Authenticating in PHP using LDAP through Active Directory

Importing a whole library seems inefficient when all you need is essentially two lines of code...

$ldap = ldap_connect("ldap.example.com");if ($bind = ldap_bind($ldap, $_POST['username'], $_POST['password'])) {  // log them in!} else {  // error message}

You would think that simply authenticating a user in Active Directory would be a pretty simple process using LDAP in PHP without the need for a library. But there are a lot of things that can complicate it pretty fast:

• You must validate input. An empty username/password would pass otherwise.
• You should ensure the username/password is properly encoded when binding.
• You should be encrypting the connection using TLS.
• Using separate LDAP servers for redundancy in case one is down.
• Getting an informative error message if authentication fails.

It's actually easier in most cases to use a LDAP library supporting the above. I ultimately ended up rolling my own library which handles all the above points: LdapTools (Well, not just for authentication, it can do much more). It can be used like the following:

use LdapTools\Configuration;use LdapTools\DomainConfiguration;use LdapTools\LdapManager;$domain = (new DomainConfiguration('example.com'))    ->setUsername('username') # A separate AD service account used by your app    ->setPassword('password')    ->setServers(['dc1', 'dc2', 'dc3'])    ->setUseTls(true);$config = new Configuration($domain);$ldap = new LdapManager($config);if (!$ldap->authenticate($username, $password, $message)) {    echo "Error: $message";} else {    // Do something...}

The authenticate call above will:

• Validate that neither the username or password is empty.
• Ensure the username/password is properly encoded (UTF-8 by default)
• Try an alternate LDAP server in case one is down.
• Encrypt the authentication request using TLS.
• Provide additional information if it failed (ie. locked/disabled account, etc)

There are other libraries to do this too (Such as Adldap2). However, I felt compelled enough to provide some additional information as the most up-voted answer is actually a security risk to rely on with no input validation done and not using TLS.

I do this simply by passing the user credentials to ldap_bind().

http://php.net/manual/en/function.ldap-bind.php

If the account can bind to LDAP, it's valid; if it can't, it's not. If all you're doing is authentication (not account management), I don't see the need for a library.