plugin authenticates clients that connect from the local host
through the Unix socket file. The plugin uses the
SO_PEERCRED socket option to obtain
information about the user running the client program. Thus, the
plugin can be used only on systems that support the
SO_PEERCRED option, such as Linux.
The source code for this plugin can be examined as a relatively simple example demonstrating how to write a loadable authentication plugin.
The following table shows the plugin and library file names. The
file must be located in the directory named by the
plugin_dir system variable.
Table 6.18 Plugin and Library Names for Socket Peer-Credential Authentication
|Plugin or File||Plugin or File Name|
|Client-side plugin||None, see discussion|
The following sections provide installation and usage information specific to socket pluggable authentication:
For general information about pluggable authentication in MySQL, see Section 6.2.13, “Pluggable Authentication”.
This section describes how to install the socket authentication plugin. For general information about installing plugins, see Section 5.5.1, “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
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, restart the
server to cause the new settings to take effect.
Alternatively, to load the plugin at runtime, use this statement:
INSTALL PLUGIN auth_socket SONAME 'auth_socket.so';
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 without
the need for
To verify plugin installation, examine the Information Schema
PLUGINS table or use the
SHOW PLUGINS statement (see
Section 5.5.2, “Obtaining Server Plugin Information”). For example:
mysql> SELECT PLUGIN_NAME, PLUGIN_STATUS FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME LIKE '%socket%'; +-------------+---------------+ | PLUGIN_NAME | PLUGIN_STATUS | +-------------+---------------+ | auth_socket | ACTIVE | +-------------+---------------+
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:
If you installed the plugin at server startup using a
--plugin-load-addoption, restart the server without the option.
If you installed the plugin at runtime using an
INSTALL PLUGINstatement, it remains installed across server restarts. To uninstall it, use
UNINSTALL PLUGIN auth_socket;
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
CREATE USER or
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:
CREATE USER 'valerie'@'localhost' IDENTIFIED WITH auth_socket;
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
valerie) differs from the client
user's name (
stephanie) and refuses the
connection. If a user named
the same thing, the plugin finds that the user name and the
MySQL user name are both
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
stephanie operating system users to access
MySQL through socket file connections that use the account,
this can be done two ways:
Name both users at account-creation time, one following
CREATE USER, and the other in the authentication string:
CREATE USER 'valerie'@'localhost' IDENTIFIED WITH auth_socket AS 'stephanie';
If you have already used
CREATE USERto create the account for a single user, use
ALTER USERto add the second user:
CREATE USER 'valerie'@'localhost' IDENTIFIED WITH auth_socket; ALTER USER 'valerie'@'localhost' IDENTIFIED WITH auth_socket AS 'stephanie';
To access the account, both
--user=valerie at connect time.