Re: [libvirt] [Patch v2 3/3] apparmor: QEMU bridge helper policy updates

On Fri, 2012-06-29 at 14:08 -0400, rmarwah(a)linux.vnet.ibm.com wrote: > From: Richa Marwaha <rmarwah(a)linux.vnet.ibm.com&gt; > > This patch provides AppArmor policy updates for the QEMU bridge helper. > The QEMU bridge helper is a SUID executable exec'd by QEMU that drops > capabilities to CAP_NET_ADMIN and adds a tap device to a network bridge. > > Signed-off-by: Richa Marwaha <rmarwah(a)linux.vnet.ibm.com&gt; > Signed-off-by: Corey Bryant&lt;coreyb(a)linux.vnet.ibm.com&gt; > --- > examples/apparmor/libvirt-qemu | 21 ++++++++++++++++++++- > 1 files changed, 20 insertions(+), 1 deletions(-) > > diff --git a/examples/apparmor/libvirt-qemu b/examples/apparmor/libvirt-qemu > index 10cdd36..766a334 100644 > --- a/examples/apparmor/libvirt-qemu > +++ b/examples/apparmor/libvirt-qemu > @@ -1,4 +1,4 @@ > -# Last Modified: Mon Apr 5 15:11:27 2010 > +# Last Modified: Fri Mar 9 14:43:22 2012 > > #include <abstractions/base> > #include <abstractions/consoles> > @@ -108,3 +108,22 @@ > /bin/dash rmix, > /bin/dd rmix, > /bin/cat rmix, > + > + /usr/libexec/qemu-bridge-helper Cx, > + # child profile for bridge helper process > + profile /usr/libexec/qemu-bridge-helper { > + #include <abstractions/base> > + > + capability setuid, > + capability setgid, > + capability setpcap, > + capability net_admin, > + > + network inet stream, > + > + /dev/net/tun rw, > + /etc/qemu/** r, > + owner @{PROC}/*/status r, > + > + /usr/libexec/qemu-bridge-helper rmix, > + } Looking at the child profile itself, this seems fine. However, the Cx transition makes it so that all libvirt-managed qemu processes are allowed to execute this setuid helper and I wonder if that is too much? Ie, a guest running under libvirt's NAT wouldn't need access to this helper at all. I wonder if it would be better to adjust virt-aa-helper to add this transition and child profile instead (the child profile could theoretically still be in apparmor/libvirt-qemu, but this is a bit messy)? Can we determine from the domain XML the circumstances when /usr/libexec/qemu-bridge-helper will be used? If so, virt-aa-helper could add the access only then. As a side-benefit, handling this in virt-aa-helper allows us at compile-time to adjust the path to qemu-bridge-helper to use the configured path to the binary (ie, some distros may not use /usr/libexec).

-- Jamie Strandboge | http://www.canonical.com