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# -*- coding: utf-8 -*-
# Copyright 2020 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
from typing import TYPE_CHECKING, Awaitable, Callable, List, Optional
import attr
from synapse.handlers._base import BaseHandler
from synapse.http.server import respond_with_html
from synapse.types import UserID, contains_invalid_mxid_characters
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class MappingException(Exception):
"""Used to catch errors when mapping the UserInfo object
"""
@attr.s
class UserAttributes:
localpart = attr.ib(type=str)
display_name = attr.ib(type=Optional[str], default=None)
emails = attr.ib(type=List[str], default=attr.Factory(list))
class SsoHandler(BaseHandler):
# The number of attempts to ask the mapping provider for when generating an MXID.
_MAP_USERNAME_RETRIES = 1000
def __init__(self, hs: "HomeServer"):
super().__init__(hs)
self._registration_handler = hs.get_registration_handler()
self._error_template = hs.config.sso_error_template
def render_error(
self, request, error: str, error_description: Optional[str] = None
) -> None:
"""Renders the error template and responds with it.
This is used to show errors to the user. The template of this page can
be found under `synapse/res/templates/sso_error.html`.
Args:
request: The incoming request from the browser.
We'll respond with an HTML page describing the error.
error: A technical identifier for this error.
error_description: A human-readable description of the error.
"""
html = self._error_template.render(
error=error, error_description=error_description
)
respond_with_html(request, 400, html)
async def get_sso_user_by_remote_user_id(
self, auth_provider_id: str, remote_user_id: str
) -> Optional[str]:
"""
Maps the user ID of a remote IdP to a mxid for a previously seen user.
If the user has not been seen yet, this will return None.
Args:
auth_provider_id: A unique identifier for this SSO provider, e.g.
"oidc" or "saml".
remote_user_id: The user ID according to the remote IdP. This might
be an e-mail address, a GUID, or some other form. It must be
unique and immutable.
Returns:
The mxid of a previously seen user.
"""
logger.debug(
"Looking for existing mapping for user %s:%s",
auth_provider_id,
remote_user_id,
)
# Check if we already have a mapping for this user.
previously_registered_user_id = await self.store.get_user_by_external_id(
auth_provider_id, remote_user_id,
)
# A match was found, return the user ID.
if previously_registered_user_id is not None:
logger.info(
"Found existing mapping for IdP '%s' and remote_user_id '%s': %s",
auth_provider_id,
remote_user_id,
previously_registered_user_id,
)
return previously_registered_user_id
# No match.
return None
async def get_mxid_from_sso(
self,
auth_provider_id: str,
remote_user_id: str,
user_agent: str,
ip_address: str,
sso_to_matrix_id_mapper: Callable[[int], Awaitable[UserAttributes]],
grandfather_existing_users: Optional[Callable[[], Awaitable[Optional[str]]]],
) -> str:
"""
Given an SSO ID, retrieve the user ID for it and possibly register the user.
This first checks if the SSO ID has previously been linked to a matrix ID,
if it has that matrix ID is returned regardless of the current mapping
logic.
If a callable is provided for grandfathering users, it is called and can
potentially return a matrix ID to use. If it does, the SSO ID is linked to
this matrix ID for subsequent calls.
The mapping function is called (potentially multiple times) to generate
a localpart for the user.
If an unused localpart is generated, the user is registered from the
given user-agent and IP address and the SSO ID is linked to this matrix
ID for subsequent calls.
Args:
auth_provider_id: A unique identifier for this SSO provider, e.g.
"oidc" or "saml".
remote_user_id: The unique identifier from the SSO provider.
user_agent: The user agent of the client making the request.
ip_address: The IP address of the client making the request.
sso_to_matrix_id_mapper: A callable to generate the user attributes.
The only parameter is an integer which represents the amount of
times the returned mxid localpart mapping has failed.
grandfather_existing_users: A callable which can return an previously
existing matrix ID. The SSO ID is then linked to the returned
matrix ID.
Returns:
The user ID associated with the SSO response.
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.
"""
# first of all, check if we already have a mapping for this user
previously_registered_user_id = await self.get_sso_user_by_remote_user_id(
auth_provider_id, remote_user_id,
)
if previously_registered_user_id:
return previously_registered_user_id
# Check for grandfathering of users.
if grandfather_existing_users:
previously_registered_user_id = await grandfather_existing_users()
if previously_registered_user_id:
# Future logins should also match this user ID.
await self.store.record_user_external_id(
auth_provider_id, remote_user_id, previously_registered_user_id
)
return previously_registered_user_id
# Otherwise, generate a new user.
for i in range(self._MAP_USERNAME_RETRIES):
try:
attributes = await sso_to_matrix_id_mapper(i)
except Exception as e:
raise MappingException(
"Could not extract user attributes from SSO response: " + str(e)
)
logger.debug(
"Retrieved user attributes from user mapping provider: %r (attempt %d)",
attributes,
i,
)
if not attributes.localpart:
raise MappingException(
"Error parsing SSO response: SSO mapping provider plugin "
"did not return a localpart value"
)
# Check if this mxid already exists
user_id = UserID(attributes.localpart, self.server_name).to_string()
if not await self.store.get_users_by_id_case_insensitive(user_id):
# This mxid is free
break
else:
# Unable to generate a username in 1000 iterations
# Break and return error to the user
raise MappingException(
"Unable to generate a Matrix ID from the SSO response"
)
# Since the localpart is provided via a potentially untrusted module,
# ensure the MXID is valid before registering.
if contains_invalid_mxid_characters(attributes.localpart):
raise MappingException("localpart is invalid: %s" % (attributes.localpart,))
logger.debug("Mapped SSO user to local part %s", attributes.localpart)
registered_user_id = await self._registration_handler.register_user(
localpart=attributes.localpart,
default_display_name=attributes.display_name,
bind_emails=attributes.emails,
user_agent_ips=[(user_agent, ip_address)],
)
await self.store.record_user_external_id(
auth_provider_id, remote_user_id, registered_user_id
)
return registered_user_id
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