tests may try to install restic at the same time.
return withFlock(path.Join(config.DataDir(), "install.lock"), func() error {
if _, err := os.Stat(resticInstallPath); err == nil {
// file is now installed, probably by another process. We can return.
return nil
}
if err := os.MkdirAll(path.Dir(resticInstallPath), 0755); err != nil {
return fmt.Errorf("create restic install directory %v: %w", path.Dir(resticInstallPath), err)
}
hash, err := downloadFile(resticDownloadURL(RequiredResticVersion), resticInstallPath+".tmp")
if err != nil {
return err
}
if err := verify(hash); err != nil {
os.Remove(resticInstallPath) // try to remove the bad binary.
return fmt.Errorf("failed to verify the authenticity of the downloaded restic binary: %v", err)
}
if err := os.Chmod(resticInstallPath+".tmp", 0755); err != nil {
return fmt.Errorf("chmod executable %v: %w", resticInstallPath, err)
}
if err := os.Rename(resticInstallPath+".tmp", resticInstallPath); err != nil {
return fmt.Errorf("rename %v.tmp to %v: %w", resticInstallPath, resticInstallPath, err)
}
return nil
})
}
func removeOldVersions(installDir string) {
files, err := os.ReadDir(installDir)
if err != nil {
zap.S().Errorf("remove old restic versions: read dir %v: %v", installDir, err)
return
}
for _, file := range files {
if !strings.HasPrefix(file.Name(), "restic-") || strings.Contains(file.Name(), RequiredResticVersion) {
continue
}
if err := os.Remove(path.Join(installDir, file.Name())); err != nil {
zap.S().Errorf("remove old restic version %v: %v", file.Name(), err)
}
}
}
// FindOrInstallResticBinary first tries to find the restic binary if provided as an environment variable. Otherwise it downloads restic if not already installed.
func FindOrInstallResticBinary() (string, error) {
findResticMu.Lock()
defer findResticMu.Unlock()
// Check if restic is provided.
resticBin := config.ResticBinPath()
if resticBin != "" {
if _, err := os.Stat(resticBin); err != nil {
if !errors.Is(err, os.ErrNotExist) {
return "", fmt.Errorf("stat(%v): %w", resticBin, err)
}
return "", fmt.Errorf("no binary found at path %v: %w", resticBin, ErrResticNotFound)
}
return resticBin, nil
}
// Search the PATH for the specific restic version.
resticBinName := resticBinName()
for _, dir := range strings.Split(os.Getenv("PATH"), string(os.PathListSeparator)) {
candidatePath := path.Join(dir, resticBinName)
if _, err := os.Stat(candidatePath); err == nil {
return candidatePath, nil
}
}
// Check for restic installation in data directory.
resticInstallPath := path.Join(config.DataDir(), resticBinName)
if runtime.GOOS == "windows" {
programFiles := os.Getenv("programfiles")
resticInstallPath = path.Join(programFiles, "backrest", resticBinName)
}
// Install restic if not found.
if _, err := os.Stat(resticInstallPath); err != nil {
if !errors.Is(err, os.ErrNotExist) {
return "", fmt.Errorf("could not stat restic binary at %v: %w", resticBin, err)
}
if didTryInstall {
return "", fmt.Errorf("already tried to install: %w", ErrResticNotFound)
}
didTryInstall = true
zap.S().Infof("installing restic %v to %v...", resticInstallPath, RequiredResticVersion)
if err := installResticIfNotExists(resticInstallPath); err != nil {
return "", fmt.Errorf("install restic: %w", err)
}
zap.S().Infof("installed restic %v", RequiredResticVersion)
removeOldVersions(path.Dir(resticInstallPath))
}
return resticInstallPath, nil
}