/*
 * 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 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * Copyright (c) 2013 RackTop Systems.
 */

#include <errno.h>
#include <sys/types.h>
#include <stdio.h>
#include <userdefs.h>
#include <grp.h>
#include <libcmdutils.h>

static int findunusedgid(gid_t start, gid_t stop, gid_t *ret);
static boolean_t isreservedgid(gid_t gid);

/*
 * Find the highest unused uid. If the highest unused gid is "stop",
 * then attempt to find a hole in the range. Returns 0 on success.
 */
int
findnextgid(gid_t start, gid_t stop, gid_t *ret)
{
        gid_t gid = start;
        struct group *grp;
        boolean_t overflow = B_FALSE;

        setgrent();
        for (grp = getgrent(); grp != NULL; grp = getgrent()) {
                if (isreservedgid(grp->gr_gid))         /* Skip reserved IDs */
                        continue;
                if (grp->gr_gid >= gid) {
                        if (grp->gr_gid == stop) {      /* Overflow check */
                                overflow = B_TRUE;
                                break;
                        }
                        gid = grp->gr_gid + 1;
                }
        }
        if (grp == NULL && errno != 0) {
                endgrent();
                return (-1);
        }
        endgrent();
        if (overflow == B_TRUE)                         /* Find a hole */
                return (findunusedgid(start, stop, ret));
        while (isreservedgid(gid) && gid < stop)        /* Skip reserved IDs */
                gid++;
        *ret = gid;
        return (0);
}

/*
 * Check to see whether the gid is a reserved gid
 * -- nobody, noaccess or nogroup
 */
static boolean_t
isreservedgid(gid_t gid)
{
        return (gid == 60001 || gid == 60002 || gid == 65534);
}

/*
 * findunusedgid() attempts to return the next valid usable id between the
 * supplied upper and lower limits. Returns 0 on success.
 */
static int
findunusedgid(gid_t start, gid_t stop, gid_t *ret)
{
        gid_t gid;

        for (gid = start; gid <= stop; gid++) {
                if (isreservedgid(gid))
                        continue;
                if (getgrgid(gid) == NULL) {
                        if (errno != 0)
                                return (-1);
                        break;
                }
        }
        if (gid > stop)
                return (-1);
        *ret = gid;
        return (0);
}