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Simplify the flow for SSO UIA (#8881)

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* SsoHandler: remove inheritance from BaseHandler

* Simplify the flow for SSO UIA

We don't need to do all the magic for mapping users when we are doing UIA, so
let's factor that out.
This commit is contained in:
Richard van der Hoff 2020-12-08 14:03:38 +00:00 committed by GitHub
parent 025fa06fc7
commit 36ba73f53d
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7 changed files with 144 additions and 40 deletions
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1
changelog.d/8881.misc Normal file
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@ -0,0 +1 @@
Simplify logic for handling user-interactive-auth via single-sign-on servers.

1
mypy.ini
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@ -43,6 +43,7 @@ files =
synapse/handlers/room_member.py,
synapse/handlers/room_member_worker.py,
synapse/handlers/saml_handler.py,
synapse/handlers/sso.py,
synapse/handlers/sync.py,
synapse/handlers/ui_auth,
synapse/http/client.py,

4
synapse/handlers/_base.py
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@ -32,6 +32,10 @@ logger = logging.getLogger(__name__)
class BaseHandler:
"""
Common base class for the event handlers.
Deprecated: new code should not use this. Instead, Handler classes should define the
fields they actually need. The utility methods should either be factored out to
standalone helper functions, or to different Handler classes.
"""
def __init__(self, hs: "HomeServer"):

11
synapse/handlers/auth.py
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@ -36,6 +36,8 @@ import attr
import bcrypt
import pymacaroons
from twisted.web.http import Request
from synapse.api.constants import LoginType
from synapse.api.errors import (
AuthError,
@ -1331,15 +1333,14 @@ class AuthHandler(BaseHandler):
)
async def complete_sso_ui_auth(
self, registered_user_id: str, session_id: str, request: SynapseRequest,
self, registered_user_id: str, session_id: str, request: Request,
):
"""Having figured out a mxid for this user, complete the HTTP request
Args:
registered_user_id: The registered user ID to complete SSO login for.
session_id: The ID of the user-interactive auth session.
request: The request to complete.
client_redirect_url: The URL to which to redirect the user at the end of the
process.
"""
# Mark the stage of the authentication as successful.
# Save the user who authenticated with SSO, this will be used to ensure
@ -1355,7 +1356,7 @@ class AuthHandler(BaseHandler):
async def complete_sso_login(
self,
registered_user_id: str,
request: SynapseRequest,
request: Request,
client_redirect_url: str,
extra_attributes: Optional[JsonDict] = None,
):
@ -1383,7 +1384,7 @@ class AuthHandler(BaseHandler):
def _complete_sso_login(
self,
registered_user_id: str,
request: SynapseRequest,
request: Request,
client_redirect_url: str,
extra_attributes: Optional[JsonDict] = None,
):

44
synapse/handlers/oidc_handler.py
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@ -674,6 +674,21 @@ class OidcHandler(BaseHandler):
self._sso_handler.render_error(request, "invalid_token", str(e))
return
# first check if we're doing a UIA
if ui_auth_session_id:
try:
remote_user_id = self._remote_id_from_userinfo(userinfo)
except Exception as e:
logger.exception("Could not extract remote user id")
self._sso_handler.render_error(request, "mapping_error", str(e))
return
return await self._sso_handler.complete_sso_ui_auth_request(
self._auth_provider_id, remote_user_id, ui_auth_session_id, request
)
# otherwise, it's a login
# Pull out the user-agent and IP from the request.
user_agent = request.get_user_agent("")
ip_address = self.hs.get_ip_from_request(request)
@ -698,14 +713,9 @@ class OidcHandler(BaseHandler):
extra_attributes = await get_extra_attributes(userinfo, token)
# and finally complete the login
if ui_auth_session_id:
await self._auth_handler.complete_sso_ui_auth(
user_id, ui_auth_session_id, request
)
else:
await self._auth_handler.complete_sso_login(
user_id, request, client_redirect_url, extra_attributes
)
await self._auth_handler.complete_sso_login(
user_id, request, client_redirect_url, extra_attributes
)
def _generate_oidc_session_token(
self,
@ -856,14 +866,11 @@ class OidcHandler(BaseHandler):
The mxid of the user
"""
try:
remote_user_id = self._user_mapping_provider.get_remote_user_id(userinfo)
remote_user_id = self._remote_id_from_userinfo(userinfo)
except Exception as e:
raise MappingException(
"Failed to extract subject from OIDC response: %s" % (e,)
)
# Some OIDC providers use integer IDs, but Synapse expects external IDs
# to be strings.
remote_user_id = str(remote_user_id)
# Older mapping providers don't accept the `failures` argument, so we
# try and detect support.
@ -933,6 +940,19 @@ class OidcHandler(BaseHandler):
grandfather_existing_users,
)
def _remote_id_from_userinfo(self, userinfo: UserInfo) -> str:
"""Extract the unique remote id from an OIDC UserInfo block
Args:
userinfo: An object representing the user given by the OIDC provider
Returns:
remote user id
"""
remote_user_id = self._user_mapping_provider.get_remote_user_id(userinfo)
# Some OIDC providers use integer IDs, but Synapse expects external IDs
# to be strings.
return str(remote_user_id)
UserAttributeDict = TypedDict(
"UserAttributeDict", {"localpart": str, "display_name": Optional[str]}

64
synapse/handlers/saml_handler.py
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@ -183,6 +183,24 @@ class SamlHandler(BaseHandler):
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._auth_provider_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.
for requirement in self._saml2_attribute_requirements:
@ -206,14 +224,7 @@ class SamlHandler(BaseHandler):
self._sso_handler.render_error(request, "mapping_error", str(e))
return
# Complete the interactive auth session or the login.
if current_session and current_session.ui_auth_session_id:
await self._auth_handler.complete_sso_ui_auth(
user_id, current_session.ui_auth_session_id, request
)
else:
await self._auth_handler.complete_sso_login(user_id, request, relay_state)
await self._auth_handler.complete_sso_login(user_id, request, relay_state)
async def _map_saml_response_to_user(
self,
@ -239,16 +250,10 @@ class SamlHandler(BaseHandler):
RedirectException: some mapping providers may raise this if they need
to redirect to an interstitial page.
"""
remote_user_id = self._user_mapping_provider.get_remote_user_id(
remote_user_id = self._remote_id_from_saml_response(
saml2_auth, client_redirect_url
)
if not remote_user_id:
raise MappingException(
"Failed to extract remote user id from SAML response"
)
async def saml_response_to_remapped_user_attributes(
failures: int,
) -> UserAttributes:
@ -304,6 +309,35 @@ class SamlHandler(BaseHandler):
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()

59
synapse/handlers/sso.py
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@ -17,8 +17,9 @@ from typing import TYPE_CHECKING, Awaitable, Callable, List, Optional
import attr
from twisted.web.http import Request
from synapse.api.errors import RedirectException
from synapse.handlers._base import BaseHandler
from synapse.http.server import respond_with_html
from synapse.types import UserID, contains_invalid_mxid_characters
@ -42,14 +43,16 @@ class UserAttributes:
emails = attr.ib(type=List[str], default=attr.Factory(list))
class SsoHandler(BaseHandler):
class SsoHandler:
# 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._store = hs.get_datastore()
self._server_name = hs.hostname
self._registration_handler = hs.get_registration_handler()
self._error_template = hs.config.sso_error_template
self._auth_handler = hs.get_auth_handler()
def render_error(
self, request, error: str, error_description: Optional[str] = None
@ -95,7 +98,7 @@ class SsoHandler(BaseHandler):
)
# Check if we already have a mapping for this user.
previously_registered_user_id = await self.store.get_user_by_external_id(
previously_registered_user_id = await self._store.get_user_by_external_id(
auth_provider_id, remote_user_id,
)
@ -181,7 +184,7 @@ class SsoHandler(BaseHandler):
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(
await self._store.record_user_external_id(
auth_provider_id, remote_user_id, previously_registered_user_id
)
return previously_registered_user_id
@ -214,8 +217,8 @@ class SsoHandler(BaseHandler):
)
# 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):
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:
@ -238,7 +241,47 @@ class SsoHandler(BaseHandler):
user_agent_ips=[(user_agent, ip_address)],
)
await self.store.record_user_external_id(
await self._store.record_user_external_id(
auth_provider_id, remote_user_id, registered_user_id
)
return registered_user_id
async def complete_sso_ui_auth_request(
self,
auth_provider_id: str,
remote_user_id: str,
ui_auth_session_id: str,
request: Request,
) -> None:
"""
Given an SSO ID, retrieve the user ID for it and complete UIA.
Note that this requires that the user is mapped in the "user_external_ids"
table. This will be the case if they have ever logged in via SAML or OIDC in
recentish synapse versions, but may not be for older users.
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.
ui_auth_session_id: The ID of the user-interactive auth session.
request: The request to complete.
"""
user_id = await self.get_sso_user_by_remote_user_id(
auth_provider_id, remote_user_id,
)
if not user_id:
logger.warning(
"Remote user %s/%s has not previously logged in here: UIA will fail",
auth_provider_id,
remote_user_id,
)
# Let the UIA flow handle this the same as if they presented creds for a
# different user.
user_id = ""
await self._auth_handler.complete_sso_ui_auth(
user_id, ui_auth_session_id, request
)