Re: [PATCH v9] virtio-net: support inner header hash

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Feb 23, 2023 at 10:50:48AM +0800, Jason Wang wrote:
> Hi:
> 
> å 2023/2/22 14:46, Heng Qi åé:
> > Hi, Jason. Long time no see. :)
> > 
> > å 2023/2/22 äå11:22, Jason Wang åé:
> > > 
> > > å 2023/2/22 01:50, Michael S. Tsirkin åé:
> > > > On Sat, Feb 18, 2023 at 10:37:15PM +0800, Heng Qi wrote:
> > > > > +\subparagraph{Security risks between encapsulated packets and RSS}
> > > > > +There may be potential security risks when encapsulated
> > > > > packets using RSS to
> > > > > +select queues for placement. When a user inside a tunnel
> > > > > tries to control the
> > > 
> > > 
> > > What do you mean by "user" here? Is it a remote or local one?
> > > 
> > 
> > I mean a remote attacker who is not under the control of the tunnel
> > owner.
> 
> 
> Anything may the tunnel different? I think this can happen even without
> tunnel (and even with single queue).

I think you are missing the fact that tunnel is normally a
security boundary: users within the tunnel can not control
what is happening outside.
The feature breaks the encapsulation somewhat.

For example without tunneling it is possible
to create a special "bad guy queue" and direct specific tunnels
there by playing with key and indirection table.

> How to mitigate those attackers seems more like a implementation details
> where might require fair queuing or other QOS technology which has been well
> studied.
> 
> It seems out of the scope of the spec (unless we want to let driver
> manageable QOS).
> 
> Thanks
> 
> 
> > 
> > Thanks.
> > 
> > > 
> > > > > +enqueuing of encapsulated packets, then the user can flood
> > > > > the device with invaild
> > > > > +packets, and the flooded packets may be hashed into the
> > > > > same queue as packets in
> > > > > +other normal tunnels, which causing the queue to overflow.
> > > > > +
> > > > > +This can pose several security risks:
> > > > > +\begin{itemize}
> > > > > +\item Encapsulated packets in the normal tunnels cannot be
> > > > > enqueued due to queue
> > > > > +ÂÂÂÂÂÂ overflow, resulting in a large amount of packet loss.
> > > > > +\item The delay and retransmission of packets in the
> > > > > normal tunnels are extremely increased.
> > > > > +\item The user can observe the traffic information and
> > > > > enqueue information of other normal
> > > > > +ÂÂÂÂÂÂ tunnels, and conduct targeted DoS attacks.
> > > > > +\end{\itemize}
> > > > > +
> > > > Hmm with this all written out it sounds pretty severe.
> > > 
> > > 
> > > I think we need first understand whether or not it's a problem that
> > > we need to solve at spec level:
> > > 
> > > 1) anything make encapsulated packets different or why we can't hit
> > > this problem without encapsulation
> > > 
> > > 2) whether or not it's the implementation details that the spec
> > > doesn't need to care (or how it is solved in real NIC)
> > > 
> > > Thanks
> > > 
> > > 
> > > > At this point with no ways to mitigate, I don't feel this is something
> > > > e.g. Linux can enable. I am not going to nack the spec patch if
> > > > others find this somehow useful e.g. for dpdk.
> > > > How about CC e.g. dpdk devs or whoever else is going to use this
> > > > and asking them for the opinion?
> > > > 
> > > > 
> >