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5.5.6.2. Using SSL Connections

To use SSL connections between the MySQL server and client programs, your system must support either OpenSSL or yaSSL and your version of MySQL must be built with SSL support.

To make it easier to use secure connections, MySQL is bundled with yaSSL as of MySQL 5.0.10. (MySQL and yaSSL employ the same licensing model, whereas OpenSSL uses an Apache-style license.) yaSSL support initially was available only for a few platforms, but now it is available on all platforms supported by Oracle Corporation.

To get secure connections to work with MySQL and SSL, you must do the following:

  1. If you are not using a binary (precompiled) version of MySQL that has been built with SSL support, and you are going to use OpenSSL rather than the bundled yaSSL library, install OpenSSL if it has not already been installed. We have tested MySQL with OpenSSL 0.9.6. To obtain OpenSSL, visit http://www.openssl.org.

    Building MySQL using OpenSSL requires a shared OpenSSL library, otherwise linker errors occur. Alternatively, build MySQL using yaSSL.

  2. If you are not using a binary (precompiled) version of MySQL that has been built with SSL support, configure a MySQL source distribution to use SSL. When you configure MySQL, invoke the configure script with the appropriate option to select the SSL library that you want to use.

    For yaSSL: 

    shell> ./configure --with-yassl

    For OpenSSL: 

    shell> ./configure --with-openssl

    Before MySQL 5.0, it was also neccessary to use --with-vio, but that option is no longer required.

    Note that yaSSL support on Unix platforms requires that either /dev/urandom or /dev/random be available to retrieve true random numbers. For additional information (especially regarding yaSSL on Solaris versions prior to 2.8 and HP-UX), see Bug#13164.

  3. Make sure that the user in the mysql database includes the SSL-related columns (beginning with ssl_ and x509_). If your user table does not have these columns, it must be upgraded; see Section 4.4.9, “mysql_upgrade — Check Tables for MySQL Upgrade”.

  4. To check whether a server binary is compiled with SSL support, invoke it with the --ssl option. An error will occur if the server does not support SSL: 

    shell> mysqld --ssl --help
060525 14:18:52 [ERROR] mysqld: unknown option '--ssl'

    To check whether a running mysqld server supports SSL, examine the value of the have_ssl system variable (if you have no have_ssl variable, check for have_openssl): 

    mysql> SHOW VARIABLES LIKE 'have_ssl';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| have_ssl      | YES   |
+---------------+-------+

    If the value is YES, the server supports SSL connections. If the value is DISABLED, the server supports SSL connections but was not started with the appropriate --ssl-xxx options (described later in this section).

To enable SSL connections, the proper SSL-related options must be used (see Section 5.5.6.3, “SSL Command Options”).

To start the MySQL server so that it allows clients to connect via SSL, use the options that identify the key and certificate files the server needs when establishing a secure connection: 

shell> mysqld --ssl-ca=ca-cert.pem \
       --ssl-cert=server-cert.pem \
       --ssl-key=server-key.pem

  • --ssl-ca identifies the Certificate Authority (CA) certificate.

  • --ssl-cert identifies the server public key. This can be sent to the client and authenticated against the CA certificate that it has.

  • --ssl-key identifies the server private key.

To establish a secure connection to a MySQL server with SSL support, the options that a client must specify depend on the SSL requirements of the user account that the client uses. (See the discussion of the REQUIRE clause in Section 12.4.1.3, “GRANT Syntax”.)

If the account has no special SSL requirements or was created using a GRANT statement that includes the REQUIRE SSL option, a client can connect securely by using just the --ssl-ca option: 

shell> mysql --ssl-ca=ca-cert.pem

To require that a client certificate also be specified, create the account using the REQUIRE X509 option. Then the client must also specify the proper client key and certificate files or the server will reject the connection: 

shell> mysql --ssl-ca=ca-cert.pem \
       --ssl-cert=client-cert.pem \
       --ssl-key=client-key.pem

In other words, the options are similar to those used for the server. Note that the Certificate Authority certificate has to be the same.

A client can determine whether the current connection with the server uses SSL by checking the value of the Ssl_cipher status variable. The value of Ssl_cipher is nonempty if SSL is used, and empty otherwise. For example: 

mysql> SHOW STATUS LIKE 'Ssl_cipher';
+---------------+--------------------+
| Variable_name | Value              |
+---------------+--------------------+
| Ssl_cipher    | DHE-RSA-AES256-SHA |
+---------------+--------------------+

For the mysql client, you can use the STATUS or \s command and check the SSL line: 

mysql> \s
...
SSL:                    Not in use
...

Or: 

mysql> \s
...
SSL:                    Cipher in use is DHE-RSA-AES256-SHA
...

To establish a secure connection from within an application program, use the mysql_ssl_set() C API function to set the appropriate certificate options before calling mysql_real_connect(). See Section 20.8.3.67, “mysql_ssl_set()”. After the connection is established, you can use mysql_get_ssl_cipher() to determine whether SSL is in use. A non-NULL return value indicates a secure connection and names the SSL cipher used for encryption. A NULL return value indicates that SSL is not being used. See Section 20.8.3.33, “mysql_get_ssl_cipher()”.