Recently, Matthew Garrett wrote about the abysmal X inter-app security situation. I.e., the total lack of a security situation. It came with an interesting proof-of-concept application, XEvilTeddy, demonstrating the ability to steal passwords and upload them elsewhere. Everybody knew such an application was possible; the interesting part was exhibiting one.

All good and fine, but one thing has been bothering me. Matthew wrote “if you’re using Snap packages on Mir (ie, Ubuntu mobile) then there’s a genuine improvement in security.” But is that really true?

Now, getting rid of X means that an application no longer can simply ask the X server to get all the keystrokes and that would seem to be an obvious improvement in security. It is, however, only an actual improvement in security if it is the only way of getting the keystrokes. It is not.

Recent years have seen a slew of side-channel attacks on, say, gpg. For example, see here and here. Basically, the cpu leaks information about the program it is running in the form of timing, current use, sound(!), electromagnetic radiation, etc. Some of these are observable from another process on the same machine, others from a laptop in the next room. If there is a direction in the field, my take on it is that attacks running on the same machine are considered a bit too easy nowadays.

It is hard to avoid side-channel leakage. gpg gets hardened every time an attack is discovered, but (say) firefox and gtk+ almost certainly leak like crazy.

“But such an attack is hard,” I hear you say. Maybe, but I do not think so. The thinking used to be that exploiting overflow of stack-based variables was hard, but all it took was one explanatory article and that cat was out of the sack.

If I was not such an incurably lazy person I would create XReallyEvilTeddy to demonstrate this. I am, so I have not. But it would be naïve to believe such applications do not exist. And it would therefore be naïve to believe that Mir and Wayland really do have better security.