Re: [TLS] How ALPN makes the http2-tls-relaxed option less secure, compared to NPN (was Re: ALPN concerns)

Alfredo Pironti <alfredo@pironti.eu> Mon, 09 December 2013 15:23 UTC

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Date: Mon, 9 Dec 2013 16:23:11 +0100
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From: Alfredo Pironti <alfredo@pironti.eu>
To: Brian Smith <brian@briansmith.org>
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Cc: Peter Gutmann <p.gutmann@auckland.ac.nz>, "<tls@ietf.org>" <tls@ietf.org>
Subject: Re: [TLS] How ALPN makes the http2-tls-relaxed option less secure, compared to NPN (was Re: ALPN concerns)
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> The case where the server does not use a certificate that the client
> would verify correctly as it would in the "normal" HTTPS case is not
> interesting. However, the case where opportunistic encryption is being
> used with a certificate that *is* valid (as defined by RFC5280, et
> al.) is interesting.

I think this pre-condition makes your counter-example invalid.
A client that only accepts valid certificates is in practice only
implementing http2, not http2-tls-relaxed, in that client's behavior
doesn't change.

>
> Note that the choice between "http2-tls-relaxed" and "http2" only
> affects (AFAICT) the validation of the certificate.

Indeed, but under the assumption that only valid certificates are
accepted, the behaviors coincide to "http2".

Best,
Alfredo