[PATCH 3/8] apparmor: allow virt-aa-helper nameservices

[Jamie Strandboge]

On Mon, 03 Aug 2020, Christian Ehrhardt wrote:

> Since quite a while libvirt-aa-helper triggers nss related apparmor
> denials like:
>  operation="open" profile="virt-aa-helper" name="/etc/nsswitch.conf"
>  operation="open" profile="virt-aa-helper" name="/etc/host.conf"
>  operation="open" profile="virt-aa-helper" name="/etc/resolv.conf"
>  operation="open" profile="virt-aa-helper" name="/etc/hosts"
> 
> Rules to allow these are in Debian [1] / Ubuntu [2] since quite a
> while but do not seem to be specific to those distributions.
> 
> There can be much more reasons than one would think to inadvertently
> use/trigger nameservices as can be seen in the comments in
> profiles/apparmor.d/abstractions/nameservice at [3].
> The nameservices abstraction provides a nice and upgrade safe
> way to cover all of them.
> 
> [1]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=882979
> [2]: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1546674
> [3]: https://gitlab.com/apparmor/apparmor
> 
> Signed-off-by: Christian Ehrhardt <christian.ehrhardt at canonical.com>
> ---
>  src/security/apparmor/usr.lib.libvirt.virt-aa-helper.in | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/src/security/apparmor/usr.lib.libvirt.virt-aa-helper.in b/src/security/apparmor/usr.lib.libvirt.virt-aa-helper.in
> index dd18c8ab89..dfc61e8de4 100644
> --- a/src/security/apparmor/usr.lib.libvirt.virt-aa-helper.in
> +++ b/src/security/apparmor/usr.lib.libvirt.virt-aa-helper.in
> @@ -2,6 +2,7 @@
>  
>  profile virt-aa-helper @libexecdir@/virt-aa-helper {
>    #include <abstractions/base>
> +  #include <abstractions/nameservice>

nameservice brings in network rules so this is actually a lot of access.
Why is it reaching out to nss? Is it just cause some library happens to
look at /etc/nsswitch.conf and pull in other things or does it actually
need networking? I suspect the former. If my suspicion is true, perhaps
instead:

  # virt-aa-helper dependent libraries read (and if successful, other
  # files) but virt-aa-helper itself doesn't require the access, so
  # silence the denial.
  deny /etc/nsswitch.conf r,

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