Subject: [TLS] TLS Security Policy Draft Update

From: Phillip Hallam-Baker <[email-masked]>
Date: Fri, 19 Oct 2012 21:08:28 -0400

http://www.ietf.org/id/draft-hallambaker-tlssecuritypolicy-02.txt

I am not proposing this as a PKIX WG item as the plan is to close the
group. It may be of interest to PKIX and TLS members however.

This is a slight generalization of the 'MUST STAPLE' certificate and CSR
extension. Specifically the specification permits two types of security
policy to be specified in an X.509v3 cert.

* Minimum TLS Version
* 'Must Staple OCSP token'

The design is slightly more general so that it can co-exist with TLS
extensions that are similar to OCSP token stapling. For example Certificate
Transparency info.

The big advantage to using this is that it allows a client to check
revocation status and to immediately fail if the OCSP token is not provided
as it should be. At present most clients will only fail if they see an
invalid OCSP token, if the token is not returned, they consider it valid.
To do otherwise opens the client to a DoS attack bu DDoS-ing the OCSP
servers.

Note that the TLS protocol handshake provides protection against most forms
of downgrade attack and most importantly cipher suite downgrade (for later
versions at least). So it is not necessary to wire them into the cert. In
fact the only statements that should be wired into the cert are statements
that the server knows that it can ensure compliance with.

-- 
Website: http://hallambaker.com/