Problems with secure bind to Active Directory using PHP

Question

I seem to be unable to use php to securely bind to Active Directory. Unencrypted connections work fine. Using other clients are able to securely bind, e.g. connecting using LDAPAdmin over SSL. What is the problem here? Is there some LDAP SSL module that I'm missing? How to securely bind to the server using php?

I noticed from phpinfo() that cURL has support for ldap/ldaps - what is a good example on utilizing this to perform secure bind in php? Is this a viable workaround?

phpinfo();

ldap
LDAP Support    enabled
RCS Version     $Id: ldap.c 293036 2010-01-03 09:23:27Z sebastian $
Total Links     0/unlimited
API Version     3001
Vendor Name     OpenLDAP
Vendor Version  20421
SASL Support    Enabled 

Attempting to bind to an Active Directory server using PHP Version 5.3.2-1ubuntu4.7 from Ubuntu 10.04 repo

$username = 'user';
$password = 'passwd';
$account_suffix = '@example.com';
$hostnameSSL = 'ldaps://ldap.example.com:636';
$hostnameTLS = 'ldap.example.com';
$portTLS = 389;

ldap_set_option(NULL, LDAP_OPT_DEBUG_LEVEL, 7);

// Attempting fix from http://www.php.net/manual/en/ref.ldap.php#77553
putenv('LDAPTLS_REQCERT=never');

####################
# SSL bind attempt #
####################
// Attempting syntax from http://www.php.net/manual/en/function.ldap-bind.php#101445
$con =  ldap_connect($hostnameSSL);
if (!is_resource($con)) trigger_error("Unable to connect to $hostnameSSL",E_USER_WARNING);

// Options from http://www.php.net/manual/en/ref.ldap.php#73191
if (!ldap_set_option($con, LDAP_OPT_PROTOCOL_VERSION, 3))
{
    trigger_error("Failed to set LDAP Protocol version to 3, TLS not supported",E_USER_WARNING);
}
ldap_set_option($con, LDAP_OPT_REFERRALS, 0);

if (ldap_bind($con,$username . $account_suffix, $password)) die('All went well using SSL');
ldap_close($con);

####################
# TLS bind attempt #
####################
$con =  ldap_connect($hostnameTLS,$portTLS);
ldap_set_option($con, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($con, LDAP_OPT_REFERRALS, 0);
$encrypted = (ldap_start_tls($con));
if ($encrypted) ldap_bind($con,$username . $account_suffix, $password); // Unecrypted works, but don't want logins sent in cleartext
ldap_close($con);

#####################
# SASL bind attempt #
#####################
$con =  ldap_connect($hostnameTLS,$portTLS);
ldap_set_option($con, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($con, LDAP_OPT_REFERRALS, 0);
ldap_sasl_bind($con, NULL, $password, 'DIGEST-MD5', NULL, $username. $account_suffix);
ldap_close($con);

All of the above fails. Errors from log:

ldap_create
ldap_url_parse_ext(ldaps://ldap.example.com:636)
ldap_bind_s
ldap_simple_bind_s
ldap_sasl_bind_s
ldap_sasl_bind
ldap_send_initial_request
ldap_new_connection 1 1 0
ldap_int_open_connection
ldap_connect_to_host: TCP ldap.example.com:636
ldap_new_socket: 27
ldap_prepare_socket: 27
ldap_connect_to_host: Trying 1.1.1.1:636
ldap_pvt_connect: fd: 27 tm: -1 async: 0
ldap_open_defconn: successful
ldap_send_server_request
ldap_result ld 0x215380c0 msgid 1
wait4msg ld 0x215380c0 msgid 1 (infinite timeout)
wait4msg continue ld 0x215380c0 msgid 1 all 1
** ld 0x215380c0 Connections:
* host: ldap.example.com  port: 636  (default)
  refcnt: 2  status: Connected
  last used: Thu Mar 10 11:15:53 2011


** ld 0x215380c0 Outstanding Requests:
 * msgid 1,  origid 1, status InProgress
   outstanding referrals 0, parent count 0
  ld 0x215380c0 request count 1 (abandoned 0)
** ld 0x215380c0 Response Queue:
   Empty
  ld 0x215380c0 response count 0
ldap_chkResponseList ld 0x215380c0 msgid 1 all 1
ldap_chkResponseList returns ld 0x215380c0 NULL
ldap_int_select
read1msg: ld 0x215380c0 msgid 1 all 1
ldap_err2string
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP Warning:  ldap_bind() [<a href='function.ldap-bind'>function.ldap-bind</a>]: Unable to bind to server: Can't contact LDAP server in /..test.php on line 28
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP Stack trace:
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP   1. {main}() /..test.php:0
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP   2. ldap_bind() /..test.php:28
ldap_free_request (origid 1, msgid 1)
ldap_free_connection 1 1
ldap_free_connection: actually freed
ldap_create
ldap_err2string
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP Warning:  ldap_start_tls() [<a href='function.ldap-start-tls'>function.ldap-start-tls</a>]: Unable to start TLS: Not Supported in /..test.php on line 37
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP Stack trace:
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP   1. {main}() /..test.php:0
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP   2. ldap_start_tls() /..test.php:37
ldap_create
ldap_sasl_interactive_bind_s: user selected: DIGEST-MD5
ldap_err2string
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP Warning:  ldap_sasl_bind() [<a href='function.ldap-sasl-bind'>function.ldap-sasl-bind</a>]: Unable to bind to server: Not Supported in /..test.php on line 47
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP Stack trace:
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP   1. {main}() /..test.php:0
[Thu Mar 10 11:15:53 2011] [error] [client ::1] PHP   2. ldap_sasl_bind() /..test.php:47

Looking at ssl response:

>> openssl s_client -connect my.example.com:636 -prexit

(...)
SSL handshake has read 5732 bytes and written 443 bytes
---
New, TLSv1/SSLv3, Cipher is RC4-MD5
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : TLSv1
    Cipher    : RC4-MD5
    Session-ID: 111111111111111111111111
    Session-ID-ctx: 
    Master-Key: AAAAAAAAAAAAAAAAAAAAA
    Key-Arg   : None
    Start Time: 1299071105
    Timeout   : 300 (sec)
    Verify return code: 20 (unable to get local issuer certificate)

Results from 'strace php test.php' :

    write(2, "  refcnt: 2  status: Connected\n", 31  refcnt: 2  status: Connected
    ) = 31
    write(2, "  last used: Tue Mar 15 10:59:19"..., 39  last used: Tue Mar 15 10:59:19 2011

    ) = 39
    write(2, "\n", 1
    )                       = 1
    write(2, "** ld 0x954e0b8 Outstanding Requ"..., 38** ld 0x954e0b8 Outstanding Requests:
    ) = 38
    write(2, " * msgid 1,  origid 1, status In"..., 41 * msgid 1,  origid 1, status InProgress
    ) = 41
    write(2, "   outstanding referrals 0, pare"..., 43   outstanding referrals 0, parent count 0
    ) = 43
    write(2, "  ld 0x954e0b8 request count 1 ("..., 45  ld 0x954e0b8 request count 1 (abandoned 0)
    ) = 45
    write(2, "** ld 0x954e0b8 Response Queue:\n", 32** ld 0x954e0b8 Response Queue:
    ) = 32
    write(2, "   Empty\n", 9   Empty
    )               = 9
    write(2, "  ld 0x954e0b8 response count 0\n", 32  ld 0x954e0b8 response count 0
    ) = 32
    write(2, "ldap_chkResponseList ld 0x954e0b"..., 48ldap_chkResponseList ld 0x954e0b8 msgid 1 all 1
    ) = 48
    write(2, "ldap_chkResponseList returns ld "..., 47ldap_chkResponseList returns ld 0x954e0b8 NULL
    ) = 47
    write(2, "ldap_int_select\n", 16ldap_int_select
    )       = 16
    poll([{fd=3, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
    write(2, "read1msg: ld 0x954e0b8 msgid 1 a"..., 37read1msg: ld 0x954e0b8 msgid 1 all 1
    ) = 37
    read(3, "", 8)                          = 0
    write(2, "ldap_err2string\n", 16ldap_err2string
    )       = 16
    write(2, "PHP Warning:  ldap_bind(): Unabl"..., 158PHP Warning:  ldap_bind(): Unable to bind to server: Can't contact LDAP server in

And I do have the /etc/ldap.conf fix with 'TLS_REQCERT never' - even though this fix is for a different error, which gives a fairly clear error message.

Answer 1

What saved my day after reading and trying out solutions from allover the web and SO, was to use a ldaps uri without the port specified in it.

So instead of this: ldaps://example.com:636 I had to use this: ldaps://example.com and it now works like a charm.

I was setting this up on Ubuntu 16.04 with PHP7.3 runing through Nginx and php-fpm.

A full code example:

try{
    $ldapUri = "ldaps://example.com";
    $ldapUsername = 'username';
    $ldapPassword = 'password';
    $ldapConn = ldap_connect($ldapUri);
    if($ldapConn){
        ldap_set_option($ldapConn,LDAP_OPT_NETWORK_TIMEOUT,10);

        if(!ldap_set_option($ldapConn,LDAP_OPT_PROTOCOL_VERSION,3)){
           print 'Failed to set ldap protocol to version 3<br>';
        }
        ldap_set_option($ldapConn, LDAP_OPT_REFERRALS,0);
        $ldapBind = ldap_bind($ldapConn, $ldapUsername, $ldapPass);
        if ($ldapBind) {
           echo "LDAP bind successful...";
           //DO LDAP search and stuff
           ldap_unbind($ldapConn);
        } else {
           echo "LDAP bind failed...";
        }
    }
}catch(Exception $e){
    print($e->getMessage();
}

Answer 2

As my code is working fine with CentOS, I conclude that the problem is not programming specific. I have not been able to get it running in my Ubuntu environment as of yet, but I assume this is a bug in my server software.

Answer 3

I was finally able to get things working on my Windows machine by reading the following PHP bug thread: http://bugs.php.net/bug.php?id=48866

Unfortunately, this is Windows specific but it got me at least going in the right direction now in my testing (I know it should work from PHP now on my web server...so long as I have ldap.conf configured correctly). On Windows with PHP 5.3 I needed to add the ldap.conf file into the root of my C: drive (other examples I had seen online had been placing it in C:\openldap\sysconf which wasn't working).

TLS still doesn't work exactly (it gives me a "unable to start tls: can't contact LDAP server" message), but SSL does appear to be working and I was able to update a password for an account in my test script.

I'm guessing the ldap.conf file just needs to be setup similarly on my web server and I should hopefully be in business (I'm just not sure if the one that's already there is the one I need to modify or if I need to create an additional one). I'll see if I can report back on that front.

Answer 4

Did you see the comment on the PHP.net page about missing permissions on some cert store that does this:

http://de3.php.net/manual/en/function.ldap-connect.php

bleathem 27-Feb-2008 10:30 Everyone is posting about getting ldaps:// working in a WAMP/AD stack, I had a tough time finding how to get it going in RHEL 5.1 (w/ all stock rpms). Good old strace did the trick and helped me find the problem... Turns out php was looking for the CA file in /etc/pki/CA, and I didn't have the correct permissions on the folder. chmod'ing it to 755 solved my "Can't contact LDAP server" message.

So maybe thats your issue too. If not you should give either strace or wireshark a try to catch the syscalls and network transmissions and figure out what goes wrong. One of the two will show it clearly.

Answer 5

this is how i do it:

<?php
    $username = ''; // username to check
    $password = ''; // password to check

/**
 * Is it an Active Directory?
 *
 * <pre>
 * true = yes
 *        set the following values:
 *        SDB_AUTH_LDAP_HOST
 *        SDB_AUTH_LDAP_SSL
 *        SDB_AUTH_LDAP_BASE
 *        SDB_AUTH_LDAP_SEARCH
 *        SDB_AUTH_LDAP_USERDOMAIN
 * false = no, you have to supply an hostname
 *         and configure the following values:
 *         SDB_AUTH_LDAP_HOST
 *         SDB_AUTH_LDAP_PORT
 *         SDB_AUTH_LDAP_SSL
 *         SDB_AUTH_LDAP_BASE
 *         SDB_AUTH_LDAP_SEARCH
 *         SDB_AUTH_LDAP_USERDOMAIN
 * </pre>
 * @see SDB_AUTH_LDAP_HOST
 */
define('SDB_AUTH_IS_AD', true);
/**
 * Domain name of the LDAP Host or of the AD-Domain
 */
define('SDB_AUTH_LDAP_HOST', 'your-domain.tld');
/**
 * LDAP Port?
 *
 * if {@link SDB_AUTH_IS_AD} = true, then the port will be read form DNS.
 */
define('SDB_AUTH_LDAP_PORT', '389');
/**
 * Use LDAPS (true) oder LDAP (false) connection?
 */
define('SDB_AUTH_LDAP_SSL', false);
/**
 * LDAP Base
 */
define('SDB_AUTH_LDAP_BASE', 'CN=Users,DC=your-domain.tld,DC=de');
/**
 * LDAP Search, to find a user
 *
 * %s will be replaced by the username.<br>
 * z.B. CN=%s
 */
define('SDB_AUTH_LDAP_SEARCH', '(&(sAMAccountName=%s)(objectclass=user)(objectcategory=person))');
/**
 * Die LDAP Domain des Benutzers
 *
 * if the username doesnt contain a domain append this domain to it.<br>
 * in case this is empty, nothing will be appended.
 */
define('SDB_AUTH_LDAP_USERDOMAIN', 'your-domain.tld');
/**
 * Path to LDAP Search
 *
 * Will give back better error messages
 * ( leave empty in case you don't want to have it. )
 */
define('SDB_AUTH_LDAP_SEARCHBIN', '/usr/bin/ldapsearch');




        $ldap_error_codes=array(
        '525' => 'Username doesnt exist.',
        '52e' => 'Wrong password.',
        '530' => 'You cannot login at this time.',
        '531' => 'You cannot login from this host.',
        '532' => 'Your password was expired.',
        '533' => 'Your account has been deactivated.',
        '701' => 'Your account was expired.',
        '773' => 'Please set another password (at your workstation) before you login.',
        '775' => 'Your account has been locked.',
        );


  if(SDB_AUTH_LDAP_SSL) $dcs=dns_get_record("_ldaps._tcp.".SDB_AUTH_LDAP_HOST, DNS_SRV); else $dcs=dns_get_record("_ldap._tcp.".SDB_AUTH_LDAP_HOST, DNS_SRV);
  shuffle($dcs);

  $_LDAP_ATTRS=array('cn', 'sn', 'description', 'givenName', 'distinguishedName', 'displayName', 'memberOf', 'name', 'sAMAccountName', 'sAMAccountType', 'objectClass', 'objectCategory');
  if(SDB_AUTH_LDAP_USERDOMAIN!='' && strstr($username, '@')===false) {
        $username=$username.'@'.SDB_AUTH_LDAP_USERDOMAIN;
  }
  $status=array();
  $status['CN']='';
  $status['displayName']='';
  $status['description']='';
  $status['distinguishedName']='';
  $status['groups']=array();
  $status['RC']=array();
  $status['connected']=false;
  $status['user_exists']=false;
  $status['is_in_team']=false;

foreach($dcs as $_LDAP_HOST) {
$_LDAP_PORT=$_LDAP_HOST['port'];
$_LDAP_HOST=$_LDAP_HOST['target'];
// check connection first ( http://bugs.php.net/bug.php?id=15637 )
$sock=@fsockopen($_LDAP_HOST, $_LDAP_PORT, $errno, $errstr, 1);
@fclose($sock);
if($errno!=0) continue;

// then do a "connect"... ( the real connect happens with bind )
$ds=@ldap_connect(( SDB_AUTH_LDAP_SSL ? "ldaps://" : "ldap://" ).$_LDAP_HOST.":".$_LDAP_PORT."/");
ldap_set_option($ds, LDAP_OPT_PROTOCOL_VERSION, 3);
// are we connected? actually, this will always return true
if(is_resource($ds)) {
    $status['connected']=true;
    // login sucessful? actually also connection test
    if(@ldap_bind($ds, $username, $password)) {
        // search
        $sr=ldap_search($ds, SDB_AUTH_LDAP_BASE, sprintf(SDB_AUTH_LDAP_SEARCH, $usernode), $_LDAP_ATTRS);
        // suche successful?
        if(is_resource($sr)) {

            // fetch entries
            $info = ldap_get_entries($ds, $sr);
            if(isset($info['count']) && $info['count']>0) {
                $status['user_exists']=true;
            }
            // close search result
            ldap_free_result($sr);
            $status['CN']=$info[0]['cn'][0];
            $status['description']=$info[0]['description'][0];
            $status['displayName']=$info[0]['displayname'][0];
            $status['distinguishedName']=$info[0]['distinguishedname'][0];
            // is the user in the dexteam?
            for($i=0; $i<$info[0]['memberof']['count']; $i++) {
                $status['groups'][]=$info[0]['memberof'][$i];
                // IS IN TEAM CHECK 
                if(substr($info[0]['memberof'][$i], 0, strlen('CN=DexTeam,'))=='CN=DexTeam,') $status['is_in_team']=true; 
            }

            $status['RC']['code']=ldap_errno($ds);
            $status['RC']['string']=ldap_error($ds);
            ldap_close($ds);
            break;
        }
        else {
            $status['RC']['code']=ldap_errno($ds);
            $status['RC']['string']=ldap_error($ds);
            ldap_close($ds);
            break;
        }
    }
    else {
        $status['RC']['code']=ldap_errno($ds);
        $status['RC']['string']=ldap_error($ds);
        // do we want better error messages?
        if(SDB_AUTH_LDAP_SEARCHBIN!='' && is_executable(SDB_AUTH_LDAP_SEARCHBIN)) {
            $status['RC']['ldapsearchrc']='';
            $status['RC']['ldapsearchtxt']=array();
            exec(SDB_AUTH_LDAP_SEARCHBIN.' -x -H '.escapeshellarg(( SDB_AUTH_LDAP_SSL ? "ldaps://" : "ldap://" ).$_LDAP_HOST.":".$_LDAP_PORT."/").' -D '.escapeshellarg($username).' -w '.escapeshellarg($password).' 2>&1', $status['RC']['ldapsearchtxt'], $status['RC']['ldapsearchrc']);
            if($status['RC']['ldapsearchrc']!=0) {
                if(preg_match("/data ([^, ]+),/", $status['RC']['ldapsearchtxt'][1], $matches)) {
                    if(isset($ldap_error_codes[$matches[1]])) {
                        $status['RC']['code']=$matches[1];
                        $status['RC']['string']=$ldap_error_codes[$matches[1]];
                    }
                }
                unset($status['RC']['ldapsearchrc']);
                unset($status['RC']['ldapsearchtxt']);
            }
        }
        ldap_close($ds);
        break;
    }
}
else {
    continue;
}
}

did you enable the certificate? i know there was a problem, when the certifiacte gets refused. edit the "/etc/ldap/ldap.conf" and add "TLS_REQCERT never"

#
# LDAP Defaults
#
# See ldap.conf(5) for details
# This file should be world readable but not world writable.
#BASE   dc=example,dc=com
#URI    ldap://ldap.example.com ldap://ldap-master.example.com:666
#SIZELIMIT      12
#TIMELIMIT      15
#DEREF          never
TLS_REQCERT never

however, to me it works with ldap and ldaps:

• it might be a configuration issue with the ad configuration. maybe lower certain security limitations...
• OR it might be also a php / ldap lib issue. Try to update to newer versions :)

Answer 6

Does your Active Directory have LDAPS enabled? If so, get the Trusted Root of the CA's key into the trusted root keystore.