text: # -*- coding: utf-8 -*-
  # Copyright 2014-2016 OpenMarket Ltd
  # Copyright 2018 New Vector 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 abc
  import collections
  import html
  import logging
  import types
  import urllib
  from http import HTTPStatus
  from io import BytesIO
  from typing import Any, Callable, Dict, Iterator, List, Tuple, Union
  
  import jinja2
  from canonicaljson import iterencode_canonical_json, iterencode_pretty_printed_json
  from zope.interface import implementer
  
  from twisted.internet import defer, interfaces
  from twisted.python import failure
  from twisted.web import resource
  from twisted.web.server import NOT_DONE_YET, Request
  from twisted.web.static import File, NoRangeStaticProducer
  from twisted.web.util import redirectTo
  
  import synapse.events
  import synapse.metrics
  from synapse.api.errors import (
      CodeMessageException,
      Codes,
      RedirectException,
      SynapseError,
      UnrecognizedRequestError,
  )
  from synapse.http.site import SynapseRequest
  from synapse.logging.context import preserve_fn
  from synapse.logging.opentracing import trace_servlet
  from synapse.util import json_encoder
  from synapse.util.caches import intern_dict
  
  logger = logging.getLogger(__name__)
  
  HTML_ERROR_TEMPLATE = """<!DOCTYPE html>
  <html lang=en>
    <head>
      <meta charset="utf-8">
      <title>Error {code}</title>
    </head>
    <body>
       <p>{msg}</p>
    </body>
  </html>
  """
  
  
  def return_json_error(f: failure.Failure, request: SynapseRequest) -> None:
      """Sends a JSON error response to clients.
      """
  
      if f.check(SynapseError):
          error_code = f.value.code
          error_dict = f.value.error_dict()
  
          logger.info("%s SynapseError: %s - %s", request, error_code, f.value.msg)
      else:
          error_code = 500
          error_dict = {"error": "Internal server error", "errcode": Codes.UNKNOWN}
  
          logger.error(
              "Failed handle request via %r: %r",
              request.request_metrics.name,
              request,
              exc_info=(f.type, f.value, f.getTracebackObject()),
          )
  
      # Only respond with an error response if we haven't already started writing,
      # otherwise lets just kill the connection
      if request.startedWriting:
          if request.transport:
              try:
                  request.transport.abortConnection()
              except Exception:
                  # abortConnection throws if the connection is already closed
                  pass
      else:
          respond_with_json(
              request,
              error_code,
              error_dict,
              send_cors=True,
              pretty_print=_request_user_agent_is_curl(request),
          )
  
  
  def return_html_error(
      f: failure.Failure, request: Request, error_template: Union[str, jinja2.Template],
  ) -> None:
      """Sends an HTML error page corresponding to the given failure.
  
      Handles RedirectException and other CodeMessageExceptions (such as SynapseError)
  
      Args:
          f: the error to report
          request: the failing request
          error_template: the HTML template. Can be either a string (with `{code}`,
              `{msg}` placeholders), or a jinja2 template
      """
      if f.check(CodeMessageException):
          cme = f.value
          code = cme.code
          msg = cme.msg
  
          if isinstance(cme, RedirectException):
              logger.info("%s redirect to %s", request, cme.location)
              request.setHeader(b"location", cme.location)
              request.cookies.extend(cme.cookies)
          elif isinstance(cme, SynapseError):
              logger.info("%s SynapseError: %s - %s", request, code, msg)
          else:
              logger.error(
                  "Failed handle request %r",
                  request,
                  exc_info=(f.type, f.value, f.getTracebackObject()),
              )
      else:
          code = HTTPStatus.INTERNAL_SERVER_ERROR
          msg = "Internal server error"
  
          logger.error(
              "Failed handle request %r",
              request,
              exc_info=(f.type, f.value, f.getTracebackObject()),
          )
  
      if isinstance(error_template, str):
          body = error_template.format(code=code, msg=html.escape(msg))
      else:
          body = error_template.render(code=code, msg=msg)
  
      respond_with_html(request, code, body)
  
  
  def wrap_async_request_handler(h):
      """Wraps an async request handler so that it calls request.processing.
  
      This helps ensure that work done by the request handler after the request is completed
      is correctly recorded against the request metrics/logs.
  
      The handler method must have a signature of "handle_foo(self, request)",
      where "request" must be a SynapseRequest.
  
      The handler may return a deferred, in which case the completion of the request isn't
      logged until the deferred completes.
      """
  
      async def wrapped_async_request_handler(self, request):
          with request.processing():
              await h(self, request)
  
      # we need to preserve_fn here, because the synchronous render method won't yield for
      # us (obviously)
      return preserve_fn(wrapped_async_request_handler)
  
  
  class HttpServer:
      """ Interface for registering callbacks on a HTTP server
      """
  
      def register_paths(self, method, path_patterns, callback):
          """ Register a callback that gets fired if we receive a http request
          with the given method for a path that matches the given regex.
  
          If the regex contains groups these gets passed to the calback via
          an unpacked tuple.
  
          Args:
              method (str): The method to listen to.
              path_patterns (list<SRE_Pattern>): The regex used to match requests.
              callback (function): The function to fire if we receive a matched
                  request. The first argument will be the request object and
                  subsequent arguments will be any matched groups from the regex.
                  This should return a tuple of (code, response).
          """
          pass
  
  
  class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta):
      """Base class for resources that have async handlers.
  
      Sub classes can either implement `_async_render_<METHOD>` to handle
      requests by method, or override `_async_render` to handle all requests.
  
      Args:
          extract_context: Whether to attempt to extract the opentracing
              context from the request the servlet is handling.
      """
  
      def __init__(self, extract_context=False):
          super().__init__()
  
          self._extract_context = extract_context
  
      def render(self, request):
          """ This gets called by twisted every time someone sends us a request.
          """
          defer.ensureDeferred(self._async_render_wrapper(request))
          return NOT_DONE_YET
  
      @wrap_async_request_handler
      async def _async_render_wrapper(self, request: SynapseRequest):
          """This is a wrapper that delegates to `_async_render` and handles
          exceptions, return values, metrics, etc.
          """
          try:
              request.request_metrics.name = self.__class__.__name__
  
              with trace_servlet(request, self._extract_context):
                  callback_return = await self._async_render(request)
  
                  if callback_return is not None:
                      code, response = callback_return
                      self._send_response(request, code, response)
          except Exception:
              # failure.Failure() fishes the original Failure out
              # of our stack, and thus gives us a sensible stack
              # trace.
              f = failure.Failure()
              self._send_error_response(f, request)
  
      async def _async_render(self, request: Request):
          """Delegates to `_async_render_<METHOD>` methods, or returns a 400 if
          no appropriate method exists. Can be overriden in sub classes for
          different routing.
          """
          # Treat HEAD requests as GET requests.
          request_method = request.method.decode("ascii")
          if request_method == "HEAD":
              request_method = "GET"
  
          method_handler = getattr(self, "_async_render_%s" % (request_method,), None)
          if method_handler:
              raw_callback_return = method_handler(request)
  
              # Is it synchronous? We'll allow this for now.
              if isinstance(raw_callback_return, (defer.Deferred, types.CoroutineType)):
                  callback_return = await raw_callback_return
              else:
                  callback_return = raw_callback_return
  
              return callback_return
  
          _unrecognised_request_handler(request)
  
      @abc.abstractmethod
      def _send_response(
          self, request: SynapseRequest, code: int, response_object: Any,
      ) -> None:
          raise NotImplementedError()
  
      @abc.abstractmethod
      def _send_error_response(
          self, f: failure.Failure, request: SynapseRequest,
      ) -> None:
          raise NotImplementedError()
  
  
  class DirectServeJsonResource(_AsyncResource):
      """A resource that will call `self._async_on_<METHOD>` on new requests,
      formatting responses and errors as JSON.
      """
  
      def _send_response(
          self, request: Request, code: int, response_object: Any,
      ):
          """Implements _AsyncResource._send_response
          """
          # TODO: Only enable CORS for the requests that need it.
          respond_with_json(
              request,
              code,
              response_object,
              send_cors=True,
              pretty_print=_request_user_agent_is_curl(request),
              canonical_json=self.canonical_json,
          )
  
      def _send_error_response(
          self, f: failure.Failure, request: SynapseRequest,
      ) -> None:
          """Implements _AsyncResource._send_error_response
          """
          return_json_error(f, request)
  
  
  class JsonResource(DirectServeJsonResource):
      """ This implements the HttpServer interface and provides JSON support for
      Resources.
  
      Register callbacks via register_paths()
  
      Callbacks can return a tuple of status code and a dict in which case the
      the dict will automatically be sent to the client as a JSON object.
  
      The JsonResource is primarily intended for returning JSON, but callbacks
      may send something other than JSON, they may do so by using the methods
      on the request object and instead returning None.
      """
  
      isLeaf = True
  
      _PathEntry = collections.namedtuple(
          "_PathEntry", ["pattern", "callback", "servlet_classname"]
      )
  
      def __init__(self, hs, canonical_json=True, extract_context=False):
          super().__init__(extract_context)
  
          self.canonical_json = canonical_json
          self.clock = hs.get_clock()
          self.path_regexs = {}
          self.hs = hs
  
      def register_paths(self, method, path_patterns, callback, servlet_classname):
          """
          Registers a request handler against a regular expression. Later request URLs are
          checked against these regular expressions in order to identify an appropriate
          handler for that request.
  
          Args:
              method (str): GET, POST etc
  
              path_patterns (Iterable[str]): A list of regular expressions to which
                  the request URLs are compared.
  
              callback (function): The handler for the request. Usually a Servlet
  
              servlet_classname (str): The name of the handler to be used in prometheus
                  and opentracing logs.
          """
          method = method.encode("utf-8")  # method is bytes on py3
  
          for path_pattern in path_patterns:
              logger.debug("Registering for %s %s", method, path_pattern.pattern)
              self.path_regexs.setdefault(method, []).append(
                  self._PathEntry(path_pattern, callback, servlet_classname)
              )
  
      def _get_handler_for_request(
          self, request: SynapseRequest
      ) -> Tuple[Callable, str, Dict[str, str]]:
          """Finds a callback method to handle the given request.
  
          Returns:
              A tuple of the callback to use, the name of the servlet, and the
              key word arguments to pass to the callback
          """
          # Treat HEAD requests as GET requests.
          request_path = request.path.decode("ascii")
          request_method = request.method
          if request_method == b"HEAD":
              request_method = b"GET"
  
          # Loop through all the registered callbacks to check if the method
          # and path regex match
          for path_entry in self.path_regexs.get(request_method, []):
              m = path_entry.pattern.match(request_path)
              if m:
                  # We found a match!
                  return path_entry.callback, path_entry.servlet_classname, m.groupdict()
  
          # Huh. No one wanted to handle that? Fiiiiiine. Send 400.
          return _unrecognised_request_handler, "unrecognised_request_handler", {}
  
      async def _async_render(self, request):
          callback, servlet_classname, group_dict = self._get_handler_for_request(request)
  
          # Make sure we have an appopriate name for this handler in prometheus
          # (rather than the default of JsonResource).
          request.request_metrics.name = servlet_classname
  
          # Now trigger the callback. If it returns a response, we send it
          # here. If it throws an exception, that is handled by the wrapper
          # installed by @request_handler.
          kwargs = intern_dict(
              {
                  name: urllib.parse.unquote(value) if value else value
                  for name, value in group_dict.items()
              }
          )
  
          raw_callback_return = callback(request, **kwargs)
  
          # Is it synchronous? We'll allow this for now.
          if isinstance(raw_callback_return, (defer.Deferred, types.CoroutineType)):
              callback_return = await raw_callback_return
          else:
              callback_return = raw_callback_return
  
          return callback_return
  
  
  class DirectServeHtmlResource(_AsyncResource):
      """A resource that will call `self._async_on_<METHOD>` on new requests,
      formatting responses and errors as HTML.
      """
  
      # The error template to use for this resource
      ERROR_TEMPLATE = HTML_ERROR_TEMPLATE
  
      def _send_response(
          self, request: SynapseRequest, code: int, response_object: Any,
      ):
          """Implements _AsyncResource._send_response
          """
          # We expect to get bytes for us to write
          assert isinstance(response_object, bytes)
          html_bytes = response_object
  
          respond_with_html_bytes(request, 200, html_bytes)
  
      def _send_error_response(
          self, f: failure.Failure, request: SynapseRequest,
      ) -> None:
          """Implements _AsyncResource._send_error_response
          """
          return_html_error(f, request, self.ERROR_TEMPLATE)
  
  
  class StaticResource(File):
      """
      A resource that represents a plain non-interpreted file or directory.
  
      Differs from the File resource by adding clickjacking protection.
      """
  
      def render_GET(self, request: Request):
          set_clickjacking_protection_headers(request)
          return super().render_GET(request)
  
  
  def _unrecognised_request_handler(request):
      """Request handler for unrecognised requests
  
      This is a request handler suitable for return from
      _get_handler_for_request. It actually just raises an
      UnrecognizedRequestError.
  
      Args:
          request (twisted.web.http.Request):
      """
      raise UnrecognizedRequestError()
  
  
  class RootRedirect(resource.Resource):
      """Redirects the root '/' path to another path."""
  
      def __init__(self, path):
          resource.Resource.__init__(self)
          self.url = path
  
      def render_GET(self, request):
          return redirectTo(self.url.encode("ascii"), request)
  
      def getChild(self, name, request):
          if len(name) == 0:
              return self  # select ourselves as the child to render
          return resource.Resource.getChild(self, name, request)
  
  
  class OptionsResource(resource.Resource):
      """Responds to OPTION requests for itself and all children."""
  
      def render_OPTIONS(self, request):
          request.setResponseCode(204)
          request.setHeader(b"Content-Length", b"0")
  
          set_cors_headers(request)
  
          return b""
  
      def getChildWithDefault(self, path, request):
          if request.method == b"OPTIONS":
              return self  # select ourselves as the child to render
          return resource.Resource.getChildWithDefault(self, path, request)
  
  
  class RootOptionsRedirectResource(OptionsResource, RootRedirect):
      pass
  
  
  @implementer(interfaces.IPushProducer)
  class _ByteProducer:
      """
      Iteratively write bytes to the request.
      """
  
      # The minimum number of bytes for each chunk. Note that the last chunk will
      # usually be smaller than this.
      min_chunk_size = 1024
  
      def __init__(
          self, request: Request, iterator: Iterator[bytes],
      ):
          self._request = request
          self._iterator = iterator
          self._paused = False
  
          # Register the producer and start producing data.
          self._request.registerProducer(self, True)
          self.resumeProducing()
  
      def _send_data(self, data: List[bytes]) -> None:
          """
          Send a list of bytes as a chunk of a response.
          """
          if not data:
              return
          self._request.write(b"".join(data))
  
      def pauseProducing(self) -> None:
          self._paused = True
  
      def resumeProducing(self) -> None:
          # We've stopped producing in the meantime (note that this might be
          # re-entrant after calling write).
          if not self._request:
              return
  
          self._paused = False
  
          # Write until there's backpressure telling us to stop.
          while not self._paused:
              # Get the next chunk and write it to the request.
              #
              # The output of the JSON encoder is buffered and coalesced until
              # min_chunk_size is reached. This is because JSON encoders produce
              # very small output per iteration and the Request object converts
              # each call to write() to a separate chunk. Without this there would
              # be an explosion in bytes written (e.g. b"{" becoming "1\r\n{\r\n").
              #
              # Note that buffer stores a list of bytes (instead of appending to
              # bytes) to hopefully avoid many allocations.
              buffer = []
              buffered_bytes = 0
              while buffered_bytes < self.min_chunk_size:
                  try:
                      data = next(self._iterator)
                      buffer.append(data)
                      buffered_bytes += len(data)
                  except StopIteration:
                      # The entire JSON object has been serialized, write any
                      # remaining data, finalize the producer and the request, and
                      # clean-up any references.
                      self._send_data(buffer)
                      self._request.unregisterProducer()
                      self._request.finish()
                      self.stopProducing()
                      return
  
              self._send_data(buffer)
  
      def stopProducing(self) -> None:
          # Clear a circular reference.
          self._request = None
  
  
  def _encode_json_bytes(json_object: Any) -> Iterator[bytes]:
      """
      Encode an object into JSON. Returns an iterator of bytes.
      """
      for chunk in json_encoder.iterencode(json_object):
          yield chunk.encode("utf-8")
  
  
  def respond_with_json(
      request: Request,
      code: int,
      json_object: Any,
      send_cors: bool = False,
      pretty_print: bool = False,
      canonical_json: bool = True,
  ):
      """Sends encoded JSON in response to the given request.
  
      Args:
          request: The http request to respond to.
          code: The HTTP response code.
          json_object: The object to serialize to JSON.
          send_cors: Whether to send Cross-Origin Resource Sharing headers
              https://fetch.spec.whatwg.org/#http-cors-protocol
          pretty_print: Whether to include indentation and line-breaks in the
              resulting JSON bytes.
          canonical_json: Whether to use the canonicaljson algorithm when encoding
              the JSON bytes.
  
      Returns:
          twisted.web.server.NOT_DONE_YET if the request is still active.
      """
      # could alternatively use request.notifyFinish() and flip a flag when
      # the Deferred fires, but since the flag is RIGHT THERE it seems like
      # a waste.
      if request._disconnected:
          logger.warning(
              "Not sending response to request %s, already disconnected.", request
          )
          return None
  
      if pretty_print:
          encoder = iterencode_pretty_printed_json
      else:
          if canonical_json or synapse.events.USE_FROZEN_DICTS:
              encoder = iterencode_canonical_json
          else:
              encoder = _encode_json_bytes
  
      request.setResponseCode(code)
      request.setHeader(b"Content-Type", b"application/json")
      request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate")
  
      if send_cors:
          set_cors_headers(request)
  
      _ByteProducer(request, encoder(json_object))
      return NOT_DONE_YET
  
  
  def respond_with_json_bytes(
      request: Request, code: int, json_bytes: bytes, send_cors: bool = False,
  ):
      """Sends encoded JSON in response to the given request.
  
      Args:
          request: The http request to respond to.
          code: The HTTP response code.
          json_bytes: The json bytes to use as the response body.
          send_cors: Whether to send Cross-Origin Resource Sharing headers
              https://fetch.spec.whatwg.org/#http-cors-protocol
  
      Returns:
          twisted.web.server.NOT_DONE_YET if the request is still active.
      """
  
      request.setResponseCode(code)
      request.setHeader(b"Content-Type", b"application/json")
      request.setHeader(b"Content-Length", b"%d" % (len(json_bytes),))
      request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate")
  
      if send_cors:
          set_cors_headers(request)
  
      # note that this is zero-copy (the bytesio shares a copy-on-write buffer with
      # the original `bytes`).
      bytes_io = BytesIO(json_bytes)
  
      producer = NoRangeStaticProducer(request, bytes_io)
      producer.start()
      return NOT_DONE_YET
  
  
  def set_cors_headers(request: Request):
      """Set the CORS headers so that javascript running in a web browsers can
      use this API
  
      Args:
          request: The http request to add CORS to.
      """
      request.setHeader(b"Access-Control-Allow-Origin", b"*")
      request.setHeader(
          b"Access-Control-Allow-Methods", b"GET, HEAD, POST, PUT, DELETE, OPTIONS"
      )
      request.setHeader(
          b"Access-Control-Allow-Headers",
          b"Origin, X-Requested-With, Content-Type, Accept, Authorization",
      )
  
  
  def respond_with_html(request: Request, code: int, html: str):
      """
      Wraps `respond_with_html_bytes` by first encoding HTML from a str to UTF-8 bytes.
      """
      respond_with_html_bytes(request, code, html.encode("utf-8"))
  
  
  def respond_with_html_bytes(request: Request, code: int, html_bytes: bytes):
      """
      Sends HTML (encoded as UTF-8 bytes) as the response to the given request.
  
      Note that this adds clickjacking protection headers and finishes the request.
  
      Args:
          request: The http request to respond to.
          code: The HTTP response code.
          html_bytes: The HTML bytes to use as the response body.
      """
      # could alternatively use request.notifyFinish() and flip a flag when
      # the Deferred fires, but since the flag is RIGHT THERE it seems like
      # a waste.
      if request._disconnected:
          logger.warning(
              "Not sending response to request %s, already disconnected.", request
          )
          return
  
      request.setResponseCode(code)
      request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
      request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
  
      # Ensure this content cannot be embedded.
      set_clickjacking_protection_headers(request)
  
      request.write(html_bytes)
      finish_request(request)
  
  
  def set_clickjacking_protection_headers(request: Request):
      """
      Set headers to guard against clickjacking of embedded content.
  
      This sets the X-Frame-Options and Content-Security-Policy headers which instructs
      browsers to not allow the HTML of the response to be embedded onto another
      page.
  
      Args:
          request: The http request to add the headers to.
      """
      request.setHeader(b"X-Frame-Options", b"DENY")
      request.setHeader(b"Content-Security-Policy", b"frame-ancestors 'none';")
  
  
  def finish_request(request: Request):
      """ Finish writing the response to the request.
  
      Twisted throws a RuntimeException if the connection closed before the
      response was written but doesn't provide a convenient or reliable way to
      determine if the connection was closed. So we catch and log the RuntimeException
  
      You might think that ``request.notifyFinish`` could be used to tell if the
      request was finished. However the deferred it returns won't fire if the
      connection was already closed, meaning we'd have to have called the method
      right at the start of the request. By the time we want to write the response
      it will already be too late.
      """
      try:
          request.finish()
      except RuntimeError as e:
          logger.info("Connection disconnected before response was written: %r", e)
  
  
  def _request_user_agent_is_curl(request: Request) -> bool:
      user_agents = request.requestHeaders.getRawHeaders(b"User-Agent", default=[])
      for user_agent in user_agents:
          if b"curl" in user_agent:
              return True
      return False
  