ALTER USER

MariaDB starting with 10.2.0

The ALTER USER statement was introduced in MariaDB 10.2.0.

Syntax

ALTER USER [IF EXISTS] 
 user_specification [,user_specification] ...
  [REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
  [WITH resource_option [resource_option] ...]

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_plugin
  | IDENTIFIED {VIA|WITH} authentication_plugin {USING|AS} 'authentication_string'
  | IDENTIFIED {VIA|WITH} authentication_plugin {USING|AS} PASSWORD('password')

tls_option
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

resource_option
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

Description

The ALTER USER statement modifies existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. The global SUPER privilege is also required if the read_only system variable is enabled.

If any of the specified user accounts do not yet exist, an error results. If an error occurs, ALTER USER will still modify the accounts that do not result in an error. Only one error is produced for all users which have not been modified.

IF EXISTS

When the IF EXISTS clause is used, MariaDB will return a warning instead of an error for each specified user that does not exist.

Account Names

For ALTER USER statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified.

CURRENT_USER or CURRENT_USER() can also be used to alter the account logged into the current session. For example, to change the current user's password to mariadb:

ALTER USER CURRENT_USER() IDENTIFIED BY 'mariadb';

Authentication Options

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table.

For example, if our password is mariadb, then we can set the account's password with:

ALTER USER foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored to the mysql.user table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)

And then we can set an account's password with the hash:

ALTER USER foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

ALTER USER foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

ALTER USER foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

In MariaDB 10.4 and later, the USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

ALTER USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');

TLS Options

By default, MariaDB uses unencrypted connections for all client/server communications. In order to use encrypted connections, OpenSSL or yaSSL must be present in your system. Also, the MariaDB server needs to be built with TLS support and be properly configured to use one of them. See Secure Connections Overview for more information about that.

TLS is the modern term to describe the encryption protocol. SSL refers to the old, now insecure, protocol that preceded TLS. Many of the variable names and options still refer to SSL, rather than TLS, for compatibility reasons. However, MariaDB only uses its more secure successors.

You can require TLS connections on a per-account basis, using the REQUIRE clause. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required.
REQUIRE X509The account must use TLS and must have a valid X509 certificate.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject.
REQUIRE CIPHER 'cipher'The account must use TLS and must have a valid X509 certificate. Also, the encryption used for the connection must use one of the methods specified in the string cipher.

If you set REQUIRE X509, then REQUIRE SSL is implicitly set. The ISSUER, SUBJECT, and CIPHER options can be set together in any order, and if you set any of them, then REQUIRE X509 is also implicitly set.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

If any of these options are set for a specific user, then any client who tries to connect with that user will have to be configured to connect with TLS. For example, the mysql client can be configured to do so by setting options like --ssl, --ssl-ca, --ssl-cert, --ssl-cipher, --ssl-key, and --ssl-verify-server-cert.

For example, you can set an account's TLS options with the following:

ALTER USER 'someone'@'localhost'
    REQUIRE SUBJECT '/CN=www.mydom.com/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

Here is an example showing how to set an account's resource limits:

ALTER USER 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 10
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

See Also

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