Writing Your Spring Security Expression Language Annotation
Spring security expression language is very useful. It helps secure your service/web methods with one line of code.
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Join For FreeSpring 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");
}
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