MariaDB从5.2.10(5.2.10仅在源代码包中)包含一PAM认证插件。PAM是 插件式认证模块(Pluggable Authentication Modules)的缩写,是一个用在Linux,FreeBSD,Solaris及其它操作系统中的认证框架。

注: Windows不使用PAM,所以PAM认证插件不能工作在Windows下。当然你可以用Windows客户端登录使用PAM认证的MariaDB服务器如进行在Linux或Solaris的。

应用实例

PAM makes it possible to implement various authentication scenarios of different complexity. For example,

  • authentication using passwords from /etc/shadow (indeed, this is what PAM usually does for a normal shell logins, for pop3, imap, and many other services)
  • authentication using LDAP
  • authentication using ssh passphrases
  • authentication using one-time passwords (even with SMS confirmation!)
  • combining different authentication modules, where either one or all of them are required to succeed
  • password expiration
  • user name mapping
  • limiting access by time, date, day of the week, etc.
  • logging every login attempt
  • and so on, the list is in no way exhaustive.

安装

  本插件默认没有安装,你可以这样安装:

MariaDB [test]> INSTALL PLUGIN pam SONAME 'auth_pam.so';

  或在服务器的命令行中加入--plugin-load=auth_pam.so,也可以在你的my.cnf文件中的[mysqld]部分加入此句。

  和其它的认证插件认证插件一样,你可在使用PAM认证的MariaDb中这样创建一个用户:

CREATE USER username@hostname IDENTIFIED VIA pam

  也可以这样:

GRANT SELECT ON db.* TO serg IDENTIFIED VIA pam

  你可以指定一个PAM服务名

CREATE USER test_pam IDENTIFIED VIA pam USING 'mariadb_mtr';

This line (copied verbatim from our test suite) creates a user that needs to be authenticated via PAM, using the service name mariadb_mtr.

If no service name is specified, the plugin will use "mysql" as the default PAM service name.

PAM Configuration

The PAM plugin tells MariaDB to delegate the authentication to the PAM subsystem. How exactly the authentication is performed depends on how PAM was configured. Typically, PAM configuration can be found in /etc/pam.d/ or in /etc/pam.conf. The syntax of these configuration files is described in your OS manual, for example, in man pam.d. A minimal example, that we use in our test suite, is

auth            required        pam_mariadb_mtr.so pam_test
account         required        pam_mariadb_mtr.so

This needs to be put in /etc/pam.d/mariadb_mtr — file name must match the name of the PAM service. This simple configuration file instructs the PAM subsystem that for successful authentication it is required that pam_mariadb_mtr.so module (our testing pam module) returns a success. And for an account to be valid, it is required that pam_mariadb_mtr.so module returns a success. You can find many other examples in your /etc/pam.d/ directory.

Note: if you configure PAM to use pam_unix.so and notice that MariaDB needs to run as a root user to be able to access /etc/shadow — try to upgrade your PAM installation. Newer versions of PAM do not require pam_unix.so to be run as root.

Dialog plugin

PAM authentication uses a dialog client plugin to communicate with the user. This allows MariaDB to support arbitrarily complex PAM configurations with regular or one-time passwords, challenge-response, multiple questions, or just about anything else. There is no need to install or enable anything — the dialog plugin is loaded by the client library completely automatically and transparently for the application.

User name mapping

Although PAM modules usually do not do that, PAM may change the user name in the process of authentication. For example, according to the PAM specification, one may start authenticating as John and end up being authenticated as Jim.

The MariaDB PAM authentication plugin fully supports it — the original user name is returned by the SQL function USER(), while the authenticated user name (if changed) is returned by the SQL function CURRENT_USER(), and it is the latter which defines what privileges are available to a connected user.

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