dotcloud/docker

//go:build !windows

package archive // import "github.com/docker/docker/pkg/archive"

import (
    "archive/tar"
    "errors"
    "os"
    "path/filepath"
    "runtime"
    "strings"
    "syscall"

    "github.com/docker/docker/pkg/idtools"
    "github.com/docker/docker/pkg/system"
    "golang.org/x/sys/unix"
)

func init() {
    sysStat = statUnix
}

// addLongPathPrefix adds the Windows long path prefix to the path provided if
// it does not already have it. It is a no-op on platforms other than Windows.
func addLongPathPrefix(srcPath string) string {
    return srcPath
}

// getWalkRoot calculates the root path when performing a TarWithOptions.
// We use a separate function as this is platform specific. On Linux, we
// can't use filepath.Join(srcPath,include) because this will clean away
// a trailing "." or "/" which may be important.
func getWalkRoot(srcPath string, include string) string {
    return strings.TrimSuffix(srcPath, string(filepath.Separator)) + string(filepath.Separator) + include
}

// chmodTarEntry is used to adjust the file permissions used in tar header based
// on the platform the archival is done.
func chmodTarEntry(perm os.FileMode) os.FileMode {
    return perm // noop for unix as golang APIs provide perm bits correctly
}

// statUnix populates hdr from system-dependent fields of fi without performing
// any OS lookups.
func statUnix(fi os.FileInfo, hdr *tar.Header) error {
    // Devmajor and Devminor are only needed for special devices.

    // In FreeBSD, RDev for regular files is -1 (unless overridden by FS):
    // https://cgit.freebsd.org/src/tree/sys/kern/vfs_default.c?h=stable/13#n1531
    // (NODEV is -1: https://cgit.freebsd.org/src/tree/sys/sys/param.h?h=stable/13#n241).

    // ZFS in particular does not override the default:
    // https://cgit.freebsd.org/src/tree/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c?h=stable/13#n2027

    // Since `Stat_t.Rdev` is uint64, the cast turns -1 into (2^64 - 1).
    // Such large values cannot be encoded in a tar header.
    if runtime.GOOS == "freebsd" && hdr.Typeflag != tar.TypeBlock && hdr.Typeflag != tar.TypeChar {
        return nil
    }
    s, ok := fi.Sys().(*syscall.Stat_t)
    if !ok {
        return nil
    }

    hdr.Uid = int(s.Uid)
    hdr.Gid = int(s.Gid)

    if s.Mode&unix.S_IFBLK != 0 ||
        s.Mode&unix.S_IFCHR != 0 {
        hdr.Devmajor = int64(unix.Major(uint64(s.Rdev))) //nolint: unconvert
        hdr.Devminor = int64(unix.Minor(uint64(s.Rdev))) //nolint: unconvert
    }

    return nil
}

func getInodeFromStat(stat interface{}) (inode uint64, err error) {
    s, ok := stat.(*syscall.Stat_t)

    if ok {
        inode = s.Ino
    }

    return
}

func getFileUIDGID(stat interface{}) (idtools.Identity, error) {
    s, ok := stat.(*syscall.Stat_t)

    if !ok {
        return idtools.Identity{}, errors.New("cannot convert stat value to syscall.Stat_t")
    }
    return idtools.Identity{UID: int(s.Uid), GID: int(s.Gid)}, nil
}

// handleTarTypeBlockCharFifo is an OS-specific helper function used by
// createTarFile to handle the following types of header: Block; Char; Fifo.
//
// Creating device nodes is not supported when running in a user namespace,
// produces a [syscall.EPERM] in most cases.
func handleTarTypeBlockCharFifo(hdr *tar.Header, path string) error {
    mode := uint32(hdr.Mode & 0o7777)
    switch hdr.Typeflag {
    case tar.TypeBlock:
        mode |= unix.S_IFBLK
    case tar.TypeChar:
        mode |= unix.S_IFCHR
    case tar.TypeFifo:
        mode |= unix.S_IFIFO
    }

    return system.Mknod(path, mode, int(system.Mkdev(hdr.Devmajor, hdr.Devminor)))
}

func handleLChmod(hdr *tar.Header, path string, hdrInfo os.FileInfo) error {
    if hdr.Typeflag == tar.TypeLink {
        if fi, err := os.Lstat(hdr.Linkname); err == nil && (fi.Mode()&os.ModeSymlink == 0) {
            if err := os.Chmod(path, hdrInfo.Mode()); err != nil {
                return err
            }
        }
    } else if hdr.Typeflag != tar.TypeSymlink {
        if err := os.Chmod(path, hdrInfo.Mode()); err != nil {
            return err
        }
    }
    return nil
}