GNOME Keysign 0.9.9

tl;dr: We have a new Keysign release with support for exchanging keys via the Internet.

I am very proud to announce this version of GNOME Keysign, because it marks an important step towards a famous “1.0”. In fact, it might be just that. But given the potentially complicated new dependencies, I thought it’d be nice to make sort of an rc release.

The main feature is a transport via the Internet. In fact, the code has been lurking around since last summer thanks to Ludovico’s great work. I felt it needed some massaging and more gentle introduction to the code base before finally enabling it.

For the transport we use Magic Wormhole, an amazing package for transferring files securely. If you don’t know it yet, give it a try. It is a very convenient tool for sending files across the Internet. They have a rendezvous server so that it works in NATted environments, too. Great.

You may wonder why we need an Internet transport, given that we have local network and Bluetooth already. And the question is good, because initially I didn’t think that we’d expose ourselves to the Internet. Simply because the attack surface is just so much larger and also because I think that it’s so weird to go all the way through the Internet when all we need is to transfer a few bytes between two physically close machines. It doesn’t sound very clever to connect to the Internet when all we need is to bridge 20 centimetres.

Anyway, as it turns out, WiFi access points don’t allow clients to connect to each other :( Then we have Bluetooth, but it’s still a bit awkward to use. My impression is that people are not satisfied with the quality of Bluetooth connections. Also, the Internet is comparatively easy to use, both as a programmer and a user.

Of course, we now also have the option to exchange keys when not being physically close. I do not recommend that, though, because our security assumes the visual channel to be present and, in fact, secure. In other words: Scan the barcode for a secure key signing experience. Be aware that if you transfer the “security code” manually via other means, you may be compromised.

With this change, the UX changes a bit for the non-Internet transports, too. For example, we have a final page now which indicates success or failure. We can use this as a base for accompanying the signing process further, e.g. sign the key again with a non-exportable short-term signature s.t. the user can send an email right away. Or exchange the keys again after the email has been received. Exciting times ahead.

Now, after the wall of text, you may wonder how to get hold of this release. It should show up on Flathub soon.

Talking at GUADEC 2018 in Almería, Spain

I’ve more or less just returned from this year’s GUADEC in Almeria, Spain where I got to talk about assessing and improving the security of our apps. My main point was to make people use ASan, which I think Michael liked ;) Secondarily, I wanted to raise awareness for the security sensitivity of some seemingly minor bugs and how the importance of getting fixes out to the user should outweigh blame shifting games.

I presented a three-staged approach to assess and improve the security of your app: Compilation time, Runtime, and Fuzzing. First, you use some hardening flags to compile your app. Then you can use amazing tools such as ASan or Valgrind. Finally, you can combine this with afl to find bugs in your code. Bonus points if you do that as part of your CI.

I encountered a few problems, when going that route with Flatpak. For example, the libasan.so is not in the Platform image, so you have to use an extension to have it loaded. It’s better than it used to be, though. I tried to compile loads of apps with ASan in the past and I needed to compile a custom GCC. And then mind the circular dependencies, e.g. libmfpr is needed by GCC. If I then compile a libmfpr with ASan, then GCC would stop working, because gcc itself is not linked against ASan. It seems silly to have those annoyances in the stack. And it is. I hope that by making people play around with these technologies a bit more, we can get to a point where we do not have to catch those time consuming bugs.

Panorama in Frigiliana

The organisation around the presentation was a bit confusing as the projector didn’t work for the first ten minutes. And it was a bit unclear who was responsible for making it work. In that room the audio also used to be wonky. I hope it went well alright after all.