I have more than 10years of development experience. My expertise is in Java EE technology, object-oriented application development, and use of open source frameworks. In recent years, I mainly worked in development projects of Java EE applications in Weblogic platform with Oracle database. I primarily involved in framework development and architectural design in these projects. Boris is a DZone MVB and is not an employee of DZone and has posted 13 posts at DZone. You can read more from them at their website. View Full User Profile

Writing Your Spring Security Expression Language Annotation

08.21.2012
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Spring security expression language is very useful. It helps secure your service/web methods with one line of code. It supports @PreAuthorize and @Secured. In the next three posts, I will talk about how to add custom behaviour to the @PreAuthorize annotation. 

Part 1 - Customize "hasPermission()" expression 
Part 2 - Add new customize method security expression 
Part 3 - Override default behaviour of spring security expression (e.g. hasRole() , permitAll() ...)

In this post, I will discuss how to add custom rules for permission-checking in your application. This is somewhat similar to what is described in Sold Craft's post. You can reference it for more details.

 Step 1: Add configuration in your spring security xml file.

You should first add the DefaultMethodSecurityExpressionHandler. It will instantiate a default MethodSecurityExpressionRoot which provides you all the default security expression (e.g. isAuthenticated(), isAnonymous(),etc.). 

Besides, you have to add a permissionEvaluator for that ExpressionHandler. If you are using spring security ACL, you could use AclPermissionEvaluator. In our case, we would create a BasePermissionEvaluator as our permission evaluator. You will see in step 2 that we would define custom rules in this permission evaluator.

 <sec:global-method-security pre-post-annotations="enabled">

  <sec:expression-handler ref="expressionHandler"/>
</sec:global-method-security>
 
<bean id="expressionHandler" class="org.springframework.security.access.expression.method.DefaultMethodSecurityExpressionHandlerr">
    <property name="permissionEvaluator" ref="permissionEvaluator"/>
</bean>  
 
<bean id="permissionEvaluator" class="org.borislam.security.BasePermissionEvaluator"/>

 Step 2: Create your PermissionEvaluator class

You must define a class that implements the org.springframework.security.access.PermissionEvaluator. You have to override the hasPermission() method and define custom rules in this class.

In my example, the user object contains a HashMap which stores the permissions of the user. I will check the permission String against this Hashmap. This HashMap is populated during login by a filter. This part will not be skipped in this example. 

For simplicity I just ignore the targetDomainObject parameter in my example. By using the targetDomainObject, you can further define security rules on certain domain objects in your application.

 public class BasePermissionEvaluator implements PermissionEvaluator{

 @Override
 public boolean hasPermission(Authentication authentication, Object targetDomainObject, Object permission) {
  boolean hasPermission = false;
  if ( authentication != null &&  permission instanceof String){
 
   //implement the permission checking of your application here   
   //you can just check if the input permission is within your permission list
 
   //In my example, the user object contains a HashMap which stored the permission of the user.
   //The HashMap<String, PrivilegeResult> is populated during using login by filter. This will not be shown in this example 
 
   User user = SecurityUtil.getUserCredential();
   HashMap<String, PrivilegeResult> pMap =user.getPrivilegeMap();
   PrivilegeResult privResult = pMap.get(permission); 
   hasPermission =  privResult.isAllowAccess();
 
  } else {
   hasPermission =false; 
  }
  return hasPermission;
 }
 
 @Override
 public boolean hasPermission(Authentication authentication,
   Serializable targetId, String targetType, Object permission) {
    throw new RimtimeException("Id and Class permissions are not supperted by this application");
 }
}

 Step 3: Example usage

You could simply add your @PreAuthorize("hasPermission()") to secure your method.

@PreAuthorize("hasPermission(#user, 'allowDoSomething')")
 public String doSomething()
 {
  //do something
  System.out.println("Do something");
 } 

 Original Post

 

Published at DZone with permission of Boris Lam, author and DZone MVB.

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