Re: [TLS] Accepting that other SNI name types will never work.

"Fossati, Thomas (Nokia - GB)" <thomas.fossati@nokia.com> Fri, 04 March 2016 07:19 UTC

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From: "Fossati, Thomas (Nokia - GB)" <thomas.fossati@nokia.com>
To: Adam Langley <agl@imperialviolet.org>, "tls@ietf.org" <tls@ietf.org>
Thread-Topic: [TLS] Accepting that other SNI name types will never work.
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Date: Fri, 4 Mar 2016 07:10:06 +0000
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Subject: Re: [TLS] Accepting that other SNI name types will never work.
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Trying again...

> Hi Adam,


In CoRE we might need to allocate a new SNI NameType for non-DNS host
names [1].

Removing SNI extensibility would make it unfeasible.

Cheers, t

[1] 
https://tools.ietf.org/html/draft-fossati-core-certmode-rd-names-00#section
-3.3


>On 03/03/2016 18:49, "TLS on behalf of Adam Langley" <tls-bounces@ietf.org
>on behalf of agl@imperialviolet.org> wrote:
>>The Server Name Indication (SNI) extension in TLS has a provision to
>>provide names other than host names[1]. None have even been defined to
>>my knowledge, but it's there.
>>
>>OpenSSL (and possibly others) have had a long-standing bug[2] (fixed
>>in master) that means that different types of names will cause an
>>error. To be clear: I live in a glass house and am not throwing
>>stones; these things happen. However, it means that a huge fraction of
>>the TLS deployment will not be able to accept a different name type
>>should one ever be defined. (This issue might have been caused by the
>>fact that the original[3] spec didn't define the extension in such a
>>way that unknown name types could be skipped over.)
>>
>>Therefore we (i.e. BoringSSL, and thus Google) are proposing to give
>>up on this and implement our parser such that the SNI extension is
>>only allowed to contain a single host name value. (This is compatible
>>with all known clients.) We're assuming that since this is already the
>>de-facto reality that there will be little objection. I'm sending this
>>mostly to record the fact so that, if someone tries to define a new
>>name type in the future, they won't waste their time.
>>
>>If the community wishes to indicate a different type of name in the
>>future, a new extension can be defined. This is already effectively
>>the case because we wouldn't fight this level of incompatibility when
>>there's any other option.
>>
>>(I think the lesson here is that protocols should have a single joint,
>>and that it should be kept well oiled. For TLS, that means that
>>extensions should have minimal extensionality in themselves and that
>>we should generally rely on the main extensions mechanism for these
>>sorts of things.)
>>
>>[1] https://tools.ietf.org/html/rfc6066#section-3
>>[2] 
>>https://github.com/openssl/openssl/blob/OpenSSL_1_0_1-stable/ssl/t1_lib.c
>>#
>>L1066
>>­ note that the data pointer is not updated.
>>[3] https://tools.ietf.org/html/rfc4366#section-3.1
>>
>>
>>Cheers
>>
>>AGL
>>
>>-- 
>>Adam Langley agl@imperialviolet.org https://www.imperialviolet.org
>>
>>_______________________________________________
>>TLS mailing list
>>TLS@ietf.org
>>https://www.ietf.org/mailman/listinfo/tls
>
>