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Fix DNS pin middleware can be tricked into DNS rebinding allowing SSRF
nextcloud/server#40234 enh: skip processing for empty response #40234
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,155 @@ | ||
| <?php | ||
|
|
||
| declare(strict_types=1); | ||
|
|
||
| /** | ||
| * @copyright Copyright (c) 2021, Lukas Reschke <[email protected]> | ||
| * | ||
| * @author Lukas Reschke <[email protected]> | ||
| * | ||
| * @license GNU AGPL version 3 or any later version | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU Affero General Public License as | ||
| * published by the Free Software Foundation, either version 3 of the | ||
| * License, or (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU Affero General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU Affero General Public License | ||
| * along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
| * | ||
| */ | ||
| namespace OC\Http\Client; | ||
|
|
||
| use OCP\Http\Client\LocalServerException; | ||
| use Psr\Http\Message\RequestInterface; | ||
|
|
||
| class DnsPinMiddleware { | ||
| /** @var NegativeDnsCache */ | ||
| private $negativeDnsCache; | ||
| /** @var LocalAddressChecker */ | ||
| private $localAddressChecker; | ||
|
|
||
| public function __construct( | ||
| NegativeDnsCache $negativeDnsCache, | ||
| LocalAddressChecker $localAddressChecker | ||
| ) { | ||
| $this->negativeDnsCache = $negativeDnsCache; | ||
| $this->localAddressChecker = $localAddressChecker; | ||
| } | ||
|
|
||
| /** | ||
| * Fetch soa record for a target | ||
| * | ||
| * @param string $target | ||
| * @return array|null | ||
| */ | ||
| private function soaRecord(string $target): ?array { | ||
| $labels = explode('.', $target); | ||
|
|
||
| $top = count($labels) >= 2 ? array_pop($labels) : ''; | ||
| $second = array_pop($labels); | ||
|
|
||
| $hostname = $second . '.' . $top; | ||
| $responses = dns_get_record($hostname, DNS_SOA); | ||
|
|
||
| if ($responses === false || count($responses) === 0) { | ||
| return null; | ||
| } | ||
|
|
||
| return reset($responses); | ||
| } | ||
|
|
||
| private function dnsResolve(string $target, int $recursionCount) : array { | ||
| if ($recursionCount >= 10) { | ||
| return []; | ||
| } | ||
|
|
||
| $recursionCount++; | ||
| $targetIps = []; | ||
|
|
||
| $soaDnsEntry = $this->soaRecord($target); | ||
| $dnsNegativeTtl = $soaDnsEntry['minimum-ttl'] ?? null; | ||
|
|
||
| $dnsTypes = [DNS_A, DNS_AAAA, DNS_CNAME]; | ||
| foreach ($dnsTypes as $dnsType) { | ||
| if ($this->negativeDnsCache->isNegativeCached($target, $dnsType)) { | ||
| continue; | ||
| } | ||
|
|
||
| $dnsResponses = dns_get_record($target, $dnsType); | ||
| $canHaveCnameRecord = true; | ||
| if ($dnsResponses !== false && count($dnsResponses) > 0) { | ||
| foreach ($dnsResponses as $dnsResponse) { | ||
| if (isset($dnsResponse['ip'])) { | ||
| $targetIps[] = $dnsResponse['ip']; | ||
| $canHaveCnameRecord = false; | ||
| } elseif (isset($dnsResponse['ipv6'])) { | ||
| $targetIps[] = $dnsResponse['ipv6']; | ||
| $canHaveCnameRecord = false; | ||
| } elseif (isset($dnsResponse['target']) && $canHaveCnameRecord) { | ||
| $targetIps = array_merge($targetIps, $this->dnsResolve($dnsResponse['target'], $recursionCount)); | ||
| $canHaveCnameRecord = true; | ||
| } | ||
| } | ||
| } elseif ($dnsNegativeTtl !== null) { | ||
| $this->negativeDnsCache->setNegativeCacheForDnsType($target, $dnsType, $dnsNegativeTtl); | ||
| } | ||
| } | ||
|
|
||
| return $targetIps; | ||
| } | ||
|
|
||
| public function addDnsPinning() { | ||
| return function (callable $handler) { | ||
| return function ( | ||
| RequestInterface $request, | ||
| array $options | ||
| ) use ($handler) { | ||
| if ($options['nextcloud']['allow_local_address'] === true) { | ||
| return $handler($request, $options); | ||
| } | ||
|
|
||
| $hostName = (string)$request->getUri()->getHost(); | ||
| $port = $request->getUri()->getPort(); | ||
|
|
||
| $ports = [ | ||
| '80', | ||
| '443', | ||
| ]; | ||
|
|
||
| if ($port !== null) { | ||
| $ports[] = (string)$port; | ||
| } | ||
|
|
||
| $targetIps = $this->dnsResolve(idn_to_utf8($hostName), 0); | ||
|
|
||
| if (empty($targetIps)) { | ||
| throw new LocalServerException('No DNS record found for ' . $hostName); | ||
| } | ||
|
|
||
| $curlResolves = []; | ||
|
|
||
| foreach ($ports as $port) { | ||
| $curlResolves["$hostName:$port"] = []; | ||
|
|
||
| foreach ($targetIps as $ip) { | ||
| $this->localAddressChecker->ThrowIfLocalIp($ip); | ||
| $curlResolves["$hostName:$port"][] = $ip; | ||
| } | ||
| } | ||
|
|
||
| // Coalesce the per-host:port ips back into a comma separated list | ||
| foreach ($curlResolves as $hostport => $ips) { | ||
| $options['curl'][CURLOPT_RESOLVE][] = "$hostport:" . implode(',', $ips); | ||
| } | ||
|
|
||
| return $handler($request, $options); | ||
| }; | ||
| }; | ||
| } | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,150 @@ | ||
| <?php | ||
|
|
||
| declare(strict_types=1); | ||
|
|
||
| /** | ||
| * @copyright Copyright (c) 2021, Lukas Reschke <[email protected]> | ||
| * | ||
| * @author Lukas Reschke <[email protected]> | ||
| * | ||
| * @license GNU AGPL version 3 or any later version | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU Affero General Public License as | ||
| * published by the Free Software Foundation, either version 3 of the | ||
| * License, or (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU Affero General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU Affero General Public License | ||
| * along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
| * | ||
| */ | ||
| namespace OC\Http\Client; | ||
|
|
||
| use Psr\Http\Message\RequestInterface; | ||
|
|
||
| class DnsPinMiddleware { | ||
| /** @var NegativeDnsCache */ | ||
| private $negativeDnsCache; | ||
| /** @var LocalAddressChecker */ | ||
| private $localAddressChecker; | ||
|
|
||
| public function __construct( | ||
| NegativeDnsCache $negativeDnsCache, | ||
| LocalAddressChecker $localAddressChecker | ||
| ) { | ||
| $this->negativeDnsCache = $negativeDnsCache; | ||
| $this->localAddressChecker = $localAddressChecker; | ||
| } | ||
|
|
||
| /** | ||
| * Fetch soa record for a target | ||
| * | ||
| * @param string $target | ||
| * @return array|null | ||
| */ | ||
| private function soaRecord(string $target): ?array { | ||
| $labels = explode('.', $target); | ||
|
|
||
| $top = count($labels) >= 2 ? array_pop($labels) : ''; | ||
| $second = array_pop($labels); | ||
|
|
||
| $hostname = $second . '.' . $top; | ||
| $responses = dns_get_record($hostname, DNS_SOA); | ||
|
|
||
| if ($responses === false || count($responses) === 0) { | ||
| return null; | ||
| } | ||
|
|
||
| return reset($responses); | ||
| } | ||
|
|
||
| private function dnsResolve(string $target, int $recursionCount) : array { | ||
| if ($recursionCount >= 10) { | ||
| return []; | ||
| } | ||
|
|
||
| $recursionCount++; | ||
| $targetIps = []; | ||
|
|
||
| $soaDnsEntry = $this->soaRecord($target); | ||
| $dnsNegativeTtl = $soaDnsEntry['minimum-ttl'] ?? null; | ||
|
|
||
| $dnsTypes = [DNS_A, DNS_AAAA, DNS_CNAME]; | ||
| foreach ($dnsTypes as $dnsType) { | ||
| if ($this->negativeDnsCache->isNegativeCached($target, $dnsType)) { | ||
| continue; | ||
| } | ||
|
|
||
| $dnsResponses = dns_get_record($target, $dnsType); | ||
| $canHaveCnameRecord = true; | ||
| if ($dnsResponses !== false && count($dnsResponses) > 0) { | ||
| foreach ($dnsResponses as $dnsResponse) { | ||
| if (isset($dnsResponse['ip'])) { | ||
| $targetIps[] = $dnsResponse['ip']; | ||
| $canHaveCnameRecord = false; | ||
| } elseif (isset($dnsResponse['ipv6'])) { | ||
| $targetIps[] = $dnsResponse['ipv6']; | ||
| $canHaveCnameRecord = false; | ||
| } elseif (isset($dnsResponse['target']) && $canHaveCnameRecord) { | ||
| $targetIps = array_merge($targetIps, $this->dnsResolve($dnsResponse['target'], $recursionCount)); | ||
| $canHaveCnameRecord = true; | ||
| } | ||
| } | ||
| } elseif ($dnsNegativeTtl !== null) { | ||
| $this->negativeDnsCache->setNegativeCacheForDnsType($target, $dnsType, $dnsNegativeTtl); | ||
| } | ||
| } | ||
|
|
||
| return $targetIps; | ||
| } | ||
|
|
||
| public function addDnsPinning() { | ||
| return function (callable $handler) { | ||
| return function ( | ||
| RequestInterface $request, | ||
| array $options | ||
| ) use ($handler) { | ||
| if ($options['nextcloud']['allow_local_address'] === true) { | ||
| return $handler($request, $options); | ||
| } | ||
|
|
||
| $hostName = (string)$request->getUri()->getHost(); | ||
| $port = $request->getUri()->getPort(); | ||
|
|
||
| $ports = [ | ||
| '80', | ||
| '443', | ||
| ]; | ||
|
|
||
| if ($port !== null) { | ||
| $ports[] = (string)$port; | ||
| } | ||
|
|
||
| $targetIps = $this->dnsResolve(idn_to_utf8($hostName), 0); | ||
|
|
||
| $curlResolves = []; | ||
|
|
||
| foreach ($ports as $port) { | ||
| $curlResolves["$hostName:$port"] = []; | ||
|
|
||
| foreach ($targetIps as $ip) { | ||
| $this->localAddressChecker->ThrowIfLocalIp($ip); | ||
| $curlResolves["$hostName:$port"][] = $ip; | ||
| } | ||
| } | ||
|
|
||
| // Coalesce the per-host:port ips back into a comma separated list | ||
| foreach ($curlResolves as $hostport => $ips) { | ||
| $options['curl'][CURLOPT_RESOLVE][] = "$hostport:" . implode(',', $ips); | ||
| } | ||
|
|
||
| return $handler($request, $options); | ||
| }; | ||
| }; | ||
| } | ||
| } |