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Archive for March, 2012

Securing a GWT application with AOP

March 12th, 2012 No comments

AOP can be a good solution to protect the business methods in an application developed with (or without) GWT.
If we have a method called displayCustomerData(…) and we want to make sure only a certain category of users can call it, for instance the category MANAGER, then AOP can come to the rescue.

I used AspectJ and Spring AOP to implement that. One should not be surprised to notice a tight integration of AOP in Spring since the spec lead for AspectJ is Adrian Coyler, who is also one of the main Spring committers.

0) First, add the needed dependencies with Maven :

<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-aop</artifactId>
	<version>3.0.6.RELEASE</version>
</dependency>

<!-- ASPECTJ dependencies -->
<!-- ******************** -->			
<dependency>
	<groupId>org.aspectj</groupId> 
	<artifactId>aspectjrt</artifactId>
	<version>1.6.12</version> 
</dependency>
							
<dependency>
	<groupId>aspectj</groupId>
	<artifactId>aspectjweaver</artifactId>
	<version>1.5.4</version>
</dependency>	

1) Then create your own annotation

package com.myproject.aop;
import java.io.Serializable;

public enum RoleEnumDto implements Serializable {
	MANAGER, SUPERVISER, BASIC_USER;
}

package com.myproject.aop;
import java.io.Serializable;

@Retention(RetentionPolicy.RUNTIME)
@Target( { ElementType.METHOD })
@Inherited
public @interface AuthorizedRoles {

	RoleEnumDto[] value();
}


2) Then add the AspectJ and Spring dependencies


<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop" 
    xsi:schemaLocation="http://www.springframework.org/schema/beans   
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd     
       http://www.springframework.org/schema/aop  
       http://www.springframework.org/schema/aop/spring-aop-3.0.xsd ">	
	
	<!-- Enable the @AspectJ support. -->
	<aop:aspectj-autoproxy/>

	<bean id="checkAuthorizedRoles" class="com.myproject.aop.CheckAuthorizedRoleAspect"   />

</beans>

3) Then develop the aspect, which is a class annotated with @Aspect.


package com.myproject.aop;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.apache.log4j.Logger;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.core.annotation.Order;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;


@Order(0)
@Aspect
public class CheckAuthorizedRoleAspect {
	
private static final Logger log = Logger.getLogger(CheckAuthorizedRoleAspect.class);
	
/**
 * The pointcut expression where to bind the advice
 */
@Pointcut("  @annotation(com.myproject.AuthorizedRoles)")
private void businessMethods() {		
	log.debug("Entering businessMethods()");		
}// the pointcut signature
	
	
 @Before("businessMethods()")
 public void checkAuthorizedAdvice(JoinPoint joinPoint, AuthorizedRoles authorizedRoles) throws    ForbiddenAccessException {
  log.debug("Entering checkAuthorizedAdvice()");
  log.debug(joinPoint.getSignature().getName());

  // Do some role checking 
  // 1. Proceed the method if the user has the required role
  if (...) {
          return pjp.proceed();
  //2. Throw an exception if not.
  else {
  throw new ForbiddenAccessException ("The user is not allowed to call this method");
  }
 }
	 		 
}

The @Order(0) annotation is useful in the case where a jointpoint can be intercepted by several aspects.
The annotation AuthorizedRoles is passed as a parameter to the checkAuthorizedAdvice(…) method, which is the advice.
The pointcut expression matches all methods annotated with the AuthorizedRoles annotation.

4) Finally, add the annotation to the business method you want to restrict the access to. This business method can be called by the implementation of an RPC service for instance :


@Override
@Transactional(rollbackFor = SomeException.class)
@AuthorizedRoles( { RoleEnumDto.MANAGER, RoleEnumDto.SUPERVISER })
public Customer displayCustomerData(long id) throws NotFoundException {
		...
}

Pretty easy and pretty powerful.

Categories: AOP, AspectJ, GWT, Spring, Spring AOP Tags: