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tar.go
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tar.go
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package archiver
import (
"archive/tar"
"bytes"
"fmt"
"io"
"log"
"os"
"path"
"path/filepath"
"strconv"
"strings"
)
// Tar provides facilities for operating TAR archives.
// See http://www.gnu.org/software/tar/manual/html_node/Standard.html.
type Tar struct {
// Whether to overwrite existing files; if false,
// an error is returned if the file exists.
OverwriteExisting bool
// Whether to make all the directories necessary
// to create a tar archive in the desired path.
MkdirAll bool
// Whether to preserve the file path in the archive
PreservePath bool
// A single top-level folder can be implicitly
// created by the Archive or Unarchive methods
// if the files to be added to the archive
// or the files to be extracted from the archive
// do not all have a common root. This roughly
// mimics the behavior of archival tools integrated
// into OS file browsers which create a subfolder
// to avoid unexpectedly littering the destination
// folder with potentially many files, causing a
// problematic cleanup/organization situation.
// This feature is available for both creation
// and extraction of archives, but may be slightly
// inefficient with lots and lots of files,
// especially on extraction.
ImplicitTopLevelFolder bool
// Strip number of leading paths. This feature is available
// only during unpacking of the entire archive.
StripComponents int
// If true, errors encountered during reading
// or writing a single file will be logged and
// the operation will continue on remaining files.
ContinueOnError bool
tw *tar.Writer
tr *tar.Reader
readerWrapFn func(io.Reader) (io.Reader, error)
writerWrapFn func(io.Writer) (io.Writer, error)
cleanupWrapFn func()
}
// CheckExt ensures the file extension matches the format.
func (*Tar) CheckExt(filename string) error {
if !strings.HasSuffix(filename, ".tar") {
return fmt.Errorf("filename must have a .tar extension")
}
return nil
}
// CheckPath ensures that the filename has not been crafted to perform path traversal attacks
func (*Tar) CheckPath(to, filename string) error {
to, _ = filepath.Abs(to) //explicit the destination folder to prevent that 'string.HasPrefix' check can be 'bypassed' when no destination folder is supplied in input
dest := filepath.Join(to, filename)
//prevent path traversal attacks
if !strings.HasPrefix(dest, to) {
return &IllegalPathError{AbsolutePath: dest, Filename: filename}
}
return nil
}
// Archive creates a tarball file at destination containing
// the files listed in sources. The destination must end with
// ".tar". File paths can be those of regular files or
// directories; directories will be recursively added.
func (t *Tar) Archive(sources []string, destination string) error {
err := t.CheckExt(destination)
if t.writerWrapFn == nil && err != nil {
return fmt.Errorf("checking extension: %v", err)
}
if !t.OverwriteExisting && fileExists(destination) {
return fmt.Errorf("file already exists: %s", destination)
}
// make the folder to contain the resulting archive
// if it does not already exist
destDir := filepath.Dir(destination)
if t.MkdirAll && !fileExists(destDir) {
err := mkdir(destDir, 0755)
if err != nil {
return fmt.Errorf("making folder for destination: %v", err)
}
}
out, err := os.Create(destination)
if err != nil {
return fmt.Errorf("creating %s: %v", destination, err)
}
defer out.Close()
err = t.Create(out)
if err != nil {
return fmt.Errorf("creating tar: %v", err)
}
defer t.Close()
var topLevelFolder string
if t.ImplicitTopLevelFolder && multipleTopLevels(sources) {
topLevelFolder = folderNameFromFileName(destination)
}
for _, source := range sources {
err := t.writeWalk(source, topLevelFolder, destination)
if err != nil {
return fmt.Errorf("walking %s: %v", source, err)
}
}
return nil
}
// Unarchive unpacks the .tar file at source to destination.
// Destination will be treated as a folder name.
func (t *Tar) Unarchive(source, destination string) error {
if !fileExists(destination) && t.MkdirAll {
err := mkdir(destination, 0755)
if err != nil {
return fmt.Errorf("preparing destination: %v", err)
}
}
// if the files in the archive do not all share a common
// root, then make sure we extract to a single subfolder
// rather than potentially littering the destination...
if t.ImplicitTopLevelFolder {
var err error
destination, err = t.addTopLevelFolder(source, destination)
if err != nil {
return fmt.Errorf("scanning source archive: %v", err)
}
}
file, err := os.Open(source)
if err != nil {
return fmt.Errorf("opening source archive: %v", err)
}
defer file.Close()
err = t.Open(file, 0)
if err != nil {
return fmt.Errorf("opening tar archive for reading: %v", err)
}
defer t.Close()
for {
err := t.untarNext(destination)
if err == io.EOF {
break
}
if err != nil {
if t.ContinueOnError || IsIllegalPathError(err) {
log.Printf("[ERROR] Reading file in tar archive: %v", err)
continue
}
return fmt.Errorf("reading file in tar archive: %v", err)
}
}
return nil
}
// addTopLevelFolder scans the files contained inside
// the tarball named sourceArchive and returns a modified
// destination if all the files do not share the same
// top-level folder.
func (t *Tar) addTopLevelFolder(sourceArchive, destination string) (string, error) {
file, err := os.Open(sourceArchive)
if err != nil {
return "", fmt.Errorf("opening source archive: %v", err)
}
defer file.Close()
// if the reader is to be wrapped, ensure we do that now
// or we will not be able to read the archive successfully
reader := io.Reader(file)
if t.readerWrapFn != nil {
reader, err = t.readerWrapFn(reader)
if err != nil {
return "", fmt.Errorf("wrapping reader: %v", err)
}
}
if t.cleanupWrapFn != nil {
defer t.cleanupWrapFn()
}
tr := tar.NewReader(reader)
var files []string
for {
hdr, err := tr.Next()
if err == io.EOF {
break
}
if err != nil {
return "", fmt.Errorf("scanning tarball's file listing: %v", err)
}
files = append(files, hdr.Name)
}
if multipleTopLevels(files) {
destination = filepath.Join(destination, folderNameFromFileName(sourceArchive))
}
return destination, nil
}
func (t *Tar) untarNext(destination string) error {
f, err := t.Read()
if err != nil {
return err // don't wrap error; calling loop must break on io.EOF
}
defer f.Close()
header, ok := f.Header.(*tar.Header)
if !ok {
return fmt.Errorf("expected header to be *tar.Header but was %T", f.Header)
}
errPath := t.CheckPath(destination, header.Name)
if errPath != nil {
return fmt.Errorf("checking path traversal attempt: %v", errPath)
}
if t.StripComponents > 0 {
if strings.Count(header.Name, "/") < t.StripComponents {
return nil // skip path with fewer components
}
for i := 0; i < t.StripComponents; i++ {
slash := strings.Index(header.Name, "/")
header.Name = header.Name[slash+1:]
}
}
return t.untarFile(f, destination, header)
}
func (t *Tar) untarFile(f File, destination string, hdr *tar.Header) error {
to := filepath.Join(destination, hdr.Name)
// do not overwrite existing files, if configured
if !f.IsDir() && !t.OverwriteExisting && fileExists(to) {
return fmt.Errorf("file already exists: %s", to)
}
switch hdr.Typeflag {
case tar.TypeDir:
return mkdir(to, f.Mode())
case tar.TypeReg, tar.TypeRegA, tar.TypeChar, tar.TypeBlock, tar.TypeFifo, tar.TypeGNUSparse:
return writeNewFile(to, f, f.Mode())
case tar.TypeSymlink:
return writeNewSymbolicLink(to, hdr.Linkname)
case tar.TypeLink:
return writeNewHardLink(to, filepath.Join(destination, hdr.Linkname))
case tar.TypeXGlobalHeader:
return nil // ignore the pax global header from git-generated tarballs
default:
return fmt.Errorf("%s: unknown type flag: %c", hdr.Name, hdr.Typeflag)
}
}
func (t *Tar) writeWalk(source, topLevelFolder, destination string) error {
sourceInfo, err := os.Stat(source)
if err != nil {
return fmt.Errorf("%s: stat: %v", source, err)
}
destAbs, err := filepath.Abs(destination)
if err != nil {
return fmt.Errorf("%s: getting absolute path of destination %s: %v", source, destination, err)
}
return filepath.Walk(source, func(fpath string, info os.FileInfo, err error) error {
handleErr := func(err error) error {
if t.ContinueOnError {
log.Printf("[ERROR] Walking %s: %v", fpath, err)
return nil
}
return err
}
if err != nil {
return handleErr(fmt.Errorf("traversing %s: %v", fpath, err))
}
if info == nil {
return handleErr(fmt.Errorf("no file info"))
}
// make sure we do not copy our output file into itself
fpathAbs, err := filepath.Abs(fpath)
if err != nil {
return handleErr(fmt.Errorf("%s: getting absolute path: %v", fpath, err))
}
if within(fpathAbs, destAbs) {
return nil
}
if t.PreservePath {
topLevelFolder = filepath.Dir(source)
}
// build the name to be used within the archive
nameInArchive, err := makeNameInArchive(sourceInfo, source, topLevelFolder, fpath)
if err != nil {
return handleErr(err)
}
var file io.ReadCloser
if info.Mode().IsRegular() {
file, err = os.Open(fpath)
if err != nil {
return handleErr(fmt.Errorf("%s: opening: %v", fpath, err))
}
defer file.Close()
}
err = t.Write(File{
FileInfo: FileInfo{
FileInfo: info,
CustomName: nameInArchive,
},
OriginalPath: fpath,
ReadCloser: file,
})
if err != nil {
return handleErr(fmt.Errorf("%s: writing: %s", fpath, err))
}
return nil
})
}
// Create opens t for writing a tar archive to out.
func (t *Tar) Create(out io.Writer) error {
if t.tw != nil {
return fmt.Errorf("tar archive is already created for writing")
}
// wrapping writers allows us to output
// compressed tarballs, for example
if t.writerWrapFn != nil {
var err error
out, err = t.writerWrapFn(out)
if err != nil {
return fmt.Errorf("wrapping writer: %v", err)
}
}
t.tw = tar.NewWriter(out)
return nil
}
// Write writes f to t, which must have been opened for writing first.
func (t *Tar) Write(f File) error {
if t.tw == nil {
return fmt.Errorf("tar archive was not created for writing first")
}
if f.FileInfo == nil {
return fmt.Errorf("no file info")
}
if f.FileInfo.Name() == "" {
return fmt.Errorf("missing file name")
}
var linkTarget string
if isSymlink(f) {
var err error
linkTarget, err = os.Readlink(f.OriginalPath)
if err != nil {
return fmt.Errorf("%s: readlink: %v", f.Name(), err)
}
}
hdr, err := tar.FileInfoHeader(f, filepath.ToSlash(linkTarget))
if err != nil {
return fmt.Errorf("%s: making header: %v", f.Name(), err)
}
err = t.tw.WriteHeader(hdr)
if err != nil {
return fmt.Errorf("%s: writing header: %w", hdr.Name, err)
}
if f.IsDir() {
return nil // directories have no contents
}
if hdr.Typeflag == tar.TypeReg {
if f.ReadCloser == nil {
return fmt.Errorf("%s: no way to read file contents", f.Name())
}
_, err := io.Copy(t.tw, f)
if err != nil {
return fmt.Errorf("%s: copying contents: %w", f.Name(), err)
}
}
return nil
}
// Open opens t for reading an archive from
// in. The size parameter is not used.
func (t *Tar) Open(in io.Reader, size int64) error {
if t.tr != nil {
return fmt.Errorf("tar archive is already open for reading")
}
// wrapping readers allows us to open compressed tarballs
if t.readerWrapFn != nil {
var err error
in, err = t.readerWrapFn(in)
if err != nil {
return fmt.Errorf("wrapping file reader: %v", err)
}
}
t.tr = tar.NewReader(in)
return nil
}
// Read reads the next file from t, which must have
// already been opened for reading. If there are no
// more files, the error is io.EOF. The File must
// be closed when finished reading from it.
func (t *Tar) Read() (File, error) {
if t.tr == nil {
return File{}, fmt.Errorf("tar archive is not open")
}
hdr, err := t.tr.Next()
if err != nil {
return File{}, err // don't wrap error; preserve io.EOF
}
file := File{
FileInfo: hdr.FileInfo(),
Header: hdr,
ReadCloser: ReadFakeCloser{t.tr},
}
return file, nil
}
// Close closes the tar archive(s) opened by Create and Open.
func (t *Tar) Close() error {
var err error
if t.tr != nil {
t.tr = nil
}
if t.tw != nil {
tw := t.tw
t.tw = nil
err = tw.Close()
}
// make sure cleanup of "Reader/Writer wrapper"
// (say that ten times fast) happens AFTER the
// underlying stream is closed
if t.cleanupWrapFn != nil {
t.cleanupWrapFn()
}
return err
}
// Walk calls walkFn for each visited item in archive.
func (t *Tar) Walk(archive string, walkFn WalkFunc) error {
file, err := os.Open(archive)
if err != nil {
return fmt.Errorf("opening archive file: %v", err)
}
defer file.Close()
err = t.Open(file, 0)
if err != nil {
return fmt.Errorf("opening archive: %v", err)
}
defer t.Close()
for {
f, err := t.Read()
if err == io.EOF {
break
}
if err != nil {
if t.ContinueOnError {
log.Printf("[ERROR] Opening next file: %v", err)
continue
}
return fmt.Errorf("opening next file: %v", err)
}
err = walkFn(f)
if err != nil {
if err == ErrStopWalk {
break
}
if t.ContinueOnError {
log.Printf("[ERROR] Walking %s: %v", f.Name(), err)
continue
}
return fmt.Errorf("walking %s: %v", f.Name(), err)
}
}
return nil
}
// Extract extracts a single file from the tar archive.
// If the target is a directory, the entire folder will
// be extracted into destination.
func (t *Tar) Extract(source, target, destination string) error {
// target refers to a path inside the archive, which should be clean also
target = path.Clean(target)
// if the target ends up being a directory, then
// we will continue walking and extracting files
// until we are no longer within that directory
var targetDirPath string
return t.Walk(source, func(f File) error {
th, ok := f.Header.(*tar.Header)
if !ok {
return fmt.Errorf("expected header to be *tar.Header but was %T", f.Header)
}
// importantly, cleaning the path strips tailing slash,
// which must be appended to folders within the archive
name := path.Clean(th.Name)
if f.IsDir() && target == name {
targetDirPath = path.Dir(name)
}
if within(target, th.Name) {
// either this is the exact file we want, or is
// in the directory we want to extract
// build the filename we will extract to
end, err := filepath.Rel(targetDirPath, th.Name)
if err != nil {
return fmt.Errorf("relativizing paths: %v", err)
}
th.Name = end
// relativize any hardlink names
if th.Typeflag == tar.TypeLink {
th.Linkname = filepath.Join(filepath.Base(filepath.Dir(th.Linkname)), filepath.Base(th.Linkname))
}
err = t.untarFile(f, destination, th)
if err != nil {
return fmt.Errorf("extracting file %s: %v", th.Name, err)
}
// if our target was not a directory, stop walk
if targetDirPath == "" {
return ErrStopWalk
}
} else if targetDirPath != "" {
// finished walking the entire directory
return ErrStopWalk
}
return nil
})
}
// Match returns true if the format of file matches this
// type's format. It should not affect reader position.
func (*Tar) Match(file io.ReadSeeker) (bool, error) {
currentPos, err := file.Seek(0, io.SeekCurrent)
if err != nil {
return false, err
}
_, err = file.Seek(0, 0)
if err != nil {
return false, err
}
defer func() {
_, _ = file.Seek(currentPos, io.SeekStart)
}()
buf := make([]byte, tarBlockSize)
if _, err = io.ReadFull(file, buf); err != nil {
return false, nil
}
return hasTarHeader(buf), nil
}
// hasTarHeader checks passed bytes has a valid tar header or not. buf must
// contain at least 512 bytes and if not, it always returns false.
func hasTarHeader(buf []byte) bool {
if len(buf) < tarBlockSize {
return false
}
b := buf[148:156]
b = bytes.Trim(b, " \x00") // clean up all spaces and null bytes
if len(b) == 0 {
return false // unknown format
}
hdrSum, err := strconv.ParseUint(string(b), 8, 64)
if err != nil {
return false
}
// According to the go official archive/tar, Sun tar uses signed byte
// values so this calcs both signed and unsigned
var usum uint64
var sum int64
for i, c := range buf {
if 148 <= i && i < 156 {
c = ' ' // checksum field itself is counted as branks
}
usum += uint64(uint8(c))
sum += int64(int8(c))
}
if hdrSum != usum && int64(hdrSum) != sum {
return false // invalid checksum
}
return true
}
func (t *Tar) String() string { return "tar" }
// NewTar returns a new, default instance ready to be customized and used.
func NewTar() *Tar {
return &Tar{
MkdirAll: true,
}
}
const tarBlockSize = 512
// Compile-time checks to ensure type implements desired interfaces.
var (
_ = Reader(new(Tar))
_ = Writer(new(Tar))
_ = Archiver(new(Tar))
_ = Unarchiver(new(Tar))
_ = Walker(new(Tar))
_ = Extractor(new(Tar))
_ = Matcher(new(Tar))
_ = ExtensionChecker(new(Tar))
_ = FilenameChecker(new(Tar))
)
// DefaultTar is a default instance that is conveniently ready to use.
var DefaultTar = NewTar()