Making MariaDB Secure Against Attackers

When you connect to a MariaDB server, you should use a password. The password is not transmitted in clear text over the connection. Password handling during the client connection sequence was upgraded in MariaDB to be very secure. If you are still using pre-4.1.1-style passwords, the encryption algorithm is not as strong as the newer algorithm. With some effort, a clever attacker who can sniff the traffic between the client and the server can crack the password. (See , "Password Hashing in MySQL", for a discussion of the different password handling methods.)

All other information is transferred as text, and can be read by anyone who is able to watch the connection. If the connection between the client and the server goes through an untrusted network, and you are concerned about this, you can use the compressed protocol to make traffic much more difficult to decipher. You can also use MySQL's internal SSL support to make the connection even more secure. See , "Using SSL for Secure Connections". Alternatively, use SSH to get an encrypted TCP/IP connection between a MariaDB server and a MariaDB client. You can find an Open Source SSH client at http://www.openssh.org/, and a commercial SSH client at http://www.ssh.com/.

To make a MariaDB system secure, you should strongly consider the following suggestions:

• Require all MariaDB accounts to have a password. A client program does not necessarily know the identity of the person running it. It is common for client/server applications that the user can specify any user name to the client program. For example, anyone can use the mysql program to connect as any other person simply by invoking it as mysql -u other_user db_name if other_user has no password. If all accounts have a password, connecting using another user's account becomes much more difficult.

  For a discussion of methods for setting passwords, see , "Assigning Account Passwords".

• Never run the MariaDB server as the Unix root user. This is extremely dangerous, because any user with the FILE privilege is able to cause the server to create files as root (for example, ~root/.bashrc). To prevent this, mysqld refuses to run as root unless that is specified explicitly using the --user=root option.

  mysqld can (and should) be run as an ordinary, unprivileged user instead. You can create a separate Unix account named MariaDB to make everything even more secure. Use this account only for administering MySQL. To start mysqld as a different Unix user, add a user option that specifies the user name in the [mysqld] group of the my.cnf option file where you specify server options. For example:

  [mysqld]
  user=mysql
  

  This causes the server to start as the designated user whether you start it manually or by using mysqld_safe or mysql.server. For more details, see , "How to Run MariaDB as a Normal User".

  Running mysqld as a Unix user other than root does not mean that you need to change the root user name in the user table. User names for MariaDB accounts have nothing to do with user names for Unix accounts.

• Do not permit the use of symlinks to tables. (This capability can be disabled with the --skip-symbolic-links option.) This is especially important if you run mysqld as root, because anyone that has write access to the server's data directory then could delete any file in the system! See , "Using Symbolic Links for Tables on Unix".
• Make sure that the only Unix user account with read or write privileges in the database directories is the account that is used for running mysqld.
• Do not grant the PROCESS or SUPER privilege to nonadministrative users. The output of mysqladmin processlist and SHOW PROCESSLIST shows the text of any statements currently being executed, so any user who is permitted to see the server process list might be able to see statements issued by other users such as UPDATE user SET password=PASSWORD('not_secure').

  mysqld reserves an extra connection for users who have the SUPER privilege, so that a MariaDB root user can log in and check server activity even if all normal connections are in use.

  The SUPER privilege can be used to terminate client connections, change server operation by changing the value of system variables, and control replication servers.

• Do not grant the FILE privilege to nonadministrative users. Any user that has this privilege can write a file anywhere in the file system with the privileges of the mysqld daemon. To make this a bit safer, files generated with SELECT ... INTO OUTFILE do not overwrite existing files and are writable by everyone.

  The FILE privilege may also be used to read any file that is world-readable or accessible to the Unix user that the server runs as. With this privilege, you can read any file into a database table. This could be abused, for example, by using LOAD DATA to load /etc/passwd into a table, which then can be displayed with SELECT.

• Stored programs and views should be written using the security guidelines discussed in , "Access Control for Stored Programs and Views".
• If you do not trust your DNS, you should use IP addresses rather than host names in the grant tables. In any case, you should be very careful about creating grant table entries using host name values that contain wildcards.
• If you want to restrict the number of connections permitted to a single account, you can do so by setting the max_user_connections variable in mysqld. The GRANT statement also supports resource control options for limiting the extent of server use permitted to an account. See , "GRANT Syntax".
• If the plugin directory is writable by the server, it may be possible for a user to write executable code to a file in the directory using SELECT ... INTO DUMPFILE. This can be prevented by making plugin_dir read only to the server or by setting --secure-file-priv to a directory where SELECT writes can be made safely.

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