Word of advice: Escaping LDAP filter values in PHP

Second “word of advice” for PHP programmers is kind of related (and also referenced in) to the previous post in the series.

We are going to cover escaping of LDAP values in LDAP queries initiated from PHP.

Introduction to the problem

Honestly, often it seems that LDAP support in PHP alone is a second class citizen. Sure, things seem to be much better in its semi-official Zend Framework. But as it goes in PHP world, a lot of developers don’t use Zend Framework, and way too many don’t use any framework since the platform lacked proper official or semi-official one for more than a decade.

Even now in the days when the biggest PHP developer’s dilemma is which application framework to use for their projects, most of the 3rd party frameworks lack any level of advanced LDAP support. Developers are then still forced to cope with (for the PHP developers’ standards) low-level LDAP support if they need LDAP functionality in their apps.

That being said, I have to mention that you shouldn’t have to worry about anything on this issue if you’re using Zend Framework properly. Zend_Ldap_Filter_Abstract class engages escapeValue() method, which is used exactly for this – escaping of values used in LDAP queries.

Although basically a database, LDAP really is, and you realize it first time you have to connect to it, whole different story from your usual relational or noSQL databases you’re used to work with. That being said, even the most basic PHP LDAP API separates modification from read-only function to access it. It means that if you use LDAP only to authenticate your users and read their data (meaning: you don’t update anything intentionally through ldap_modify or some other such function) you shouldn’t face the worse result of “LDAP injection”. Worse case scenario in such environment would be attacker’s succesful logins which usually wouldn’t succeed. Bad enough, but no damage to your data.

That doesn’t mean you should approach issue of LDAP queries with unconsciousness. Hence this article. :-) Continue reading “Word of advice: Escaping LDAP filter values in PHP”