Re: [Libguestfs] [libvirt] [PATCH libguestfs 0/4] Add a libvirt backend to libguestfs.

On Mon, Jul 23, 2012 at 10:45:21AM +0100, Daniel P. Berrange wrote: > On Sat, Jul 21, 2012 at 09:43:45PM +0100, Richard W.M. Jones wrote: > > On Sat, Jul 21, 2012 at 08:20:45PM +0100, Richard W.M. Jones wrote: > > > Some questions: > > > > Another question ... > > > > > <channel type="unix"> > > > <source mode="connect" path="/home/rjones/d/libguestfs/libguestfsSSg3Kl/guestfsd.sock"/> > > > <target type="virtio" name="org.libguestfs.channel.0"/> > > > </channel> > > > > This clause doesn't work when libguestfs/qemu runs as root. As far as > > I can tell there are a combination of three factors working against it: > > > > (1) libvirt (when run as root) runs qemu as qemu.qemu. Since this > > user didn't have write access to the socket, it fails. I fixed this > > by chowning the socket. > > What libvirt URI are you using ? If libguest is running as non-root, > then I expect you'd want to use qemu:///session. It's using NULL and expecting libvirt to choose the appropriate connection URI, which does appear to work.

> Thus all files would be owned by the matching user ID, and I'd > sugest $HOME/.libguestfs/qemu for the directory to store the sockets > in. > > If libguestfs is running as root, then use qemu:///system and a socket > under /var/lib/libguestfs/qemu/ This is fairly sucky. We already make a temporary directory (a randomly named subdirectory of $TMPDIR) and that seems the appropriate place for small temporary files like sockets, especially since the temp cleaner will clean them up properly if we don't. > You could either use the same directory that libvirt uses for the > main QEMU monitor socket, or preferrably define standard directories > for libguestfs and have them added to the SELinux policy So just so I'm completely clear about what's happening: (1) SELinux labels are chosen based on the parent directory.

(2) By having a standard named parent directory (even $HOME/.libguestfs) SELinux will assign the right label to a socket in this directory, even if libguestfs is not running as root.

(3) libguestfs should not be setting labels on anything itself.

(4) If a non-root user has never run libguestfs before, then merely the act of libguestfs doing mkdir("$HOME/.libguestfs") [as non-root] will ensure that any sockets in this directory are labelled correctly.