Simplified remote access to a home lab

One of the challenges of being someone that travels on a regular basis is that you are often not near your lab. The investment in a home lab really requires the ability access it from anywhere in order to meet any hope of a falsely perceived ROI. I’ve had a Unix/Linux based workstation for more of my working life than I’ve had a Windows one, sure Windows was always involved as a virtual machine on VMware Workstation (Linux) and now VMware Fusion (Mac).

There are insecure, complex and/or expensive options, such as buying a Cisco ASA or some other “firewall” that supports VPN…but that doesn’t support the goals and requirements for my lab and is the expensive option. The possibly more complex option would be to build a firewall from an PC, but that is high maintenance and I prefer my regular access to be simple and reliable (thus I have a Mac + Airport household, other than the 3 lab servers). The insecure option would be to expose RDP on your Windows guest directly to the Internet, that is not an option for me. My service provider background makes me paranoid about Windows security, or lack there of.

I have chosen to go with the cheapest and simplest option, in my mind. Linux virtual machines are light weight, use few resources, and you could always use a non-persistent disk to make it revert to a known config with a simple reboot (or restore from a snapshot). I leverage SSH tunneling, which is often overlooked and people peruse more complex L2TP or IPSEC based options…but SSH is just simple, seldom blocked on networks and does the job. I have not gone as far as using L3 tunneling, though that is an option with SSH.

Firewall Settings

In my network I have 1 open port on my “firewall” (Apple Airport Extreme) which is forwarded to a minimal Linux virtual machine with a static (private) IP address.

  • Public Internet –> Port 8080 on firewall –> Port 22 on Linux

I would recommend creating multiple port forwards on your firewall, this will give you other options if the one you choose was blocked. I’ve had good luck with 8080 and 8022 so far, but some environments may block those…there is nothing to say you can’t use port 80, however any forced proxy server will break your SSH session access…or protocol inspecting firewalls, and some service providers block the ports 25, 80, 443 and others.

The beauty is that from the Linux side very little needs to be done, I would recommend editing your SSH config on the Linux VM to prevent root access. Keep in mind you really must create your non-root users before you do so, otherwise you cannot login via SSH and will have to add those accounts via console.

Secure Linux SSH Settings

I would recommend making sure your Linux VM is up to date using the correct update process for whichever distribution you select. The SSH server is pretty sure anymore, but when compromises are found you should update to apply the relevant patches.

I would recommend editing the config file for sshd (/etc/ssh/sshd_config). Find the line that states PermitRootLogin and edit it to be “no”, if it is commented out remove the “#” and set it to “no”.

  • PermitRootLogin no

Now restart SSH: $: sudo /etc/init.d/sshd restart

The reason to remove root access to SSH is that its a “known” account and can easily be targeted. You should generally use hard to guess usernames and complex passwords for this “access server”, it is going to be port scanned and have attempts made to compromise it. You ideally would configure the authentication policies so that account lock-out occurs after too many false attempts. Personally I do not allow interactive password based logins, I use only pre shared keys (much more difficult to guess a 2048 bit RSA key than a 8 character password). You can investigate the RSAAuthentication and PubkeyAuthentication options within the sshd_config file to learn more about that option.

Public Access

My cable modem provider issues me a DHCP address, it happens to have been the same address for many months but there is always the chance it could change. I use Dyn (http://dyn.com) to provide dynamic DNS to my home lab. You can install one of their dynamic DNS clients (http://dyn.com/support/clients/) on any OS within your home network that is generally always on (e.g on your Linux access server), some “routers” (e.g. Cisco/Linksys) have one built in.

Client Connection

Setup SSH Saved Configs
At this point you just need to configure your client. I happen to use the default SSH client on Mac OS, though if you are using Windows you could use PuTTY or another client and achieve the same. In my case I don’t want to manually type out all of my config settings every time I connect, remember this is more than for SSH CLI access…it is for our simple “VPN”.

In my environment I either want SSH access or RDP (e.g. to Windows for vSphere Client) access. I do this through simple port forwarding rules.

In order to configure saved “session” settings for the shell SSH client on OS X you will need to do the following:

  1. Open a terminal window of your choice (Terminal.app or my preferred iTerm2)
  2. Navigate to your home directory: $: cd ~/
  3. Create a .ssh directory: $:~ mkdir .ssh
  4. Create a .ssh/config file: $: touch ~/.ssh/config
  5. Set security settings on the .ssh directory, otherwise sshd will not accept your keys if you use them in the future: $: chmod 700 ~/.ssh
  6. Set security settings on config (not really necessary, but anything in .ssh should be set this way): $: chmod 600 ~/.ssh/*
  7. Now we can move on to building our configuration

You can use the editor of your choice to open the config file, if you wish to use an app you can go to finder and press CMD-Shift-G and you will be given a box to type in your target folder (e.g. ~/.ssh/ ), you can then edit the file with whichever editor you prefer (e.g. TextMate). The format of the file is:

Host <name used as ssh target>
        HostName <target hostname>
        User <username>
        Port <TCP port on firewall>
        Compression yes
        AddressFamily inet
        CompressionLevel 9
        KeepAlive yes
        # RDP to Server1
        LocalForward localhost:3389 <private IP>:3389
        # RDP to Server2
        LocalForward localhost:3399 <private IP>:3389
        # RDP to Server3
        LocalForward localhost:3390 <private IP>:3389

Working example:
Host remotelab
        HostName my-dns.dnsalias.net
        User user0315
        Port 8080
        Compression yes
        AddressFamily inet
        CompressionLevel 9
        # Privoxy
        LocalForward localhost:8118 localhost:8118
        # RDP to Control Center Server
        LocalForward localhost:3389 192.168.100.15:3389
        # RDP to vCenter
        LocalForward localhost:3399 192.168.100.20:3389
        # RDP to AD Server
        LocalForward localhost:3390 192.168.100.60:3389
        # HTTPS to vCloud Director cell
        LocalForward localhost:443 192.168.100.25:443

In my case I also installed and configured Privoxy (http://www.privoxy.org/ ) to give me the ability to tunnel other protocols via proxy settings on my laptop (e.g. web browser, instant messengers, etc).

Connect To Your Lab

What was the point of all of this if I don’t show you how to connect? Open your terminal again and type “ssh” followed by your saved config name (e.g. $: ssh remotelab). Authenticate as needed, you should then be connected to the shell of your Linux VM.

Now open your RDP client of choice (I suggest CoRD: http://cord.sourceforge.net/ ), select to connect to one of your target tunnels specifying localhost:<target port for desired server>.

wpid-voila_capture503-2011-09-2-18-182.png

Now anyone lazy, errr…striving for efficiency, will save a config for their servers within CoRD for connecting directly when on your network or via the tunnel. You can then just select the saved session within CoRD.app without having to remember which TCP port is for each server.

Of course, for those Windows users this doesn’t help. In Windows you have a really neat client you can use to simplify this, I would recommend Tunnelier from bitvise: http://www.bitvise.com/tunnelier There may be simpler GUI driven SSH clients for configuring this for Mac OS, however I just use what is included as its always there and it doesn’t break when you upgrade to the next version.

Have a better way that is easy? Let me know, I’m always open to new ideas around getting access to the lab. I’ve always intended to setup View with a secure server, but that is also on the complex path and I want something that just works. Once this configuration is setup you can duplicate it easily, as the complexity is in the saved .ssh/config file and not the “server”.

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