MySQL 8.0 Reference Manual
MySQL 8.0 Release Notes
Authentication involves one party establishing its identity to the satisfaction of a second party. Multifactor authentication (MFA) is the use of multiple authentication values (or “factors”) during the authentication process. MFA provides greater security than one-factor/single-factor authentication (1FA/SFA), which uses only one authentication method such as a password. MFA enables additional authentication methods, such as authentication using multiple passwords, or authentication using devices like smart cards, security keys, and biometric readers.
MySQL 8.0.27 and higher includes support for multifactor authentication. This capability includes forms of MFA that require up to three authentication values. That is, MySQL account management supports accounts that use 2FA or 3FA, in addition to the existing 1FA support.
When a client attempts a connection to the MySQL server using a single-factor account, the server invokes the authentication plugin indicated by the account definition and accepts or rejects the connection depending on whether the plugin reports success or failure.
For an account that has multiple authentication factors, the process is similar. The server invokes authentication plugins in the order listed in the account definition. If a plugin reports success, the server either accepts the connection if the plugin is the last one, or proceeds to invoke the next plugin if any remain. If any plugin reports failure, the server rejects the connection.
The following sections cover multifactor authentication in MySQL in more detail.
Authentication factors commonly include these types of information:
Something you know, such as a secret password or passphrase.
Something you have, such as a security key or smart card.
Something you are; that is, a biometric characteristic such as a fingerprint or facial scan.
The “something you know” factor type relies on information that is kept secret on both sides of the authentication process. Unfortunately, secrets may be subject to compromise: Someone might see you enter your password or fool you with a phishing attack, a password stored on the server side might be exposed by a security breach, and so forth. Security can be improved by using multiple passwords, but each may still be subject to compromise. Use of the other factor types enables improved security with less risk of compromise.
Implementation of multifactor authentication in MySQL comprises these elements:
The
authentication_policysystem variable controls how many authentication factors can be used and the types of authentication permitted for each factor. That is, it places constraints onCREATE USERandALTER USERstatements with respect to multifactor authentication.CREATE USERandALTER USERhave syntax enabling multiple authentication methods to be specified for new accounts, and for adding, modifying, or dropping authentication methods for existing accounts. If an account uses 2FA or 3FA, themysql.usersystem table stores information about the additional authentication factors in theUser_attributescolumn.To enable authentication to the MySQL server using accounts that require multiple passwords, client programs have
--password1,--password2, and--password3options that permit up to three passwords to be specified. For applications that use the C API, theMYSQL_OPT_USER_PASSWORDoption for themysql_options4()C API function enables the same capability.The server-side
authentication_fidoplugin (deprecated) enables authentication using devices. This server-side FIDO authentication plugin is included only in MySQL Enterprise Edition distributions. It is not included in MySQL community distributions. However, the client-sideauthentication_fido_clientplugin (deprecated) is included in all distributions, including community distributions. This enables clients from any distribution to connect to accounts that useauthentication_fidoto authenticate on a server that has that plugin loaded. See Section 6.1.11, “FIDO Pluggable Authentication”.authentication_fidoalso enables passwordless authentication, if it is the only authentication plugin used by an account. See FIDO Passwordless Authentication.Multifactor authentication can use non-FIDO MySQL authentication methods, the FIDO authentication method, or a combination of both.
These privileges enable users to perform certain restricted multifactor authentication-related operations:
A user who has the
AUTHENTICATION_POLICY_ADMINprivilege is not subject to the constraints imposed by theauthentication_policysystem variable. (A warning does occur for statements that otherwise would not be permitted.)The
PASSWORDLESS_USER_ADMINprivilege enables creation of passwordless-authentication accounts and replication of operations on them.
The authentication_policy
system variable defines the multifactor authentication policy.
Specifically, it defines how many authentication factors
accounts may have (or are required to have) and the
authentication methods that can be used for each factor.
The value of
authentication_policy is a list
of 1, 2, or 3 comma-separated elements. Each element in the list
corresponds to an authentication factor and can be an
authentication plugin name, an asterisk (*),
empty, or missing. (Exception: Element 1 cannot be empty or
missing.) The entire list is enclosed in single quotes. For
example, the following
authentication_policy value
includes an asterisk, an authentication plugin name, and an
empty element:
authentication_policy = '*,authentication_fido,'
An asterisk (*) indicates that an
authentication method is required but any method is permitted.
An empty element indicates that an authentication method is
optional and any method is permitted. A missing element (no
asterisk, empty element, or authentication plugin name)
indicates that an authentication method is not permitted. When a
plugin name is specified, that authentication method is required
for the respective factor when creating or modifying an account.
The default
authentication_policy value is
'*,,' (an asterisk and two empty elements),
which requires a first factor, and optionally permits second and
third factors. The default
authentication_policy value is
thus backward compatible with existing 1FA accounts, but also
permits creation or modification of accounts to use 2FA or 3FA.
A user who has the
AUTHENTICATION_POLICY_ADMIN
privilege is not subject to the constraints imposed by the
authentication_policy setting.
(A warning occurs for statements that otherwise would not be
permitted.)
authentication_policy values
can be defined in an option file or specified using a
SET
GLOBAL statement:
SET GLOBAL authentication_policy='*,*,';
There are several rules that govern how the
authentication_policy value can
be defined. Refer to the
authentication_policy system
variable description for a compete account of those rules. The
following table provides several
authentication_policy example
values and the policy established by each.
Table 4.10 Example authentication_policy Values
| authentication_policy Value | Effective Policy |
|---|---|
'*' |
Permit only creating or altering accounts with one factor. |
'*,*' |
Permit only creating or altering accounts with two factors. |
'*,*,*' |
Permit only creating or altering accounts with three factors. |
'*,' |
Permit creating or altering accounts with one or two factors. |
'*,,' |
Permit creating or altering accounts with one, two, or three factors. |
'*,*,' |
Permit creating or altering accounts with two or three factors. |
'*, |
Permit creating or altering accounts with two factors, where the first factor can be any authentication method, and the second factor must be the named plugin. |
' |
Permit creating or altering accounts with two or three factors, where the first factor must be the named plugin. |
' |
Permit creating or altering accounts with one or two factors, where the first factor must be the named plugin. |
' |
Permits creating or altering accounts with three factors, where the factors must use the named plugins. |
By default, MySQL uses a multifactor authentication policy that permits any authentication plugin for the first factor, and optionally permits second and third authentication factors. This policy is configurable; for details, see Configuring the Multifactor Authentication Policy.
Note
It is not permitted to use any internal credential storage
plugins (caching_sha2_password or
mysql_native_password) for factor 2 or 3.
Suppose that you want an account to authenticate first using the
caching_sha2_password plugin, then using the
authentication_ldap_sasl SASL LDAP plugin.
(This assumes that LDAP authentication is already set up as
described in Section 6.1.7, “LDAP Pluggable Authentication”,
and that the user has an entry in the LDAP directory
corresponding to the authentication string shown in the
example.) Create the account using a statement like this:
CREATE USER 'alice'@'localhost'
IDENTIFIED WITH caching_sha2_password
BY 'sha2_password'
AND IDENTIFIED WITH authentication_ldap_sasl
AS 'uid=u1_ldap,ou=People,dc=example,dc=com';
To connect, the user must supply two passwords. To enable
authentication to the MySQL server using accounts that require
multiple passwords, client programs have
--password1,
--password2, and
--password3 options that permit
up to three passwords to be specified. These options are similar
to the --password option in that
they can take a password value following the option on the
command line (which is insecure) or if given without a password
value cause the user to be prompted for one. For the account
just created, factors 1 and 2 take passwords, so invoke the
mysql client with the
--password1 and
--password2 options.
mysql prompts for each password in turn:
$> mysql --user=alice --password1 --password2
Enter password: (enter factor 1 password)
Enter password: (enter factor 2 password)
Suppose you want to add a third authentication factor. This can
be achieved by dropping and recreating the user with a third
factor or by using
ALTER USER
syntax. Both methods
are shown below:
user ADD
factor
DROP USER 'alice'@'localhost';
CREATE USER 'alice'@'localhost'
IDENTIFIED WITH caching_sha2_password
BY 'sha2_password'
AND IDENTIFIED WITH authentication_ldap_sasl
AS 'uid=u1_ldap,ou=People,dc=example,dc=com'
AND IDENTIFIED WITH authentication_fido;
ADD syntax
includes the factor number and factorFACTOR
keyword:
ALTER USER 'alice'@'localhost' ADD 3 FACTOR IDENTIFIED WITH authentication_fido;
ALTER USER
syntax permits
dropping a factor. The following example drops the third factor
(user DROP
factorauthentication_fido) that was added in the
previous example:
ALTER USER 'alice'@'localhost' DROP 3 FACTOR;
ALTER USER
syntax permits
changing the plugin or authentication string for a particular
factor, provided that the factor exists. The following example
modifies the second factor, changing the authentication method
from user MODIFY
factorauthentication_ldap_sasl to
authetication_fido:
ALTER USER 'alice'@'localhost' MODIFY 2 FACTOR IDENTIFIED WITH authentication_fido;
Use SHOW CREATE USER to view the
authentication methods defined for an account:
SHOW CREATE USER 'u1'@'localhost'\G
*************************** 1. row ***************************
CREATE USER for u1@localhost: CREATE USER `u1`@`localhost`
IDENTIFIED WITH 'caching_sha2_password' AS 'sha2_password'
AND IDENTIFIED WITH 'authentication_fido' REQUIRE NONE
PASSWORD EXPIRE DEFAULT ACCOUNT UNLOCK PASSWORD HISTORY
DEFAULT PASSWORD REUSE INTERVAL DEFAULT PASSWORD REQUIRE
CURRENT DEFAULT