ldap - LDAP as a naming repository
LDAP refers to Lightweight Directory Access Protocol, which is an industry standard for accessing directory servers. By initializing the client using ldapclient(8) and using the keyword ldap in the name service switch file, /etc/nsswitch.conf, Oracle Solaris clients can obtain naming information from an LDAP server. Information such as usernames, hostnames, and passwords are stored on the LDAP server in a Directory Information Tree or DIT. The DIT consists of entries which in turn are composed of attributes. Each attribute has a type and one or more values.
Oracle Solaris LDAP clients use the LDAP v3 protocol to access naming information from LDAP servers. The LDAP server must support the object classes and attributes defined in RFC2307bis (draft), which maps the naming service model on to LDAP. As an alternate to using the schema defined in RFC2307bis (draft), the system can be configured to use other schema sets and the schema mapping feature is configured to map between the two.
The ldapclient(8) utility can make an Oracle Solaris machine an LDAP client by setting up the appropriate directories, files, and configuration information. The LDAP client caches this configuration information in local cache files. This configuration information is accessed through the ldap_cachemgr(8) daemon. This daemon also refreshes the information in the configuration files from the LDAP server, providing better performance and security. The ldap_cachemgr must run at all times for the proper operation of the naming services.
There are two types of configuration information, the information available through a profile, and the information configured per client. The profile contains all the information as to how the client accesses the directory. The credential information for proxy user is configured on a per client basis and is not downloaded through the profile.
The profile contains server-specific parameters that are required by all clients to locate the servers for the desired LDAP domain. This information could be the server's IP address and the search base Distinguished Name (DN), for instance. It is configured on the client from the default profile during client initialization and is periodically updated by the ldap_cachemgr daemon when the expiration time has elapsed.
Client profiles can be stored on the LDAP server and can be used by the ldapclient utility to initialize an LDAP client. Using the client profile is the easiest way to configure a client machine. See ldapclient(8).
Credential information includes client-specific parameters that are used by a client. This information could be the Bind DN (LDAP “login” name) of the client and the password. If these parameters are required, they are manually defined during the initialization through ldapclient(8).
The naming information is stored in containers on the LDAP server. A container is a non-leaf entry in the DIT that contains naming service information. Containers are similar to maps in NIS. A default mapping between the NIS databases and the containers in LDAP is presented below. The location of these containers as well as their names can be overridden through the use of serviceSearchDescriptors. For more information, see ldapclient(8).
The security model for clients is defined by a combination of the credential level to be used, the authentication method, and the PAM modules to be used. The credential level defines what credentials the client should use to authenticate to the directory server, and the authentication method defines the method of choice. Both these can be set with multiple values. The Oracle Solaris LDAP supports the following values for credential level :
The Oracle Solaris LDAP supports the following values for authentication method:
When the credential level is configured as self, DNS must be configured and the authentication method must be sasl/GSSAPI. The hosts and ipnodes in /etc/nsswitch.conf must be configured to use DNS, for example hosts: dns files and ipnodes: dns files.
sasl/GSSAPI automatically uses GSSAPI confidentiality and integrity options, if they are configured on the directory server.
The credential level of self enables per-user naming service lookups, or lookups that use the GSSAPI credentials of the user when connecting to the directory server. Currently the only GSSAPI mechanism supported in this model is Kerberos V5. Kerberos must be configured before you can use this credential level.
More protection can be provided by means of access control, allowing the server to grant access for certain containers or entries. Access control is specified by Access Control Lists (ACLs) that are defined and stored in the LDAP server. The Access Control Lists on the LDAP server are called Access Control Instructions (ACIs) by the SunOne Directory Server. Each ACL or ACI specifies one or more directory objects, for example, the cn attribute in a specific container, one or more clients to whom you grant or deny access, and one or more access rights that determine what the clients can do to or with the objects. Clients can be users or applications. Access rights can be specified as read and write, for example.
A sample nsswitch.conf(5) file called nsswitch.ldap is provided in the /etc directory. This is copied to /etc/nsswitch.conf by the ldapclient(8) utility. This file uses LDAP as a repository for the different databases in the nsswitch.conf file.
The following is a list of the user commands related to LDAP:
Prepares a SunOne Directory Server to be ready to support Solaris LDAP clients.
Creates LDAP entries from corresponding /etc files.
Initializes LDAP clients, or generates a configuration profile to be stored in the directory.
Lists the contents of the LDAP naming space.
Files that contain the LDAP configuration of the client. Do not manually modify these files. Their content is not guaranteed to be human readable. Use ldapclient(8) to update them.
Configuration file for the name-service switch.
Sample configuration file for the name-service switch configured with LDAP and files.
PAM framework configuration file.
Alternate PAM framework configuration files.
ldaplist(1), nsswitch.conf(5), pam.conf(5), pam_authtok_check(7), pam_authtok_get(7), pam_authtok_store(7), pam_dhkeys(7), pam_ldap(7), pam_passwd_auth(7), pam_unix_account(7), pam_unix_auth(7), pam_unix_session(7), idsconfig(8), ldap_cachemgr(8), ldapaddent(8), ldapclient(8)