/* This file is part of Telegram Desktop, the official desktop application for the Telegram messaging service. For license and copyright information please follow this link: https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL */ #include "mtproto/details/mtproto_domain_resolver.h" #include "base/random.h" #include "base/invoke_queued.h" #include "base/call_delayed.h" #include #include #include #include #include #include #include namespace MTP::details { namespace { constexpr auto kSendNextTimeout = crl::time(800); constexpr auto kMinTimeToLive = 10 * crl::time(1000); constexpr auto kMaxTimeToLive = 300 * crl::time(1000); } // namespace const std::vector &DnsDomains() { static const auto kResult = std::vector{ "google.com", "www.google.com", "google.ru", "www.google.ru", }; return kResult; } QString GenerateDnsRandomPadding() { constexpr char kValid[] = "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; auto result = QString(); const auto count = [&] { constexpr auto kMinPadding = 13; constexpr auto kMaxPadding = 128; while (true) { const auto result = 1 + (base::RandomValue() / 2); Assert(result <= kMaxPadding); if (result >= kMinPadding) { return result; } } }(); result.resize(count); for (auto &ch : result) { ch = kValid[base::RandomValue() % (sizeof(kValid) - 1)]; } return result; } QByteArray DnsUserAgent() { static const auto kResult = QByteArray( "Mozilla/5.0 (Windows NT 10.0; Win64; x64) " "AppleWebKit/537.36 (KHTML, like Gecko) " "Chrome/109.0.5414.74 Safari/537.36"); return kResult; } std::vector ParseDnsResponse( const QByteArray &bytes, std::optional typeRestriction) { if (bytes.isEmpty()) { return {}; } // Read and store to "result" all the data bytes from the response: // { .., // "Answer": [ // { .., "data": "bytes1", "TTL": int, .. }, // { .., "data": "bytes2", "TTL": int, .. } // ], // .. } auto error = QJsonParseError{ 0, QJsonParseError::NoError }; const auto document = QJsonDocument::fromJson(bytes, &error); if (error.error != QJsonParseError::NoError) { LOG(("Config Error: Failed to parse dns response JSON, error: %1" ).arg(error.errorString())); return {}; } else if (!document.isObject()) { LOG(("Config Error: Not an object received in dns response JSON.")); return {}; } const auto response = document.object(); const auto answerIt = response.find("Answer"); if (answerIt == response.constEnd()) { LOG(("Config Error: Could not find Answer in dns response JSON.")); return {}; } else if (!(*answerIt).isArray()) { LOG(("Config Error: Not an array received " "in Answer in dns response JSON.")); return {}; } auto result = std::vector(); for (const auto elem : (*answerIt).toArray()) { if (!elem.isObject()) { LOG(("Config Error: Not an object found " "in Answer array in dns response JSON.")); continue; } const auto object = elem.toObject(); if (typeRestriction) { const auto typeIt = object.find("type"); const auto type = int(base::SafeRound((*typeIt).toDouble())); if (!(*typeIt).isDouble()) { LOG(("Config Error: Not a number in type field " "in Answer array in dns response JSON.")); continue; } else if (type != *typeRestriction) { continue; } } const auto dataIt = object.find("data"); if (dataIt == object.constEnd()) { LOG(("Config Error: Could not find data " "in Answer array entry in dns response JSON.")); continue; } else if (!(*dataIt).isString()) { LOG(("Config Error: Not a string data found " "in Answer array entry in dns response JSON.")); continue; } const auto ttlIt = object.find("TTL"); const auto ttl = (ttlIt != object.constEnd()) ? crl::time(base::SafeRound((*ttlIt).toDouble())) : crl::time(0); result.push_back({ (*dataIt).toString(), ttl }); } return result; } ServiceWebRequest::ServiceWebRequest(not_null reply) : reply(reply.get()) { } ServiceWebRequest::ServiceWebRequest(ServiceWebRequest &&other) : reply(base::take(other.reply)) { } ServiceWebRequest &ServiceWebRequest::operator=(ServiceWebRequest &&other) { if (reply != other.reply) { destroy(); reply = base::take(other.reply); } return *this; } void ServiceWebRequest::destroy() { if (const auto value = base::take(reply)) { value->disconnect( value, &QNetworkReply::finished, nullptr, nullptr); value->abort(); value->deleteLater(); } } ServiceWebRequest::~ServiceWebRequest() { if (reply) { reply->deleteLater(); } } DomainResolver::DomainResolver(Fn callback) : _callback(std::move(callback)) { _manager.setProxy(QNetworkProxy::NoProxy); } void DomainResolver::resolve(const QString &domain) { resolve({ domain, false }); resolve({ domain, true }); } void DomainResolver::resolve(const AttemptKey &key) { if (_attempts.find(key) != end(_attempts)) { return; } else if (_requests.find(key) != end(_requests)) { return; } const auto i = _cache.find(key); _lastTimestamp = crl::now(); if (i != end(_cache) && i->second.expireAt > _lastTimestamp) { checkExpireAndPushResult(key.domain); return; } auto attempts = std::vector(); auto domains = DnsDomains(); std::random_device rd; ranges::shuffle(domains, std::mt19937(rd())); const auto takeDomain = [&] { const auto result = domains.back(); domains.pop_back(); return result; }; const auto shuffle = [&](int from, int till) { Expects(till > from); ranges::shuffle( begin(attempts) + from, begin(attempts) + till, std::mt19937(rd())); }; attempts.push_back({ Type::Google, "dns.google.com" }); attempts.push_back({ Type::Google, takeDomain(), "dns" }); attempts.push_back({ Type::Mozilla, "mozilla.cloudflare-dns.com" }); while (!domains.empty()) { attempts.push_back({ Type::Google, takeDomain(), "dns" }); } shuffle(0, 2); ranges::reverse(attempts); // We go from last to first. _attempts.emplace(key, Attempts{ std::move(attempts) }); sendNextRequest(key); } void DomainResolver::checkExpireAndPushResult(const QString &domain) { const auto ipv4 = _cache.find({ domain, false }); if (ipv4 == end(_cache) || ipv4->second.expireAt <= _lastTimestamp) { return; } auto result = ipv4->second; const auto ipv6 = _cache.find({ domain, true }); if (ipv6 != end(_cache) && ipv6->second.expireAt > _lastTimestamp) { result.ips.append(ipv6->second.ips); accumulate_min(result.expireAt, ipv6->second.expireAt); } InvokeQueued(this, [=] { _callback(domain, result.ips, result.expireAt); }); } void DomainResolver::sendNextRequest(const AttemptKey &key) { auto i = _attempts.find(key); if (i == end(_attempts)) { return; } auto &attempts = i->second; auto &list = attempts.list; const auto attempt = list.back(); list.pop_back(); if (!list.empty()) { base::call_delayed(kSendNextTimeout, &attempts.guard, [=] { sendNextRequest(key); }); } performRequest(key, attempt); } void DomainResolver::performRequest( const AttemptKey &key, const Attempt &attempt) { auto url = QUrl(); url.setScheme("https"); auto request = QNetworkRequest(); switch (attempt.type) { case Type::Mozilla: { url.setHost(attempt.data); url.setPath("/dns-query"); url.setQuery(QStringLiteral("name=%1&type=%2&random_padding=%3" ).arg(key.domain ).arg(key.ipv6 ? 28 : 1 ).arg(GenerateDnsRandomPadding())); request.setRawHeader("accept", "application/dns-json"); } break; case Type::Google: { url.setHost(attempt.data); url.setPath("/resolve"); url.setQuery(QStringLiteral("name=%1&type=%2&random_padding=%3" ).arg(key.domain ).arg(key.ipv6 ? 28 : 1 ).arg(GenerateDnsRandomPadding())); if (!attempt.host.isEmpty()) { const auto host = attempt.host + ".google.com"; request.setRawHeader("Host", host.toLatin1()); } } break; default: Unexpected("Type in DomainResolver::performRequest."); } request.setUrl(url); request.setRawHeader("User-Agent", DnsUserAgent()); const auto i = _requests.emplace( key, std::vector()).first; const auto reply = i->second.emplace_back( _manager.get(request) ).reply; connect(reply, &QNetworkReply::finished, this, [=] { requestFinished(key, reply); }); } void DomainResolver::requestFinished( const AttemptKey &key, not_null reply) { const auto result = finalizeRequest(key, reply); const auto response = ParseDnsResponse(result); if (response.empty()) { return; } _requests.erase(key); _attempts.erase(key); auto entry = CacheEntry(); auto ttl = kMaxTimeToLive; for (const auto &item : response) { entry.ips.push_back(item.data); ttl = std::min( ttl, std::max(item.TTL * crl::time(1000), kMinTimeToLive)); } _lastTimestamp = crl::now(); entry.expireAt = _lastTimestamp + ttl; _cache[key] = std::move(entry); checkExpireAndPushResult(key.domain); } QByteArray DomainResolver::finalizeRequest( const AttemptKey &key, not_null reply) { if (reply->error() != QNetworkReply::NoError) { DEBUG_LOG(("Resolve Error: Failed to get response, error: %2 (%3)" ).arg(reply->errorString() ).arg(reply->error())); } const auto result = reply->readAll(); const auto i = _requests.find(key); if (i != end(_requests)) { auto &requests = i->second; const auto from = ranges::remove( requests, reply, [](const ServiceWebRequest &request) { return request.reply; }); requests.erase(from, end(requests)); if (requests.empty()) { _requests.erase(i); } } return result; } } // namespace MTP::details