PuTTY as telnet handler in IE7

As you’ll know if you read around my blog and other pages here, I do networks with a tilt towards security. At the moment I’m alternating between studying for a Checkpoint CCSE (Checkpoint Certified Security Expert) and studying the parts needed for a CCNP (Cisco Certified Network Professional), having done a CCSP (Cisco Certified Security Professional) a couple of years back.

Right now I’m on the CCNP kick, and as part of that I’ve been using some remote labs (handy if you can get them). One of the things that these remote labs use is a telnet connection to control the kit you’re configuring, and that connection is usually accessed via a telnet:// link on a web page. Unfortunately these don’t work under Internet Explorer 7 without some tweaking.

So, right here, and as much for my own records as to share it with the internet as a whole, I’m going to meander over the tweaks needed not only to get the telnet handler working on IE7, but also how to set it to use PuTTY, my terminal emulator and ssh client of choice.

The process can be broken down into three steps

1. download putty (link)
2. enable the telnet handler (link)
3. set putty as your telnet  handler application (link)

The first step of course is to download and install PuTTY from its homepage, go on there’s no reason not to. I reckon that it’s among the finest pieces of software available on the internet, and even better than that – it’s free! You cannot go wrong at that price can you?

Next you’ll want to re-enable to telnet handler. I’m not quite sure why Microsoft decided to disable it in IE7, it worked in IE6 and previous. Sure telnet is an old and not wonderfully secure protocol (it sends everything you type in plain text, so mr nasty in the middle can read your passwords), it isn’t even installed by default on Vista, but it’s an old friend, and a handy troubleshooting tool.

To enable the handler you need to run up regedit or your windows registry editor of choice and create the key “HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_DISABLE_TELNET_PROTOCOL”, in that key you need to create a DWORD called “iexplore.exe” and set its value to 0 (you’re disabling telnet being disabled see?).

For your convenience I have placed a .reg file here that does this bit for you.

The final thing to do is set putty to be the telnet handler. The instructions are actually contained in the release notes on the homepage, but it’s always good to repeat things eh?

Still got regedit open? Navigate to “HKEY_CLASSES_ROOT\telnet\shell\open\command” and replace the string value in there with “path\to\putty.exe %1″, so for example if you took the default installation location it would be c:\progra~1\putty\putty.exe

Again, for your convenience i have a .reg file here, but it’ll only work if you installed PuTTY into the default location as above.

With all that done, restart your browser (you might have to restart your computer, I’m not sure), and give it a try. I’d create a html file with a link in it to telnet to your router <a href=”telnet://your.router.ip.address:23″>mummy!</a> kind of thing.

Assuming it all works, you will have many hours of happy remote labbing. Remember me when you’re earning super mega money won’t you?