Struts

Status
'''Content to be finalized. First draft'''

Overview
Struts is an Apache framework aimed at simplifying the creation of dynamic web applications in Java.

Struts is built on a MVC architecture, which means the application is arranged into 3 primary types of code. These are know as a Model, View and Controller. The Model defines the structure of your data being processed. The View defines everything that a end user can see. The controller take the model as submitted from the page, performs business logic on the data, then decides what view should be responsible for displaying the result.

I will not spend any more time talking about the architecture of struts. If you would like to have more information on that topic, I suggest going to the official website.

Validation
The Struts Validation Framework is the primary method of validating a struts based application. Struts validation consists of a few elements to be setup. To properly use Struts validation your application should have the following...

 A validator-rules.xml file in the WEB-INF folder. A validator.xml in the WEB-INF folder. All ActionForms should extend org.apache.struts.validator.ValidatorForm or org.apache.struts.validator.ValidatorActionForm instead of org.apache.struts.action.ActionForm. The commons-validator.jar in WEB-INF. This can be obtained here. The Validator plug-in should be enabled in struts-config.xml     

Examples
Struts Validation in an ActionForm

Struts Validation in validator.xml using an ActionForm

Struts Validation in validator.xml using a DynaValidatorForm

Output Sanitation
Output sanitation is the process of ensuring that your output does not contain HTML or XML specific characters. So, for example a '<' becomes '&amp;lt;'. This should be used as a secondary XSS prevention method. Primary method of prevention should be validation. Luckily some Struts tags include output sanitation by default. If you're tag is not here, then you should implement sanitation manually.

Sanitized tags

 * bean:Write (may be overwritten by setting filter to false)
 * html:Hidden
 * html:Messages (if the value is of type String)
 * html:Multibox
 * html:OptionsCollection (may be overwritten by setting filter to false)
 * html:Options (may be overwritten by setting filter to false)
 * html:Option (you must set filter to true)
 * html:Radio
 * html:TextArea
 * html:File
 * html:Hidden
 * html:Password
 * html:Text

Roles
In the struts-config.xml configuration file it is possible to specify a roles attribute, a comma-delimited list of security role names that are allowed access to the ActionMapping object. This is pretty much all that you get out of the box.

 <forward name="success" path="article.jsp"/>

Custom Action Mappings
It is possible to implement far more complex security models if you extend the action mappings.

TODO: Lots more detail here.

Error Handling
TODO: Put some info here

Common errors and vulnerabilities
Form Field Without Validator

Plug-in Framework Not In Use

Unused Validation Form

Unvalidated Action Form

Validator Turned Off

Validator Without Form Field

Form Does Not Extend Validation Class

Erroneous validate Method

Duplicate Validation Forms

Auditing Tools
Struts XSLT Viewer