Spring MVC accessing Spring Security ConfigAttributes? - spring

Question

I want to produce HTTP Response Body with an error message referencing something like _"missing ... 'CUSTOM_AUTHORITY'"_ in addition to a 403 Forbidden HTTP Status code.
My application is Spring Boot with a Spring-Security-Secured #PreAuthorize method within a Spring-MVC-REST #Controller:
MyController
#Controller
#RequestMapping("/foo")
public FooController{
#PreAuthorize("hasAuthority('CUSTOM_AUTHORITY')")
public Object getSomething(){ ... }
}
GlobalExceptionHandlerResolver
#ControllerAdvice
public class GlobalExceptionHandler {
#ExceptionHandler(AccessDeniedException.class)
#ResponseStatus(HttpStatus.FORBIDDEN)
public Object forbidden(AccessDeniedException exception){ ... }
}
What I want is to expose/inject Collection<ConfigAttribute>. The Spring Security docs reference it.

Answer 1

There doesn't seem to be a straightforward way of accomplishing this. The AccessDecisionManager (which is AffirmativeBased) throws the AccessDeniedException with none of the information you want. So if you want to "expose/inject" the Collection<ConfigAttribute>, you'll want to provide your own AccessDecisionManager that throws a custom exception that holds the ConfigAttributes.
The easiest way to do this could be to wrap the default AccessDecisionManager with your own and delegate method calls to it:
#Configuration
#EnableGlobalMethodSecurity(prePostEnabled=true)
CustomMethodSecurityConfig extends GlobalMethodSecurityConfiguration
#Override
protected AccessDecisionManager accessDecisionManager() {
AccessDecisionManager default = super.accessDecisionManager();
MyCustomDecisionManager custom = new CustomDecisionManager(default);
}
}
You could define your custom AccessDecisionManager as follows:
public class MyCustomDecisionManager implements AccessDecisionManager {
private AccessDecisionManager default;
public MyCustomDecisionManager(AccessDecisionManager acm) {
this.default = acm;
}
#Override
public void decide(Authentication authentication, Object object, Collection<ConfigAttribute> configAttributes) throws AccessDeniedException, InsufficientAuthenticationException{
try {
default.decide(authentication, object, configAttributes)
} catch(AccessDeniedException ex) {
throw new CustomAccessDeniedException(ex.getMessage(), configAttributes);
}
}
// other methods delegate to default
}
Now whenever access is denied, you will get an exception that holds the Collection<ConfigAttribute>.
Your custom exception could look like this:
public class CustomAccessDeniedException extends AccessDeniedException {
private Collection<ConfigAttribute> attributes;
public CustomAccessDeniedException(String message, Collection<ConfigAttribute> attr) {
super(message);
this.attributes = attr;
}
public Collection<ConfigAttribute> getAttributes() {
return this.attributes;
}
}
Now your #ExceptionHandler could handle your CustomAccessDeniedException and have access to the ConfigAttributes.
HOWEVER...
I am not sure that will provide you with the error message you wanted. The ConfigAttribute interface only has one method:
String getAttribute();
And the javadoc states:
If the ConfigAttribute cannot be expressed with sufficient precision as a String, null should be returned.
Since we can't rely on the interface method, how you deal with each ConfigAttribute will be heavily dependent on the type of the particular object you're dealing with.
For example, the ConfigAttribute that corresponds to #PreAuthorize("hasAuthority('CUSTOM_AUTHORITY')") is PreInvocationExpressionAttribute, and to print something that resembles what you want, you could do:
PreInvocationExpressionAttribute attr = (PreInvocationExpressionAttribute)configAttribute;
String expressionString = attr.getAuthorizeExpression().getExpressionString();
System.out.println(expressionString); // "hasAuthority('CUSTOM_AUTHORITY')"
That's the major drawback. Also, you would get ALL the ConfigAttributes, not necessarily the ones that failed.