deps: update to github.com/cyphar/filepath-securejoin@v0.4.1

This release includes a minor breaking API change that requires us to rework the types of our wrappers, but there is no practical behaviour change. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> (cherry picked from commit 70e500e7d1) Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
2026-07-11 06:03:57 +08:00 · 2025-01-13 18:54:47 +11:00
parent 456d770f22
commit 00f4a5cc4f
15 changed files with 403 additions and 50 deletions
@@ -12,7 +12,7 @@ require (
 	github.com/cilium/ebpf v0.16.0
 	github.com/containerd/console v1.0.4
 	github.com/coreos/go-systemd/v22 v22.5.0
-	github.com/cyphar/filepath-securejoin v0.3.5
+	github.com/cyphar/filepath-securejoin v0.4.1
 	github.com/docker/go-units v0.5.0
 	github.com/godbus/dbus/v5 v5.1.0
 	github.com/moby/sys/mountinfo v0.7.1
@@ -9,8 +9,8 @@ github.com/coreos/go-systemd/v22 v22.5.0 h1:RrqgGjYQKalulkV8NGVIfkXQf6YYmOyiJKk8
 github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/cpuguy83/go-md2man/v2 v2.0.2 h1:p1EgwI/C7NhT0JmVkwCD2ZBK8j4aeHQX2pMHHBfMQ6w=
 github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
-github.com/cyphar/filepath-securejoin v0.3.5 h1:L81NHjquoQmcPgXcttUS9qTSR/+bXry6pbSINQGpjj4=
-github.com/cyphar/filepath-securejoin v0.3.5/go.mod h1:edhVd3c6OXKjUmSrVa/tGJRS9joFTxlslFCAyaxigkE=
+github.com/cyphar/filepath-securejoin v0.4.1 h1:JyxxyPEaktOD+GAnqIqTf9A8tHyAG22rowi7HkoSU1s=
+github.com/cyphar/filepath-securejoin v0.4.1/go.mod h1:Sdj7gXlvMcPZsbhwhQ33GguGLDGQL7h7bg04C/+u9jI=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -68,9 +68,8 @@ github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpE
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
-github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
-github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/syndtr/gocapability v0.0.0-20200815063812-42c35b437635 h1:kdXcSzyDtseVEc4yCz2qF8ZrQvIDBJLl4S1c3GCXmoI=
 github.com/syndtr/gocapability v0.0.0-20200815063812-42c35b437635/go.mod h1:hkRG7XYTFWNJGYcbNJQlaLq0fg1yr4J4t/NcTQtrfww=
 github.com/urfave/cli v1.22.14 h1:ebbhrRiGK2i4naQJr+1Xj92HXZCrK7MsyTS/ob3HnAk=
@@ -287,9 +287,6 @@ func IsLexicallyInRoot(root, path string) bool {
 // try to detect any symlink components in the path while we are doing the
 // MkdirAll.
 //
-// NOTE: Unlike os.MkdirAll, mode is not Go's os.FileMode, it is the unix mode
-// (the suid/sgid/sticky bits are not the same as for os.FileMode).
-//
 // NOTE: If unsafePath is a subpath of root, we assume that you have already
 // called SecureJoin and so we use the provided path verbatim without resolving
 // any symlinks (this is done in a way that avoids symlink-exchange races).
@@ -300,7 +297,7 @@ func IsLexicallyInRoot(root, path string) bool {
 // handling if unsafePath has already been scoped within the rootfs (this is
 // needed for a lot of runc callers and fixing this would require reworking a
 // lot of path logic).
-func MkdirAllInRootOpen(root, unsafePath string, mode uint32) (_ *os.File, Err error) {
+func MkdirAllInRootOpen(root, unsafePath string, mode os.FileMode) (_ *os.File, Err error) {
 	// If the path is already "within" the root, get the path relative to the
 	// root and use that as the unsafe path. This is necessary because a lot of
 	// MkdirAllInRootOpen callers have already done SecureJoin, and refactoring
@@ -334,12 +331,12 @@ func MkdirAllInRootOpen(root, unsafePath string, mode uint32) (_ *os.File, Err e
 	}
 	defer rootDir.Close()

-	return securejoin.MkdirAllHandle(rootDir, unsafePath, int(mode))
+	return securejoin.MkdirAllHandle(rootDir, unsafePath, mode)
 }

 // MkdirAllInRoot is a wrapper around MkdirAllInRootOpen which closes the
 // returned handle, for callers that don't need to use it.
-func MkdirAllInRoot(root, unsafePath string, mode uint32) error {
+func MkdirAllInRoot(root, unsafePath string, mode os.FileMode) error {
 	f, err := MkdirAllInRootOpen(root, unsafePath, mode)
 	if err == nil {
 		_ = f.Close()
@@ -6,7 +6,74 @@ and this project adheres to [Semantic Versioning](http://semver.org/).

 ## [Unreleased] ##

+## [0.4.1] - 2025-01-28 ##
+
+### Fixed ###
+- The restrictions added for `root` paths passed to `SecureJoin` in 0.4.0 was
+  found to be too strict and caused some regressions when folks tried to
+  update, so this restriction has been relaxed to only return an error if the
+  path contains a `..` component. We still recommend users use `filepath.Clean`
+  (and even `filepath.EvalSymlinks`) on the `root` path they are using, but at
+  least you will no longer be punished for "trivial" unclean paths.
+
+## [0.4.0] - 2025-01-13 ##
+
+### Breaking ####
+- `SecureJoin(VFS)` will now return an error if the provided `root` is not a
+  `filepath.Clean`'d path.
+
+  While it is ultimately the responsibility of the caller to ensure the root is
+  a safe path to use, passing a path like `/symlink/..` as a root would result
+  in the `SecureJoin`'d path being placed in `/` even though `/symlink/..`
+  might be a different directory, and so we should more strongly discourage
+  such usage.
+
+  All major users of `securejoin.SecureJoin` already ensure that the paths they
+  provide are safe (and this is ultimately a question of user error), but
+  removing this foot-gun is probably a good idea. Of course, this is
+  necessarily a breaking API change (though we expect no real users to be
+  affected by it).
+
+  Thanks to [Erik Sjölund](https://github.com/eriksjolund), who initially
+  reported this issue as a possible security issue.
+
+- `MkdirAll` and `MkdirHandle` now take an `os.FileMode`-style mode argument
+  instead of a raw `unix.S_*`-style mode argument, which may cause compile-time
+  type errors depending on how you use `filepath-securejoin`. For most users,
+  there will be no change in behaviour aside from the type change (as the
+  bottom `0o777` bits are the same in both formats, and most users are probably
+  only using those bits).
+
+  However, if you were using `unix.S_ISVTX` to set the sticky bit with
+  `MkdirAll(Handle)` you will need to switch to `os.ModeSticky` otherwise you
+  will get a runtime error with this update. In addition, the error message you
+  will get from passing `unix.S_ISUID` and `unix.S_ISGID` will be different as
+  they are treated as invalid bits now (note that previously passing said bits
+  was also an error).
+
+## [0.3.6] - 2024-12-17 ##
+
+### Compatibility ###
+- The minimum Go version requirement for `filepath-securejoin` is now Go 1.18
+  (we use generics internally).
+
+  For reference, `filepath-securejoin@v0.3.0` somewhat-arbitrarily bumped the
+  Go version requirement to 1.21.
+
+  While we did make some use of Go 1.21 stdlib features (and in principle Go
+  versions <= 1.21 are no longer even supported by upstream anymore), some
+  downstreams have complained that the version bump has meant that they have to
+  do workarounds when backporting fixes that use the new `filepath-securejoin`
+  API onto old branches. This is not an ideal situation, but since using this
+  library is probably better for most downstreams than a hand-rolled
+  workaround, we now have compatibility shims that allow us to build on older
+  Go versions.
+- Lower minimum version requirement for `golang.org/x/sys` to `v0.18.0` (we
+  need the wrappers for `fsconfig(2)`), which should also make backporting
+  patches to older branches easier.
+
 ## [0.3.5] - 2024-12-06 ##
+
 ### Fixed ###
 - `MkdirAll` will now no longer return an `EEXIST` error if two racing
  processes are creating the same directory. We will still verify that the path
@@ -171,7 +238,10 @@ This is our first release of `github.com/cyphar/filepath-securejoin`,
 containing a full implementation with a coverage of 93.5% (the only missing
 cases are the error cases, which are hard to mocktest at the moment).

-[Unreleased]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.5...HEAD
+[Unreleased]: https://github.com/cyphar/filepath-securejoin/compare/v0.4.1...HEAD
+[0.4.1]: https://github.com/cyphar/filepath-securejoin/compare/v0.4.0...v0.4.1
+[0.4.0]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.6...v0.4.0
+[0.3.6]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.5...v0.3.6
 [0.3.5]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.4...v0.3.5
 [0.3.4]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.3...v0.3.4
 [0.3.3]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.2...v0.3.3
@@ -1 +1 @@
-0.3.5
+0.4.1
@@ -0,0 +1,18 @@
+//go:build linux && go1.20
+
+// Copyright (C) 2024 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securejoin
+
+import (
+	"fmt"
+)
+
+// wrapBaseError is a helper that is equivalent to fmt.Errorf("%w: %w"), except
+// that on pre-1.20 Go versions only errors.Is() works properly (errors.Unwrap)
+// is only guaranteed to give you baseErr.
+func wrapBaseError(baseErr, extraErr error) error {
+	return fmt.Errorf("%w: %w", extraErr, baseErr)
+}
@@ -0,0 +1,38 @@
+//go:build linux && !go1.20
+
+// Copyright (C) 2024 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securejoin
+
+import (
+	"fmt"
+)
+
+type wrappedError struct {
+	inner   error
+	isError error
+}
+
+func (err wrappedError) Is(target error) bool {
+	return err.isError == target
+}
+
+func (err wrappedError) Unwrap() error {
+	return err.inner
+}
+
+func (err wrappedError) Error() string {
+	return fmt.Sprintf("%v: %v", err.isError, err.inner)
+}
+
+// wrapBaseError is a helper that is equivalent to fmt.Errorf("%w: %w"), except
+// that on pre-1.20 Go versions only errors.Is() works properly (errors.Unwrap)
+// is only guaranteed to give you baseErr.
+func wrapBaseError(baseErr, extraErr error) error {
+	return wrappedError{
+		inner:   baseErr,
+		isError: extraErr,
+	}
+}
@@ -0,0 +1,32 @@
+//go:build linux && go1.21
+
+// Copyright (C) 2024 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securejoin
+
+import (
+	"slices"
+	"sync"
+)
+
+func slices_DeleteFunc[S ~[]E, E any](slice S, delFn func(E) bool) S {
+	return slices.DeleteFunc(slice, delFn)
+}
+
+func slices_Contains[S ~[]E, E comparable](slice S, val E) bool {
+	return slices.Contains(slice, val)
+}
+
+func slices_Clone[S ~[]E, E any](slice S) S {
+	return slices.Clone(slice)
+}
+
+func sync_OnceValue[T any](f func() T) func() T {
+	return sync.OnceValue(f)
+}
+
+func sync_OnceValues[T1, T2 any](f func() (T1, T2)) func() (T1, T2) {
+	return sync.OnceValues(f)
+}
@@ -0,0 +1,124 @@
+//go:build linux && !go1.21
+
+// Copyright (C) 2024 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securejoin
+
+import (
+	"sync"
+)
+
+// These are very minimal implementations of functions that appear in Go 1.21's
+// stdlib, included so that we can build on older Go versions. Most are
+// borrowed directly from the stdlib, and a few are modified to be "obviously
+// correct" without needing to copy too many other helpers.
+
+// clearSlice is equivalent to the builtin clear from Go 1.21.
+// Copied from the Go 1.24 stdlib implementation.
+func clearSlice[S ~[]E, E any](slice S) {
+	var zero E
+	for i := range slice {
+		slice[i] = zero
+	}
+}
+
+// Copied from the Go 1.24 stdlib implementation.
+func slices_IndexFunc[S ~[]E, E any](s S, f func(E) bool) int {
+	for i := range s {
+		if f(s[i]) {
+			return i
+		}
+	}
+	return -1
+}
+
+// Copied from the Go 1.24 stdlib implementation.
+func slices_DeleteFunc[S ~[]E, E any](s S, del func(E) bool) S {
+	i := slices_IndexFunc(s, del)
+	if i == -1 {
+		return s
+	}
+	// Don't start copying elements until we find one to delete.
+	for j := i + 1; j < len(s); j++ {
+		if v := s[j]; !del(v) {
+			s[i] = v
+			i++
+		}
+	}
+	clearSlice(s[i:]) // zero/nil out the obsolete elements, for GC
+	return s[:i]
+}
+
+// Similar to the stdlib slices.Contains, except that we don't have
+// slices.Index so we need to use slices.IndexFunc for this non-Func helper.
+func slices_Contains[S ~[]E, E comparable](s S, v E) bool {
+	return slices_IndexFunc(s, func(e E) bool { return e == v }) >= 0
+}
+
+// Copied from the Go 1.24 stdlib implementation.
+func slices_Clone[S ~[]E, E any](s S) S {
+	// Preserve nil in case it matters.
+	if s == nil {
+		return nil
+	}
+	return append(S([]E{}), s...)
+}
+
+// Copied from the Go 1.24 stdlib implementation.
+func sync_OnceValue[T any](f func() T) func() T {
+	var (
+		once   sync.Once
+		valid  bool
+		p      any
+		result T
+	)
+	g := func() {
+		defer func() {
+			p = recover()
+			if !valid {
+				panic(p)
+			}
+		}()
+		result = f()
+		f = nil
+		valid = true
+	}
+	return func() T {
+		once.Do(g)
+		if !valid {
+			panic(p)
+		}
+		return result
+	}
+}
+
+// Copied from the Go 1.24 stdlib implementation.
+func sync_OnceValues[T1, T2 any](f func() (T1, T2)) func() (T1, T2) {
+	var (
+		once  sync.Once
+		valid bool
+		p     any
+		r1    T1
+		r2    T2
+	)
+	g := func() {
+		defer func() {
+			p = recover()
+			if !valid {
+				panic(p)
+			}
+		}()
+		r1, r2 = f()
+		f = nil
+		valid = true
+	}
+	return func() (T1, T2) {
+		once.Do(g)
+		if !valid {
+			panic(p)
+		}
+		return r1, r2
+	}
+}
@@ -1,5 +1,5 @@
 // Copyright (C) 2014-2015 Docker Inc & Go Authors. All rights reserved.
-// Copyright (C) 2017-2024 SUSE LLC. All rights reserved.
+// Copyright (C) 2017-2025 SUSE LLC. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

@@ -24,6 +24,31 @@ func IsNotExist(err error) bool {
 	return errors.Is(err, os.ErrNotExist) || errors.Is(err, syscall.ENOTDIR) || errors.Is(err, syscall.ENOENT)
 }

+// errUnsafeRoot is returned if the user provides SecureJoinVFS with a path
+// that contains ".." components.
+var errUnsafeRoot = errors.New("root path provided to SecureJoin contains '..' components")
+
+// stripVolume just gets rid of the Windows volume included in a path. Based on
+// some godbolt tests, the Go compiler is smart enough to make this a no-op on
+// Linux.
+func stripVolume(path string) string {
+	return path[len(filepath.VolumeName(path)):]
+}
+
+// hasDotDot checks if the path contains ".." components in a platform-agnostic
+// way.
+func hasDotDot(path string) bool {
+	// If we are on Windows, strip any volume letters. It turns out that
+	// C:..\foo may (or may not) be a valid pathname and we need to handle that
+	// leading "..".
+	path = stripVolume(path)
+	// Look for "/../" in the path, but we need to handle leading and trailing
+	// ".."s by adding separators. Doing this with filepath.Separator is ugly
+	// so just convert to Unix-style "/" first.
+	path = filepath.ToSlash(path)
+	return strings.Contains("/"+path+"/", "/../")
+}
+
 // SecureJoinVFS joins the two given path components (similar to [filepath.Join]) except
 // that the returned path is guaranteed to be scoped inside the provided root
 // path (when evaluated). Any symbolic links in the path are evaluated with the
@@ -46,7 +71,22 @@ func IsNotExist(err error) bool {
 // provided via direct input or when evaluating symlinks. Therefore:
 //
 // "C:\Temp" + "D:\path\to\file.txt" results in "C:\Temp\path\to\file.txt"
+//
+// If the provided root is not [filepath.Clean] then an error will be returned,
+// as such root paths are bordering on somewhat unsafe and using such paths is
+// not best practice. We also strongly suggest that any root path is first
+// fully resolved using [filepath.EvalSymlinks] or otherwise constructed to
+// avoid containing symlink components. Of course, the root also *must not* be
+// attacker-controlled.
 func SecureJoinVFS(root, unsafePath string, vfs VFS) (string, error) {
+	// The root path must not contain ".." components, otherwise when we join
+	// the subpath we will end up with a weird path. We could work around this
+	// in other ways but users shouldn't be giving us non-lexical root paths in
+	// the first place.
+	if hasDotDot(root) {
+		return "", errUnsafeRoot
+	}
+
 	// Use the os.* VFS implementation if none was specified.
 	if vfs == nil {
 		vfs = osVFS{}
@@ -59,9 +99,10 @@ func SecureJoinVFS(root, unsafePath string, vfs VFS) (string, error) {
 		linksWalked   int
 	)
 	for remainingPath != "" {
-		if v := filepath.VolumeName(remainingPath); v != "" {
-			remainingPath = remainingPath[len(v):]
-		}
+		// On Windows, if we managed to end up at a path referencing a volume,
+		// drop the volume to make sure we don't end up with broken paths or
+		// escaping the root volume.
+		remainingPath = stripVolume(remainingPath)

 		// Get the next path component.
 		var part string
@@ -12,7 +12,6 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"slices"
 	"strings"

 	"golang.org/x/sys/unix"
@@ -113,7 +112,7 @@ func (s *symlinkStack) push(dir *os.File, remainingPath, linkTarget string) erro
 		return nil
 	}
 	// Split the link target and clean up any "" parts.
-	linkTargetParts := slices.DeleteFunc(
+	linkTargetParts := slices_DeleteFunc(
 		strings.Split(linkTarget, "/"),
 		func(part string) bool { return part == "" || part == "." })

@@ -11,7 +11,6 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"slices"
 	"strings"

 	"golang.org/x/sys/unix"
@@ -22,6 +21,33 @@ var (
 	errPossibleAttack = errors.New("possible attack detected")
 )

+// modePermExt is like os.ModePerm except that it also includes the set[ug]id
+// and sticky bits.
+const modePermExt = os.ModePerm | os.ModeSetuid | os.ModeSetgid | os.ModeSticky
+
+//nolint:cyclop // this function needs to handle a lot of cases
+func toUnixMode(mode os.FileMode) (uint32, error) {
+	sysMode := uint32(mode.Perm())
+	if mode&os.ModeSetuid != 0 {
+		sysMode |= unix.S_ISUID
+	}
+	if mode&os.ModeSetgid != 0 {
+		sysMode |= unix.S_ISGID
+	}
+	if mode&os.ModeSticky != 0 {
+		sysMode |= unix.S_ISVTX
+	}
+	// We don't allow file type bits.
+	if mode&os.ModeType != 0 {
+		return 0, fmt.Errorf("%w %+.3o (%s): type bits not permitted", errInvalidMode, mode, mode)
+	}
+	// We don't allow other unknown modes.
+	if mode&^modePermExt != 0 || sysMode&unix.S_IFMT != 0 {
+		return 0, fmt.Errorf("%w %+.3o (%s): unknown mode bits", errInvalidMode, mode, mode)
+	}
+	return sysMode, nil
+}
+
 // MkdirAllHandle is equivalent to [MkdirAll], except that it is safer to use
 // in two respects:
 //
@@ -40,17 +66,17 @@ var (
 // a brand new lookup of unsafePath (such as with [SecureJoin] or openat2) after
 // doing [MkdirAll]. If you intend to open the directory after creating it, you
 // should use MkdirAllHandle.
-func MkdirAllHandle(root *os.File, unsafePath string, mode int) (_ *os.File, Err error) {
-	// Make sure there are no os.FileMode bits set.
-	if mode&^0o7777 != 0 {
-		return nil, fmt.Errorf("%w for mkdir 0o%.3o", errInvalidMode, mode)
+func MkdirAllHandle(root *os.File, unsafePath string, mode os.FileMode) (_ *os.File, Err error) {
+	unixMode, err := toUnixMode(mode)
+	if err != nil {
+		return nil, err
 	}
 	// On Linux, mkdirat(2) (and os.Mkdir) silently ignore the suid and sgid
 	// bits. We could also silently ignore them but since we have very few
 	// users it seems more prudent to return an error so users notice that
 	// these bits will not be set.
-	if mode&^0o1777 != 0 {
-		return nil, fmt.Errorf("%w for mkdir 0o%.3o: suid and sgid are ignored by mkdir", errInvalidMode, mode)
+	if unixMode&^0o1777 != 0 {
+		return nil, fmt.Errorf("%w for mkdir %+.3o: suid and sgid are ignored by mkdir", errInvalidMode, mode)
 	}

 	// Try to open as much of the path as possible.
@@ -93,7 +119,7 @@ func MkdirAllHandle(root *os.File, unsafePath string, mode int) (_ *os.File, Err
 	}

 	remainingParts := strings.Split(remainingPath, string(filepath.Separator))
-	if slices.Contains(remainingParts, "..") {
+	if slices_Contains(remainingParts, "..") {
 		// The path contained ".." components after the end of the "real"
 		// components. We could try to safely resolve ".." here but that would
 		// add a bunch of extra logic for something that it's not clear even
@@ -105,9 +131,6 @@ func MkdirAllHandle(root *os.File, unsafePath string, mode int) (_ *os.File, Err
 		return nil, fmt.Errorf("%w: yet-to-be-created path %q contains '..' components", unix.ENOENT, remainingPath)
 	}

-	// Make sure the mode doesn't have any type bits.
-	mode &^= unix.S_IFMT
-
 	// Create the remaining components.
 	for _, part := range remainingParts {
 		switch part {
@@ -124,11 +147,15 @@ func MkdirAllHandle(root *os.File, unsafePath string, mode int) (_ *os.File, Err
 		// directory at the same time as us. In that case, just continue on as
 		// if we created it (if the created inode is not a directory, the
 		// following open call will fail).
-		if err := unix.Mkdirat(int(currentDir.Fd()), part, uint32(mode)); err != nil && !errors.Is(err, unix.EEXIST) {
+		if err := unix.Mkdirat(int(currentDir.Fd()), part, unixMode); err != nil && !errors.Is(err, unix.EEXIST) {
 			err = &os.PathError{Op: "mkdirat", Path: currentDir.Name() + "/" + part, Err: err}
 			// Make the error a bit nicer if the directory is dead.
-			if err2 := isDeadInode(currentDir); err2 != nil {
-				err = fmt.Errorf("%w (%w)", err, err2)
+			if deadErr := isDeadInode(currentDir); deadErr != nil {
+				// TODO: Once we bump the minimum Go version to 1.20, we can use
+				// multiple %w verbs for this wrapping. For now we need to use a
+				// compatibility shim for older Go versions.
+				//err = fmt.Errorf("%w (%w)", err, deadErr)
+				err = wrapBaseError(err, deadErr)
 			}
 			return nil, err
 		}
@@ -193,10 +220,7 @@ func MkdirAllHandle(root *os.File, unsafePath string, mode int) (_ *os.File, Err
 // If you plan to open the directory after you have created it or want to use
 // an open directory handle as the root, you should use [MkdirAllHandle] instead.
 // This function is a wrapper around [MkdirAllHandle].
-//
-// NOTE: The mode argument must be set the unix mode bits (unix.S_I...), not
-// the Go generic mode bits ([os.FileMode]...).
-func MkdirAll(root, unsafePath string, mode int) error {
+func MkdirAll(root, unsafePath string, mode os.FileMode) error {
 	rootDir, err := os.OpenFile(root, unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
 	if err != nil {
 		return err
@@ -12,12 +12,11 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"sync"

 	"golang.org/x/sys/unix"
 )

-var hasOpenat2 = sync.OnceValue(func() bool {
+var hasOpenat2 = sync_OnceValue(func() bool {
 	fd, err := unix.Openat2(unix.AT_FDCWD, ".", &unix.OpenHow{
 		Flags:   unix.O_PATH | unix.O_CLOEXEC,
 		Resolve: unix.RESOLVE_NO_SYMLINKS | unix.RESOLVE_IN_ROOT,
@@ -12,7 +12,6 @@ import (
 	"os"
 	"runtime"
 	"strconv"
-	"sync"

 	"golang.org/x/sys/unix"
 )
@@ -54,7 +53,7 @@ func verifyProcRoot(procRoot *os.File) error {
 	return nil
 }

-var hasNewMountApi = sync.OnceValue(func() bool {
+var hasNewMountApi = sync_OnceValue(func() bool {
 	// All of the pieces of the new mount API we use (fsopen, fsconfig,
 	// fsmount, open_tree) were added together in Linux 5.1[1,2], so we can
 	// just check for one of the syscalls and the others should also be
@@ -192,11 +191,11 @@ func doGetProcRoot() (*os.File, error) {
 	return procRoot, err
 }

-var getProcRoot = sync.OnceValues(func() (*os.File, error) {
+var getProcRoot = sync_OnceValues(func() (*os.File, error) {
 	return doGetProcRoot()
 })

-var hasProcThreadSelf = sync.OnceValue(func() bool {
+var hasProcThreadSelf = sync_OnceValue(func() bool {
 	return unix.Access("/proc/thread-self/", unix.F_OK) == nil
 })

@@ -265,12 +264,20 @@ func procThreadSelf(procRoot *os.File, subpath string) (_ *os.File, _ procThread
 			Resolve: unix.RESOLVE_BENEATH | unix.RESOLVE_NO_XDEV | unix.RESOLVE_NO_MAGICLINKS,
 		})
 		if err != nil {
-			return nil, nil, fmt.Errorf("%w: %w", errUnsafeProcfs, err)
+			// TODO: Once we bump the minimum Go version to 1.20, we can use
+			// multiple %w verbs for this wrapping. For now we need to use a
+			// compatibility shim for older Go versions.
+			//err = fmt.Errorf("%w: %w", errUnsafeProcfs, err)
+			return nil, nil, wrapBaseError(err, errUnsafeProcfs)
 		}
 	} else {
 		handle, err = openatFile(procRoot, threadSelf+subpath, unix.O_PATH|unix.O_NOFOLLOW|unix.O_CLOEXEC, 0)
 		if err != nil {
-			return nil, nil, fmt.Errorf("%w: %w", errUnsafeProcfs, err)
+			// TODO: Once we bump the minimum Go version to 1.20, we can use
+			// multiple %w verbs for this wrapping. For now we need to use a
+			// compatibility shim for older Go versions.
+			//err = fmt.Errorf("%w: %w", errUnsafeProcfs, err)
+			return nil, nil, wrapBaseError(err, errUnsafeProcfs)
 		}
 		defer func() {
 			if Err != nil {
@@ -289,12 +296,17 @@ func procThreadSelf(procRoot *os.File, subpath string) (_ *os.File, _ procThread
 	return handle, runtime.UnlockOSThread, nil
 }

-var hasStatxMountId = sync.OnceValue(func() bool {
+// STATX_MNT_ID_UNIQUE is provided in golang.org/x/sys@v0.20.0, but in order to
+// avoid bumping the requirement for a single constant we can just define it
+// ourselves.
+const STATX_MNT_ID_UNIQUE = 0x4000
+
+var hasStatxMountId = sync_OnceValue(func() bool {
 	var (
 		stx unix.Statx_t
 		// We don't care which mount ID we get. The kernel will give us the
 		// unique one if it is supported.
-		wantStxMask uint32 = unix.STATX_MNT_ID_UNIQUE | unix.STATX_MNT_ID
+		wantStxMask uint32 = STATX_MNT_ID_UNIQUE | unix.STATX_MNT_ID
 	)
 	err := unix.Statx(-int(unix.EBADF), "/", 0, int(wantStxMask), &stx)
 	return err == nil && stx.Mask&wantStxMask != 0
@@ -310,7 +322,7 @@ func getMountId(dir *os.File, path string) (uint64, error) {
 		stx unix.Statx_t
 		// We don't care which mount ID we get. The kernel will give us the
 		// unique one if it is supported.
-		wantStxMask uint32 = unix.STATX_MNT_ID_UNIQUE | unix.STATX_MNT_ID
+		wantStxMask uint32 = STATX_MNT_ID_UNIQUE | unix.STATX_MNT_ID
 	)

 	err := unix.Statx(int(dir.Fd()), path, unix.AT_EMPTY_PATH|unix.AT_SYMLINK_NOFOLLOW, int(wantStxMask), &stx)
@@ -25,8 +25,8 @@ github.com/coreos/go-systemd/v22/dbus
 # github.com/cpuguy83/go-md2man/v2 v2.0.2
 ## explicit; go 1.11
 github.com/cpuguy83/go-md2man/v2/md2man
-# github.com/cyphar/filepath-securejoin v0.3.5
-## explicit; go 1.21
+# github.com/cyphar/filepath-securejoin v0.4.1
+## explicit; go 1.18
 github.com/cyphar/filepath-securejoin
 # github.com/docker/go-units v0.5.0
 ## explicit
@@ -1 +1 @@
 .3.5
 .4.1