permissions required on /run/user/<uid>/gnupg

[Daniel Kahn Gillmor]

On Thu 2016-10-06 05:17:57 -0400, Justus Winter wrote:
> Daniel Kahn Gillmor <dkg at fifthhorseman.net> writes:
>
>>> I fact, would like to entirely get rid of sockets in the homedir.  We
>>> still need them for compatibility reasons but in the long term they
>>> should go away.
>>
>> I'd love for them to go away as well!
>
> Oh?  What about all the people not using systemd?

there's nothing that makes /run/user/<uid>/ systemd-specific.  having an
ephemeral chunk of the local filesystem that only your user can write to
that *isn't* your homedir is useful for lots of reasons, not least of
which are:

 * people with NFS-mounted homedirs, who can't effectively use the same
   socket in ~/.gnupg on two different machins

 * accounts with read-only home directories

 * accounts with no home directories at all

Consider it a chunk of working space that you can use to coordinate
processes on the same machine without needing to touch the disks,
without worrying about access by other users, and without worrying about
cleanup after poweroff.

If your operating system supports ephemeral, in-ram filesystems (An OS
with the Linux kernel would call it "tmpfs", i dunno what it's called on
other kernels), why *not* have such a mountpoint?

On the Linux kernel since version 2.2, we do have another such option,
which would be to use the abstract sockets namespace, but that would
require an entirely different permissions model, and would be a chunk of
non-portable code.

> Fwiw, I do not like that GnuPG automagically uses /run/users/X if it
> exists, because everytime I accidentally install some package that pulls
> in the systemd component that creates these directories, my gnupg setup
> breaks.  Yes, it is my fault for expecting the sockets to be created in
> ~/.gnupg, and yes, there is gpgconf that I should ask instead, but I
> still consider it very surprising that installing a seemingly unrelated
> package changes GnuPGs behavior like that.

I agree with you that this behavior change is frustrating.  You can
avoid the behavior change by just keeping /run/user/<uid>/ around in
perpetuity ;)

           --dkg
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