tetss: reverse: add TestHardlinkedLongname

Regression test for #802 .
Fails at the moment.

tests/reverse/correctness_test.go

@@ -4,8 +4,10 @@ import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
+	"log"
 	"os"
 	"path/filepath"
+	"strings"
 	"syscall"
 	"testing"
 
@@ -293,3 +295,61 @@ func TestSeekData(t *testing.T) {
 	}
 	f.Close()
 }
+
+func findInum(dir string, inum uint64) (name string) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		panic(err)
+	}
+	for _, e := range entries {
+		info, _ := e.Info()
+		st := info.Sys().(*syscall.Stat_t)
+		if st.Ino == inum {
+			return dir + "/" + e.Name()
+		}
+	}
+	log.Panicf("inum %d not found", inum)
+	return ""
+}
+
+// gocryptfs.longname.*.name of hardlinked files should not appear hardlinked (as the
+// contents are different).
+//
+// https://github.com/rfjakob/gocryptfs/issues/802
+func TestHardlinkedLongname(t *testing.T) {
+	if plaintextnames {
+		t.Skip()
+	}
+
+	workdir := dirA + "/" + t.Name()
+	if err := os.Mkdir(workdir, 0700); err != nil {
+		t.Fatal(err)
+	}
+	long1 := workdir + "/" + strings.Repeat("x", 200)
+	if err := ioutil.WriteFile(long1, []byte("hello"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	long2 := workdir + "/" + strings.Repeat("y", 220)
+	if err := syscall.Link(long1, long2); err != nil {
+		t.Fatal(err)
+	}
+
+	// Find workdir in encrypted view
+	var st syscall.Stat_t
+	if err := syscall.Stat(workdir, &st); err != nil {
+		t.Fatal(err)
+	}
+	cWorkdir := findInum(dirB, st.Ino)
+	t.Logf("workdir=%q cWorkdir=%q", workdir, cWorkdir)
+
+	matches, err := filepath.Glob(cWorkdir + "/gocryptfs.longname.*.name")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(matches) != 2 {
+		t.Fatalf("BUG: only %d matches, want 2", len(matches))
+	}
+	if test_helpers.Md5fn(matches[0]) == test_helpers.Md5fn(matches[1]) {
+		t.Errorf("Files %q are identical - that's wrong!", matches)
+	}
+}