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<?php | |
/** | |
* @file | |
* Contains \Drupal\Component\PhpStorage\MTimeProtectedFileStorage. | |
*/ | |
namespace Drupal\Component\PhpStorage; | |
/** | |
* Stores PHP code in files with securely hashed names. | |
* | |
* The goal of this class is to ensure that if a PHP file is replaced with | |
* an untrusted one, it does not get loaded. Since mtime granularity is 1 | |
* second, we cannot prevent an attack that happens within one second of the | |
* initial save(). However, it is very unlikely for an attacker exploiting an | |
* upload or file write vulnerability to also know when a legitimate file is | |
* being saved, discover its hash, undo its file permissions, and override the | |
* file with an upload all within a single second. Being able to accomplish | |
* that would indicate a site very likely vulnerable to many other attack | |
* vectors. | |
* | |
* Each file is stored in its own unique containing directory. The hash is | |
* based on the virtual file name, the containing directory's mtime, and a | |
* cryptographically hard to guess secret string. Thus, even if the hashed file | |
* name is discovered and replaced by an untrusted file (e.g., via a | |
* move_uploaded_file() invocation by a script that performs insufficient | |
* validation), the directory's mtime gets updated in the process, invalidating | |
* the hash and preventing the untrusted file from getting loaded. Also, the | |
* file mtime will be checked providing security against overwriting in-place, | |
* at the cost of an additional system call for every load() and exists(). | |
* | |
* The containing directory is created with the same name as the virtual file | |
* name (slashes replaced with hashmarks) to assist with debugging, since the | |
* file itself is stored with a name that's meaningless to humans. | |
*/ | |
class MTimeProtectedFileStorage extends MTimeProtectedFastFileStorage { | |
/** | |
* {@inheritdoc} | |
*/ | |
public function load($name) { | |
if (($filename = $this->checkFile($name)) !== FALSE) { | |
// Inline parent::load() to avoid an expensive getFullPath() call. | |
return (@include_once $filename) !== FALSE; | |
} | |
return FALSE; | |
} | |
/** | |
* {@inheritdoc} | |
*/ | |
public function exists($name) { | |
return $this->checkFile($name) !== FALSE; | |
} | |
/** | |
* Determines whether a protected file exists and sets the filename too. | |
* | |
* @param string $name | |
* The virtual file name. Can be a relative path. | |
* | |
* @return string|false | |
* The full path where the file is if it is valid, FALSE otherwise. | |
*/ | |
protected function checkFile($name) { | |
$filename = $this->getFullPath($name, $directory, $directory_mtime); | |
return file_exists($filename) && filemtime($filename) <= $directory_mtime ? $filename : FALSE; | |
} | |
/** | |
* {@inheritdoc} | |
*/ | |
public function getPath($name) { | |
return $this->checkFile($name); | |
} | |
} |