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Luke Howard 62c1790bf5 kadm5: pre/post-commit plugin hook for kadm5 update operations (#397 )

This change adds plugin support to the kadmin libraries for performing
actions before and after a password change is committed to the KDC database
and after a change is made to the attributes of a principal (specifically,
a change to DISALLOW_ALL_TIX).

This change adds a hook_libraries configuration option to the [kadmin]
section of krb5.conf (or kdc.conf if you use that file) that must be set
to load the module. That configuration option is in the form:

[kadmin]
  hook_libraries = /usr/local/lib/krb5/plugins/kadm5_hook/krb5_sync.so

where the value is the full path to the plugin that you want to load. If
this option is not present, kadmind will not load a plugin and the changes
from the patch will be inactive. If this option is given and the plugin
cannot be loaded, kadmind startup will abort with a (hopefully useful)
error message in syslog.

Any plugin used with this patch must expose a public function named
kadm5_hook_init of type kadm5_hook_init_t that returns a kadm5_hook structure.
See sample_hook.c for an example of this initialization function.

typedef struct kadm5_hook {
    const char *name;
    uint32_t version;
    const char *vendor;
    void (KRB5_CALLCONV *fini)(krb5_context, void *data);

    krb5_error_code (KRB5_CALLCONV *chpass)(krb5_context context,
					    void *data,
					    enum kadm5_hook_stage stage,
                                            krb5_error_code code,
                                            krb5_const_principal princ,
                                            uint32_t flags,
                                            size_t n_ks_tuple,
                                            krb5_key_salt_tuple *ks_tuple,
                                            const char *password,
                                            char **error_msg);
    ...
};

where enum kadm5_hook_stage is:

enum kadm5_hook_stage {
    KADM5_HOOK_STAGE_PRECOMMIT,
    KADM5_HOOK_STAGE_POSTCOMMIT
};

init creates a hook context that is passed into all subsequent calls.
chpass is called for password changes, create is called for principal
creation (with the newly-created principal in the kadm5_principal_ent_t
argument), and modify is called when a principal is modified. The purpose of
the remaining functions should be self-explanatory.

returning 0 on success and a Kerberos error code on failure, setting the
Kerberos error message in the provided context. The error code passed in is
valid for post-commit hooks and contains the result of the update operation.

This change is submitted under the following license

Copyright 2012, 2013
The Board of Trustees of the Leland Stanford Junior University

Portions Copyright 2018 AuriStor Inc.

Copying and distribution of this file, with or without modification, are
permitted in any medium without royalty provided the copyright notice and
this notice are preserved. This file is offered as-is, without any
warranty.

2018-12-26 11:04:05 -06:00