Drupal 7 Module Development

Node Access
This code will grant anonymous users with the proper permission access to View
content as if they were authenticated.
Security warning!
Be very careful with any code that provides this type of privilege
escalation. For instance, if we failed to check that $op == 'view' we
would be giving anonymous users permission to View, Update and
Delete all content on the site!
The above example is great, but what if we want to restrict custom roles to only view
content created by people in those roles? That is, we might need to remove the ability
to View content as an authenticated user. With a slight modification to the code, we
can do so:
/**
* Implement hook_node_grants_alter().
*/
function role_access_extend_node_grants_alter(&$grants, $account, $op)
{
// We only act on the 'view' operation.
// If our grants is not present, do nothing.
if ($op != 'view' || !isset($grants['role_access'])) {
return;
}
// Check the permission.
$access = user_access('view role access as authenticated user');
// Get the defined role id for 'authenticated user'.
$rid = DRUPAL_AUTHENTICATED_RID;
// Check authenticated users.
if ($account->uid > 0) {
// Users with more than one role should have 'authenticated users'
// removed.
if (count($account->roles) > 1 && in_array($rid, $grants['role_
access']) && !$access) {
// The grants array is in the order $grants[$realm][$key] =>
// $value, so flip it, unset, and flip back.
$grants['role_access'] = array_flip($grants['role_access']);
unset($grants['role_access'][$rid]);
$grants['role_access'] = array_flip($grants['role_access']);
}
}
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