/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright 2019 by Western Digital Corporation
 */

/*
 * au_preselect.c
 */

#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <bsm/audit.h>
#include <bsm/libbsm.h>
#include <synch.h>

#define	ALLOC_INIT (600)	/* initially allocate ALLOC_INIT map entries */
#define	ALLOC_INCR (100)	/* if more map entries are needed, realloc */
				/* in ALLOC_INCR increments */

static int alloc_map();
static int load_map();
static int realloc_map();

typedef struct event_map {
	au_event_t event;	/* audit event number */
	au_class_t class;	/* audit event class mask */
} event_map_t;

static event_map_t *event_map;	/* the map */
static uint_t alloc_count;	/* number of entries currently allocated */
static uint_t event_count;	/* number of entries in map */
static mutex_t mutex_au_preselect = DEFAULTMUTEX;

/*
 * au_preselect:
 *
 * Keep a dynamic array of event<-->class mappings.
 * Refresh the map when the value of flag is AU_PRS_REREAD.
 * Return:
 *	1: The event is preselected.
 *	0: The event is not preselected.
 *	-1: There was an error:
 *		Couldn't allocate memory.
 *		Couldn't find event.
 */
int
au_preselect(au_event_t au_event, au_mask_t *au_mask_p, int sorf, int flag)
{
	static char been_here_before;  /* we cache the map */
	register int i;
	register au_class_t comp_class;

	(void) mutex_lock(&mutex_au_preselect);
	if (!been_here_before) {
		if (alloc_map() == -1) {
			(void) mutex_unlock(&mutex_au_preselect);
			return (-1);
		}

		if (load_map() == -1) {
			(void) mutex_unlock(&mutex_au_preselect);
			return (-1);
		}

		been_here_before = 1;
	}

	/*
	 * Don't use the cache. Re-read the audit_event(5) db every time
	 */
	if (flag == AU_PRS_REREAD) {
		if (load_map() == -1) {
			(void) mutex_unlock(&mutex_au_preselect);
			return (-1);
		}
	}

	/* Determine what portion of the preselection mask to check. */
	if (sorf == AU_PRS_SUCCESS)
		comp_class = au_mask_p->am_success;
	else if (sorf == AU_PRS_FAILURE)
		comp_class = au_mask_p->am_failure;
	else
		comp_class = au_mask_p->am_success | au_mask_p->am_failure;

	for (i = 0; i < event_count; i++) {
		if (event_map[i].event == au_event) {
			if (event_map[i].class & comp_class) {
				(void) mutex_unlock(&mutex_au_preselect);
				return (1);
			} else {
				(void) mutex_unlock(&mutex_au_preselect);
				return (0);
			}
		}
	}

	(void) mutex_unlock(&mutex_au_preselect);
	return (-1);	/* could not find event in the table */
}

/*
 * Initially allocate about as many map entries as are there
 * are audit events shipped with the system. For sites
 * that don't add audit events, this should be enough.
 */
static int
alloc_map()
{
	if ((event_map = (event_map_t *)
	    calloc(ALLOC_INIT, (size_t)sizeof (event_map_t))) ==
	    (event_map_t *)NULL)
		return (-1);
	else
		alloc_count = ALLOC_INIT;

	return (0);
}

/*
 * load the event<->class map into memory
 */
static int
load_map()
{
	register au_event_ent_t *evp;

	event_count = 0;
	setauevent();
	while ((evp = getauevent()) != (au_event_ent_t *)NULL) {
		if (event_count == alloc_count && realloc_map() == -1) {
			endauevent();
			return (-1);
		}
		event_map[event_count].event = evp->ae_number;
		event_map[event_count].class = evp->ae_class;
		++event_count;
	}
	endauevent();

	return (0);
}

/*
 * realloc the event map in ALLOC_INCR increments
 */
static int
realloc_map()
{
	uint_t new_alloc_count;
	event_map_t *new_event_map;

	new_alloc_count = alloc_count + ALLOC_INCR;
	if (new_alloc_count <= alloc_count) {
		errno = ENOMEM;
		return (-1);
	}

	if ((new_event_map = recallocarray(event_map, alloc_count,
	    new_alloc_count, sizeof (event_map_t))) == NULL)
		return (-1);

	alloc_count = new_alloc_count;
	event_map = new_event_map;

	return (0);
}