Rename handler and config modules which end in handler/config. (#9816)

synapse/handlers/saml.py

@@ -0,0 +1,517 @@
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# 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 logging
+import re
+from typing import TYPE_CHECKING, Callable, Dict, Optional, Set, Tuple
+
+import attr
+import saml2
+import saml2.response
+from saml2.client import Saml2Client
+
+from synapse.api.errors import SynapseError
+from synapse.config import ConfigError
+from synapse.handlers._base import BaseHandler
+from synapse.handlers.sso import MappingException, UserAttributes
+from synapse.http.servlet import parse_string
+from synapse.http.site import SynapseRequest
+from synapse.module_api import ModuleApi
+from synapse.types import (
+    UserID,
+    map_username_to_mxid_localpart,
+    mxid_localpart_allowed_characters,
+)
+from synapse.util.iterutils import chunk_seq
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+@attr.s(slots=True)
+class Saml2SessionData:
+    """Data we track about SAML2 sessions"""
+
+    # time the session was created, in milliseconds
+    creation_time = attr.ib()
+    # The user interactive authentication session ID associated with this SAML
+    # session (or None if this SAML session is for an initial login).
+    ui_auth_session_id = attr.ib(type=Optional[str], default=None)
+
+
+class SamlHandler(BaseHandler):
+    def __init__(self, hs: "HomeServer"):
+        super().__init__(hs)
+        self._saml_client = Saml2Client(hs.config.saml2_sp_config)
+        self._saml_idp_entityid = hs.config.saml2_idp_entityid
+
+        self._saml2_session_lifetime = hs.config.saml2_session_lifetime
+        self._grandfathered_mxid_source_attribute = (
+            hs.config.saml2_grandfathered_mxid_source_attribute
+        )
+        self._saml2_attribute_requirements = hs.config.saml2.attribute_requirements
+        self._error_template = hs.config.sso_error_template
+
+        # plugin to do custom mapping from saml response to mxid
+        self._user_mapping_provider = hs.config.saml2_user_mapping_provider_class(
+            hs.config.saml2_user_mapping_provider_config,
+            ModuleApi(hs, hs.get_auth_handler()),
+        )
+
+        # identifier for the external_ids table
+        self.idp_id = "saml"
+
+        # user-facing name of this auth provider
+        self.idp_name = "SAML"
+
+        # we do not currently support icons/brands for SAML auth, but this is required by
+        # the SsoIdentityProvider protocol type.
+        self.idp_icon = None
+        self.idp_brand = None
+        self.unstable_idp_brand = None
+
+        # a map from saml session id to Saml2SessionData object
+        self._outstanding_requests_dict = {}  # type: Dict[str, Saml2SessionData]
+
+        self._sso_handler = hs.get_sso_handler()
+        self._sso_handler.register_identity_provider(self)
+
+    async def handle_redirect_request(
+        self,
+        request: SynapseRequest,
+        client_redirect_url: Optional[bytes],
+        ui_auth_session_id: Optional[str] = None,
+    ) -> str:
+        """Handle an incoming request to /login/sso/redirect
+
+        Args:
+            request: the incoming HTTP request
+            client_redirect_url: the URL that we should redirect the
+                client to after login (or None for UI Auth).
+            ui_auth_session_id: The session ID of the ongoing UI Auth (or
+                None if this is a login).
+
+        Returns:
+            URL to redirect to
+        """
+        if not client_redirect_url:
+            # Some SAML identity providers (e.g. Google) require a
+            # RelayState parameter on requests, so pass in a dummy redirect URL
+            # (which will never get used).
+            client_redirect_url = b"unused"
+
+        reqid, info = self._saml_client.prepare_for_authenticate(
+            entityid=self._saml_idp_entityid, relay_state=client_redirect_url
+        )
+
+        # Since SAML sessions timeout it is useful to log when they were created.
+        logger.info("Initiating a new SAML session: %s" % (reqid,))
+
+        now = self.clock.time_msec()
+        self._outstanding_requests_dict[reqid] = Saml2SessionData(
+            creation_time=now,
+            ui_auth_session_id=ui_auth_session_id,
+        )
+
+        for key, value in info["headers"]:
+            if key == "Location":
+                return value
+
+        # this shouldn't happen!
+        raise Exception("prepare_for_authenticate didn't return a Location header")
+
+    async def handle_saml_response(self, request: SynapseRequest) -> None:
+        """Handle an incoming request to /_synapse/client/saml2/authn_response
+
+        Args:
+            request: the incoming request from the browser. We'll
+                respond to it with a redirect.
+
+        Returns:
+            Completes once we have handled the request.
+        """
+        resp_bytes = parse_string(request, "SAMLResponse", required=True)
+        relay_state = parse_string(request, "RelayState", required=True)
+
+        # expire outstanding sessions before parse_authn_request_response checks
+        # the dict.
+        self.expire_sessions()
+
+        try:
+            saml2_auth = self._saml_client.parse_authn_request_response(
+                resp_bytes,
+                saml2.BINDING_HTTP_POST,
+                outstanding=self._outstanding_requests_dict,
+            )
+        except saml2.response.UnsolicitedResponse as e:
+            # the pysaml2 library helpfully logs an ERROR here, but neglects to log
+            # the session ID. I don't really want to put the full text of the exception
+            # in the (user-visible) exception message, so let's log the exception here
+            # so we can track down the session IDs later.
+            logger.warning(str(e))
+            self._sso_handler.render_error(
+                request, "unsolicited_response", "Unexpected SAML2 login."
+            )
+            return
+        except Exception as e:
+            self._sso_handler.render_error(
+                request,
+                "invalid_response",
+                "Unable to parse SAML2 response: %s." % (e,),
+            )
+            return
+
+        if saml2_auth.not_signed:
+            self._sso_handler.render_error(
+                request, "unsigned_respond", "SAML2 response was not signed."
+            )
+            return
+
+        logger.debug("SAML2 response: %s", saml2_auth.origxml)
+
+        await self._handle_authn_response(request, saml2_auth, relay_state)
+
+    async def _handle_authn_response(
+        self,
+        request: SynapseRequest,
+        saml2_auth: saml2.response.AuthnResponse,
+        relay_state: str,
+    ) -> None:
+        """Handle an AuthnResponse, having parsed it from the request params
+
+        Assumes that the signature on the response object has been checked. Maps
+        the user onto an MXID, registering them if necessary, and returns a response
+        to the browser.
+
+        Args:
+            request: the incoming request from the browser. We'll respond to it with an
+                HTML page or a redirect
+            saml2_auth: the parsed AuthnResponse object
+            relay_state: the RelayState query param, which encodes the URI to rediret
+               back to
+        """
+
+        for assertion in saml2_auth.assertions:
+            # kibana limits the length of a log field, whereas this is all rather
+            # useful, so split it up.
+            count = 0
+            for part in chunk_seq(str(assertion), 10000):
+                logger.info(
+                    "SAML2 assertion: %s%s", "(%i)..." % (count,) if count else "", part
+                )
+                count += 1
+
+        logger.info("SAML2 mapped attributes: %s", saml2_auth.ava)
+
+        current_session = self._outstanding_requests_dict.pop(
+            saml2_auth.in_response_to, None
+        )
+
+        # first check if we're doing a UIA
+        if current_session and current_session.ui_auth_session_id:
+            try:
+                remote_user_id = self._remote_id_from_saml_response(saml2_auth, None)
+            except MappingException as e:
+                logger.exception("Failed to extract remote user id from SAML response")
+                self._sso_handler.render_error(request, "mapping_error", str(e))
+                return
+
+            return await self._sso_handler.complete_sso_ui_auth_request(
+                self.idp_id,
+                remote_user_id,
+                current_session.ui_auth_session_id,
+                request,
+            )
+
+        # otherwise, we're handling a login request.
+
+        # Ensure that the attributes of the logged in user meet the required
+        # attributes.
+        if not self._sso_handler.check_required_attributes(
+            request, saml2_auth.ava, self._saml2_attribute_requirements
+        ):
+            return
+
+        # Call the mapper to register/login the user
+        try:
+            await self._complete_saml_login(saml2_auth, request, relay_state)
+        except MappingException as e:
+            logger.exception("Could not map user")
+            self._sso_handler.render_error(request, "mapping_error", str(e))
+
+    async def _complete_saml_login(
+        self,
+        saml2_auth: saml2.response.AuthnResponse,
+        request: SynapseRequest,
+        client_redirect_url: str,
+    ) -> None:
+        """
+        Given a SAML response, complete the login flow
+
+        Retrieves the remote user ID, registers the user if necessary, and serves
+        a redirect back to the client with a login-token.
+
+        Args:
+            saml2_auth: The parsed SAML2 response.
+            request: The request to respond to
+            client_redirect_url: The redirect URL passed in by the client.
+
+        Raises:
+            MappingException if there was a problem mapping the response to a user.
+            RedirectException: some mapping providers may raise this if they need
+                to redirect to an interstitial page.
+        """
+        remote_user_id = self._remote_id_from_saml_response(
+            saml2_auth, client_redirect_url
+        )
+
+        async def saml_response_to_remapped_user_attributes(
+            failures: int,
+        ) -> UserAttributes:
+            """
+            Call the mapping provider to map a SAML response to user attributes and coerce the result into the standard form.
+
+            This is backwards compatibility for abstraction for the SSO handler.
+            """
+            # Call the mapping provider.
+            result = self._user_mapping_provider.saml_response_to_user_attributes(
+                saml2_auth, failures, client_redirect_url
+            )
+            # Remap some of the results.
+            return UserAttributes(
+                localpart=result.get("mxid_localpart"),
+                display_name=result.get("displayname"),
+                emails=result.get("emails", []),
+            )
+
+        async def grandfather_existing_users() -> Optional[str]:
+            # backwards-compatibility hack: see if there is an existing user with a
+            # suitable mapping from the uid
+            if (
+                self._grandfathered_mxid_source_attribute
+                and self._grandfathered_mxid_source_attribute in saml2_auth.ava
+            ):
+                attrval = saml2_auth.ava[self._grandfathered_mxid_source_attribute][0]
+                user_id = UserID(
+                    map_username_to_mxid_localpart(attrval), self.server_name
+                ).to_string()
+
+                logger.debug(
+                    "Looking for existing account based on mapped %s %s",
+                    self._grandfathered_mxid_source_attribute,
+                    user_id,
+                )
+
+                users = await self.store.get_users_by_id_case_insensitive(user_id)
+                if users:
+                    registered_user_id = list(users.keys())[0]
+                    logger.info("Grandfathering mapping to %s", registered_user_id)
+                    return registered_user_id
+
+            return None
+
+        await self._sso_handler.complete_sso_login_request(
+            self.idp_id,
+            remote_user_id,
+            request,
+            client_redirect_url,
+            saml_response_to_remapped_user_attributes,
+            grandfather_existing_users,
+        )
+
+    def _remote_id_from_saml_response(
+        self,
+        saml2_auth: saml2.response.AuthnResponse,
+        client_redirect_url: Optional[str],
+    ) -> str:
+        """Extract the unique remote id from a SAML2 AuthnResponse
+
+        Args:
+            saml2_auth: The parsed SAML2 response.
+            client_redirect_url: The redirect URL passed in by the client.
+        Returns:
+            remote user id
+
+        Raises:
+            MappingException if there was an error extracting the user id
+        """
+        # It's not obvious why we need to pass in the redirect URI to the mapping
+        # provider, but we do :/
+        remote_user_id = self._user_mapping_provider.get_remote_user_id(
+            saml2_auth, client_redirect_url
+        )
+
+        if not remote_user_id:
+            raise MappingException(
+                "Failed to extract remote user id from SAML response"
+            )
+
+        return remote_user_id
+
+    def expire_sessions(self):
+        expire_before = self.clock.time_msec() - self._saml2_session_lifetime
+        to_expire = set()
+        for reqid, data in self._outstanding_requests_dict.items():
+            if data.creation_time < expire_before:
+                to_expire.add(reqid)
+        for reqid in to_expire:
+            logger.debug("Expiring session id %s", reqid)
+            del self._outstanding_requests_dict[reqid]
+
+
+DOT_REPLACE_PATTERN = re.compile(
+    ("[^%s]" % (re.escape("".join(mxid_localpart_allowed_characters)),))
+)
+
+
+def dot_replace_for_mxid(username: str) -> str:
+    """Replace any characters which are not allowed in Matrix IDs with a dot."""
+    username = username.lower()
+    username = DOT_REPLACE_PATTERN.sub(".", username)
+
+    # regular mxids aren't allowed to start with an underscore either
+    username = re.sub("^_", "", username)
+    return username
+
+
+MXID_MAPPER_MAP = {
+    "hexencode": map_username_to_mxid_localpart,
+    "dotreplace": dot_replace_for_mxid,
+}  # type: Dict[str, Callable[[str], str]]
+
+
+@attr.s
+class SamlConfig:
+    mxid_source_attribute = attr.ib()
+    mxid_mapper = attr.ib()
+
+
+class DefaultSamlMappingProvider:
+    __version__ = "0.0.1"
+
+    def __init__(self, parsed_config: SamlConfig, module_api: ModuleApi):
+        """The default SAML user mapping provider
+
+        Args:
+            parsed_config: Module configuration
+            module_api: module api proxy
+        """
+        self._mxid_source_attribute = parsed_config.mxid_source_attribute
+        self._mxid_mapper = parsed_config.mxid_mapper
+
+        self._grandfathered_mxid_source_attribute = (
+            module_api._hs.config.saml2_grandfathered_mxid_source_attribute
+        )
+
+    def get_remote_user_id(
+        self, saml_response: saml2.response.AuthnResponse, client_redirect_url: str
+    ) -> str:
+        """Extracts the remote user id from the SAML response"""
+        try:
+            return saml_response.ava["uid"][0]
+        except KeyError:
+            logger.warning("SAML2 response lacks a 'uid' attestation")
+            raise MappingException("'uid' not in SAML2 response")
+
+    def saml_response_to_user_attributes(
+        self,
+        saml_response: saml2.response.AuthnResponse,
+        failures: int,
+        client_redirect_url: str,
+    ) -> dict:
+        """Maps some text from a SAML response to attributes of a new user
+
+        Args:
+            saml_response: A SAML auth response object
+
+            failures: How many times a call to this function with this
+                saml_response has resulted in a failure
+
+            client_redirect_url: where the client wants to redirect to
+
+        Returns:
+            dict: A dict containing new user attributes. Possible keys:
+                * mxid_localpart (str): Required. The localpart of the user's mxid
+                * displayname (str): The displayname of the user
+                * emails (list[str]): Any emails for the user
+        """
+        try:
+            mxid_source = saml_response.ava[self._mxid_source_attribute][0]
+        except KeyError:
+            logger.warning(
+                "SAML2 response lacks a '%s' attestation",
+                self._mxid_source_attribute,
+            )
+            raise SynapseError(
+                400, "%s not in SAML2 response" % (self._mxid_source_attribute,)
+            )
+
+        # Use the configured mapper for this mxid_source
+        localpart = self._mxid_mapper(mxid_source)
+
+        # Append suffix integer if last call to this function failed to produce
+        # a usable mxid.
+        localpart += str(failures) if failures else ""
+
+        # Retrieve the display name from the saml response
+        # If displayname is None, the mxid_localpart will be used instead
+        displayname = saml_response.ava.get("displayName", [None])[0]
+
+        # Retrieve any emails present in the saml response
+        emails = saml_response.ava.get("email", [])
+
+        return {
+            "mxid_localpart": localpart,
+            "displayname": displayname,
+            "emails": emails,
+        }
+
+    @staticmethod
+    def parse_config(config: dict) -> SamlConfig:
+        """Parse the dict provided by the homeserver's config
+        Args:
+            config: A dictionary containing configuration options for this provider
+        Returns:
+            SamlConfig: A custom config object for this module
+        """
+        # Parse config options and use defaults where necessary
+        mxid_source_attribute = config.get("mxid_source_attribute", "uid")
+        mapping_type = config.get("mxid_mapping", "hexencode")
+
+        # Retrieve the associating mapping function
+        try:
+            mxid_mapper = MXID_MAPPER_MAP[mapping_type]
+        except KeyError:
+            raise ConfigError(
+                "saml2_config.user_mapping_provider.config: '%s' is not a valid "
+                "mxid_mapping value" % (mapping_type,)
+            )
+
+        return SamlConfig(mxid_source_attribute, mxid_mapper)
+
+    @staticmethod
+    def get_saml_attributes(config: SamlConfig) -> Tuple[Set[str], Set[str]]:
+        """Returns the required attributes of a SAML
+
+        Args:
+            config: A SamlConfig object containing configuration params for this provider
+
+        Returns:
+            The first set equates to the saml auth response
+                attributes that are required for the module to function, whereas the
+                second set consists of those attributes which can be used if
+                available, but are not necessary
+        """
+        return {"uid", config.mxid_source_attribute}, {"displayName", "email"}