Re: [ldapext] Case sensitivity summary

Michael Ströder <michael@stroeder.com> Fri, 04 December 2015 14:00 UTC

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To: Andrew Findlay <andrew.findlay@skills-1st.co.uk>, LDAP Extensions list <ldapext@ietf.org>
References: <20151204123810.GA8983@slab.skills-1st.co.uk>
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Subject: Re: [ldapext] Case sensitivity summary
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Andrew Findlay wrote:
> We are not going to define a standard that forces everyone to do everything
> 'right' while providing interworking of differing systems. It is simply
> not possible.

That perfectly summarizes this topic.
Thanks Andrew, for this clear statement.

Let's keep the scope right.

> Overall I think we are heading for something like this:
> 
> 1)	Usernames and groupnames should have caseIgnoreMatch syntax
> 
> 2)	Usernames and groupnames should preferably be stored in lower-case in
> 	cultures where that has meaning. Remember that LDAP is case-preserving
> 	even for case-insensitive attributes.
> 
> 3)	Systems that are internally case-sensitive should take extra care
> 	when using data from LDAP.
> 
> I know this conflicts with Mark's wish to be able to import existing
> NIS data unchanged to cope with weird existing situations, but I see that 
> as a special case that may be better handled in another way.

+1 !!!

(That's pretty much exactly what I planned to suggest.)

> Note that the above discussion *only* applies to usernames and groupnames.
> Unix-specific mappings such as automount maps are a different issue.

automount maps are maybe a similar topic like generating 'homeDirectory' values
for $HOME on case-sensitive file-systems based on user names.  For this
RECOMMENDing that usernames are normalized to lower-case is really helpful.

Regarding service names:

(Personally I never saw any customer LDAP deployment storing a services map.)

1. Service names are used in DNS RRs (SRV, DANE, etc.) and those DNS labels are
definitely supposed to be treated case-insensitive.

2. Jordan pointed out RFC 6335.

=> I concur with Jordan: Service names MUST be treated case-insensitive.
Probably recommending in an implementation note to normalize values to
lower-case seems also to be a good idea.

=> People actually using case-sensitive service names to address *different*
services MUST clean up their local mess. But they likely have to do that anyway.

Ciao, Michael.