Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (Transport Layer

I think this text is helpful and does belong to RFC 4366bis. TLS is a tool.
This is a piece of information how to avoid a pitfall when using this tool.

Which does not preclude from writing a lengthier document - a guide for
application developers.

On 9/30/09  12:51 , "Peter Saint-Andre" <stpeter@stpeter.im> wrote:

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> On 9/30/09 10:45 AM, Joseph Salowey (jsalowey) wrote:
>>  
>> 
>>> -----Original Message-----
>>> From: Simon Josefsson [mailto:simon@josefsson.org]
>>> Sent: Tuesday, September 29, 2009 10:20 PM
>>> To: Joseph Salowey (jsalowey)
>>> Cc: Michael D'Errico; martin.rex@sap.com; ietf@ietf.org; tls@ietf.org
>>> Subject: Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis
>>> (Transport Layer
>>> 
>>> "Joseph Salowey (jsalowey)" <jsalowey@cisco.com> writes:
>>> 
>>>> It seems that this is really up to the application.  Both
>>> server names 
>>>> are authenticated under the same session.  It seems an application
>>>> server may require them to be the same or allow them to be
>>> different.   
>>> 
>>> I would agree if the draft wouldn't prevent clients from
>>> requesting a different server name at the application layer:
>>> 
>>>    negotiated in the application protocol. If the server_name is
>>>    established in the TLS session handshake, the client SHOULD NOT
>>>    attempt to request a different server name at the
>>> application layer.
>>> 
>>> At least that is how I read it.
>>> 
>> [Joe] Good point, however I still think it is application protocol that
>> needs to enforce the matching if it cares.  Perhaps we can add some text
>> that states
>> 
>> "Since it is possible for a client to present a different server_name in
>> the application protocol, application server implementators should take
>> this into account and take appropriate action to avoid introducing
>> security vulnerabilities if the names do not match.  "
> 
> I think that text is helpful. Overall, however, I wonder if this is
> something that truly belongs in rfc4366bis or if it is more appropriate
> to define a set of best practices for application protocols that use
> TLS. A group of folks in the Apps Area has started to do that here:
> 
> http://tools.ietf.org/html/draft-saintandre-tls-server-id-check
> 
> It can't hurt to place a brief warning in the core TLS spec, though.
> 
> Peter
> 
> - --
> Peter Saint-Andre
> https://stpeter.im/
> 
> 
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-- 
Regards,
Uri         uri@ll.mit.edu
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