Derby Startup Script

Posted on August 15th, 2008 in General,Linux System Administration by Brandon

I was surprised when installing Derby for a customer, that it only provided a command to start derby running as a server from the terminal. I guess most users likely used it in embedded mode where the application runs derby itself. But surely there are people who would like the multi-user features of having it run as a standalone server.

Google searches didn’t find any suitable startup scripts either, so I wrote my own and figured it might be useful for others. Anybody who is interested can download it here. Simply save it as /etc/init.d/derby and create a ‘derby’ user before using it. It assumes that derby is installed in /usr/local/derby, so be sure to modify the first few lines to match your exact configuration.

Vacation (AutoReply) Message with Virtual Users and Postfix

Posted on August 8th, 2008 in General,Linux System Administration,Mail by Brandon

I’ve previously written about both Virtual Mail users, and about enabling vacation messages for postfix. The next step was to get vacation working with virtual users.

My first thought was to try and make the sendmail ‘vacation’ program work with virtual users, but after digging into that a bit, it looked like more trouble than it was worth. I remembered that PostfixAdmin had some kind of support for this, so decided to check it out, which proved a much more promising solution.

PostfixAdmin ships with a perl-based script that can be piped an email message and then will send an auto-reply to the sender. The script is able to grab a customized subject and message body from a MySQL database and then reply to senders as appropriate. It also keeps track of who it has auto-replied to so that each sender only gets one auto-reply in a given length of time.

The instructions for implementing it can be found at http://postfixadmin.svn.sourceforge.net/viewvc/postfixadmin/trunk/VIRTUAL_VACATION/INSTALL.TXT?view=markup. I found the documentation to be fairly straightforward.

Essentially, when a user enables the auto-reply, it adds an email address to the aliases table that points to user#domain@autoreply.yourdomain.com. You then configure postfix to send everything to the ‘autoreply.yourdomain.com’ domain to the vacation script, which then can read the original recipient’s address and respond as desired.

I now have this working on our hosted mail solution, so that RoundSphere mail customers now have auto-reply functionality. In addition, I made an addition to the webmail application (RoundCube) so that users can modify their vacation message themselves instead of having to have a mail administrator do it through postfixadmin.

Testing for Vulnerable Caching Name Servers

Posted on August 8th, 2008 in General,Linux System Administration,Security by Brandon

Most of the technical community has probably heard of the recently found DNS weakness.  The basic premise is that if a recursive nameserver doesn’t use sufficently random source ports when making recursive queries, it can be vulnerable to an attacker who is trying to poisen the cache, or fill it with incorrect data.

I’ve now heard reports about it from various news sources who make it sound much more drastic than it actually is.   Granted, it is a serious flaw, but fortunately most companies with any desire for security use SSL, which provides an additional layer for identity verification.  Also, for most any company with an IT staff, patching the DNS server with the required fixes should be a fairly trivial task.   The most important servers to be fixed are those run by ISPs and Datacenters, both of which should have their servers fixed by now.

Tools for testing your DNS servers are fairly easy to come by.  dns-oarc.net has a web-based test, although I don’t know how it discovers your DNS Servers.  For windows users, you can run ‘nslookup’ like this:

C:\Documents and Settings\Brandon>nslookup
Default Server:  cns.manassaspr.va.dc02.comcast.net
Address:  68.87.73.242

> set type=TXT
> porttest.dns-oarc.net
Server:  cns.manassaspr.va.dc02.comcast.net
Address:  68.87.73.242

Non-authoritative answer:
porttest.dns-oarc.net   canonical name = porttest.y.x.w.v.u.t.s.r.q.p.o.n.m.l.k.
j.i.h.g.f.e.d.c.b.a.pt.dns-oarc.net
porttest.y.x.w.v.u.t.s.r.q.p.o.n.m.l.k.j.i.h.g.f.e.d.c.b.a.pt.dns-oarc.net
text =

        "68.87.73.245 is GREAT: 26 queries in 2.3 seconds from 25 ports with std
 dev 16592"
>

To test from a linux machine, you can use dns-oarc’s test with dig like this:

root@server:~# dig porttest.dns-oarc.net in txt +short
porttest.y.x.w.v.u.t.s.r.q.p.o.n.m.l.k.j.i.h.g.f.e.d.c.b.a.pt.dns-oarc.net.
"72.249.0.34 is GREAT: 26 queries in 1.2 seconds from 26 ports with std dev 20533"

Your are looking for a response that contains GOOD or GREAT. If your results contain something else, you should notify your ISP or Data Center to have them fix their servers.