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833139f390
The recently-upgraded gosec linter has a rule for archive extraction code which may be vulnerable to directory traversal attacks, a.k.a. Zip Slip. Gosec's detection is unfortunately prone to false positives, however: it flags any filepath.Join call with an argument derived from a tar.Header value, irrespective of whether the resultant path is used for filesystem operations or if directory traversal attacks are guarded against. All of the lint errors reported by gosec appear to be false positives. Signed-off-by: Cory Snider <csnider@mirantis.com>
100 lines
2.9 KiB
Go
100 lines
2.9 KiB
Go
package archive // import "github.com/docker/docker/pkg/archive"
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import (
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"archive/tar"
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"os"
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"path/filepath"
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"strings"
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"github.com/docker/docker/pkg/system"
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"github.com/pkg/errors"
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"golang.org/x/sys/unix"
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)
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func getWhiteoutConverter(format WhiteoutFormat, inUserNS bool) (tarWhiteoutConverter, error) {
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if format == OverlayWhiteoutFormat {
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if inUserNS {
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return nil, errors.New("specifying OverlayWhiteoutFormat is not allowed in userns")
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}
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return overlayWhiteoutConverter{}, nil
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}
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return nil, nil
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}
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type overlayWhiteoutConverter struct {
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}
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func (overlayWhiteoutConverter) ConvertWrite(hdr *tar.Header, path string, fi os.FileInfo) (wo *tar.Header, err error) {
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// convert whiteouts to AUFS format
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if fi.Mode()&os.ModeCharDevice != 0 && hdr.Devmajor == 0 && hdr.Devminor == 0 {
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// we just rename the file and make it normal
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dir, filename := filepath.Split(hdr.Name)
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hdr.Name = filepath.Join(dir, WhiteoutPrefix+filename)
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hdr.Mode = 0600
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hdr.Typeflag = tar.TypeReg
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hdr.Size = 0
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}
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if fi.Mode()&os.ModeDir != 0 {
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// convert opaque dirs to AUFS format by writing an empty file with the prefix
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opaque, err := system.Lgetxattr(path, "trusted.overlay.opaque")
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if err != nil {
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return nil, err
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}
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if len(opaque) == 1 && opaque[0] == 'y' {
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if hdr.Xattrs != nil {
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delete(hdr.Xattrs, "trusted.overlay.opaque")
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}
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// create a header for the whiteout file
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// it should inherit some properties from the parent, but be a regular file
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wo = &tar.Header{
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Typeflag: tar.TypeReg,
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Mode: hdr.Mode & int64(os.ModePerm),
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Name: filepath.Join(hdr.Name, WhiteoutOpaqueDir),
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Size: 0,
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Uid: hdr.Uid,
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Uname: hdr.Uname,
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Gid: hdr.Gid,
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Gname: hdr.Gname,
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AccessTime: hdr.AccessTime,
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ChangeTime: hdr.ChangeTime,
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} //#nosec G305 -- An archive is being created, not extracted.
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}
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}
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return
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}
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func (c overlayWhiteoutConverter) ConvertRead(hdr *tar.Header, path string) (bool, error) {
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base := filepath.Base(path)
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dir := filepath.Dir(path)
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// if a directory is marked as opaque by the AUFS special file, we need to translate that to overlay
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if base == WhiteoutOpaqueDir {
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err := unix.Setxattr(dir, "trusted.overlay.opaque", []byte{'y'}, 0)
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if err != nil {
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return false, errors.Wrapf(err, "setxattr(%q, trusted.overlay.opaque=y)", dir)
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}
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// don't write the file itself
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return false, err
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}
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// if a file was deleted and we are using overlay, we need to create a character device
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if strings.HasPrefix(base, WhiteoutPrefix) {
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originalBase := base[len(WhiteoutPrefix):]
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originalPath := filepath.Join(dir, originalBase)
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if err := unix.Mknod(originalPath, unix.S_IFCHR, 0); err != nil {
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return false, errors.Wrapf(err, "failed to mknod(%q, S_IFCHR, 0)", originalPath)
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}
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if err := os.Chown(originalPath, hdr.Uid, hdr.Gid); err != nil {
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return false, err
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}
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// don't write the file itself
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return false, nil
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}
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return true, nil
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}
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