syscallcompat: Drop Openat emulation on macOS.

1 files changed, 20 insertions, 0 deletions

diff --git a/internal/syscallcompat/sys_common.go b/internal/syscallcompat/sys_common.go
index a1aa66d..a5b2c05 100644
--- a/internal/syscallcompat/sys_common.go
+++ b/internal/syscallcompat/sys_common.go
@@ -5,6 +5,8 @@ import (
 	"syscall"
 
 	"golang.org/x/sys/unix"
+
+	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
 // PATH_MAX is the maximum allowed path length on Linux.
@@ -42,6 +44,24 @@ func Faccessat(dirfd int, path string, mode uint32) error {
 	return unix.Faccessat(dirfd, path, mode, 0)
 }
 
+// Openat wraps the Openat syscall.
+func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
+	if flags&syscall.O_CREAT != 0 {
+		// O_CREAT should be used with O_EXCL. O_NOFOLLOW has no effect with O_EXCL.
+		if flags&syscall.O_EXCL == 0 {
+			tlog.Warn.Printf("Openat: O_CREAT without O_EXCL: flags = %#x", flags)
+			flags |= syscall.O_EXCL
+		}
+	} else {
+		// If O_CREAT is not used, we should use O_NOFOLLOW
+		if flags&syscall.O_NOFOLLOW == 0 {
+			tlog.Warn.Printf("Openat: O_NOFOLLOW missing: flags = %#x", flags)
+			flags |= syscall.O_NOFOLLOW
+		}
+	}
+	return unix.Openat(dirfd, path, flags, mode)
+}
+
 // Linkat exists both in Linux and in MacOS 10.10+.
 func Linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error) {
 	return unix.Linkat(olddirfd, oldpath, newdirfd, newpath, flags)