Fix __hash__ crashing on unhashable dict attributes

tests/test_api.py

@@ -14,7 +14,7 @@
 from copy import copy, deepcopy
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
-from typing import ClassVar
+from typing import TYPE_CHECKING, ClassVar
 
 from securesystemslib import exceptions as sslib_exceptions
 from securesystemslib.signer import (
@@ -48,6 +48,9 @@
 from tuf.api.serialization import DeserializationError, SerializationError
 from tuf.api.serialization.json import JSONSerializer
 
+if TYPE_CHECKING:
+    from collections.abc import Callable
+
 logger = logging.getLogger(__name__)
 
 
@@ -1111,6 +1114,51 @@ def test_role_and_delegated_role_hash(self) -> None:
         role_set = {dr, dr2}
         self.assertEqual(len(role_set), 1)
 
+    def test_metadata_hash(self) -> None:
+        # Each of these __hash__ implementations passed a raw dict
+        # (unrecognized_fields, keys, roles, meta, targets, hashes,
+        # signatures) to hash(), which raises TypeError.
+        expires = datetime(2030, 1, 1, tzinfo=timezone.utc)
+        key = SSlibKey("kid1", "ed25519", "ed25519", {"public": "aa"})
+        delegated_role = DelegatedRole("r", ["kid1"], 1, False, ["*"], None)
+
+        factories: dict[str, Callable[[], object]] = {
+            "MetaFile": lambda: MetaFile(1, 10, {"sha256": "ab"}),
+            "TargetFile": lambda: TargetFile(10, {"sha256": "ab"}, "p"),
+            "Delegations": lambda: Delegations(
+                {"kid1": key}, {"r": delegated_role}
+            ),
+            "Root": lambda: Root(expires=expires),
+            "Timestamp": lambda: Timestamp(expires=expires),
+            "Snapshot": lambda: Snapshot(expires=expires),
+            "Targets": lambda: Targets(expires=expires),
+            "Metadata": lambda: Metadata(Snapshot(expires=expires)),
+        }
+
+        for name, factory in factories.items():
+            with self.subTest(name):
+                obj, equal_obj = factory(), factory()
+
+                self.assertIsInstance(hash(obj), int)
+
+                # equal objects must produce equal hashes (Python data model)
+                self.assertEqual(obj, equal_obj)
+                self.assertEqual(hash(obj), hash(equal_obj))
+
+                # the object must work as a set member / dict key
+                self.assertEqual(len({obj, equal_obj}), 1)
+
+    def test_metadata_hash_ignores_unrecognized_fields(self) -> None:
+        # unrecognized_fields holds arbitrary (possibly nested) JSON, so it is
+        # left out of __hash__. Objects differing only in unrecognized_fields
+        # are unequal but may share a hash, which the data model allows.
+        expires = datetime(2030, 1, 1, tzinfo=timezone.utc)
+        plain = Snapshot(expires=expires)
+        extra = Snapshot(expires=expires, unrecognized_fields={"a": ["b"]})
+
+        self.assertNotEqual(plain, extra)
+        self.assertIsInstance(hash(extra), int)
+
     def test_is_delegated_role_in_succinct_roles(self) -> None:
         succinct_roles = SuccinctRoles([], 1, 5, "bin")
         false_role_name_examples = [

tuf/api/_payload.py

@@ -188,7 +188,6 @@ def __hash__(self) -> int:
                 self.version,
                 self.spec_version,
                 self.expires,
-                self.unrecognized_fields,
             )
         )
 
@@ -565,10 +564,9 @@ def __hash__(self) -> int:
         return hash(
             (
                 super().__hash__(),
-                self.keys,
-                self.roles,
+                tuple(sorted(self.keys)),
+                tuple(sorted(self.roles)),
                 self.consistent_snapshot,
-                self.unrecognized_fields,
             )
         )
 
@@ -848,9 +846,7 @@ def __eq__(self, other: object) -> bool:
         )
 
     def __hash__(self) -> int:
-        return hash(
-            (self.version, self.length, self.hashes, self.unrecognized_fields)
-        )
+        return hash((self.version, self.length))
 
     @classmethod
     def from_dict(cls, meta_dict: dict[str, Any]) -> MetaFile:
@@ -1031,7 +1027,7 @@ def __eq__(self, other: object) -> bool:
         return super().__eq__(other) and self.meta == other.meta
 
     def __hash__(self) -> int:
-        return hash((super().__hash__(), self.meta))
+        return hash((super().__hash__(), len(self.meta)))
 
     @classmethod
     def from_dict(cls, signed_dict: dict[str, Any]) -> Snapshot:
@@ -1463,10 +1459,10 @@ def __eq__(self, other: object) -> bool:
     def __hash__(self) -> int:
         return hash(
             (
-                self.keys,
-                self.roles,
+                tuple(sorted(self.keys)),
+                # Order of the delegated roles matters (see __eq__)
+                tuple(self.roles) if self.roles is not None else None,
                 self.succinct_roles,
-                self.unrecognized_fields,
             )
         )
 
@@ -1592,9 +1588,7 @@ def __eq__(self, other: object) -> bool:
         )
 
     def __hash__(self) -> int:
-        return hash(
-            (self.length, self.hashes, self.path, self.unrecognized_fields)
-        )
+        return hash((self.length, self.path))
 
     @classmethod
     def from_dict(cls, target_dict: dict[str, Any], path: str) -> TargetFile:
@@ -1740,7 +1734,7 @@ def __eq__(self, other: object) -> bool:
         )
 
     def __hash__(self) -> int:
-        return hash((super().__hash__(), self.targets, self.delegations))
+        return hash((super().__hash__(), len(self.targets), self.delegations))
 
     @classmethod
     def from_dict(cls, signed_dict: dict[str, Any]) -> Targets:

tuf/api/metadata.py

@@ -148,7 +148,7 @@ def __eq__(self, other: object) -> bool:
         )
 
     def __hash__(self) -> int:
-        return hash((self.signatures, self.signed, self.unrecognized_fields))
+        return hash((tuple(self.signatures), self.signed))
 
     @property
     def signed_bytes(self) -> bytes: