DEFCON CTF VM Files

This repository contains the files necessary for the DEFCON CTF VM that I created. You can grab a copy of the VM itself from my blog.

To use this VM, simply start it up in VMware and do the following to connect to a given service:

nc defcon.local <port>  # for TCPv4 services
nc6 defcon.local <port>  # for TCPv6 services

NOTE: Your network settings may not resolve "defcon.local" as a hostname. You can log in and run ifconfig from inside the VM to get its IP address. You can also try using just "defcon" or "defcon." and see if those work.

Getting the flag for each service is, obviously, an exercise left to the reader.

List of Services

DEFCON 13 (2005)

• Organizers: Kenshoto
• Operating System: FreeBSD 5.4

NOTE: Check /root/kinit.py for how to run these services! Many of these were xinetd services that don't contain their own server setup code.

Other binaries I've come across that may have been part of this year:

• alice
• b16
• kstrings
• nettoe
• readmail
• smtpd
• vacation

DEFCON 14 (2006)

• Organizers: Kenshoto
• Operating System: Solaris ???

Notably absent from the VM are the services from DEFCON 14. These challenges were built for and ran on Solaris. Since I haven't created a Solaris VM to host them (and a Solaris translation layer for FreeBSD doesn't appear to exist), I can't get them running. I do, however, have what I think are all of the services if anyone would like to play with them. Their names are:

• CookieMonster
• CustomHeap
• FingerLickinGood
• FuckTcpd2
• Heisenberg
• IFallDown
• InMyMemory
• KuFtpd
• NPComplete
• OhShitD
• SpamMe
• Vanilla
• YouHadMeAtHello

DEFCON 15 (2007)

• Organizers: Kenshoto
• Operating System: FreeBSD 6.3?

NOTE: Many of the following services require the compat6x-i386 package to be installed.

Other binaries I've come across that may have been part of this year:

• xserver (looks like a web challenge...drops to user "xserver")
• UserAdder and makeuser? (looks like just a way to create users...drops to user "makeuser")
• I have a "serverd" somehow that I have listed as being from this year, but honestly no idea where this is from or what it's for

DEFCON 16 (2008)

• Organizers: Kenshoto
• Operating System: FreeBSD 6.3

Other binaries I've come across that may have been part of this year:

• SupaFlyTNT
• Something that would have used a user named "nubbin"?

DEFCON 17 (2009)

• Organizers: DDTEK
• Operating System: FreeBSD 7.2

DEFCON 18 (2010)

• Organizers: DDTEK
• Operating System: FreeBSD 8.0

DEFCON 19 (2011)

• Organizers: DDTEK
• Operating System: FreeBSD 8.2

NOTE: In addition to the services below, there was also a service called "finch" that interacted with some remote control cars in a chicken coop. To my knowledge, no team ever figured out how to score successfully (you were supposed to drive your car into the lighted area matching your car's color). Since "finch" was a Linux binary that was meant to run on your own machine, it isn't included below.

DEFCON 20 (2012)

• Organizers: DDTEK
• Operating System: FreeBSD 9.0

NOTE: All these services bound the interface em1 in the game, but I patched them to bind em0 for the VM to work.

Setting Up Your Own VM

In case you don't like the VM I've created, here's some quick documentation on how I set up the VM myself!

Initial Setup

The initial setup is simple:

• Installed FreeBSD 9.1 with default options from the i386 install media
• Uncommented and set "PermitRootLogin" to "yes" in /etc/ssh/sshd_config with vi
• Ran /etc/rc.d/sshd restart so I could SSH/SCP

NOTE: In the real CTF, each team would actually get a FreeBSD jail, rather than a VM. For simplicity, I've set everything up outside of a jail. I hope to find my documentation on jails and include it here in the future if anyone wants to set things up more authentically. For now, you'll just have to make do with this approximation.

Service Setup

Setting up services was a little more involved. In order to run a given service, you will generally have to create a user and home directory for that user. This is because most DEFCON CTF services will "drop" privileges from root to an unprivileged user specific to the service, just like real services. The ownership of the binary will also need to be changed to prevent unwanted modifications. To do this:

# create a user with a given name (-n), shell (-s), and home directory (-m)
pw useradd -n <username> -s /usr/bin/false -m
chmod 750 /usr/home/<username>
chown root:<username> /path/to/service
chmod 750 /path/to/service

Binaries before DEFCON 19 were located inside each service's home folder. Starting in DEFCON 19, however, they were moved to /usr/local/sbin. Either approach is fine, but I found it easier to place all the services in /usr/local/sbin.

Flags were typically stored in a file called "key" inside of each user's home directory. A kernel module was used to change these out periodically (about once every 2-5 minutes or so). Since I don't have a similar kernel module, I just placed the sha1sum of the service into the flag file:

sha1 /path/to/service | cut -d' ' -f4 > /usr/home/<username>/key
chmod 540 /usr/home/<username>/key

At this point, running the service should be as easy as:

/path/to/service &

You can check if it is running/listening by doing:

ps aux | grep <service>  # check if it is running
sockstat | grep <service>  # check if it is listening (and on what port)

If that doesn't work, check the table above to see if there are any caveats for a particular service. Some services require extra stuff to be installed, configured, or otherwise present in order for it to function. Some were also not actually network services and had to be run locally.

Once a service is running, you should be able to use netcat to connect to it:

nc <hostname or address> <port>  # for IPv4
nc6 <hostname or address> <port>  # for IPv6

Note that services won't start up by default unless you create an /etc/rc.d startup script for them. The template I created for these, if you'd like to develop your own, is called rc_d_template in the top level of this repository.