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Re: Kerberos double binding creates no bindings (ITS#433)

On Thu, 27 Jan 2000, Mark Adamson wrote:

> Hello all.
>   I am working on getting OpenLDAP 2.0 working for the CMU campus
> here. I CVS downloaded the source in early December and have it
> compiled and running on my desktop machine.
>   I am working on getting Kerberos authentication working, and ran
> into what I'd have to call a bug. It has to do with a client such as
> ldapsearch uses ldap_kerberos_bind_s() and how the server binds your
> DN using do_bind().
>   When a client uses ldap_kerberos_bind_s() it first binds with an
> authmethod LDAP_AUTH_KRBV41 (the "ldapserver" ticket), and then again
> with LDAP_AUTH_KRBV42 (the "x500dsa" ticket). On the server, in the
> function 
> 	servers/slapd/back-ldbm/bind.c
> 	ldbm_back_bind()
> the first bind does all of the leg work of checking the krbName and
> returns 0 to the calling function
> 	servers/slapd/bind.c
> 	do_bind()
> The second bind on the server simply sends a SUCCESS message back to
> the client and returns a non-zero code back to do_bind(), with the
> comment "stop front end from sending result". 
>   When do_bind() was called, it first cleared any previous bindings and
> then if the backend bind returns 0 it will store the requested DN in
> the connection.
>   The bug is that the second (LDAP_AUTH_KRBV42) binding in
> ldbm_back_bind() always returns a non-zero code to do_bind(), so the
> DN binding from the first binding was erased and not stored the second 
> time. The result is a connection that has NO binding: you are
> unauthenticated. 
>   I am curious as to why the second binding wants to send the SUCCESS
> message itself and return !0, instead of returning 0 and letting
> do_bind() return SUCCESS (and set the DN binding).

- The whole double-bind thing is a hack from the Umich code when 
ldap was more integrated into the whole X500 environment. If you 
are running slapd, there is really no point to doing anything 
besides LDAP_AUTH_KRBV41. It's my understanding that the original
idea was to authenticate to both the ldap server and the X500 
DSA. I have no idea why this was done, but since X500 DSA's have
gone the way of the dodo, there is really no point in doing it

- Booker C. Bense