MySQL provides two authentication plugins that implement SHA-256 hashing for user account passwords:
sha256_password: Implements basic SHA-256 authentication.
caching_sha2_password: Implements SHA-256 authentication (like
sha256_password), but uses caching on the server side for better performance and has additional features for wider applicability.
This section describes the original noncaching SHA-2 authentication plugin. For information about the caching plugin, see Section 7.1.3, “Caching SHA-2 Pluggable Authentication”.
In MySQL 8.0,
caching_sha2_password is the
default authentication plugin rather than
mysql_native_password. For information
about the implications of this change for server operation and
compatibility of the server with clients and connectors, see
caching_sha2_password as the Preferred Authentication Plugin.
caching_sha2_password is the
default authentication plugin in MySQL 8.0 and provides a
superset of the capabilities of the
sha256_password authentication plugin,
sha256_password is deprecated and will be
removed in a future MySQL version. MySQL accounts that
be migrated to use
To connect to the server using an account that authenticates
sha256_password plugin, you must
use either a TLS connection or an unencrypted connection that
supports password exchange using an RSA key pair, as described
later in this section. Either way, the
sha256_password plugin uses MySQL's
encryption capabilities. See
Chapter 6, Using Encrypted Connections.
In the name
“sha256” refers to the 256-bit digest length the
plugin uses for encryption. In the name
refers more generally to the SHA-2 class of encryption
algorithms, of which 256-bit encryption is one instance. The
latter name choice leaves room for future expansion of
possible digest lengths without changing the plugin name.
The following table shows the plugin names on the server and client sides.
Table 7.2 Plugin and Library Names for SHA-256 Authentication
|Plugin or File||Plugin or File Name|
|Library file||None (plugins are built in)|
The following sections provide installation and usage information specific to SHA-256 pluggable authentication:
For general information about pluggable authentication in MySQL, see Section 5.10, “Pluggable Authentication”.
sha256_password plugin exists in server
and client forms:
The server-side plugin is built into the server, need not be loaded explicitly, and cannot be disabled by unloading it.
The client-side plugin is built into the
libmysqlclientclient library and is available to any program linked against
To set up an account that uses the
sha256_password plugin for SHA-256 password
hashing, use the following statement, where
password is the desired account
CREATE USER 'sha256user'@'localhost' IDENTIFIED WITH sha256_password BY 'password';
The server assigns the
plugin to the account and uses it to encrypt the password
using SHA-256, storing those values in the
authentication_string columns of the
mysql.user system table.
The preceding instructions do not assume that
sha256_password is the default
authentication plugin. If
is the default authentication plugin, a simpler
CREATE USER syntax can be used.
To start the server with the default authentication plugin set
sha256_password, put these lines in the
server option file:
That causes the
sha256_password plugin to
be used by default for new accounts. As a result, it is
possible to create the account and set its password without
naming the plugin explicitly:
CREATE USER 'sha256user'@'localhost' IDENTIFIED BY 'password';
Another consequence of setting
sha256_password is that, to use some
other plugin for account creation, you must specify that
plugin explicitly. For example, to use the
mysql_native_password plugin, use this
CREATE USER 'nativeuser'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password';
sha256_password supports connections over
supports encrypted password exchange using RSA over
unencrypted connections if these conditions are satisfied:
MySQL is compiled using OpenSSL. MySQL can be compiled using either OpenSSL or yaSSL (see Section 6.4, “SSL Library-Dependent Capabilities”), and
sha256_passwordworks with distributions compiled using either package, but RSA support requires OpenSSL.
The MySQL server to which you wish to connect is configured to support RSA (using the RSA configuration procedure given later in this section).
RSA support has these characteristics:
On the server side, two system variables name the RSA private and public key-pair files:
sha256_password_public_key_path. The database administrator must set these variables at server startup if the key files to use have names that differ from the system variable default values.
The server uses the
sha256_password_auto_generate_rsa_keyssystem variable to determine whether to automatically generate the RSA key-pair files. See Section 6.3, “Creating SSL and RSA Certificates and Keys”.
Rsa_public_keystatus variable displays the RSA public key value used by the
Clients that are in possession of the RSA public key can perform RSA key pair-based password exchange with the server during the connection process, as described later.
For connections by accounts that authenticate with
sha256_passwordand RSA public key pair-based password exchange, the server sends the RSA public key to the client as needed. However, if a copy of the public key is available on the client host, the client can use it to save a round trip in the client/server protocol:
For these command-line clients, use the
--server-public-key-pathoption to specify the RSA public key file: mysql, mysqladmin, mysqlbinlog, mysqlcheck, mysqldump, mysqlimport, mysqlpump, mysqlshow, mysqlslap, mysqltest, mysql_upgrade.
For programs that use the C API, call
mysql_options()to specify the RSA public key file by passing the
MYSQL_SERVER_PUBLIC_KEYoption and the name of the file.
For replication slaves, use the
CHANGE MASTER TOstatement with the
MASTER_PUBLIC_KEY_PATHoption to specify the RSA public key file. For Group Replication, the
group_replication_recovery_get_public_keysystem variable serves the same purpose.
For clients that use the
plugin, passwords are never exposed as cleartext when
connecting to the server. How password transmission occurs
depends on whether a secure connection or RSA encryption is
If the connection is secure, an RSA key pair is unnecessary and is not used. This applies to encrypted connections that use TLS. The password is sent as cleartext but cannot be snooped because the connection is secure.
If the connection is not secure, and an RSA key pair is available, the connection remains unencrypted. This applies to unencrypted connections without TLS. RSA is used only for password exchange between client and server, to prevent password snooping. When the server receives the encrypted password, it decrypts it. A scramble is used in the encryption to prevent repeat attacks.
If a secure connection is not used and RSA encryption is not available, the connection attempt fails because the password cannot be sent without being exposed as cleartext.
As mentioned previously, RSA password encryption is available only if MySQL was compiled using OpenSSL. The implication for MySQL distributions compiled using wolfSSL is that, to use SHA-256 passwords, clients must use an encrypted connection to access the server. See Section 6.1, “Configuring MySQL to Use Encrypted Connections”.
To use RSA password encryption with
sha256_password, the client and server
both must be compiled using OpenSSL, not just one of them.
Assuming that MySQL has been compiled using OpenSSL, use the following procedure to enable use of an RSA key pair for password exchange during the client connection process:
Create the RSA private and public key-pair files using the instructions in Section 6.3, “Creating SSL and RSA Certificates and Keys”.
If the private and public key files are located in the data directory and are named
public_key.pem(the default values of the
sha256_password_public_key_pathsystem variables), the server uses them automatically at startup.
Otherwise, to name the key files explicitly, set the system variables to the key file names in the server option file. If the files are located in the server data directory, you need not specify their full path names:
[mysqld] sha256_password_private_key_path=myprivkey.pem sha256_password_public_key_path=mypubkey.pem
If the key files are not located in the data directory, or to make their locations explicit in the system variable values, use full path names:
[mysqld] sha256_password_private_key_path=/usr/local/mysql/myprivkey.pem sha256_password_public_key_path=/usr/local/mysql/mypubkey.pem
Restart the server, then connect to it and check the
Rsa_public_keystatus variable value. The value will differ from that shown here, but should be nonempty:
mysql> SHOW STATUS LIKE 'Rsa_public_key'\G *************************** 1. row *************************** Variable_name: Rsa_public_key Value: -----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDO9nRUDd+KvSZgY7cNBZMNpwX6 MvE1PbJFXO7u18nJ9lwc99Du/E7lw6CVXw7VKrXPeHbVQUzGyUNkf45Nz/ckaaJa aLgJOBCIDmNVnyU54OT/1lcs2xiyfaDMe8fCJ64ZwTnKbY2gkt1IMjUAB5Ogd5kJ g8aV7EtKwyhHb0c30QIDAQAB -----END PUBLIC KEY-----
If the value is empty, the server found some problem with the key files. Check the error log for diagnostic information.
After the server has been configured with the RSA key files,
accounts that authenticate with the
sha256_password plugin have the option of
using those key files to connect to the server. As mentioned
previously, such accounts can use either a secure connection
(in which case RSA is not used) or an unencrypted connection
that performs password exchange using RSA. Suppose that an
unencrypted connection is used. For example:
shell> mysql --ssl-mode=DISABLED -u sha256user -p Enter password: password
For this connection attempt by
the server determines that
is the appropriate authentication plugin and invokes it
(because that was the plugin specified at
CREATE USER time). The plugin
finds that the connection is not encrypted and thus requires
the password to be transmitted using RSA encryption. In this
case, the plugin sends the RSA public key to the client, which
uses it to encrypt the password and returns the result to the
server. The plugin uses the RSA private key on the server side
to decrypt the password and accepts or rejects the connection
based on whether the password is correct.
The server sends the RSA public key to the client as needed.
However, if the client has a file containing a local copy of
the RSA public key required by the server, it can specify the
file using the
shell> mysql --ssl-mode=DISABLED -u sha256user -p --server-public-key-path=file_name Enter password: password
The public key value in the file named by the
should be the same as the key value in the server-side file
named by the
system variable. If the key file contains a valid public key
value but the value is incorrect, an access-denied error
occurs. If the key file does not contain a valid public key,
the client program cannot use it. In this case, the
sha256_password plugin sends the public key
to the client as if no
had been specified.
Client users can obtain the RSA public key two ways:
The database administrator can provide a copy of the public key file.
A client user who can connect to the server some other way can use a
SHOW STATUS LIKE 'Rsa_public_key'statement and save the returned key value in a file.