php-doc-en/reference/mongo/security.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->

<section xml:id="mongo.security" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <title>Security</title>

 <section>
  <title>Request Injection Attacks</title>
  <para>
   If you are passing <literal>$_GET</literal> parameters to your queries, make
   sure that they are cast to strings first.  Users can insert associative
   arrays in GET requests, which could then become unwanted $-queries.
  </para>

  <para>
   A fairly innocuous example: suppose you are looking up a user's information
   with the request <emphasis>http://www.example.com?username=bob</emphasis>.
   Your application does the query
   <literal>$collection->find(array("username" => $_GET['username']))</literal>.
  </para>

  <para>
   Someone could subvert this by getting
   <emphasis>http://www.example.com?username[$ne]=foo</emphasis>, which PHP
   will magically turn into an associative array, turning your query into
   <literal>$collection->find(array("username" => array('$ne' => "foo")))</literal>,
   which will return all users not named "foo" (all of your users, probably).
  </para>

  <para>
   This is a fairly easy attack to defend against: make sure $_GET's parameters
   are the type you expect before you send them to the database (cast them to
   strings, in this case).
  </para>

  <para>
   Note that this type of attack can be used with any databases interation that
   locates a document, including updates, upserts, find-and-modifies, and
   removes.
  </para>

  <para>
   Thanks to <link xlink:href="&url.mongodb.injection;">Phil</link> for pointing this out.
  </para>

  <para>
   See <link xlink:href="&url.mongodb.dochub.security;">the main documentation</link>
   for more information about SQL-injection-like issues with MongoDB.
  </para>
 </section>

 <section>
  <title>Script Injection Attacks</title>
  <para>
   If you are using JavaScript, make sure that any variables that cross the PHP-
   to-JavaScript boundry are passed in the <literal>scope</literal> field of
   <classname>MongoCode</classname>, not interpolated into the JavaScript
   string. This can come up when using <function>MongoDB::execute</function>,
   <literal>$where</literal> clauses, MapReduces, group-bys, and any other time
   you may pass JavaScript into the database.
  </para>
  <note>
   <para>
    MapReduce ignore the <literal>scope</literal> field of
    <classname>MongoCode</classname>, but there is a <literal>scope</literal>
    option on the command that can be used instead.
   </para>
  </note>
  <para>
   For example, suppose we have some JavaScript to greet a user in the database
   logs.  We could do:
  </para>
  <programlisting role="php">
<![CDATA[
<?php

// don't do this!

$username = $_POST['username'];
$db->execute("print('Hello, $username!');");

?>
]]>
  </programlisting>
  <para>
   However, what if a malicious user passes in some JavaScript?
  </para>
  <programlisting role="php">
<![CDATA[
<?php

// don't do this!

// $username is set to "'); db.users.drop(); print('"
$db->execute("print('Hello, $username!');");

?>
]]>
  </programlisting>
  <para>
   Now MongoDB executes the JavaScript string
   <literal>"print('Hello, '); db.users.drop(); print('!');"</literal>.
   This attack is easy to avoid: use <literal>scope</literal> to pass
   variables from PHP to JavaScript:
  </para>
  <programlisting role="php">
<![CDATA[
<?php

$scope = array("user" => $username);
$db->execute(new MongoCode("print('Hello, '+user+'!');", $scope));

?>
]]>
  </programlisting>
  <para>
   This adds a variable <literal>user</literal> to the JavaScript scope. Now if
   someone tries to send malicious code, MongoDB will harmlessly print
   <literal>Hello, '); db.dropDatabase(); print('!</literal>.
  </para>

  <para>
   Using <literal>scope</literal> helps prevent malicious input from being
   executed by the database.  However, you must make sure that your code does
   not turn around and execute the input anyway! For example, never use the
   JavaScript <literal>eval</literal> function on user input:
  </para>
  <programlisting>
<![CDATA[
<?php

// don't do this!

// $jsShellInput is "db.users.drop();"
$scope = array("input" => $jsShellInput);
$db->execute(new MongoCode("eval(input);", $scope));

?>
]]>
  </programlisting>
  <para>
   Always use <literal>scope</literal> and never allow the database to execute
   user input as code.
  </para>
 </section>
</section>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->