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

On Tue, 2012-07-03 at 12:05 -0400, rmarwah(a)linux.vnet.ibm.com wrote: > Quoting Jamie Strandboge <jamie(a)canonical.com&gt;: > > > 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). > > Thanks a lot reviewing the apparmor patch. We cannot detemine from the > domain XML whether /usr/libexec/qemu-bridge-helper will be used or not > because we cannot determine whether we are running as privileged user > or not. Hmmm, that's too bad. > Is there a way we can specify the configured path to the > binary in the current policy we have? Not in a convenient way, no. The policy is intended as example policy anyway, and distributions are expected to modify this, so I don't think this alone is a blocker.

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