spring-security how ACL grants permissions - permissions

Question

I'm currently integrating springs-security into our new web application stack. We will need to be able to grant permissions for a user or role to access a specific object or all objects of a certain type. However that's one thing I didn't really get when working through documentations and examples:
Does an ACL only grant permissions to a user/role for a single object or does it do that for the entire type? As I understand it, domain object means the type but the examples and tutorials seem like they assign permissions to specific objects. Am I just confused or can I do both? If not, how do I do the other?
Thanks!

Answer 1

With spring-security you can do both. It's possible because spring-security supports the so called permission rules - within the spring-security terminology they call it permission evaluators. Permission rules encompass ACL, but also you can secure instances of objects when they're in a certain state...etc.
This is how it works:
You need to extend the PermissionEvaluator - this allows you to have super custom logic for determining access rights - you can check the type of the object or check for a particular id, or check if the user invoking the method is the user that created the object, etc.:
public class SomePermissionsEvaluator implements PermissionEvaluator {
#Override
public boolean hasPermission(Authentication authentication, Object targetDomainObject, Object permission) {
if (permission.equals("do_something") &&
/*authentication authorities has the role A*/) {
return true
} else if (permission.equals("do_something_else") &&
/*authentication authorities has the role B*/) {
return /*true if targetDomainObject satisfies certain condition*/;
}
return false;
}
#Override
public boolean hasPermission(Authentication authentication,
Serializable targetId, String targetType, Object permission) {
throw new UnsupportedOperationException();
}
}
Now that you have a security rule, you need to apply it through annotations:
#PreAuthorize("hasRole('SOME_ROLE_OR_RIGHT') and" +
" hasPermission(#someDomainObject, 'do_something')")
public void updateSomeDomainObject(SomeDomainObject someDomainObject) {
// before updating the object spring-security will check the security rules
}
In order for this to work the security annotations should be enabled in the applicationContext.xml:
<global-method-security secured-annotations="enabled" pre-post-annotations="enabled">
<expression-handler ref="expressionHandler"/>
</global-method-security>
<beans:bean id="expressionHandler" class="org.springframework.security.access.expression.method.DefaultMethodSecurityExpressionHandler">
<beans:property name="permissionEvaluator">
<beans:bean id="permissionEvaluator" class="com.npacemo.permissions.SomePermissionsEvaluator"/>
</beans:property>
</beans:bean>