7.3. Managing Synchronization Agreements

7.3.1. Trusting the Active Directory and IPA CA Certificates

Both Active Directory and Identity Management use certificates for server authentication. For the Active Directory and IPA SSL server certificates to be trusted by each other, both servers need to trust the CA certificate for the CA which issued those certificates. This means that the Active Directory CA certificate needs to be imported into the IPA database, and the IPA CA certificate needs to be imported into the Active Directory database.

Export the Active Directory CA certificate.
1. In My Network Places, open the CA distribution point. For example, the location on Windows Server 2003 is C:\WINDOWS\system32\certsrv\CertEnroll\.
2. Double-click the security certificate file (.crt file) to display the Certificate dialog box.
3. On the Details tab, click Copy to File to start the Certificate Export Wizard.
4. Click Next, and then select Base-64 encoded X.509 (.CER).
5. Specify a suitable directory and file name for the exported file. Click Next to export the certificate, and then click Finish.
Copy the Active Directory certificate over to the IPA server machine.
Download the IPA server's CA certificate from http://ipa.example.com/ipa/config/ca.crt.
Copy both the Active Directory CA certificate and the IPA CA certificate into the /etc/openldap/cacerts/ directory.
Update the hash symlinks for the certificates.
```
cacertdir_rehash /etc/openldap/cacerts/
```
Edit the /etc/openldap/ldap.conf file, and add the information to point to and use the certificates in the /etc/openldap/cacerts/ directory.
```
TLS_CACERTDIR /etc/openldap/cacerts/
TLS_REQCERT allow
```

7.3.2. Creating Synchronization Agreements

Synchronization agreements are created on the IPA server using the ipa-replica-manage connect command because it creates a connection to the Active Directory domain. The options to create the synchronization agreement are listed in Table 7.3, “Synchronization Agreement Options”.

Make sure that the Active Directory and IPA servers trust each other's CA certificates, as in Section 7.3.1, “Trusting the Active Directory and IPA CA Certificates”.
Remove any existing Kerberos credentials on the IPA server.
```
$ kdestroy
```
Use the ipa-replica-manage command to create a Windows synchronization agreement. This requires the --winsync option. If passwords will be synchronized as well as user accounts, then also use the --passsync option and set a password to use for Password Sync.
The --binddn and--bindpwd options give the username and password of the system account on the Active Directory server that IPA will use to connect to the Active Directory server.
```
$ ipa-replica-manage connect --winsync 
	--binddn cn=administrator,cn=users,dc=example,dc=com 
	--bindpw Windows-secret 
	--passsync secretpwd 
	--cacert /etc/openldap/cacerts/windows.cer  
	adserver.example.com -v
```
When prompted, enter the Directory Manager password.
Optional. Configure Password Synchronization, as in Section 7.4.2, “Setting up Password Synchronization”.

Table 7.3. Synchronization Agreement Options

Option	Description
--winsync	Identifies this as a synchronization agreement.
--binddn	Gives the full user DN of the synchronization identity. This is the user DN that the IPA LDAP server uses to bind to Active Directory. This user must exist in the Active Directory domain and must have replicator, read, search, and write permissions on the Active Directory subtree.
--bindpw	Gives the password for the sync user.
--passsync	Gives the password for the Windows user account which is involved in synchronization.
--cacert	Gives the full path and file name of the Active Directory CA certificate. This certificate is exported in Section 7.3.1, “Trusting the Active Directory and IPA CA Certificates”.
--win-subtree	Gives the DN of the Windows subtree containing the users to synchronize. The default value is `cn=Users,$SUFFIX`.
AD_server_name	Gives the hostname of the Active Directory domain controller.

7.3.3. Changing the Behavior for Syncing User Account Attributes

When the sync agreement is created, it has certain default behaviors defined for how the synchronization process handled the user account attributes during synchronization. The types of behaviors are things like how to handle lockout attributes or how to handle different DN formats. This behavior can be changed by editing the synchronization agreement. The list of attribute-related parameters are in Table 7.4, “Synced Attribute Settings”.

The sync agreement exists as a special plug-in entry in the LDAP server and each attribute behavior is set through an LDAP attribute. To change the sync behavior, use the ldapmodify command to modify the LDAP server entry directly.

For example, account lockout attributes are synchronized between IPA and Active Directory by default, but this can be disabled by editing the ipaWinSyncAcctDisable attribute. (Changing this means that if an account is disabled in Active Directory, it is still active in IPA and vice versa.)

$ ldapmodify -x -D "cn=directory manager" -w password

dn: cn=ipa-winsync,cn=plugins,cn=config
changetype: modify
replace: ipaWinSyncAcctDisable
ipaWinSyncAcctDisable: none

modifying entry "cn=ipa-winsync,cn=plugins,cn=config"

Table 7.4. Synced Attribute Settings

Parameter	Description	Possible Values
General User Account Parameters
ipaWinSyncNewEntryFilter	Sets the search filter to use to find the entry which contains the list of object classes to add to new user entries.	The default is `(cn=ipaConfig)`.
ipaWinSyncNewUserOCAttr	Sets the attribute in the configuration entry which actually contains the list of object classes to add to new user entries.	The default is `ipauserobjectclasses`.
ipaWinSyncHomeDirAttr	Identifies which attribute in the entry contains the default location of the POSIX home directory.	The default is `ipaHomesRootDir`.
ipaWinSyncUserAttr	Sets an additional attribute with a specific value to add to Active Directory users when they are synced over from the Active Directory domain. If the attribute is multi-valued, then it can be set multiple times, and the sync process adds all of the values to the entry. NOTE This only sets the attribute value if the entry does not already have that attribute present. If the attribute is present, then the entry's value is used when the Active Directory entry is synced over.	ipaWinSyncUserAttr: attributeName attributeValue
ipaWinSyncUserFlatten	Sets whether to normalize the DN of Active Directory entries to conform with the IPA directory structure. In IPA, all users are stored under the `cn=users,cn=accounts,$SUFFIX` entry, but Active Directory can have more branches in its directory, which can result in DNs like `cn=John Smith,ou=Development,ou=Engineering,cn=users,dc=example,dc=com`. Flattening the DN discards any additional intervening organizational units in the Active Directory DN and creating a simple DN on the IPA side. Any `ou` attributes are stored in the IPA user entry.	true \| false
ipaWinSyncForceSync	Sets whether to check existing IPA users which match an existing Active Directory user should be automatically edited so they can be synchronized. If an IPA user account has a `uid` parameter which is identical to the `samAccountName` in an existing Active Directory user, then that account is not synced by default. This attribute tells the sync service to add the `ntUser` and `ntUserDomainId` to the IPA user entries automatically, which allows them to be synchronized.	true \| false
User Account Lock Parameters
ipaWinSyncAcctDisable	Sets which way to synchronize account lockout attributes. It is possible to control which account lockout settings are in effect. For example, `to_ad` means that when account lockout attribute is set in IPA, its value is synced over to Active Directory and overrides the local Active Directory value. By default, account lockout attributes are synced from both domains.	both (default) to_ad to_ds none
ipaWinSyncInactivatedFilter	Sets the search filter to use to find the DN of the group used to hold inactivated (disabled) users. This does not need to be changed in most deployments.	The default is `(&(cn=inactivated)(objectclass=groupOfNames))`.
ipaWinSyncActivatedFilter	Sets the search filter to use to find the DN of the group used to hold activate users. This does not need to be changed in most deployments.	The default is `(&(cn=activated)(objectclass=groupOfNames))`.
Group Parameters
ipaWinSyncDefaultGroupAttr	Sets the attribute in the new user account to reference to see what the default group for the user is. The group name in the entry is then used to find the `gidNumber` for the user account.	The default is `ipaDefaultPrimaryGroup`.
ipaWinSyncDefaultGroupFilter	Sets the search filter to map the group name to the POSIX `gidNumber`.	The default is `(&(gidNumber=)(objectclass=posixGroup)(cn=`groupAttr_value*`))`.
Realm Parameters
ipaWinSyncRealmAttr	Sets the attribute which contains the realm name in the realm entry.	The default is `cn`.
ipaWinSyncRealmFilter	Sets the search filter to use to find the entry which contains the IPA realm name.	The default is `(objectclass=krbRealmContainer)`.

7.3.4. Changing the Synchronized Windows Subtree

Creating a synchronization agreement automatically sets the two subtrees to use as the synchronized user database. In IPA, the default is cn=users,cn=accounts,$SUFFIX, and for Active Directory, the default is CN=Users,$SUFFIX.

The value for the Active Directory subtree can be set to a non-default value when the sync agreement is created by using the --win-subtree option. After the agreement is created, the Active Directory subtree can be changed by using the ldapmodify command to edit the nsds7WindowsReplicaSubtree value in the sync agreement entry.

For example:

$ ldapmodify -x -D "cn=directory manager" -w password

dn: cn=ipa-winsync,cn=plugins,cn=config
changetype: modify
replace: nsds7WindowsReplicaSubtree
nsds7WindowsReplicaSubtree: CN=People,DC=example,DC=com

modifying entry "cn=ipa-winsync,cn=plugins,cn=config"

7.3.5. Deleting Synchronization Agreements

Synchronization can be stopped by deleting the sync agreement which disconnects the IPA and Active Directory servers. In the inverse of creating a sync agreement, deleting a sync agreement uses the ipa-replica-manage disconnect command and then the hostname of the Active Directory server.

Delete the sync agreement.

# ipa-replica-manage disconnect adserver.example.com

Remove the Active Directory CA certificate from the IPA server database:
```
# certutil -D -d /etc/dirsrv/slapd-EXAMPLE.COM/ -n "Imported CA"
```

7.3.6. Winsync Agreement Failures

Creating the sync agreement fails because it cannot connect to the Active Directory server.

One of the most common sync agreement failures is that the IPA server cannot connect to the Active Directory server:

"Update failed! Status: [81  - LDAP error: Can't contact LDAP server]

This can occur if the wrong Active Directory CA certificate was specified when the agreement was created. This creates duplicate certificates in the IPA LDAP database (in the /etc/dirsrv/slapd-DOMAIN/ directory) with the name Imported CA. This can be checked using certutil:

$ certutil -L -d /etc/dirsrv/slapd-DOMAIN/

Certificate Nickname                                         Trust Attributes
SSL,S/MIME,JAR/XPI

CA certificate                                               CTu,u,Cu
Imported CA                                                  CT,,C
Server-Cert                                                  u,u,u
Imported CA                                                  CT,,C

To resolve this issue, clear the certificate database:

# certutil -d /etc/dirsrv/slapd-DOMAIN-NAME -D -n "Imported CA"

This deletes the CA certificate from the LDAP database.

There are errors saying passwords aren't being synced because it says the entry exists

For some entries in the user database, there may be an informational error message that the password is not being reset because the entry already exists:

"Windows PassSync entry exists, not resetting password"

This is not an error. This message occurs when an exempt user, the Password Sync user, it not being changed. The Password Sync user is the operational user which is used by the service to change the passwords in IPA.