I'm kinda having the same issue.

I want to use the LDAP database to store the secrets.

I've the SASL regular expression in slapd.conf

slapd.conf:
PHP Code:
...

authz-regexp
   uid
=([^,]*),cn=digest-md5,cn=auth
   ldap
:///ou=mgnt,dc=tao,dc=intranet??one?(uid=$1)

... 
When I execute:

PHP Code:
[root@tao-dev-auth02 sasl2]# ldapsearch -Y DIGEST-MD5 -U admin@tao-dev-auth02 -b "" 'uid=admin'     SASL/DIGEST-MD5 authentication started
Please enter your password:
ldap_sasl_interactive_bind_sInvalid credentials (49)
        
additional infoSASL(-13): user not foundno secret in database 
Now I even added 2 user's to sasl's own db, still the same error.

Also I don't understand how SASL's determines to use LDAP's db or it's own, or wherever it should be set.

It's a very very old post, so I guess you have thinks working by now hope you/someone could help me out.