ubuntu-phone team mailing list archive

[Thomas Voß <thomas.voss@xxxxxxxxxxxxx>]

On Thu, Mar 6, 2014 at 6:19 PM, Sebastien Bacher <seb128@xxxxxxxxxx> wrote:
> Hey everyone,
>
> That's a topic that has been discussed between different groups of people
> recently, on merge requests [1] and bug reports, and it feels like we should
> have the discussion on a common place/together, to decide what is best, and
> all do the same thing.
>
> Summary of the issue:
> - in unity8 we use the greeter as a lock screen
> - we want to have informations from the users available on the lock screen
> ("currently playing song" for example)
> - we need a way to get those informations from the session to the greeter
>
> We are currently using accountsservice to store "static" informations (e.g
> the background image for the user), that's needed because the user might not
> be logged/the directory not available to get the information otherwise. The
> case we are speaking about there is different and concerns "dynamic"
> informations (e.g the song currently playing in the user sessions)
>
> We have some solutions which have been suggested:
>
> 1. using accountsservice there as well, maybe adding support for "volatile"
> informations which wouldn't get store.
>
> That's the first suggestion made and some people started work using that
> approach. It feels suboptimal though, since it involves making 2 running
> processes talk by using a third process as proxy (which was not designed for
> that usecase).
>

Hmmm, I'm trying to see the issue why we wouldn't want to extend AS to
become a proxy for volatile data, too. Something has to proxy that
information, and AS seems to be the best fit from my pov, mostly due
to it already handling user-specific data.

>
> We discussed it a bit on #ubuntu-desktop and came with those possible
> solutions as well
>
>
> 2. get lightdm to connect to the user-session bus and send back selected
> informations to the greeter.
>
> That seems like the most flexible/powerful solution, giving access to the
> user session might be a concern for security though.
>
>

How is that different from (1.)? Lightdm becomes the proxy here, and I
don't think the display manager is the right place to handle static or
dynamic data.

> 3. having a subdirectory in the user's XDG_RUNTIME_DIR, which is visible to
> the greter via a privileged protocol in lightdm (lightdm opening files and
> sending content, or using fds are possible options)
>
> that should do the job, be easy enough and not risk exposing too much from
> the user session
>

It feels hacky to me to do it this way. Both from a security and from
a functional perspective.

Thomas

>
> Robert, what do you think of 2 and 3 from a lightdm perspective? Would you
> be happy to add support for one of those?
>
>
> Everyone, I've you have comments or extra ideas, feedback is welcome ;-)
>
> Cheers,
> Sebastien Bacher
>
>
> [1]
> https://code.launchpad.net/~ted/indicator-sound/account-service-support/+merge/205891
>
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