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Refactor the CAS code (move the logic out of the REST layer to a handler) (#7136)

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Patrick Cloke 2020-03-26 15:05:26 -04:00 committed by GitHub
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5 changed files with 226 additions and 154 deletions
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1
changelog.d/7136.misc Normal file
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@ -0,0 +1 @@
Refactored the CAS authentication logic to a separate class.

204
synapse/handlers/cas_handler.py Normal file
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@ -0,0 +1,204 @@
# -*- 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
import xml.etree.ElementTree as ET
from typing import AnyStr, Dict, Optional, Tuple
from six.moves import urllib
from twisted.web.client import PartialDownloadError
from synapse.api.errors import Codes, LoginError
from synapse.http.site import SynapseRequest
from synapse.types import UserID, map_username_to_mxid_localpart
logger = logging.getLogger(__name__)
class CasHandler:
"""
Utility class for to handle the response from a CAS SSO service.
Args:
hs (synapse.server.HomeServer)
"""
def __init__(self, hs):
self._hostname = hs.hostname
self._auth_handler = hs.get_auth_handler()
self._registration_handler = hs.get_registration_handler()
self._cas_server_url = hs.config.cas_server_url
self._cas_service_url = hs.config.cas_service_url
self._cas_displayname_attribute = hs.config.cas_displayname_attribute
self._cas_required_attributes = hs.config.cas_required_attributes
self._http_client = hs.get_proxied_http_client()
def _build_service_param(self, client_redirect_url: AnyStr) -> str:
return "%s%s?%s" % (
self._cas_service_url,
"/_matrix/client/r0/login/cas/ticket",
urllib.parse.urlencode({"redirectUrl": client_redirect_url}),
)
async def _handle_cas_response(
self, request: SynapseRequest, cas_response_body: str, client_redirect_url: str
) -> None:
"""
Retrieves the user and display name from the CAS response and continues with the authentication.
Args:
request: The original client request.
cas_response_body: The response from the CAS server.
client_redirect_url: The URl to redirect the client to when
everything is done.
"""
user, attributes = self._parse_cas_response(cas_response_body)
displayname = attributes.pop(self._cas_displayname_attribute, None)
for required_attribute, required_value in self._cas_required_attributes.items():
# If required attribute was not in CAS Response - Forbidden
if required_attribute not in attributes:
raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
# Also need to check value
if required_value is not None:
actual_value = attributes[required_attribute]
# If required attribute value does not match expected - Forbidden
if required_value != actual_value:
raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
await self._on_successful_auth(user, request, client_redirect_url, displayname)
def _parse_cas_response(
self, cas_response_body: str
) -> Tuple[str, Dict[str, Optional[str]]]:
"""
Retrieve the user and other parameters from the CAS response.
Args:
cas_response_body: The response from the CAS query.
Returns:
A tuple of the user and a mapping of other attributes.
"""
user = None
attributes = {}
try:
root = ET.fromstring(cas_response_body)
if not root.tag.endswith("serviceResponse"):
raise Exception("root of CAS response is not serviceResponse")
success = root[0].tag.endswith("authenticationSuccess")
for child in root[0]:
if child.tag.endswith("user"):
user = child.text
if child.tag.endswith("attributes"):
for attribute in child:
# ElementTree library expands the namespace in
# attribute tags to the full URL of the namespace.
# We don't care about namespace here and it will always
# be encased in curly braces, so we remove them.
tag = attribute.tag
if "}" in tag:
tag = tag.split("}")[1]
attributes[tag] = attribute.text
if user is None:
raise Exception("CAS response does not contain user")
except Exception:
logger.exception("Error parsing CAS response")
raise LoginError(401, "Invalid CAS response", errcode=Codes.UNAUTHORIZED)
if not success:
raise LoginError(
401, "Unsuccessful CAS response", errcode=Codes.UNAUTHORIZED
)
return user, attributes
async def _on_successful_auth(
self,
username: str,
request: SynapseRequest,
client_redirect_url: str,
user_display_name: Optional[str] = None,
) -> None:
"""Called once the user has successfully authenticated with the SSO.
Registers the user if necessary, and then returns a redirect (with
a login token) to the client.
Args:
username: the remote user id. We'll map this onto
something sane for a MXID localpath.
request: the incoming request from the browser. We'll
respond to it with a redirect.
client_redirect_url: the redirect_url the client gave us when
it first started the process.
user_display_name: if set, and we have to register a new user,
we will set their displayname to this.
"""
localpart = map_username_to_mxid_localpart(username)
user_id = UserID(localpart, self._hostname).to_string()
registered_user_id = await self._auth_handler.check_user_exists(user_id)
if not registered_user_id:
registered_user_id = await self._registration_handler.register_user(
localpart=localpart, default_display_name=user_display_name
)
self._auth_handler.complete_sso_login(
registered_user_id, request, client_redirect_url
)
def handle_redirect_request(self, client_redirect_url: bytes) -> bytes:
"""
Generates a URL to the CAS server where the client should be redirected.
Args:
client_redirect_url: The final URL the client should go to after the
user has negotiated SSO.
Returns:
The URL to redirect to.
"""
args = urllib.parse.urlencode(
{"service": self._build_service_param(client_redirect_url)}
)
return ("%s/login?%s" % (self._cas_server_url, args)).encode("ascii")
async def handle_ticket_request(
self, request: SynapseRequest, client_redirect_url: str, ticket: str
) -> None:
"""
Validates a CAS ticket sent by the client for login/registration.
On a successful request, writes a redirect to the request.
"""
uri = self._cas_server_url + "/proxyValidate"
args = {
"ticket": ticket,
"service": self._build_service_param(client_redirect_url),
}
try:
body = await self._http_client.get_raw(uri, args)
except PartialDownloadError as pde:
# Twisted raises this error if the connection is closed,
# even if that's being used old-http style to signal end-of-data
body = pde.response
await self._handle_cas_response(request, body, client_redirect_url)

169
synapse/rest/client/v1/login.py
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@ -14,11 +14,6 @@
# limitations under the License.
import logging
import xml.etree.ElementTree as ET
from six.moves import urllib
from twisted.web.client import PartialDownloadError
from synapse.api.errors import Codes, LoginError, SynapseError
from synapse.api.ratelimiting import Ratelimiter
@ -28,9 +23,10 @@ from synapse.http.servlet import (
parse_json_object_from_request,
parse_string,
)
from synapse.http.site import SynapseRequest
from synapse.rest.client.v2_alpha._base import client_patterns
from synapse.rest.well_known import WellKnownBuilder
from synapse.types import UserID, map_username_to_mxid_localpart
from synapse.types import UserID
from synapse.util.msisdn import phone_number_to_msisdn
logger = logging.getLogger(__name__)
@ -72,14 +68,6 @@ def login_id_thirdparty_from_phone(identifier):
return {"type": "m.id.thirdparty", "medium": "msisdn", "address": msisdn}
def build_service_param(cas_service_url, client_redirect_url):
return "%s%s?redirectUrl=%s" % (
cas_service_url,
"/_matrix/client/r0/login/cas/ticket",
urllib.parse.quote(client_redirect_url, safe=""),
)
class LoginRestServlet(RestServlet):
PATTERNS = client_patterns("/login$", v1=True)
CAS_TYPE = "m.login.cas"
@ -409,7 +397,7 @@ class BaseSSORedirectServlet(RestServlet):
PATTERNS = client_patterns("/login/(cas|sso)/redirect", v1=True)
def on_GET(self, request):
def on_GET(self, request: SynapseRequest):
args = request.args
if b"redirectUrl" not in args:
return 400, "Redirect URL not specified for SSO auth"
@ -418,15 +406,15 @@ class BaseSSORedirectServlet(RestServlet):
request.redirect(sso_url)
finish_request(request)
def get_sso_url(self, client_redirect_url):
def get_sso_url(self, client_redirect_url: bytes) -> bytes:
"""Get the URL to redirect to, to perform SSO auth
Args:
client_redirect_url (bytes): the URL that we should redirect the
client_redirect_url: the URL that we should redirect the
client to when everything is done
Returns:
bytes: URL to redirect to
URL to redirect to
"""
# to be implemented by subclasses
raise NotImplementedError()
@ -434,16 +422,10 @@ class BaseSSORedirectServlet(RestServlet):
class CasRedirectServlet(BaseSSORedirectServlet):
def __init__(self, hs):
super(CasRedirectServlet, self).__init__()
self.cas_server_url = hs.config.cas_server_url
self.cas_service_url = hs.config.cas_service_url
self._cas_handler = hs.get_cas_handler()
def get_sso_url(self, client_redirect_url):
args = urllib.parse.urlencode(
{"service": build_service_param(self.cas_service_url, client_redirect_url)}
)
return "%s/login?%s" % (self.cas_server_url, args)
def get_sso_url(self, client_redirect_url: bytes) -> bytes:
return self._cas_handler.handle_redirect_request(client_redirect_url)
class CasTicketServlet(RestServlet):
@ -451,81 +433,15 @@ class CasTicketServlet(RestServlet):
def __init__(self, hs):
super(CasTicketServlet, self).__init__()
self.cas_server_url = hs.config.cas_server_url
self.cas_service_url = hs.config.cas_service_url
self.cas_displayname_attribute = hs.config.cas_displayname_attribute
self.cas_required_attributes = hs.config.cas_required_attributes
self._sso_auth_handler = SSOAuthHandler(hs)
self._http_client = hs.get_proxied_http_client()
self._cas_handler = hs.get_cas_handler()
async def on_GET(self, request):
async def on_GET(self, request: SynapseRequest) -> None:
client_redirect_url = parse_string(request, "redirectUrl", required=True)
uri = self.cas_server_url + "/proxyValidate"
args = {
"ticket": parse_string(request, "ticket", required=True),
"service": build_service_param(self.cas_service_url, client_redirect_url),
}
try:
body = await self._http_client.get_raw(uri, args)
except PartialDownloadError as pde:
# Twisted raises this error if the connection is closed,
# even if that's being used old-http style to signal end-of-data
body = pde.response
result = await self.handle_cas_response(request, body, client_redirect_url)
return result
def handle_cas_response(self, request, cas_response_body, client_redirect_url):
user, attributes = self.parse_cas_response(cas_response_body)
displayname = attributes.pop(self.cas_displayname_attribute, None)
for required_attribute, required_value in self.cas_required_attributes.items():
# If required attribute was not in CAS Response - Forbidden
if required_attribute not in attributes:
raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
# Also need to check value
if required_value is not None:
actual_value = attributes[required_attribute]
# If required attribute value does not match expected - Forbidden
if required_value != actual_value:
raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
return self._sso_auth_handler.on_successful_auth(
user, request, client_redirect_url, displayname
ticket = parse_string(request, "ticket", required=True)
await self._cas_handler.handle_ticket_request(
request, client_redirect_url, ticket
)
def parse_cas_response(self, cas_response_body):
user = None
attributes = {}
try:
root = ET.fromstring(cas_response_body)
if not root.tag.endswith("serviceResponse"):
raise Exception("root of CAS response is not serviceResponse")
success = root[0].tag.endswith("authenticationSuccess")
for child in root[0]:
if child.tag.endswith("user"):
user = child.text
if child.tag.endswith("attributes"):
for attribute in child:
# ElementTree library expands the namespace in
# attribute tags to the full URL of the namespace.
# We don't care about namespace here and it will always
# be encased in curly braces, so we remove them.
tag = attribute.tag
if "}" in tag:
tag = tag.split("}")[1]
attributes[tag] = attribute.text
if user is None:
raise Exception("CAS response does not contain user")
except Exception:
logger.exception("Error parsing CAS response")
raise LoginError(401, "Invalid CAS response", errcode=Codes.UNAUTHORIZED)
if not success:
raise LoginError(
401, "Unsuccessful CAS response", errcode=Codes.UNAUTHORIZED
)
return user, attributes
class SAMLRedirectServlet(BaseSSORedirectServlet):
PATTERNS = client_patterns("/login/sso/redirect", v1=True)
@ -533,65 +449,10 @@ class SAMLRedirectServlet(BaseSSORedirectServlet):
def __init__(self, hs):
self._saml_handler = hs.get_saml_handler()
def get_sso_url(self, client_redirect_url):
def get_sso_url(self, client_redirect_url: bytes) -> bytes:
return self._saml_handler.handle_redirect_request(client_redirect_url)
class SSOAuthHandler(object):
"""
Utility class for Resources and Servlets which handle the response from a SSO
service
Args:
hs (synapse.server.HomeServer)
"""
def __init__(self, hs):
self._hostname = hs.hostname
self._auth_handler = hs.get_auth_handler()
self._registration_handler = hs.get_registration_handler()
self._macaroon_gen = hs.get_macaroon_generator()
# cast to tuple for use with str.startswith
self._whitelisted_sso_clients = tuple(hs.config.sso_client_whitelist)
async def on_successful_auth(
self, username, request, client_redirect_url, user_display_name=None
):
"""Called once the user has successfully authenticated with the SSO.
Registers the user if necessary, and then returns a redirect (with
a login token) to the client.
Args:
username (unicode|bytes): the remote user id. We'll map this onto
something sane for a MXID localpath.
request (SynapseRequest): the incoming request from the browser. We'll
respond to it with a redirect.
client_redirect_url (unicode): the redirect_url the client gave us when
it first started the process.
user_display_name (unicode|None): if set, and we have to register a new user,
we will set their displayname to this.
Returns:
Deferred[none]: Completes once we have handled the request.
"""
localpart = map_username_to_mxid_localpart(username)
user_id = UserID(localpart, self._hostname).to_string()
registered_user_id = await self._auth_handler.check_user_exists(user_id)
if not registered_user_id:
registered_user_id = await self._registration_handler.register_user(
localpart=localpart, default_display_name=user_display_name
)
self._auth_handler.complete_sso_login(
registered_user_id, request, client_redirect_url
)
def register_servlets(hs, http_server):
LoginRestServlet(hs).register(http_server)
if hs.config.cas_enabled:

5
synapse/server.py
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@ -56,6 +56,7 @@ from synapse.handlers.account_validity import AccountValidityHandler
from synapse.handlers.acme import AcmeHandler
from synapse.handlers.appservice import ApplicationServicesHandler
from synapse.handlers.auth import AuthHandler, MacaroonGenerator
from synapse.handlers.cas_handler import CasHandler
from synapse.handlers.deactivate_account import DeactivateAccountHandler
from synapse.handlers.device import DeviceHandler, DeviceWorkerHandler
from synapse.handlers.devicemessage import DeviceMessageHandler
@ -198,6 +199,7 @@ class HomeServer(object):
"sendmail",
"registration_handler",
"account_validity_handler",
"cas_handler",
"saml_handler",
"event_client_serializer",
"password_policy_handler",
@ -529,6 +531,9 @@ class HomeServer(object):
def build_account_validity_handler(self):
return AccountValidityHandler(self)
def build_cas_handler(self):
return CasHandler(self)
def build_saml_handler(self):
from synapse.handlers.saml_handler import SamlHandler

1
tox.ini
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@ -186,6 +186,7 @@ commands = mypy \
synapse/federation/sender \
synapse/federation/transport \
synapse/handlers/auth.py \
synapse/handlers/cas_handler.py \
synapse/handlers/directory.py \
synapse/handlers/presence.py \
synapse/handlers/sync.py \