First, sorry for having placed this thread in private, that was unintentional (maybe I should reconsider using a "reply to all" by default). Group added. 2011/7/29 Howard Chu<hyc(a)symas.com>: > Erwann ABALEA wrote: [...] >> In fact, I know such a CA that was generated some months ago, with a >> very large audience, and whose certificates are to be stored in an >> LDAP structure. Czech Republic passport CA certificate. If you want to >> know how it's used, and by who, we can talk about it in private, or >> you can look at www.icao.int, search for Doc9303 documents, PKD >> structure, etc. (In fact, I didn't know of this limitation, and I'll >> look forward its impact in integrating the Czech certificates in the >> OpenLDAP structures we sell and deploy). >> I agree that UTF8String would have been a much better choice, but >> X.509 doesn't prevent the use of T61String. >> In the meantime, some products still don't support UTF8String in >> certificates, a Novell proxy product (I don't remember its exact name) >> is an example I encountered recently. > > If that's the case, what solutions do you propose? We could accept T61String > if it only uses characters that are present in 7-bit ASCII of course. But > once you venture into 8-bit and extended/accented characters all bets are > off. I'll need to grab this CA certificate back. I was asked to give my opinion on whether it was to be considered valid or not. Despite the fact that T61String is clearly deprecated in RFC5280/3280/2459, and that ICAO has chosen to base their certificate profile on RFC3280 (a bad choice), asking for a country to change its root CA cert signing all its passports because that doesn't follow rules I personally don't adhere to is difficult and counterproductive. I wasn't the only one to have this idea, and it was accepted. I'm 99% sure 7 bits didn't suffice. The remaining 1% will be fixed as soon as I find the certificate. Do you have any document or pointer to understand the task of converting to/from T.61, and incompatible character sets you talked about? I Googled for this, but I'm not sure of what I found (what I found reminds me of old character sets we used many years ago in France for the Minitel, with G1/G2 character groups, etc, not that far from VT consoles).

Howard Chu wrote: > Erwann ABALEA wrote: >> Do you have any document or pointer to understand the task of >> converting to/from T.61, and incompatible character sets you talked >> about? I Googled for this, but I'm not sure of what I found (what I >> found reminds me of old character sets we used many years ago in >> France for the Minitel, with G1/G2 character groups, etc, not that far >> from VT consoles). > > You can reference this old draft; I wrote Appendix A and B to document the > mapping as we understood it at that time. These Appendices were dropped > from > the final version because it was considered futile to attempt to document > the > T.61 character encoding rules. > > http://tools.ietf.org/html/draft-ietf-ldapbis-strprep-00#appendix-A > > You can also read libldap/t61.c; the code has been present in every > OpenLDAP > release since 2002 but is not compiled or used. > This Guide has a pretty good discussion of the issues. http://www.cs.auckland.ac.nz/~pgut001/pubs/x509guide.txt The section on "Character Sets" is particularly relevant. The section on "Comparing DNs" is somewhat relevant, though in fact OpenLDAP has already solved this problem (for all the string types besides T61String) by doing all matching in UTF-8.

Erwann ABALEA wrote:

> I'm reading now libldap/t61.c. I just read the IETF draft, and the > numerous tables... What a mess. X.680 has a reference to T.61 > recommendation, which was deleted some years ago, and I'm not clever > enough to make Google find a copy of the standard. It can't be bought > anymore from ITU, but it's still referenced by later standards. Nice. The 1988 edition is still downloadable. http://www.itu.int/rec/T-REC-T.61-198811-S/en

It also references T.51: http://www.itu.int/rec/T-REC-T.51/en Unfortunately the 1993 edition of T.61 is gone.

> Meanwhile, I still haven't found the Czech CSCA certificate, but I > know what to do with the remaining 1% uncertainty. The CN field is > encoded as T61String, to hold the "CSCA_CZ" value. That fits well > within the 7bits limit. Then you should just be using PrintableString. You're required to use the least-inclusive string type, after all.

> 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.

Erwann ABALEA wrote: > 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.