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# Copyright 2023 The Matrix.org Foundation.
#
# 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, Any, Dict, List, Optional
from urllib.parse import urlencode
from authlib.oauth2 import ClientAuth
from authlib.oauth2.auth import encode_client_secret_basic, encode_client_secret_post
from authlib.oauth2.rfc7523 import ClientSecretJWT, PrivateKeyJWT, private_key_jwt_sign
from authlib.oauth2.rfc7662 import IntrospectionToken
from authlib.oidc.discovery import OpenIDProviderMetadata, get_well_known_url
from twisted.web.client import readBody
from twisted.web.http_headers import Headers
from synapse.api.auth.base import BaseAuth
from synapse.api.errors import AuthError, StoreError
from synapse.http.site import SynapseRequest
from synapse.logging.context import make_deferred_yieldable
from synapse.types import Requester, UserID, create_requester
from synapse.util import json_decoder
from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
def scope_to_list(scope: str) -> List[str]:
"""Convert a scope string to a list of scope tokens"""
return scope.strip().split(" ")
class PrivateKeyJWTWithKid(PrivateKeyJWT):
"""An implementation of the private_key_jwt client auth method that includes a kid header.
This is needed because some providers (Keycloak) require the kid header to figure
out which key to use to verify the signature.
"""
def sign(self, auth: Any, token_endpoint: str) -> bytes:
return private_key_jwt_sign(
auth.client_secret,
client_id=auth.client_id,
token_endpoint=token_endpoint,
claims=self.claims,
header={"kid": auth.client_secret["kid"]},
)
class OAuthDelegatedAuth(BaseAuth):
AUTH_METHODS = {
"client_secret_post": encode_client_secret_post,
"client_secret_basic": encode_client_secret_basic,
"client_secret_jwt": ClientSecretJWT(),
"private_key_jwt": PrivateKeyJWTWithKid(),
}
def __init__(self, hs: "HomeServer"):
super().__init__(hs)
self._config = hs.config.auth
assert self._config.oauth_delegation_enabled, "OAuth delegation is not enabled"
assert self._config.oauth_delegation_issuer, "No issuer provided"
assert self._config.oauth_delegation_client_id, "No client_id provided"
assert self._config.oauth_delegation_client_secret, "No client_secret provided"
assert (
self._config.oauth_delegation_client_auth_method
in OAuthDelegatedAuth.AUTH_METHODS
), "Invalid client_auth_method"
self._http_client = hs.get_proxied_http_client()
self._hostname = hs.hostname
self._issuer_metadata = RetryOnExceptionCachedCall(self._load_metadata)
secret = self._config.oauth_delegation_client_secret
self._client_auth = ClientAuth(
self._config.oauth_delegation_client_id,
secret,
OAuthDelegatedAuth.AUTH_METHODS[
self._config.oauth_delegation_client_auth_method
],
)
async def _load_metadata(self) -> OpenIDProviderMetadata:
if self._config.oauth_delegation_issuer_metadata is not None:
return OpenIDProviderMetadata(
**self._config.oauth_delegation_issuer_metadata
)
url = get_well_known_url(self._config.oauth_delegation_issuer, external=True)
response = await self._http_client.get_json(url)
metadata = OpenIDProviderMetadata(**response)
# metadata.validate_introspection_endpoint()
return metadata
async def _introspect_token(self, token: str) -> IntrospectionToken:
metadata = await self._issuer_metadata.get()
introspection_endpoint = metadata.get("introspection_endpoint")
raw_headers: Dict[str, str] = {
"Content-Type": "application/x-www-form-urlencoded",
"User-Agent": str(self._http_client.user_agent, "utf-8"),
"Accept": "application/json",
}
args = {"token": token, "token_type_hint": "access_token"}
body = urlencode(args, True)
# Fill the body/headers with credentials
uri, raw_headers, body = self._client_auth.prepare(
method="POST", uri=introspection_endpoint, headers=raw_headers, body=body
)
headers = Headers({k: [v] for (k, v) in raw_headers.items()})
# Do the actual request
# We're not using the SimpleHttpClient util methods as we don't want to
# check the HTTP status code and we do the body encoding ourself.
response = await self._http_client.request(
method="POST",
uri=uri,
data=body.encode("utf-8"),
headers=headers,
)
resp_body = await make_deferred_yieldable(readBody(response))
# TODO: Let's not worry about 5xx errors & co. for now and just try
# decoding that as JSON. We should also do some validation of the
# response
resp = json_decoder.decode(resp_body.decode("utf-8"))
return IntrospectionToken(**resp)
async def is_server_admin(self, requester: Requester) -> bool:
return "urn:synapse:admin:*" in requester.scope
async def get_user_by_req(
self,
request: SynapseRequest,
allow_guest: bool = False,
allow_expired: bool = False,
) -> Requester:
access_token = self.get_access_token_from_request(request)
return await self.get_user_by_access_token(access_token, allow_expired)
async def get_user_by_access_token(
self,
token: str,
allow_expired: bool = False,
) -> Requester:
introspection_result = await self._introspect_token(token)
logger.info(f"Introspection result: {introspection_result!r}")
# TODO: introspection verification should be more extensive, especially:
# - verify the scopes
# - verify the audience
if not introspection_result.get("active"):
raise AuthError(
403,
"Invalid access token",
)
# TODO: claim mapping should be configurable
username: Optional[str] = introspection_result.get("username")
if username is None or not isinstance(username, str):
raise AuthError(
500,
"Invalid username claim in the introspection result",
)
# Let's look at the scope
scope: List[str] = scope_to_list(introspection_result.get("scope", ""))
device_id = None
# Find device_id in scope
for tok in scope:
if tok.startswith("urn:matrix:org.matrix.msc2967.client:device:"):
parts = tok.split(":")
if len(parts) == 5:
device_id = parts[4]
user_id = UserID(username, self._hostname)
user_info = await self.store.get_userinfo_by_id(user_id=user_id.to_string())
# If the user does not exist, we should create it on the fly
# TODO: we could use SCIM to provision users ahead of time and listen
# for SCIM SET events if those ever become standard:
# https://datatracker.ietf.org/doc/html/draft-hunt-scim-notify-00
if not user_info:
await self.store.register_user(user_id=user_id.to_string())
user_info = await self.store.get_userinfo_by_id(user_id=user_id.to_string())
if not user_info:
raise AuthError(
500,
"Could not create user on the fly",
)
if device_id:
# Create the device on the fly if it does not exist
try:
await self.store.get_device(
user_id=user_id.to_string(), device_id=device_id
)
except StoreError:
await self.store.store_device(
user_id=user_id.to_string(),
device_id=device_id,
initial_device_display_name="OIDC-native client",
)
# TODO: there is a few things missing in the requester here, which still need
# to be figured out, like:
# - impersonation, with the `authenticated_entity`, which is used for
# rate-limiting, MAU limits, etc.
# - shadow-banning, with the `shadow_banned` flag
# - a proper solution for appservices, which still needs to be figured out in
# the context of MSC3861
return create_requester(
user_id=user_id,
device_id=device_id,
scope=scope,
)
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