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”

Word of advice: PHP authentication against LDAP service

I see this problem a lot in various PHP scripts which are connecting to LDAP service.. Problem is not isolated to PHP environment only, but for some odd reason, PHP developers in majority end in this pitfall, while developers on using other popular programming languages usually handle this issue better.

Introduction to the problem

LDAP service authentication often poses a challenge to the developers who are engaging in LDAP-dependent services development for the first time. In general, your input data will be username and password, while for the succesful authentication against LDAP you need different info: DN (distinguished name) and a password.

So, in order to be able to authenticate user credentials against LDAP service, you have to make a relation between username as input variable and DN as a parameter LDAP service expects.

Again, LDAP service is very specific with its approach towards users, passwords and authentication. You might be able to retrieve DN using query such as

…even when your server bind is anonymous. Of course, that depends on the configuration of your LDAP service, but it’s not so rare occurrence that LDAP service allows such basic info as DN to be read through anonymous connections. Should it be allowed is a discussion for some  completely another occasion.

But the problem starts just here. Continue reading “Word of advice: PHP authentication against LDAP service”