CasperSecurity
# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
import abc
import enum
import inspect
import sys
import typing
import warnings
# We use a UserWarning subclass, instead of DeprecationWarning, because CPython
# decided deprecation warnings should be invisble by default.
class CryptographyDeprecationWarning(UserWarning):
pass
# Several APIs were deprecated with no specific end-of-life date because of the
# ubiquity of their use. They should not be removed until we agree on when that
# cycle ends.
PersistentlyDeprecated2017 = CryptographyDeprecationWarning
PersistentlyDeprecated2019 = CryptographyDeprecationWarning
DeprecatedIn34 = CryptographyDeprecationWarning
def _check_bytes(name: str, value: bytes):
if not isinstance(value, bytes):
raise TypeError("{} must be bytes".format(name))
def _check_byteslike(name: str, value: bytes):
try:
memoryview(value)
except TypeError:
raise TypeError("{} must be bytes-like".format(name))
def read_only_property(name: str):
return property(lambda self: getattr(self, name))
def register_interface(iface):
def register_decorator(klass, *, check_annotations=False):
verify_interface(iface, klass, check_annotations=check_annotations)
iface.register(klass)
return klass
return register_decorator
def register_interface_if(predicate, iface):
def register_decorator(klass, *, check_annotations=False):
if predicate:
verify_interface(iface, klass, check_annotations=check_annotations)
iface.register(klass)
return klass
return register_decorator
def int_to_bytes(integer: int, length: typing.Optional[int] = None) -> bytes:
return integer.to_bytes(
length or (integer.bit_length() + 7) // 8 or 1, "big"
)
class InterfaceNotImplemented(Exception):
pass
def strip_annotation(signature):
return inspect.Signature(
[
param.replace(annotation=inspect.Parameter.empty)
for param in signature.parameters.values()
]
)
def verify_interface(iface, klass, *, check_annotations=False):
for method in iface.__abstractmethods__:
if not hasattr(klass, method):
raise InterfaceNotImplemented(
"{} is missing a {!r} method".format(klass, method)
)
if isinstance(getattr(iface, method), abc.abstractproperty):
# Can't properly verify these yet.
continue
sig = inspect.signature(getattr(iface, method))
actual = inspect.signature(getattr(klass, method))
if check_annotations:
ok = sig == actual
else:
ok = strip_annotation(sig) == strip_annotation(actual)
if not ok:
raise InterfaceNotImplemented(
"{}.{}'s signature differs from the expected. Expected: "
"{!r}. Received: {!r}".format(klass, method, sig, actual)
)
class _DeprecatedValue(object):
def __init__(self, value, message, warning_class):
self.value = value
self.message = message
self.warning_class = warning_class
class _ModuleWithDeprecations(object):
def __init__(self, module):
self.__dict__["_module"] = module
def __getattr__(self, attr):
obj = getattr(self._module, attr)
if isinstance(obj, _DeprecatedValue):
warnings.warn(obj.message, obj.warning_class, stacklevel=2)
obj = obj.value
return obj
def __setattr__(self, attr, value):
setattr(self._module, attr, value)
def __delattr__(self, attr):
obj = getattr(self._module, attr)
if isinstance(obj, _DeprecatedValue):
warnings.warn(obj.message, obj.warning_class, stacklevel=2)
delattr(self._module, attr)
def __dir__(self):
return ["_module"] + dir(self._module)
def deprecated(value, module_name, message, warning_class):
module = sys.modules[module_name]
if not isinstance(module, _ModuleWithDeprecations):
sys.modules[module_name] = _ModuleWithDeprecations(
module
) # type: ignore[assignment]
return _DeprecatedValue(value, message, warning_class)
def cached_property(func):
cached_name = "_cached_{}".format(func)
sentinel = object()
def inner(instance):
cache = getattr(instance, cached_name, sentinel)
if cache is not sentinel:
return cache
result = func(instance)
setattr(instance, cached_name, result)
return result
return property(inner)
int_from_bytes = deprecated(
int.from_bytes,
__name__,
"int_from_bytes is deprecated, use int.from_bytes instead",
DeprecatedIn34,
)
# Python 3.10 changed representation of enums. We use well-defined object
# representation and string representation from Python 3.9.
class Enum(enum.Enum):
def __repr__(self):
return f"<{self.__class__.__name__}.{self._name_}: {self._value_!r}>"
def __str__(self):
return f"{self.__class__.__name__}.{self._name_}"