379 lines
15 KiB
Python
379 lines
15 KiB
Python
# Copyright 2023 The Matrix.org Foundation.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from typing import TYPE_CHECKING, Any, Dict, List, Optional
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from urllib.parse import urlencode
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from authlib.oauth2 import ClientAuth
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from authlib.oauth2.auth import encode_client_secret_basic, encode_client_secret_post
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from authlib.oauth2.rfc7523 import ClientSecretJWT, PrivateKeyJWT, private_key_jwt_sign
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from authlib.oauth2.rfc7662 import IntrospectionToken
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from authlib.oidc.discovery import OpenIDProviderMetadata, get_well_known_url
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from prometheus_client import Histogram
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from twisted.web.client import readBody
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from twisted.web.http_headers import Headers
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from synapse.api.auth.base import BaseAuth
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from synapse.api.errors import (
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AuthError,
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HttpResponseException,
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InvalidClientTokenError,
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OAuthInsufficientScopeError,
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StoreError,
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SynapseError,
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)
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from synapse.http.site import SynapseRequest
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from synapse.logging.context import make_deferred_yieldable
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from synapse.types import Requester, UserID, create_requester
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from synapse.util import json_decoder
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from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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introspection_response_timer = Histogram(
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"synapse_api_auth_delegated_introspection_response",
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"Time taken to get a response for an introspection request",
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["code"],
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)
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# Scope as defined by MSC2967
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# https://github.com/matrix-org/matrix-spec-proposals/pull/2967
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SCOPE_MATRIX_API = "urn:matrix:org.matrix.msc2967.client:api:*"
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SCOPE_MATRIX_GUEST = "urn:matrix:org.matrix.msc2967.client:api:guest"
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SCOPE_MATRIX_DEVICE_PREFIX = "urn:matrix:org.matrix.msc2967.client:device:"
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# Scope which allows access to the Synapse admin API
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SCOPE_SYNAPSE_ADMIN = "urn:synapse:admin:*"
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def scope_to_list(scope: str) -> List[str]:
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"""Convert a scope string to a list of scope tokens"""
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return scope.strip().split(" ")
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class PrivateKeyJWTWithKid(PrivateKeyJWT): # type: ignore[misc]
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"""An implementation of the private_key_jwt client auth method that includes a kid header.
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This is needed because some providers (Keycloak) require the kid header to figure
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out which key to use to verify the signature.
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"""
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def sign(self, auth: Any, token_endpoint: str) -> bytes:
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return private_key_jwt_sign(
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auth.client_secret,
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client_id=auth.client_id,
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token_endpoint=token_endpoint,
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claims=self.claims,
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header={"kid": auth.client_secret["kid"]},
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)
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class MSC3861DelegatedAuth(BaseAuth):
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AUTH_METHODS = {
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"client_secret_post": encode_client_secret_post,
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"client_secret_basic": encode_client_secret_basic,
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"client_secret_jwt": ClientSecretJWT(),
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"private_key_jwt": PrivateKeyJWTWithKid(),
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}
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EXTERNAL_ID_PROVIDER = "oauth-delegated"
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def __init__(self, hs: "HomeServer"):
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super().__init__(hs)
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self._config = hs.config.experimental.msc3861
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auth_method = MSC3861DelegatedAuth.AUTH_METHODS.get(
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self._config.client_auth_method.value, None
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)
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# Those assertions are already checked when parsing the config
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assert self._config.enabled, "OAuth delegation is not enabled"
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assert self._config.issuer, "No issuer provided"
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assert self._config.client_id, "No client_id provided"
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assert auth_method is not None, "Invalid client_auth_method provided"
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self._clock = hs.get_clock()
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self._http_client = hs.get_proxied_http_client()
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self._hostname = hs.hostname
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self._admin_token = self._config.admin_token
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self._issuer_metadata = RetryOnExceptionCachedCall(self._load_metadata)
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if isinstance(auth_method, PrivateKeyJWTWithKid):
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# Use the JWK as the client secret when using the private_key_jwt method
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assert self._config.jwk, "No JWK provided"
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self._client_auth = ClientAuth(
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self._config.client_id, self._config.jwk, auth_method
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)
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else:
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# Else use the client secret
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assert self._config.client_secret, "No client_secret provided"
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self._client_auth = ClientAuth(
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self._config.client_id, self._config.client_secret, auth_method
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)
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async def _load_metadata(self) -> OpenIDProviderMetadata:
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if self._config.issuer_metadata is not None:
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return OpenIDProviderMetadata(**self._config.issuer_metadata)
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url = get_well_known_url(self._config.issuer, external=True)
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response = await self._http_client.get_json(url)
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metadata = OpenIDProviderMetadata(**response)
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# metadata.validate_introspection_endpoint()
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return metadata
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async def _introspect_token(self, token: str) -> IntrospectionToken:
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"""
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Send a token to the introspection endpoint and returns the introspection response
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Parameters:
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token: The token to introspect
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Raises:
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HttpResponseException: If the introspection endpoint returns a non-2xx response
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ValueError: If the introspection endpoint returns an invalid JSON response
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JSONDecodeError: If the introspection endpoint returns a non-JSON response
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Exception: If the HTTP request fails
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Returns:
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The introspection response
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"""
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metadata = await self._issuer_metadata.get()
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introspection_endpoint = metadata.get("introspection_endpoint")
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raw_headers: Dict[str, str] = {
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"Content-Type": "application/x-www-form-urlencoded",
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"User-Agent": str(self._http_client.user_agent, "utf-8"),
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"Accept": "application/json",
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}
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args = {"token": token, "token_type_hint": "access_token"}
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body = urlencode(args, True)
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# Fill the body/headers with credentials
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uri, raw_headers, body = self._client_auth.prepare(
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method="POST", uri=introspection_endpoint, headers=raw_headers, body=body
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)
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headers = Headers({k: [v] for (k, v) in raw_headers.items()})
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# Do the actual request
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# We're not using the SimpleHttpClient util methods as we don't want to
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# check the HTTP status code, and we do the body encoding ourselves.
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start_time = self._clock.time()
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try:
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response = await self._http_client.request(
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method="POST",
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uri=uri,
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data=body.encode("utf-8"),
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headers=headers,
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)
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resp_body = await make_deferred_yieldable(readBody(response))
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except Exception:
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end_time = self._clock.time()
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introspection_response_timer.labels("ERR").observe(end_time - start_time)
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raise
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end_time = self._clock.time()
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introspection_response_timer.labels(response.code).observe(
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end_time - start_time
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)
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if response.code < 200 or response.code >= 300:
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raise HttpResponseException(
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response.code,
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response.phrase.decode("ascii", errors="replace"),
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resp_body,
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)
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resp = json_decoder.decode(resp_body.decode("utf-8"))
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if not isinstance(resp, dict):
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raise ValueError(
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"The introspection endpoint returned an invalid JSON response."
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)
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return IntrospectionToken(**resp)
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async def is_server_admin(self, requester: Requester) -> bool:
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return "urn:synapse:admin:*" in requester.scope
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async def get_user_by_req(
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self,
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request: SynapseRequest,
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allow_guest: bool = False,
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allow_expired: bool = False,
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allow_locked: bool = False,
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) -> Requester:
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access_token = self.get_access_token_from_request(request)
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requester = await self.get_appservice_user(request, access_token)
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if not requester:
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# TODO: we probably want to assert the allow_guest inside this call
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# so that we don't provision the user if they don't have enough permission:
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requester = await self.get_user_by_access_token(access_token, allow_expired)
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# Do not record requests from MAS using the virtual `__oidc_admin` user.
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if access_token != self._admin_token:
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await self._record_request(request, requester)
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if not allow_guest and requester.is_guest:
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raise OAuthInsufficientScopeError([SCOPE_MATRIX_API])
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request.requester = requester
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return requester
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async def get_user_by_access_token(
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self,
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token: str,
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allow_expired: bool = False,
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) -> Requester:
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if self._admin_token is not None and token == self._admin_token:
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# XXX: This is a temporary solution so that the admin API can be called by
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# the OIDC provider. This will be removed once we have OIDC client
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# credentials grant support in matrix-authentication-service.
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logging.info("Admin toked used")
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# XXX: that user doesn't exist and won't be provisioned.
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# This is mostly fine for admin calls, but we should also think about doing
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# requesters without a user_id.
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admin_user = UserID("__oidc_admin", self._hostname)
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return create_requester(
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user_id=admin_user,
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scope=["urn:synapse:admin:*"],
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)
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try:
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introspection_result = await self._introspect_token(token)
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except Exception:
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logger.exception("Failed to introspect token")
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raise SynapseError(503, "Unable to introspect the access token")
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logger.info(f"Introspection result: {introspection_result!r}")
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# TODO: introspection verification should be more extensive, especially:
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# - verify the audience
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if not introspection_result.get("active"):
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raise InvalidClientTokenError("Token is not active")
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# Let's look at the scope
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scope: List[str] = scope_to_list(introspection_result.get("scope", ""))
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# Determine type of user based on presence of particular scopes
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has_user_scope = SCOPE_MATRIX_API in scope
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has_guest_scope = SCOPE_MATRIX_GUEST in scope
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if not has_user_scope and not has_guest_scope:
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raise InvalidClientTokenError("No scope in token granting user rights")
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# Match via the sub claim
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sub: Optional[str] = introspection_result.get("sub")
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if sub is None:
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raise InvalidClientTokenError(
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"Invalid sub claim in the introspection result"
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)
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user_id_str = await self.store.get_user_by_external_id(
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MSC3861DelegatedAuth.EXTERNAL_ID_PROVIDER, sub
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)
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if user_id_str is None:
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# If we could not find a user via the external_id, it either does not exist,
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# or the external_id was never recorded
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# TODO: claim mapping should be configurable
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username: Optional[str] = introspection_result.get("username")
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if username is None or not isinstance(username, str):
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raise AuthError(
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500,
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"Invalid username claim in the introspection result",
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)
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user_id = UserID(username, self._hostname)
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# First try to find a user from the username claim
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user_info = await self.store.get_user_by_id(user_id=user_id.to_string())
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if user_info is None:
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# If the user does not exist, we should create it on the fly
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# TODO: we could use SCIM to provision users ahead of time and listen
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# for SCIM SET events if those ever become standard:
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# https://datatracker.ietf.org/doc/html/draft-hunt-scim-notify-00
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# TODO: claim mapping should be configurable
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# If present, use the name claim as the displayname
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name: Optional[str] = introspection_result.get("name")
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await self.store.register_user(
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user_id=user_id.to_string(), create_profile_with_displayname=name
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)
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# And record the sub as external_id
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await self.store.record_user_external_id(
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MSC3861DelegatedAuth.EXTERNAL_ID_PROVIDER, sub, user_id.to_string()
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)
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else:
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user_id = UserID.from_string(user_id_str)
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# Find device_ids in scope
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# We only allow a single device_id in the scope, so we find them all in the
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# scope list, and raise if there are more than one. The OIDC server should be
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# the one enforcing valid scopes, so we raise a 500 if we find an invalid scope.
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device_ids = [
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tok[len(SCOPE_MATRIX_DEVICE_PREFIX) :]
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for tok in scope
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if tok.startswith(SCOPE_MATRIX_DEVICE_PREFIX)
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]
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if len(device_ids) > 1:
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raise AuthError(
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500,
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"Multiple device IDs in scope",
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)
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device_id = device_ids[0] if device_ids else None
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if device_id is not None:
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# Sanity check the device_id
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if len(device_id) > 255 or len(device_id) < 1:
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raise AuthError(
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500,
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"Invalid device ID in scope",
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)
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# Create the device on the fly if it does not exist
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try:
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await self.store.get_device(
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user_id=user_id.to_string(), device_id=device_id
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)
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except StoreError:
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await self.store.store_device(
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user_id=user_id.to_string(),
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device_id=device_id,
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initial_device_display_name="OIDC-native client",
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)
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# TODO: there is a few things missing in the requester here, which still need
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# to be figured out, like:
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# - impersonation, with the `authenticated_entity`, which is used for
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# rate-limiting, MAU limits, etc.
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# - shadow-banning, with the `shadow_banned` flag
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# - a proper solution for appservices, which still needs to be figured out in
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# the context of MSC3861
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return create_requester(
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user_id=user_id,
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device_id=device_id,
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scope=scope,
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is_guest=(has_guest_scope and not has_user_scope),
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)
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