Hi,

On 2 Dec 2014, at 17:55, Yaron Sheffer <[email protected]> wrote:

>>>>>>> This document is not an application profile standard, in the sense of
>>>>>>>   Section 9 of [RFC5246].  As a result, clients and servers are still
>>>>>>>   REQUIRED to support the mandatory TLS cipher suite,
>>>>>>>   TLS_RSA_WITH_AES_128_CBC_SHA.
>>>>>> 
>>>>>> A BCP defining cipher suite recommendations should not have a higher
>>>>>> level of requirement for TLS_RSA_WITH_AES_128_CBC_SHA than it has for
>>>>>> TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, at least. I think it is OK to just
>>>>>> say that the TLS specification was wrong to mandate
>>>>>> TLS_RSA_WITH_AES_128_CBC_SHA, or don't mention it at all.
>>>>> 
>>>>> I don't know if RFC 5246 was *wrong*, but the situation on the ground has 
>>>>> changed since 2008.
>>>> 
>>>> I was wondering about the above as well. I think your document is updating 
>>>> MTI or at least narrowing down recommended choices, and CBC_SHA is not one 
>>>> of them. So deleting the two sentences quoted above is the best.
>>> 
>>> And in fact the text currently says:
>>> 
>>>  This document is not an application profile standard, in the sense of
>>>  Section 9 of [RFC5246].  As a result, clients and servers are still
>>>  REQUIRED to support the mandatory TLS cipher suite,
>>>  TLS_RSA_WITH_AES_128_CBC_SHA.
>>> 
>>> So I'd agree with Yaron here.
>> 
>> IMHO, a distinction without a difference. Anybody complying with your spec 
>> will need to implement a larger set of ciphers, so you are effectively 
>> extending the MTI list.
>> 
>> Which reminds me of something else: some application protocols specify 
>> explicit MTI TLS ciphers, which are different from the above. So now that I 
>> thought about that, I really dislike the paragraph you quoted above. So 
>> maybe change it to something more neutral:
>> 
>> This document doesn't change mandatory-to-implement TLS cipher suite(s) 
>> prescribed by TLS and application protocols using TLS.
>> 
>> But I would rather drop the whole paragraph, as it weakens the whole 
>> document.
> 
> I think we should be explicit about the cipher suite, even if we dislike it. 
> So how about:
> 
> This document doesn't change mandatory-to-implement TLS cipher suite(s) 
> prescribed by TLS and application protocols using TLS. To maximize 
> interoperability, RFC 5246 REQUIRES implementation of the 
> TLS_RSA_WITH_AES_128_CBC_SHA cipher suite, which is significantly weaker than 
> the cipher suites recommended here. Implementers should consider the 
> interoperability gain against the loss in security when deploying this cipher 
> suite. Other application protocols specify other cipher suites as mandatory 
> to implement (MTI).

This is much better, thank you!

_______________________________________________
Uta mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/uta

Reply via email to