Resolved it myself. 
For the record, I just needed that for customers, so I changed the actual MD5 crypt in 
Kernel/System/CustomerAuth/DB.pm
and
Kernel/System/CustomerUser/DB.pm
(its just one line)
from 
$CryptedPw = unix_md5_crypt( $Pw, $Login );
to
$CryptedPw = md5_hex($Pw);

(also added, use Digest::MD5 qw(md5_hex);).

If anyone thinks I've missed something, let me know.

-sv
On Tue, Jan 12, 2010 at 11:37 PM, Sagy Volkov <sagyvolkov@gmail.com> wrote:
Hi,

I need to get OTRS (2.4.5) to somehow change the method in Frontend::Customer::Auth to support another option, (not just plain,MD5, crypt) but also support Digest:: MD5, i.e.

use Digest::MD5 qw(md5_hex);
my testpass=md5_hex("password");

I know in terms of security its less secured, but because of integration from another system who keeps password (in php) with plain MD5, I need to change the way OTRS save/compare customer passwords.

Have anyone done it in the past? any thoughts?

Best Regards,

-sv