tahoe-lafs/src/allmydata/protocol_switch.py

"""
Support for listening with both HTTP and Foolscap on the same port.
"""

from typing import Optional, Tuple

from twisted.internet.protocol import Protocol
from twisted.internet.interfaces import ITransport
from twisted.internet.ssl import CertificateOptions, PrivateCertificate
from twisted.web.server import Site
from twisted.protocols.tls import TLSMemoryBIOFactory

from foolscap.negotiate import Negotiation

from .storage.http_server import HTTPServer
from .storage.server import StorageServer


class PretendToBeNegotiation(type):
    """😱"""

    def __instancecheck__(self, instance):
        return (instance.__class__ == self) or isinstance(instance, Negotiation)


class FoolscapOrHttp(Protocol, metaclass=PretendToBeNegotiation):
    """
    Based on initial query, decide whether we're talking Foolscap or HTTP.

    Pretends to be a ``foolscap.negotiate.Negotiation`` instance.
    """

    # These three will be set by a subclass
    swissnum: bytes
    certificate: PrivateCertificate
    storage_server: StorageServer

    def __init__(self, *args, **kwargs):
        self._foolscap: Negotiation = Negotiation(*args, **kwargs)
        self._buffer: bytes = b""

    def __setattr__(self, name, value):
        if name in {
            "_foolscap",
            "_buffer",
            "transport",
            "__class__",
        }:
            object.__setattr__(self, name, value)
        else:
            setattr(self._foolscap, name, value)

    def __getattr__(self, name):
        return getattr(self._foolscap, name)

    def _convert_to_negotiation(self) -> Tuple[bytes, Optional[ITransport]]:
        """Convert self to a ``Negotiation`` instance, return any buffered bytes"""
        transport = self.transport
        buf = self._buffer
        self.__class__ = Negotiation  # type: ignore
        self.__dict__ = self._foolscap.__dict__
        return buf, transport

    def initClient(self, *args, **kwargs):
        # After creation, a Negotiation instance either has initClient() or
        # initServer() called. SInce this is a client, we're never going to do
        # HTTP. Relying on __getattr__/__setattr__ doesn't work, for some
        # reason, so just mutate ourselves appropriately.
        assert not self._buffer
        self._convert_to_negotiation()
        return self.initClient(*args, **kwargs)

    def dataReceived(self, data: bytes) -> None:
        """Handle incoming data.

        Once we've decided which protocol we are, update self.__class__, at
        which point all methods will be called on the new class.
        """
        self._buffer += data
        if len(self._buffer) < 8:
            return

        # Check if it looks like a Foolscap request. If so, it can handle this
        # and later data:
        if self._buffer.startswith(b"GET /id/"):
            buf, transport = self._convert_to_negotiation()
            self.makeConnection(transport)
            self.dataReceived(buf)
            return
        else:
            certificate_options = CertificateOptions(
                privateKey=self.certificate.privateKey.original,
                certificate=self.certificate.original,
            )
            http_server = HTTPServer(self.storage_server, self.swissnum)
            factory = TLSMemoryBIOFactory(
                certificate_options, False, Site(http_server.get_resource())
            )
            assert self.transport is not None
            protocol = factory.buildProtocol(self.transport.getPeer())
            protocol.makeConnection(self.transport)
            protocol.dataReceived(self._buffer)
            self.__class__ = protocol.__class__
            self.__dict__ = protocol.__dict__


def create_foolscap_or_http_class():
    class FoolscapOrHttpWithCert(FoolscapOrHttp):
        pass

    return FoolscapOrHttpWithCert


def update_foolscap_or_http_class(cls, certificate, storage_server, swissnum):
    cls.certificate = certificate
    cls.storage_server = storage_server
    cls.swissnum = swissnum