RFC: root cert tool

[Juan Lang]

> As long as you don't try paths under /home, even a moderate amount of
> guessing seems safer than storing them in a user-writable file.

I'm not sure I agree.  If the threat model is a user doing dumb
things, there's no protection against that.  If the threat model is a
rogue Windows program installing bad CA certs, that particular attack
would only work in Wine.  Our install base is too small to consider
that likely.  If the threat model is a winelib program or an external
process installing bad CA certs, ditto.

> How many different paths are there really?

I don't know.  On my current machine, there are two equally probable
locations, depending on whether I'm looking for OpenSSL's certs or
Apache's.  On my laptop, there was one (different) location for
OpenSSL's certs for one distro version, and another (distinct yet
again) for another version of that distro.  So I haven't done a
complete sample, but on the three distros I've used within the last
year, there are at least three different locations.

I don't mean to imply that the limit of the number of locations as the
number of distros goes to infinity diverges, just that I haven't found
a strict upper bound yet.

--Juan