From 3b2dbeb75816c2926c04b8e37b133335b419c138 Mon Sep 17 00:00:00 2001
From: Kio Smallwood <kio.smallwood@flexitricity.com>
Date: Thu, 22 Jul 2021 16:28:00 +0100
Subject: [PATCH] Roll in a fix for #118 while we're at it

---
 cbor2/decoder.py      |  6 +++++-
 source/decoder.c      |  4 +++-
 tests/test_decoder.py | 10 ++++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/cbor2/decoder.py b/cbor2/decoder.py
index 876e4cfc..82e95b2c 100644
--- a/cbor2/decoder.py
+++ b/cbor2/decoder.py
@@ -369,7 +369,11 @@ def decode_special(self, subtype):
             return CBORSimpleValue(subtype)
 
         # Major tag 7
-        return special_decoders[subtype](self)
+        try:
+            return special_decoders[subtype](self)
+        except KeyError as e:
+            raise CBORDecodeValueError(
+                    "Undefined Reserved major type 7 subtype 0x%x" % subtype) from e
 
     #
     # Semantic decoders (major tag 6)
diff --git a/source/decoder.c b/source/decoder.c
index 7f0af3c2..4a0c4423 100644
--- a/source/decoder.c
+++ b/source/decoder.c
@@ -1606,7 +1606,9 @@ decode_special(CBORDecoderObject *self, uint8_t subtype)
             case 27: return CBORDecoder_decode_float64(self);
             case 31: CBOR2_RETURN_BREAK;
             default:
-                // XXX Raise exception?
+                PyErr_Format(
+                    _CBOR2_CBORDecodeValueError,
+                    "Undefined Reserved major type 7 subtype 0x%x", subtype);
                 break;
         }
     }
diff --git a/tests/test_decoder.py b/tests/test_decoder.py
index ce8ce049..3ec0f308 100644
--- a/tests/test_decoder.py
+++ b/tests/test_decoder.py
@@ -697,3 +697,13 @@ def test_invalid_cbor(impl):
             '4c271579b01633a3ef6271be5c225eb2'
             )
         )
+
+
+@pytest.mark.parametrize('data, expected', [
+    ('fc', '1c'), ('fd', '1d'), ('fe', '1e')
+    ],
+)
+def test_reserved_special_tags(impl, data, expected):
+    with pytest.raises(impl.CBORDecodeValueError) as exc_info:
+        impl.loads(unhexlify(data))
+    assert exc_info.value.args[0] == "Undefined Reserved major type 7 subtype 0x" + expected