Re: [Openvpn-devel] Progress on Version negotiation

[Timothe Litt]

On 23-Apr-14 06:56, Steffan Karger wrote:

Hi,

On 04/23/2014 10:10 AM, Gert Doering wrote:

On Tue, Apr 22, 2014 at 10:58:22PM -0400, Timothe Litt wrote:

It does not appear to be the negotiation, rather it's TLS1.2.

This is quite cool, thank you.  (I'm not enough of a crypto geek to
make real sense out of it, but it's quite useful to understand where
it is failing, and I appreciate that you took the time to dig into it)

Steffan, Arne, any ideas?

This sounds very plausible, yes.

I've seen situations in which an OpenSSL 2.3.3 client refuses to connect
to a PolarSSL 1.2.10 server. I tried to reproduce that in a test setup
last night, but did not manage make it break. So I'm still a bit in the
dark on the real cause.

For the 'fix the breaking asap', maybe we should add an
--tls-version-max if that really resolves the problem.

-Steffan

Just to confirm that the issue is 1.2, not the negotiation:

I added an unconditional
      sslopt |= SSL_OP_NO_TLSv1_2;
 in tls_ctx_set_options.


Without it, the tunnel does not come up.

So it is the use of 1.2 that is the issue, not how it is selected.



Let me know if you would like the full traces.

With this (and the context initialized to SSL_v23_*_method, so we negotiate), the tunnel comes up. I generated a matching pair of traces of the failure (client and server) & posted a summary. This is 100% reproducible here, so let me know if you need more instrumentation. (However, I can't build a windows client, so if that's necessary, you'll have to build it for me to run.)

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