This section describes how C applications use the C API capabilities for encrypted connections. By default, MySQL programs attempt to connect using encryption if the server supports encrypted connections, falling back to an unencrypted connection if an encrypted connection cannot be established (seeConfiguring MySQL to Use Encrypted Connections). For applications that require control beyond the default behavior over how encrypted connections are established, the C API provides these capabilities:
The
mysql_options()function enables applications to set the appropriate SSL/TLS options before callingmysql_real_connect(). For example, to require the use of an encrypted connection, seeEnforcing an Encrypted Connection.The
mysql_get_ssl_cipher()function enables applications to determine, after a connection has been established, whether the connection uses encryption. ANULLreturn value indicates that encryption is not being used. A non-NULLreturn value indicates an encrypted connection and names the encryption cipher. SeeSection 5.4.34, “mysql_get_ssl_cipher()”.
mysql_options() provides the following options for control over use of encrypted connections. For option details, seeSection 5.4.50, “mysql_options()”.
MYSQL_OPT_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.MYSQL_OPT_SSL_CAPATH: The path name of the directory that contains trusted SSL CA certificate files.MYSQL_OPT_SSL_CERT: The path name of the client public key certificate file.MYSQL_OPT_SSL_CIPHER: The list of permissible ciphers for SSL encryption.MYSQL_OPT_SSL_CRL: The path name of the file containing certificate revocation lists.MYSQL_OPT_SSL_CRLPATH: The path name of the directory that contains certificate revocation list files.MYSQL_OPT_SSL_KEY: The path name of the client private key file.MYSQL_OPT_SSL_MODE: The connection security state.MYSQL_OPT_SSL_VERIFY_SERVER_CERT: Whether to perform host name identity verification of the server certificate Common Name value.MYSQL_OPT_TLS_VERSION: The encryption protocols the client permits.
mysql_ssl_set() can be used as a convenience routine that is equivalent to a set ofmysql_options() calls that specify certificate and key files, encryption ciphers, and so forth. SeeSection 5.4.75, “mysql_ssl_set()”.
mysql_options() options for information such as SSL certificate and key files are used to establish an encrypted connection if such connections are available, but do not enforce any requirement that the connection obtained be encrypted. To require an encrypted connection, use the following technique:
Call
mysql_options()as necessary supply the appropriate SSL parameters (certificate and key files, encryption ciphers, and so forth).Call
mysql_options()to pass theMYSQL_OPT_SSL_MODEoption with a value ofSSL_MODE_REQUIREDor one of the more-restrictive option values.Call
mysql_real_connect()to connect to the server. The call fails if an encrypted connection cannot be obtained; exit with an error.
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, call
mysql_options()to pass theMYSQL_OPT_SSL_CA(orMYSQL_OPT_SSL_CAPATH) option, and callmysql_options()to pass theMYSQL_OPT_SSL_MODEoption with a value ofSSL_MODE_VERIFY_CA.To enable host name identity verification as well, call
mysql_options()to pass theMYSQL_OPT_SSL_MODEoption with a value ofSSL_MODE_VERIFY_IDENTITYrather thanSSL_MODE_VERIFY_CA.
Host name identity verification withSSL_MODE_VERIFY_IDENTITY does not work with self-signed certificates created automatically by the server, or manually usingmysql_ssl_rsa_setup (seeCreating SSL and RSA Certificates and Keys using MySQL). Such self-signed certificates do not contain the server name as the Common Name value.
Host name identity verification also does not work with certificates that specify the Common Name using wildcards because that name is compared verbatim to the server name.