# MIT Kerberos Documentation

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# PKINIT certificate authorization interface (certauth)

The certauth interface was first introduced in release 1.16. It allows customization of the X.509 certificate attribute requirements placed on certificates used by PKINIT enabled clients. For a detailed description of the certauth interface, see the header file `<krb5/certauth_plugin.h>`

A certauth module implements the authorize method to determine whether a client’s certificate is authorized to authenticate a client principal. authorize receives the DER-encoded certificate, the requested client principal, and a pointer to the client’s krb5_db_entry (for modules that link against libkdb5). The method must decode the certificate and inspect its attributes to determine if it should authorize PKINIT authentication. It returns the authorization status and optionally outputs a list of authentication indicator strings to be added to the ticket.

Beginning in release 1.19, the authorize method can request that the hardware authentication bit be set in the ticket by returning KRB5_CERTAUTH_HWAUTH. Beginning in release 1.20, the authorize method can return KRB5_CERTAUTH_HWAUTH_PASS to request that the hardware authentication bit be set in the ticket but otherwise defer authorization to another certauth module. A module must use its own internal or library-provided ASN.1 certificate decoder.

A module can optionally create and destroy module data with the init and fini methods. Module data objects last for the lifetime of the KDC process.

If a module allocates and returns a list of authentication indicators from authorize, it must also implement the free_ind method to free the list.