Tag Archives: DNS

Migrate from Sophos UTM to pfSense part 1

I’ve been using a Sophos UTM virtual appliance as my main firewall / threat manager appliance for about two years now. I’ve had some strange issues with this solution off and on but for the most part it worked. The number of odd issues has begun to build, though.

Recently it decided to randomly drop some connections even though logs showed no dropped packets. The partial connections spanned across various networks and devices. I never did figure out what was wrong. After two days of furiously investigating (including disconnecting all devices from the network), the problem went away completely on its own with no action on my part. It was maddening – enough to drive me to pfSense.

As of version 2.2 pfSense can be fully virtualized in Xen, thanks to FreeBSD 10.1. This allowed me the option to migrate. Below are the initial steps I’ve taken to move to pfSense.

Features checklist

I am currently using the following functions in Sophos UTM. My goal is to move these functions to equivalents in pfSense:

  • Network firewall
  • Web Application Firewall, also known as a reverse proxy.
  • NTP server
  • PPPOE client
  • DHCP server
  • DNS server
  • Transparent proxy for content filtering and reporting
  • E-mail server / SPAM protection
  • Intrusion Detection system
  • Anti-virus
  • SOCKS proxy
  • Remote access portal (for downloading VPN configurations, etc)
  • Citrix Xenserver support (for live migration etc)
  • Log all events to a syslog server
  • VPN server
  • Daily / weekly / monthly e-mail reports on bandwidth usage, CPU, most visited sites, etc.

I haven’t migrated all of these function over to pfSense which is why this article is only Part 1. Here is what I have done so far.

Xenserver support

Installing xen tools is fairly straightforward thanks to this article. It’s simply a matter of dropping to a shell on your pfSense VM to install and enable xen tools

pkg install xe-guest-utilities
echo "xenguest_enable=\"YES\"" >> /etc/rc.conf.local
ln -s /usr/local/etc/rc.d/xenguest /usr/local/etc/rc.d/xenguest.sh 
service xenguest start

PPPoE client

The wizard works fine for configuring PPPOE, however I experienced some very strange issues with internet speed. Downstream would be fine but upstream would be incredibly slow. Another symptom was NAT / port forwarding appearing not to work at all.

It turns out the issue was pfSense’s virtualized status. There is a bug in the virtio driver that handles virtualized networking. You have to disable all hardware offloading on both the xenserver hypervisor and the pfSense VM to work around the bug. Details on how to do this can be found here. After that fix was implemented, speed and performance went back to normal.

DNS server

To get this working like it did in Sophos you have to disable the default DNS resolver service and enable the DNS forwarder service instead. Once DNS forwarder is enabled, check the box “register DHCP leases in DNS” so that DHCP hostnames come through to clients.

Syslog

Navigate to Status / system logs / settings tab and  tick “Send log messages to remote syslog server” and fill out the appropriate settings.

Note for Splunk users: the Technology Add-on for parsing pfsense logs expects the sourcetype to equal pfsense (not syslog). Create a manual input for logs coming from pfsense so it’s tagged as pfsense and not syslog (thanks to this post for the solution on how to get the TA to work properly.)

VPN

OpenVPN – wizard ran fine. Install OpenVPN Client Export utility package for easy exporting to clients. Once package is installed go to VPN / OpenVPN and you will see a new tab – Client Export.

Note you will need to create a user and check the “create certificate” checkbox or add a user certificate to existing user by going to System / User manager, Editing the user and clicking the plus next to User Certificates. The export utility will only show users that have valid certificates attached to them. If no users have valid certificates the Client Export tab will be blank.

Firewall

One useful setting to note is to enable NAT reflection. This allows you to access NATed resources as if you were outside the network, even though you are inside it. Do this by going to System / Advanced and clicking on the Firewall / NAT tab. Scroll halfway down to find the Network Address Translation section. Change NAT reflection mode for port forwards to Enable (Pure NAT)

It’s also very helpful to configure host and port aliases by going to Firewall / Aliases. This is roughly equivalent to creating Network and Host definitions in Sophos. When you write firewall rules you can simply use the alias instead of writing out hosts IPs and ports.

So far so good

This is the end of part 1. I’ve successfully moved the following services from Sophos UTM to pfSense:

  • Network firewall
  • PPPOE client
  • Log all events to a syslog server
  • VPN server
  • NTP server
  • DHCP server
  • DNS server
  • Xenserver support

I’m still working on moving the other services over. I’ve yet to find a viable alternative to the web application firewall but I haven’t given up yet.

Get geolocation info in Splunk with iplocation

Splunk 6 has many awesome new features, one of which is built-in IP geolocation. No longer do you have to manually lookup up city, state, and country when investigating logs – Splunk will do that for you. This page has the details.

For example, if I want my x_forwarded_for IP addresses to have geolocation, I tack this at the end of my query:

| iplocation x_forwarded_for | stats count by x_forwarded_for City Region Country

The fields iplocation can produce are:

  • City
  • Continent
  • Country
  • lat
  • lon
  • MetroCode
  • Region
  • Timezone

You can combine this query with DNS lookups (as detailed here) for a more complete picture of your data.

<search query> | iplocation x_forwarded_for | lookup dnslookup clientip as x_forwarded_for OUTPUT clienthost as hostname | stats count by x_forwarded_for City Region Country hostname

Neat.

Fix DNS issues after Yosemite upgrade

My wife’s macbook pro started behaving strangely after upgrading to Yosemite from Mavericks. The initial upgrade went smoothly but over time certain applications began to quit working. The Pandora desktop client suddenly could never connect. Tunnelbick completely broke no matter what I did. Dnslookups all were fine but pings hung forever, eventually saying they couldn’t resolve a hostname.

It turns out that Yosemite changed the way Mac OSX resolves DNS records from mDNSresponder to dnsdiscoveryd. The issue I had only happened from and upgrade – clean installs didn’t have the issue

The fix for this madness, taken from here, is to remove a few network configuration files and reboot.

First, disconnect from any networks you’re connected to. Then, go to /Library/Preferences/SystemConfiguration/ and remove the following files (if they exist)

com.apple.airport.preferences.plist

com.apple.network.identification.plist
com.apple.wifi.message-tracer.plist

NetworkInterfaces.plist

preferences.plist

After removing those files, reboot. That should fix your problem! (At least, it did for me.)

Perform DNS lookups on Splunk fields

I recently came across a very handy command in Splunk, the lookup command. Thanks to this website I was able to learn how to use the lookup command to give me more relevant results. Instead of Splunk listing a bunch of IP addresses, it now returns a column with everything it could resolve. Seeing resolved domain names alongside IP addresses gives much more meaning to the data.

The command is as follows:

<search> | lookup dnslookup clientip as <IP Field> OUTPUT clienthost as <Resolved Hostname>
  • <search> is your original search
  • <IP Field> is the field which contains the IP addresses you want to do name lookups on
  • <Resolved Hostname> is the name of the column which will contain your resolved hostnames.

You can order your search results in a table if you do the above command before your stats or table command. The example below is to parse some firewall logs from a single source host and perform lookups on them.

<search> | lookup dnslookup clientip as dstip OUTPUT clienthost as Resolved_hostname | stats count by dstip Resolved_hostname dstport proto action

Be careful when using the stats command, though. If they IP address is local it will have a blank resolved hostname, which will exclude it from the stats table.

Sophos UTM returns NXDOMAIN for valid domain names

This issue took me a while to figure out. It’s actually been an issue for a while but I didn’t notice it until XBMC became Kodi. XBMC moved their domain name to kodi.tv and suddenly I was unable to access their site at all.

An nslookup returns NXDOMAIN immediately; however, querying a different server, say Google’s DNS, would return a valid address.

After scratching my head for weeks I came across this post which outlines the exact same problem – any .tv domains are instantly not resolved. I didn’t notice it until XBMC moved to kodi.tv because I don’t visit .tv domains.

The culprit: static DNS entries without a fully qualified domain name. I have plenty of these, and in this case, I have a computer named simply “tv” which Sophos translates into an internal DNS zone; Consequently it doesn’t even bother querying other DNS servers for anything ending in .tv.

The fix: make sure you have fully qualified domain names for all of your static DNS entries. This best practice will save you headaches in the long run.

Configure Sophos UTM to forward e-mail for internal clients

If you’re in a situation like mine you have an ISP which stubbornly blocks port 25. You can get around this by using SSL/TLS of course but configuring each server can be a pain. The solution, in my case, is to turn my UTM into an e-mail relay server and simply have each node point to it for SMTP.

The process wasn’t as straightforward as I had hoped. Below are the steps to accomplish this:

First, enable the SMTP proxy by going to E-mail Protection / SMTP.

Next, go to the Relaying tab and configure allowed relay hosts. For my setup I went to the Host-based relay section and added each individual host that I want to have use my UTM for e-mail relaying.

Lastly, you must configure your UTM to send e-mails out to your ISP’s mail relay since by default the UTM tries to send e-mails out itself on port 25, which in my case is blocked. Do this by going to the Advanced tab and scrolling down to smart host settings. Configure the mail relay server, credentials, and port required there.

That part was fairly straightforward; however the spam protection feature of the UTM was preventing any messages sent to the UTM from being sent to the internet.

After much weeping, wailing and gnashing of teeth (including adding an SPF record for my domain) I discovered that the solution was to ensure that outgoing mail shows the node’s name in the From: field. If your server’s name is server, the from should always be server@yourdomain.org. I haven’t dug into why, but oh well! It works.