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| 1 | +# test_delete_descriptor_binding.py |
| 2 | +# |
| 3 | +# Copyright (C) 2026 wolfSSL Inc. |
| 4 | +# |
| 5 | +# This file is part of wolfSSL. (formerly known as CyaSSL) |
| 6 | +# |
| 7 | +# wolfSSL is free software; you can redistribute it and/or modify |
| 8 | +# it under the terms of the GNU General Public License as published by |
| 9 | +# the Free Software Foundation; either version 2 of the License, or |
| 10 | +# (at your option) any later version. |
| 11 | +# |
| 12 | +# wolfSSL is distributed in the hope that it will be useful, |
| 13 | +# but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | +# GNU General Public License for more details. |
| 16 | +# |
| 17 | +# You should have received a copy of the GNU General Public License |
| 18 | +# along with this program; if not, write to the Free Software |
| 19 | +# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA |
| 20 | + |
| 21 | +""" |
| 22 | +Regression tests guarding against the Python descriptor-binding bug on |
| 23 | +``_delete`` / ``_copy`` class attributes. |
| 24 | +
|
| 25 | +Historically these were written as bare references to ``_lib`` functions:: |
| 26 | +
|
| 27 | + class Random: |
| 28 | + _delete = _lib.wc_FreeRng |
| 29 | +
|
| 30 | + def __del__(self): |
| 31 | + self._delete(self.native_object) |
| 32 | +
|
| 33 | +If the underlying callable is ever a plain Python function (e.g. a mock, |
| 34 | +wrapper, or future CFFI change), the descriptor protocol turns |
| 35 | +``self._delete`` into a *bound method*, and ``self._delete(native)`` then |
| 36 | +calls ``fn(self, native)`` - passing ``self`` as an extra C argument. |
| 37 | +
|
| 38 | +The fix wraps the callable in ``staticmethod(...)`` at the class level so |
| 39 | +that attribute lookup never binds ``self``. These tests assert the fix |
| 40 | +stays in place and document the Python semantics it relies on. |
| 41 | +""" |
| 42 | + |
| 43 | +# pylint: disable=redefined-outer-name |
| 44 | + |
| 45 | +import inspect |
| 46 | + |
| 47 | +import pytest |
| 48 | + |
| 49 | +from wolfcrypt._ffi import lib as _lib |
| 50 | + |
| 51 | + |
| 52 | +def _static_attrs(): |
| 53 | + """Yield (cls, attr_name) pairs that must be staticmethod-wrapped.""" |
| 54 | + from wolfcrypt.random import Random |
| 55 | + yield Random, "_delete" |
| 56 | + |
| 57 | + if _lib.SHA_ENABLED: |
| 58 | + from wolfcrypt.hashes import Sha |
| 59 | + yield Sha, "_delete" |
| 60 | + yield Sha, "_copy" |
| 61 | + if _lib.SHA256_ENABLED: |
| 62 | + from wolfcrypt.hashes import Sha256 |
| 63 | + yield Sha256, "_delete" |
| 64 | + yield Sha256, "_copy" |
| 65 | + if _lib.SHA384_ENABLED: |
| 66 | + from wolfcrypt.hashes import Sha384 |
| 67 | + yield Sha384, "_delete" |
| 68 | + yield Sha384, "_copy" |
| 69 | + if _lib.SHA512_ENABLED: |
| 70 | + from wolfcrypt.hashes import Sha512 |
| 71 | + yield Sha512, "_delete" |
| 72 | + yield Sha512, "_copy" |
| 73 | + if _lib.HMAC_ENABLED: |
| 74 | + from wolfcrypt.hashes import _Hmac |
| 75 | + yield _Hmac, "_delete" |
| 76 | + |
| 77 | + if _lib.AESGCM_STREAM_ENABLED: |
| 78 | + from wolfcrypt.ciphers import AesGcmStream |
| 79 | + yield AesGcmStream, "_delete" |
| 80 | + if _lib.RSA_ENABLED: |
| 81 | + from wolfcrypt.ciphers import _Rsa |
| 82 | + yield _Rsa, "_delete" |
| 83 | + if _lib.ECC_ENABLED: |
| 84 | + from wolfcrypt.ciphers import _Ecc |
| 85 | + yield _Ecc, "_delete" |
| 86 | + if _lib.ED25519_ENABLED: |
| 87 | + from wolfcrypt.ciphers import _Ed25519 |
| 88 | + yield _Ed25519, "_delete" |
| 89 | + if _lib.ED448_ENABLED: |
| 90 | + from wolfcrypt.ciphers import _Ed448 |
| 91 | + yield _Ed448, "_delete" |
| 92 | + |
| 93 | + |
| 94 | +@pytest.mark.parametrize( |
| 95 | + "cls,attr", |
| 96 | + list(_static_attrs()), |
| 97 | + ids=lambda v: v if isinstance(v, str) else v.__name__, |
| 98 | +) |
| 99 | +def test_lib_fn_class_attr_is_staticmethod(cls, attr): |
| 100 | + """The class attribute must be a ``staticmethod`` so that attribute |
| 101 | + access via an instance never triggers descriptor binding. |
| 102 | +
|
| 103 | + ``inspect.getattr_static`` walks the MRO without invoking descriptors, |
| 104 | + so it returns the raw object (the ``staticmethod`` wrapper itself). |
| 105 | + """ |
| 106 | + raw = inspect.getattr_static(cls, attr) |
| 107 | + assert isinstance(raw, staticmethod), ( |
| 108 | + "%s.%s must be wrapped in staticmethod(...) to prevent Python's " |
| 109 | + "descriptor protocol from injecting `self` as an extra positional " |
| 110 | + "argument when the underlying callable is a plain Python function " |
| 111 | + "(e.g. a test mock). Got %r." % (cls.__name__, attr, type(raw)) |
| 112 | + ) |
| 113 | + |
| 114 | + |
| 115 | +def test_descriptor_binding_semantics_documentation(): |
| 116 | + """Document the exact Python behavior the fix relies on. |
| 117 | +
|
| 118 | + Without ``staticmethod``, a Python-function class attribute becomes a |
| 119 | + bound method and leaks ``self`` into the call. ``staticmethod`` makes |
| 120 | + the descriptor return the underlying callable unchanged. |
| 121 | + """ |
| 122 | + received = [] |
| 123 | + |
| 124 | + def recorder(*args, **kwargs): |
| 125 | + received.append((args, kwargs)) |
| 126 | + |
| 127 | + class Buggy: |
| 128 | + _delete = recorder |
| 129 | + |
| 130 | + def run(self): |
| 131 | + self._delete("native") |
| 132 | + |
| 133 | + class Fixed: |
| 134 | + _delete = staticmethod(recorder) |
| 135 | + |
| 136 | + def run(self): |
| 137 | + self._delete("native") |
| 138 | + |
| 139 | + Buggy().run() |
| 140 | + buggy_args, _ = received[-1] |
| 141 | + assert len(buggy_args) == 2 and buggy_args[1] == "native", ( |
| 142 | + "Sanity check failed: plain class-attribute Python function " |
| 143 | + "should have been bound and passed self as the first arg." |
| 144 | + ) |
| 145 | + |
| 146 | + Fixed().run() |
| 147 | + fixed_args, _ = received[-1] |
| 148 | + assert fixed_args == ("native",), ( |
| 149 | + "staticmethod-wrapping should prevent self from being bound, " |
| 150 | + "so the callable receives only the intended positional argument." |
| 151 | + ) |
| 152 | + |
| 153 | + |
| 154 | +def test_random_delete_receives_only_native_object(): |
| 155 | + """End-to-end behavioral check on the real ``Random`` class. |
| 156 | +
|
| 157 | + We substitute a plain Python recorder in place of the CFFI free |
| 158 | + function (wrapped in staticmethod, mirroring how the class itself |
| 159 | + stores it) and trigger the code path that calls ``self._delete``. |
| 160 | + The recorder must see exactly one positional argument - the |
| 161 | + ``native_object`` - and never ``self``. |
| 162 | + """ |
| 163 | + from wolfcrypt.random import Random |
| 164 | + |
| 165 | + received = [] |
| 166 | + |
| 167 | + def recorder(*args, **kwargs): |
| 168 | + received.append((args, kwargs)) |
| 169 | + |
| 170 | + original = inspect.getattr_static(Random, "_delete") |
| 171 | + try: |
| 172 | + Random._delete = staticmethod(recorder) |
| 173 | + r = Random() |
| 174 | + native = r.native_object |
| 175 | + r.__del__() |
| 176 | + r.native_object = None # prevent real cleanup on the way out |
| 177 | + assert received, "recorder was never called" |
| 178 | + args, kwargs = received[-1] |
| 179 | + assert kwargs == {} |
| 180 | + assert args == (native,), ( |
| 181 | + "Random.__del__ must call _delete with only native_object, " |
| 182 | + "but got args=%r" % (args,) |
| 183 | + ) |
| 184 | + finally: |
| 185 | + Random._delete = original |
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