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Merge pull request #6037 from matrix-org/rav/saml_mapping_work

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Update the process for mapping SAML2 users to matrix IDs
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Richard van der Hoff 2019-09-24 17:04:54 +01:00 committed by GitHub
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7 changed files with 280 additions and 10 deletions
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1
changelog.d/6037.feature Normal file
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@ -0,0 +1 @@
Make the process for mapping SAML2 users to matrix IDs more flexible.

26
docs/sample_config.yaml
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@ -1174,6 +1174,32 @@ saml2_config:
#
#saml_session_lifetime: 5m
# The SAML attribute (after mapping via the attribute maps) to use to derive
# the Matrix ID from. 'uid' by default.
#
#mxid_source_attribute: displayName
# The mapping system to use for mapping the saml attribute onto a matrix ID.
# Options include:
# * 'hexencode' (which maps unpermitted characters to '=xx')
# * 'dotreplace' (which replaces unpermitted characters with '.').
# The default is 'hexencode'.
#
#mxid_mapping: dotreplace
# In previous versions of synapse, the mapping from SAML attribute to MXID was
# always calculated dynamically rather than stored in a table. For backwards-
# compatibility, we will look for user_ids matching such a pattern before
# creating a new account.
#
# This setting controls the SAML attribute which will be used for this
# backwards-compatibility lookup. Typically it should be 'uid', but if the
# attribute maps are changed, it may be necessary to change it.
#
# The default is 'uid'.
#
#grandfathered_mxid_source_attribute: upn
# Enable CAS for registration and login.

78
synapse/config/saml2_config.py
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@ -14,7 +14,13 @@
# See the License for the specific language governing permissions and
# limitations under the License.
import re
from synapse.python_dependencies import DependencyException, check_requirements
from synapse.types import (
map_username_to_mxid_localpart,
mxid_localpart_allowed_characters,
)
from synapse.util.module_loader import load_python_module
from ._base import Config, ConfigError
@ -67,6 +73,14 @@ class SAML2Config(Config):
self.saml2_enabled = True
self.saml2_mxid_source_attribute = saml2_config.get(
"mxid_source_attribute", "uid"
)
self.saml2_grandfathered_mxid_source_attribute = saml2_config.get(
"grandfathered_mxid_source_attribute", "uid"
)
saml2_config_dict = self._default_saml_config_dict()
_dict_merge(
merge_dict=saml2_config.get("sp_config", {}), into_dict=saml2_config_dict
@ -87,6 +101,12 @@ class SAML2Config(Config):
saml2_config.get("saml_session_lifetime", "5m")
)
mapping = saml2_config.get("mxid_mapping", "hexencode")
try:
self.saml2_mxid_mapper = MXID_MAPPER_MAP[mapping]
except KeyError:
raise ConfigError("%s is not a known mxid_mapping" % (mapping,))
def _default_saml_config_dict(self):
import saml2
@ -94,6 +114,13 @@ class SAML2Config(Config):
if public_baseurl is None:
raise ConfigError("saml2_config requires a public_baseurl to be set")
required_attributes = {"uid", self.saml2_mxid_source_attribute}
optional_attributes = {"displayName"}
if self.saml2_grandfathered_mxid_source_attribute:
optional_attributes.add(self.saml2_grandfathered_mxid_source_attribute)
optional_attributes -= required_attributes
metadata_url = public_baseurl + "_matrix/saml2/metadata.xml"
response_url = public_baseurl + "_matrix/saml2/authn_response"
return {
@ -105,8 +132,9 @@ class SAML2Config(Config):
(response_url, saml2.BINDING_HTTP_POST)
]
},
"required_attributes": ["uid"],
"optional_attributes": ["mail", "surname", "givenname"],
"required_attributes": list(required_attributes),
"optional_attributes": list(optional_attributes),
# "name_id_format": saml2.saml.NAMEID_FORMAT_PERSISTENT,
}
},
}
@ -182,6 +210,52 @@ class SAML2Config(Config):
# The default is 5 minutes.
#
#saml_session_lifetime: 5m
# The SAML attribute (after mapping via the attribute maps) to use to derive
# the Matrix ID from. 'uid' by default.
#
#mxid_source_attribute: displayName
# The mapping system to use for mapping the saml attribute onto a matrix ID.
# Options include:
# * 'hexencode' (which maps unpermitted characters to '=xx')
# * 'dotreplace' (which replaces unpermitted characters with '.').
# The default is 'hexencode'.
#
#mxid_mapping: dotreplace
# In previous versions of synapse, the mapping from SAML attribute to MXID was
# always calculated dynamically rather than stored in a table. For backwards-
# compatibility, we will look for user_ids matching such a pattern before
# creating a new account.
#
# This setting controls the SAML attribute which will be used for this
# backwards-compatibility lookup. Typically it should be 'uid', but if the
# attribute maps are changed, it may be necessary to change it.
#
# The default is 'uid'.
#
#grandfathered_mxid_source_attribute: upn
""" % {
"config_dir_path": config_dir_path
}
DOT_REPLACE_PATTERN = re.compile(
("[^%s]" % (re.escape("".join(mxid_localpart_allowed_characters)),))
)
def dot_replace_for_mxid(username: str) -> str:
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,
}

106
synapse/handlers/saml_handler.py
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@ -21,6 +21,8 @@ from saml2.client import Saml2Client
from synapse.api.errors import SynapseError
from synapse.http.servlet import parse_string
from synapse.rest.client.v1.login import SSOAuthHandler
from synapse.types import UserID, map_username_to_mxid_localpart
from synapse.util.async_helpers import Linearizer
logger = logging.getLogger(__name__)
@ -29,12 +31,26 @@ class SamlHandler:
def __init__(self, hs):
self._saml_client = Saml2Client(hs.config.saml2_sp_config)
self._sso_auth_handler = SSOAuthHandler(hs)
self._registration_handler = hs.get_registration_handler()
self._clock = hs.get_clock()
self._datastore = hs.get_datastore()
self._hostname = hs.hostname
self._saml2_session_lifetime = hs.config.saml2_session_lifetime
self._mxid_source_attribute = hs.config.saml2_mxid_source_attribute
self._grandfathered_mxid_source_attribute = (
hs.config.saml2_grandfathered_mxid_source_attribute
)
self._mxid_mapper = hs.config.saml2_mxid_mapper
# identifier for the external_ids table
self._auth_provider_id = "saml"
# a map from saml session id to Saml2SessionData object
self._outstanding_requests_dict = {}
self._clock = hs.get_clock()
self._saml2_session_lifetime = hs.config.saml2_session_lifetime
# a lock on the mappings
self._mapping_lock = Linearizer(name="saml_mapping", clock=self._clock)
def handle_redirect_request(self, client_redirect_url):
"""Handle an incoming request to /login/sso/redirect
@ -60,7 +76,7 @@ class SamlHandler:
# this shouldn't happen!
raise Exception("prepare_for_authenticate didn't return a Location header")
def handle_saml_response(self, request):
async def handle_saml_response(self, request):
"""Handle an incoming request to /_matrix/saml2/authn_response
Args:
@ -77,6 +93,10 @@ class SamlHandler:
# the dict.
self.expire_sessions()
user_id = await self._map_saml_response_to_user(resp_bytes)
self._sso_auth_handler.complete_sso_login(user_id, request, relay_state)
async def _map_saml_response_to_user(self, resp_bytes):
try:
saml2_auth = self._saml_client.parse_authn_request_response(
resp_bytes,
@ -91,18 +111,88 @@ class SamlHandler:
logger.warning("SAML2 response was not signed")
raise SynapseError(400, "SAML2 response was not signed")
if "uid" not in saml2_auth.ava:
logger.info("SAML2 response: %s", saml2_auth.origxml)
logger.info("SAML2 mapped attributes: %s", saml2_auth.ava)
try:
remote_user_id = saml2_auth.ava["uid"][0]
except KeyError:
logger.warning("SAML2 response lacks a 'uid' attestation")
raise SynapseError(400, "uid not in SAML2 response")
try:
mxid_source = saml2_auth.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,)
)
self._outstanding_requests_dict.pop(saml2_auth.in_response_to, None)
username = saml2_auth.ava["uid"][0]
displayName = saml2_auth.ava.get("displayName", [None])[0]
return self._sso_auth_handler.on_successful_auth(
username, request, relay_state, user_display_name=displayName
)
with (await self._mapping_lock.queue(self._auth_provider_id)):
# first of all, check if we already have a mapping for this user
logger.info(
"Looking for existing mapping for user %s:%s",
self._auth_provider_id,
remote_user_id,
)
registered_user_id = await self._datastore.get_user_by_external_id(
self._auth_provider_id, remote_user_id
)
if registered_user_id is not None:
logger.info("Found existing mapping %s", registered_user_id)
return registered_user_id
# 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._hostname
).to_string()
logger.info(
"Looking for existing account based on mapped %s %s",
self._grandfathered_mxid_source_attribute,
user_id,
)
users = await self._datastore.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)
await self._datastore.record_user_external_id(
self._auth_provider_id, remote_user_id, registered_user_id
)
return registered_user_id
# figure out a new mxid for this user
base_mxid_localpart = self._mxid_mapper(mxid_source)
suffix = 0
while True:
localpart = base_mxid_localpart + (str(suffix) if suffix else "")
if not await self._datastore.get_users_by_id_case_insensitive(
UserID(localpart, self._hostname).to_string()
):
break
suffix += 1
logger.info("Allocating mxid for new user with localpart %s", localpart)
registered_user_id = await self._registration_handler.register_user(
localpart=localpart, default_display_name=displayName
)
await self._datastore.record_user_external_id(
self._auth_provider_id, remote_user_id, registered_user_id
)
return registered_user_id
def expire_sessions(self):
expire_before = self._clock.time_msec() - self._saml2_session_lifetime

14
synapse/rest/client/v1/login.py
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@ -29,6 +29,7 @@ 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
@ -507,6 +508,19 @@ class SSOAuthHandler(object):
localpart=localpart, default_display_name=user_display_name
)
self.complete_sso_login(registered_user_id, request, client_redirect_url)
def complete_sso_login(
self, registered_user_id: str, request: SynapseRequest, client_redirect_url: str
):
"""Having figured out a mxid for this user, complete the HTTP request
Args:
registered_user_id:
request:
client_redirect_url:
"""
login_token = self._macaroon_gen.generate_short_term_login_token(
registered_user_id
)

41
synapse/storage/registration.py
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@ -22,6 +22,7 @@ from six import iterkeys
from six.moves import range
from twisted.internet import defer
from twisted.internet.defer import Deferred
from synapse.api.constants import UserTypes
from synapse.api.errors import Codes, StoreError, SynapseError, ThreepidValidationError
@ -384,6 +385,26 @@ class RegistrationWorkerStore(SQLBaseStore):
return self.runInteraction("get_users_by_id_case_insensitive", f)
async def get_user_by_external_id(
self, auth_provider: str, external_id: str
) -> str:
"""Look up a user by their external auth id
Args:
auth_provider: identifier for the remote auth provider
external_id: id on that system
Returns:
str|None: the mxid of the user, or None if they are not known
"""
return await self._simple_select_one_onecol(
table="user_external_ids",
keyvalues={"auth_provider": auth_provider, "external_id": external_id},
retcol="user_id",
allow_none=True,
desc="get_user_by_external_id",
)
@defer.inlineCallbacks
def count_all_users(self):
"""Counts all users registered on the homeserver."""
@ -1032,6 +1053,26 @@ class RegistrationStore(
self._invalidate_cache_and_stream(txn, self.get_user_by_id, (user_id,))
txn.call_after(self.is_guest.invalidate, (user_id,))
def record_user_external_id(
self, auth_provider: str, external_id: str, user_id: str
) -> Deferred:
"""Record a mapping from an external user id to a mxid
Args:
auth_provider: identifier for the remote auth provider
external_id: id on that system
user_id: complete mxid that it is mapped to
"""
return self._simple_insert(
table="user_external_ids",
values={
"auth_provider": auth_provider,
"external_id": external_id,
"user_id": user_id,
},
desc="record_user_external_id",
)
def user_set_password_hash(self, user_id, password_hash):
"""
NB. This does *not* evict any cache because the one use for this

24
synapse/storage/schema/delta/56/user_external_ids.sql Normal file
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@ -0,0 +1,24 @@
/* 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.
*/
/*
* a table which records mappings from external auth providers to mxids
*/
CREATE TABLE IF NOT EXISTS user_external_ids (
auth_provider TEXT NOT NULL,
external_id TEXT NOT NULL,
user_id TEXT NOT NULL,
UNIQUE (auth_provider, external_id)
);