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

"Joseph Salowey (jsalowey)" <jsalowey@cisco.com> Mon, 07 June 2010 20:08 UTC

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Date: Mon, 7 Jun 2010 13:08:55 -0700
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Thread-Topic: [TLS] RFC-4366-bis and the unrecognized_name(112) alert
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References: <4C092737.2060604@pobox.com> from "Michael D'Errico" at Jun 4, 10 09:17:59 am <201006041647.o54Gl4iH024692@fs4113.wdf.sap.corp> <AC1CFD94F59A264488DC2BEC3E890DE50A9EDDA1@xmb-sjc-225.amer.cisco.com> <4C09C4EC.1070903@pobox.com> <4C09F856.2030407@gnutls.org> <4C0A6852.5040001@pobox.com>
From: "Joseph Salowey (jsalowey)" <jsalowey@cisco.com>
To: "Michael D'Errico" <mike-list@pobox.com>, "Nikos Mavrogiannopoulos" <nmav@gnutls.org>
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Subject: Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert
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<snip>
> 
> It should be in both places, especially since there won't be another
> update to the main spec for several years.
> 
[Joe] 4366-bis does not update 5246.  Right now we need to focus on
resolving this issue for SNI so we can get the document out. 

> The problem seems to be that the names given to alert levels both
sound
> bad.  Really what they mean are "fatal" and "non-fatal" but since the
> name "warning" was chosen as the label, implementers who haven't
thought
> much about it decide that warning == bad, so they escalate it to
fatal.
> 
> They need to be told that warning alerts should not automatically be
> treated as fatal, but should be ignored by default.  If they have gone
> through an analysis and determined that a particular warning alert is
> really fatal for them, then they are justified in aborting the
handshake
> when they see that particular warning.
> 
> > My version of how the text should be is:
> >
> > (1) "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, and it refuses to continue it MUST
send a
> > fatal unrecognized_name(112) alert and terminate the handshake.
> > The server might decide to continue the  handshake, but in that case
it
> > is NOT RECOMMENDED send any warning alert. Clients SHOULD be
prepared to
> > receive and ignore the unrecognized_name(112) alert with warning
level.
> 
> I could live with this text.  I would also like section 9 (Error
Alerts)
> to mention that warning alerts should be treated as informational
(non-
> fatal) by default to help avoid similar problems in the future.
> 
> Mike