Re: [OAUTH-WG] security considerations for draft-ietf-oauth-mtls-12

I believe the standard approach to this is to only prompt for a client certificate in a renegotiation handshake rather than in the initial handshake. Renegotiations are encrypted under the existing TLS session.

— Neil

> On 1 Nov 2018, at 14:37, Brian Campbell <bcampbell=40pingidentity.com@dmarc.ietf.org> wrote:
> 
> To be honest, I thought that was a relatively well known aspect of TLS 1.2 (and prior) and a noted difference of the new features in TLS 1.3. Also, I'd note that we're well past WGCL for this document. But, with that said, I suppose adding some privacy considerations text on the subject is worthwhile. Would you propose some text for the WG to consider, John-Mark? Bearing in mind that the implications of a certificate presented by, and representing, an OAuth client are somewhat different than for an end-user doing client cert authentication. 
> 
> 
> 
> 
> On Wed, Oct 31, 2018 at 4:12 PM John-Mark Gurney <jmg+oauth@newcontext.com> wrote:
> I would suggest that the security considerations section of
> draft-ietf-oauth-mtls-12 be expanded to include the privacy
> implications of using this on versions of TLS before 1.3.  On all
> versions of TLS before 1.3, the client cert is not encrypted and can
> be used by third parties to monitor and track users.  I recently
> posted a blog entry about this:
> https://blog.funkthat.com/2018/10/tls-client-authentication-leaks-user.html
> 
> Thanks.
> 
> John-Mark Gurney
> 
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