« OpenLDAP password policy » is an overlay that allows you to set up an efficient management of the authentication accounts of people referenced in the OpenLDAP directory. This management concerns in particular the passwords of these persons. This article will show how to configure the OpenLDAP server to activate the« password policy » overlay and implement this management. Prerequisite: The article Adding data to the directory and its prerequisites are read. The OpenLDAP server is installed and the data of the article are entered.

1. Enable ppolicy schema (OpenLDAP password policy)

By default, the ppolicy schema is installed: /etc/ldap/schema/ppolicy.ldif, but not enabled. To enable it:

ldapmodify -x -a -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -f /etc/ldap/schema/ppolicy.ldif

To check the schema loading :

ldapsearch -x -s one -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -b cn=schema,cn=config cn -LLL

dn: cn={0}core,cn=schema,cn=config
cn: {0}core

dn: cn={1}cosine,cn=schema,cn=config
cn: {1}cosine

dn: cn={2}nis,cn=schema,cn=config
cn: {2}nis

dn: cn={3}inetorgperson,cn=schema,cn=config
cn: {3}inetorgperson

dn: cn={4}ppolicy,cn=schema,cn=config
cn: {4}ppolicy

Notice the presence of the ppolicy schema in addition to the four schemas that are enabled by default.

2. Enable the ppolicy overlay

Create the LDIF command file: ppolicy-module.ldif

vi ppolicy-module.ldif

Enter in the editor and save:

dn: cn=module{0},cn=config
changeType: modify
add: olcModuleLoad
olcModuleLoad: ppolicy

Execute the modify command contained in the file:

ldapmodify -x -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -f ppolicy-module.ldif

To check the module activation:

ldapsearch -x -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -b cn=config "(objectClass=olcModuleList)" olcModuleLoad -LLL

dn: cn=module{0},cn=config
olcModuleLoad: {0}back_mdb
olcModuleLoad: {1}ppolicy

Notice the presence of the ppolicy module in the list, while default only back_mdb (database management module) is enabled.

3. Configuring the ppolicy overlay

Create the LDIF command file: ppolicy-conf.ldif

vi ppolicy-conf.ldif

Enter in the editor and save:

dn: olcOverlay=ppolicy,olcDatabase={1}hdb,cn=config
objectClass: olcPpolicyConfig
olcOverlay: ppolicy
olcPPolicyDefault: cn=ppolicy,dc=ldaptuto,dc=net
olcPPolicyUseLockout: FALSE
olcPPolicyHashCleartext: TRUE

Add the entry contained in the file:

ldapmodify -x -a -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -f ppolicy-conf.ldif

To verify that the configuration is actually enabled:

ldapsearch -x -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -b cn=config "(objectClass=olcPpolicyConfig)" -LLL

dn: olcOverlay={0}ppolicy,olcDatabase={1}hdb,cn=config
objectClass: olcPPolicyConfig
olcOverlay: {0}ppolicy
olcPPolicyDefault: cn=ppolicy,dc=ldaptuto,dc=net
olcPPolicyHashCleartext: TRUE
olcPPolicyUseLockout: FALSE

Three configuration settings:

1. olcPPolicyDefault: Specifies a configuration DN used by default (see next paragraph).
2. olcPPolicyHashCleartext: Indicates whether passwords should be encrypted systematically. Advise: This setting should be TRUE.
3. olcPPolicyUseLockout: Indicates whether the error message returned when attempting to connect to a locked account is a message specific to that locked state (TRUE), or a general failed login message (FALSE). FALSE is more secure (no indication to a possible pirate), TRUE is more convenient.

4. Configure a password policy

We will configure the entry specified in the olcPPolicyDefault parameter of the ppolicy overlay configuration, i.e. cn=ppolicy,dc=ldaptuto,dc=net. To do this we will create an LDIF file that will allow to add this entry.

vi ppolicy-defaut.ldif

Enter in the editor and save:

dn: cn=ppolicy,dc=ldaptuto,dc=net
objectClass: device
objectClass: pwdPolicyChecker
objectClass: pwdPolicy
cn: ppolicy
pwdAllowUserChange: TRUE
pwdAttribute: userPassword
pwdCheckQuality: 1
pwdExpireWarning: 600
pwdFailureCountInterval: 30
pwdGraceAuthNLimit: 5
pwdInHistory: 5
pwdLockout: TRUE
pwdLockoutDuration: 0
pwdMaxAge: 0
pwdMaxFailure: 5
pwdMinAge: 0
pwdMinLength: 5
pwdMustChange: FALSE
pwdSafeModify: FALSE

Add the entry contained in the file:

ldapmodify -x -a -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -f ppolicy-defaut.ldif

To verify the result:

ldapsearch -x -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -b dc=ldaptuto,dc=net "(objectClass=pwdPolicy)" -LLL

16 Settings (all listed attributes) allow you to set up an efficient and effective policy for passwords and user account management. The following command gives you full details about these parameters:

man slapo-ppolicy

For example, pwdMinLength has been set to 5, which means that a password can not be less than 5 characters in length. Let’s test:

ldappasswd -x -H ldap://localhost -D uid=durand,ou=people,dc=ldaptuto,dc=net -w durand -s dura

Result: Constraint violation (19)
Additional info: Password fails quality checking policy

This command allows Alain Durand to log in with his username and password (-D uid=durand,ou=people,dc=ldaptuto,dc=net and -w durand) and change this password with the new value provided (-s dura). The command fails because the new password has only 4 characters.

ldappasswd -x -H ldap://localhost -D uid=durand,ou=people,dc=ldaptuto,dc=net -w durand -s duran

The command succeeds because the new password has 5 characters. To verify the password modification:

ldapsearch -x -H ldap://localhost -D uid=durand,ou=people,dc=ldaptuto,dc=net -w durand -b dc=ldaptuto,dc=net

ldap_bind: Invalid credentials (49)

The old password is not accepted and the same command with the new password: duran, should succeed. Another setting: pwdCheckModule controls the quality of the contents of passwords. This setting specifies the file name of a native shared library that ensures this function. Before informing it, it will first be necessary to ensure that this library is present. pqChecker is a library that can be used to control passwords content strength for ppolicy overlay. To use it, you should modify the default password policy setting.

vi modifpp.ldif

Enter in the editor and save:

dn: cn=ppolicy,dc=ldaptuto,dc=net
changeType: modify
add: pwdCheckModule
pwdCheckModule: pqchecker.so

Execute the modify command contained in the file:

ldapmodify -x -a -H ldap://localhost -D cn=admin,dc=ldaptuto,dc=net -w admin -f modifpp.ldif

pqchecker.so is the quality control library for the contents of passwords. By default it is installed at /usr/lib/ldap. It requires by default a password with at least 1 uppercase, 1 lowercase, 1 digit and 1 special character (not alphabetic). Further details about it may be read on http://www.meddeb.net/pqchecker]]>