import hashlib import json import random import secrets from base64 import b32encode from typing import Dict from urllib.parse import quote, urlencode, urljoin import requests from defusedxml import ElementTree from django.conf import settings from django.core.signing import Signer from django.http import HttpRequest, HttpResponse from django.middleware import csrf from django.shortcuts import redirect, render from django.utils.crypto import constant_time_compare, salted_hmac from django.utils.translation import gettext as _ from django.views.decorators.cache import never_cache from django.views.decorators.csrf import csrf_exempt from django.views.decorators.http import require_POST from oauthlib.oauth2 import OAuth2Error from requests_oauthlib import OAuth2Session from returns.curry import partial from zerver.actions.video_calls import do_set_zoom_token from zerver.decorator import zulip_login_required from zerver.lib.exceptions import ErrorCode, JsonableError from zerver.lib.outgoing_http import OutgoingSession from zerver.lib.pysa import mark_sanitized from zerver.lib.request import REQ, has_request_variables from zerver.lib.response import json_success from zerver.lib.subdomains import get_subdomain from zerver.lib.url_encoding import append_url_query_string from zerver.lib.validator import check_bool, check_dict, check_string from zerver.models import UserProfile, get_realm class VideoCallSession(OutgoingSession): def __init__(self) -> None: super().__init__(role="video_calls", timeout=5) class InvalidZoomTokenError(JsonableError): code = ErrorCode.INVALID_ZOOM_TOKEN def __init__(self) -> None: super().__init__(_("Invalid Zoom access token")) def get_zoom_session(user: UserProfile) -> OAuth2Session: if settings.VIDEO_ZOOM_CLIENT_ID is None: raise JsonableError(_("Zoom credentials have not been configured")) client_id = settings.VIDEO_ZOOM_CLIENT_ID client_secret = settings.VIDEO_ZOOM_CLIENT_SECRET return OAuth2Session( client_id, redirect_uri=urljoin(settings.ROOT_DOMAIN_URI, "/calls/zoom/complete"), auto_refresh_url="https://zoom.us/oauth/token", auto_refresh_kwargs={ "client_id": client_id, "client_secret": client_secret, }, token=user.zoom_token, token_updater=partial(do_set_zoom_token, user), ) def get_zoom_sid(request: HttpRequest) -> str: # This is used to prevent CSRF attacks on the Zoom OAuth # authentication flow. We want this value to be unpredictable and # tied to the session, but we don’t want to expose the main CSRF # token directly to the Zoom server. csrf.get_token(request) # Use 'mark_sanitized' to cause Pysa to ignore the flow of user controlled # data out of this function. 'request.META' is indeed user controlled, but # post-HMAC output is no longer meaningfully controllable. return mark_sanitized( "" if getattr(request, "_dont_enforce_csrf_checks", False) else salted_hmac("Zulip Zoom sid", request.META["CSRF_COOKIE"]).hexdigest() ) @zulip_login_required @never_cache def register_zoom_user(request: HttpRequest) -> HttpResponse: assert request.user.is_authenticated oauth = get_zoom_session(request.user) authorization_url, state = oauth.authorization_url( "https://zoom.us/oauth/authorize", state=json.dumps( {"realm": get_subdomain(request), "sid": get_zoom_sid(request)}, ), ) return redirect(authorization_url) @never_cache @has_request_variables def complete_zoom_user( request: HttpRequest, state: Dict[str, str] = REQ( json_validator=check_dict([("realm", check_string)], value_validator=check_string) ), ) -> HttpResponse: if get_subdomain(request) != state["realm"]: return redirect(urljoin(get_realm(state["realm"]).uri, request.get_full_path())) return complete_zoom_user_in_realm(request) @zulip_login_required @has_request_variables def complete_zoom_user_in_realm( request: HttpRequest, code: str = REQ(), state: Dict[str, str] = REQ( json_validator=check_dict([("sid", check_string)], value_validator=check_string) ), ) -> HttpResponse: assert request.user.is_authenticated if not constant_time_compare(state["sid"], get_zoom_sid(request)): raise JsonableError(_("Invalid Zoom session identifier")) client_secret = settings.VIDEO_ZOOM_CLIENT_SECRET oauth = get_zoom_session(request.user) try: token = oauth.fetch_token( "https://zoom.us/oauth/token", code=code, client_secret=client_secret, ) except OAuth2Error: raise JsonableError(_("Invalid Zoom credentials")) do_set_zoom_token(request.user, token) return render(request, "zerver/close_window.html") @has_request_variables def make_zoom_video_call( request: HttpRequest, user: UserProfile, is_video_call: bool = REQ(json_validator=check_bool, default=True), ) -> HttpResponse: oauth = get_zoom_session(user) if not oauth.authorized: raise InvalidZoomTokenError # The meeting host has the ability to configure both their own and # participants' default video on/off state for the meeting. That's # why when creating a meeting, configure the video on/off default # according to the desired call type. Each Zoom user can still have # their own personal setting to not start video by default. payload = { "settings": { "host_video": is_video_call, "participant_video": is_video_call, } } try: res = oauth.post("https://api.zoom.us/v2/users/me/meetings", json=payload) except OAuth2Error: do_set_zoom_token(user, None) raise InvalidZoomTokenError if res.status_code == 401: do_set_zoom_token(user, None) raise InvalidZoomTokenError elif not res.ok: raise JsonableError(_("Failed to create Zoom call")) return json_success(request, data={"url": res.json()["join_url"]}) @csrf_exempt @require_POST @has_request_variables def deauthorize_zoom_user(request: HttpRequest) -> HttpResponse: return json_success(request) @has_request_variables def get_bigbluebutton_url( request: HttpRequest, user_profile: UserProfile, meeting_name: str = REQ() ) -> HttpResponse: # https://docs.bigbluebutton.org/dev/api.html#create for reference on the API calls # https://docs.bigbluebutton.org/dev/api.html#usage for reference for checksum id = "zulip-" + str(random.randint(100000000000, 999999999999)) password = b32encode(secrets.token_bytes(20)).decode() # 20 bytes means 32 characters # We sign our data here to ensure a Zulip user can not tamper with # the join link to gain access to other meetings that are on the # same bigbluebutton server. signed = Signer().sign_object( { "meeting_id": id, "name": meeting_name, "password": password, } ) url = append_url_query_string("/calls/bigbluebutton/join", "bigbluebutton=" + signed) return json_success(request, {"url": url}) # We use zulip_login_required here mainly to get access to the user's # full name from Zulip to prepopulate the user's name in the # BigBlueButton meeting. Since the meeting's details are encoded in # the link the user is clicking, there is no validation tying this # meeting to the Zulip organization it was created in. @zulip_login_required @never_cache @has_request_variables def join_bigbluebutton(request: HttpRequest, bigbluebutton: str = REQ()) -> HttpResponse: assert request.user.is_authenticated if settings.BIG_BLUE_BUTTON_URL is None or settings.BIG_BLUE_BUTTON_SECRET is None: raise JsonableError(_("BigBlueButton is not configured.")) try: bigbluebutton_data = Signer().unsign_object(bigbluebutton) except Exception: raise JsonableError(_("Invalid signature.")) create_params = urlencode( { "meetingID": bigbluebutton_data["meeting_id"], "name": bigbluebutton_data["name"], "moderatorPW": bigbluebutton_data["password"], # We generate the attendee password from moderatorPW, # because the BigBlueButton API requires a separate # password. This integration is designed to have all users # join as moderators, so we generate attendeePW by # truncating the moderatorPW while keeping it long enough # to not be vulnerable to brute force attacks. "attendeePW": bigbluebutton_data["password"][:16], }, quote_via=quote, ) checksum = hashlib.sha256( ("create" + create_params + settings.BIG_BLUE_BUTTON_SECRET).encode() ).hexdigest() try: response = VideoCallSession().get( append_url_query_string(settings.BIG_BLUE_BUTTON_URL + "api/create", create_params) + "&checksum=" + checksum ) response.raise_for_status() except requests.RequestException: raise JsonableError(_("Error connecting to the BigBlueButton server.")) payload = ElementTree.fromstring(response.text) if payload.find("messageKey").text == "checksumError": raise JsonableError(_("Error authenticating to the BigBlueButton server.")) if payload.find("returncode").text != "SUCCESS": raise JsonableError(_("BigBlueButton server returned an unexpected error.")) join_params = urlencode( { "meetingID": bigbluebutton_data["meeting_id"], # We use the moderator password here to grant ever user # full moderator permissions to the bigbluebutton session. "password": bigbluebutton_data["password"], "fullName": request.user.full_name, # https://docs.bigbluebutton.org/dev/api.html#create # The createTime option is used to have the user redirected to a link # that is only valid for this meeting. # # Even if the same link in Zulip is used again, a new # createTime parameter will be created, as the meeting on # the BigBlueButton server has to be recreated. (after a # few minutes) "createTime": payload.find("createTime").text, }, quote_via=quote, ) checksum = hashlib.sha256( ("join" + join_params + settings.BIG_BLUE_BUTTON_SECRET).encode() ).hexdigest() redirect_url_base = append_url_query_string( settings.BIG_BLUE_BUTTON_URL + "api/join", join_params ) return redirect(append_url_query_string(redirect_url_base, "checksum=" + checksum))