element-call/src/e2ee/sharedKeyManagement.ts

/*
Copyright 2023, 2024 New Vector Ltd.

SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE in the repository root for full details.
*/

import { useEffect, useMemo } from "react";

import { setLocalStorageItem, useLocalStorage } from "../useLocalStorage";
import { type UrlParams, getUrlParams, useUrlParams } from "../UrlParams";
import { E2eeType } from "./e2eeType";
import { useClient } from "../ClientContext";

export function saveKeyForRoom(roomId: string, password: string): void {
  setLocalStorageItem(getRoomSharedKeyLocalStorageKey(roomId), password);
}

const getRoomSharedKeyLocalStorageKey = (roomId: string): string =>
  `room-shared-key-${roomId}`;

const useInternalRoomSharedKey = (roomId: string): string | null => {
  const key = getRoomSharedKeyLocalStorageKey(roomId);
  const [roomSharedKey] = useLocalStorage(key);

  return roomSharedKey;
};

export function getKeyForRoom(roomId: string): string | null {
  saveKeyFromUrlParams(getUrlParams());
  const key = getRoomSharedKeyLocalStorageKey(roomId);
  return localStorage.getItem(key);
}

function saveKeyFromUrlParams(urlParams: UrlParams): void {
  if (!urlParams.password || !urlParams.roomId) return;

  // Take the key from the URL and save it.
  // It's important to always use the room ID specified in the URL
  // when saving keys rather than whatever the current room ID might be,
  // in case we've moved to a different room but the URL hasn't changed.
  saveKeyForRoom(urlParams.roomId, urlParams.password);
}

/**
 * Extracts the room password from the URL if one is present, saving it in localstorage
 * and returning it in a tuple with the corresponding room ID from the URL.
 * @returns A tuple of the roomId and password from the URL if the URL has both,
 *          otherwise [undefined, undefined]
 */
const useKeyFromUrl = (): [string, string] | [undefined, undefined] => {
  const urlParams = useUrlParams();

  useEffect(() => saveKeyFromUrlParams(urlParams), [urlParams]);

  return urlParams.roomId && urlParams.password
    ? [urlParams.roomId, urlParams.password]
    : [undefined, undefined];
};

export type Unencrypted = { kind: E2eeType.NONE };
export type SharedSecret = { kind: E2eeType.SHARED_KEY; secret: string };
export type PerParticipantE2EE = { kind: E2eeType.PER_PARTICIPANT };
export type EncryptionSystem = Unencrypted | SharedSecret | PerParticipantE2EE;

export function useRoomEncryptionSystem(roomId: string): EncryptionSystem {
  const { client } = useClient();

  // make sure we've extracted the key from the URL first
  // (and we still need to take the value it returns because
  // the effect won't run in time for it to save to localstorage in
  // time for us to read it out again).
  const [urlRoomId, passwordFromUrl] = useKeyFromUrl();
  const storedPassword = useInternalRoomSharedKey(roomId);
  const room = client?.getRoom(roomId);
  const e2eeSystem = <EncryptionSystem>useMemo(() => {
    if (!room) return { kind: E2eeType.NONE };
    if (storedPassword)
      return {
        kind: E2eeType.SHARED_KEY,
        secret: storedPassword,
      };
    if (urlRoomId === roomId)
      return {
        kind: E2eeType.SHARED_KEY,
        secret: passwordFromUrl,
      };
    if (room.hasEncryptionStateEvent()) {
      return { kind: E2eeType.PER_PARTICIPANT };
    }
    return { kind: E2eeType.NONE };
  }, [passwordFromUrl, room, roomId, storedPassword, urlRoomId]);
  return e2eeSystem;
}