6.4.1.9 Socket Peer-Credential Pluggable Authentication

This section describes how to install the socket authentication plugin. For general information about installing plugins, see Section 5.6.1, “Installing and Uninstalling Plugins”.

To be usable by the server, the plugin library file must be located in the MySQL plugin directory (the directory named by the plugin_dir system variable). If necessary, configure the plugin directory location by setting the value of plugin_dir at server startup.

To load the plugin at server startup, use the --plugin-load-add option to name the library file that contains it. With this plugin-loading method, the option must be given each time the server starts. For example, put these lines in the server my.cnf file:

[mysqld]
plugin-load-add=auth_socket.so

After modifying my.cnf, restart the server to cause the new settings to take effect.

Alternatively, to register the plugin at runtime, use this statement:

INSTALL PLUGIN loads the plugin immediately, and also registers it in the mysql.plugins system table to cause the server to load it for each subsequent normal startup.

To verify plugin installation, examine the INFORMATION_SCHEMA.PLUGINS table or use the SHOW PLUGINS statement (see Section 5.6.2, “Obtaining Server Plugin Information”). For example:

If the plugin fails to initialize, check the server error log for diagnostic messages.

To associate MySQL accounts with the socket plugin, see Using Socket Pluggable Authentication.

The method used to uninstall the socket authentication plugin depends on how you installed it:

The socket plugin checks whether the socket user name (the operating system user name) matches the MySQL user name specified by the client program to the server. If the names do not match, the plugin checks whether the socket user name matches the name specified in the authentication_string column of the mysql.user system table row. If a match is found, the plugin permits the connection. The authentication_string value can be specified using an IDENTIFIED ...AS clause with CREATE USER or ALTER USER.

Suppose that a MySQL account is created for an operating system user named valerie who is to be authenticated by the auth_socket plugin for connections from the local host through the socket file:

If a user on the local host with a login name of stefanie invokes mysql with the option --user=valerie to connect through the socket file, the server uses auth_socket to authenticate the client. The plugin determines that the --user option value (valerie) differs from the client user's name (stephanie) and refuses the connection. If a user named valerie tries the same thing, the plugin finds that the user name and the MySQL user name are both valerie and permits the connection. However, the plugin refuses the connection even for valerie if the connection is made using a different protocol, such as TCP/IP.

To permit both the valerie and stephanie operating system users to access MySQL through socket file connections that use the account, this can be done two ways:

To access the account, both valerie and stephanie specify --user=valerie at connect time.