Subject: Re: ldap for aliases

From: Per Hedeland <[email-masked]>
Date: Thu, 20 Aug 1998 15:23:22 +0200 (MET DST)

Curt Hillegas <[email-masked]> wrote:
>We're moving all of our University directory services to LDAP.  We need
>to be able to do directory lookups for a user that could return multiple
>delivery addresses for that user (we're currently doing this with NIS). 
>The most obvious place to do this would be by having the AliasFile query
>our LDAP database, but ldapx does not have the MCF_ALIASOK flag turned
>on.  Is there another way to achieve our goal, or is there a reason not
>to turn on the MCF_ALIASOK for ldapx?  Are there plans to enable LDAP
>for alias lookups in the near future?

I'm Cc'ing Booker Bense on this, as he is the real expert on the LDAP
code in sendmail (having written it:-) - hopefully he'll correct me if
I'm wrong...

First, regarding returning multiple addresses:

- The current (sendmail 8.9.1) code will do this if the attribute asked
for has a single value including all the addresses, comma-separated - as
if specified in the aliases file.

- The current code will *not* do this in the case where the found
attribute is multi-valued - rather it will just pick the first value
returned. Booker Bense has submitted a patch to turn the multiple values
into a comma-separated list in this case - I can't say when (or even if)
this will be included in the standard release, but it may not be until
8.10.

- Neither the current code nor Booker's patch will do this in the case
where multiple entries are found - again just the first entry found will
be used. Quoting Booker:-): "The changes needed to do this are pretty
simple".

Second, regarding MCF_ALIASOK:

The above issues with multiple values is the "official" reason it isn't
set for ldapx - I'm not sure it's a very good reason, as nothing "bad"
will happen if you run into these situations - just that the semantics
may not be what is expected, and as long as it is documented... I.e. if
you want to, you should be able to go ahead and set MCF_ALIASOK in your
copy of the code - however it is of limited benefit anyway:

Setting it allows you to have an ldapx spec in the AliasFile option,
which would look something like (assuming this is the only map there):

O Aliasfile=ldapx:-h"ldap.stanford.edu"
		-k"mailacceptinggeneralid=%s" -v maildrop

which doesn't look very nice:-), and what is worse if you need to use -b
with embedded commas, as in

O Aliasfile=ldapx:-b"ou=People, o=Stanford University, c=US"
		-h"ldap.stanford.edu" -k"mailacceptinggeneralid=%s" -v maildrop

the spec will be misparsed, as the commas are taken as alias map
separators - it should be possible to fix this, but it requires careful
consideration to make sure such a change in the parsing doesn't break
something else. AND... - finally some good news:-) - you can avoid these
problems with one level of indirection, using a 'sequence' map with a
single member:

Kldapaliases ldapx -b"ou=People, o=Stanford University, c=US"
		-h"ldap.stanford.edu" -k"mailacceptinggeneralid=%s" -v maildrop

O Aliasfile=sequence:ldapaliases

works just fine, even without having MCF_ALIASOK set for ldapx (the
latter might actually be a bug:-).

--Per Hedeland