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Enhance signature algorithm for code signatures #24727

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Enhance signature algorithm for code signatures #24727

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89b52c3
Also sign signatures with sha512
rullzer Dec 16, 2020
3ae54d2
<= 21 check for the new signature.
rullzer Dec 16, 2020
a074c3c
Always check new sig for server releases
rullzer Dec 16, 2020
e0802d8
Add info.xml
rullzer Jan 8, 2021
25df593
Bump autoloader
nickvergessen Jan 8, 2021
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1 change: 1 addition & 0 deletions lib/composer/composer/autoload_classmap.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1156,6 +1156,7 @@
'OC\\IntegrityCheck\\Helpers\\AppLocator' => $baseDir . '/lib/private/IntegrityCheck/Helpers/AppLocator.php',
'OC\\IntegrityCheck\\Helpers\\EnvironmentHelper' => $baseDir . '/lib/private/IntegrityCheck/Helpers/EnvironmentHelper.php',
'OC\\IntegrityCheck\\Helpers\\FileAccessHelper' => $baseDir . '/lib/private/IntegrityCheck/Helpers/FileAccessHelper.php',
'OC\\IntegrityCheck\\Helpers\\InfoParser' => $baseDir . '/lib/private/IntegrityCheck/Helpers/InfoParser.php',
'OC\\IntegrityCheck\\Iterator\\ExcludeFileByNameFilterIterator' => $baseDir . '/lib/private/IntegrityCheck/Iterator/ExcludeFileByNameFilterIterator.php',
'OC\\IntegrityCheck\\Iterator\\ExcludeFoldersByPathFilterIterator' => $baseDir . '/lib/private/IntegrityCheck/Iterator/ExcludeFoldersByPathFilterIterator.php',
'OC\\L10N\\Factory' => $baseDir . '/lib/private/L10N/Factory.php',
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1 change: 1 addition & 0 deletions lib/composer/composer/autoload_static.php
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Expand Up @@ -1185,6 +1185,7 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
'OC\\IntegrityCheck\\Helpers\\AppLocator' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Helpers/AppLocator.php',
'OC\\IntegrityCheck\\Helpers\\EnvironmentHelper' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Helpers/EnvironmentHelper.php',
'OC\\IntegrityCheck\\Helpers\\FileAccessHelper' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Helpers/FileAccessHelper.php',
'OC\\IntegrityCheck\\Helpers\\InfoParser' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Helpers/InfoParser.php',
'OC\\IntegrityCheck\\Iterator\\ExcludeFileByNameFilterIterator' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Iterator/ExcludeFileByNameFilterIterator.php',
'OC\\IntegrityCheck\\Iterator\\ExcludeFoldersByPathFilterIterator' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Iterator/ExcludeFoldersByPathFilterIterator.php',
'OC\\L10N\\Factory' => __DIR__ . '/../../..' . '/lib/private/L10N/Factory.php',
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57 changes: 45 additions & 12 deletions lib/private/IntegrityCheck/Checker.php
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@
use OC\IntegrityCheck\Helpers\AppLocator;
use OC\IntegrityCheck\Helpers\EnvironmentHelper;
use OC\IntegrityCheck\Helpers\FileAccessHelper;
use OC\IntegrityCheck\Helpers\InfoParser;
use OC\IntegrityCheck\Iterator\ExcludeFileByNameFilterIterator;
use OC\IntegrityCheck\Iterator\ExcludeFoldersByPathFilterIterator;
use OCP\App\IAppManager;
Expand Down Expand Up @@ -76,6 +77,8 @@ class Checker {
private $tempManager;
/** @var IMimeTypeDetector */
private $mimeTypeDetector;
/** @var InfoParser */
private $infoParser;

/**
* @param EnvironmentHelper $environmentHelper
Expand All @@ -89,6 +92,7 @@ class Checker {
*/
public function __construct(EnvironmentHelper $environmentHelper,
FileAccessHelper $fileAccessHelper,
InfoParser $infoParser,
AppLocator $appLocator,
IConfig $config = null,
ICacheFactory $cacheFactory,
Expand All @@ -103,6 +107,7 @@ public function __construct(EnvironmentHelper $environmentHelper,
$this->appManager = $appManager;
$this->tempManager = $tempManager;
$this->mimeTypeDetector = $mimeTypeDetector;
$this->infoParser = $infoParser;
}

/**
Expand Down Expand Up @@ -235,13 +240,21 @@ private function createSignatureData(array $hashes,

$privateKey->setSignatureMode(RSA::SIGNATURE_PSS);
$privateKey->setMGFHash('sha512');
$privateKey->setHash('sha1');
// See https://tools.ietf.org/html/rfc3447#page-38
$privateKey->setSaltLength(0);
$signature = $privateKey->sign(json_encode($hashes));
$sha1signature = $privateKey->sign(json_encode($hashes));

$privateKey->setHash('sha512');
$sha512signature = $privateKey->sign(json_encode($hashes));

return [
'hashes' => $hashes,
'signature' => base64_encode($signature),
'signature' => base64_encode($sha1signature),
'signatures' => [
'sha1' => base64_encode($sha1signature),
'sha512' => base64_encode($sha512signature),
],
'certificate' => $certificate->saveX509($certificate->currentCert),
];
}
Expand Down Expand Up @@ -311,11 +324,12 @@ public function writeCoreSignature(X509 $certificate,
* @param string $signaturePath
* @param string $basePath
* @param string $certificateCN
* @param string|null $forceHash
* @return array
* @throws InvalidSignatureException
* @throws \Exception
*/
private function verify(string $signaturePath, string $basePath, string $certificateCN): array {
private function verify(string $signaturePath, string $basePath, string $certificateCN, ?string $forceHash = null): array {
if (!$this->isCodeCheckEnforced()) {
return [];
}
Expand All @@ -332,7 +346,6 @@ private function verify(string $signaturePath, string $basePath, string $certifi

$expectedHashes = $signatureData['hashes'];
ksort($expectedHashes);
$signature = base64_decode($signatureData['signature']);
$certificate = $signatureData['certificate'];

// Check if certificate is signed by Nextcloud Root Authority
Expand All @@ -357,8 +370,19 @@ private function verify(string $signaturePath, string $basePath, string $certifi
$rsa->setMGFHash('sha512');
// See https://tools.ietf.org/html/rfc3447#page-38
$rsa->setSaltLength(0);
if (!$rsa->verify(json_encode($expectedHashes), $signature)) {
throw new InvalidSignatureException('Signature could not get verified.');

if ($forceHash && isset($signatureData['signatures'][$forceHash])) {
// Check the sha512 hash
$rsa->setHash($forceHash);
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That scares me a bit because it could eventually lead to something like https://auth0.com/blog/critical-vulnerabilities-in-json-web-token-libraries/, in which there is a null algorithm or something eventually.

Can we instead pass a version identifier (e.g. 2 == SHA512)?

if (!$rsa->verify(json_encode($expectedHashes), base64_decode($signatureData['signatures'][$forceHash]))) {
throw new InvalidSignatureException('Signature could not get verified.');
}
} else {
// The default fallback with the sha1 hash
$rsa->setHash('sha1');
if (!$rsa->verify(json_encode($expectedHashes), base64_decode($signatureData['signature']))) {
throw new InvalidSignatureException('Signature could not get verified.');
}
}

// Fixes for the updater as shipped with ownCloud 9.0.x: The updater is
Expand Down Expand Up @@ -502,10 +526,18 @@ public function verifyAppSignature(string $appId, string $path = ''): array {
if ($path === '') {
$path = $this->appLocator->getAppPath($appId);
}

$minVersion = $this->infoParser->getMinVersion($path . '/appinfo/info.xml');
$forceHash = null;
if ($minVersion >= 22) {
$forceHash = 'sha512';
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Can you elaborate the reason for the hardcoding here? :)

}

$result = $this->verify(
$path . '/appinfo/signature.json',
$path,
$appId
$path . '/appinfo/signature.json',
$path,
$appId,
$forceHash
);
} catch (\Exception $e) {
$result = [
Expand Down Expand Up @@ -553,9 +585,10 @@ public function verifyAppSignature(string $appId, string $path = ''): array {
public function verifyCoreSignature(): array {
try {
$result = $this->verify(
$this->environmentHelper->getServerRoot() . '/core/signature.json',
$this->environmentHelper->getServerRoot(),
'core'
$this->environmentHelper->getServerRoot() . '/core/signature.json',
$this->environmentHelper->getServerRoot(),
'core',
'sha512'
);
} catch (\Exception $e) {
$result = [
Expand Down
42 changes: 42 additions & 0 deletions lib/private/IntegrityCheck/Helpers/InfoParser.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
<?php

declare(strict_types=1);

/**
* @copyright Copyright (c) 2021, Roeland Jago Douma <roeland@famdouma.nl>
*
* @author Roeland Jago Douma <roeland@famdouma.nl>
*
* @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\IntegrityCheck\Helpers;

use OC\App\InfoParser as RealParser;

class InfoParser {
public function getMinVersion(string $infoPath): int {
$parser = new RealParser();
$result = $parser->parse($infoPath);

if (!isset($result['dependencies']['nextcloud']['@attributes']['min-version'])) {
throw new \Exception('Could not parse nextcloud dependency');
}

return (int)$result['dependencies']['nextcloud']['@attributes']['min-version'];
}
}
2 changes: 2 additions & 0 deletions lib/private/Server.php
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,7 @@
use OC\IntegrityCheck\Helpers\AppLocator;
use OC\IntegrityCheck\Helpers\EnvironmentHelper;
use OC\IntegrityCheck\Helpers\FileAccessHelper;
use OC\IntegrityCheck\Helpers\InfoParser;
use OC\Lock\DBLockingProvider;
use OC\Lock\MemcacheLockingProvider;
use OC\Lock\NoopLockingProvider;
Expand Down Expand Up @@ -938,6 +939,7 @@ public function __construct($webRoot, \OC\Config $config) {
return new Checker(
new EnvironmentHelper(),
new FileAccessHelper(),
new InfoParser(),
new AppLocator(),
$config,
$c->get(ICacheFactory::class),
Expand Down
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