mirror of
https://github.com/danog/dns-over-https.git
synced 2024-12-02 09:17:50 +01:00
392 lines
14 KiB
PHP
392 lines
14 KiB
PHP
<?php
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namespace Amp\DoH;
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use Amp\Cache\Cache;
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use Amp\Dns\ConfigException;
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use Amp\Dns\DnsException;
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use Amp\Dns\NoRecordException;
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use Amp\Dns\Record;
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use Amp\Dns\Resolver;
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use Amp\Dns\TimeoutException;
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use Amp\DoH\Internal\HttpsSocket;
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use Amp\DoH\Internal\Socket;
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use Amp\MultiReasonException;
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use Amp\Promise;
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use LibDNS\Messages\Message;
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use LibDNS\Records\Question;
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use LibDNS\Records\QuestionFactory;
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use function Amp\call;
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use function Amp\Dns\normalizeName;
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final class Rfc8484StubResolver implements Resolver
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{
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const CACHE_PREFIX = "amphp.doh.";
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/** @var \Amp\Dns\ConfigLoader */
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private $configLoader;
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/** @var \LibDNS\Records\QuestionFactory */
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private $questionFactory;
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/** @var \Amp\Dns\Config|null */
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private $config;
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/** @var Promise|null */
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private $pendingConfig;
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/** @var \Amp\DoH\DoHConfig */
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private $dohConfig;
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/** @var Cache */
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private $cache;
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/** @var Promise[] */
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private $pendingQueries = [];
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/** @var \Amp\Dns\Rfc1035StubResolver */
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private $subResolver;
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public function __construct(DoHConfig $config)
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{
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$resolver = $config->getSubResolver();
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if ($resolver instanceof Rfc8484StubResolver) {
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throw new ConfigException("Can't use Rfc8484StubResolver as subresolver for Rfc8484StubResolver");
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}
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$this->cache = $config->getCache();
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$this->configLoader = $config->getConfigLoader();
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$this->subResolver = $resolver;
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$this->dohConfig = $config;
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$this->questionFactory = new QuestionFactory;
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}
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/** @inheritdoc */
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public function resolve(string $name, int $typeRestriction = null): Promise
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{
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if ($typeRestriction !== null && $typeRestriction !== Record::A && $typeRestriction !== Record::AAAA) {
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throw new \Error("Invalid value for parameter 2: null|Record::A|Record::AAAA expected");
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}
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return call(function () use ($name, $typeRestriction) {
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if (!$this->config) {
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yield $this->reloadConfig();
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}
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switch ($typeRestriction) {
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case Record::A:
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
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return [new Record($name, Record::A, null)];
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} elseif (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
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throw new DnsException("Got an IPv6 address, but type is restricted to IPv4");
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}
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break;
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case Record::AAAA:
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
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return [new Record($name, Record::AAAA, null)];
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} elseif (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
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throw new DnsException("Got an IPv4 address, but type is restricted to IPv6");
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}
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break;
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default:
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if (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
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return [new Record($name, Record::A, null)];
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} elseif (\filter_var($name, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
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return [new Record($name, Record::AAAA, null)];
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}
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break;
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}
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$name = normalizeName($name);
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if ($records = $this->queryHosts($name, $typeRestriction)) {
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return $records;
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}
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// Follow RFC 6761 and never send queries for localhost to the caching DNS server
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// Usually, these queries are already resolved via queryHosts()
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if ($name === 'localhost') {
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return $typeRestriction === Record::AAAA
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? [new Record('::1', Record::AAAA, null)]
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: [new Record('127.0.0.1', Record::A, null)];
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}
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if ($this->dohConfig->isNameserver($name)) {
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// Work around an OPCache issue that returns an empty array with "return yield ...",
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// so assign to a variable first and return after the try block.
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//
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// See https://github.com/amphp/dns/issues/58.
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// See https://bugs.php.net/bug.php?id=74840.
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$records = yield $this->subResolver->resolve($name, $typeRestriction);
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return $records;
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}
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for ($redirects = 0; $redirects < 5; $redirects++) {
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try {
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if ($typeRestriction) {
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$records = yield $this->query($name, $typeRestriction);
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} else {
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try {
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list(, $records) = yield Promise\some([
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$this->query($name, Record::A),
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$this->query($name, Record::AAAA),
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]);
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$records = \array_merge(...$records);
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break; // Break redirect loop, otherwise we query the same records 5 times
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} catch (MultiReasonException $e) {
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$errors = [];
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foreach ($e->getReasons() as $reason) {
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if ($reason instanceof NoRecordException) {
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throw $reason;
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}
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$errors[] = $reason->getMessage();
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}
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throw new DnsException("All query attempts failed for {$name}: ".\implode(", ", $errors), 0, $e);
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}
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}
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} catch (NoRecordException $e) {
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try {
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/** @var Record[] $cnameRecords */
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$cnameRecords = yield $this->query($name, Record::CNAME);
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$name = $cnameRecords[0]->getValue();
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continue;
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} catch (NoRecordException $e) {
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/** @var Record[] $dnameRecords */
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$dnameRecords = yield $this->query($name, Record::DNAME);
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$name = $dnameRecords[0]->getValue();
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continue;
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}
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}
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}
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return $records;
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});
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}
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/**
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* Reloads the configuration in the background.
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*
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* Once it's finished, the configuration will be used for new requests.
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*
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* @return Promise
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*/
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public function reloadConfig(): Promise
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{
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$this->subResolver->reloadConfig();
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if ($this->pendingConfig) {
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return $this->pendingConfig;
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}
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$promise = call(function () {
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$this->config = yield $this->configLoader->loadConfig();
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});
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$this->pendingConfig = $promise;
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$promise->onResolve(function () {
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$this->pendingConfig = null;
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});
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return $promise;
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}
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private function queryHosts(string $name, int $typeRestriction = null): array
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{
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$hosts = $this->config->getKnownHosts();
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$records = [];
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$returnIPv4 = $typeRestriction === null || $typeRestriction === Record::A;
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$returnIPv6 = $typeRestriction === null || $typeRestriction === Record::AAAA;
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if ($returnIPv4 && isset($hosts[Record::A][$name])) {
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$records[] = new Record($hosts[Record::A][$name], Record::A, null);
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}
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if ($returnIPv6 && isset($hosts[Record::AAAA][$name])) {
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$records[] = new Record($hosts[Record::AAAA][$name], Record::AAAA, null);
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}
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return $records;
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}
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/** @inheritdoc */
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public function query(string $name, int $type): Promise
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{
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$pendingQueryKey = $type." ".$name;
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if (isset($this->pendingQueries[$pendingQueryKey])) {
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return $this->pendingQueries[$pendingQueryKey];
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}
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$promise = call(function () use ($name, $type) {
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if (!$this->config) {
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yield $this->reloadConfig();
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}
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$name = $this->normalizeName($name, $type);
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$question = $this->createQuestion($name, $type);
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if (null !== $cachedValue = yield $this->cache->get($this->getCacheKey($name, $type))) {
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return $this->decodeCachedResult($name, $type, $cachedValue);
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}
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/** @var Nameserver[] $nameservers */
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$nameservers = $this->dohConfig->getNameservers();
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$attempts = $this->config->getAttempts();
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$attempt = 0;
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/** @var Socket $socket */
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$nameserver = $nameservers[0];
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$socket = $this->getSocket($nameserver);
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$attemptDescription = [];
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while ($attempt < $attempts) {
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try {
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$attemptDescription[] = $nameserver;
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/** @var Message $response */
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$response = yield $socket->ask($question, $this->config->getTimeout());
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$this->assertAcceptableResponse($response);
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if ($response->isTruncated()) {
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throw new DnsException("Server returned a truncated response for '{$name}' (".Record::getName($type).")");
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}
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$answers = $response->getAnswerRecords();
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$result = [];
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$ttls = [];
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/** @var \LibDNS\Records\Resource $record */
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foreach ($answers as $record) {
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$recordType = $record->getType();
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$result[$recordType][] = (string) $record->getData();
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// Cache for max one day
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$ttls[$recordType] = \min($ttls[$recordType] ?? 86400, $record->getTTL());
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}
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foreach ($result as $recordType => $records) {
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// We don't care here whether storing in the cache fails
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$this->cache->set($this->getCacheKey($name, $recordType), \json_encode($records), $ttls[$recordType]);
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}
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if (!isset($result[$type])) {
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// "it MUST NOT cache it for longer than five (5) minutes" per RFC 2308 section 7.1
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$this->cache->set($this->getCacheKey($name, $type), \json_encode([]), 300);
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throw new NoRecordException("No records returned for '{$name}' (".Record::getName($type).")");
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}
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return \array_map(function ($data) use ($type, $ttls) {
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return new Record($data, $type, $ttls[$type]);
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}, $result[$type]);
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} catch (TimeoutException $e) {
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// Defer call, because it might interfere with the unreference() call in Internal\Socket otherwise
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$i = ++$attempt % \count($nameservers);
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$nameserver = $nameservers[$i];
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$socket = $this->getSocket($nameserver);
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continue;
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}
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}
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throw new TimeoutException(\sprintf(
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"No response for '%s' (%s) from any nameserver after %d attempts, tried %s",
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$name,
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Record::getName($type),
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$attempts,
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\implode(", ", $attemptDescription)
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));
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});
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$this->pendingQueries[$type." ".$name] = $promise;
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$promise->onResolve(function () use ($name, $type) {
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unset($this->pendingQueries[$type." ".$name]);
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});
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return $promise;
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}
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private function normalizeName(string $name, int $type)
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{
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if ($type === Record::PTR) {
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if (($packedIp = @\inet_pton($name)) !== false) {
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if (isset($packedIp[4])) { // IPv6
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$name = \wordwrap(\strrev(\bin2hex($packedIp)), 1, ".", true).".ip6.arpa";
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} else { // IPv4
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$name = \inet_ntop(\strrev($packedIp)).".in-addr.arpa";
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}
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}
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} elseif (\in_array($type, [Record::A, Record::AAAA])) {
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$name = normalizeName($name);
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}
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return $name;
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}
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/**
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* @param string $name
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* @param int $type
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*
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* @return \LibDNS\Records\Question
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*/
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private function createQuestion(string $name, int $type): Question
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{
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if (0 > $type || 0xffff < $type) {
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$message = \sprintf('%d does not correspond to a valid record type (must be between 0 and 65535).', $type);
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throw new \Error($message);
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}
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$question = $this->questionFactory->create($type);
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$question->setName($name);
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return $question;
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}
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private function getCacheKey(string $name, int $type): string
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{
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return self::CACHE_PREFIX.$name."#".$type;
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}
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private function decodeCachedResult(string $name, int $type, string $encoded)
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{
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$decoded = \json_decode($encoded, true);
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if (!$decoded) {
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throw new NoRecordException("No records returned for {$name} (cached result)");
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}
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$result = [];
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foreach ($decoded as $data) {
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$result[] = new Record($data, $type);
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}
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return $result;
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}
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private function getSocket(Nameserver $nameserver)
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{
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$uri = $nameserver->getUri();
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if (isset($this->sockets[$uri])) {
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return $this->sockets[$uri];
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}
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$this->sockets[$uri] = HttpsSocket::connect($this->dohConfig->getArtax(), $nameserver);
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return $this->sockets[$uri];
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}
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private function assertAcceptableResponse(Message $response)
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{
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if ($response->getResponseCode() !== 0) {
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throw new DnsException(\sprintf("Server returned error code: %d", $response->getResponseCode()));
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}
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}
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}
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