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import sys
import types
import typing as t
import decorator as deco
from gssapi.raw.misc import GSSError
if t.TYPE_CHECKING:
from gssapi.sec_contexts import SecurityContext
def import_gssapi_extension(
name: str,
) -> t.Optional[types.ModuleType]:
"""Import a GSSAPI extension module
This method imports a GSSAPI extension module based
on the name of the extension (not including the
'ext_' prefix). If the extension is not available,
the method retuns None.
Args:
name (str): the name of the extension
Returns:
module: Either the extension module or None
"""
try:
path = 'gssapi.raw.ext_{0}'.format(name)
__import__(path)
return sys.modules[path]
except ImportError:
return None
def inquire_property(
name: str,
doc: t.Optional[str] = None
) -> property:
"""Creates a property based on an inquire result
This method creates a property that calls the
:python:`_inquire` method, and return the value of the
requested information.
Args:
name (str): the name of the 'inquire' result information
Returns:
property: the created property
"""
def inquire_property(self: "SecurityContext") -> t.Any:
if not self._started:
msg = (f"Cannot read {name} from a security context whose "
"establishment has not yet been started.")
raise AttributeError(msg)
return getattr(self._inquire(**{name: True}), name)
return property(inquire_property, doc=doc)
# use UTF-8 as the default encoding, like Python 3
_ENCODING = 'UTF-8'
def _get_encoding() -> str:
"""Gets the current encoding used for strings.
This value is used to encode and decode string
values like names.
Returns:
str: the current encoding
"""
return _ENCODING
def set_encoding(
enc: str,
) -> None:
"""Sets the current encoding used for strings
This value is used to encode and decode string
values like names.
Args:
enc: the encoding to use
"""
global _ENCODING
_ENCODING = enc
def _encode_dict(
d: t.Dict[t.Union[bytes, str], t.Union[bytes, str]],
) -> t.Dict[bytes, bytes]:
"""Encodes any relevant strings in a dict"""
def enc(x: t.Union[bytes, str]) -> bytes:
if isinstance(x, str):
return x.encode(_ENCODING)
else:
return x
return {enc(k): enc(v) for k, v in d.items()}
# in case of Python 3, just use exception chaining
@deco.decorator
def catch_and_return_token(
func: t.Callable,
self: "SecurityContext",
*args: t.Any,
**kwargs: t.Any,
) -> t.Optional[bytes]:
"""Optionally defer exceptions and return a token instead
When `__DEFER_STEP_ERRORS__` is set on the implementing class
or instance, methods wrapped with this wrapper will
catch and save their :python:`GSSError` exceptions and
instead return the result token attached to the exception.
The exception can be later retrived through :python:`_last_err`
(and :python:`_last_tb` when Python 2 is in use).
"""
try:
return func(self, *args, **kwargs)
except GSSError as e:
defer_step_errors = getattr(self, '__DEFER_STEP_ERRORS__', False)
if e.token is not None and defer_step_errors:
self._last_err = e
# skip the "return func" line above in the traceback
tb = e.__traceback__.tb_next # type: ignore[union-attr]
self._last_err.__traceback__ = tb
return e.token
else:
raise
@deco.decorator
def check_last_err(
func: t.Callable,
self: "SecurityContext",
*args: t.Any,
**kwargs: t.Any,
) -> t.Any:
"""Check and raise deferred errors before running the function
This method checks :python:`_last_err` before running the wrapped
function. If present and not None, the exception will be raised
with its original traceback.
"""
if self._last_err is not None:
try:
raise self._last_err
finally:
self._last_err = None
else:
return func(self, *args, **kwargs)
class CheckLastError(type):
"""Check for a deferred error on all methods
This metaclass applies the :python:`check_last_err` decorator
to all methods not prefixed by '_'.
Additionally, it enabled `__DEFER_STEP_ERRORS__` by default.
"""
def __new__(
cls,
name: str,
parents: t.Tuple[t.Type],
attrs: t.Dict[str, t.Any],
) -> "CheckLastError":
attrs['__DEFER_STEP_ERRORS__'] = True
for attr_name in attrs:
attr = attrs[attr_name]
# wrap only methods
if not isinstance(attr, types.FunctionType):
continue
if attr_name[0] != '_':
attrs[attr_name] = check_last_err(attr)
return super(CheckLastError, cls).__new__(cls, name, parents, attrs)
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