feat: Implement Lchown function for changing file ownership (#5161)

* feat: Implement Lchown function for changing file ownership

- Added Lchown function to change the numeric uid and gid of a file or symbolic link.
- Included error handling to return *PathError for failed operations.
- Added unit tests for Lchown to verify behavior on different error scenarios.

* fix: fix chmod tests

src/os/file_anyos.go

@@ -166,6 +166,19 @@ func Chown(name string, uid, gid int) error {
 	return nil
 }
 
+// Lchown changes the numeric uid and gid of the named file.
+// If the file is a symbolic link, it changes the uid and gid of the link itself.
+// If there is an error, it will be of type [*PathError].
+//
+// If there is an error, it will be of type *PathError.
+func Lchown(name string, uid, gid int) error {
+	e := ignoringEINTR(func() error { return syscall.Lchown(name, uid, gid) })
+	if e != nil {
+		return &PathError{Op: "lchown", Path: name, Err: e}
+	}
+	return nil
+}
+
 // ignoringEINTR makes a function call and repeats it if it returns an
 // EINTR error. This appears to be required even though we install all
 // signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.

src/os/os_chmod_test.go

@@ -12,6 +12,7 @@ import (
 	"errors"
 	"io/fs"
 	. "os"
+	"path/filepath"
 	"runtime"
 	"testing"
 )
@@ -70,3 +71,38 @@ func TestChownErr(t *testing.T) {
 		}
 	}
 }
+
+func TestLchownErr(t *testing.T) {
+	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
+		t.Log("skipping on " + runtime.GOOS)
+		return
+	}
+
+	var (
+		TEST_UID_ROOT = 0
+		TEST_GID_ROOT = 0
+	)
+
+	f := newFile("TestLchown", t)
+	defer Remove(f.Name())
+	defer f.Close()
+	link := filepath.Join(TempDir(), "TestLchownLink")
+	_ = Symlink(f.Name(), link)
+	defer Remove(link)
+
+	// EACCES
+	if err := Lchown(link, TEST_UID_ROOT, TEST_GID_ROOT); err != nil {
+		errCmp := fs.PathError{Op: "lchown", Path: link, Err: errors.New("operation not permitted")}
+		if errors.Is(err, &errCmp) {
+			t.Fatalf("lchown(%s, uid=%v, gid=%v): got '%v', want 'operation not permitted'", link, TEST_UID_ROOT, TEST_GID_ROOT, err)
+		}
+	}
+
+	// ENOENT
+	if err := Chown("invalid", Geteuid(), Getgid()); err != nil {
+		errCmp := fs.PathError{Op: "lchown", Path: "invalid", Err: errors.New("no such file or directory")}
+		if errors.Is(err, &errCmp) {
+			t.Fatalf("chown(%s, uid=%v, gid=%v): got '%v', want 'no such file or directory'", link, Geteuid(), Getegid(), err)
+		}
+	}
+}

src/syscall/syscall_libc.go

@@ -172,6 +172,15 @@ func Chown(path string, uid, gid int) (err error) {
 	return
 }
 
+func Lchown(path string, uid, gid int) (err error) {
+	data := cstring(path)
+	fail := int(libc_lchown(&data[0], uid, gid))
+	if fail < 0 {
+		err = getErrno()
+	}
+	return
+}
+
 func Fork() (err error) {
 	fail := int(libc_fork())
 	if fail < 0 {
@@ -368,6 +377,11 @@ func libc_chmod(pathname *byte, mode uint32) int32
 //export chown
 func libc_chown(pathname *byte, owner, group int) int32
 
+// int lchown(const char *pathname, uid_t owner, gid_t group);
+//
+//export lchown
+func libc_lchown(pathname *byte, owner, group int) int32
+
 // int mkdir(const char *pathname, mode_t mode);
 //
 //export mkdir