Re: [tsvwg] [saag] Fwd: Last Call: <draft-ietf-tsvwg-transport-encrypt-19.txt> (Considerations around Transport Header Confidentiality, Network Operations, and the Evolution of Internet Transport Protocols) to Informational RFC

[Tom Herbert <[e-mail]>]

On Thu, Feb 11, 2021 at 11:40 AM Fernando Gont <[e-mail]> wrote:
>
> On 11/2/21 15:18, Tom Herbert wrote:
> [...]
> >
> > When the transport layer is encrypted, network devices would only see
> > the plaintext EH and that is only what that is what they can act on.
> > At the destination, we could try to rectify transport information in
> > HBH with decrypted plaintext transport headers, but I suspect that
> > wouldn't typically be done. The HBH information is only operationally
> > useful to the network, not the transport endpoints that have access to
> > the transport header.
>
> Then this is what an attacker would do:
> He/she would advertise on a HBH option something that looks sensible to
> the guy enforcing a network-based security policy, and then at transport
> would do what he/she needs to do. :-)
>
>
> e.g., HBH could advertise that my packets are directed to ports 80/443,
> while in transport they are actually directed to port, say, 22.
>
It's more likely that information in the HBH would be generic and
abstract, afterall the whole point of encrypting the transport header
is to hide information from the network that it doesn't require, not
to just blindly volunteer the same information somewhere else in the
packet. Port numbers, for instance, are not required for delivery and
in fact are prone to misinterpretation in the network (RFC7605)-- IMO
it makes no sense to put those in a HBH option.

Regardless of HBH though, if the preponderence of transport headers
are encrytped then network security policiy that relies on the
information will need to change.

Tom

>
>
> > The only point of the end host comparing the
> > data would be to enforce the network's security policy, but it's not
> > common that end hosts actually know what the network security policies
> > are.
>
> The point for the end-node comparing both values is so that it makes
> sense in the first place to enforce a security policy based on e.g.
> HBH-conveyed information.
>
> Otherwise, the operator/admin knows that attackers will do what I'd
> suggested above, and they wouldnt even bother to try to enforce security
> policy which is circumvent-able  "by design", so to speak :-)
>
> If consistence cannot be guaranteed, then the mechanism won't be useful
> for enforcing security policies.
>
> Thanks,
> --
> Fernando Gont
> SI6 Networks
> e-mail: [e-mail]
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
>
>
>