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move FileInfoHeaderNoLookups to separate tarheader package
This aligns with how containerd organizes the code, and allows consuming this function without requiring all the other code. Signed-off-by: Sebastiaan van Stijn <[email protected]>
1 parent a17ea4b commit cfc1738

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5 files changed

+152
-73
lines changed

5 files changed

+152
-73
lines changed

Diff for: ‎archive.go

+5-64
Original file line numberDiff line numberDiff line change
@@ -26,6 +26,7 @@ import (
2626

2727
"github.com/containerd/log"
2828
"github.com/klauspost/compress/zstd"
29+
"github.com/moby/go-archive/tarheader"
2930
"github.com/moby/patternmatcher"
3031
"github.com/moby/sys/sequential"
3132
"github.com/moby/sys/user"
@@ -475,71 +476,11 @@ func (compression *Compression) Extension() string {
475476
return ""
476477
}
477478

478-
// assert that we implement [tar.FileInfoNames].
479-
var _ tar.FileInfoNames = (*nosysFileInfo)(nil)
480-
481-
// nosysFileInfo hides the system-dependent info of the wrapped FileInfo to
482-
// prevent tar.FileInfoHeader from introspecting it and potentially calling into
483-
// glibc.
484-
//
485-
// It implements [tar.FileInfoNames] to further prevent [tar.FileInfoHeader]
486-
// from performing any lookups on go1.23 and up. see https://go.dev/issue/50102
487-
type nosysFileInfo struct {
488-
os.FileInfo
489-
}
490-
491-
// Uname stubs out looking up username. It implements [tar.FileInfoNames]
492-
// to prevent [tar.FileInfoHeader] from loading libraries to perform
493-
// username lookups.
494-
func (fi nosysFileInfo) Uname() (string, error) {
495-
return "", nil
496-
}
497-
498-
// Gname stubs out looking up group-name. It implements [tar.FileInfoNames]
499-
// to prevent [tar.FileInfoHeader] from loading libraries to perform
500-
// username lookups.
501-
func (fi nosysFileInfo) Gname() (string, error) {
502-
return "", nil
503-
}
504-
505-
func (fi nosysFileInfo) Sys() interface{} {
506-
// A Sys value of type *tar.Header is safe as it is system-independent.
507-
// The tar.FileInfoHeader function copies the fields into the returned
508-
// header without performing any OS lookups.
509-
if sys, ok := fi.FileInfo.Sys().(*tar.Header); ok {
510-
return sys
511-
}
512-
return nil
513-
}
514-
515-
// sysStat, if non-nil, populates hdr from system-dependent fields of fi.
516-
var sysStat func(fi os.FileInfo, hdr *tar.Header) error
517-
518479
// FileInfoHeaderNoLookups creates a partially-populated tar.Header from fi.
519480
//
520-
// Compared to the archive/tar.FileInfoHeader function, this function is safe to
521-
// call from a chrooted process as it does not populate fields which would
522-
// require operating system lookups. It behaves identically to
523-
// tar.FileInfoHeader when fi is a FileInfo value returned from
524-
// tar.Header.FileInfo().
525-
//
526-
// When fi is a FileInfo for a native file, such as returned from os.Stat() and
527-
// os.Lstat(), the returned Header value differs from one returned from
528-
// tar.FileInfoHeader in the following ways. The Uname and Gname fields are not
529-
// set as OS lookups would be required to populate them. The AccessTime and
530-
// ChangeTime fields are not currently set (not yet implemented) although that
531-
// is subject to change. Callers which require the AccessTime or ChangeTime
532-
// fields to be zeroed should explicitly zero them out in the returned Header
533-
// value to avoid any compatibility issues in the future.
481+
// Deprecated: use [tarheader.FileInfoHeaderNoLookups].
534482
func FileInfoHeaderNoLookups(fi os.FileInfo, link string) (*tar.Header, error) {
535-
hdr, err := tar.FileInfoHeader(nosysFileInfo{fi}, link)
536-
if err != nil {
537-
return nil, err
538-
}
539-
if sysStat != nil {
540-
return hdr, sysStat(fi, hdr)
541-
}
542-
return hdr, nil
483+
return tarheader.FileInfoHeaderNoLookups(fi, link)
543484
}
544485

545486
// FileInfoHeader creates a populated Header from fi.
@@ -550,7 +491,7 @@ func FileInfoHeaderNoLookups(fi os.FileInfo, link string) (*tar.Header, error) {
550491
// precision, and the Uname and Gname fields are only set when fi is a FileInfo
551492
// value returned from tar.Header.FileInfo().
552493
func FileInfoHeader(name string, fi os.FileInfo, link string) (*tar.Header, error) {
553-
hdr, err := FileInfoHeaderNoLookups(fi, link)
494+
hdr, err := tarheader.FileInfoHeaderNoLookups(fi, link)
554495
if err != nil {
555496
return nil, err
556497
}
@@ -1420,7 +1361,7 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
14201361
}
14211362
defer srcF.Close()
14221363

1423-
hdr, err := FileInfoHeaderNoLookups(srcSt, "")
1364+
hdr, err := tarheader.FileInfoHeaderNoLookups(srcSt, "")
14241365
if err != nil {
14251366
return err
14261367
}

Diff for: ‎archive_test.go

-9
Original file line numberDiff line numberDiff line change
@@ -1384,12 +1384,3 @@ func TestPigz(t *testing.T) {
13841384
assert.Equal(t, reflect.TypeOf(wrapper.Reader), reflect.TypeOf(&gzip.Reader{}))
13851385
}
13861386
}
1387-
1388-
func TestNosysFileInfo(t *testing.T) {
1389-
st, err := os.Stat("archive_test.go")
1390-
assert.NilError(t, err)
1391-
h, err := tar.FileInfoHeader(nosysFileInfo{st}, "")
1392-
assert.NilError(t, err)
1393-
assert.Check(t, h.Uname == "")
1394-
assert.Check(t, h.Gname == "")
1395-
}

Diff for: ‎tarheader/tarheader.go

+73
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
1+
package tarheader
2+
3+
import (
4+
"archive/tar"
5+
"os"
6+
)
7+
8+
// assert that we implement [tar.FileInfoNames].
9+
var _ tar.FileInfoNames = (*nosysFileInfo)(nil)
10+
11+
// nosysFileInfo hides the system-dependent info of the wrapped FileInfo to
12+
// prevent tar.FileInfoHeader from introspecting it and potentially calling into
13+
// glibc.
14+
//
15+
// It implements [tar.FileInfoNames] to further prevent [tar.FileInfoHeader]
16+
// from performing any lookups on go1.23 and up. see https://go.dev/issue/50102
17+
type nosysFileInfo struct {
18+
os.FileInfo
19+
}
20+
21+
// Uname stubs out looking up username. It implements [tar.FileInfoNames]
22+
// to prevent [tar.FileInfoHeader] from loading libraries to perform
23+
// username lookups.
24+
func (fi nosysFileInfo) Uname() (string, error) {
25+
return "", nil
26+
}
27+
28+
// Gname stubs out looking up group-name. It implements [tar.FileInfoNames]
29+
// to prevent [tar.FileInfoHeader] from loading libraries to perform
30+
// username lookups.
31+
func (fi nosysFileInfo) Gname() (string, error) {
32+
return "", nil
33+
}
34+
35+
func (fi nosysFileInfo) Sys() interface{} {
36+
// A Sys value of type *tar.Header is safe as it is system-independent.
37+
// The tar.FileInfoHeader function copies the fields into the returned
38+
// header without performing any OS lookups.
39+
if sys, ok := fi.FileInfo.Sys().(*tar.Header); ok {
40+
return sys
41+
}
42+
return nil
43+
}
44+
45+
// sysStat, if non-nil, populates hdr from system-dependent fields of fi.
46+
var sysStat func(fi os.FileInfo, hdr *tar.Header) error
47+
48+
// FileInfoHeaderNoLookups creates a partially-populated tar.Header from fi.
49+
//
50+
// Compared to the archive/tar.FileInfoHeader function, this function is safe to
51+
// call from a chrooted process as it does not populate fields which would
52+
// require operating system lookups. It behaves identically to
53+
// tar.FileInfoHeader when fi is a FileInfo value returned from
54+
// tar.Header.FileInfo().
55+
//
56+
// When fi is a FileInfo for a native file, such as returned from os.Stat() and
57+
// os.Lstat(), the returned Header value differs from one returned from
58+
// tar.FileInfoHeader in the following ways. The Uname and Gname fields are not
59+
// set as OS lookups would be required to populate them. The AccessTime and
60+
// ChangeTime fields are not currently set (not yet implemented) although that
61+
// is subject to change. Callers which require the AccessTime or ChangeTime
62+
// fields to be zeroed should explicitly zero them out in the returned Header
63+
// value to avoid any compatibility issues in the future.
64+
func FileInfoHeaderNoLookups(fi os.FileInfo, link string) (*tar.Header, error) {
65+
hdr, err := tar.FileInfoHeader(nosysFileInfo{fi}, link)
66+
if err != nil {
67+
return nil, err
68+
}
69+
if sysStat != nil {
70+
return hdr, sysStat(fi, hdr)
71+
}
72+
return hdr, nil
73+
}

Diff for: ‎tarheader/tarheader_test.go

+24
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,24 @@
1+
package tarheader
2+
3+
import (
4+
"archive/tar"
5+
"os"
6+
"testing"
7+
)
8+
9+
func TestNosysFileInfo(t *testing.T) {
10+
st, err := os.Stat("tarheader_test.go")
11+
if err != nil {
12+
t.Fatal(err)
13+
}
14+
h, err := tar.FileInfoHeader(nosysFileInfo{st}, "")
15+
if err != nil {
16+
t.Fatal(err)
17+
}
18+
if h.Uname != "" {
19+
t.Errorf("uname should be empty; got %v", h.Uname)
20+
}
21+
if h.Gname != "" {
22+
t.Errorf("gname should be empty; got %v", h.Uname)
23+
}
24+
}

Diff for: ‎tarheader/tarheader_unix.go

+50
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,50 @@
1+
//go:build !windows
2+
3+
package tarheader
4+
5+
import (
6+
"archive/tar"
7+
"os"
8+
"runtime"
9+
"syscall"
10+
11+
"golang.org/x/sys/unix"
12+
)
13+
14+
func init() {
15+
sysStat = statUnix
16+
}
17+
18+
// statUnix populates hdr from system-dependent fields of fi without performing
19+
// any OS lookups.
20+
func statUnix(fi os.FileInfo, hdr *tar.Header) error {
21+
// Devmajor and Devminor are only needed for special devices.
22+
23+
// In FreeBSD, RDev for regular files is -1 (unless overridden by FS):
24+
// https://cgit.freebsd.org/src/tree/sys/kern/vfs_default.c?h=stable/13#n1531
25+
// (NODEV is -1: https://cgit.freebsd.org/src/tree/sys/sys/param.h?h=stable/13#n241).
26+
27+
// ZFS in particular does not override the default:
28+
// https://cgit.freebsd.org/src/tree/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c?h=stable/13#n2027
29+
30+
// Since `Stat_t.Rdev` is uint64, the cast turns -1 into (2^64 - 1).
31+
// Such large values cannot be encoded in a tar header.
32+
if runtime.GOOS == "freebsd" && hdr.Typeflag != tar.TypeBlock && hdr.Typeflag != tar.TypeChar {
33+
return nil
34+
}
35+
s, ok := fi.Sys().(*syscall.Stat_t)
36+
if !ok {
37+
return nil
38+
}
39+
40+
hdr.Uid = int(s.Uid)
41+
hdr.Gid = int(s.Gid)
42+
43+
if s.Mode&unix.S_IFBLK != 0 ||
44+
s.Mode&unix.S_IFCHR != 0 {
45+
hdr.Devmajor = int64(unix.Major(uint64(s.Rdev))) //nolint: unconvert
46+
hdr.Devminor = int64(unix.Minor(uint64(s.Rdev))) //nolint: unconvert
47+
}
48+
49+
return nil
50+
}

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