A few weeks back I posted some prototype patches for PolicyKit support to
allow the main libvirt daemon socket to be made world-accessible. PolicyKit
then can do ACLs on incoming connections, allowing definition of rules which
could for example, allow only the user who owns the active X login sesion
http://www.redhat.com/archives/libvir-list/2007-August/msg00027.html
This is an updated patch which takes account of a change in the PolicyKit
XML file syntax between 0.4 and 0.5 releases.
The configure.in scripts has been tweaked to automatically disable PolicyKit
if pkg-config is not available instead of aborting.
The code for getting UNIX socket credentials has been factored out into its
own method. There is still only a Linux implementation. I was going to take
the code for other OS from DBus, but DBus is currently under a GPL/Academic
license options, which is not compatible with LGPL. Fortunately DBus is in
middle of re-licensing to X11 style which is LGPL compatible, so in a week
or so's time we'll be able to safely take their OS portability code for
socket credentials.
I short-circuit the logic to always allow root. This allows existing people
running libvirt tools as root to continue use without any regressions. There
is one small issue still that the default policy I provide only allows the
use of read-only connections if the user is logged into to the desktop. This
is a partial regression - the admin can edit /etc/PolicyKit/PolicyKit.conf
and add a site-local rule allowing all users access, regardless of whether
they're in a session. I've spoken with David Zeuthan and he's going to add
ability to specify rules for non-session clients in the default policy
config files, which will fix this minor regression. Once this is done the
libvirt default policy will be identical to current file permission based
policy (root == full access, non-root == read only).
As I mentioned previously, with this change it is now possible to open a full
read-write connection from virt-manager running as non-root. Depending on
site policy it will optionally prompt for root password (su style equiv) or
the user's password (sudo style equiv) without needing virt-manager itself
to gain any elevated privileges.
When compiling with PolicyKit support, the default file permissions for both
the main & readonly UNIX sockets in the daemon switch to 0777, instead of
the previous 0700 & 0777. It is possible to turn off PolicyKit auth in the
daemon config file, even if it is compiled in - in which case the default
permissions get set back to 0700 & 0777.
Although in previous feedback Daniel suggested I leave the LIBVIRTD_AUTH_POLKIT
constant compiled in all the time, I feel it is better to remove it when the
policykit support is disabled in configure. This removes the need to have
extra switch/case statements to explicitly reject LIBVIRTD_AUTH_POLKIT auth,
since it will be handle by the 'default:' statement which already has code
to reject connections.
I've done more extensive testing with virt-manager since my previous patch,
and its working very nicely with the new UI which allows multiple hypervisor
connections. Instead of asking for the root password up-front at app start
time, we now only need ask for it if the user connects to a local HV. If
they only ever manage remote connections we don't need to do anything with
the local root password.
Dan.
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