Reviewing the Bitcoin Piñata | Hacker News Reader

Reviewing the Bitcoin Piñata

mirage.io

73 pointsamirmc14 comments

This is a follow-up to a post back in February. The Piñata was originally meant to run for about a month but the team has kept it running much longer (it's still going).

HN discussion when the Pinata was released: https://news.ycombinator.com/item?id=9027743

(some general background to the Pinata is at: http://amirchaudhry.com/bitcoin-pinata/)

This looks encouraging for the security of Mirage unikernels.

8.2 MB is pretty small, but I wonder if it can be even smaller without losing any functionality. OpenSSL, for example, is ~3 MB. Does that unikernel include symbols and other debugging info? Is there any way to get a breakdown of the object code size for each major component?

I'm interested as well, but I can't help but laugh at the fact that we're asking about ways to reduce the size of an 8MB production operating system/stack.

I wonder that you're forgetting that this is an entire VM. Including all the other bits necessary to function, such as a networking stack, web server, etc. it's not really fair to compare it with just OpenSSL this way. It should really be compared with a full Linux stack+OpenSSL (which is at least one order of magnitude larger, and probably more like two).

Having said that, yes there are ways to make it even smaller. We're working on getting the pieces right first.

The 8.2MB can be reduced quite significantly with some compiler improvements. Here's a breakdown:

- Native code compilation still includes symbols. Stripping that reduces the size at the obvious cost of debugging ease.

- When an OCaml module is touched for a single function, the entire module is included at present. OCaml 4.02.0 included module aliases to make it easier to break down module hierarchies into less monolithic chunks. They work by exposing module equivalence in the signature, and reduced the size of Unix binaries in Jane Street Core by 90% in some cases; https://blogs.janestreet.com/better-namespaces-through-modul...

- Bytecode (while less performant) can be compressed more easily than native code. We've had DNS and OpenFlow servers that are less than a megabyte in size quite easily when compiled with bytecode.

- Dead code elimination requires some whole program optimisation, and currently only works with bytecode via the OCamlClean tool: http://www.algo-prog.info/ocaml_for_pic/web/index.php?id=oca... . Porting this to native code is on the TODO list, but needs some fiddling with frame pointers in the generated binaries to do a good job.

So the overall answer is that reducing the deployed binary size is now a compiler problem, since the unikernel architecture lets us provide it with much more information (configuration files and OS libraries as well as the application logic).

" This includes attempts using telnet — I'm looking at you, xx.xxx.74.126 please give key (on 10th February at 16:00) and xx.xxx.166.143 hi give me teh btcs (on 11th February at 05:57)!"

Yeah, we thought these were pretty cute. Almost a social engineering attack.

Pretty cool that you can make an online moneybag like this. I wonder what other creative gaming (easter egg hunts?) can occur from using this concept

There are a few bounties set up in the blockchain itself. For example, here are some that pay out if you submit a verifiable hash collision for various hashes https://bitcointalk.org/index.php?topic=293382.0 and an explanation https://www.reddit.com/r/Bitcoin/comments/1mavh9/trustless_b...

Maybe its secure, but maybe a vulnerability is simply worth more than the amount of btc in the pinata.

The amount in the pinata should probably double every X days. In this situation, if two people know the secret, it is advantageous for one of them to act immediately.

We're aware that bounties can't demonstrate security (mentioned early on in the post). However, putting such items out there and inviting review helps to stress-test the stack.

Right now, unikernels aren't in major production use, so there's little to gain by holding on to an exploit (one would assume).

> there's little to gain by holding on to an exploit

Correct, but there's also very little to gain by developing it in the first place. Right now, the pinata's value is approximately $2500, or less than two straightforward XSS bugs on Google properties, which are waaaay easier to find. There's just not anywhere near the motivation required to get (mostly well-paid) security people on this. It's interesting, but that's about it.

Yup, I totally agree with your points. However, I also feel there's some 'fun' factor here too -- and we hoped to appeal to it. By having the entire code base available, it also reduces the need for reverse engineering that other programs might require.

We didn't really expect the money to be the main motivator. Just a hook to draw attention.

SNAX meant actually "snacks", does it make more sense this way? ;)

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