MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
MySQL supports multiple TLS protocols and ciphers, and enables configuring which protocols and ciphers to permit for encrypted connections. It is also possible to determine which protocol and cipher the current session uses.
MySQL supports encrypted connections using the TLSv1, TLSv1.1, and TLSv1.2 protocols, listed in order from less secure to more secure. The set of protocols actually permitted for connections is subject to multiple factors:
MySQL configuration. Permitted TLS protocols can be configured on both the server side and client side to include only a subset of the supported TLS protocols. The configuration on both sides must include at least one protocol in common or connection attempts cannot negotiate a protocol to use. For details, see Connection TLS Protocol Negotiation.
System-wide host configuration. The host system may permit only certain TLS protocols, which means that MySQL connections cannot use nonpermitted protocols even if MySQL itself permits them:
Suppose that MySQL configuration permits TLSv1, TLSv1.1, and TLSv1.2, but your host system configuration permits only connections that use TLSv1.2 or higher. In this case, you cannot establish MySQL connections that use TLSv1 or TLSv1.1, even though MySQL is configured to permit them, because the host system does not permit them.
If MySQL configuration permits TLSv1, TLSv1.1, and TLSv1.2, but your host system configuration permits only connections that use TLSv1.3 or higher, you cannot establish MySQL connections at all, because no protocol permitted by MySQL is permitted by the host system.
Workarounds for this issue include:
Change the system-wide host configuration to permit
additional TLS protocols. Consult your operating system
documentation for instructions. For example, your system
may have an /etc/ssl/openssl.cnf file
that contains these lines to restrict TLS protocols to
TLSv1.2 or higher:
[system_default_sect] MinProtocol = TLSv1.2
Changing the value to a lower protocol version or
None makes the system more
permissive. This workaround has the disadvantage that
permitting lower (less secure) protocols may have
adverse security consequences.
If you cannot or prefer not to change the host system TLS configuration, change MySQL applications to use higher (more secure) TLS protocols that are permitted by the host system. This may not be possible for older versions of MySQL that support only lower protocol versions. For example, TLSv1 is the only supported protocol prior to MySQL 5.6.46, so attempts to connect to a pre-5.6.46 server fail even if the client is from a newer MySQL version that supports higher protocol versions. In such cases, an upgrade to a version of MySQL that supports additional TLS versions may be required.
The SSL library. If the SSL library does not support a particular protocol, neither does MySQL, and any parts of the following discussion that specify that protocol do not apply.
When compiled using OpenSSL 1.0.1 or higher, MySQL supports the TLSv1, TLSv1.1, and TLSv1.2 protocols.
When compiled using yaSSL, MySQL supports the TLSv1 and TLSv1.1 protocols.
It is possible to compile MySQL using yaSSL as an alternative to OpenSSL only prior to MySQL 5.7.28. As of MySQL 5.7.28, support for yaSSL is removed and all MySQL builds use OpenSSL.
On the server side, the value of the
tls_version system variable
determines which TLS protocols a MySQL server permits for
encrypted connections. The
tls_version value applies to
connections from clients and from replica servers using regular
source/replica replication. The variable value is a list of one
or more comma-separated protocol versions from this list (not
case-sensitive): TLSv1, TLSv1.1, TLSv1.2. By default, this
variable lists all protocols supported by the SSL library used
to compile MySQL (TLSv1,TLSv1.1,TLSv1.2 for
OpenSSL, TLSv1,TLSv1.1 for yaSSL). To
determine the value of
tls_version at runtime, use
this statement:
mysql> SHOW GLOBAL VARIABLES LIKE 'tls_version';
+---------------+-----------------------+
| Variable_name | Value |
+---------------+-----------------------+
| tls_version | TLSv1,TLSv1.1,TLSv1.2 |
+---------------+-----------------------+
To change the value of
tls_version, set it at server
startup. For example, to permit connections that use the TLSv1.1
or TLSv1.2 protocol, but prohibit connections that use the
less-secure TLSv1 protocol, use these lines in the server
my.cnf file:
[mysqld] tls_version=TLSv1.1,TLSv1.2
To be even more restrictive and permit only TLSv1.2 connections,
set tls_version like this
(assuming that your server is compiled using OpenSSL because
yaSSL does not support TLSv1.2):
[mysqld] tls_version=TLSv1.2
As of MySQL 5.7.35, the TLSv1 and TLSv1.1 connection protocols are deprecated and support for them is subject to removal in a future version of MySQL. See Deprecated TLS Protocols.
On the client side, the
--tls-version option specifies
which TLS protocols a client program permits for connections to
the server. The format of the option value is the same as for
the tls_version system variable
described previously (a list of one or more comma-separated
protocol versions).
For source/replica replication, the
MASTER_TLS_VERSION option for the
CHANGE MASTER TO statement
specifies which TLS protocols a replica server permits for
connections to the source. The format of the option value is the
same as for the tls_version
system variable described previously. See
Section 16.3.8, “Setting Up Replication to Use Encrypted Connections”.
The protocols that can be specified for
MASTER_TLS_VERSION depend on the SSL library.
This option is independent of and not affected by the server
tls_version value. For example,
a server that acts as a replica can be configured with
tls_version set to TLSv1.2 to
permit only incoming connections that use TLSv1.2, but also
configured with MASTER_TLS_VERSION set to
TLSv1.1 to permit only TLSv1.1 for outgoing replica connections
to the source.
TLS protocol configuration affects which protocol a given connection uses, as described in Connection TLS Protocol Negotiation.
Permitted protocols should be chosen such as not to leave “holes” in the list. For example, these server configuration values do not have holes:
tls_version=TLSv1,TLSv1.1,TLSv1.2 tls_version=TLSv1.1,TLSv1.2 tls_version=TLSv1.2
This value does have a hole and should not be used:
tls_version=TLSv1,TLSv1.2 (TLSv1.1 is missing)
The prohibition on holes also applies in other configuration contexts, such as for clients or replicas.
Unless you intend to disable encrypted connections, the list of permitted protocols should not be empty. If you set a TLS version parameter to the empty string, encrypted connections cannot be established:
tls_version: The server
does not permit encrypted incoming connections.
--tls-version: The client
does not permit encrypted outgoing connections to the
server.
MASTER_TLS_VERSION: The replica does not
permit encrypted outgoing connections to the source.
As of MySQL 5.7.35, the TLSv1 and TLSv1.1 connection protocols are deprecated and support for them is subject to removal in a future MySQL version. (For background, refer to the IETF memo Deprecating TLSv1.0 and TLSv1.1.) It is recommended that connections be made using the more-secure TLSv1.2 and TLSv1.3 protocols. TLSv1.3 requires that both the MySQL server and the client application be compiled with OpenSSL 1.1.1 or higher.
On the server side, this deprecation has the following effects:
If the tls_version system
variable is assigned a value containing a deprecated TLS
protocol during server startup, the server writes a warning
for each deprecated protocol to the error log.
If a client successfully connects using a deprecated TLS protocol, the server writes a warning to the error log.
On the client side, the deprecation has no visible effect. Clients do not issue a warning if configured to permit a deprecated TLS protocol. This includes:
Client programs that support a
--tls-version option for
specifying TLS protocols for connections to the MySQL
server.
Statements that enable replicas to specify TLS protocols for
connections to the source server.
(CHANGE MASTER TO has a
MASTER_TLS_VERSION option.)
A default set of ciphers applies to encrypted connections, which can be overridden by explicitly configuring the permitted ciphers. During connection establishment, both sides of a connection must permit some cipher in common or the connection fails. Of the permitted ciphers common to both sides, the SSL library chooses the one supported by the provided certificate that has the highest priority.
To specify a cipher or ciphers for encrypted connections, set
the ssl_cipher system variable
on the server side, and use the
--ssl-cipher option for client
programs.
For source/replica replication connections, where this server
instance is the source, set the
ssl_cipher system variable.
Where this server instance is the replica, use the
MASTER_SSL_CIPHER option for the
CHANGE MASTER TO statement. See
Section 16.3.8, “Setting Up Replication to Use Encrypted Connections”.
A given cipher may work only with particular TLS protocols, which affects the TLS protocol negotiation process. See Connection TLS Protocol Negotiation.
To determine which ciphers a given server supports, check the
session value of the
Ssl_cipher_list status
variable:
SHOW SESSION STATUS LIKE 'Ssl_cipher_list';
The Ssl_cipher_list status
variable lists the possible SSL ciphers (empty for non-SSL
connections). The set of available ciphers depends on your MySQL
version and whether MySQL was compiled using OpenSSL or yaSSL,
and (for OpenSSL) the library version used to compile MySQL.
ECDSA ciphers only work in combination with an SSL certificate that uses ECDSA for the digital signature, and they do not work with certificates that use RSA. MySQL Server’s automatic generation process for SSL certificates does not generate ECDSA signed certificates, it generates only RSA signed certificates. Do not select ECDSA ciphers unless you have an ECDSA certificate available to you.
MySQL passes a default cipher list to the SSL library.
MySQL passes this default cipher list to OpenSSL:
ECDHE-ECDSA-AES128-GCM-SHA256 ECDHE-ECDSA-AES256-GCM-SHA384 ECDHE-RSA-AES128-GCM-SHA256 ECDHE-RSA-AES256-GCM-SHA384 ECDHE-ECDSA-AES128-SHA256 ECDHE-RSA-AES128-SHA256 ECDHE-ECDSA-AES256-SHA384 ECDHE-RSA-AES256-SHA384 DHE-RSA-AES128-GCM-SHA256 DHE-DSS-AES128-GCM-SHA256 DHE-RSA-AES128-SHA256 DHE-DSS-AES128-SHA256 DHE-DSS-AES256-GCM-SHA384 DHE-RSA-AES256-SHA256 DHE-DSS-AES256-SHA256 ECDHE-RSA-AES128-SHA ECDHE-ECDSA-AES128-SHA ECDHE-RSA-AES256-SHA ECDHE-ECDSA-AES256-SHA DHE-DSS-AES128-SHA DHE-RSA-AES128-SHA TLS_DHE_DSS_WITH_AES_256_CBC_SHA DHE-RSA-AES256-SHA AES128-GCM-SHA256 DH-DSS-AES128-GCM-SHA256 ECDH-ECDSA-AES128-GCM-SHA256 AES256-GCM-SHA384 DH-DSS-AES256-GCM-SHA384 ECDH-ECDSA-AES256-GCM-SHA384 AES128-SHA256 DH-DSS-AES128-SHA256 ECDH-ECDSA-AES128-SHA256 AES256-SHA256 DH-DSS-AES256-SHA256 ECDH-ECDSA-AES256-SHA384 AES128-SHA DH-DSS-AES128-SHA ECDH-ECDSA-AES128-SHA AES256-SHA DH-DSS-AES256-SHA ECDH-ECDSA-AES256-SHA DHE-RSA-AES256-GCM-SHA384 DH-RSA-AES128-GCM-SHA256 ECDH-RSA-AES128-GCM-SHA256 DH-RSA-AES256-GCM-SHA384 ECDH-RSA-AES256-GCM-SHA384 DH-RSA-AES128-SHA256 ECDH-RSA-AES128-SHA256 DH-RSA-AES256-SHA256 ECDH-RSA-AES256-SHA384 ECDHE-RSA-AES128-SHA ECDHE-ECDSA-AES128-SHA ECDHE-RSA-AES256-SHA ECDHE-ECDSA-AES256-SHA DHE-DSS-AES128-SHA DHE-RSA-AES128-SHA TLS_DHE_DSS_WITH_AES_256_CBC_SHA DHE-RSA-AES256-SHA AES128-SHA DH-DSS-AES128-SHA ECDH-ECDSA-AES128-SHA AES256-SHA DH-DSS-AES256-SHA ECDH-ECDSA-AES256-SHA DH-RSA-AES128-SHA ECDH-RSA-AES128-SHA DH-RSA-AES256-SHA ECDH-RSA-AES256-SHA DES-CBC3-SHA
MySQL passes this default cipher list to yaSSL:
DHE-RSA-AES256-SHA DHE-RSA-AES128-SHA AES128-RMD DES-CBC3-RMD DHE-RSA-AES256-RMD DHE-RSA-AES128-RMD DHE-RSA-DES-CBC3-RMD AES256-SHA RC4-SHA RC4-MD5 DES-CBC3-SHA DES-CBC-SHA EDH-RSA-DES-CBC3-SHA EDH-RSA-DES-CBC-SHA AES128-SHA:AES256-RMD
As of MySQL 5.7.10, these cipher restrictions are in place:
The following ciphers are permanently restricted:
!DHE-DSS-DES-CBC3-SHA !DHE-RSA-DES-CBC3-SHA !ECDH-RSA-DES-CBC3-SHA !ECDH-ECDSA-DES-CBC3-SHA !ECDHE-RSA-DES-CBC3-SHA !ECDHE-ECDSA-DES-CBC3-SHA
The following categories of ciphers are permanently restricted:
!aNULL !eNULL !EXPORT !LOW !MD5 !DES !RC2 !RC4 !PSK !SSLv3
If the server is started with the
ssl_cert system variable set to
a certificate that uses any of the preceding restricted ciphers
or cipher categories, the server starts with support for
encrypted connections disabled.
Connection attempts in MySQL negotiate use of the highest TLS protocol version available on both sides for which a protocol-compatible encryption cipher is available on both sides. The negotiation process depends on factors such as the SSL library used to compile the server and client, the TLS protocol and encryption cipher configuration, and which key size is used:
For a connection attempt to succeed, the server and client TLS protocol configuration must permit some protocol in common.
Similarly, the server and client encryption cipher configuration must permit some cipher in common. A given cipher may work only with particular TLS protocols, so a protocol available to the negotiation process is not chosen unless there is also a compatible cipher.
If the server and client are compiled using OpenSSL, TLSv1.2
is used if possible. If either or both the server and client
are compiled using yaSSL, TLSv1.1 is used if possible.
(“Possible” means that server and client
configuration both must permit the indicated protocol, and
both must also permit some protocol-compatible encryption
cipher.) Otherwise, MySQL continues through the list of
available protocols, proceeding from more secure protocols
to less secure. Negotiation order is independent of the
order in which protocols are configured. For example,
negotiation order is the same regardless of whether
tls_version has a value of
TLSv1,TLSv1.1,TLSv1.2 or
TLSv1.2,TLSv1.1,TLSv1.
Prior to MySQL 5.7.10, MySQL supports only TLSv1, for both OpenSSL and yaSSL, and no system variable or client option exist for specifying which TLS protocols to permit.
TLSv1.2 does not work with all ciphers that have a key size
of 512 bits or less. To use this protocol with such a key,
set the ssl_cipher system
variable on the server side or use the
--ssl-cipher client option
to specify the cipher name explicitly:
AES128-SHA AES128-SHA256 AES256-SHA AES256-SHA256 CAMELLIA128-SHA CAMELLIA256-SHA DES-CBC3-SHA DHE-RSA-AES256-SHA RC4-MD5 RC4-SHA SEED-SHA
For better security, use a certificate with an RSA key size of at least 2048 bits.
If the server and client do not have a permitted protocol in common, and a protocol-compatible cipher in common, the server terminates the connection request. Examples:
If the server is configured with
tls_version=TLSv1.1,TLSv1.2:
Connection attempts fail for clients invoked with
--tls-version=TLSv1, and
for older clients that support only TLSv1.
Similarly, connection attempts fail for replicas
configured with MASTER_TLS_VERSION =
'TLSv1', and for older replicas that support
only TLSv1.
If the server is configured with
tls_version=TLSv1 or is an
older server that supports only TLSv1:
Connection attempts fail for clients invoked with
--tls-version=TLSv1.1,TLSv1.2.
Similarly, connection attempts fail for replicas
configured with MASTER_TLS_VERSION =
'TLSv1.1,TLSv1.2'.
MySQL permits specifying a list of protocols to support. This
list is passed directly down to the underlying SSL library and
is ultimately up to that library what protocols it actually
enables from the supplied list. Please refer to the MySQL source
code and the OpenSSL
SSL_CTX_new()
documentation for information about how the SSL library handles
this.
To determine which encryption TLS protocol and cipher the
current client session uses, check the session values of the
Ssl_version and
Ssl_cipher status variables:
mysql>SELECT * FROM performance_schema.session_statusWHERE VARIABLE_NAME IN ('Ssl_version','Ssl_cipher');+---------------+---------------------------+ | VARIABLE_NAME | VARIABLE_VALUE | +---------------+---------------------------+ | Ssl_cipher | DHE-RSA-AES128-GCM-SHA256 | | Ssl_version | TLSv1.2 | +---------------+---------------------------+
If the connection is not encrypted, both variables have an empty value.