14 KiB
Security
Introduction
This page details notes on how to ensure that we develop secure SilverStripe applications. See our "Release Process on how to report security issues.
SQL Injection
The coding-conventions help guard against SQL injection attacks but still require developer diligence: ensure that any variable you insert into a filter / sort / join clause has been escaped.
See http://shiflett.org/articles/sql-injection.
Automatic escaping
SilverStripe automatically escapes data in SQL statements wherever possible,
through database-specific methods (see [api:Database->addslashes()]).
For [api:MySQLDatabase], this will be [mysql_real_escape_string()](http://de3.php.net/mysql_real_escape_string).
- Most
[api:DataList]accessors (see escaping note in method documentation) - DataObject::get_by_id()
- DataObject::update()
- DataObject::castedUpdate()
- DataObject->Property = 'val', DataObject->setField('Property','val')
- DataObject::write()
- DataList->byID()
- Form->saveInto()
- FormField->saveInto()
- DBField->saveInto()
Data is escaped when saving back to the database, not when writing to object-properties.
Example:
:::php
// automatically escaped/quoted
$members = Member::get()->filter('Name', $_GET['name']);
// automatically escaped/quoted
$members = Member::get()->filter(array('Name' => $_GET['name']));
// needs to be escaped/quoted manually
$members = Member::get()->where(sprintf('"Name" = \'%s\'', Convert::raw2sql($_GET['name'])));
Manual escaping
As a rule of thumb, whenever you're creating raw queries (or just chunks of SQL), you need to take care of escaping yourself. See coding-conventions and datamodel for ways to cast and convert your data.
SQLQueryDataObject::buildSQL()DB::query()Director::urlParams()Controller->requestParams,Controller->urlParamsSS_HTTPRequestdata- GET/POST data passed to a form method
Example:
:::php
class MyForm extends Form {
public function save($RAW_data, $form) {
$SQL_data = Convert::raw2sql($RAW_data); // works recursively on an array
$objs = Player::get()->where("Name = '{$SQL_data[name]}'");
// ...
}
}
FormField->Value()- URLParams passed to a Controller-method
Example:
:::php
class MyController extends Controller {
private static $allowed_actions = array('myurlaction');
public function myurlaction($RAW_urlParams) {
$SQL_urlParams = Convert::raw2sql($RAW_urlParams); // works recursively on an array
$objs = Player::get()->where("Name = '{$SQL_data[OtherID]}'");
// ...
}
}
As a rule of thumb, you should escape your data as close to querying as possible. This means if you've got a chain of functions passing data through, escaping should happen at the end of the chain.
:::php
class MyController extends Controller {
/**
* @param array $RAW_data All names in an indexed array (not SQL-safe)
*/
public function saveAllNames($RAW_data) {
// $SQL_data = Convert::raw2sql($RAW_data); // premature escaping
foreach($RAW_data as $item) $this->saveName($item);
}
public function saveName($RAW_name) {
$SQL_name = Convert::raw2sql($RAW_name);
DB::query("UPDATE Player SET Name = '{$SQL_name}'");
}
}
This might not be applicable in all cases - especially if you are building an API thats likely to be customized. If you're passing unescaped data, make sure to be explicit about it by writing phpdoc-documentation and prefixing your variables ($RAW_data instead of $data).
XSS (Cross-Site-Scripting)
SilverStripe helps you guard any output against clientside attacks initiated by malicious user input, commonly known as XSS (Cross-Site-Scripting). With some basic guidelines, you can ensure your output is safe for a specific use case (e.g. displaying a blog post in HTML from a trusted author, or escaping a search parameter from an untrusted visitor before redisplaying it).
See http://shiflett.org/articles/foiling-cross-site-attacks for in-depth information about "Cross-Site-Scripting".
Escaping model properties
[api:SSViewer] (the SilverStripe template engine) automatically takes care of escaping HTML tags from specific
object-properties by casting its string value into a [api:DBField] object.
PHP:
:::php
class MyObject extends DataObject {
private static $db = array(
'MyEscapedValue' => 'Text', // Example value: <b>not bold</b>
'MyUnescapedValue' => 'HTMLText' // Example value: <b>bold</b>
);
}
Template:
:::php
<ul>
<li>$MyEscapedValue</li> // output: <b>not bold<b>
<li>$MyUnescapedValue</li> // output: <b>bold</b>
</ul>
The example below assumes that data wasn't properly filtered when saving to the database, but are escaped before outputting through SSViewer.
Overriding default escaping in templates
You can force escaping on a casted value/object by using an escape type method in your template, e.g. "XML" or "ATT".
Template (see above):
:::php
<ul>
// output: <a href="#" title="foo & &#quot;bar"">foo & "bar"</a>
<li><a href="#" title="$Title.ATT">$Title</a></li>
<li>$MyEscapedValue</li> // output: <b>not bold<b>
<li>$MyUnescapedValue</li> // output: <b>bold</b>
<li>$MyUnescapedValue.XML</li> // output: <b>bold<b>
</ul>
Escaping custom attributes and getters
Every object attribute or getter method used for template purposes should have its escape type defined through the static $casting array. Caution: Casting only applies when using values in a template, not in PHP.
PHP:
:::php
class MyObject extends DataObject {
public $Title = '<b>not bold</b>'; // will be escaped due to Text casting
$casting = array(
"Title" => "Text", // forcing a casting
'TitleWithHTMLSuffix' => 'HTMLText' // optional, as HTMLText is the default casting
);
public function TitleWithHTMLSuffix($suffix) {
// $this->Title is not casted in PHP
return $this->Title . '<small>(' . $suffix. ')</small>';
}
}
Template:
:::php
<ul>
<li>$Title</li> // output: <b>not bold<b>
<li>$Title.RAW</li> // output: <b>not bold</b>
<li>$TitleWithHTMLSuffix</li> // output: <b>not bold</b>: <small>(...)</small>
</ul>
Note: Avoid generating HTML by string concatenation in PHP wherever possible to minimize risk and separate your presentation from business logic.
Manual escaping in PHP
When using customise() or renderWith() calls in your controller, or otherwise forcing a custom context for your template, you'll need to take care of casting and escaping yourself in PHP.
The [api:Convert] class has utilities for this, mainly Convert::raw2xml() and Convert::raw2att() (which is
also used by XML and ATT in template code).
PHP:
:::php
class MyController extends Controller {
private static $allowed_actions = array('search');
public function search($request) {
$htmlTitle = '<p>Your results for:' . Convert::raw2xml($request->getVar('Query')) . '</p>';
return $this->customise(array(
'Query' => Text::create($request->getVar('Query')),
'HTMLTitle' => HTMLText::create($htmlTitle)
));
}
}
Template:
:::php
<h2 title="Searching for $Query.ATT">$HTMLTitle</h2>
Whenever you insert a variable into an HTML attribute within a template, use $VarName.ATT, no not $VarName.
You can also use the built-in casting in PHP by using the obj() wrapper, see datamodel .
Escaping URLs
Whenever you are generating a URL that contains querystring components based on user data, use urlencode() to escape the user data, not Convert::raw2att(). Use raw ampersands in your URL, and cast the URL as a "Text" DBField:
PHP:
:::php
class MyController extends Controller {
private static $allowed_actions = array('search');
public function search($request) {
$rssRelativeLink = "/rss?Query=" . urlencode($_REQUEST['query']) . "&sortOrder=asc";
$rssLink = Controller::join_links($this->Link(), $rssRelativeLink);
return $this->customise(array(
"RSSLink" => Text::create($rssLink),
));
}
}
Template:
:::php
<a href="$RSSLink.ATT">RSS feed</a>
Some rules of thumb:
- Don't concatenate URLs in a template. It only works in extremely simple cases that usually contain bugs.
- Use Controller::join_links() to concatenate URLs. It deals with query strings and other such edge cases.
Filtering incoming HTML from TinyMCE
In some cases you may be particularly concerned about which HTML elements are addable to Content via the CMS.
By default, although TinyMCE is configured to restrict some dangerous tags (such as script tags), this restriction
is not enforced server-side. A malicious user with write access to the CMS might create a specific request to avoid
these restrictions.
To enable server side filtering using the same whitelisting controls as TinyMCE, set the HtmlEditorField::$sanitise_server_side config property to true.
Cross-Site Request Forgery (CSRF)
SilverStripe has built-in countermeasures against CSRF identity theft for all form submissions. A form object
will automatically contain a SecurityID parameter which is generated as a secure hash on the server, connected to the
currently active session of the user. If this form is submitted without this parameter, or if the parameter doesn't
match the hash stored in the users session, the request is discarded.
You can disable this behaviour through [api:Form->disableSecurityToken()].
It is also recommended to limit form submissions to the intended HTTP verb (mostly GET or POST)
through [api:Form->setStrictFormMethodCheck()].
Casting user input
When working with $_GET, $_POST or Director::urlParams variables, and you know your variable has to be of a
certain type, like an integer, then it's essential to cast it as one. Why? To be sure that any processing of your
given variable is done safely, with the assumption that it's an integer.
To cast the variable as an integer, place (int) or (integer) before the variable.
For example: a page with the URL paramaters mysite.com/home/add/1 requires that ''Director::urlParams['ID']'' be an
integer. We cast it by adding (int) - ''(int)Director::urlParams['ID']''. If a value other than an integer is
passed, such as mysite.com/home/add/dfsdfdsfd, then it returns 0.
Below is an example with different ways you would use this casting technique:
:::php
public function CaseStudies() {
// cast an ID from URL parameters e.g. (mysite.com/home/action/ID)
$anotherID = (int)Director::urlParam['ID'];
// perform a calculation, the prerequisite being $anotherID must be an integer
$calc = $anotherID + (5 - 2) / 2;
// cast the 'category' GET variable as an integer
$categoryID = (int)$_GET['category'];
// perform a byID(), which ensures the ID is an integer before querying
return CaseStudy::get()->byID($categoryID);
}
The same technique can be employed anywhere in your PHP code you know something must be of a certain type. A list of PHP cast types can be found here:
(int),(integer)- cast to integer(bool),(boolean)- cast to boolean(float),(double),(real)- cast to float(string)- cast to string(array)- cast to array(object)- cast to object
Note that there is also a 'SilverStripe' way of casting fields on a class, this is a different type of casting to the standard PHP way. See casting.
Filesystem
Don't allow script-execution in /assets
As all uploaded files are stored by default on the /assets-directory, you should disallow script-execution for this folder. This is just an additional security-measure to making sure you avoid directory-traversal, check for filesize and disallow certain filetypes.
Example configuration for Apache2:
<VirtualHost *:80>
...
<LocationMatch assets/>
php_flag engine off
Options -ExecCGI -Includes -Indexes
</LocationMatch>
</VirtualHost>
If you are using shared hosting or in a situation where you cannot alter your Vhost definitions, you can use a .htaccess file in the assets directory. This requires PHP to be loaded as an Apache module (not CGI or FastCGI).
/assets/.htaccess
php_flag engine off
Options -ExecCGI -Includes -Indexes
Don't allow access to .yml files
Yaml files are often used to store sensitive or semi-sensitive data for use by SilverStripe framework (for instance, configuration and test fixtures).
You should therefore block access to all yaml files (extension .yml) by default, and white list only yaml files you need to serve directly.
See Apache and Nginx installation documentation for details specific to your web server