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Security: Complex Access Controls with Expressions

Security: Complex Access Controls with Expressions

The best solution for handling complex authorization rules is to use the Voter System.

In addition to a role like ROLE_ADMIN, the isGranted() method also accepts an Expression object:

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use Symfony\Component\ExpressionLanguage\Expression;
// ...

public function index()
{
    $this->denyAccessUnlessGranted(new Expression(
        '"ROLE_ADMIN" in roles or (user and user.isSuperAdmin())'
    ));

    // ...
}

In this example, if the current user has ROLE_ADMIN or if the current user object's isSuperAdmin() method returns true, then access will be granted (note: your User object may not have an isSuperAdmin() method, that method is invented for this example).

This uses an expression and you can learn more about the expression language syntax, see The Expression Syntax.

Inside the expression, you have access to a number of variables:

user
The user object (or the string anon if you're not authenticated).
roles
The array of roles the user has, including from the role hierarchy but not including the IS_AUTHENTICATED_* attributes (see the functions below).
object
The object (if any) that's passed as the second argument to isGranted().
token
The token object.
trust_resolver
The AuthenticationTrustResolverInterface, object: you'll probably use the is_*() functions below instead.

Additionally, you have access to a number of functions inside the expression:

is_authenticated
Returns true if the user is authenticated via "remember-me" or authenticated "fully" - i.e. returns true if the user is "logged in".
is_anonymous
Equal to using IS_AUTHENTICATED_ANONYMOUSLY with the isGranted() function.
is_remember_me
Similar, but not equal to IS_AUTHENTICATED_REMEMBERED, see below.
is_fully_authenticated
Similar, but not equal to IS_AUTHENTICATED_FULLY, see below.
has_role
Checks to see if the user has the given role - equivalent to an expression like 'ROLE_ADMIN' in roles.

The is_remember_me() and is_authenticated_fully() functions are similar to using IS_AUTHENTICATED_REMEMBERED and IS_AUTHENTICATED_FULLY with the isGranted() function - but they are not the same. The following controller snippet shows the difference:

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use Symfony\Component\ExpressionLanguage\Expression;
use Symfony\Component\Security\Core\Authorization\AuthorizationCheckerInterface;
// ...

public function index(AuthorizationCheckerInterface $auth)
{
    $access1 = $auth->isGranted('IS_AUTHENTICATED_REMEMBERED');

    $access2 = $auth->isGranted(new Expression(
        'is_remember_me() or is_fully_authenticated()'
    ));
}

Here, $access1 and $access2 will be the same value. Unlike the behavior of IS_AUTHENTICATED_REMEMBERED and IS_AUTHENTICATED_FULLY, the is_remember_me() function only returns true if the user is authenticated via a remember-me cookie and is_fully_authenticated only returns true if the user has actually logged in during this session (i.e. is full-fledged).

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.