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

Julian Reschke <julian.reschke@gmx.de> Mon, 13 March 2017 08:14 UTC

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To: Carsten Bormann <cabo@tzi.org>
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From: Julian Reschke <julian.reschke@gmx.de>
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Date: Mon, 13 Mar 2017 09:14:16 +0100
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Cc: draft-ietf-jsonbis-rfc7159bis.all@ietf.org, John Cowan <cowan@ccil.org>, Ned Freed <ned.freed@mrochek.com>, IETF <ietf@ietf.org>, Peter Cordell <petejson@codalogic.com>, secdir@ietf.org, "json@ietf.org" <json@ietf.org>, Benjamin Kaduk <kaduk@mit.edu>
Subject: Re: [Json] secdir review of draft-ietf-jsonbis-rfc7159bis-03
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On 2017-03-12 16:31, Carsten Bormann wrote:
> On 12 Mar 2017, at 10:14, Julian Reschke <julian.reschke@gmx.de>; wrote:
>>
>> Does anybody recall why we removed <https://tools.ietf.org/html/rfc4627#section-3>;:
>
> I seem to remember that the advice simply is no longer working since JSON was extended from 4627 to 7159.  Instead of trying to come up with an updated algorithm, the WG recognized that this is not a real-world problem.
 > ...

So the changes in RFC 7159 allow top-level strings, so we can't rely on 
the first *two* characters being US-ASCII. But we *can* rely on the 
first one being US-ASCII, no?

So the following should still be correct:

>    Since the first character of a JSON text will always be an ASCII
>    character [RFC0020], it is possible to determine whether an octet
>    stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking
>    at the pattern of nulls in the first four octets.
>
>            00 00 00 xx  UTF-32BE
>            00 xx xx xx  UTF-16BE
>            xx 00 00 00  UTF-32LE
>            xx 00 xx xx  UTF-16LE
>            xx xx xx xx  UTF-8

Best regards, Julian