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5.3.7 LDAP authentication

This authentication method operates similarly to password except that it uses LDAP as the password verification method. LDAP is used only to validate the user name/password pairs. Therefore the user must already exist in the database before LDAP can be used for authentication.

LDAP authentication can operate in two modes. In the first mode, the server will bind to the distinguished name constructed as prefix username suffix. Typically, the prefix parameter is used to specify cn=, or DOMAIN\ in an Active Directory environment. suffix is used to specify the remaining part of the DN in a non-Active Directory environment.

In the second mode, the server first binds to the LDAP directory with a fixed user name and password, specified with ldapbinduser and ldapbinddn, and performs a search for the user trying to log in to the database. If no user and password is configured, an anonymous bind will be attempted to the directory. The search will be performed over the subtree at ldapbasedn, and will try to do an exact match of the attribute specified in ldapsearchattribute. If no attribute is specified, the uid attribute will be used. Once the user has been found in this search, the server disconnects and re-binds to the directory as this user, using the password specified by the client, to verify that the login is correct. This method allows for significantly more flexibility in where the user objects are located in the directory, but will cause two separate connections to the LDAP server to be made.

The following configuration options are supported for LDAP:

ldapserver

Name or IP of LDAP server to connect to.

ldapport

Port number on LDAP server to connect to. If no port is specified, the LDAP library's default port setting will be used.

ldaptls

Set to 1 to make the connection between PostgreSQL and the LDAP server use TLS encryption. Note that this only encrypts the traffic to the LDAP server--the connection to the client will still be unencrypted unless SSL is used.

ldapprefix

String to prepend to the user name when forming the DN to bind as, when doing simple bind authentication.

ldapsuffix

String to append to the user name when forming the DN to bind as, when doing simple bind authentication.

ldapbasedn

Root DN to begin the search for the user in, when doing search+bind authentication.

ldapbinddn

DN of user to bind to the directory with to perform the search when doing search+bind authentication.

ldapbindpasswd

Password for user to bind to the directory with to perform the search when doing search+bind authentication.

ldapsearchattribute

Attribute to match against the user name in the search when doing search+bind authentication.

Note: Since LDAP often uses commas and spaces to separate the different parts of a DN, it is often necessary to use double-quoted parameter values when configuring LDAP options, for example:

ldapserver=ldap.example.net ldapprefix="cn=" 
  ldapsuffix=", dc=example, dc=net"