Re: [saag] [tsvwg] 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

Fernando Gont <fgont@si6networks.com> Thu, 11 February 2021 18:40 UTC

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To: Tom Herbert <tom@herbertland.com>
Cc: Gorry Fairhurst <gorry@erg.abdn.ac.uk>, "Black, David" <David.Black@dell.com>, Fernando Gont <fernando@gont.com.ar>, Benjamin Kaduk <kaduk@mit.edu>, "saag@ietf.org" <saag@ietf.org>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Thu, 11 Feb 2021 15:40:02 -0300
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Subject: Re: [saag] [tsvwg] 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
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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.



> 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: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492