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[](https://scrutinizer-ci.com/g/TYPO3/phar-stream-wrapper/?branch=v2) [](https://travis-ci.org/TYPO3/phar-stream-wrapper) [](https://ci.appveyor.com/project/ohader/phar-stream-wrapper) # PHP Phar Stream Wrapper ## Abstract & History Based on Sam Thomas' findings concerning [insecure deserialization in combination with obfuscation strategies](https://blog.secarma.co.uk/labs/near-phar-dangerous-unserialization-wherever-you-are) allowing to hide Phar files inside valid image resources, the TYPO3 project decided back then to introduce a `PharStreamWrapper` to intercept invocations of the `phar://` stream in PHP and only allow usage for defined locations in the file system. Since the TYPO3 mission statement is **inspiring people to share**, we thought it would be helpful for others to release our `PharStreamWrapper` as standalone package to the PHP community. The mentioned security issue was reported to TYPO3 on 10th June 2018 by Sam Thomas and has been addressed concerning the specific attack vector and for this generic `PharStreamWrapper` in TYPO3 versions 7.6.30 LTS, 8.7.17 LTS and 9.3.1 on 12th July 2018. * https://blog.secarma.co.uk/labs/near-phar-dangerous-unserialization-wherever-you-are * https://youtu.be/GePBmsNJw6Y * https://typo3.org/security/advisory/typo3-psa-2018-001/ * https://typo3.org/security/advisory/typo3-psa-2019-007/ * https://typo3.org/security/advisory/typo3-psa-2019-008/ ## License In general the TYPO3 core is released under the GNU General Public License version 2 or any later version (`GPL-2.0-or-later`). In order to avoid licensing issues and incompatibilities this `PharStreamWrapper` is licenced under the MIT License. In case you duplicate or modify source code, credits are not required but really appreciated. ## Credits Thanks to [Alex Pott](https://github.com/alexpott), Drupal for creating back-ports of all sources in order to provide compatibility with PHP v5.3. ## Installation The `PharStreamWrapper` is provided as composer package `typo3/phar-stream-wrapper` and has minimum requirements of PHP v5.3 ([`v2`](https://github.com/TYPO3/phar-stream-wrapper/tree/v2) branch) and PHP v7.0 ([`master`](https://github.com/TYPO3/phar-stream-wrapper) branch). ### Installation for PHP v7.0 ``` composer require typo3/phar-stream-wrapper ^3.0 ``` ### Installation for PHP v5.3 ``` composer require typo3/phar-stream-wrapper ^2.0 ``` ## Example The following example is bundled within this package, the shown `PharExtensionInterceptor` denies all stream wrapper invocations files not having the `.phar` suffix. Interceptor logic has to be individual and adjusted to according requirements. ``` $behavior = new \TYPO3\PharStreamWrapper\Behavior(); \TYPO3\PharStreamWrapper\Manager::initialize( $behavior->withAssertion(new PharExtensionInterceptor()) ); if (in_array('phar', stream_get_wrappers())) { stream_wrapper_unregister('phar'); stream_wrapper_register('phar', 'TYPO3\\PharStreamWrapper\\PharStreamWrapper'); } ``` * `PharStreamWrapper` defined as class reference will be instantiated each time `phar://` streams shall be processed. * `Manager` as singleton pattern being called by `PharStreamWrapper` instances in order to retrieve individual behavior and settings. * `Behavior` holds reference to interceptor(s) that shall assert correct/allowed invocation of a given `$path` for a given `$command`. Interceptors implement the interface `Assertable`. Interceptors can act individually on following commands or handle all of them in case not defined specifically: + `COMMAND_DIR_OPENDIR` + `COMMAND_MKDIR` + `COMMAND_RENAME` + `COMMAND_RMDIR` + `COMMAND_STEAM_METADATA` + `COMMAND_STREAM_OPEN` + `COMMAND_UNLINK` + `COMMAND_URL_STAT` ## Interceptors The following interceptor is shipped with the package and ready to use in order to block any Phar invocation of files not having a `.phar` suffix. Besides that individual interceptors are possible of course. ``` class PharExtensionInterceptor implements Assertable { /** * Determines whether the base file name has a ".phar" suffix. * * @param string $path * @param string $command * @return bool * @throws Exception */ public function assert($path, $command) { if ($this->baseFileContainsPharExtension($path)) { return true; } throw new Exception( sprintf( 'Unexpected file extension in "%s"', $path ), 1535198703 ); } /** * @param string $path * @return bool */ private function baseFileContainsPharExtension($path) { $baseFile = Helper::determineBaseFile($path); if ($baseFile === null) { return false; } $fileExtension = pathinfo($baseFile, PATHINFO_EXTENSION); return strtolower($fileExtension) === 'phar'; } } ``` ### ConjunctionInterceptor This interceptor combines multiple interceptors implementing `Assertable`. It succeeds when all nested interceptors succeed as well (logical `AND`). ``` $behavior = new \TYPO3\PharStreamWrapper\Behavior(); \TYPO3\PharStreamWrapper\Manager::initialize( $behavior->withAssertion(new ConjunctionInterceptor(array( new PharExtensionInterceptor(), new PharMetaDataInterceptor() ))) ); ``` ### PharExtensionInterceptor This (basic) interceptor just checks whether the invoked Phar archive has an according `.phar` file extension. Resolving symbolic links as well as Phar internal alias resolving are considered as well. ``` $behavior = new \TYPO3\PharStreamWrapper\Behavior(); \TYPO3\PharStreamWrapper\Manager::initialize( $behavior->withAssertion(new PharExtensionInterceptor()) ); ``` ### PharMetaDataInterceptor This interceptor is actually checking serialized Phar meta-data against PHP objects and would consider a Phar archive malicious in case not only scalar values are found. A custom low-level `Phar\Reader` is used in order to avoid using PHP's `Phar` object which would trigger the initial vulnerability. ``` $behavior = new \TYPO3\PharStreamWrapper\Behavior(); \TYPO3\PharStreamWrapper\Manager::initialize( $behavior->withAssertion(new PharMetaDataInterceptor()) ); ``` ## Reader * `Phar\Reader::__construct(string $fileName)`: Creates low-level reader for Phar archive * `Phar\Reader::resolveContainer(): Phar\Container`: Resolves model representing Phar archive * `Phar\Container::getStub(): Phar\Stub`: Resolves (plain PHP) stub section of Phar archive * `Phar\Container::getManifest(): Phar\Manifest`: Resolves parsed Phar archive manifest as documented at http://php.net/manual/en/phar.fileformat.manifestfile.php * `Phar\Stub::getMappedAlias(): string`: Resolves internal Phar archive alias defined in stub using `Phar::mapPhar('alias.phar')` - actually the plain PHP source is analyzed here * `Phar\Manifest::getAlias(): string` - Resolves internal Phar archive alias defined in manifest using `Phar::setAlias('alias.phar')` * `Phar\Manifest::getMetaData(): string`: Resolves serialized Phar archive meta-data * `Phar\Manifest::deserializeMetaData(): mixed`: Resolves deserialized Phar archive meta-data containing only scalar values - in case an object is determined, an according `Phar\DeserializationException` will be thrown ``` $reader = new Phar\Reader('example.phar'); var_dump($reader->resolveContainer()->getManifest()->deserializeMetaData()); ``` ## Helper * `Helper::determineBaseFile(string $path): string`: Determines base file that can be accessed using the regular file system. For instance the following path `phar:///home/user/bundle.phar