Re: [Json] secdir review of draft-ietf-jsonbis-rfc7159bis-03

Julian Reschke <julian.reschke@gmx.de> Thu, 16 March 2017 11:35 UTC

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To: Peter Cordell <petejson@codalogic.com>, John Cowan <cowan@ccil.org>, Carsten Bormann <cabo@tzi.org>
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Cc: draft-ietf-jsonbis-rfc7159bis.all@ietf.org, secdir@ietf.org, "json@ietf.org" <json@ietf.org>
From: Julian Reschke <julian.reschke@gmx.de>
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Date: Thu, 16 Mar 2017 12:35:39 +0100
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Subject: Re: [Json] secdir review of draft-ietf-jsonbis-rfc7159bis-03
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On 2017-03-16 12:23, Peter Cordell wrote:
> On 16/03/2017 10:49, Julian Reschke wrote:
>> On 2017-03-16 11:28, Peter Cordell wrote:
>>>
>>> 8.1.  Character Encoding
>>>
>>>    JSON text SHOULD be encoded in UTF-8 [UNICODE] (Section 3).  JSON
>>>    texts that are encoded in UTF-8 are interoperable in the sense that
>>>    they will be read successfully by the maximum number of
>>>    implementations.
>>>
>>>    There are many implementations that cannot successfully read texts
>>>    in other encodings.  JSON text MAY be encoded in other encodings if
>>>    the generator is sure that the intended parsers can read them.
>>>
>>>    Implementations MUST NOT add a byte order mark to the beginning of a
>>>    JSON text.  In the interests of interoperability, implementations
>>>    that parse JSON texts MAY ignore the presence of a byte order mark
>>>    rather than treating it as an error.
>>>
>>> Are "generator" and "parser" the correct terms to use in this instance,
>>> or does that functionality sit above the character encoding layer?
>>> ...
>>
>> Not convinced.
>>
>> a) It's not constrained to UTF-8/16/32, so people might decide to
>> support ISO-8859-1, or UTF-7-
>
> Why is that a problem if the generator knows the parser can read it?  If
> someone wants to use EBCDIC for whatever reason, are they not allowed to
> call it JSON?

For application/json, it would violate a SHOULD-level requirement... 
<https://greenbytes.de/tech/webdav/rfc7159.html#rfc.section.8.1.p.1>;:

"JSON text SHALL be encoded in UTF-8, UTF-16, or UTF-32. The default 
encoding is UTF-8, and JSON texts that are encoded in UTF-8 are 
interoperable in the sense that they will be read successfully by the 
maximum number of implementations; there are many implementations that 
cannot successfully read texts in other encodings (such as UTF-16 and 
UTF-32)."

So I agree it's technically allowed.

>> b) It doesn't state that the only way to support encodings other than
>> UTF-8 is to inspect the leading octets for zeros (or their lack of).
>
> UTF detection is one way.  It's not the only way.  If you want to go the
> UTF detection way or some other way, rfc7159bis shouldn't prevent it,
> but it doesn't have to tell you how to do it.

Oh, it's not the only way?

How do we interoperate then?

Best regards, Julian