exchangelib.autodiscover.discovery.pox API documentation

# Module `exchangelib.autodiscover.discovery.pox`

Expand source code

    import logging
    import time

    from ...configuration import Configuration
    from ...errors import AutoDiscoverFailed, RedirectError, TransportError, UnauthorizedError
    from ...protocol import Protocol
    from ...transport import AUTH_TYPE_MAP, DEFAULT_HEADERS, GSSAPI, NOAUTH, get_auth_method_from_response
    from ...util import (
        CONNECTION_ERRORS,
        TLS_ERRORS,
        DummyResponse,
        ParseError,
        _back_off_if_needed,
        get_redirect_url,
        post_ratelimited,
    )
    from ..cache import autodiscover_cache
    from ..properties import Autodiscover
    from ..protocol import AutodiscoverProtocol
    from .base import BaseAutodiscovery

    log = logging.getLogger(__name__)

    def discover(email, credentials=None, auth_type=None, retry_policy=None):
        ad_response, protocol = PoxAutodiscovery(email=email, credentials=credentials).discover()
        protocol.config.auth_typ = auth_type
        protocol.config.retry_policy = retry_policy
        return ad_response, protocol

    class PoxAutodiscovery(BaseAutodiscovery):
        URL_PATH = "Autodiscover/Autodiscover.xml"

        def _build_response(self, ad_response):
            if not ad_response.autodiscover_smtp_address:
                # Autodiscover does not always return an email address. In that case, the requesting email should be used
                ad_response.user.autodiscover_smtp_address = self.email

            protocol = Protocol(
                config=Configuration(
                    service_endpoint=ad_response.protocol.ews_url,
                    credentials=self.credentials,
                    version=ad_response.version,
                    auth_type=ad_response.protocol.auth_type,
                )
            )
            return ad_response, protocol

        def _quick(self, protocol):
            try:
                r = self._get_authenticated_response(protocol=protocol)
            except TransportError as e:
                raise AutoDiscoverFailed(f"Response error: {e}")
            if r.status_code == 200:
                try:
                    ad = Autodiscover.from_bytes(bytes_content=r.content)
                except ParseError as e:
                    raise AutoDiscoverFailed(f"Invalid response: {e}")
                else:
                    return self._step_5(ad=ad)
            raise AutoDiscoverFailed(f"Invalid response code: {r.status_code}")

        def _get_unauthenticated_response(self, url, method="post"):
            """Get auth type by tasting headers from the server. Do POST requests be default. HEAD is too error-prone, and
            some servers are set up to redirect to OWA on all requests except POST to the autodiscover endpoint.

            :param url:
            :param method:  (Default value = 'post')
            :return:
            """
            # We are connecting to untrusted servers here, so take necessary precautions.
            self._ensure_valid_hostname(url)

            kwargs = dict(
                url=url, headers=DEFAULT_HEADERS.copy(), allow_redirects=False, timeout=AutodiscoverProtocol.TIMEOUT
            )
            if method == "post":
                kwargs["data"] = Autodiscover.payload(email=self.email)
            retry = 0
            t_start = time.monotonic()
            while True:
                _back_off_if_needed(self.INITIAL_RETRY_POLICY.back_off_until)
                log.debug("Trying to get response from %s", url)
                with AutodiscoverProtocol.raw_session(url) as s:
                    try:
                        r = getattr(s, method)(**kwargs)
                        r.close()  # Release memory
                        break
                    except TLS_ERRORS as e:
                        # Don't retry on TLS errors. They will most likely be persistent.
                        raise TransportError(str(e))
                    except CONNECTION_ERRORS as e:
                        r = DummyResponse(url=url, request_headers=kwargs["headers"])
                        total_wait = time.monotonic() - t_start
                        if self.INITIAL_RETRY_POLICY.may_retry_on_error(response=r, wait=total_wait):
                            log.debug("Connection error on URL %s (retry %s, error: %s). Cool down", url, retry, e)
                            # Don't respect the 'Retry-After' header. We don't know if this is a useful endpoint, and we
                            # want autodiscover to be reasonably fast.
                            self.INITIAL_RETRY_POLICY.back_off(self.RETRY_WAIT)
                            retry += 1
                            continue
                        log.debug("Connection error on URL %s: %s", url, e)
                        raise TransportError(str(e))
            try:
                auth_type = get_auth_method_from_response(response=r)
            except UnauthorizedError:
                # Failed to guess the auth type
                auth_type = NOAUTH
            if r.status_code in (301, 302) and "location" in r.headers:
                # Make the redirect URL absolute
                try:
                    r.headers["location"] = get_redirect_url(r)
                except TransportError:
                    del r.headers["location"]
            return auth_type, r

        def _get_authenticated_response(self, protocol):
            """Get a response by using the credentials provided. We guess the auth type along the way.

            :param protocol:
            :return:
            """
            # Redo the request with the correct auth
            data = Autodiscover.payload(email=self.email)
            headers = DEFAULT_HEADERS.copy()
            session = protocol.get_session()
            if GSSAPI in AUTH_TYPE_MAP and isinstance(session.auth, AUTH_TYPE_MAP[GSSAPI]):
                # https://docs.microsoft.com/en-us/exchange/client-developer/web-service-reference/pox-autodiscover-request-for-exchange
                headers["X-ClientCanHandle"] = "Negotiate"
            try:
                r, session = post_ratelimited(
                    protocol=protocol,
                    session=session,
                    url=protocol.service_endpoint,
                    headers=headers,
                    data=data,
                )
                protocol.release_session(session)
            except UnauthorizedError as e:
                # It's entirely possible for the endpoint to ask for login. We should continue if login fails because this
                # isn't necessarily the right endpoint to use.
                raise TransportError(str(e))
            except RedirectError as e:
                r = DummyResponse(url=protocol.service_endpoint, headers={"location": e.url}, status_code=302)
            return r

        def _attempt_response(self, url):
            """Return an (is_valid_response, response) tuple.

            :param url:
            :return:
            """
            self._urls_visited.append(url.lower())
            log.debug("Attempting to get a valid response from %s", url)
            try:
                auth_type, r = self._get_unauthenticated_response(url=url)
                ad_protocol = AutodiscoverProtocol(
                    config=Configuration(
                        service_endpoint=url,
                        credentials=self.credentials,
                        auth_type=auth_type,
                        retry_policy=self.INITIAL_RETRY_POLICY,
                    )
                )
                if auth_type != NOAUTH:
                    r = self._get_authenticated_response(protocol=ad_protocol)
            except TransportError as e:
                log.debug("Failed to get a response: %s", e)
                return False, None
            if r.status_code in (301, 302) and "location" in r.headers:
                redirect_url = get_redirect_url(r)
                if self._redirect_url_is_valid(url=redirect_url):
                    # The protocol does not specify this explicitly, but by looking at how testconnectivity.microsoft.com
                    # works, it seems that we should follow this URL now and try to get a valid response.
                    return self._attempt_response(url=redirect_url)
            if r.status_code == 200:
                try:
                    ad = Autodiscover.from_bytes(bytes_content=r.content)
                except ParseError as e:
                    log.debug("Invalid response: %s", e)
                else:
                    # We got a valid response. Unless this is a URL redirect response, we cache the result
                    if ad.response is None or not ad.response.redirect_url:
                        cache_key = self._cache_key
                        log.debug("Adding cache entry for key %s: %s", cache_key, ad_protocol.service_endpoint)
                        autodiscover_cache[cache_key] = ad_protocol
                    return True, ad
            return False, None

## Functions

`def discover(email, credentials=None, auth_type=None, retry_policy=None)`
  Expand source code

      def discover(email, credentials=None, auth_type=None, retry_policy=None):
          ad_response, protocol = PoxAutodiscovery(email=email, credentials=credentials).discover()
          protocol.config.auth_typ = auth_type
          protocol.config.retry_policy = retry_policy
          return ad_response, protocol

## Classes

`class PoxAutodiscovery (email, credentials=None)`

  Autodiscover is a Microsoft protocol for automatically getting the endpoint of the Exchange server and other connection-related settings holding the email address using only the email address, and username and password of the user.

  For a description of the protocol implemented, see "Autodiscover for Exchange ActiveSync developers":

  https://docs.microsoft.com/en-us/previous-versions/office/developer/exchange-server-interoperability-guidance/hh352638%28v%3dexchg.140%29

  Descriptions of the steps from the article are provided in their respective methods in this class.

  For a description of how to handle autodiscover error messages, see:

  https://docs.microsoft.com/en-us/exchange/client-developer/exchange-web-services/handling-autodiscover-error-messages

  A tip from the article: The client can perform steps 1 through 4 in any order or in parallel to expedite the process, but it must wait for responses to finish at each step before proceeding. Given that many organizations prefer to use the URL in step 2 to set up the Autodiscover service, the client might try this step first.

  Another possibly newer resource which has not yet been attempted is "Outlook 2016 Implementation of Autodiscover": https://support.microsoft.com/en-us/help/3211279/outlook-2016-implementation-of-autodiscover

  WARNING: The autodiscover protocol is very complicated. If you have problems autodiscovering using this implementation, start by doing an official test at https://testconnectivity.microsoft.com

  :param email: The email address to autodiscover :param credentials: Credentials with authorization to make autodiscover lookups for this Account (Default value = None)

  Expand source code

      class PoxAutodiscovery(BaseAutodiscovery):
          URL_PATH = "Autodiscover/Autodiscover.xml"

          def _build_response(self, ad_response):
              if not ad_response.autodiscover_smtp_address:
                  # Autodiscover does not always return an email address. In that case, the requesting email should be used
                  ad_response.user.autodiscover_smtp_address = self.email

              protocol = Protocol(
                  config=Configuration(
                      service_endpoint=ad_response.protocol.ews_url,
                      credentials=self.credentials,
                      version=ad_response.version,
                      auth_type=ad_response.protocol.auth_type,
                  )
              )
              return ad_response, protocol

          def _quick(self, protocol):
              try:
                  r = self._get_authenticated_response(protocol=protocol)
              except TransportError as e:
                  raise AutoDiscoverFailed(f"Response error: {e}")
              if r.status_code == 200:
                  try:
                      ad = Autodiscover.from_bytes(bytes_content=r.content)
                  except ParseError as e:
                      raise AutoDiscoverFailed(f"Invalid response: {e}")
                  else:
                      return self._step_5(ad=ad)
              raise AutoDiscoverFailed(f"Invalid response code: {r.status_code}")

          def _get_unauthenticated_response(self, url, method="post"):
              """Get auth type by tasting headers from the server. Do POST requests be default. HEAD is too error-prone, and
              some servers are set up to redirect to OWA on all requests except POST to the autodiscover endpoint.

              :param url:
              :param method:  (Default value = 'post')
              :return:
              """
              # We are connecting to untrusted servers here, so take necessary precautions.
              self._ensure_valid_hostname(url)

              kwargs = dict(
                  url=url, headers=DEFAULT_HEADERS.copy(), allow_redirects=False, timeout=AutodiscoverProtocol.TIMEOUT
              )
              if method == "post":
                  kwargs["data"] = Autodiscover.payload(email=self.email)
              retry = 0
              t_start = time.monotonic()
              while True:
                  _back_off_if_needed(self.INITIAL_RETRY_POLICY.back_off_until)
                  log.debug("Trying to get response from %s", url)
                  with AutodiscoverProtocol.raw_session(url) as s:
                      try:
                          r = getattr(s, method)(**kwargs)
                          r.close()  # Release memory
                          break
                      except TLS_ERRORS as e:
                          # Don't retry on TLS errors. They will most likely be persistent.
                          raise TransportError(str(e))
                      except CONNECTION_ERRORS as e:
                          r = DummyResponse(url=url, request_headers=kwargs["headers"])
                          total_wait = time.monotonic() - t_start
                          if self.INITIAL_RETRY_POLICY.may_retry_on_error(response=r, wait=total_wait):
                              log.debug("Connection error on URL %s (retry %s, error: %s). Cool down", url, retry, e)
                              # Don't respect the 'Retry-After' header. We don't know if this is a useful endpoint, and we
                              # want autodiscover to be reasonably fast.
                              self.INITIAL_RETRY_POLICY.back_off(self.RETRY_WAIT)
                              retry += 1
                              continue
                          log.debug("Connection error on URL %s: %s", url, e)
                          raise TransportError(str(e))
              try:
                  auth_type = get_auth_method_from_response(response=r)
              except UnauthorizedError:
                  # Failed to guess the auth type
                  auth_type = NOAUTH
              if r.status_code in (301, 302) and "location" in r.headers:
                  # Make the redirect URL absolute
                  try:
                      r.headers["location"] = get_redirect_url(r)
                  except TransportError:
                      del r.headers["location"]
              return auth_type, r

          def _get_authenticated_response(self, protocol):
              """Get a response by using the credentials provided. We guess the auth type along the way.

              :param protocol:
              :return:
              """
              # Redo the request with the correct auth
              data = Autodiscover.payload(email=self.email)
              headers = DEFAULT_HEADERS.copy()
              session = protocol.get_session()
              if GSSAPI in AUTH_TYPE_MAP and isinstance(session.auth, AUTH_TYPE_MAP[GSSAPI]):
                  # https://docs.microsoft.com/en-us/exchange/client-developer/web-service-reference/pox-autodiscover-request-for-exchange
                  headers["X-ClientCanHandle"] = "Negotiate"
              try:
                  r, session = post_ratelimited(
                      protocol=protocol,
                      session=session,
                      url=protocol.service_endpoint,
                      headers=headers,
                      data=data,
                  )
                  protocol.release_session(session)
              except UnauthorizedError as e:
                  # It's entirely possible for the endpoint to ask for login. We should continue if login fails because this
                  # isn't necessarily the right endpoint to use.
                  raise TransportError(str(e))
              except RedirectError as e:
                  r = DummyResponse(url=protocol.service_endpoint, headers={"location": e.url}, status_code=302)
              return r

          def _attempt_response(self, url):
              """Return an (is_valid_response, response) tuple.

              :param url:
              :return:
              """
              self._urls_visited.append(url.lower())
              log.debug("Attempting to get a valid response from %s", url)
              try:
                  auth_type, r = self._get_unauthenticated_response(url=url)
                  ad_protocol = AutodiscoverProtocol(
                      config=Configuration(
                          service_endpoint=url,
                          credentials=self.credentials,
                          auth_type=auth_type,
                          retry_policy=self.INITIAL_RETRY_POLICY,
                      )
                  )
                  if auth_type != NOAUTH:
                      r = self._get_authenticated_response(protocol=ad_protocol)
              except TransportError as e:
                  log.debug("Failed to get a response: %s", e)
                  return False, None
              if r.status_code in (301, 302) and "location" in r.headers:
                  redirect_url = get_redirect_url(r)
                  if self._redirect_url_is_valid(url=redirect_url):
                      # The protocol does not specify this explicitly, but by looking at how testconnectivity.microsoft.com
                      # works, it seems that we should follow this URL now and try to get a valid response.
                      return self._attempt_response(url=redirect_url)
              if r.status_code == 200:
                  try:
                      ad = Autodiscover.from_bytes(bytes_content=r.content)
                  except ParseError as e:
                      log.debug("Invalid response: %s", e)
                  else:
                      # We got a valid response. Unless this is a URL redirect response, we cache the result
                      if ad.response is None or not ad.response.redirect_url:
                          cache_key = self._cache_key
                          log.debug("Adding cache entry for key %s: %s", cache_key, ad_protocol.service_endpoint)
                          autodiscover_cache[cache_key] = ad_protocol
                      return True, ad
              return False, None

  ### Ancestors

  - BaseAutodiscovery

  ### Class variables

  `var URL_PATH`