RE: Domain Controller Discovery in PHP

["Jason" <networkadmin@xxxxxxxxxxxx>]

-----Original Message-----
From: Robert Cummings [mailto:robert@xxxxxxxxxxxxx] 
Sent: 27 September 2010 19:38
To: Jason
Cc: 'PHP General'
Subject: Re:  Domain Controller Discovery in PHP

On 10-09-27 11:26 AM, Jason wrote:
> Hi Rob,
>
> I believe you should be able to do this with nothing more than DNS (this is how Windows clients do it).
>
> Once you have the DNS domain of the machine you're on (_SERVER["USERDNSDOMAIN"]), query for SRV records called the following:
>
> Name: _ldap._tcp.dc._msdcs.<machine domain name>
>
> That should return one or more records in the answer, each one will be the FQDN of a domain controller.
>
> Additional info from the horses mouth: http://support.microsoft.com/kb/247811

Hi Jason,

Thanks for the info. I don't actually have that server field (maybe 
because the article is for windows 2000), but maybe I can use your info 
to get to the next step anyways.

Cheers,
Rob.
-- 


Hi Rob,

I've checked a couple of windows machines (which I admit I had assumed you were running php on) and the ENV variable "USERDNSDOMAIN" is definitely what you need. If your php is running on linux, you'll need to find out the target windows domain some other way (user input/config file maybe?).

The article is a Win2k based one - there is a link to the XP one in the top-right corner. However I read both and things haven't changed from a DNS point of view.

Here's a code snippet for you (run on my network from a windows workstation)...

<?php
# assume $_SERVER["USERDNSDOMAIN"] is equal to "xxx.local".

print_r( dns_get_record("_ldap._tcp.dc._msdcs.".$_SERVER["USERDNSDOMAIN"],DNS_SRV) );
?>


And the output (edited for obvious reasons):


Array
(
    [0] => Array
        (
            [host] => _ldap._tcp.dc._msdcs.xxx.local
            [type] => SRV
            [pri] => 0
            [weight] => 100
            [port] => 389
            [target] => dc2.xxx.local
            [class] => IN
            [ttl] => 545
        )
 
    [1] => Array
        (
            [host] => _ldap._tcp.dc._msdcs.xxx.local
            [type] => SRV
            [pri] => 0
            [weight] => 100
            [port] => 389
            [target] => dc1.xxx.local
            [class] => IN
            [ttl] => 545
        )
 
)


HTH
J



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