421 lines
15 KiB
Python
421 lines
15 KiB
Python
# Copyright 2017, 2018 New Vector Ltd
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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, Optional, Tuple, cast
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from synapse.api.errors import Codes, NotFoundError, SynapseError
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from synapse.http.server import HttpServer
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from synapse.http.servlet import (
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RestServlet,
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parse_json_object_from_request,
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parse_string,
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)
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from synapse.http.site import SynapseRequest
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from synapse.types import JsonDict
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from ._base import client_patterns
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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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class RoomKeysServlet(RestServlet):
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PATTERNS = client_patterns(
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"/room_keys/keys(/(?P<room_id>[^/]+))?(/(?P<session_id>[^/]+))?$"
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)
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CATEGORY = "Encryption requests"
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def __init__(self, hs: "HomeServer"):
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super().__init__()
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self.auth = hs.get_auth()
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self.e2e_room_keys_handler = hs.get_e2e_room_keys_handler()
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async def on_PUT(
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self, request: SynapseRequest, room_id: Optional[str], session_id: Optional[str]
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) -> Tuple[int, JsonDict]:
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"""
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Uploads one or more encrypted E2E room keys for backup purposes.
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room_id: the ID of the room the keys are for (optional)
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session_id: the ID for the E2E room keys for the room (optional)
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version: the version of the user's backup which this data is for.
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the version must already have been created via the /room_keys/version API.
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Each session has:
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* first_message_index: a numeric index indicating the oldest message
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encrypted by this session.
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* forwarded_count: how many times the uploading client claims this key
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has been shared (forwarded)
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* is_verified: whether the client that uploaded the keys claims they
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were sent by a device which they've verified
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* session_data: base64-encrypted data describing the session.
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Returns 200 OK on success with body {}
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Returns 403 Forbidden if the version in question is not the most recently
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created version (i.e. if this is an old client trying to write to a stale backup)
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Returns 404 Not Found if the version in question doesn't exist
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The API is designed to be otherwise agnostic to the room_key encryption
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algorithm being used. Sessions are merged with existing ones in the
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backup using the heuristics:
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* is_verified sessions always win over unverified sessions
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* older first_message_index always win over newer sessions
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* lower forwarded_count always wins over higher forwarded_count
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We trust the clients not to lie and corrupt their own backups.
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It also means that if your access_token is stolen, the attacker could
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delete your backup.
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POST /room_keys/keys/!abc:matrix.org/c0ff33?version=1 HTTP/1.1
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Content-Type: application/json
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{
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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Or...
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POST /room_keys/keys/!abc:matrix.org?version=1 HTTP/1.1
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Content-Type: application/json
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{
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"sessions": {
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"c0ff33": {
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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}
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}
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Or...
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POST /room_keys/keys?version=1 HTTP/1.1
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Content-Type: application/json
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{
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"rooms": {
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"!abc:matrix.org": {
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"sessions": {
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"c0ff33": {
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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}
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}
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}
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}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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body = parse_json_object_from_request(request)
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version = parse_string(request, "version", required=True)
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if session_id:
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body = {"sessions": {session_id: body}}
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if room_id:
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body = {"rooms": {room_id: body}}
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ret = await self.e2e_room_keys_handler.upload_room_keys(user_id, version, body)
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return 200, ret
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async def on_GET(
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self, request: SynapseRequest, room_id: Optional[str], session_id: Optional[str]
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) -> Tuple[int, JsonDict]:
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"""
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Retrieves one or more encrypted E2E room keys for backup purposes.
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Symmetric with the PUT version of the API.
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room_id: the ID of the room to retrieve the keys for (optional)
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session_id: the ID for the E2E room keys to retrieve the keys for (optional)
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version: the version of the user's backup which this data is for.
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the version must already have been created via the /change_secret API.
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Returns as follows:
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GET /room_keys/keys/!abc:matrix.org/c0ff33?version=1 HTTP/1.1
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{
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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Or...
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GET /room_keys/keys/!abc:matrix.org?version=1 HTTP/1.1
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{
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"sessions": {
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"c0ff33": {
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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}
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}
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Or...
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GET /room_keys/keys?version=1 HTTP/1.1
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{
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"rooms": {
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"!abc:matrix.org": {
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"sessions": {
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"c0ff33": {
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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}
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}
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}
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}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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version = parse_string(request, "version", required=True)
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room_keys = cast(
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JsonDict,
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await self.e2e_room_keys_handler.get_room_keys(
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user_id, version, room_id, session_id
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),
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)
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# Convert room_keys to the right format to return.
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if session_id:
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# If the client requests a specific session, but that session was
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# not backed up, then return an M_NOT_FOUND.
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if room_keys["rooms"] == {}:
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raise NotFoundError("No room_keys found")
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else:
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room_keys = room_keys["rooms"][room_id]["sessions"][session_id]
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elif room_id:
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# If the client requests all sessions from a room, but no sessions
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# are found, then return an empty result rather than an error, so
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# that clients don't have to handle an error condition, and an
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# empty result is valid. (Similarly if the client requests all
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# sessions from the backup, but in that case, room_keys is already
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# in the right format, so we don't need to do anything about it.)
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if room_keys["rooms"] == {}:
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room_keys = {"sessions": {}}
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else:
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room_keys = room_keys["rooms"][room_id]
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return 200, room_keys
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async def on_DELETE(
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self, request: SynapseRequest, room_id: Optional[str], session_id: Optional[str]
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) -> Tuple[int, JsonDict]:
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"""
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Deletes one or more encrypted E2E room keys for a user for backup purposes.
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DELETE /room_keys/keys/!abc:matrix.org/c0ff33?version=1
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HTTP/1.1 200 OK
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{}
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room_id: the ID of the room whose keys to delete (optional)
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session_id: the ID for the E2E session to delete (optional)
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version: the version of the user's backup which this data is for.
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the version must already have been created via the /change_secret API.
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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version = parse_string(request, "version", required=True)
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ret = await self.e2e_room_keys_handler.delete_room_keys(
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user_id, version, room_id, session_id
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)
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return 200, ret
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class RoomKeysNewVersionServlet(RestServlet):
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PATTERNS = client_patterns("/room_keys/version$")
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CATEGORY = "Encryption requests"
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def __init__(self, hs: "HomeServer"):
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super().__init__()
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self.auth = hs.get_auth()
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self.e2e_room_keys_handler = hs.get_e2e_room_keys_handler()
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async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
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"""
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Retrieve the version information about the most current backup version (if any)
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It takes out an exclusive lock on this user's room_key backups, to ensure
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clients only upload to the current backup.
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Returns 404 if the given version does not exist.
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GET /room_keys/version HTTP/1.1
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{
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"version": "12345",
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"algorithm": "m.megolm_backup.v1",
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"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
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}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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try:
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info = await self.e2e_room_keys_handler.get_version_info(user_id)
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except SynapseError as e:
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if e.code == 404:
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raise SynapseError(404, "No backup found", Codes.NOT_FOUND)
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return 200, info
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async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
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"""
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Create a new backup version for this user's room_keys with the given
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info. The version is allocated by the server and returned to the user
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in the response. This API is intended to be used whenever the user
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changes the encryption key for their backups, ensuring that backups
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encrypted with different keys don't collide.
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It takes out an exclusive lock on this user's room_key backups, to ensure
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clients only upload to the current backup.
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The algorithm passed in the version info is a reverse-DNS namespaced
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identifier to describe the format of the encrypted backupped keys.
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The auth_data is { user_id: "user_id", nonce: <random string> }
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encrypted using the algorithm and current encryption key described above.
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POST /room_keys/version
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Content-Type: application/json
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{
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"algorithm": "m.megolm_backup.v1",
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"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
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}
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HTTP/1.1 200 OK
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Content-Type: application/json
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{
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"version": 12345
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}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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info = parse_json_object_from_request(request)
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new_version = await self.e2e_room_keys_handler.create_version(user_id, info)
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return 200, {"version": new_version}
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# we deliberately don't have a PUT /version, as these things really should
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# be immutable to avoid people footgunning
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class RoomKeysVersionServlet(RestServlet):
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PATTERNS = client_patterns("/room_keys/version/(?P<version>[^/]+)$")
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CATEGORY = "Encryption requests"
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def __init__(self, hs: "HomeServer"):
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super().__init__()
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self.auth = hs.get_auth()
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self.e2e_room_keys_handler = hs.get_e2e_room_keys_handler()
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async def on_GET(
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self, request: SynapseRequest, version: str
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) -> Tuple[int, JsonDict]:
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"""
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Retrieve the version information about a given version of the user's
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room_keys backup.
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It takes out an exclusive lock on this user's room_key backups, to ensure
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clients only upload to the current backup.
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Returns 404 if the given version does not exist.
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GET /room_keys/version/12345 HTTP/1.1
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{
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"version": "12345",
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"algorithm": "m.megolm_backup.v1",
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"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
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}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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try:
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info = await self.e2e_room_keys_handler.get_version_info(user_id, version)
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except SynapseError as e:
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if e.code == 404:
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raise SynapseError(404, "No backup found", Codes.NOT_FOUND)
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return 200, info
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async def on_DELETE(
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self, request: SynapseRequest, version: str
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) -> Tuple[int, JsonDict]:
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"""
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Delete the information about a given version of the user's
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room_keys backup. Doesn't delete the actual room data.
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DELETE /room_keys/version/12345 HTTP/1.1
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HTTP/1.1 200 OK
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{}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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await self.e2e_room_keys_handler.delete_version(user_id, version)
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return 200, {}
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async def on_PUT(
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self, request: SynapseRequest, version: str
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) -> Tuple[int, JsonDict]:
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"""
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Update the information about a given version of the user's room_keys backup.
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POST /room_keys/version/12345 HTTP/1.1
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Content-Type: application/json
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{
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"algorithm": "m.megolm_backup.v1",
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"auth_data": {
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"public_key": "abcdefg",
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"signatures": {
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"ed25519:something": "hijklmnop"
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}
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},
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"version": "12345"
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}
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HTTP/1.1 200 OK
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Content-Type: application/json
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{}
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"""
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requester = await self.auth.get_user_by_req(request, allow_guest=False)
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user_id = requester.user.to_string()
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info = parse_json_object_from_request(request)
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await self.e2e_room_keys_handler.update_version(user_id, version, info)
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return 200, {}
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def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
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RoomKeysServlet(hs).register(http_server)
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RoomKeysVersionServlet(hs).register(http_server)
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RoomKeysNewVersionServlet(hs).register(http_server)
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