[Date Prev][Date Next] [Chronological] [Thread] [Top]

Re: invalid syntax when teletexstring

Erwann ABALEA wrote:
2011/7/29 Howard Chu<hyc@symas.com>:
Then you should just be using PrintableString. You're required to use the
least-inclusive string type, after all.

Howard, you're very good. But you too can make mistakes :)
1. PrintableString is inadequate (because of the underscore character).

Ah, right.

If everything is internally converted to UTF8 and t61.c seems to
provide a lossless T.61 to UTF8 conversion, why isn't it used?

Because it's incomplete. It only handles the original 333 character
repertoire of T.61, it doesn't handle shift-in/shift-out to other character
sets. I believe in the last version of T.61 there was support for Japanese
(JIS), Chinese, and Greek. So quite a lot more logic and tables needs to be
added, and it looks like a lot of work for something nobody should actually
be using.

If the support for JIS, Chinese, and Greek characters were to be
included in the 1993 edition, and this edition has never been
published, couldn't it be possible to ignore them?
X.680 (1997 edition) also references the 1988 edition of T.61, and if
no newer edition is present, then it still must be used, right?

Actually Japanese and Chinese are already specified in the 1988 edition. Greek is mentioned there but is lacking a specification of which escape code to use. Probably it's defined elsewhere, like a later version of ISO 2022 or somesuch.

Is an incomplete (but documented) support for T61String really worse
than no support for it at all? Even if literature tells that no
perfect support can exist?

In the security arena, yes. E.g. if we accept a T61String that uses escape codes, we will not normalize it correctly to UTF-8. From there we would be giving "definitive" yes/no results to matches, based on invalid comparisons.

  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/