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660 lines
26 KiB
Python
660 lines
26 KiB
Python
# This contains the main Connection class. Everything in h11 revolves around
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# this.
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from typing import (
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Any,
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Callable,
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cast,
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Dict,
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List,
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Optional,
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overload,
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Tuple,
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Type,
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Union,
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)
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from ._events import (
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ConnectionClosed,
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Data,
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EndOfMessage,
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Event,
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InformationalResponse,
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Request,
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Response,
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)
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from ._headers import get_comma_header, has_expect_100_continue, set_comma_header
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from ._readers import READERS, ReadersType
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from ._receivebuffer import ReceiveBuffer
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from ._state import (
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_SWITCH_CONNECT,
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_SWITCH_UPGRADE,
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CLIENT,
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ConnectionState,
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DONE,
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ERROR,
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MIGHT_SWITCH_PROTOCOL,
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SEND_BODY,
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SERVER,
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SWITCHED_PROTOCOL,
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)
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from ._util import ( # Import the internal things we need
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LocalProtocolError,
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RemoteProtocolError,
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Sentinel,
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)
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from ._writers import WRITERS, WritersType
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# Everything in __all__ gets re-exported as part of the h11 public API.
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__all__ = ["Connection", "NEED_DATA", "PAUSED"]
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class NEED_DATA(Sentinel, metaclass=Sentinel):
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pass
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class PAUSED(Sentinel, metaclass=Sentinel):
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pass
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# If we ever have this much buffered without it making a complete parseable
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# event, we error out. The only time we really buffer is when reading the
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# request/response line + headers together, so this is effectively the limit on
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# the size of that.
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#
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# Some precedents for defaults:
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# - node.js: 80 * 1024
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# - tomcat: 8 * 1024
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# - IIS: 16 * 1024
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# - Apache: <8 KiB per line>
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DEFAULT_MAX_INCOMPLETE_EVENT_SIZE = 16 * 1024
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# RFC 7230's rules for connection lifecycles:
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# - If either side says they want to close the connection, then the connection
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# must close.
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# - HTTP/1.1 defaults to keep-alive unless someone says Connection: close
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# - HTTP/1.0 defaults to close unless both sides say Connection: keep-alive
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# (and even this is a mess -- e.g. if you're implementing a proxy then
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# sending Connection: keep-alive is forbidden).
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#
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# We simplify life by simply not supporting keep-alive with HTTP/1.0 peers. So
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# our rule is:
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# - If someone says Connection: close, we will close
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# - If someone uses HTTP/1.0, we will close.
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def _keep_alive(event: Union[Request, Response]) -> bool:
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connection = get_comma_header(event.headers, b"connection")
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if b"close" in connection:
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return False
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if getattr(event, "http_version", b"1.1") < b"1.1":
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return False
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return True
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def _body_framing(
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request_method: bytes, event: Union[Request, Response]
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) -> Tuple[str, Union[Tuple[()], Tuple[int]]]:
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# Called when we enter SEND_BODY to figure out framing information for
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# this body.
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#
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# These are the only two events that can trigger a SEND_BODY state:
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assert type(event) in (Request, Response)
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# Returns one of:
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#
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# ("content-length", count)
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# ("chunked", ())
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# ("http/1.0", ())
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#
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# which are (lookup key, *args) for constructing body reader/writer
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# objects.
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#
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# Reference: https://tools.ietf.org/html/rfc7230#section-3.3.3
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#
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# Step 1: some responses always have an empty body, regardless of what the
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# headers say.
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if type(event) is Response:
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if (
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event.status_code in (204, 304)
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or request_method == b"HEAD"
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or (request_method == b"CONNECT" and 200 <= event.status_code < 300)
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):
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return ("content-length", (0,))
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# Section 3.3.3 also lists another case -- responses with status_code
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# < 200. For us these are InformationalResponses, not Responses, so
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# they can't get into this function in the first place.
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assert event.status_code >= 200
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# Step 2: check for Transfer-Encoding (T-E beats C-L):
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transfer_encodings = get_comma_header(event.headers, b"transfer-encoding")
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if transfer_encodings:
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assert transfer_encodings == [b"chunked"]
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return ("chunked", ())
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# Step 3: check for Content-Length
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content_lengths = get_comma_header(event.headers, b"content-length")
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if content_lengths:
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return ("content-length", (int(content_lengths[0]),))
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# Step 4: no applicable headers; fallback/default depends on type
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if type(event) is Request:
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return ("content-length", (0,))
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else:
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return ("http/1.0", ())
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################################################################
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#
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# The main Connection class
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#
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################################################################
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class Connection:
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"""An object encapsulating the state of an HTTP connection.
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Args:
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our_role: If you're implementing a client, pass :data:`h11.CLIENT`. If
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you're implementing a server, pass :data:`h11.SERVER`.
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max_incomplete_event_size (int):
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The maximum number of bytes we're willing to buffer of an
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incomplete event. In practice this mostly sets a limit on the
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maximum size of the request/response line + headers. If this is
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exceeded, then :meth:`next_event` will raise
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:exc:`RemoteProtocolError`.
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"""
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def __init__(
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self,
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our_role: Type[Sentinel],
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max_incomplete_event_size: int = DEFAULT_MAX_INCOMPLETE_EVENT_SIZE,
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) -> None:
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self._max_incomplete_event_size = max_incomplete_event_size
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# State and role tracking
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if our_role not in (CLIENT, SERVER):
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raise ValueError(f"expected CLIENT or SERVER, not {our_role!r}")
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self.our_role = our_role
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self.their_role: Type[Sentinel]
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if our_role is CLIENT:
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self.their_role = SERVER
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else:
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self.their_role = CLIENT
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self._cstate = ConnectionState()
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# Callables for converting data->events or vice-versa given the
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# current state
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self._writer = self._get_io_object(self.our_role, None, WRITERS)
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self._reader = self._get_io_object(self.their_role, None, READERS)
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# Holds any unprocessed received data
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self._receive_buffer = ReceiveBuffer()
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# If this is true, then it indicates that the incoming connection was
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# closed *after* the end of whatever's in self._receive_buffer:
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self._receive_buffer_closed = False
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# Extra bits of state that don't fit into the state machine.
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#
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# These two are only used to interpret framing headers for figuring
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# out how to read/write response bodies. their_http_version is also
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# made available as a convenient public API.
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self.their_http_version: Optional[bytes] = None
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self._request_method: Optional[bytes] = None
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# This is pure flow-control and doesn't at all affect the set of legal
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# transitions, so no need to bother ConnectionState with it:
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self.client_is_waiting_for_100_continue = False
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@property
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def states(self) -> Dict[Type[Sentinel], Type[Sentinel]]:
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"""A dictionary like::
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{CLIENT: <client state>, SERVER: <server state>}
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See :ref:`state-machine` for details.
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"""
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return dict(self._cstate.states)
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@property
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def our_state(self) -> Type[Sentinel]:
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"""The current state of whichever role we are playing. See
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:ref:`state-machine` for details.
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"""
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return self._cstate.states[self.our_role]
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@property
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def their_state(self) -> Type[Sentinel]:
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"""The current state of whichever role we are NOT playing. See
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:ref:`state-machine` for details.
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"""
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return self._cstate.states[self.their_role]
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@property
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def they_are_waiting_for_100_continue(self) -> bool:
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return self.their_role is CLIENT and self.client_is_waiting_for_100_continue
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def start_next_cycle(self) -> None:
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"""Attempt to reset our connection state for a new request/response
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cycle.
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If both client and server are in :data:`DONE` state, then resets them
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both to :data:`IDLE` state in preparation for a new request/response
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cycle on this same connection. Otherwise, raises a
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:exc:`LocalProtocolError`.
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See :ref:`keepalive-and-pipelining`.
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"""
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old_states = dict(self._cstate.states)
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self._cstate.start_next_cycle()
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self._request_method = None
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# self.their_http_version gets left alone, since it presumably lasts
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# beyond a single request/response cycle
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assert not self.client_is_waiting_for_100_continue
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self._respond_to_state_changes(old_states)
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def _process_error(self, role: Type[Sentinel]) -> None:
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old_states = dict(self._cstate.states)
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self._cstate.process_error(role)
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self._respond_to_state_changes(old_states)
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def _server_switch_event(self, event: Event) -> Optional[Type[Sentinel]]:
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if type(event) is InformationalResponse and event.status_code == 101:
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return _SWITCH_UPGRADE
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if type(event) is Response:
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if (
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_SWITCH_CONNECT in self._cstate.pending_switch_proposals
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and 200 <= event.status_code < 300
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):
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return _SWITCH_CONNECT
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return None
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# All events go through here
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def _process_event(self, role: Type[Sentinel], event: Event) -> None:
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# First, pass the event through the state machine to make sure it
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# succeeds.
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old_states = dict(self._cstate.states)
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if role is CLIENT and type(event) is Request:
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if event.method == b"CONNECT":
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self._cstate.process_client_switch_proposal(_SWITCH_CONNECT)
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if get_comma_header(event.headers, b"upgrade"):
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self._cstate.process_client_switch_proposal(_SWITCH_UPGRADE)
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server_switch_event = None
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if role is SERVER:
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server_switch_event = self._server_switch_event(event)
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self._cstate.process_event(role, type(event), server_switch_event)
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# Then perform the updates triggered by it.
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if type(event) is Request:
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self._request_method = event.method
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if role is self.their_role and type(event) in (
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Request,
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Response,
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InformationalResponse,
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):
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event = cast(Union[Request, Response, InformationalResponse], event)
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self.their_http_version = event.http_version
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# Keep alive handling
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#
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# RFC 7230 doesn't really say what one should do if Connection: close
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# shows up on a 1xx InformationalResponse. I think the idea is that
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# this is not supposed to happen. In any case, if it does happen, we
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# ignore it.
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if type(event) in (Request, Response) and not _keep_alive(
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cast(Union[Request, Response], event)
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):
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self._cstate.process_keep_alive_disabled()
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# 100-continue
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if type(event) is Request and has_expect_100_continue(event):
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self.client_is_waiting_for_100_continue = True
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if type(event) in (InformationalResponse, Response):
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self.client_is_waiting_for_100_continue = False
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if role is CLIENT and type(event) in (Data, EndOfMessage):
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self.client_is_waiting_for_100_continue = False
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self._respond_to_state_changes(old_states, event)
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def _get_io_object(
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self,
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role: Type[Sentinel],
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event: Optional[Event],
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io_dict: Union[ReadersType, WritersType],
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) -> Optional[Callable[..., Any]]:
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# event may be None; it's only used when entering SEND_BODY
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state = self._cstate.states[role]
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if state is SEND_BODY:
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# Special case: the io_dict has a dict of reader/writer factories
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# that depend on the request/response framing.
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framing_type, args = _body_framing(
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cast(bytes, self._request_method), cast(Union[Request, Response], event)
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)
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return io_dict[SEND_BODY][framing_type](*args) # type: ignore[index]
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else:
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# General case: the io_dict just has the appropriate reader/writer
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# for this state
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return io_dict.get((role, state)) # type: ignore[return-value]
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# This must be called after any action that might have caused
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# self._cstate.states to change.
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def _respond_to_state_changes(
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self,
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old_states: Dict[Type[Sentinel], Type[Sentinel]],
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event: Optional[Event] = None,
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) -> None:
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# Update reader/writer
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if self.our_state != old_states[self.our_role]:
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self._writer = self._get_io_object(self.our_role, event, WRITERS)
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if self.their_state != old_states[self.their_role]:
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self._reader = self._get_io_object(self.their_role, event, READERS)
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@property
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def trailing_data(self) -> Tuple[bytes, bool]:
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"""Data that has been received, but not yet processed, represented as
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a tuple with two elements, where the first is a byte-string containing
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the unprocessed data itself, and the second is a bool that is True if
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the receive connection was closed.
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See :ref:`switching-protocols` for discussion of why you'd want this.
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"""
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return (bytes(self._receive_buffer), self._receive_buffer_closed)
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def receive_data(self, data: bytes) -> None:
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"""Add data to our internal receive buffer.
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This does not actually do any processing on the data, just stores
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it. To trigger processing, you have to call :meth:`next_event`.
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Args:
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data (:term:`bytes-like object`):
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The new data that was just received.
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Special case: If *data* is an empty byte-string like ``b""``,
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then this indicates that the remote side has closed the
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connection (end of file). Normally this is convenient, because
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standard Python APIs like :meth:`file.read` or
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:meth:`socket.recv` use ``b""`` to indicate end-of-file, while
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other failures to read are indicated using other mechanisms
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like raising :exc:`TimeoutError`. When using such an API you
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can just blindly pass through whatever you get from ``read``
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to :meth:`receive_data`, and everything will work.
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But, if you have an API where reading an empty string is a
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valid non-EOF condition, then you need to be aware of this and
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make sure to check for such strings and avoid passing them to
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:meth:`receive_data`.
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Returns:
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Nothing, but after calling this you should call :meth:`next_event`
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to parse the newly received data.
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Raises:
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RuntimeError:
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Raised if you pass an empty *data*, indicating EOF, and then
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pass a non-empty *data*, indicating more data that somehow
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arrived after the EOF.
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(Calling ``receive_data(b"")`` multiple times is fine,
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and equivalent to calling it once.)
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"""
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if data:
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if self._receive_buffer_closed:
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raise RuntimeError("received close, then received more data?")
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self._receive_buffer += data
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else:
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self._receive_buffer_closed = True
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def _extract_next_receive_event(
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self,
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) -> Union[Event, Type[NEED_DATA], Type[PAUSED]]:
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state = self.their_state
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# We don't pause immediately when they enter DONE, because even in
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# DONE state we can still process a ConnectionClosed() event. But
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# if we have data in our buffer, then we definitely aren't getting
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# a ConnectionClosed() immediately and we need to pause.
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if state is DONE and self._receive_buffer:
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return PAUSED
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if state is MIGHT_SWITCH_PROTOCOL or state is SWITCHED_PROTOCOL:
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return PAUSED
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assert self._reader is not None
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event = self._reader(self._receive_buffer)
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if event is None:
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if not self._receive_buffer and self._receive_buffer_closed:
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# In some unusual cases (basically just HTTP/1.0 bodies), EOF
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# triggers an actual protocol event; in that case, we want to
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# return that event, and then the state will change and we'll
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# get called again to generate the actual ConnectionClosed().
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if hasattr(self._reader, "read_eof"):
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event = self._reader.read_eof()
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else:
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event = ConnectionClosed()
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if event is None:
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event = NEED_DATA
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return event # type: ignore[no-any-return]
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def next_event(self) -> Union[Event, Type[NEED_DATA], Type[PAUSED]]:
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"""Parse the next event out of our receive buffer, update our internal
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state, and return it.
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This is a mutating operation -- think of it like calling :func:`next`
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on an iterator.
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Returns:
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: One of three things:
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1) An event object -- see :ref:`events`.
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2) The special constant :data:`NEED_DATA`, which indicates that
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you need to read more data from your socket and pass it to
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:meth:`receive_data` before this method will be able to return
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any more events.
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3) The special constant :data:`PAUSED`, which indicates that we
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are not in a state where we can process incoming data (usually
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because the peer has finished their part of the current
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request/response cycle, and you have not yet called
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:meth:`start_next_cycle`). See :ref:`flow-control` for details.
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Raises:
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RemoteProtocolError:
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The peer has misbehaved. You should close the connection
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(possibly after sending some kind of 4xx response).
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Once this method returns :class:`ConnectionClosed` once, then all
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subsequent calls will also return :class:`ConnectionClosed`.
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If this method raises any exception besides :exc:`RemoteProtocolError`
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then that's a bug -- if it happens please file a bug report!
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If this method raises any exception then it also sets
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:attr:`Connection.their_state` to :data:`ERROR` -- see
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:ref:`error-handling` for discussion.
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"""
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if self.their_state is ERROR:
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raise RemoteProtocolError("Can't receive data when peer state is ERROR")
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try:
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event = self._extract_next_receive_event()
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if event not in [NEED_DATA, PAUSED]:
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self._process_event(self.their_role, cast(Event, event))
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if event is NEED_DATA:
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if len(self._receive_buffer) > self._max_incomplete_event_size:
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# 431 is "Request header fields too large" which is pretty
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# much the only situation where we can get here
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raise RemoteProtocolError(
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"Receive buffer too long", error_status_hint=431
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)
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if self._receive_buffer_closed:
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# We're still trying to complete some event, but that's
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# never going to happen because no more data is coming
|
|
raise RemoteProtocolError("peer unexpectedly closed connection")
|
|
return event
|
|
except BaseException as exc:
|
|
self._process_error(self.their_role)
|
|
if isinstance(exc, LocalProtocolError):
|
|
exc._reraise_as_remote_protocol_error()
|
|
else:
|
|
raise
|
|
|
|
@overload
|
|
def send(self, event: ConnectionClosed) -> None:
|
|
...
|
|
|
|
@overload
|
|
def send(
|
|
self, event: Union[Request, InformationalResponse, Response, Data, EndOfMessage]
|
|
) -> bytes:
|
|
...
|
|
|
|
@overload
|
|
def send(self, event: Event) -> Optional[bytes]:
|
|
...
|
|
|
|
def send(self, event: Event) -> Optional[bytes]:
|
|
"""Convert a high-level event into bytes that can be sent to the peer,
|
|
while updating our internal state machine.
|
|
|
|
Args:
|
|
event: The :ref:`event <events>` to send.
|
|
|
|
Returns:
|
|
If ``type(event) is ConnectionClosed``, then returns
|
|
``None``. Otherwise, returns a :term:`bytes-like object`.
|
|
|
|
Raises:
|
|
LocalProtocolError:
|
|
Sending this event at this time would violate our
|
|
understanding of the HTTP/1.1 protocol.
|
|
|
|
If this method raises any exception then it also sets
|
|
:attr:`Connection.our_state` to :data:`ERROR` -- see
|
|
:ref:`error-handling` for discussion.
|
|
|
|
"""
|
|
data_list = self.send_with_data_passthrough(event)
|
|
if data_list is None:
|
|
return None
|
|
else:
|
|
return b"".join(data_list)
|
|
|
|
def send_with_data_passthrough(self, event: Event) -> Optional[List[bytes]]:
|
|
"""Identical to :meth:`send`, except that in situations where
|
|
:meth:`send` returns a single :term:`bytes-like object`, this instead
|
|
returns a list of them -- and when sending a :class:`Data` event, this
|
|
list is guaranteed to contain the exact object you passed in as
|
|
:attr:`Data.data`. See :ref:`sendfile` for discussion.
|
|
|
|
"""
|
|
if self.our_state is ERROR:
|
|
raise LocalProtocolError("Can't send data when our state is ERROR")
|
|
try:
|
|
if type(event) is Response:
|
|
event = self._clean_up_response_headers_for_sending(event)
|
|
# We want to call _process_event before calling the writer,
|
|
# because if someone tries to do something invalid then this will
|
|
# give a sensible error message, while our writers all just assume
|
|
# they will only receive valid events. But, _process_event might
|
|
# change self._writer. So we have to do a little dance:
|
|
writer = self._writer
|
|
self._process_event(self.our_role, event)
|
|
if type(event) is ConnectionClosed:
|
|
return None
|
|
else:
|
|
# In any situation where writer is None, process_event should
|
|
# have raised ProtocolError
|
|
assert writer is not None
|
|
data_list: List[bytes] = []
|
|
writer(event, data_list.append)
|
|
return data_list
|
|
except:
|
|
self._process_error(self.our_role)
|
|
raise
|
|
|
|
def send_failed(self) -> None:
|
|
"""Notify the state machine that we failed to send the data it gave
|
|
us.
|
|
|
|
This causes :attr:`Connection.our_state` to immediately become
|
|
:data:`ERROR` -- see :ref:`error-handling` for discussion.
|
|
|
|
"""
|
|
self._process_error(self.our_role)
|
|
|
|
# When sending a Response, we take responsibility for a few things:
|
|
#
|
|
# - Sometimes you MUST set Connection: close. We take care of those
|
|
# times. (You can also set it yourself if you want, and if you do then
|
|
# we'll respect that and close the connection at the right time. But you
|
|
# don't have to worry about that unless you want to.)
|
|
#
|
|
# - The user has to set Content-Length if they want it. Otherwise, for
|
|
# responses that have bodies (e.g. not HEAD), then we will automatically
|
|
# select the right mechanism for streaming a body of unknown length,
|
|
# which depends on depending on the peer's HTTP version.
|
|
#
|
|
# This function's *only* responsibility is making sure headers are set up
|
|
# right -- everything downstream just looks at the headers. There are no
|
|
# side channels.
|
|
def _clean_up_response_headers_for_sending(self, response: Response) -> Response:
|
|
assert type(response) is Response
|
|
|
|
headers = response.headers
|
|
need_close = False
|
|
|
|
# HEAD requests need some special handling: they always act like they
|
|
# have Content-Length: 0, and that's how _body_framing treats
|
|
# them. But their headers are supposed to match what we would send if
|
|
# the request was a GET. (Technically there is one deviation allowed:
|
|
# we're allowed to leave out the framing headers -- see
|
|
# https://tools.ietf.org/html/rfc7231#section-4.3.2 . But it's just as
|
|
# easy to get them right.)
|
|
method_for_choosing_headers = cast(bytes, self._request_method)
|
|
if method_for_choosing_headers == b"HEAD":
|
|
method_for_choosing_headers = b"GET"
|
|
framing_type, _ = _body_framing(method_for_choosing_headers, response)
|
|
if framing_type in ("chunked", "http/1.0"):
|
|
# This response has a body of unknown length.
|
|
# If our peer is HTTP/1.1, we use Transfer-Encoding: chunked
|
|
# If our peer is HTTP/1.0, we use no framing headers, and close the
|
|
# connection afterwards.
|
|
#
|
|
# Make sure to clear Content-Length (in principle user could have
|
|
# set both and then we ignored Content-Length b/c
|
|
# Transfer-Encoding overwrote it -- this would be naughty of them,
|
|
# but the HTTP spec says that if our peer does this then we have
|
|
# to fix it instead of erroring out, so we'll accord the user the
|
|
# same respect).
|
|
headers = set_comma_header(headers, b"content-length", [])
|
|
if self.their_http_version is None or self.their_http_version < b"1.1":
|
|
# Either we never got a valid request and are sending back an
|
|
# error (their_http_version is None), so we assume the worst;
|
|
# or else we did get a valid HTTP/1.0 request, so we know that
|
|
# they don't understand chunked encoding.
|
|
headers = set_comma_header(headers, b"transfer-encoding", [])
|
|
# This is actually redundant ATM, since currently we
|
|
# unconditionally disable keep-alive when talking to HTTP/1.0
|
|
# peers. But let's be defensive just in case we add
|
|
# Connection: keep-alive support later:
|
|
if self._request_method != b"HEAD":
|
|
need_close = True
|
|
else:
|
|
headers = set_comma_header(headers, b"transfer-encoding", [b"chunked"])
|
|
|
|
if not self._cstate.keep_alive or need_close:
|
|
# Make sure Connection: close is set
|
|
connection = set(get_comma_header(headers, b"connection"))
|
|
connection.discard(b"keep-alive")
|
|
connection.add(b"close")
|
|
headers = set_comma_header(headers, b"connection", sorted(connection))
|
|
|
|
return Response(
|
|
headers=headers,
|
|
status_code=response.status_code,
|
|
http_version=response.http_version,
|
|
reason=response.reason,
|
|
)
|