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Re: Limiting the power of packages




* Simon McVittie:

> On Thu, 04 Oct 2018 at 08:34:15 +0200, Florian Weimer wrote:
>> * Paul Wise:
>> > To fully solve the problem you need a whitelist based approach that
>> > ends up something completely different like Flatpak.
>> 
>> Flatpaks don't work this way.  Try installing gedit and open a file
>> like ~/.ssh/id_rsa with it.  There are no security prompts whatsoever,
>> yet the software in a flatpak can read your SSH private key.
>
> That particular app's whitelist presumably includes "share the entire
> host filesystem"; the existence of a whitelist doesn't mean the whitelist
> isn't large. General-purpose development tools and text editors generally
> have larger whitelists than more limited apps, with GNOME Builder at
> the extreme of least-confined.

The other problem is that the whitelist comes from the application
author, so it's like asking a drunk whether they are drunk.

> % flatpak --user install flathub org.gnome.gedit
> Installing in user:
> org.gnome.Platform.Locale/x86_64/3.28 flathub 2823e3d81b74
> org.gnome.gedit/x86_64/stable         flathub a03b66681bce
>   permissions: ipc, wayland, x11
>   file access: host, xdg-run/dconf, ~/.config/dconf:ro
>                ^^^^
>                 \- this is why it can read arbitrary files
>   dbus access: ca.desrt.dconf, org.gtk.vfs.*
> org.gnome.gedit.Locale/x86_64/stable  flathub c2974b37ef08
> Is this ok [y/n]:
>
> I think the intention is that GUIs like GNOME Software prompt for apps
> that need special permissions in a more user-friendly way, something
> like how Android handles app permissions, although I don't think that's
> actually implemented yet.

Yes, I tried this on Fedora 28 before posting, which I consider the
reference implementation.  There is no security prompt at all.

I've also been told in an other context that it is up to the Flatpak
repository to vet the permissions requested by the software authors.
This model would be closer to what the Debian archive does in
practice.

> I don't know specifically why gedit has the host file access
> permission: it's unnecessary for File->Open and File->Save
> As... (e.g. org.gnome.Recipes is a good example of an app that
> doesn't, but can still import and export recipes) but presumably some
> of gedit's IDE-like features involve opening files other than the one
> you directly asked for.

I assume it's because gedit creates backup files when saving, and the
document portal does not support that.