Add comprehensive test coverage for attack vectors and CVE patterns

test/_helpers.py

@@ -0,0 +1,71 @@
+"""Shared test helpers for fickling test suite."""
+
+from __future__ import annotations
+
+import pickle
+from typing import Any
+
+from fickling.analysis import check_safety
+from fickling.fickle import Pickled
+
+
+def make_malicious_pickle(
+    module: str, func: str, args: tuple[Any, ...] = (), protocol: int = 4
+) -> bytes:
+    """Create a malicious pickle that calls module.func(*args).
+
+    Uses __reduce__ to serialize a payload that, when unpickled, would call
+    the specified function. Note: Python resolves the module at pickle time
+    via importlib, so dotted module paths like "os.path" resolve to their
+    actual implementation (e.g., posixpath on Unix).
+    """
+
+    class Payload:
+        def __reduce__(self) -> tuple[Any, tuple[Any, ...]]:
+            import importlib
+
+            mod = importlib.import_module(module)
+            fn = getattr(mod, func)
+            return (fn, args)
+
+    return pickle.dumps(Payload(), protocol=protocol)
+
+
+def make_benign_pickle(data: Any | None = None, protocol: int = 4) -> bytes:
+    """Create a benign pickle with safe data."""
+    if data is None:
+        data = [1, 2, 3]
+    return pickle.dumps(data, protocol=protocol)
+
+
+def make_pickle(obj: Any, protocol: int = 4) -> bytes:
+    """Create a pickle from a Python object."""
+    return pickle.dumps(obj, protocol=protocol)
+
+
+def assert_not_malicious(data: bytes) -> None:
+    """Assert that a pickle is not flagged as overtly malicious.
+
+    Standard library imports may be flagged as SUSPICIOUS (unused variable)
+    or LIKELY_UNSAFE (non-standard imports) but should NEVER be flagged as
+    OVERTLY_MALICIOUS unless they're actually dangerous.
+    """
+    from fickling.analysis import Severity
+
+    pickled = Pickled.load(data)
+    result = check_safety(pickled)
+    assert result.severity < Severity.LIKELY_OVERTLY_MALICIOUS, (
+        f"Safe object incorrectly flagged as malicious. "
+        f"Severity: {result.severity.name}. Results: {result.to_string()}"
+    )
+
+
+def assert_likely_safe(data: bytes) -> None:
+    """Assert that a pickle is LIKELY_SAFE (pure data, no imports)."""
+    from fickling.analysis import Severity
+
+    pickled = Pickled.load(data)
+    result = check_safety(pickled)
+    assert result.severity == Severity.LIKELY_SAFE, (
+        f"Expected LIKELY_SAFE, got {result.severity.name}. Results: {result.to_string()}"
+    )