30.4.2. Configuring an LDAP Domain

An LDAP domain simply means that SSSD uses an LDAP directory as the identity provider (and, optionally, also as an authentication provider). SSSD supports several major directory services:
  • Red Hat Directory Server
  • OpenLDAP
  • Microsoft Active Directory 2008, with Subsystem for UNIX-based Applications

Note

DNS service discovery allows the LDAP backend to find the appropriate DNS servers to connect to automatically using a special DNS query.

30.4.2.1. Parameters for Configuring an LDAP Domain

An LDAP directory can function as both an identity provider and an authentication provider. The configuration requires enough information to identify and connect to the user directory in the LDAP server, but the way that those connection parameters are defined is flexible.
Other options are available to provide more fine-grained control, like specifying a user account to use to connect to the LDAP server or using different LDAP servers for password operations. The most common options are listed in Table 30.5, “LDAP Domain Configuration Parameters”. All of the options listed in Section 30.4.1, “General Rules and Options for Configuring a Domain” are also available for LDAP domains.

Note

Many other options are listed in the man page for LDAP domain configuration, sssd-ldap(5).

Table 30.5. LDAP Domain Configuration Parameters

Parameter Description
ldap_uri Gives a comma-separated list of the URIs of the LDAP servers to which SSSD will connect. The list is given in order of preference, so the first server in the list is tried first. Listing additional servers provides failover protection. This can be detected from the DNS SRV records if it is not given.
ldap_search_base Gives the base DN to use for performing LDAP user operations.
ldap_tls_reqcert Specifies how to check for SSL server certificates in a TLS session. There are four options:
  • never disables requests for certificates.
  • allow requests a certificate, but proceeds normally even if no certificate is given or a bad certificate is given.
  • try requests a certificate and proceeds normally if no certificate is given, If a bad certificate is given, the session terminates.
  • demand and hard are the same option. This requires a valid certificate or the session is terminated.
The default is hard.
ldap_tls_cacert Gives the full path and file name to the file that contains the CA certificates for all of the CAs that SSSD recognizes. SSSD will accept any certificate issued by these CAs.
This uses the OpenLDAP system defaults if it is not given explicitly.
ldap_referrals Sets whether SSSD will use LDAP referrals, meaning forwarding queries from one LDAP database to another. SSSD supports database-level and subtree referrals. For referrals within the same LDAP server, SSSD will adjust the DN of the entry being queried. For referrals that go to different LDAP servers, SSSD does an exact match on the DN. Setting this value to true enables referrals. This is the default.
ldap_schema Sets what version of schema to use when searching for user entries. This can be either rfc2307 or rfc2307bis. The default is rfc2307.
In RFC 2307, group objects use a multi-valued attribute, memberuid, which lists the names of the users that belong to that group. In RFC 2307bis, group objects use the member attribute, which contains the full distinguished name (DN) of a user or group entry. RFC 2307bis allows nested groups usning the member attribute. Because these different schema use different definitions for group membership, using the wrong LDAP schema with SSSD can affect both viewing and managing network resources, even if the appropriate permissions are in place.
For example, with RFC 2307bis, all groups are returned when using nested groups or primary/secondary groups.
$ id
uid=500(myserver) gid=500(myserver) groups=500(myserver),510(myothergroup)
If SSSD is using RFC 2307 schema, only the primary group is returned.
This setting only affects how SSSD determines the group members. It does not change the actual user data.
ldap_search_timeout Sets the time, in seconds, that LDAP searches are allowed to run before they are canceled and cached results are returned. This defaults to five when the enumerate value is false and defaults to 30 when enumerate is true.
When an LDAP search times out, SSSD automatically switches to offline mode.
ldap_network_timeout Sets the time, in seconds, SSSD attempts to poll an LDAP server after a connection attempt fails. The default is six seconds.
ldap_opt_timeout Sets the time, in seconds, to wait before aborting synchronous LDAP operations if no response is received from the server. This option also controls the timeout when communicating with the KDC in case of a SASL bind. The default is five seconds.