Re: [Xen-devel] severe security issue on dom0/xend/xm/non-root users

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Kurt Garloff wrote:

> I agree.
>
> Currently xend just accepts every command that it receives.
> Not a good basis to grant role based permissions ...
>  
One approach to role based permissions is to have dom0 enforce 
policies.  Another approach is to enforce policies at the hypervisor 
level which is what sHype does.
One problem with any sort of Xend-level policies is managing 
authentication in a large network.  Especially if you start dealing with 
certificates (you've got to tie Xend into a larger certificate 
distribution system).
I think relying on local authentication is a useful approach.  Policies 
can be enforced at group/user granularities and you get every pam/nss 
based sign-on solution for free.
You're restricted by the Unix user model (small groups, no nested 
groups, etc.) but you gain an awful lot of additional functionality.
Regards,
Anthony Liguori

> So, we need to have some restrictions first, so tools can
> grant them for the right people.
>
> And my suggestion was binding to localhost only and requiring a port 
> < 1024 -- then you'd need to be a local user with CAP_NET_BIND_SERVICE 
> capability.  Granting additional rights by providing this capability 
> from a setuid root wrapper (or a PAM service that sets this on login)
> should not be too hard and straightforward enough to not introduce
> another load of security holes.
>
> The disadvantage of this is that it's a all or nothing approach.
> xend could be made more clever and require the user to show
> different certificates for different operations on different
> domains. But this is no short term solution.
>
> It would give a rather large matrix of certificates, one dimension
> being the kind of operation (list, restart, sysrq, balloon, scheduler,
> save/restrore, migrate, ...), another one being the domain. We could
> have master certificates for both directions, of course.
>
>
> Regards,
>  

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