GSSAPI Client Authenticator

GSSAPI is an authentication protocol that is commonly implemented with Kerberos on Unix or Active Directory on Windows. This document describes the GSSAPI authentication in MaxScale.

The GSSAPIAuth module implements the client side authentication and the GSSAPIBackendAuth module implements the backend authentication.

Preparing the GSSAPI system

For Unix systems, the usual GSSAPI implementation is Kerberos. This is a short guide on how to set up Kerberos for MaxScale.

The first step is to create a new principal for MaxScale. This can be done with the kadmin or kadmin.local tools.

kadmin.local -q "addprinc -nokey mariadb/"

The -nokey option will make the principal a passwordless one. This allows the maxscale user to acquire a ticket for it without a password being prompted.

The next step is to export this principal into the Kerberos keytab file.

kadmin.local -q "ktadd -k /etc/krb5.keytab -norandkey mariadb/"

This adds the mariadb/ principal into the keytab file. The -norandkey option tells that the password we defined earlier, i.e. no password at all, should be used instead of a random password.

The MariaDB documentation for the GSSAPI Authentication Plugin is a good example on how to set up a new principal for the MariaDB server.

Authenticator options

The client side GSSAPIAuth authenticator supports one option, the service principal name that MaxScale sends to the client. The backend authenticator module has no options.


The service principal name to send to the client. This parameter is a string parameter which is used by the client to request the token.

The default value for this option is mariadb/localhost.localdomain.

The parameter must be a valid GSSAPI principal name e.g. styx/pluto@EXAMPLE.COM. The principal name can also be defined without the realm part in which case the default realm will be used.

Implementation details

Read the Authentication Modules document for more details on how authentication modules work in MaxScale.

GSSAPI authentication

The GSSAPI plugin authentication starts when the database server sends the service principal name in the AuthSwitchRequest packet. The principal name will usually be in the form service@REALM.COM.

The client will then request a token for this service from the GSSAPI server and send the token to the database server. The database server will verify the authenticity of the token by contacting the GSSAPI server and if the token is authentic, the server sends the final OK packet.


Client side GSSAPI authentication is only supported when the backend connections use GSSAPI authentication.

See the Limitations document for more details.

Building the module

The GSSAPI authenticator modules require the GSSAPI and the SQLite3 development libraries (krb5-devel and sqlite-devel on CentOS 7).


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