Let’s dial it up to 11

So. It’s been a few months since I last posted here. I decided that the best way to sharpen my cyber skills would be to start treating my home environment like an enterprise one. In approaching this thought experiment, I thought:

“What key functions would I have in a production, enterprise network that I don’t have here?”

I have an IDS (Snort) but there are some holes:

  • Vulnerability scanning
  • Log aggregation
  • Centralized identity management
  • Endpoint protection
  • Etc.

In thinking through things, I decided I’ll tackle these one at a time. First things first, let’s get some log aggregation going.

After doing some research, I decided that the open source version of Graylog would be my choice for this function on my pseudo-production network. I thought about running this on my OpenBSD router/firewall, but decided that the stack necessary would just overwhelm the machine. Therefore I spun up a virtual host in my hosting environment of choice (DigitalOcean) and started installing / configuring things.

I decided to run Ubuntu 18.04 LTS for the core OS on the virtual machine and followed this tutorial to get Graylog up and running. Once I had the core server running, I decided to figure out how to get log data pushed to it. Since I want everything I do to be open source, I figured that rSyslog would be my best approach. It appeared to be native (or nearly native) on most of the operating systems I run and integrated nicely with Graylog.

I added a “Syslog UDP” Graylog input on a high numbered port on my server, used UFW to open a hole for the traffic and then started researching the arcane syntax of the /etc/rsyslog.conf file that would be necessary to work this bit of magic and get my log messages pushed to my aggregator. I figured it out in about 30 seconds but thought – “No way. It can’t be that easy!” and dug around for a while until I decided to just try it. Here is the incredibly complex piece of syntax you have to use:

*.* @your.graylog-server.example.com:1234

Where the single at sign means to use RDP, the 1234 is the port you are running the Graylog input listener on and “your.graylog-server.example.com” is the FQDN of your Graylog server. No kidding, it’s that easy!

Slug that in as the last line in /etc/rsyslog.conf on a Linux box, restart the rsyslog service:

sudo systemctl restart rsyslog

and you are cooking with gas. I’ve still not cracked the code with OpenBSD, but with all of my other ‘nix boxes, it’s dead simple. Now to tackle Windows (yes, I have a few Windows machines).

For Windows, the common wisdom on the Internet says you should use nxLog for the listener on the Windows box and you should ship the log data over to Graylog as a GELF format. After installing a GELF UDP input listener on Graylog and playing around for a while, I ended up with the following configuration file for nxLog that worked:

Panic Soft
#NoFreeOnExit TRUE

define ROOT     C:\Program Files (x86)\nxlog
define CERTDIR  %ROOT%\cert
define CONFDIR  %ROOT%\conf
define LOGDIR   %ROOT%\data
define LOGFILE  %LOGDIR%\nxlog.log
LogFile %LOGFILE%

Moduledir %ROOT%\modules
CacheDir  %ROOT%\data
Pidfile   %ROOT%\data\nxlog.pid
SpoolDir  %ROOT%\data

<Extension _syslog>
    Module      xm_syslog
</Extension>

<Extension _charconv>
    Module      xm_charconv
    AutodetectCharsets iso8859-2, utf-8, utf-16, utf-32
</Extension>

<Extension _exec>
    Module      xm_exec
</Extension>

<Extension _fileop>
    Module      xm_fileop

    # Check the size of our log file hourly, rotate if larger than 5MB
    <Schedule>
        Every   1 hour
        Exec    if (file_exists('%LOGFILE%') and \
                   (file_size('%LOGFILE%') >= 5M)) \
                    file_cycle('%LOGFILE%', 8);
    </Schedule>

    # Rotate our log file every week on Sunday at midnight
    <Schedule>
        When    @weekly
        Exec    if file_exists('%LOGFILE%') file_cycle('%LOGFILE%', 8);
    </Schedule>
</Extension>

<Extension _gelf>
    Module      xm_gelf
</Extension>

<Input eventlog>
    Module  im_msvistalog
</Input>

<Output out>
    Module      om_udp
    Host        your.graylog-server.example.com
    Port        1234
    OutputType  GELF
</Output>

<Route 1>
    Path eventlog => out
</Route>

Make sure to put in your FQDN for your Graylog server and the port number you are running your GELF input on.

At this point, I logged into each machine on my network and the log messages started flowing smoothly! Just for fun I set up an email alert capability and set some thresholds on failed root logins for the ‘nix boxes to let me know if anything funky is happening.

Next up – vulnerability scanning!