Determine the modules that permissions belong to.
An associative array in the format $permission => $module.
function user_permission_get_modules() {
$permissions = array();
foreach (module_implements('permission') as $module) {
$perms = module_invoke($module, 'permission');
foreach ($perms as $key => $value) {
$permissions[$key] = $module;
}
}
return $permissions;
}