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

Michael D'Errico <mike-list@pobox.com> Wed, 09 June 2010 17:13 UTC

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Date: Wed, 09 Jun 2010 10:13:48 -0700
From: Michael D'Errico <mike-list@pobox.com>
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To: "Joseph Salowey (jsalowey)" <jsalowey@cisco.com>
References: <4C0FA538.7050309@pobox.com> from "Michael D'Errico" at Jun 9, 10 07:29:12 am <201006091456.o59EukJ3015376@fs4113.wdf.sap.corp> <AC1CFD94F59A264488DC2BEC3E890DE50AA7E552@xmb-sjc-225.amer.cisco.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert
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I agree Martin's text is better than mine.  But I'd like to modify
it slightly:

    Sending a warning-level unrecognized_name(112) alert in the
    latter case is allowed, but NOT RECOMMENDED since .....
                ^^^^^^^^^^

Mike


Joseph Salowey (jsalowey) wrote:
> Thanks,  
> 
> The text below looks much better looks much better. Let's go with that. 
> 
> Joe
>> -----Original Message-----
>> From: Martin Rex [mailto:mrex@sap.com]
>> Sent: Wednesday, June 09, 2010 7:57 AM
>> To: Michael D'Errico
>> Cc: Joseph Salowey (jsalowey); tls@ietf.org
>> Subject: Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert
>>
>> 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
>

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