signal-desktop/ts/challenge.ts

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// Copyright 2021 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
// `ChallengeHandler` is responsible for:
// 1. tracking the messages that failed to send with 428 error and could be
// retried when user solves the challenge
// 2. presenting the challenge to user and sending the challenge response back
// to the server
//
// The tracked messages are persisted in the database, and are imported back
// to the `ChallengeHandler` on `.load()` call (from `ts/background.ts`). They
// are not immediately retried, however, until `.onOnline()` is called from
// when we are actually online.
import { assertDev } from './util/assert';
import { isOlderThan } from './util/timestamp';
import { parseRetryAfterWithDefault } from './util/parseRetryAfter';
import { clearTimeoutIfNecessary } from './util/clearTimeoutIfNecessary';
import { getEnvironment, Environment } from './environment';
import type { StorageInterface } from './types/Storage.d';
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import * as Errors from './types/errors';
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import { HTTPError } from './textsecure/Errors';
import type { SendMessageChallengeData } from './textsecure/Errors';
import * as log from './logging/log';
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export type ChallengeResponse = Readonly<{
captcha: string;
}>;
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export type IPCRequest = Readonly<{
seq: number;
reason: string;
}>;
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export type IPCResponse = Readonly<{
seq: number;
data: ChallengeResponse;
}>;
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type Handler = Readonly<{
token: string | undefined;
resolve(response: ChallengeResponse): void;
reject(error: Error): void;
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}>;
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export type ChallengeData = Readonly<{
type: 'recaptcha';
token: string;
captcha: string;
}>;
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export type Options = Readonly<{
storage: Pick<StorageInterface, 'get' | 'put'>;
requestChallenge(request: IPCRequest): void;
startQueue(conversationId: string): void;
sendChallengeResponse(data: ChallengeData): Promise<void>;
setChallengeStatus(challengeStatus: 'idle' | 'required' | 'pending'): void;
onChallengeSolved(): void;
onChallengeFailed(retryAfter?: number): void;
expireAfter?: number;
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}>;
export const STORAGE_KEY = 'challenge:conversations';
export type RegisteredChallengeType = Readonly<{
conversationId: string;
createdAt: number;
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reason: string;
retryAt?: number;
token?: string;
}>;
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type SolveOptionsType = Readonly<{
token: string;
reason: string;
}>;
export type MaybeSolveOptionsType = Readonly<{
conversationId: string;
reason: string;
}>;
export type RequestCaptchaOptionsType = Readonly<{
reason: string;
token?: string;
}>;
const DEFAULT_EXPIRE_AFTER = 24 * 3600 * 1000; // one day
const CAPTCHA_URL = 'https://signalcaptchas.org/challenge/generate.html';
const CAPTCHA_STAGING_URL =
'https://signalcaptchas.org/staging/challenge/generate.html';
function shouldStartQueue(registered: RegisteredChallengeType): boolean {
// No retryAt provided; waiting for user to complete captcha
if (!registered.retryAt) {
return false;
}
if (registered.retryAt <= Date.now()) {
return true;
}
return false;
}
export function getChallengeURL(): string {
if (getEnvironment() === Environment.Staging) {
return CAPTCHA_STAGING_URL;
}
return CAPTCHA_URL;
}
// Note that even though this is a class - only one instance of
// `ChallengeHandler` should be in memory at the same time because they could
// overwrite each others storage data.
export class ChallengeHandler {
private solving = 0;
private isLoaded = false;
private challengeToken: string | undefined;
private seq = 0;
private isOnline = false;
private readonly responseHandlers = new Map<number, Handler>();
private readonly registeredConversations = new Map<
string,
RegisteredChallengeType
>();
private readonly startTimers = new Map<string, NodeJS.Timeout>();
private readonly pendingStarts = new Set<string>();
constructor(private readonly options: Options) {}
public async load(): Promise<void> {
if (this.isLoaded) {
return;
}
this.isLoaded = true;
const challenges: ReadonlyArray<RegisteredChallengeType> =
this.options.storage.get(STORAGE_KEY) || [];
log.info(`challenge: loading ${challenges.length} challenges`);
await Promise.all(
challenges.map(async challenge => {
const expireAfter = this.options.expireAfter || DEFAULT_EXPIRE_AFTER;
if (isOlderThan(challenge.createdAt, expireAfter)) {
log.info(
`challenge: expired challenge for conversation ${challenge.conversationId}`
);
return;
}
// The initialization order is following:
//
// 1. `.load()` when the `window.storage` is ready
// 2. `.onOnline()` when we connected to the server
//
// Wait for `.onOnline()` to trigger the retries instead of triggering
// them here immediately (if the message is ready to be retried).
await this.register(challenge);
})
);
}
public async onOffline(): Promise<void> {
this.isOnline = false;
log.info('challenge: offline');
}
public async onOnline(): Promise<void> {
this.isOnline = true;
const pending = Array.from(this.pendingStarts.values());
this.pendingStarts.clear();
log.info(`challenge: online, starting ${pending.length} queues`);
// Start queues for challenges that matured while we were offline
await Promise.all(
pending.map(conversationId => this.startQueue(conversationId))
);
await this.startAllQueues();
}
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public maybeSolve({ conversationId, reason }: MaybeSolveOptionsType): void {
const challenge = this.registeredConversations.get(conversationId);
if (!challenge) {
return;
}
if (this.solving > 0) {
return;
}
if (challenge.token) {
void this.solve({ reason, token: challenge.token });
}
}
public async register(
challenge: RegisteredChallengeType,
data?: SendMessageChallengeData
): Promise<void> {
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const { conversationId, reason } = challenge;
const logId = `challenge(${reason})`;
if (this.isRegistered(conversationId)) {
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log.info(`${logId}: conversation ${conversationId} already registered`);
return;
}
this.registeredConversations.set(conversationId, challenge);
await this.persist();
// Challenge is already retryable - start the queue
if (shouldStartQueue(challenge)) {
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log.info(`${logId}: starting conversation ${conversationId} immediately`);
await this.startQueue(conversationId);
return;
}
if (challenge.retryAt) {
const waitTime = Math.max(0, challenge.retryAt - Date.now());
const oldTimer = this.startTimers.get(conversationId);
if (oldTimer) {
clearTimeoutIfNecessary(oldTimer);
}
this.startTimers.set(
conversationId,
setTimeout(() => {
this.startTimers.delete(conversationId);
void this.startQueue(conversationId);
}, waitTime)
);
log.info(
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`${logId}: tracking ${conversationId} with waitTime=${waitTime}`
);
} else {
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log.info(`${logId}: tracking ${conversationId} with no waitTime`);
}
if (data && !data.options?.includes('recaptcha')) {
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log.error(`${logId}: unexpected options ${JSON.stringify(data.options)}`);
}
if (!challenge.token) {
const dataString = JSON.stringify(data);
log.error(
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`${logId}: ${conversationId} is waiting; no token in data ${dataString}`
);
return;
}
void this.solve({ token: challenge.token, reason });
}
public onResponse(response: IPCResponse): void {
const handler = this.responseHandlers.get(response.seq);
if (!handler) {
return;
}
this.responseHandlers.delete(response.seq);
handler.resolve(response.data);
}
public async unregister(conversationId: string): Promise<void> {
log.info(`challenge: unregistered conversation ${conversationId}`);
this.registeredConversations.delete(conversationId);
this.pendingStarts.delete(conversationId);
const timer = this.startTimers.get(conversationId);
this.startTimers.delete(conversationId);
clearTimeoutIfNecessary(timer);
await this.persist();
}
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public async requestCaptcha({
reason,
token = '',
}: RequestCaptchaOptionsType): Promise<string> {
const request: IPCRequest = { seq: this.seq, reason };
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this.seq += 1;
this.options.requestChallenge(request);
const response = await new Promise<ChallengeResponse>((resolve, reject) => {
this.responseHandlers.set(request.seq, { token, resolve, reject });
});
return response.captcha;
}
private async persist(): Promise<void> {
assertDev(
this.isLoaded,
'ChallengeHandler has to be loaded before persisting new data'
);
await this.options.storage.put(
STORAGE_KEY,
Array.from(this.registeredConversations.values())
);
}
public isRegistered(conversationId: string): boolean {
return this.registeredConversations.has(conversationId);
}
private startAllQueues({
force = false,
}: {
force?: boolean;
} = {}): void {
log.info(`challenge: startAllQueues force=${force}`);
Array.from(this.registeredConversations.values())
.filter(challenge => force || shouldStartQueue(challenge))
.forEach(challenge => this.startQueue(challenge.conversationId));
}
private async startQueue(conversationId: string): Promise<void> {
if (!this.isOnline) {
this.pendingStarts.add(conversationId);
return;
}
await this.unregister(conversationId);
if (this.registeredConversations.size === 0) {
this.options.setChallengeStatus('idle');
}
log.info(`startQueue: starting queue ${conversationId}`);
this.options.startQueue(conversationId);
}
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private async solve({ reason, token }: SolveOptionsType): Promise<void> {
this.solving += 1;
this.options.setChallengeStatus('required');
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this.challengeToken = token;
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const captcha = await this.requestCaptcha({ reason, token });
// Another `.solve()` has completed earlier than us
if (this.challengeToken === undefined) {
this.solving -= 1;
return;
}
const lastToken = this.challengeToken;
this.challengeToken = undefined;
this.options.setChallengeStatus('pending');
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log.info(`challenge(${reason}): sending challenge to server`);
try {
await this.sendChallengeResponse({
type: 'recaptcha',
token: lastToken,
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captcha,
});
} catch (error) {
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log.error(
`challenge(${reason}): challenge failure, error:`,
Errors.toLogFormat(error)
);
this.options.setChallengeStatus('required');
this.solving -= 1;
return;
}
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log.info(`challenge(${reason}): challenge success. force sending`);
this.options.setChallengeStatus('idle');
this.startAllQueues({ force: true });
this.solving -= 1;
}
private async sendChallengeResponse(data: ChallengeData): Promise<void> {
try {
await this.options.sendChallengeResponse(data);
} catch (error) {
if (
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!(error instanceof HTTPError) ||
!(error.code === 413 || error.code === 429) ||
!error.responseHeaders
) {
this.options.onChallengeFailed();
throw error;
}
const retryAfter = parseRetryAfterWithDefault(
error.responseHeaders['retry-after']
);
log.info(`challenge: retry after ${retryAfter}ms`);
this.options.onChallengeFailed(retryAfter);
return;
}
this.options.onChallengeSolved();
}
}