Reflections on WireGuard Design Goals
b.candler at pobox.com
Fri Aug 10 15:35:14 CEST 2018
> For whatever reason, in the last several weeks, WireGuard been receiving a
> considerable amount of attention, and with that comes various parties
> interested in the project moving in this direction or in that direction. And
> more generally, over the last year or so, we've seen a decent amount of
> interest from different folks wanting to do different things with the project
> and with the protocol. This inevitably leads to the question: what do we
> actually want WireGuard to be, as a project, as a protocol, as a set of
> implementations, as a design methodology, and so forth? I've had a pretty
> clear idea about that, but I don't think I've ever tried to communicate
> aspects of it in this context, so I thought here I'd highlight two important
> design goals that motivate us.
Thanks for explaining the project background, and your very sensible
goals of simplicity and robustness. And thanks for releasing this
excellent piece of software.
From my point of view, the only thing which makes me uncomfortable
about wireguard is the lack of any second authentication factor. Your
private key is embedded in a plaintext file in your device (e.g.
laptop), not even protected with a passphrase. Anyone who gains access
to that laptop is able to establish wireguard connections.
Of course, it can be argued that the laptop holds other information
which is more valuable that the wireguard key, therefore you should
concentrate on properly securing the laptop itself (*). Furthermore, to
be able to talk to the wireguard kernel module you're already root, and
therefore have all sorts of malicious options available to you. etc etc
But I'd feel a lot happier if a second level of authentication were
required to establish a wireguard connection, if no packets had been
flowing for more than a configurable amount of time - say, an hour. It
would give some comfort around lost/stolen devices.
Whilst I appreciate that wireguard is symmetrical, a common use case is
to have remote "clients" with a central "office". I'm thinking about a
hook whereby the "office" side could request extra authentication when
required - e.g. if it sees a connection from a wireguard public key
which has been idle for more than a configurable amount of time, then it
sends a challenge which requires (e.g.) a Yubikey to complete. I
appreciate that it's not going to be straightforward, requiring the
kernel module to talk to userland components at both ends.
In the absence of that, it would be nice if the private key which is
stored on the laptop were encrypted with a passphrase. Simplest option
may be to extend wg-quick so that the entire config file can be
(*) You could make a similar argument for ssh keys or pgp keys, saying
there's no need to protect them with a passphrase if the host they are
stored on is properly secured. I think many people would disagree.
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