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136 lines
4.8 KiB
Python
136 lines
4.8 KiB
Python
2 years ago
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from typing import Any, Dict, NoReturn, Pattern, Tuple, Type, TypeVar, Union
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__all__ = [
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"ProtocolError",
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"LocalProtocolError",
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"RemoteProtocolError",
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"validate",
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"bytesify",
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]
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class ProtocolError(Exception):
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"""Exception indicating a violation of the HTTP/1.1 protocol.
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This as an abstract base class, with two concrete base classes:
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:exc:`LocalProtocolError`, which indicates that you tried to do something
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that HTTP/1.1 says is illegal, and :exc:`RemoteProtocolError`, which
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indicates that the remote peer tried to do something that HTTP/1.1 says is
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illegal. See :ref:`error-handling` for details.
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In addition to the normal :exc:`Exception` features, it has one attribute:
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.. attribute:: error_status_hint
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This gives a suggestion as to what status code a server might use if
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this error occurred as part of a request.
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For a :exc:`RemoteProtocolError`, this is useful as a suggestion for
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how you might want to respond to a misbehaving peer, if you're
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implementing a server.
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For a :exc:`LocalProtocolError`, this can be taken as a suggestion for
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how your peer might have responded to *you* if h11 had allowed you to
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continue.
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The default is 400 Bad Request, a generic catch-all for protocol
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violations.
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"""
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def __init__(self, msg: str, error_status_hint: int = 400) -> None:
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if type(self) is ProtocolError:
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raise TypeError("tried to directly instantiate ProtocolError")
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Exception.__init__(self, msg)
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self.error_status_hint = error_status_hint
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# Strategy: there are a number of public APIs where a LocalProtocolError can
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# be raised (send(), all the different event constructors, ...), and only one
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# public API where RemoteProtocolError can be raised
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# (receive_data()). Therefore we always raise LocalProtocolError internally,
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# and then receive_data will translate this into a RemoteProtocolError.
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#
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# Internally:
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# LocalProtocolError is the generic "ProtocolError".
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# Externally:
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# LocalProtocolError is for local errors and RemoteProtocolError is for
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# remote errors.
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class LocalProtocolError(ProtocolError):
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def _reraise_as_remote_protocol_error(self) -> NoReturn:
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# After catching a LocalProtocolError, use this method to re-raise it
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# as a RemoteProtocolError. This method must be called from inside an
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# except: block.
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#
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# An easy way to get an equivalent RemoteProtocolError is just to
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# modify 'self' in place.
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self.__class__ = RemoteProtocolError # type: ignore
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# But the re-raising is somewhat non-trivial -- you might think that
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# now that we've modified the in-flight exception object, that just
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# doing 'raise' to re-raise it would be enough. But it turns out that
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# this doesn't work, because Python tracks the exception type
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# (exc_info[0]) separately from the exception object (exc_info[1]),
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# and we only modified the latter. So we really do need to re-raise
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# the new type explicitly.
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# On py3, the traceback is part of the exception object, so our
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# in-place modification preserved it and we can just re-raise:
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raise self
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class RemoteProtocolError(ProtocolError):
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pass
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def validate(
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regex: Pattern[bytes], data: bytes, msg: str = "malformed data", *format_args: Any
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) -> Dict[str, bytes]:
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match = regex.fullmatch(data)
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if not match:
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if format_args:
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msg = msg.format(*format_args)
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raise LocalProtocolError(msg)
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return match.groupdict()
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# Sentinel values
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#
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# - Inherit identity-based comparison and hashing from object
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# - Have a nice repr
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# - Have a *bonus property*: type(sentinel) is sentinel
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#
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# The bonus property is useful if you want to take the return value from
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# next_event() and do some sort of dispatch based on type(event).
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_T_Sentinel = TypeVar("_T_Sentinel", bound="Sentinel")
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class Sentinel(type):
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def __new__(
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cls: Type[_T_Sentinel],
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name: str,
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bases: Tuple[type, ...],
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namespace: Dict[str, Any],
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**kwds: Any
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) -> _T_Sentinel:
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assert bases == (Sentinel,)
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v = super().__new__(cls, name, bases, namespace, **kwds)
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v.__class__ = v # type: ignore
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return v
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def __repr__(self) -> str:
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return self.__name__
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# Used for methods, request targets, HTTP versions, header names, and header
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# values. Accepts ascii-strings, or bytes/bytearray/memoryview/..., and always
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# returns bytes.
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def bytesify(s: Union[bytes, bytearray, memoryview, int, str]) -> bytes:
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# Fast-path:
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if type(s) is bytes:
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return s
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if isinstance(s, str):
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s = s.encode("ascii")
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if isinstance(s, int):
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raise TypeError("expected bytes-like object, not int")
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return bytes(s)
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