Check size of metadata

Author: cffls

pycardano/metadata.py

@@ -7,7 +7,7 @@
 from nacl.encoding import RawEncoder
 from nacl.hash import blake2b
 
-from pycardano.exception import DeserializeException
+from pycardano.exception import DeserializeException, InvalidArgumentException
 from pycardano.hash import AuxiliaryDataHash, AUXILIARY_DATA_HASH_SIZE
 from pycardano.nativescript import NativeScript
 from pycardano.serialization import (CBORSerializable, DictCBORSerializable, ArrayCBORSerializable,
@@ -18,6 +18,38 @@ class Metadata(DictCBORSerializable):
     KEY_TYPE = int  # transaction_metadatum_label, see https://github.com/cardano-foundation/CIPs/tree/master/CIP-0010
     VALUE_TYPE = Any
 
+    MAX_ITEM_SIZE = 64
+    INTERNAL_TYPES = (dict, list, int, bytes, str)
+
+    def _validate(self):
+
+        def _validate_type_and_size(data):
+            if not isinstance(data, self.INTERNAL_TYPES):
+                raise InvalidArgumentException(f"A value in Metadata has to be one of {self.INTERNAL_TYPES}, "
+                                               f"got {type(data)} instead.")
+            if isinstance(data, bytes):
+                if len(data) > self.MAX_ITEM_SIZE:
+                    raise InvalidArgumentException(f"The size of {data} exceeds {self.MAX_ITEM_SIZE} bytes.")
+            elif isinstance(data, str):
+                if len(data.encode("utf-8")) > self.MAX_ITEM_SIZE:
+                    raise InvalidArgumentException(f"The size of {data} exceeds {self.MAX_ITEM_SIZE} bytes.")
+            elif isinstance(data, list):
+                for item in data:
+                    _validate_type_and_size(item)
+            elif isinstance(data, dict):
+                for key in data:
+                    _validate_type_and_size(data[key])
+
+        for k in self:
+            if not isinstance(k, self.KEY_TYPE):
+                raise InvalidArgumentException(f"Keys in the first layer of Metadata has to be {self.KEY_TYPE}, "
+                                               f"got {type(k)} instead.")
+            _validate_type_and_size(self[k])
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._validate()
+
 
 @dataclass
 class ShellayMarryMetadata(ArrayCBORSerializable):

test/pycardano/test_metadata.py

@@ -1,5 +1,7 @@
+import pytest
 from cbor2 import CBORTag
 
+from pycardano.exception import InvalidArgumentException
 from pycardano.key import VerificationKey
 from pycardano.metadata import Metadata, ShellayMarryMetadata, AlonzoMetadata, AuxiliaryData
 from pycardano.nativescript import ScriptPubkey, ScriptAll, InvalidBefore, InvalidHereAfter
@@ -92,3 +94,49 @@ def test_axuiliary_data_hash():
 
     aux_data = AuxiliaryData(AlonzoMetadata(metadata=Metadata(data)))
     assert "592a2df0e091566969b3044626faa8023dabe6f39c78f33bed9e105e55159221" == str(aux_data.hash())
+
+
+def test_metadata_invalid_type():
+    data = {
+        "abc": "abc"
+    }
+    with pytest.raises(InvalidArgumentException):
+        Metadata(data)
+
+    data = {
+        123: {
+            "1": set()
+        }
+    }
+    with pytest.raises(InvalidArgumentException):
+        Metadata(data)
+
+
+def test_metadata_valid_size():
+    data = {
+        123: {
+            "1": bytes(Metadata.MAX_ITEM_SIZE),
+            "2": "1" * Metadata.MAX_ITEM_SIZE
+        }
+    }
+    Metadata(data)
+
+
+def test_metadata_invalid_size():
+    data = {
+        123: {
+            "1": bytes(Metadata.MAX_ITEM_SIZE + 1)
+        }
+    }
+
+    with pytest.raises(InvalidArgumentException):
+        Metadata(data)
+
+    data = {
+        123: {
+            "1": "1" * (Metadata.MAX_ITEM_SIZE + 1)
+        }
+    }
+
+    with pytest.raises(InvalidArgumentException):
+        Metadata(data)