Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert

Martin Rex <mrex@sap.com> Wed, 09 June 2010 14:57 UTC

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From: Martin Rex <mrex@sap.com>
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To: mike-list@pobox.com (Michael D'Errico)
Date: Wed, 9 Jun 2010 16:56:46 +0200 (MEST)
In-Reply-To: <4C0FA538.7050309@pobox.com> from "Michael D'Errico" at Jun 9, 10 07:29:12 am
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Cc: tls@ietf.org
Subject: Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert
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Michael D'Errico wrote:
> 
> After reading this again, I think it's missing something.

I felt the same.

Another possible approach would be to slightly rearrange that part.

 "The ServerNameList MUST NOT contain more than one name of the same
  name_type.  If the server understood the client hello extension,

  but does not recognize the server name, the server has two options.
  Either abort the handshake sending a fatal unrecognized_name(112)
  alert or continue the handshake using a default credential.
  Sending a warning-level unrecognized_name(112) alert in the latter
  case is NOT RECOMMENDED, since existing client behaviour is
  unpredictable.


> > A TLS client implementation that receives a
> > warning-level unrecognized_name(112) alert SHOULD ignore this alert and
> > continue the TLS handshake.  If there is a mismatch between the server
> > name used by the client application and the server name of the default
> > credential chosen by the server, this mismatch will become apparent when
> > the client application performs the server endpoint identification, at
> > which point the client application will have to decide whether to
> > proceed with the communication.  TLS implementations are encouraged to
> > make information available to application callers about warning-level
> > alerts that were received or sent during a TLS handshake.  Such
> > information can be useful for diagnostic purposes."

-Martin