feat: improve user impersonation using dedicated voter

config/packages/security.yaml

@@ -22,7 +22,7 @@ security:
             custom_authenticators:
                 - App\Security\BpnAuthenticator
             switch_user:
-                role: ROLE_ADMIN
+                role: CAN_IMPERSONATE
             logout:
                 path: app_security_logout
                 target: app_security_login

src/Security/Voter/ImpersonationVoter.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace App\Security\Voter;
+
+use App\Entity\User;
+use Symfony\Bundle\SecurityBundle\Security;
+use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
+use Symfony\Component\Security\Core\Authorization\Voter\Voter;
+use Symfony\Component\Security\Core\User\UserInterface;
+
+class ImpersonationVoter extends Voter
+{
+    public function __construct(private readonly Security $security)
+    {
+    }
+
+    protected function supports(string $attribute, mixed $subject): bool
+    {
+        return 'CAN_IMPERSONATE' === $attribute && $subject instanceof UserInterface;
+    }
+
+    protected function voteOnAttribute(string $attribute, mixed $subject, TokenInterface $token): bool
+    {
+        $currentUser = $token->getUser();
+        $targetUser = $subject;
+
+        // if the user is anonymous or if the subject is not a user, do not grant access
+        if (!$currentUser instanceof User || !$targetUser instanceof User) {
+            return false;
+        }
+
+        // if the current user is trying to impersonate herself, do not grant access
+        if ($currentUser === $targetUser) {
+            return false;
+        }
+
+        // if the current user is already impersonating, do not grant access
+        if ($this->security->isGranted('IS_IMPERSONATOR')) {
+            return false;
+        }
+
+        // Admin is the only role allowed to impersonate
+        return $this->security->isGranted('ROLE_ADMIN');
+    }
+}