# documentation:2.0:authslave
Keywords: documentation,2.0,authslave

# Slave

Authentication | Users | Password
--- | --- | ---
✔ | ✔ |

## Presentation

LL::NG Slave backend relies on HTTP headers to retrieve user login and/or attributes.

- Authentication: will check user login in a header and create session without prompting any credentials (but will register client IP and creation date)
- Users: collect data transferred in HTTP headers by the “master”.

It allows one to put LL::NG::portal behind another web SSO, or behind a SSL hardware to delegate SSL authentication to that hardware.

## Configuration

In Manager, go in `General Parameters` > `Authentication modules` and choose Slave for authentication or users module.

Then, go in `Slave parameters`:

- Authentication level: authentication level for this module.
- Header for user login: header that contains the user main login
- Master's IP address: the IP addresses of servers which are accredited to authenticate user. This is a security point, to prevent someone to create a session by sending custom headers. You can set one or several IP addresses, separated by spaces, or let this parameter empty to disable the checking.
- Control header name: header that contains a value to control. Let this parameter empty to disable the checking.
- Control header content: value to control. Let this parameter empty to disable the checking.

You have then to declare HTTP headers exported by the main SSO (in Exported Variables). Example :

Key (LL::NG name) | Value (HTTP header name)
--- | ---
uid | Auth-User
mail | User-Email

See also exported variables configuration.