Re: ldap.conf clarification

[Philip Guenther <guenther+ldaptech@sendmail.com>]

On Fri, 15 Mar 2013, Mik J wrote:
> Sorry if my question seem to be simple but I've read the ldap.conf 
> manpage and I would like to clarify what I understood
> 
> ldap.conf is the configuration file read by the ldap client.
> 
> TLS_REQCERT never
> means that the client doesn't ask the server for a certificate. 
> Therefore the server will not sent its certificate. Even for LDAPS (LDAP 
> over SSL)

The text of the manpage is misleading: in TLS/SSL, the client does not 
'request' a server certificate.  Whether the server sends its certificate 
is not under the client control, but rather is a property of the 
cipher-suite that was selected.  For example, with AES256-SHA the server 
cert is always sent.  (And no, TLS_REQCERT has no effect on the 
cipher-suite selection.)

So, setting it to "never" just tells the client to do no checking of the 
server certificate, if any, that is received.

(Note also: at least when using OpenSSL, the 'try' setting behaves exactly 
the same as 'demand' and 'hard'.)


...
> I have a few questions though
> 1) The statements TLS_CACERT and TLS_CACERTDIR seem to be a bit 
>    redundant. Why use the TLS_CACERT statement, we can have multiple CA 
>    cert right ?

Sometimes it's easier to administer a single file of multiple certs 
instead of a directory of hashed certificate names.


(On the server side, the certs in the olcTLSCACertificateFile file are 
also used to generate the optional list of CA subjects included in the 
client cert request, though many (most?) client ignore that list.)


> 2) I read that some people tell to have both "TLS_REQCERT never" and 
> "TLS_CACERTDIR" or "TLS_CACERT". Why would you specify a CA cert if our 
> client doesn't request and certificate from the LDAP server ?

It's probably pointless.  I suppose it's possible to use "TLS_REQCERT 
never" but also use client certs, in which case the client might need to 
send certs for intermediate CA...but that would be a bizarre use-case.


> 3) I will use "TLS_CACERT" and "TLS_KEY" on my client, if I want my 
>    client to be authenticated by the LDAP server

If you want to use TLS/SSL client certificate authentication, yes.  That 
doesn't directly affect the identity it binds as, of course.


> 4) All these statements are also valid for LDAP over SSL. Correct ?

Yes.


Philip Guenther