text: # Copyright 2016 OpenMarket Ltd
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  import contextlib
  import logging
  import time
  from typing import Optional, Tuple, Union
  
  import attr
  from zope.interface import implementer
  
  from twisted.internet.interfaces import IAddress, IReactorTime
  from twisted.python.failure import Failure
  from twisted.web.resource import IResource
  from twisted.web.server import Request, Site
  
  from synapse.config.server import ListenerConfig
  from synapse.http import get_request_user_agent, redact_uri
  from synapse.http.request_metrics import RequestMetrics, requests_counter
  from synapse.logging.context import (
      ContextRequest,
      LoggingContext,
      PreserveLoggingContext,
  )
  from synapse.types import Requester
  
  logger = logging.getLogger(__name__)
  
  _next_request_seq = 0
  
  
  class SynapseRequest(Request):
      """Class which encapsulates an HTTP request to synapse.
  
      All of the requests processed in synapse are of this type.
  
      It extends twisted's twisted.web.server.Request, and adds:
       * Unique request ID
       * A log context associated with the request
       * Redaction of access_token query-params in __repr__
       * Logging at start and end
       * Metrics to record CPU, wallclock and DB time by endpoint.
       * A limit to the size of request which will be accepted
  
      It also provides a method `processing`, which returns a context manager. If this
      method is called, the request won't be logged until the context manager is closed;
      this is useful for asynchronous request handlers which may go on processing the
      request even after the client has disconnected.
  
      Attributes:
          logcontext: the log context for this request
      """
  
      def __init__(self, channel, *args, max_request_body_size=1024, **kw):
          Request.__init__(self, channel, *args, **kw)
          self._max_request_body_size = max_request_body_size
          self.site = channel.site  # type: SynapseSite
          self._channel = channel  # this is used by the tests
          self.start_time = 0.0
  
          # The requester, if authenticated. For federation requests this is the
          # server name, for client requests this is the Requester object.
          self._requester = None  # type: Optional[Union[Requester, str]]
  
          # we can't yet create the logcontext, as we don't know the method.
          self.logcontext = None  # type: Optional[LoggingContext]
  
          global _next_request_seq
          self.request_seq = _next_request_seq
          _next_request_seq += 1
  
          # whether an asynchronous request handler has called processing()
          self._is_processing = False
  
          # the time when the asynchronous request handler completed its processing
          self._processing_finished_time = None
  
          # what time we finished sending the response to the client (or the connection
          # dropped)
          self.finish_time = None
  
      def __repr__(self):
          # We overwrite this so that we don't log ``access_token``
          return "<%s at 0x%x method=%r uri=%r clientproto=%r site=%r>" % (
              self.__class__.__name__,
              id(self),
              self.get_method(),
              self.get_redacted_uri(),
              self.clientproto.decode("ascii", errors="replace"),
              self.site.site_tag,
          )
  
      def handleContentChunk(self, data):
          # we should have a `content` by now.
          assert self.content, "handleContentChunk() called before gotLength()"
          if self.content.tell() + len(data) > self._max_request_body_size:
              logger.warning(
                  "Aborting connection from %s because the request exceeds maximum size: %s %s",
                  self.client,
                  self.get_method(),
                  self.get_redacted_uri(),
              )
              self.transport.abortConnection()
              return
          super().handleContentChunk(data)
  
      @property
      def requester(self) -> Optional[Union[Requester, str]]:
          return self._requester
  
      @requester.setter
      def requester(self, value: Union[Requester, str]) -> None:
          # Store the requester, and update some properties based on it.
  
          # This should only be called once.
          assert self._requester is None
  
          self._requester = value
  
          # A logging context should exist by now (and have a ContextRequest).
          assert self.logcontext is not None
          assert self.logcontext.request is not None
  
          (
              requester,
              authenticated_entity,
          ) = self.get_authenticated_entity()
          self.logcontext.request.requester = requester
          # If there's no authenticated entity, it was the requester.
          self.logcontext.request.authenticated_entity = authenticated_entity or requester
  
      def get_request_id(self):
          return "%s-%i" % (self.get_method(), self.request_seq)
  
      def get_redacted_uri(self) -> str:
          """Gets the redacted URI associated with the request (or placeholder if the URI
          has not yet been received).
  
          Note: This is necessary as the placeholder value in twisted is str
          rather than bytes, so we need to sanitise `self.uri`.
  
          Returns:
              The redacted URI as a string.
          """
          uri = self.uri  # type: Union[bytes, str]
          if isinstance(uri, bytes):
              uri = uri.decode("ascii", errors="replace")
          return redact_uri(uri)
  
      def get_method(self) -> str:
          """Gets the method associated with the request (or placeholder if method
          has not yet been received).
  
          Note: This is necessary as the placeholder value in twisted is str
          rather than bytes, so we need to sanitise `self.method`.
  
          Returns:
              The request method as a string.
          """
          method = self.method  # type: Union[bytes, str]
          if isinstance(method, bytes):
              return self.method.decode("ascii")
          return method
  
      def get_authenticated_entity(self) -> Tuple[Optional[str], Optional[str]]:
          """
          Get the "authenticated" entity of the request, which might be the user
          performing the action, or a user being puppeted by a server admin.
  
          Returns:
              A tuple:
                  The first item is a string representing the user making the request.
  
                  The second item is a string or None representing the user who
                  authenticated when making this request. See
                  Requester.authenticated_entity.
          """
          # Convert the requester into a string that we can log
          if isinstance(self._requester, str):
              return self._requester, None
          elif isinstance(self._requester, Requester):
              requester = self._requester.user.to_string()
              authenticated_entity = self._requester.authenticated_entity
  
              # If this is a request where the target user doesn't match the user who
              # authenticated (e.g. and admin is puppetting a user) then we return both.
              if self._requester.user.to_string() != authenticated_entity:
                  return requester, authenticated_entity
  
              return requester, None
          elif self._requester is not None:
              # This shouldn't happen, but we log it so we don't lose information
              # and can see that we're doing something wrong.
              return repr(self._requester), None  # type: ignore[unreachable]
  
          return None, None
  
      def render(self, resrc):
          # this is called once a Resource has been found to serve the request; in our
          # case the Resource in question will normally be a JsonResource.
  
          # create a LogContext for this request
          request_id = self.get_request_id()
          self.logcontext = LoggingContext(
              request_id,
              request=ContextRequest(
                  request_id=request_id,
                  ip_address=self.getClientIP(),
                  site_tag=self.site.site_tag,
                  # The requester is going to be unknown at this point.
                  requester=None,
                  authenticated_entity=None,
                  method=self.get_method(),
                  url=self.get_redacted_uri(),
                  protocol=self.clientproto.decode("ascii", errors="replace"),
                  user_agent=get_request_user_agent(self),
              ),
          )
  
          # override the Server header which is set by twisted
          self.setHeader("Server", self.site.server_version_string)
  
          with PreserveLoggingContext(self.logcontext):
              # we start the request metrics timer here with an initial stab
              # at the servlet name. For most requests that name will be
              # JsonResource (or a subclass), and JsonResource._async_render
              # will update it once it picks a servlet.
              servlet_name = resrc.__class__.__name__
              self._started_processing(servlet_name)
  
              Request.render(self, resrc)
  
              # record the arrival of the request *after*
              # dispatching to the handler, so that the handler
              # can update the servlet name in the request
              # metrics
              requests_counter.labels(self.get_method(), self.request_metrics.name).inc()
  
      @contextlib.contextmanager
      def processing(self):
          """Record the fact that we are processing this request.
  
          Returns a context manager; the correct way to use this is:
  
          async def handle_request(request):
              with request.processing("FooServlet"):
                  await really_handle_the_request()
  
          Once the context manager is closed, the completion of the request will be logged,
          and the various metrics will be updated.
          """
          if self._is_processing:
              raise RuntimeError("Request is already processing")
          self._is_processing = True
  
          try:
              yield
          except Exception:
              # this should already have been caught, and sent back to the client as a 500.
              logger.exception(
                  "Asynchronous message handler raised an uncaught exception"
              )
          finally:
              # the request handler has finished its work and either sent the whole response
              # back, or handed over responsibility to a Producer.
  
              self._processing_finished_time = time.time()
              self._is_processing = False
  
              # if we've already sent the response, log it now; otherwise, we wait for the
              # response to be sent.
              if self.finish_time is not None:
                  self._finished_processing()
  
      def finish(self):
          """Called when all response data has been written to this Request.
  
          Overrides twisted.web.server.Request.finish to record the finish time and do
          logging.
          """
          self.finish_time = time.time()
          Request.finish(self)
          if not self._is_processing:
              assert self.logcontext is not None
              with PreserveLoggingContext(self.logcontext):
                  self._finished_processing()
  
      def connectionLost(self, reason):
          """Called when the client connection is closed before the response is written.
  
          Overrides twisted.web.server.Request.connectionLost to record the finish time and
          do logging.
          """
          # There is a bug in Twisted where reason is not wrapped in a Failure object
          # Detect this and wrap it manually as a workaround
          # More information: https://github.com/matrix-org/synapse/issues/7441
          if not isinstance(reason, Failure):
              reason = Failure(reason)
  
          self.finish_time = time.time()
          Request.connectionLost(self, reason)
  
          if self.logcontext is None:
              logger.info(
                  "Connection from %s lost before request headers were read", self.client
              )
              return
  
          # we only get here if the connection to the client drops before we send
          # the response.
          #
          # It's useful to log it here so that we can get an idea of when
          # the client disconnects.
          with PreserveLoggingContext(self.logcontext):
              logger.info("Connection from client lost before response was sent")
  
              if not self._is_processing:
                  self._finished_processing()
  
      def _started_processing(self, servlet_name):
          """Record the fact that we are processing this request.
  
          This will log the request's arrival. Once the request completes,
          be sure to call finished_processing.
  
          Args:
              servlet_name (str): the name of the servlet which will be
                  processing this request. This is used in the metrics.
  
                  It is possible to update this afterwards by updating
                  self.request_metrics.name.
          """
          self.start_time = time.time()
          self.request_metrics = RequestMetrics()
          self.request_metrics.start(
              self.start_time, name=servlet_name, method=self.get_method()
          )
  
          self.site.access_logger.debug(
              "%s - %s - Received request: %s %s",
              self.getClientIP(),
              self.site.site_tag,
              self.get_method(),
              self.get_redacted_uri(),
          )
  
      def _finished_processing(self):
          """Log the completion of this request and update the metrics"""
          assert self.logcontext is not None
          usage = self.logcontext.get_resource_usage()
  
          if self._processing_finished_time is None:
              # we completed the request without anything calling processing()
              self._processing_finished_time = time.time()
  
          # the time between receiving the request and the request handler finishing
          processing_time = self._processing_finished_time - self.start_time
  
          # the time between the request handler finishing and the response being sent
          # to the client (nb may be negative)
          response_send_time = self.finish_time - self._processing_finished_time
  
          user_agent = get_request_user_agent(self, "-")
  
          code = str(self.code)
          if not self.finished:
              # we didn't send the full response before we gave up (presumably because
              # the connection dropped)
              code += "!"
  
          log_level = logging.INFO if self._should_log_request() else logging.DEBUG
  
          # If this is a request where the target user doesn't match the user who
          # authenticated (e.g. and admin is puppetting a user) then we log both.
          requester, authenticated_entity = self.get_authenticated_entity()
          if authenticated_entity:
              requester = "{}.{}".format(authenticated_entity, requester)
  
          self.site.access_logger.log(
              log_level,
              "%s - %s - {%s}"
              " Processed request: %.3fsec/%.3fsec (%.3fsec, %.3fsec) (%.3fsec/%.3fsec/%d)"
              ' %sB %s "%s %s %s" "%s" [%d dbevts]',
              self.getClientIP(),
              self.site.site_tag,
              requester,
              processing_time,
              response_send_time,
              usage.ru_utime,
              usage.ru_stime,
              usage.db_sched_duration_sec,
              usage.db_txn_duration_sec,
              int(usage.db_txn_count),
              self.sentLength,
              code,
              self.get_method(),
              self.get_redacted_uri(),
              self.clientproto.decode("ascii", errors="replace"),
              user_agent,
              usage.evt_db_fetch_count,
          )
  
          try:
              self.request_metrics.stop(self.finish_time, self.code, self.sentLength)
          except Exception as e:
              logger.warning("Failed to stop metrics: %r", e)
  
      def _should_log_request(self) -> bool:
          """Whether we should log at INFO that we processed the request."""
          if self.path == b"/health":
              return False
  
          if self.method == b"OPTIONS":
              return False
  
          return True
  
  
  class XForwardedForRequest(SynapseRequest):
      """Request object which honours proxy headers
  
      Extends SynapseRequest to replace getClientIP, getClientAddress, and isSecure with
      information from request headers.
      """
  
      # the client IP and ssl flag, as extracted from the headers.
      _forwarded_for = None  # type: Optional[_XForwardedForAddress]
      _forwarded_https = False  # type: bool
  
      def requestReceived(self, command, path, version):
          # this method is called by the Channel once the full request has been
          # received, to dispatch the request to a resource.
          # We can use it to set the IP address and protocol according to the
          # headers.
          self._process_forwarded_headers()
          return super().requestReceived(command, path, version)
  
      def _process_forwarded_headers(self):
          headers = self.requestHeaders.getRawHeaders(b"x-forwarded-for")
          if not headers:
              return
  
          # for now, we just use the first x-forwarded-for header. Really, we ought
          # to start from the client IP address, and check whether it is trusted; if it
          # is, work backwards through the headers until we find an untrusted address.
          # see https://github.com/matrix-org/synapse/issues/9471
          self._forwarded_for = _XForwardedForAddress(
              headers[0].split(b",")[0].strip().decode("ascii")
          )
  
          # if we got an x-forwarded-for header, also look for an x-forwarded-proto header
          header = self.getHeader(b"x-forwarded-proto")
          if header is not None:
              self._forwarded_https = header.lower() == b"https"
          else:
              # this is done largely for backwards-compatibility so that people that
              # haven't set an x-forwarded-proto header don't get a redirect loop.
              logger.warning(
                  "forwarded request lacks an x-forwarded-proto header: assuming https"
              )
              self._forwarded_https = True
  
      def isSecure(self):
          if self._forwarded_https:
              return True
          return super().isSecure()
  
      def getClientIP(self) -> str:
          """
          Return the IP address of the client who submitted this request.
  
          This method is deprecated.  Use getClientAddress() instead.
          """
          if self._forwarded_for is not None:
              return self._forwarded_for.host
          return super().getClientIP()
  
      def getClientAddress(self) -> IAddress:
          """
          Return the address of the client who submitted this request.
          """
          if self._forwarded_for is not None:
              return self._forwarded_for
          return super().getClientAddress()
  
  
  @implementer(IAddress)
  @attr.s(frozen=True, slots=True)
  class _XForwardedForAddress:
      host = attr.ib(type=str)
  
  
  class SynapseSite(Site):
      """
      Synapse-specific twisted http Site
  
      This does two main things.
  
      First, it replaces the requestFactory in use so that we build SynapseRequests
      instead of regular t.w.server.Requests. All of the  constructor params are really
      just parameters for SynapseRequest.
  
      Second, it inhibits the log() method called by Request.finish, since SynapseRequest
      does its own logging.
      """
  
      def __init__(
          self,
          logger_name: str,
          site_tag: str,
          config: ListenerConfig,
          resource: IResource,
          server_version_string,
          max_request_body_size: int,
          reactor: IReactorTime,
      ):
          """
  
          Args:
              logger_name:  The name of the logger to use for access logs.
              site_tag:  A tag to use for this site - mostly in access logs.
              config:  Configuration for the HTTP listener corresponding to this site
              resource:  The base of the resource tree to be used for serving requests on
                  this site
              server_version_string: A string to present for the Server header
              max_request_body_size: Maximum request body length to allow before
                  dropping the connection
              reactor: reactor to be used to manage connection timeouts
          """
          Site.__init__(self, resource, reactor=reactor)
  
          self.site_tag = site_tag
  
          assert config.http_options is not None
          proxied = config.http_options.x_forwarded
          request_class = XForwardedForRequest if proxied else SynapseRequest
  
          def request_factory(channel, queued) -> Request:
              return request_class(
                  channel, max_request_body_size=max_request_body_size, queued=queued
              )
  
          self.requestFactory = request_factory  # type: ignore
          self.access_logger = logging.getLogger(logger_name)
          self.server_version_string = server_version_string.encode("ascii")
  
      def log(self, request):
          pass
  