more test coverage for der parsers

src/ecdsa/test_der.py

@@ -21,6 +21,9 @@
     remove_bitstring,
     remove_object,
     encode_oid,
+    remove_constructed,
+    remove_octet_string,
+    remove_sequence,
 )
 
 
@@ -71,6 +74,18 @@ def test_encoding_of_128(self):
         self.assertEqual(val, 128)
         self.assertFalse(rem)
 
+    def test_wrong_tag(self):
+        with self.assertRaises(UnexpectedDER) as e:
+            remove_integer(b"\x01\x02\x00\x80")
+
+        self.assertIn("wanted type 'integer'", str(e.exception))
+
+    def test_wrong_length(self):
+        with self.assertRaises(UnexpectedDER) as e:
+            remove_integer(b"\x02\x03\x00\x80")
+
+        self.assertIn("Length longer", str(e.exception))
+
 
 class TestReadLength(unittest.TestCase):
     # DER requires the lengths between 0 and 127 to be encoded using the short
@@ -368,6 +383,70 @@ def test_with_too_long_length(self):
             remove_object(b"\x06\x03\x88\x37")
 
 
+class TestRemoveConstructed(unittest.TestCase):
+    def test_simple(self):
+        data = b"\xa1\x02\xff\xaa"
+
+        tag, body, rest = remove_constructed(data)
+
+        self.assertEqual(tag, 0x01)
+        self.assertEqual(body, b"\xff\xaa")
+        self.assertEqual(rest, b"")
+
+    def test_with_malformed_tag(self):
+        data = b"\x01\x02\xff\xaa"
+
+        with self.assertRaises(UnexpectedDER) as e:
+            tag, body, rest = remove_constructed(data)
+
+        self.assertIn("constructed tag", str(e.exception))
+
+
+class TestRemoveOctetString(unittest.TestCase):
+    def test_simple(self):
+        data = b"\x04\x03\xaa\xbb\xcc"
+        body, rest = remove_octet_string(data)
+        self.assertEqual(body, b"\xaa\xbb\xcc")
+        self.assertEqual(rest, b"")
+
+    def test_with_malformed_tag(self):
+        data = b"\x03\x03\xaa\xbb\xcc"
+        with self.assertRaises(UnexpectedDER) as e:
+            body, rest = remove_octet_string(data)
+
+        self.assertIn("octetstring", str(e.exception))
+
+
+class TestRemoveSequence(unittest.TestCase):
+    def test_simple(self):
+        data = b"\x30\x02\xff\xaa"
+        body, rest = remove_sequence(data)
+        self.assertEqual(body, b"\xff\xaa")
+        self.assertEqual(rest, b"")
+
+    def test_with_empty_string(self):
+        with self.assertRaises(UnexpectedDER) as e:
+            remove_sequence(b"")
+
+        self.assertIn("Empty string", str(e.exception))
+
+    def test_with_wrong_tag(self):
+        data = b"\x20\x02\xff\xaa"
+
+        with self.assertRaises(UnexpectedDER) as e:
+            remove_sequence(data)
+
+        self.assertIn("wanted type 'sequence'", str(e.exception))
+
+    def test_with_wrong_length(self):
+        data = b"\x30\x03\xff\xaa"
+
+        with self.assertRaises(UnexpectedDER) as e:
+            remove_sequence(data)
+
+        self.assertIn("Length longer", str(e.exception))
+
+
 @st.composite
 def st_oid(draw, max_value=2 ** 512, max_size=50):
     """