Do not validate snappy xerial header version and compat fields (#2483)

Author: dpkp

Diff for: kafka/codec.py

@@ -193,8 +193,15 @@ def _detect_xerial_stream(payload):
     """
 
     if len(payload) > 16:
-        header = struct.unpack('!' + _XERIAL_V1_FORMAT, bytes(payload)[:16])
-        return header == _XERIAL_V1_HEADER
+        magic = struct.unpack('!' + _XERIAL_V1_FORMAT[:8], bytes(payload)[:8])
+        version, compat = struct.unpack('!' + _XERIAL_V1_FORMAT[8:], bytes(payload)[8:16])
+        # Until there is more than one way to do xerial blocking, the version + compat
+        # fields can be ignored. Also some producers (i.e., redpanda) are known to
+        # incorrectly encode these as little-endian, and that causes us to fail decoding
+        # when we otherwise would have succeeded.
+        # See https://github.com/dpkp/kafka-python/issues/2414
+        if magic == _XERIAL_V1_HEADER[:8]:
+            return True
     return False
 
 

Diff for: test/test_codec.py

@@ -39,12 +39,14 @@ def test_snappy_detect_xerial():
     _detect_xerial_stream = kafka1.codec._detect_xerial_stream
 
     header = b'\x82SNAPPY\x00\x00\x00\x00\x01\x00\x00\x00\x01Some extra bytes'
+    redpanda_header = b'\x82SNAPPY\x00\x01\x00\x00\x00\x01\x00\x00\x00Some extra bytes'
     false_header = b'\x01SNAPPY\x00\x00\x00\x01\x00\x00\x00\x01'
     default_snappy = snappy_encode(b'foobar' * 50)
     random_snappy = snappy_encode(b'SNAPPY' * 50, xerial_compatible=False)
     short_data = b'\x01\x02\x03\x04'
 
     assert _detect_xerial_stream(header) is True
+    assert _detect_xerial_stream(redpanda_header) is True
     assert _detect_xerial_stream(b'') is False
     assert _detect_xerial_stream(b'\x00') is False
     assert _detect_xerial_stream(false_header) is False