Chapter 4. Additional configuration for identity and authentication providers

Procedure

1. Open the /etc/sssd/sssd.conf file.

2. Use the re_expression option to define a custom regular expression.

   Example 4.1. Defining regular expressions globally

   To define the regular expressions globally for all domains, add re_expression to the [sssd] section of the sssd.conf file.

   You can use the following global expression to define the username in the format of domain\\username or domain@username:

   [sssd]
   [... file truncated ...]
   re_expression = (?P<domain>[^\\]*?)\\?(?P<name>[^\\]+$)

   Example 4.2. Defining regular expressions a particular domain

   To define the regular expressions individually for a particular domain, add re_expression to the corresponding domain section of the sssd.conf file.

   You can use the following global expression to define the username in the format of domain\\username or domain@username for the LDAP domain:

   [domain/LDAP]
   [... file truncated ...]
   re_expression = (?P<domain>[^\\]*?)\\?(?P<name>[^\\]+$)

Procedure

1. As root, open the /etc/sssd/sssd.conf file.

2. To define the expansion globally for all domains, add full_name_format to the [sssd] section of sssd.conf.

   [sssd]
   [... file truncated ...]
   full_name_format = %1$s@%2$s

   In this case the user name is displayed as user@domain.test.

3. To define the user name printing format for a particular domain, add full_name_format to the corresponding domain section of sssd.conf.

   • To configure the expansion for the Active Directory (AD) domain using %2$s\%1$s:

     [domain/ad.domain]
     [... file truncated ...]
     full_name_format = %2$s\%1$s

     In this case the user name is displayed as ad.domain\user.

   • To configure the expansion for the Active Directory (AD) domain using %3$s\%1$s:

     [domain/ad.domain]
     [... file truncated ...]
     full_name_format = %3$s\%1$s

     In this case the user name is displayed as AD\user if the flat domain name of the Active Directory domain is set to AD.

Procedure

1. Open the /etc/sssd/sssd.conf file.

2. In a domain section, add the cache_credentials = true setting:

   [domain/your-domain-name]
   cache_credentials = true

3. Optional, but recommended: Configure a time limit for how long SSSD allows offline authentication if the identity provider is unavailable:

   1. Configure the PAM service to work with SSSD.

      See Configuring user authentication using authselect for more details.

   2. Use the offline_credentials_expiration option to specify the time limit.

      Note that the limit is set in days.

      For example, to specify that users are able to authenticate offline for 3 days since the last successful login, use:

      [pam]
      offline_credentials_expiration = 3

Procedure

1. Open the /etc/sssd/sssd.conf file.

2. Set the primary server value to _srv_.

   For an LDAP provider, the primary server is set using the ldap_uri option:

   [domain/your-domain-name]
   id_provider = ldap
   ldap_uri = _srv_

3. Enable service discovery in the password change provider by setting a service type:

   [domain/your-domain-name]
   id_provider = ldap
   ldap_uri = _srv_
   
   chpass_provider = ldap
   ldap_chpass_dns_service_name = ldap

4. Optional: By default, the service discovery uses the domain portion of the system host name as the domain name. To use a different DNS domain, specify the domain name by using the dns_discovery_domain option.
5. Optional: By default, the service discovery scans for the LDAP service type. To use a different service type, specify the type by using the ldap_dns_service_name option.
6. Optional: By default, SSSD attempts to look up an IPv4 address. If the attempt fails, SSSD attempts to look up an IPv6 address. To customize this behavior, use the lookup_family_order option.

7. For every service with which you want to use service discovery, add a DNS record to the DNS server:

   _service._protocol._domain TTL priority weight port host_name

Procedure

1. Open the /etc/sssd/sssd.conf file.

2. Set the access_provider option to simple:

   [domain/your-domain-name]
   access_provider = simple

3. Define the access control rules for users.

   1. To allow access to users, use the simple_allow_users option.

   2. To deny access to users, use the simple_deny_users option.

      Important

      If you deny access to specific users, you automatically allow access to everyone else. Allowing access to specific users is considered safer than denying.

4. Define the access control rules for groups. Choose one of the following:

   1. To allow access to groups, use the simple_allow_groups option.

   2. To deny access to groups, use the simple_deny_groups option.

      Important

      If you deny access to specific groups, you automatically allow access to everyone else. Allowing access to specific groups is considered safer than denying.

      Example 4.3. Allowing access to specific users and groups

      The following example allows access to user1, user2, and members of group1, while denying access to all other users:

      [domain/your-domain-name]
      access_provider = simple
      simple_allow_users = user1, user2
      simple_allow_groups = group1

Procedure

1. Open the /etc/sssd/sssd.conf file.

2. In the [domain] section, specify the LDAP access control filter.

   • For an LDAP access provider, use the ldap_access_filter option. See the sssd-ldap(5) man page for details.

   • For an AD access provider, use the ad_access_filter option. See the sssd-ad(5) man page for details.

     Example 4.4. Allowing access to specific AD users

     For example, to allow access only to AD users who belong to the admins user group and have a unixHomeDirectory attribute set, use:

     [domain/your-AD-domain-name]
     access provider = ad
     [... file truncated ...]
     ad_access_filter = (&(memberOf=cn=admins,ou=groups,dc=example,dc=com)(unixHomeDirectory=*))