TLS 1.3 non compliance with current draft

Hubert Kario <[email protected]> Fri, 01 Sep 2017 19:05:51 +0200

Newsgroups	gmane.comp.encryption.openssl.devel
Message-ID	<[email protected]>

When openssl sends a second Client Hello message, it modifies it quite 
extensively, not only client_random is changed but also advertised cipher 
suites.

see https://github.com/openssl/openssl/issues/4292

That makes it non-compliant with the current draft (-21):

   When a client first connects to a server, it is REQUIRED to send the
   ClientHello as its first message.  The client will also send a
   ClientHello when the server has responded to its ClientHello with a
   HelloRetryRequest.  In that case, the client *MUST send the same*
   *ClientHello* (without modification) except:

   -  If a "key_share" extension was supplied in the HelloRetryRequest,
      replacing the list of shares with a list containing a single
      KeyShareEntry from the indicated group.

   -  Removing the "early_data" extension (Section 4.2.9) if one was
      present.  Early data is not permitted after HelloRetryRequest.

   -  Including a "cookie" extension if one was provided in the
      HelloRetryRequest.

   -  Updating the "pre_shared_key" extension if present by recomputing
      the "obfuscated_ticket_age" and binder values and (optionally)
      removing any PSKs which are incompatible with the server's
      indicated cipher suite.


-- 
Regards,
Hubert Kario
Senior Quality Engineer, QE BaseOS Security team
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 115, 612 00  Brno, Czech Republic

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