iodine - IP over DNS is now easy http://code.kryo.se/iodine ******************************** This is a piece of software that lets you tunnel IPv4 data through a DNS server. This can be usable in different situations where internet access is firewalled, but DNS queries are allowed. QUICKSTART: Try it out within your own LAN! Follow these simple steps: - On your server, run: ./iodined -f 10.0.0.1 test.asdf (If you already use the 10.0.0.0 network, use another internal net like 172.16.0.0) - On the client, run: ./iodine -f 192.168.0.1 test.asdf (Replace 192.168.0.1 with the server's ip address) - Now the client has the tunnel ip 10.0.0.2 and the server has 10.0.0.1 - Try pinging each other through the tunnel - Done! :) To actually use it through a relaying nameserver, see below. HOW TO USE: Server side: To use this tunnel, you need control over a real domain (like mytunnel.com), and a server with a static public IP number that does not yet run a DNS server. Then, delegate a subdomain (say, tunnel1.mytunnel.com) to the server. If you use BIND for the domain, add these lines to the zone file: tunnel1host IN A 10.15.213.99 tunnel1 IN NS tunnel1host.mytunnel.com. Now any DNS querys for domains ending with tunnel1.mytunnnel.com will be sent to your server. Start iodined on the server. The first argument is the tunnel IP address (like 192.168.99.1) and the second is the assigned domain (in this case tunnel1.mytunnel.com). The -f argument will keep iodined running in the foreground, which helps when testing. iodined will start a virtual interface, and also start listening for DNS queries on UDP port 53. Now everything is ready for the client. Client side: All the setup is done, just start iodine. It also takes two arguments, the first is the local relaying DNS server and the second is the domain used (tunnel1.mytunnnel.com). If DNS queries are allowed to any computer, you can use the tunnel endpoint (example: 10.15.213.99 or tunnel1host.mytunnel.com) as the first argument. The tunnel interface will get an IP close to the servers (in this case 192.168.99.2) and a suitable MTU. Now you should be able to ping the other end of the tunnel from either side. MISC. INFO: Note that you can have only one client per server at the same time. This is because of the fragmentation of big packets going upstream, and will be fixed in future versions. Try experimenting with the MTU size (-m option) to get maximum bandwidth. It is set to 1024 by default, which seems to work with most DNS servers. If you have problems, try setting it to below 512. If you have problems, try inspecting the traffic with network monitoring tools and make sure that the relaying DNS server has not cached the response. A cached error message could mean that you started the client before the server. The upstream data is sent gzipped encoded with Base32. DNS protocol allows one query per packet, and one query can be max 256 chars. Each domain name part can be max 63 chars. So your domain name and subdomain should be as short as possible to allow maximum throughput. PORTABILITY: iodine has been tested on Linux (x86 and SPARC64), FreeBSD (x86), OpenBSD (x86), NetBSD (x86) and MacOS X (10.3, ppc, with http://www-user.rhrk.uni-kl.de/~nissler/tuntap/). It should work on other unix-like systems as well that has TUN/TAP tunneling support. Let us know if you get it to run on other platforms. THE NAME: The name iodine was chosen since it starts with IOD (IP Over DNS) and since iodine has atomic number 53, which happens to be the DNS port number. THANKS: - To kuxien for FreeBSD and OS X testing - To poplix for code audit AUTHORS & LICENSE: Copyright (c) 2006 Bjorn Andersson , Erik Ekman Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.