Re: [9fans] Solo factotum (was: Enterable namespaces: /proc/pid/$ns/srv)

["sirjofri via 9fans" <9fans@9fans.net>]

29.12.2025 14:03:55 David Arroyo <droyo@aqwari.net>:
> On Sun, Dec 14, 2025, at 07:43, sirjofri wrote:
>> More ideally, but also offtopic, I's like to have a factotum usb drive,
>> where the secrets never leave the usb device. It would talk 9p directly
>> over the serial bus.
>
> I think this is a great idea; an HSM-like device with an interface that
> doesn't suck. After some discussion about this idea on IRC, I want to
> try and implement it.

That sounds cool and I can't wait for the results.

> It has a capacitive button
> which would work nice with the `confirm` attribute of factotum to require
> human presence before using a key.

Somehow funny that factotum has this feature that's described in the fido standard years later.

> I'm trying to figure out how to serve 9P over USB, which I know very
> little about.  My initial plan is to make the device a USB serial
> device that expects 9P, then try to mount the /dev/eiaUN device.
> However, nusb(4) states that the nusb/serial driver only works for two
> chips, so I'd have to add support for this one.  That's not a problem,
> but am I going in the right direction?

I don't know much about USB, though maybe the nusb/serial restriction only applies for real rxtx serial converters or something? I mean, USB is serial by its nature so any communication is serial, I guess... But I also don't know. However, being able to mount 9p from a USB serial line would be interesting for many use cases.

For the factotum key, another complex issue could be that factotum needs access to the network interface for auth stuff. I was thinking about this, and plan 9 makes it possible to solve this. One could for example put the /net of the host into a /srv of the factotum key, or something like that. In any case, this is a challenge to find a good and clean solution.

sirjofri.

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