pkg/archive: Use archive_unix.go on FreeBSD

Almost all the code can be shared between Linux, FreeBSD and Darwin with
the only different in the handling of lchmod. On FreeBSD and Darwin (and
probably other BSDs) we can access lchmod functionality via
unix.Fchmodat.

Signed-off-by: Doug Rabson <dfr@rabson.org>

pkg/archive/archive_bsd.go

@@ -0,0 +1,19 @@
+//go:build freebsd || darwin
+// +build freebsd darwin
+
+package archive
+
+import (
+	"archive/tar"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func handleLChmod(hdr *tar.Header, path string, hdrInfo os.FileInfo, forceMask *os.FileMode) error {
+	permissionsMask := hdrInfo.Mode()
+	if forceMask != nil {
+		permissionsMask = *forceMask
+	}
+	return unix.Fchmodat(unix.AT_FDCWD, path, uint32(permissionsMask), unix.AT_SYMLINK_NOFOLLOW)
+}

pkg/archive/archive_linux.go

@@ -189,3 +189,22 @@ func GetFileOwner(path string) (uint32, uint32, uint32, error) {
 	}
 	return 0, 0, uint32(f.Mode()), nil
 }
+
+func handleLChmod(hdr *tar.Header, path string, hdrInfo os.FileInfo, forceMask *os.FileMode) error {
+	permissionsMask := hdrInfo.Mode()
+	if forceMask != nil {
+		permissionsMask = *forceMask
+	}
+	if hdr.Typeflag == tar.TypeLink {
+		if fi, err := os.Lstat(hdr.Linkname); err == nil && (fi.Mode()&os.ModeSymlink == 0) {
+			if err := os.Chmod(path, permissionsMask); err != nil {
+				return err
+			}
+		}
+	} else if hdr.Typeflag != tar.TypeSymlink {
+		if err := os.Chmod(path, permissionsMask); err != nil {
+			return err
+		}
+	}
+	return nil
+}

pkg/archive/archive_unix.go

@@ -1,5 +1,5 @@
-//go:build !windows && !freebsd
-// +build !windows,!freebsd
+//go:build !windows
+// +build !windows
 
 package archive
 
@@ -101,25 +101,6 @@ func handleTarTypeBlockCharFifo(hdr *tar.Header, path string) error {
 	return system.Mknod(path, mode, system.Mkdev(hdr.Devmajor, hdr.Devminor))
 }
 
-func handleLChmod(hdr *tar.Header, path string, hdrInfo os.FileInfo, forceMask *os.FileMode) error {
-	permissionsMask := hdrInfo.Mode()
-	if forceMask != nil {
-		permissionsMask = *forceMask
-	}
-	if hdr.Typeflag == tar.TypeLink {
-		if fi, err := os.Lstat(hdr.Linkname); err == nil && (fi.Mode()&os.ModeSymlink == 0) {
-			if err := os.Chmod(path, permissionsMask); err != nil {
-				return err
-			}
-		}
-	} else if hdr.Typeflag != tar.TypeSymlink {
-		if err := os.Chmod(path, permissionsMask); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
 // Hardlink without symlinks
 func handleLLink(targetPath, path string) error {
 	// Note: on Linux, the link syscall will not follow symlinks.