Monthly Archives: November 2018

Another old copy

This post is by request (after I mentioned the trick in passing to someone on IRC).

So, the lay of the land: you find yourself in some dubious or highly unconventional position of server access. Maybe it’s behind a few layers of ssh jumps and VPN paths. Maybe the only way to get data input is that it’s on the other side of a phonecall, a human slowly typing in some things as you read it out to them. Maybe it’s just some damned SSO config on a corporate network somewhere. Doesn’t matter exactly which it is, you have the problem that you cannot easily copy a set of files to where you need it.

There’s a few handfuls of ways in which one can deal with this. One of the easiest, if you can manage, is to stick it somewhere as an HTTPS resource and pull that down. But… sometimes you don’t have HTTPS access (or, for that matter, any outbound internet access at all). Maybe you can do some DNS tunneling? The difficulty of that ramps up rather quickly, unfortunately. You just happen to not have your DNS fileserver running today!

But… hey, you already have a shell, right? And there’s a `base64` or `od` binary on that host, or maybe some python or Perl or even bash?

Well then, lucky you.

Take your file on the input side. Pop it through a base64 encode.

# presuming OSX
source% base64 -i some_input -o the_base64

Read that base64 into your pastebuffer, paste on the other side. End off your heredoc (they do make it easier in many cases). Remake your file as you need it.

# presuming linux
dest% cat <<EOF>> base64_input
< the paste goes here >
dest% base64 -d base64_input > the_original

You need multiple files? Roundtrip it through an archive!

Maybe they’re big files and you’re worried about items getting lost? `split` and `par2` are your friends! Don’t have `par2`? No matter, you can install it in this manner!

You can see how versatile this technique can be. And how insane. But it’s a nice enough wrench to have in your toolbox if you ever need to hit a nail in, if you know what I mean.

It’s also by no means new. Nor is it previously undocumented. Or even the only variation of this trick[0]. It’s just one of those things that sometimes happens to need to be shown. Lest the arcana be forgotten.

[0] – for a fun exercise, see how many variations of this you can come up with.