reverse: reject too-long symlink target reads with ENAMETOOLONG

If the symlink target gets too long due to base64 encoding, we should
return ENAMETOOLONG instead of having the kernel reject the data and
returning an I/O error to the user.

Fixes https://github.com/rfjakob/gocryptfs/issues/167

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/reverse/correctness_test.go b/tests/reverse/correctness_test.go
index ee0a5b0..63043b7 100644
--- a/tests/reverse/correctness_test.go
+++ b/tests/reverse/correctness_test.go
@@ -147,3 +147,25 @@ func TestEnoent(t *testing.T) {
 		t.Errorf("want ENOENT, got: %v", err)
 	}
 }
+
+// If the symlink target gets too long due to base64 encoding, we should
+// return ENAMETOOLONG instead of having the kernel reject the data and
+// returning an I/O error to the user.
+// https://github.com/rfjakob/gocryptfs/issues/167
+func TestTooLongSymlink(t *testing.T) {
+	fn := dirA + "/TooLongSymlink"
+	target := string(bytes.Repeat([]byte("x"), 4000))
+	err := os.Symlink(target, fn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = os.Readlink(dirC + "/TooLongSymlink")
+	if err == nil {
+		return
+	}
+	err2 := err.(*os.PathError)
+	if err2.Err != syscall.ENAMETOOLONG {
+		t.Errorf("Expected %q error, got %q instead", syscall.ENAMETOOLONG,
+			err2.Err)
+	}
+}