6.3.1 Configuring MySQL to Use Encrypted Connections

To enable encrypted connections, your MySQL distribution must be built with SSL support, as described in Section 2.9.6, “Configuring SSL Library Support”. In addition, several configuration parameters 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

Encrypted connections also can be used in other contexts, as discussed in these additional sections:

• Between source and replica servers. See Section 17.3.8, “Setting Up Replication to Use Encrypted Connections”.

• By client programs that are based on the MySQL C API. See Support for Encrypted Connections.

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.

Instructions for creating any required certificate and key files are available in Section 6.3.3, “Creating SSL and RSA Certificates and Keys”.

Server-Side Startup Configuration for Encrypted Connections

These system variables on the server side specify 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 certificate 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 certificate and key system variable 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 system variables for server-side encrypted-connection control:

• ssl_cipher: The list of permissible 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.)

Client-Side Configuration for Encrypted Connections

For a complete list of client options related to establishment of encrypted connections, see Command Options 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 ssl_ca, ssl_cert, and ssl_key system variables 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.

• --ssl-cipher: The list of permissible 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.)

Important

--ssl-mode=REQUIRED produces an encrypted connection. However, to help prevent sophisticated man-in-the-middle attacks, it is also important for the client to verify the server’s identity. Adding the --ssl-verify-server-cert option achieves this. To implement that additional option, you must first ensure that the CA certificate for the server is reliably available to all the clients that use it in your environment, otherwise availability issues will result.

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 the MySQL server.

Suppose that you want to connect using an account that has no special encryption requirements or that was created using a GRANT statement that included the REQUIRE SSL clause. As a recommended set of encrypted-connection options, start the server with at least the ssl_cert and ssl_key system variables set, and invoke the client with the --ssl-ca (or --ssl-capath) option. 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 a REQUIRE X509 clause. Then the client must also specify the proper client key and certificate files or the server rejects the connection (enter the command on a single line):

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

For additional information about the REQUIRE clause, see Section 13.7.1.4, “GRANT Statement”.

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

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
...