278 lines
11 KiB
Python
278 lines
11 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 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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InvalidClientTokenError,
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OAuthInsufficientScopeError,
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StoreError,
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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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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):
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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 OAuthDelegatedAuth(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.auth
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assert self._config.oauth_delegation_enabled, "OAuth delegation is not enabled"
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assert self._config.oauth_delegation_issuer, "No issuer provided"
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assert self._config.oauth_delegation_client_id, "No client_id provided"
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assert self._config.oauth_delegation_client_secret, "No client_secret provided"
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assert (
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self._config.oauth_delegation_client_auth_method
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in OAuthDelegatedAuth.AUTH_METHODS
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), "Invalid client_auth_method"
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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._issuer_metadata = RetryOnExceptionCachedCall(self._load_metadata)
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secret = self._config.oauth_delegation_client_secret
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self._client_auth = ClientAuth(
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self._config.oauth_delegation_client_id,
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secret,
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OAuthDelegatedAuth.AUTH_METHODS[
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self._config.oauth_delegation_client_auth_method
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],
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)
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async def _load_metadata(self) -> OpenIDProviderMetadata:
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if self._config.oauth_delegation_issuer_metadata is not None:
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return OpenIDProviderMetadata(
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**self._config.oauth_delegation_issuer_metadata
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)
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url = get_well_known_url(self._config.oauth_delegation_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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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 ourself.
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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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# TODO: Let's not worry about 5xx errors & co. for now and just try
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# decoding that as JSON. We should also do some validation of the
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# response
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resp = json_decoder.decode(resp_body.decode("utf-8"))
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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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) -> Requester:
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access_token = self.get_access_token_from_request(request)
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# TODO: we probably want to assert the allow_guest inside this call 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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if not allow_guest and requester.is_guest:
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raise OAuthInsufficientScopeError(
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["urn:matrix:org.matrix.msc2967.client:api:*"]
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)
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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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introspection_result = await self._introspect_token(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_admin_scope = "urn:synapse:admin:*" in scope
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has_user_scope = "urn:matrix:org.matrix.msc2967.client:api:*" in scope
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has_guest_scope = "urn:matrix:org.matrix.msc2967.client:api:guest" in scope
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is_user = has_user_scope or has_admin_scope
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is_guest = has_guest_scope and not is_user
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if not is_user and not is_guest:
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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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OAuthDelegatedAuth.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_userinfo_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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OAuthDelegatedAuth.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_id in scope
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device_id = None
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for tok in scope:
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if tok.startswith("urn:matrix:org.matrix.msc2967.client:device:"):
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parts = tok.split(":")
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if len(parts) == 5:
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device_id = parts[4]
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if device_id:
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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=is_guest,
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)
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