Struts

Status

Content to be finalised. First draft

Introduction

This article describes the web security implications for the Struts MVC framework, how Struts helps in securing your web applications and where special attention is needed. It will not describe the internal details of Struts.

Architecture

The framework provides its own web Controller component. This Controller acts as a bridge between the application's Model and the web View. When a request is received, the Controller invokes an Action class. The Action class interacts with the Model to examine or update the application's state. The framework provides an ActionForm class to help transfer data between Model and View.

Components

Action

• No distinction is made between HTTP GET and POST method. Both methods are mapped to the same Action execute method.

ActionForm

• The ActionForm is much like a java bean.
• There is at least one action for each action that contains post data.
• It defines the fields that are passed to the action.
• It has pointers to or contains the validation that occurs before control makes it to the action.
• It is very important that you validate every field no matter how certain you may be about it's inability to cause problems.

Validation in the ActionForm

• struts-config.xml

    <struts-config>
        <form-beans>
            <form-bean name="logonForm" type="net.jcj.LogonForm"/>
        </form-beans>
        <action-mappings>
            <action path="/Logon" forward="/pages/Logon.jsp"/>
            <action path="/LogonSubmit" type="app.jcj.LogonAction" name="logonForm" 
               scope="request" validate="true" input="/pages/Logon.jsp">
                <forward name="success" path="/pages/Welcome.jsp"/>
                <forward name="failure" path="/pages/Logon.jsp"/>
            </action>
        </action-mappings>
        <message-resources parameter="resources.application"/>
    </struts-config>

• net.jcj.LogonForm

package net.jcj;

import javax.servlet.http.HttpServletRequest;
import org.apache.struts.action.*;

public class LogonForm extends ActionForm
{
  private String userId = null;
  private String password = null;

  public void setUserId (String userId){
    this.userId = userId ;
  }

  public String getUserId(){
    return this.userId ;
  }

  public void setPassword (String password){
    this.password = password;
  }

  public String getPassword(){
    return this.password;
  }

    /**
     * Resets all properties to their default values.
     */
    public void reset(ActionMapping mapping, HttpServletRequest request) {
      this.userId = null;
      this.password = null;
    }

    /**
     * Validates the form.  Returns a list of action
     * Of course in a production environment, your rules would be far more strict than this.
     */
  public ActionErrors validate( 
      ActionMapping mapping, HttpServletRequest request ) {
      ActionErrors errors = new ActionErrors();
      
      if( getUserId() == null || getUserId().length() < 1 ) {
        errors.add("userId",new ActionMessage("error.userid.required"));
      }
      if( getPassword() == null || getPassword().length() < 1 ) {
        errors.add("password",new ActionMessage("error.password.required"));
      }

      return errors;
  }

}

Validation framework

• Integration with commons validator
• A bit awkward, but it gets the job done.

• struts-config.xml

    <struts-config>
      <form-beans>
          <form-bean name="logonForm" type="net.jcj.LogonForm"/>
      </form-beans>
      <action-mappings>
          <action path="/Logon" forward="/pages/Logon.jsp"/>
          <action path="/LogonSubmit" type="app.jcj.LogonAction" name="logonForm" 
             scope="request" validate="true" input="/pages/Logon.jsp">
              <forward name="success" path="/pages/Welcome.jsp"/>
              <forward name="failure" path="/pages/Logon.jsp"/>
          </action>
      </action-mappings>
      <message-resources parameter="resources.application"/>
        <plug-in className="org.apache.struts.validator.ValidatorPlugIn">
        <set-property property="pathnames" value="/technology/WEB-INF/validator-rules.xml, /WEB-INF/validation.xml"/>
      </plug-in>
    </struts-config>

• net.jcj.LogonForm

package net.jcj;

import javax.servlet.http.HttpServletRequest;
import org.apache.struts.action.*;

public class LogonForm extends ActionForm
{
  private String userId = null;
  private String password = null;

  public void setUserId (String userId){
    this.userId = userId ;
  }

  public String getUserId(){
    return this.userId ;
  }

  public void setPassword (String password){
    this.password = password;
  }

  public String getPassword(){
    return this.password;
  }

    /**
     * Resets all properties to their default values.
     */
    public void reset(ActionMapping mapping, HttpServletRequest request) {
      this.userId = null;
      this.password = null;
    }

    /**
     * Validates the form.  Returns a list of action
     * Of course in a production environment, your rules would be far more strict than this.
     */
  public ActionErrors validate( 
      ActionMapping mapping, HttpServletRequest request ) {
      return new ActionErrors();
  }

}

• validation.xml

<form-validation>
  <formset>
    <form name="logonForm">
      <field property="userId" depends="required">
        <arg0 key="prompt.userId"/>
      </field>
      <field property="password" depends="required">
        <arg0 key="prompt.password"/>
      </field>
    </form>
  </formset>
</form-validation>

Security

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.

<action
     roles="administrator,contributor"
     path="/article/Edit"
     parameter="org.article.FindByArticle"
     name="articleForm"  
     scope="request">
       <forward
             name="success"
             path="article.jsp"/>
</action>

Extending action mappings

If you extend the action mappings, you will be able to satisfy much more complicated security schemes.