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Security Guidelines

560

control system that MySQL uses for setting up user accounts and checking database access, see

Section 6.2, “The MySQL Access Privilege System”

For answers to some questions that are often asked about MySQL Server security issues, see

Section B.9, “MySQL 5.0 FAQ: Security”

6.1.1. Security Guidelines

Anyone using MySQL on a computer connected to the Internet should read this section to avoid the
most common security mistakes.

In discussing security, it is necessary to consider fully protecting the entire server host (not just the
MySQL server) against all types of applicable attacks: eavesdropping, altering, playback, and denial of
service. We do not cover all aspects of availability and fault tolerance here.

MySQL uses security based on Access Control Lists (ACLs) for all connections, queries, and other
operations that users can attempt to perform. There is also support for SSL-encrypted connections
between MySQL clients and servers. Many of the concepts discussed here are not specific to MySQL
at all; the same general ideas apply to almost all applications.

When running MySQL, follow these guidelines:

• Do not ever give anyone (except MySQL

root

accounts) access to the

user

table in the

mysql

database! This is critical.

• Learn how the MySQL access privilege system works (see

Section 6.2, “The MySQL Access

Privilege System”

). Use the

GRANT

and

REVOKE

statements to control access to MySQL. Do not

grant more privileges than necessary. Never grant privileges to all hosts.

Checklist:

• Try

mysql -u root

. If you are able to connect successfully to the server without being asked

for a password, anyone can connect to your MySQL server as the MySQL

root

user with full

privileges! Review the MySQL installation instructions, paying particular attention to the information
about setting a

root

password. See

Section 2.18.2, “Securing the Initial MySQL Accounts”

• Use the

SHOW GRANTS

statement to check which accounts have access to what. Then use the

REVOKE

statement to remove those privileges that are not necessary.

• Do not store cleartext passwords in your database. If your computer becomes compromised,

the intruder can take the full list of passwords and use them. Instead, use

SHA1()

[956]

MD5()

[955]

, or some other one-way hashing function and store the hash value.

• Do not choose passwords from dictionaries. Special programs exist to break passwords. Even

passwords like “xfish98” are very bad. Much better is “duag98” which contains the same word
“fish” but typed one key to the left on a standard QWERTY keyboard. Another method is to use
a password that is taken from the first characters of each word in a sentence (for example, “Four
score and seven years ago” results in a password of “Fsasya”). The password is easy to remember
and type, but difficult to guess for someone who does not know the sentence. In this case, you can
additionally substitute digits for the number words to obtain the phrase “4 score and 7 years ago”,
yielding the password “4sa7ya” which is even more difficult to guess.

• Invest in a firewall. This protects you from at least 50% of all types of exploits in any software. Put

MySQL behind the firewall or in a demilitarized zone (DMZ).

Checklist:

• Try to scan your ports from the Internet using a tool such as

nmap

. MySQL uses port 3306

by default. This port should not be accessible from untrusted hosts. As a simple way to check
whether your MySQL port is open, try the following command from some remote machine, where

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