syscallcompat: add tests for emulated syscalls

Also fix the bug in emulateFchmodat that was found by the tests.

internal/syscallcompat/emulate.go

@@ -135,6 +135,16 @@ func emulateFchmodat(dirfd int, path string, mode uint32, flags int) (err error)
 		return err
 	}
 	defer syscall.Fchdir(cwd)
+	// We also don't have Lchmod, so emulate it (poorly).
+	if flags&unix.AT_SYMLINK_NOFOLLOW > 0 {
+		fi, err := os.Lstat(path)
+		if err != nil {
+			return err
+		}
+		if fi.Mode()&os.ModeSymlink > 0 {
+			return nil
+		}
+	}
 	return syscall.Chmod(path, mode)
 }
 

internal/syscallcompat/emulate_test.go

@@ -0,0 +1,223 @@
+package syscallcompat
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"syscall"
+	"testing"
+
+	"golang.org/x/sys/unix"
+)
+
+var tmpDir string
+var tmpDirFd int
+
+func TestMain(m *testing.M) {
+	origWd, err := os.Getwd()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	parent := "/tmp/gocryptfs-test-parent"
+	err = os.MkdirAll(parent, 0700)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	tmpDir, err = ioutil.TempDir(parent, "syscallcompat")
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	dirf, err := os.Open(tmpDir)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	defer dirf.Close()
+	tmpDirFd = int(dirf.Fd())
+	// Run the tests
+	r := m.Run()
+	// Check that we are in the same directory again (the emulated syscalls
+	// use Fchdir a lot)
+	cwd, _ := os.Getwd()
+	if cwd != origWd {
+		fmt.Printf("working dir has changed from %q to %q", origWd, cwd)
+		os.Exit(1)
+	}
+	os.Exit(r)
+}
+
+func TestEmulateOpenat(t *testing.T) {
+	_, err := emulateOpenat(tmpDirFd, "testOpenAt", 0, 0)
+	if err == nil {
+		t.Errorf("should have failed")
+	}
+	fd, err := os.Create(tmpDir + "/testOpenAt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+	rawFd, err := emulateOpenat(tmpDirFd, "testOpenAt", 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer syscall.Close(rawFd)
+	if rawFd < 0 {
+		t.Fatalf("rawFd=%d", rawFd)
+	}
+}
+
+func TestEmulateRenameat(t *testing.T) {
+	os.Mkdir(tmpDir+"/dir1", 0700)
+	dir1, err := os.Open(tmpDir + "/dir1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dir1.Close()
+	os.Mkdir(tmpDir+"/dir2", 0700)
+	dir2, err := os.Open(tmpDir + "/dir2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dir2.Close()
+	fd, err := os.Create(tmpDir + "/dir1/f1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+	err = emulateRenameat(int(dir1.Fd()), "f1", int(dir2.Fd()), "f2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = os.Stat(tmpDir + "/dir2/f2")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestEmulateUnlinkat(t *testing.T) {
+	os.Mkdir(tmpDir+"/unlink1", 0700)
+	dirfd, err := os.Open(tmpDir + "/unlink1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dirfd.Close()
+	// Try to delete file
+	fd, err := os.Create(tmpDir + "/unlink1/f1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+	err = emulateUnlinkat(int(dirfd.Fd()), "f1", 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = os.Stat(tmpDir + "/unlink1/f1")
+	if err == nil {
+		t.Fatalf("file not deleted!")
+	}
+	// Try to delete dir
+	err = os.Mkdir(tmpDir+"/unlink1/d1", 0700)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = emulateUnlinkat(int(dirfd.Fd()), "d1", 0)
+	if err == nil {
+		t.Fatalf("this should fail due to missing AT_REMOVEDIR flag")
+	}
+	err = emulateUnlinkat(int(dirfd.Fd()), "d1", unix.AT_REMOVEDIR)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = os.Stat(tmpDir + "/unlink1/d1")
+	if err == nil {
+		t.Fatalf("dir not deleted!")
+	}
+}
+
+func TestEmulateMknodat(t *testing.T) {
+	err := emulateMknodat(tmpDirFd, "fifo1", unix.S_IFIFO, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = os.Stat(tmpDir + "/fifo1")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestEmulateFchmodat(t *testing.T) {
+	fd, err := os.Create(tmpDir + "/chmod")
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = fd.Chmod(0654)
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+	// Chmod a normal file
+	err = emulateFchmodat(tmpDirFd, "chmod", 0600, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var st syscall.Stat_t
+	err = syscall.Lstat(tmpDir+"/chmod", &st)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if st.Mode != 0100600 {
+		t.Fatalf("Wrong mode: have %o, want %o", st.Mode, 0100600)
+	}
+	// Chmod a symlink (original file should not change)
+	err = os.Symlink(tmpDir+"/chmod", tmpDir+"/chmodSymlink")
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = emulateFchmodat(tmpDirFd, "chmodSymlink", 0123, unix.AT_SYMLINK_NOFOLLOW)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = syscall.Lstat(tmpDir+"/chmod", &st)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if st.Mode != 0100600 {
+		t.Fatalf("Wrong mode: have %o, want %o", st.Mode, 0100600)
+	}
+}
+
+func TestEmulateFchownat(t *testing.T) {
+	t.Skipf("TODO")
+}
+
+func TestEmulateSymlinkat(t *testing.T) {
+	err := emulateSymlinkat("/foo/bar/baz", tmpDirFd, "symlink1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var st syscall.Stat_t
+	err = syscall.Lstat(tmpDir+"/symlink1", &st)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if st.Mode != 0120777 {
+		t.Fatalf("Wrong mode, have %o, want 0120777", st.Mode)
+	}
+}
+
+func TestEmulateMkdirat(t *testing.T) {
+	err := emulateMkdirat(tmpDirFd, "mkdirat", 0100)
+	if err != nil {
+		t.Fatal(err)
+	}
+	fi, err := os.Stat(tmpDir + "/mkdirat")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !fi.IsDir() {
+		t.Fatalf("mkdirat did not create a directory")
+	}
+}