[Samba] Samba4 AD delegation to read userPassword attribute

[Christian Hailer]

Hello Samba group,

I ran into a problem concerning Dovecot LDAP authentication to the Samba4 Active Directory.

Background: I want to install a Openchange+Samba4 environment using Sogo, Dovecot and Postfix. I didn't want to use openldap as described in the Openchange documentation, why should I use 2 LDAP databases?

Fedora 17, latest updates applied
Samba: Version 4.1.0pre1-GIT-813bd03
dovecot-2.1.10-4.fc17.i686

At first I tried to use the auth_bind method of Dovecot, but very soon I realized (via tcpdump) that you first have to authenticate to Samba4:

...
searchResDone
resultCode: operationsError (1)
matchedDN:
Operation unavailable without authentication
...

I defined the  properties in dovecot-ldap.conf like this:

---------------------------------------------------
uris = ldaps://192.168.0.1:636
dn = cn=ldap,ou=USER,dc=example,dc=de
dnpass = somepassword

base = dc=example,dc=de
scope = subtree
deref = never

user_attrs = sAMAccountName=uid,primaryGroupID=gid
user_filter = (sAMAccountName=%u)

pass_attrs = mail=user,userPassword=password
pass_filter = (sAMAccountName=%u)
---------------------------------------------------

So trying to authenticate to Dovecot with a telnet connection

>telnet localhost 143              
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN] Dovecot ready.
1 login someuser somepassword

results in the error message "result: mail=someuser at example.de; userPassword missing"

A tcpdump shows the following searchRequest:

---------------------------------------------------
Lightweight Directory Access Protocol
  LDAPMessage searchRequest(2) "dc=example,dc=de" wholeSubtree
  ...
  Filter: (sAMAccountName=someuser)
    filter: equalityMatch (3)
     equalityMatch
       attributeDesc: sAMAccountName
       assertionValue: someuser
  attributes: 2 items
    AttributeDescription: mail
    AttributeDescription: userPassword
---------------------------------------------------

As a result I get:

---------------------------------------------------
Lightweight Directory Access Protocol
  LDAPMessage searchResEntry(2) "CN=someuser, OU=USER,DC=example,DC=de" [1 result]
  ...
  searchResEntry
    objectName: CN=someuser, OU=USER,DC=example,DC=de
    attributes: 1 item
      PartialAttributeList item mail
        type: mail
        vals: 1 item
          AttributeValue: someuser at exchange.de
---------------------------------------------------

So unfortunately the "userPassword" attribute is missing. Now, I remembered the "Control Delegation Wizard" from Microsoft AD where you have to delegate permission to read all user properties to a user account in order to be able to authenticate i.e. pam_ldap users on a linux server. 

I delegated the appropriate permissions to the "ldap" user used in dovecot-ldap.conf above, but the behaviour did not change, the "userPassword" attribute won't be delivered to the "ldap" user.

Is anybody out there who ran into the same problem?

Best regards, Christian