Server Security Tips

Whenever I deploy a new server I always ensure that any flaws which I’ve picked up from my few years of server experience are fixed, leaving the new server as secure as can be and ready for use.

Below are a few tips for keeping your server as secure as can be:

  • Have a secure root password – Use something random and at least 8 characters long
  • Use non-default ports – Change the default port for services commonly targeted by bots or attackers such as SSH
  • Check your logs – Look for authentication failures and put the related IPs in a block or reject rule using iptables
  • Process users – Make sure processes have their own users and aren’t ran as root

More tips will be added once I remember them!

Install EPEL Repository on CentOS 7 (x64)

The simple one line command below will enable the EPEL repository on CentOS 7

rpm -Uvh http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-2.noarch.rpm

Once ran you will see confirmation that it has been installed successfully, that’s it!

Notes

  • You can find out more about the EPEL repository here
  • If you don’t already have a server, I’d strongly recommend starting with DigitalOcean

Icecast PHP Stats

A recent project of mine called Coop Cam uses several live video streams served by an Icecast server at different mount points which works great, but I found there was no real solution to simply display how many viewers were actually watching the live streams.

I put together a basic PHP code that reads the Icecast XML stats file and retrieves the current overall viewers (or listeners as its officially known) of all available mount points.

Code

// get the stats xml file //
$output = file_get_contents('http://admin:[email protected]:8000/admin/stats');

// explode to make the magic happen //   
$listeners = explode('',$output);
$listeners = explode('',$listeners[1]);

// output to the world //
echo "Currently <b>$listeners[0]</b> people are watching the live stream!";

Once you have amended the admin password, server name and port the code above will then connect to your server and read the /admin/stats XML file. From here it will literally pick out the content shown between the <listeners></listeners> tags and that then becomes the $listeners[0] variable, simply place this wherever you want to display the amount of current viewers.

Notes

  • This code may or may not work depending on if your hosting provider allows the file_get_contents function – In my case I use my own dedicated servers and it works without issue, if you have any problems I’m sure I can sort something for you!
  • You can show the amount of sources, file connections and so on by amending the code to reflect the correct tags – A full list of tags can be seen by visiting the youricecastservername.com:8000/admin/stats page
  • You can find a live working example of this script here or actually see it in place here
  • Finally, you can download the script by clicking here

Disable Virtualmin Two-factor Authentication

Virtualmin is constantly being developed and gaining ever useful features, and for a while now has featured two-factor authentication which is great, although what happens if you get locked out of your system? As long as you have SSH or console access then you can follow the steps below to easily get back in.

Disabling two-factor authentication for a single user

  • Get root SSH or console access
  • Edit the file /etc/webmin/miniserv.users, comment out the current line for the user then create a fresh copy above it
  • Remove any mention of “totp” and the long string of characters near the end and save, for example your file should now look like the following:
...
root:x::::::::0:0:::
#root:x::::::::0:0:totp:ZZZZZZZZZZZZZZZZ:
...
  • Restart Webmin and log back in normally

Disabling two-factor authentication entirely

  • Get root SSH or console access
  • Edit the file /etc/webmin/miniserv.conf and find the line “twofactor_provider=totp” and replace with “twofactor_provider=” and save
  • Edit the /etc/webmin/miniserv.users as mentioned above
  • Restart Webmin and log back in normally

Notes

  • I’ve had success with this on Webmin 1.760 running on CentOS 7.0

Encrypted AES VPN tunnel between pfSense 2.3 and Ubiquiti EdgeRouter Lite

I recently retired my Draytek 2830 following a serious security flaw I discovered (that’s another post, stay tuned!) and took the plunge with a rather impressive looking Ubiquiti EdgeRouter Lite.

The other option was a rack mountable TP-Link TL-ER6020 although the maximum NAT throughput was only 180Mbps and it only had 128MB  DDR2 memory and no clear CPU specs, also the web interface looked tired and very restricted. Pound for pound the EdgeRouter was cheaper and has a better spec of anywhere up to and over 600Mbps, 512MB DDR2 memory and Dual‑Core 500 MHz, although it wasn’t rack mountable it was a no brainer with its modern web interface, also did I mention it can process 1 million packets per second?

The EdgeRouter also appeals to my inner nerd  (you can no doubt tell) as you can program it via web interface, command line or console connection and you can remove features you don’t need to boost performance. For example, it may only have 3 gigabit ports, but you can do whatever you like with them! In my case I have it configured as 1 WAN port and the other 2 ports are linked to two seperate LAN’s. I will write a full review when I get chance, but for now just take my word that it is the best router I have ever owned.

Anyway, to business!

Home Network

As before with the Draytek guide my home network is still double NAT’d but there isn’t a speed issue anymore. I do plan to eventually run everything via the EdgeRouter but first I need to install a few additional access points (I’m thinking a couple of airGateway-LR’s hidden in roof spaces will do, powered by PoE obviously!).

In the example below the home network subnet will be 192.168.100.x
and WAN address will be 1.2.3.4

Remote Network

The remote network is the same as before too – a pfSense machine sits at x.1 and deals with traffic to the local network.

In the example below the remote subnet will be 192.168.150.x and WAN address will be 5.6.7.8

Important

  • Each local area network must be on a seperate subnet, otherwise things can quickly get messy and conflict!
  • Make sure you use a secure pre-shared key, anything above 32 characters will do nicely and under no circumstances use the example key!
  • The example details below are fake, replace them with your own details if you want this to work

Configuring pfSense

The guide below lists only the parts you need to change, if the option isn’t listed then leave it as is. Anything to do with double NATing is in red, ignore this if your router is WAN facing.

Fairly straight forward, go to VPN > IPSec > Click Add P1

  • Enter the Remote Gateway as the WAN IP address of the EdgeRouter (or the Superhub in my case) 1.2.3.4
  • Enter a brieft description in the Description box – VPN to pfSense LAN
  • Select Peer identifer as KeyID tag then enter the WAN address of EdgeRouter (192.168.100.1) else leave as Peer IP address
  • Enter your pre-shared key in the Pre-Shared Key box – testing123
  • Set the DH Group to 14
  • Press Save

That’s your Phase 1 entry configured, now for Phase 2:

Go to VPN > IPSec > Click on Show Phase 2 Entries for Home

  • Enter Remote Network as the home network subnet – 192.168.100.0/24
  • Put a brief description in the Description box – Home
  • Set PSF Key Group to 14
  • Press Save and then hit Apply Changes

Finally, we need to create a firewall rule to allow traffic to pass over the VPN:

  • Go to Firewall > Rules > IPSec and click Add
  • Change Protocol to any
  • Enter a brief description in the Description box – Allow VPN Traffic
  • Press Save any hit Apply Changes

Configuring the EdgeRouter

First of all make sure you are running the latest firmware otherwise options may be missing and this may not go smoothly! Currently (March 2017) I’m running EdgeRouter Lite v1.9.1.

Configuring the EdgeRouter is pretty straight forward, you don’t need to do anything via command line or console (unless you really want to, knock yourself out!) – Go to VPN > IPSec Site-to-Site

  • First tick the box Show advanced options to show the encryption options
  • Under Global Options leave Automatically open firewall and exclude from NAT unless you want greater control over who can connect in
  • Under Site-to-site peers enter the Peer as the home WAN address – 5.6.7.8
  • Put a brief description in the Description box – Remote
  • In local IP enter any
  • For Encryption set AES-256
  • In Pre-shared secret enter the key set previously – testing123
  • Enter the Local subnet as 192.168.100.0/24
  • Enter the Remote subnet as 192.168.150.0/24

All being well you should end up with something like below:

Once everything is saved, head over to the pfSense IPSec Status page and hit connect if it hasn’t already established and  there you have it!

At this point you may be asking why did you uncheck the option to Automatically open firewall…, this is because I like to have greater control over what IP addresses are allowed access to my network.

To substitute this option I created a rule in the NAT section translating UDP port 4500 to the routers local IP address (192.168.100.1). In turn I set the Src Address Group of this rule to a list of predefined IP addresses, thus only allowing access to my networks and blocking the rest of the world.

 

 

 

How to List the Contents of a Web Directory

Any good web host will secure the contents of website directories which don’t have an index page by not allowing the  files or folders to be listed, instead you’ll get a 403 error page saying access is forbidden. Whilst this is good in practice, sometimes you might actually need to list the contents – and its simple to enable on an Apache web server – add one line to your .htaccess file and you’re done!

How it’s done

Options +Indexes

Notes

  • If you have access you can edit your web server configuration and make it global

Add a NAS drive to your Livedrive account for free

I used to be a customer of popular cloud backup service Livedrive. The upload and download speeds were nothing to shout about and one annoyance was having to pay extra to add a NAS drive to your account, but there is a workaround!

How so?

All you need to do is add a symbolic link to your NAS drive from your computer. Think of a symbolic link as a fancy shortcut, the only difference being it masks the destination instead of taking you straight there – you’ll see what I mean when you read on.

Imagine you have a Windows computer with your NAS drive with the root of the drive already mapped to Z:, you have a folder on your NAS called MyFiles and would be able to browse to Z:\MyFiles to see whatever is stored there. Next imagine we have a folder called C:\Backup which is already uploading to your Livedrive account, using  the following command we will make C:\Backup\MyFiles lead to your NAS and in turn be included with your Livedrive backup.

mklink /d "C:\Backup\MyFiles" "Z:\MyFiles"

For me, this worked absolutely fine and I had a couple of TB uploaded without ever being caught out. I’ve since jumped ship to Amazon Drive, whilst it is more expensive per year I’ve got it running from multiple computers and the upload and download speed always tops out my connection, so I can’t complain!

Notes

  • Use the above guide at your own risk – I won’t be held liable if anything happens to your Livedrive account, files or anything else because of this!
  • This doesn’t work with Dropbox or Google Drive  – sorry
  • You only need to run the command once, after that the link will be remembered
  • To remove the link just delete it as you would any other  file or folder

Turnigy 1:16 Nitro RC Cars

I recently bought 2 Turnigy Nitro RC cars to have a little fun with, whilst being fully aware of them having a problem with the starter mechanism I hoped that HobbyKing would have resolved them by now, but unfortunately not.

I bought a Truggy for £50 and a Buggy for £70 and managed to start them both twice before the pull starter began to slip. I took the buggy engine apart and found no obvious problems, but there was a lot of oily residue covering pretty much everything, even the pull starters chord and this seemed to be the reason it was slipping.

Searching online at the HobbyKing website I  found various posts about replacing different engine parts but the most promising said that a Graupner 92600.117A back plate was the ultimate solution and stops the oily residue from the fuel seeping everywhere.

All in all it looks like a design flaw with the engine, but two new back plates are on their way from Germany, £30 inc postage and should be here in a few weeks.

Turnigy Buggy & Truggy

Update 16/08/2015 –

The new back plates fits nicely and the engines have both turned over flawlessly since. The pictures below show briefly how it was done to the buggy engine, the same steps were repeated for the truggy engine too.

A video will be attached soon showing the cars in action.

Unstick a LinkStation Disk Backup

Imagine this… you have two decent network attach storage boxes which regularly backup one to the other using a built in Disk Backup tool –  Brilliant huh, sounds almost like a nerdy dream! Now imagine part way through a backup you get a power cut or you just trip over the power cable ripping the plug out the wall… not to worry, things will pick up where they left off… unless those decent boxes are Buffalo LinkStations!

I first discovered this flaw a few weeks back when one of my nightly backups seemed to be taking longer than usual. I gave the box about a day or so to try and fix itself but it still kept saying that the disk backup was in progress and in the admin interface and I was unable to cancel or remove the backup, so it was pretty much stuck as you can see below:

stuck-backup

I headed to the official Buffalo support website which seemed to have a fix for this common problem – See for yourself below:

buffalo-stuck-disk-backup
Okay so you have to restore the box to factory defaults… no thanks! I can only assume that because the HS-DHGL is one of their older discontinued products they just can’t be bothered to make a firmware update as it’s not worth their time or effort, but the other option is to use SSH to edit a file which will force the backup to complete.

Getting Unstuck

The following guide will assume you have already enabled SSH and are logged in ready to go, if you haven’t yet enabled SSH see this post here.

  • First of all we need to locate the backup configuration file and this depends on the job number specified on the admin interface, in my case it was number 1 so we need to type in the following command to open the file in a text editor:
    • "vi /etc/melco/backup1"
  • You will now see the configuration file open, hit I (for indigo) on your keyboard to allow inserting of new text and change the line status=running to status=done
  • Hit the Escape key and then type :wq to save your changes and quit
  • Head back to the admin interface to the Disk Backup section and you’ll now see the backup showing as complete as seen below:
    job-complete
  • That’s it – The backup is unstuck, and we haven’t had to restore anything to factory defaults!

Notes

  • This has been tried and tested on the following models/firmware: HS-DHGL/v2.1
  • Finally, if you could let me know if you encounter any problems or can confirm if this works for other models I’d be grateful