thank you very much: it works very well with slapd(8) 2.3.27.
my issue now is that i will have to use the package supplied by RH
enteprise 4: openldap-servers-2.2.13-6.4E
and with this version i get this message:
unknown directive "idassert-bind" inside backend database definition
(ignored)
line 80 (idassert-authzfrom "dn.regex=.+")
slapd doesn't know idassert-authzfrom !
so, do you know if there is an other directive with this version that
enable me to do the same things (anonymous bind rewrite as an admin DN)