Revision as of 18:45, 3 December 2010

Overview

OWASP CSRFGuard implements a variant of the synchronizer token pattern to mitigate the risk of CSRF attacks. In order to implement this pattern, CSRFGuard must offer the capability to place the CSRF prevention token within the HTML produced by the protected web application. CSRFGuard 3 provides developers more fine grain control over the injection of the token. Developers can inject the token in their HTML using either a JSP tag library or a dynamic JavaScript servlet. CSRFGuard no longer intercepts and modifies the HttpServletResponse object as was done in previous releases. The currently available token injection strategies are designed to make the integration of CSRFGuard more feasible and scalable within current enterprise web applications. The purpose of this article is to describe the token injection strategies offered by OWASP CSRFGuard 3.

JSP Tag Library

OWASP CSRFGuard 3 exposes a JSP tag library providing developers more fine grain control over token injection. The library exposes JSP tags that allow access to the token name, the token value, and the token name value pair delimited by an equals (=) sign. In order to make use of the tag library, ensure the Owasp.CsrfGuard.jar file is found within the target application's classpath. For example, the Owasp.CsrfGuard.Test application places the OWASP CSRFGuard jar file within the WebContent/WEB-INF/lib directory. After placing the library in the classpath, developers can reference the tags in JSP pages using predefined URI reference. The following JSP code snippet imports the tag library and makes it available using the prefix "csrf":

<%@ taglib uri="http://www.owasp.org/index.php/Category:OWASP_CSRFGuard_Project/Owasp.CsrfGuard.tld" prefix="csrf" %>

Display Token Name

The OWASP CSRFGuard token name can be obtained through the token-name tag. The token-name tag is useful when injecting the CSRFGuard token name in a non-query string context. Consider the following code snippet taken from the Owasp.CsrfGuard.Test application. This code makes use of the token-name tag to reference the token name in the name attribute of a hidden input field:

<form name="test1" action="protect.html">
     <input type="text" name="text" value="text"/>
     <input type="submit" name="submit" value="submit"/>
     <input type="hidden" name="<csrf:token-name/>" value="<csrf:token-value/>"/>
</form>

Display Token Value

The OWASP CSRFGuard token value can be obtained through the token-value tag. The token-value tag is useful when injecting the CSRFGuard token value in a non-query string context. Consider the following code snippet taken from the Owasp.CsrfGuard.Test application. This code makes use of the token-value tag to reference the token value in the value attribute of a hidden input field:

<form name="test1" action="protect.html">
     <input type="text" name="text" value="text"/>
     <input type="submit" name="submit" value="submit"/>
     <input type="hidden" name="<csrf:token-name/>" value="<csrf:token-value/>"/>
</form>