On 07/26/2012 10:30 AM, rmarwah@linux.vnet.ibm.com wrote:
Quoting Jamie Strandboge <jamie@canonical.com>:
On Mon, 2012-07-09 at 10:22 -0400, rmarwah@linux.vnet.ibm.com wrote:
Quoting Jamie Strandboge <jamie@canonical.com>:
Quoting Jamie Strandboge <jamie@canonical.com>:
On Fri, 2012-06-29 at 14:08 -0400, rmarwah@linux.vnet.ibm.com wrote: > From: Richa Marwaha <rmarwah@linux.vnet.ibm.com> > > 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@linux.vnet.ibm.com> > Signed-off-by: Corey Bryant<coreyb@linux.vnet.ibm.com> > --- > 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
On Tue, 2012-07-03 at 12:05 -0400, rmarwah@linux.vnet.ibm.com wrote: 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.
Right now the only way we can think of is that whenever in domain XML we see interface=bridge we set the policy for the qemu-bridge-helper even though we don't know if the qemu-bridge-helper is going to be used or not.
Ah, well, that would at least be somewhat better and IMHO, worthwhile.
Hi Jamie I started testing out the policy generation with the approach that if it checks inteface=bridge then only we generate the qemu-bridge-helper policies. I found 2 issues while trying to do that 1) There are a lot of ways to start bridge helper and the way libvirt is starting it is using -netdev bridge br=br0 and the executable is started by the qemu and not libvirt. So the way I can think of changing the path at compile time is to search for the executable in /usr/. Not being a big fan of this approach for searching the executable.
Can you add a new tag to the domain XML that allows specification of the helper executable path? For example, adding <helper>: <interface type='bridge'> <source bridge='br0'/> <helper='/usr/libexec/qemu-bridge-helper' /> </interface> That would translate to something like: qemu-kvm -netdev bridge,helper=/usr/libexec/qemu-bridge-helper,br=br0,id=xyz -device ... -- Regards, Corey