For both of these approaches, an internally named LDAP server must be defined in the ClickHouse config so that other parts of the config can refer to it.
- The resulting DN will be constructed by replacing all `{user_name}` substrings of the template with the actual user name during each authentication attempt.
-`verification_cooldown` — A period of time, in seconds, after a successful bind attempt, during which the user will be assumed to be successfully authenticated for all consecutive requests without contacting the LDAP server.
A remote LDAP server can be used as a method for verifying passwords for locally defined users (users defined in `users.xml` or in local access control paths). To achieve this, specify previously defined LDAP server name instead of `password` or similar sections in the user definition.
At each login attempt, ClickHouse tries to "bind" to the specified DN defined by the `bind_dn` parameter in the [LDAP server definition](#ldap-server-definition) using the provided credentials, and if successful, the user is considered authenticated. This is often called a "simple bind" method.
When SQL-driven [Access Control and Account Management](../access-rights.md#access-control) is enabled, users that are authenticated by LDAP servers can also be created using the [CREATE USER](../../sql-reference/statements/create/user.md#create-user-statement) statement.
In addition to the locally defined users, a remote LDAP server can be used as a source of user definitions. To achieve this, specify previously defined LDAP server name (see [LDAP Server Definition](#ldap-server-definition)) in the `ldap` section inside the `users_directories` section of the `config.xml` file.
At each login attempt, ClickHouse tries to find the user definition locally and authenticate it as usual. If the user is not defined, ClickHouse will assume the definition exists in the external LDAP directory and will try to "bind" to the specified DN at the LDAP server using the provided credentials. If successful, the user will be considered existing and authenticated. The user will be assigned roles from the list specified in the `roles` section. Additionally, LDAP "search" can be performed and results can be transformed and treated as role names and then be assigned to the user if the `role_mapping` section is also configured. All this implies that the SQL-driven [Access Control and Account Management](../access-rights.md#access-control) is enabled and roles are created using the [CREATE ROLE](../../sql-reference/statements/create/role.md#create-role-statement) statement.
Note that `my_ldap_server` referred in the `ldap` section inside the `user_directories` section must be a previously defined LDAP server that is configured in the `config.xml` (see [LDAP Server Definition](#ldap-server-definition)).
- When a user authenticates, while still bound to LDAP, an LDAP search is performed using `search_filter` and the name of the logged-in user. For each entry found during that search, the value of the specified attribute is extracted. For each attribute value that has the specified prefix, the prefix is removed, and the rest of the value becomes the name of a local role defined in ClickHouse, which is expected to be created beforehand by the [CREATE ROLE](../../sql-reference/statements/create/role.md#create-role-statement) statement.
- The resulting DN will be constructed by replacing all `{user_name}` and `{bind_dn}` substrings of the template with the actual user name and bind DN during each LDAP search.
- The resulting filter will be constructed by replacing all `{user_name}`, `{bind_dn}` and `{base_dn}` substrings of the template with the actual user name, bind DN and base DN during each LDAP search.
-`prefix` — Prefix, that will be expected to be in front of each string in the original list of strings returned by the LDAP search. The prefix will be removed from the original strings and the resulting strings will be treated as local role names. Empty by default.
