8.4.1.11 WebAuthn Pluggable Authentication

Note

WebAuthn authentication is an extension included in MySQL Enterprise Edition, a commercial product. To learn more about commercial products, see https://www.mysql.com/products/.

MySQL Enterprise Edition supports an authentication method that enables users to authenticate to MySQL Server using WebAuthn authentication.

WebAuthn stands for Web Authentication, which is a web standard published by the World Wide Web Consortium (W3C) and web application APIs that add FIDO-based authentication to supported browsers and platforms.

WebAuthn pluggable authentication replaces FIDO pluggable authentication, which is deprecated. WebAuthn pluggable authentication supports both FIDO and FIDO2 devices.

WebAuthn pluggable authentication provides these capabilities:

• WebAuthn enables authentication to MySQL Server using devices such as smart cards, security keys, and biometric readers.

• Because authentication can occur other than by providing a password, WebAuthn enables passwordless authentication.

• On the other hand, device authentication is often used in conjunction with password authentication, so WebAuthn authentication can be used to good effect for MySQL accounts that use multifactor authentication; see Section 8.2.18, “Multifactor Authentication”.

The following table shows the plugin and library file names. The file name suffix might differ on your system. Common suffixes are .so for Unix and Unix-like systems, and .dll for Windows. The file must be located in the directory named by the plugin_dir system variable. For installation information, see Installing WebAuthn Pluggable Authentication.

Table 8.28 Plugin and Library Names for WebAuthn Authentication

Plugin or File	Plugin or File Name
Server-side plugin	authentication_webauthn
Client-side plugin	authentication_webauthn_client
Library file	authentication_webauthn.so, authentication_webauthn_client.so

Note

A libfido2 library must be available on systems where either the server-side or client-side WebAuthn authentication plugin is used.

The server-side WebAuthn authentication plugin is included only in MySQL Enterprise Edition. It is not included in MySQL community distributions. The client-side plugin is included in all distributions, including community distributions, which enables clients from any distribution to connect to a server that has the server-side plugin loaded.

The following sections provide installation and usage information specific to WebAuthn pluggable authentication:

• Installing WebAuthn Pluggable Authentication

• Using WebAuthn Authentication

• WebAuthn Passwordless Authentication

• Device Unregistration for WebAuthn

• How WebAuthn Authentication of MySQL Users Works

• Cross-Version Compatibility

For general information about pluggable authentication in MySQL, see Section 8.2.17, “Pluggable Authentication”.

Installing WebAuthn Pluggable Authentication

This section describes how to install the server-side WebAuthn authentication plugin. For general information about installing plugins, see Section 7.6.1, “Installing and Uninstalling Plugins”.

To be usable by the server, the plugin library file must be located in the MySQL plugin directory (the directory named by the plugin_dir system variable). If necessary, configure the plugin directory location by setting the value of plugin_dir at server startup.

The server-side plugin library file base name is authentication_webauthn. The file name suffix differs per platform (for example, .so for Unix and Unix-like systems, .dll for Windows).

Before installing the server-side plugin, define a unique name for the relying party ID (used for device registration and authentication), which is the MySQL server. Start the server using the --loose-authentication-webauthn-rp-id=value option. The example here specifies the value mysql.com as the relying party ID. Replace this value with one that satisfies your requirements.

$> mysqld [options] --loose-authentication-webauthn-rp-id=mysql.com

Note

For replication, use the same authentication_webauthn_rp_id value on all nodes if a user is expected to connect to multiple servers.

To define the relying party and load the plugin at server startup, use the --plugin-load-add option to name the library file that contains it, adjusting the .so suffix for your platform as necessary. With this plugin-loading method, the option must be given each time the server starts.

$> mysqld [options] 
    --loose-authentication-webauthn-rp-id=mysql.com
    --plugin-load-add=authentication_webauthn.so

To define the relying party and load the plugin, put lines such as this in your my.cnf file, adjusting the .so suffix for your platform as necessary:

[mysqld]
plugin-load-add=authentication_webauthn.so
authentication_webauthn_rp_id=mysql.com

After modifying my.cnf, restart the server to cause the new setting to take effect.

Alternatively, to load the plugin at runtime, use this statement, adjusting the .so suffix for your platform as necessary:

INSTALL PLUGIN authentication_webauthn
  SONAME 'authentication_webauthn.so';

INSTALL PLUGIN loads the plugin immediately, and also registers it in the mysql.plugins system table to cause the server to load it for each subsequent normal startup without the need for --plugin-load-add.

To verify plugin installation, examine the Information Schema PLUGINS table or use the SHOW PLUGINS statement (see Section 7.6.2, “Obtaining Server Plugin Information”). For example:

mysql> SELECT PLUGIN_NAME, PLUGIN_STATUS
       FROM INFORMATION_SCHEMA.PLUGINS
       WHERE PLUGIN_NAME = 'authentication_webauthn';
+-------------------------+---------------+
| PLUGIN_NAME             | PLUGIN_STATUS |
+-------------------------+---------------+
| authentication_webauthn | ACTIVE        |
+-------------------------+---------------+

If a plugin fails to initialize, check the server error log for diagnostic messages.

To associate MySQL accounts with the WebAuthn authentication plugin, see Using WebAuthn Authentication.

Using WebAuthn Authentication

WebAuthn authentication typically is used in the context of multifactor authentication (see Section 8.2.18, “Multifactor Authentication”). This section shows how to incorporate WebAuthn device-based authentication into a multifactor account, using the authentication_webauthn plugin.

It is assumed in the following discussion that the server is running with the server-side WebAuthn authentication plugin enabled, as described in Installing WebAuthn Pluggable Authentication, and that the client-side WebAuthn plugin is available in the plugin directory on the client host.

Note

On Windows, WebAuthn authentication only functions if the client process runs as a user with administrator privileges. It might also be necessary to add the location of your FIDO/FIDO2 device to the client host's PATH environment variable.

It is also assumed that WebAuthn authentication is used in conjunction with non-WebAuthn authentication (which implies a 2FA or 3FA account). WebAuthn can also be used by itself to create 1FA accounts that authenticate in a passwordless manner. In this case, the setup process differs somewhat. For instructions, see WebAuthn Passwordless Authentication.

An account that is configured to use the authentication_webauthn plugin is associated with a Fast Identity Online (FIDO/FIDO2) device. Because of this, a one-time device registration step is required before WebAuthn authentication can occur. The device registration process has these characteristics:

• Any FIDO/FIDO2 device associated with an account must be registered before the account can be used.

• Registration requires that a FIDO/FIDO2 device be available on the client host, or registration fails.

• The user is expected to perform the appropriate FIDO/FIDO2 device action when prompted during registration (for example, touching the device or performing a biometric scan).

• To perform device registration, the client user must invoke the mysql client program and specify the --register-factor option to specify the factor or factors for which a device is being registered. For example, if the account is set to use WebAuthn as the second authentication factor, the user invokes mysql with the --register-factor=2 option.

• If the user account is configured with the authentication_webauthn plugin set as the second or third factor, authentication for all preceding factors must succeed before the registration step can proceed.

• The server knows from the information in the user account whether the FIDO/FIDO2 device requires registration or has already been registered. When the client program connects, the server places the client session in sandbox mode if the device must be registered, so that registration must occur before anything else can be done. Sandbox mode used for FIDO/FIDO2 device registration is similar to that used for handling of expired passwords. See Section 8.2.16, “Server Handling of Expired Passwords”.

• In sandbox mode, no statements other than ALTER USER are permitted. Registration is performed using forms of this statement. When invoked with the --register-factor option, the mysql client generates the ALTER USER statements required to perform registration. After registration has been accomplished, the server switches the session out of sandbox mode, and the client can proceed normally. For information about the generated ALTER USER statements, refer to the --register-factor description.

• When device registration has been performed for the account, the server updates the mysql.user system table row for that account to update the device registration status and to store the public key and credential ID. (The server does not retain the credential ID following FIDO2 device registration.)

• The registration step can be performed only by the user named by the account. If one user attempts to perform registration for another user, an error occurs.

• The user should use the same FIDO/FIDO2 device during registration and authentication. If, after registering a FIDO/FIDO2 device on the client host, the device is reset or a different device is inserted, authentication fails. In this case, the device associated with the account must be unregistered and registration must be done again.

Suppose that you want an account to authenticate first using the caching_sha2_password plugin, then using the authentication_webauthn plugin. Create a multifactor account using a statement like this:

CREATE USER 'u2'@'localhost'
  IDENTIFIED WITH caching_sha2_password
    BY 'sha2_password'
  AND IDENTIFIED WITH authentication_webauthn;

To connect, supply the factor 1 password to satisfy authentication for that factor, and to initiate registration of the FIDO/FIDO2 device, set the --register-factor to factor 2.

$> mysql --user=u2 --password1 --register-factor=2
Enter password: (enter factor 1 password)
Please insert FIDO device and follow the instruction. Depending on the device, 
you may have to perform gesture action multiple times.
1. Perform gesture action (Skip this step if you are prompted to enter device PIN).
2. Enter PIN for token device:
3. Perform gesture action for registration to complete.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8

After the factor 1 password is accepted, the client session enters sandbox mode so that device registration can be performed for factor 2. During registration, you are prompted to perform the appropriate FIDO/FIDO2 device action, such as touching the device or performing a biometric scan.

Optionally, you can invoke the mysql client program and specify the --plugin-authentication-webauthn-client-preserve-privacy option. If the FIDO2 device contains multiple discoverable credentials (resident keys) for a given replying party (RP) ID, this option permits choosing a key to be used for assertion. By default, the option is set to FALSE, indicating that assertions are to be created using all resident keys for a given RP ID. When specified with this option, mysql prompts the you for a device PIN and lists all of the available credentials for given RP ID. Select one key and then perform the remaining online instructions to complete the authentication. The example here assumes that mysql.com is a valid RP ID:

$> mysql --user=u2 --password1 --register-factor=2
     --plugin-authentication-webauthn-client-preserve-privacy
Enter password: (enter factor 1 password)
Enter PIN for token device: 
Found following credentials for RP ID: mysql.com
[1]`u2`@`127.0.0.1`
[2]`u2`@`%`
Please select one(1...N):
1
Please insert FIDO device and perform gesture action for authentication to complete.
+----------------+
| CURRENT_USER() |
+----------------+
| u2@127.0.0.1   |
+----------------+

The --plugin-authentication-webauthn-client-preserve-privacy option has no effect on FIDO devices that do not support the resident-key feature.

When the registration process is complete, the connection to the server is permitted.

Note

The connection to the server is permitted following registration regardless of additional authentication factors in the account's authentication chain. For example, if the account in the preceding example was defined with a third authentication factor (using non-WebAuthn authentication), the connection would be permitted after a successful registration without authenticating the third factor. However, subsequent connections would require authenticating all three factors.

WebAuthn Passwordless Authentication

This section describes how WebAuthn can be used by itself to create 1FA accounts that authenticate in a passwordless manner. In this context, “passwordless” means that authentication occurs but uses a method other than a password, such as a security key or biometric scan. It does not refer to an account that uses a password-based authentication plugin for which the password is empty. That kind of “passwordless” is completely insecure and is not recommended.

The following prerequisites apply when using the authentication_webauthn plugin to achieve passwordless authentication:

• The user that creates a passwordless-authentication account requires the PASSWORDLESS_USER_ADMIN privilege in addition to the CREATE USER privilege.

• The first element of the authentication_policy value must be an asterisk (*) and not a plugin name. For example, the default authentication_policy value supports enabling passwordless authentication because the first element is an asterisk:

  authentication_policy='*,,'

  For information about configuring the authentication_policy value, see Configuring the Multifactor Authentication Policy.

To use authentication_webauthn as a passwordless authentication method, the account must be created with authentication_webauthn as the first factor authentication method. The INITIAL AUTHENTICATION IDENTIFIED BY clause must also be specified for the first factor (it is not supported with 2nd or 3rd factors). This clause specifies whether a randomly generated or user-specified password will be used for FIDO/FIDO2 device registration. After device registration, the server deletes the password and modifies the account to make authentication_webauthn the sole authentication method (the 1FA method).

The required CREATE USER syntax is as follows:

CREATE USER user
  IDENTIFIED WITH authentication_webauthn
  INITIAL AUTHENTICATION IDENTIFIED BY {RANDOM PASSWORD | 'auth_string'};

The following example uses the RANDOM PASSWORD syntax:

mysql> CREATE USER 'u1'@'localhost'
         IDENTIFIED WITH authentication_webauthn
         INITIAL AUTHENTICATION IDENTIFIED BY RANDOM PASSWORD;
+------+-----------+----------------------+-------------+
| user | host      | generated password   | auth_factor |
+------+-----------+----------------------+-------------+
| u1   | localhost | 9XHK]M{l2rnD;VXyHzeF |           1 |
+------+-----------+----------------------+-------------+

To perform registration, the user must authenticate to the server with the password associated with the INITIAL AUTHENTICATION IDENTIFIED BY clause, either the randomly generated password, or the 'auth_string' value. If the account was created as just shown, the user executes this command and pastes in the preceding randomly generated password (9XHK]M{l2rnD;VXyHzeF) at the prompt:

$> mysql --user=u1 --password --register-factor=2
Enter password:
Please insert FIDO device and follow the instruction. Depending on the device, 
you may have to perform gesture action multiple times.
1. Perform gesture action (Skip this step if you are prompted to enter device PIN).
2. Enter PIN for token device:
3. Perform gesture action for registration to complete.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10

Alternatively, use the --plugin-authentication-webauthn-client-preserve-privacy option to select a discoverable credential for authentication.

$> mysql --user=u1 --password --register-factor=2
     --plugin-authentication-webauthn-client-preserve-privacy
Enter password:
Enter PIN for token device: 
Found following credentials for RP ID: mysql.com
[1]`u1`@`127.0.0.1`
[2]`u1`@`%`
Please select one(1...N):
1
Please insert FIDO device and perform gesture action for authentication to complete.
+----------------+
| CURRENT_USER() |
+----------------+
| u1@127.0.0.1   |
+----------------+

The option --register-factor=2 is used because the INITIAL AUTHENTICATION IDENTIFIED BY clause is currently acting as the first factor authentication method. The user must therefore provide the temporary password by using the second factor. On a successful registration, the server removes the temporary password and revises the account entry in the mysql.user system table to list authentication_webauthn as the sole (1FA) authentication method.

When creating a passwordless-authentication account, it is important to include the INITIAL AUTHENTICATION IDENTIFIED BY clause in the CREATE USER statement. The server accepts a statement without the clause, but the resulting account is unusable because there is no way to connect to the server to register the device. Suppose that you execute a statement like this:

CREATE USER 'u2'@'localhost'
  IDENTIFIED WITH authentication_webauthn;

Subsequent attempts to use the account to connect fail like this:

$> mysql --user=u2 --skip-password
mysql: [Warning] Using a password on the command line can be insecure.
No FIDO device on client host.
ERROR 1 (HY000): Unknown MySQL error

Note

Passwordless authentication is achieved using the Universal 2nd Factor (U2F) protocol, which does not support additional security measures such as setting a PIN on the device to be registered. It is therefore the responsibility of the device holder to ensure the device is handled in a secure manner.

Device Unregistration for WebAuthn

It is possible to unregister FIDO/FIDO2 devices associated with a MySQL account. This might be desirable or necessary under multiple circumstances:

• A FIDO/FIDO2 device is to be replaced with a different device. The previous device must be unregistered and the new device registered.

  In this case, the account owner or any user who has the CREATE USER privilege can unregister the device. The account owner can register the new device.

• A FIDO/FIDO2 device is reset or lost. Authentication attempts will fail until the current device is unregistered and a new registration is performed.

  In this case, the account owner, being unable to authenticate, cannot unregister the current device and must contact the DBA (or any user who has the CREATE USER privilege) to do so. Then the account owner can reregister the reset device or register a new device.

Unregistering a FIDO/FIDO2 device can be done by the account owner or by any user who has the CREATE USER privilege. Use this syntax:

ALTER USER user {2 | 3} FACTOR UNREGISTER;

To re-register a device or perform a new registration, refer to the instructions in Using WebAuthn Authentication.

How WebAuthn Authentication of MySQL Users Works

This section provides an overview of how MySQL and WebAuthn work together to authenticate MySQL users. For examples showing how to set up MySQL accounts to use the WebAuthn authentication plugins, see Using WebAuthn Authentication.

An account that uses WebAuthn authentication must perform an initial device registration step before it can connect to the server. After the device has been registered, authentication can proceed. WebAuthn device registration process is as follows:

1. The server sends a random challenge, user ID, and relying party ID (which uniquely identifies a server) to the client in JSON format. The relying party ID is defined by the authentication_webauthn_rp_id system variable. The default value is mysql.com.

2. The client receives that information and sends it to the client-side WebAuthn authentication plugin, which in turn provides it to the FIDO/FIDO2 device. Client also sends 1-byte capability, with RESIDENT_KEYS bit set to ON (if it is FIDO2 device) or OFF.

3. After the user has performed the appropriate device action (for example, touching the device or performing a biometric scan) the FIDO/FIDO2 device generates a public/private key pair, a key handle, an X.509 certificate, and a signature, which is returned to the server.

4. The server-side WebAuthn authentication plugin verifies the signature. With successful verification, the server stores the credential ID (for FIDO devices only) and public key in the mysql.user system table.

After registration has been performed successfully, WebAuthn authentication follows this process:

1. The server sends a random challenge, user ID, relying party ID and credentials to the client. The challenge is converted to URL-safe Base64 format.

2. The client sends the same information to the device. The client queries the device to check if it supports Client-to-Authenticator Protocols (CTAP2) protocol. CTAP2 support indicates that the device is FIDO2-protocol aware.

3. The FIDO/FIDO2 device prompts the user to perform the appropriate device action, based on the selection made during registration.

   If the device is FIDO2-protocol aware, the device signs with all private keys available in the device for a given RP ID. Optionally, it may prompt user to pick one from the list as well. If the device is not FIDO2 capable, it fetches the right private key.

4. This action unlocks the private key and the challenge is signed.

5. This signed challenge is returned to the server.

6. The server-side WebAuthn authentication plugin verifies the signature with the public key and responds to indicate authentication success or failure.

Cross-Version Compatibility

WebAuthn pluggable authentication supports both FIDO and FIDO2 devices. Cross-version compatibility occurs during device registration as follows:

• An older version of mysql client can initiate registration for a user that uses the authentication_fido plugin against the latest version of the server.

• The latest version of mysql client can initiate registration for a user that uses the authentication_fido plugin against an older version of the server. In such a case, the server signals to the client that authentication_fido_client should be used for registration.