Bug#769961: hard-coded UIDs and GIDs

[Ivo De Decker <ivodd@debian.org>]

Hi,

First of all, please don't break threads.

On Tue, Dec 09, 2014 at 08:35:03PM +0100, Hans-Christoph Steiner wrote:
> I think you don't understand the situation with the Android kernel. 

I think I do.

> There are hard-coded UIDs and GIDs in the kernel itself that represent the
> Android permissions, and special Android processes.  When running Debian on
> top of an Android kernel, those UIDs and GIDs cannot be changed.

I understand that.

> So not changing the UID/GID stuff in Debian is actually the risky thing to
> do.

I disagree. The problem is that android-permissions can be installed on
existing systems (not running on android) as well. Blindly changing uid/gid
there is a very bad thing to do. Even on systems running in a chroot on
android, this shouldn't be changed as a result of installing a package.

> For example, by default, the first user account that Debian creates is UID
> 1000.  That is the GID of the Android 'system' permission, granting wide
> ranging permissions to the system.  I doubt anyone wants to grant the first
> user such permissions, both automatically and unchangeably.

I guess you will agree that blindly changing the uid of an existing user can
never be a good thing to do. If this uid needs to be changed, the admin of the
system needs to be aware of this, and probably clean up afterwards.

> Another example is that if the Debian 'audio' GID does not match Android
> 'audio' GID, the Debian 'audio' group will never be able to grant permissions
> to use the audio devices.

> As for installing android-permissions with debootstrap, that's how this
> package is used.  And it turns out that there are system groups already
> created by the time debootstrap installs android-permissions.  That is why I
> made that change.

Is there a way to avoid this, by having debootstrap install
android-permissions earlier in the boot process? Having the groups created
with a certain hardcoded id (the one used by the android kernel) is one thing.
Changing it on the fly is something else.

Cheers,

Ivo