Web to ssh gateway – not so difficult with Right Tools

Intro
I won’t go into details in this posting for fear that the “bad people” will be more likely to benefit than the legitimate users of what I’m describing. That being said there are some legitimate uses, for instance when you need that terminal access but a direct ssh connection just isn’t available.

Ajaxterm
I’m kind of amazed at how far Javascript has come. You can implement a curses-based application in javascript, i.e., a terminal console? Yup. You bet. And the kicker is that it works quite well. Teraterm it ain’t, but I’ll be danged if you can’t vi a file, run top as well your basic commands, all over a pretty standard-looking web page. That’s what we mean by gateway – an application which converts one protocol to another. In this case HTTP to shell (I suppose).

The generic application is called ajaxterm. I used it from a distribution that runs a local python server on my server. It’s described here:

https://github.com/antonylesuisse/qweb/tree/master/ajaxterm/README.txt

If you keep the default screen size, 80×24, he says it has few enough characters that a screen refresh can be contained in one packet. In my testing the echo delay was probably under one quarter second.

Forget about a scroll bar holding 1000’s of lines, however. You get just your basic terminal like in the old days.

Someone reminded me about screen, which I hadn’t been using. Screen is an extremely useful tool. It’s like a terminal multiplexor. Now I normally set up my screen escape sequence to be Ctrl-\, but for some reason this particular sequence is not recognized by Ajaxterm. What I settled on instead is Ctrl-g (escape ^Gg in your .screenrc). I don’t like to use the default Ctrl-a because this is a useful emacs editing mode sequence – takes you to beginning of line. Popping between screens is a little slow with ajaxterm as might be expected. It’s a worst-case, everything must be re-drawn situation, I suppose. But ajaxterm + screen is a pretty powerful combination.

Conclusion
Now I have an additional path to my server’s command line if a direct ssh connection isn’t available.

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