Advanced Usage¶
Storing ACL Data for Persistence¶
The Zend\Permissions\Acl
component was designed in such a way that it does not require any particular backend technology
such as a database or cache server for storage of the ACL data. Its complete PHP implementation enables
customized administration tools to be built upon Zend\Permissions\Acl\Acl
with relative ease and flexibility. Many
situations require some form of interactive maintenance of the ACL, and Zend\Permissions\Acl\Acl
provides methods for
setting up, and querying against, the access controls of an application.
Storage of ACL data is therefore left as a task for the developer, since use cases are expected to vary widely
for various situations. Because Zend\Permissions\Acl\Acl
is serializable, ACL objects may be serialized with PHP‘s
serialize() function, and the results may be stored anywhere the developer should desire, such as a file,
database, or caching mechanism.
Writing Conditional ACL Rules with Assertions¶
Sometimes a rule for allowing or denying a role access to a resource should not be absolute but dependent upon
various criteria. For example, suppose that certain access should be allowed, but only between the hours of 8:00am
and 5:00pm. Another example would be denying access because a request comes from an IP address that has been
flagged as a source of abuse. Zend\Permissions\Acl\Acl
has built-in support for implementing rules based on whatever
conditions the developer needs.
Zend\Permissions\Acl\Acl
provides support for conditional rules with Zend\Permissions\Acl\Assertion\AssertionInterface
. In order to
use the rule assertion interface, a developer writes a class that implements the assert()
method of the
interface:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | class CleanIPAssertion implements Zend\Permissions\Acl\Assertion\AssertionInterface
{
public function assert(Zend\Permissions\Acl $acl,
Zend\Permissions\Acl\Role\RoleInterface $role = null,
Zend\Permissions\Acl\Resource\ResourceInterface $resource = null,
$privilege = null)
{
return $this->_isCleanIP($_SERVER['REMOTE_ADDR']);
}
protected function _isCleanIP($ip)
{
// ...
}
}
|
Once an assertion class is available, the developer must supply an instance of the assertion class when assigning
conditional rules. A rule that is created with an assertion only applies when the assertion method returns
TRUE
.
1 2 3 4 | use Zend\Permissions\Acl\Acl;
$acl = new Acl();
$acl->allow(null, null, null, new CleanIPAssertion());
|
The above code creates a conditional allow rule that allows access to all privileges on everything by everyone, except when the requesting IP is “blacklisted.” If a request comes in from an IP that is not considered “clean,” then the allow rule does not apply. Since the rule applies to all roles, all resources, and all privileges, an “unclean” IP would result in a denial of access. This is a special case, however, and it should be understood that in all other cases (i.e., where a specific role, resource, or privilege is specified for the rule), a failed assertion results in the rule not applying, and other rules would be used to determine whether access is allowed or denied.
The assert()
method of an assertion object is passed the ACL, role, resource, and privilege to which the
authorization query (i.e., isAllowed()
) applies, in order to provide a context for the assertion class to
determine its conditions where needed.