When you connect to a MySQL 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 MySQL 4.1.1 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 Section 2.2.4, “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 Section 5.9, “Using SSL for Secure Connections”. Alternatively, use SSH to get an encrypted TCP/IP connection between a MySQL server and a MySQL client. You can find an Open Source SSH client at http://www.openssh.org/, and a comparison of both Open Source and Commercial SSH clients at http://en.wikipedia.org/wiki/Comparison_of_SSH_clients.
To make a MySQL system secure, you should strongly consider the following suggestions:
Require all MySQL 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 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 Section 5.5, “Assigning Account Passwords”.
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.
Never run the MySQL server as the Unix
user. This is extremely dangerous, because any user with the
FILE privilege is able to cause
the server to create files as
~root/.bashrc). To prevent this,
mysqld refuses to run as
root unless that is specified explicitly
mysqld can (and should) be run as an
ordinary, unprivileged user instead. You can create a separate
Unix account named
mysql 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:
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 Section 2.5, “How to Run MySQL as a Normal User”.
Running mysqld as a Unix user other than
root does not mean that you need to change
root user name in the
user table. User names for MySQL
accounts have nothing to do with user names for Unix
Do not grant the
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. This
includes the server's data directory containing the files that
implement the privilege tables. To make
FILE-privilege operations a bit
safer, files generated with
SELECT ... INTO
OUTFILE do not overwrite existing files and are
writable by everyone.
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
DATA to load
/etc/passwd into a
table, which then can be displayed with
Do not grant the
SUPER privilege to
nonadministrative users. The output of mysqladmin
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
mysqld reserves an extra connection for
users who have the
privilege, so that a MySQL
root user can
log in and check server activity even if all normal
connections are in use.
SUPER privilege can be used
to terminate client connections, change server operation by
changing the value of system variables, and control
Do not permit the use of symlinks to tables. (This capability
can be disabled with the
option.) This is especially important if you run
anyone that has write access to the server's data directory
then could delete any file in the system! See
Using Symbolic Links for MyISAM Tables on Unix.
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
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
... INTO DUMPFILE. This can be prevented by making
plugin_dir read only to the
server or by setting
--secure-file-priv to a
can be made safely.