6.4.1 Configuring MySQL to Use Encrypted Connections

To enable encrypted connections, your MySQL distribution must be built with SSL support, as described in Section 6.4.5, “Building MySQL with Support for Encrypted Connections”. In addition, several options are available to indicate whether to use encrypted connections, and to specify the appropriate certificate and key files. This section provides general guidance about configuring the server and clients for encrypted connections:

• Server-Side Startup Configuration for Encrypted Connections

• Client-Side Configuration for Encrypted Connections

For a complete list of options related to establishment of encrypted connections, see Section 6.4.2, “Command Options for Encrypted Connections”. To create any required certificate and key files, see Section 6.4.3, “Creating SSL and RSA Certificates and Keys”.

Encrypted connections can be used between master and slave replication servers. See Section 17.3.8, “Setting Up Replication to Use Encrypted Connections”.

Encrypted connections are available through the MySQL C API. See Section 23.8.15, “C API Encrypted Connection Support”.

Note

If the server is compiled against OpenSSL, clients from MySQL 5.6 versions older than 5.6.17 are not able to connect to the server using encrypted connections if the client library is compiled using yaSSL. Either use a client and server compiled using the same SSL package, or upgrade to clients compiled against a client library version from MySQL 5.6.17 or higher.

Server-Side Startup Configuration for Encrypted Connections

These options on the server side identify the certificate and key files the server uses when permitting clients to establish encrypted connections:

• --ssl-ca: The path name of the Certificate Authority (CA) certificate file. (--ssl-capath is similar but specifies the path name of a directory of CA certificate files.)

• --ssl-cert: The path name of the server public key certificate file. This can be sent to the client and authenticated against the CA certificate that it has.

• --ssl-key: The path name of the server private key file.

For example, to enable the server for encrypted connections, start it with these lines in the my.cnf file, changing the file names as necessary:

[mysqld]
ssl-ca=ca.pem
ssl-cert=server-cert.pem
ssl-key=server-key.pem

Each option names a file in PEM format. If you have a MySQL source distribution, you can test your setup using the demonstration certificate and key files in its mysql-test/std_data directory.

MySQL also provides these options for server-side SSL control:

• --ssl-cipher: The list of permitted ciphers for connection encryption.

• --ssl-crl: The path name of the file containing certificate revocation lists. (--ssl-crlpath is similar but specifies the path name of a directory of certificate revocation-list files.)

The server uses the values of the --ssl-xxx options as the values of the used certificate and key files to set the corresponding system variables (ssl_ca, ssl_cert, ssl_key, and so forth).

Client-Side Configuration for Encrypted Connections

These options on the client side identify the certificate and key files clients use when establishing encrypted connections to the server. They are similar to the options used on the server side, but --ssl-cert and --ssl-key identify the client public and private key:

• --ssl-ca: The path name of the Certificate Authority (CA) certificate file. This option, if used, must specify the same certificate used by the server. (--ssl-capath is similar but specifies the path name of a directory of CA certificate files.)

• --ssl-cert: The path name of the client public key certificate file.

• --ssl-key: The path name of the client private key file.

For additional security relative to that provided by the default encryption, clients can supply a CA certificate matching the one used by the server and enable host name identity verification. In this way, the server and client place their trust in the same CA certificate and the client verifies that the host to which it connected is the one intended:

• To specify the CA certificate, use --ssl-ca (or --ssl-capath).

• To enable host name identity verification as well, specify --ssl-verify-server-cert.

• To require an encrypted connection, specify --ssl-mode=REQUIRED.

Depending on the encryption requirements of the MySQL account used by a client, the client may be required to specify certain options to connect using encryption to a MySQL server that supports encrypted connections.

Suppose that you want to connect using an account that has no special encryption requirements or was created using a GRANT statement that includes the REQUIRE SSL option. As a recommended set of encrypted-connection options, start the server with at least --ssl-cert and --ssl-key, and invoke the client with --ssl-ca (or --ssl-capath). A client can connect using encryption like this:

mysql --ssl-ca=ca.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:

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

For additional information about the REQUIRE clause, see the discussion in Section 13.7.1.4, “GRANT Syntax”.

To prevent use of encryption and override other --ssl-xxx options, invoke the client program with --ssl=0 or a synonym (--skip-ssl, --disable-ssl):

mysql --ssl=0

MySQL also provides these options for client-side SSL control:

• --ssl-cipher: The list of permitted ciphers for connection encryption.

• --ssl-crl: The path name of the file containing certificate revocation lists. (--ssl-crlpath is similar but specifies the path name of a directory of certificate revocation-list files.)

To determine whether the current connection with the server uses encryption, check the session value of the Ssl_cipher status variable. If the value is empty, the connection is not encrypted. Otherwise, the connection is encrypted and the value indicates the encryption cipher. For example:

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

For the mysql client, an alternative is to 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
...