syscallcompat: OSX: add Unlinkat wrapper

Also, replace remaining naked syscall.Openat calls.

internal/fusefrontend/fs.go

@@ -133,7 +133,7 @@ func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Conte
 
 		// Create content
 		var fdRaw int
-		fdRaw, err = syscall.Openat(int(dirfd.Fd()), cName, iflags|os.O_CREATE, mode)
+		fdRaw, err = syscallcompat.Openat(int(dirfd.Fd()), cName, iflags|os.O_CREATE, mode)
 		if err != nil {
 			nametransform.DeleteLongName(dirfd, cName)
 			return nil, fuse.ToStatus(err)
@@ -295,7 +295,7 @@ func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
 		}
 		defer dirfd.Close()
 		// Delete content
-		err = syscall.Unlinkat(int(dirfd.Fd()), cName)
+		err = syscallcompat.Unlinkat(int(dirfd.Fd()), cName)
 		if err != nil {
 			return fuse.ToStatus(err)
 		}

internal/fusefrontend/fs_dir.go

@@ -114,7 +114,7 @@ func (fs *FS) Rmdir(path string, context *fuse.Context) (code fuse.Status) {
 	defer parentDirFd.Close()
 
 	cName := filepath.Base(cPath)
-	dirfdRaw, err := syscall.Openat(int(parentDirFd.Fd()), cName,
+	dirfdRaw, err := syscallcompat.Openat(int(parentDirFd.Fd()), cName,
 		syscall.O_RDONLY, 0)
 	if err == syscall.EACCES {
 		// We need permission to read and modify the directory
@@ -136,7 +136,7 @@ func (fs *FS) Rmdir(path string, context *fuse.Context) (code fuse.Status) {
 		// Retry open
 		var st syscall.Stat_t
 		syscall.Lstat(cPath, &st)
-		dirfdRaw, err = syscall.Openat(int(parentDirFd.Fd()), cName,
+		dirfdRaw, err = syscallcompat.Openat(int(parentDirFd.Fd()), cName,
 			syscall.O_RDONLY, 0)
 		// Undo the chmod if removing the directory failed
 		defer func() {
@@ -191,7 +191,7 @@ func (fs *FS) Rmdir(path string, context *fuse.Context) (code fuse.Status) {
 			return fuse.ToStatus(err)
 		}
 		// Delete "gocryptfs.diriv.rmdir.XYZ"
-		err = syscall.Unlinkat(int(parentDirFd.Fd()), tmpName)
+		err = syscallcompat.Unlinkat(int(parentDirFd.Fd()), tmpName)
 		if err != nil {
 			tlog.Warn.Printf("Rmdir: Could not clean up %s: %v", tmpName, err)
 		}

internal/nametransform/diriv.go

@@ -9,6 +9,7 @@ import (
 	"syscall"
 
 	"github.com/rfjakob/gocryptfs/internal/cryptocore"
+	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
@@ -35,7 +36,7 @@ func ReadDirIV(dir string) (iv []byte, err error) {
 // ReadDirIVAt reads "gocryptfs.diriv" from the directory that is opened as "dirfd".
 // Using the dirfd makes it immune to concurrent renames of the directory.
 func ReadDirIVAt(dirfd *os.File) (iv []byte, err error) {
-	fdRaw, err := syscall.Openat(int(dirfd.Fd()), DirIVFilename, syscall.O_RDONLY, 0)
+	fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), DirIVFilename, syscall.O_RDONLY, 0)
 	if err != nil {
 		tlog.Warn.Printf("ReadDirIVAt: opening %q in dir %q failed: %v",
 			DirIVFilename, dirfd.Name(), err)

internal/nametransform/longnames.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 	"syscall"
 
+	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
@@ -65,7 +66,7 @@ func ReadLongName(path string) (string, error) {
 
 // DeleteLongName deletes "hashName.name".
 func DeleteLongName(dirfd *os.File, hashName string) error {
-	err := syscall.Unlinkat(int(dirfd.Fd()), hashName+LongNameSuffix)
+	err := syscallcompat.Unlinkat(int(dirfd.Fd()), hashName+LongNameSuffix)
 	if err != nil {
 		tlog.Warn.Printf("DeleteLongName: %v", err)
 	}
@@ -86,7 +87,7 @@ func (n *NameTransform) WriteLongName(dirfd *os.File, hashName string, plainName
 	cName := n.EncryptName(plainName, dirIV)
 
 	// Write the encrypted name into hashName.name
-	fdRaw, err := syscall.Openat(int(dirfd.Fd()), hashName+LongNameSuffix,
+	fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), hashName+LongNameSuffix,
 		syscall.O_WRONLY|syscall.O_CREAT|syscall.O_EXCL, 0600)
 	if err != nil {
 		tlog.Warn.Printf("WriteLongName: Openat: %v", err)

internal/syscallcompat/sys_darwin.go

@@ -69,6 +69,24 @@ func Renameat(olddirfd int, oldpath string, newdirfd int, newpath string) (err e
 	return syscall.Rename(oldpath, newpath)
 }
 
+// Poor man's Unlinkat
+func Unlinkat(dirfd int, path string) (err error) {
+	chdirMutex.Lock()
+	defer chdirMutex.Unlock()
+	if !filepath.IsAbs(path) {
+		oldWd, err := os.Getwd()
+		if err != nil {
+			return err
+		}
+		defer os.Chdir(oldWd)
+	}
+	path, err = dirfdAbs(dirfd, path)
+	if err != nil {
+		return err
+	}
+	return syscall.Unlink(path)
+}
+
 // dirfdAbs transforms the dirfd-relative "path" to an absolute one. If the
 // path is not already absolute, this function will change the working
 // directory. The caller has to chdir back.

internal/syscallcompat/sys_linux.go

@@ -48,3 +48,7 @@ func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
 func Renameat(olddirfd int, oldpath string, newdirfd int, newpath string) (err error) {
 	return syscall.Renameat(olddirfd, oldpath, newdirfd, newpath)
 }
+
+func Unlinkat(dirfd int, path string) error {
+	return syscall.Unlinkat(dirfd, path)
+}