Re: [9fans] factotum vs. SASL+TLS+applications

[Ori Bernstein <ori@eigenstate.org>]

> The following is all hypothetical.  I'm curious about how people
> think auth(2)/factotum(4) could be adapted to support the use
> case ...
> 
> factotum was intended to handle the authentication dance on behalf
> of network apps. But in the case of things like IMAP, it really
> just stores the client's login/password, and provides a bit of
> helper glue for CRAM-MD5. Similarly for ftpfs.
> 
> I'm curious why upasfs and ftpfs are outliers in only using factotum
> as a credential store, but leaving the actual authentication protocol
> dance in the clients/servers.  The "Security" paper (/sys/doc/auth)
> strongly hints that these parts of the application protocols were
> meant to be outsourced to factotum.  Section 2.2 in particular
> argues that the auth modules should be implemented once in factotum,
> for consumption by the rest of the system.

Probably simple expediency.
 
> <snip>
>
> To require a specific SASL mechanism, add "sasl=scram-md5" (using
> "sasl=*" as a default if you need to fall back for some reason).

This all sounds fairly reasonable. I think that patches to this effect
would be worth integrating.

> Of course all of this needs to be glued into auth(2) in a way that
> doesn't destroy the existing API.  But it does need to handle
> factotum replacing the underlying connection to the client/server
> with one that has been pushtls()ed by factotum itself.

I'm not sure how factotum can have this action at a distance. I think
the pushtls is stuck in the client itself -- though, the auth code can
probably return the parameters needed for this.