/*
 * Copyright (c) 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * @(#) Copyright (c) 1988, 1993 The Regents of the University of California.  All rights reserved.
 * @(#)chroot.c 8.1 (Berkeley) 6/9/93
 * $FreeBSD: src/usr.sbin/chroot/chroot.c,v 1.4.2.1 2002/03/15 22:54:59 mikeh Exp $
 * $DragonFly: src/usr.sbin/chroot/chroot.c,v 1.9 2004/12/22 08:59:33 dillon Exp $
 */

#include <sys/types.h>

#include <ctype.h>
#include <err.h>
#include <grp.h>
#include <limits.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void usage(void);

int
main(int argc, char **argv)
{
        struct group    *gp;
        struct passwd   *pw;
        char            *endp, *p;
        const char      *shell;
        const char      *user;          /* user to switch to before running program */
        const char      *group;         /* group to switch to ... */
        char            *grouplist;     /* group list to switch to ... */
        gid_t           gid, gidlist[NGROUPS_MAX];
        uid_t           uid;
        int             ch, gids;

        user = NULL;
        group = NULL;
        grouplist = NULL;

        gid = 0;
        uid = 0;
        while ((ch = getopt(argc, argv, "G:g:u:")) != -1) {
                switch(ch) {
                case 'u':
                        user = optarg;
                        if (*user == '\0')
                                usage();
                        break;
                case 'g':
                        group = optarg;
                        if (*group == '\0')
                                usage();
                        break;
                case 'G':
                        grouplist = optarg;
                        if (*grouplist == '\0')
                                usage();
                        break;
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        if (argc < 1)
                usage();

        if (group != NULL) {
                if (isdigit(*group)) {
                        gid = (gid_t)strtoul(group, &endp, 0);
                        if (*endp != '\0')
                                goto getgroup;
                } else {
 getgroup:
                        if ((gp = getgrnam(group)) != NULL)
                                gid = gp->gr_gid;
                        else
                                errx(1, "no such group `%s'", group);
                }
        }

        for (gids = 0;
            (p = strsep(&grouplist, ",")) != NULL && gids < NGROUPS_MAX; ) {
                if (*p == '\0')
                        continue;

                if (isdigit(*p)) {
                        gidlist[gids] = (gid_t)strtoul(p, &endp, 0);
                        if (*endp != '\0')
                                goto getglist;
                } else {
 getglist:
                        if ((gp = getgrnam(p)) != NULL)
                                gidlist[gids] = gp->gr_gid;
                        else
                                errx(1, "no such group `%s'", p);
                }
                gids++;
        }
        if (p != NULL && gids == NGROUPS_MAX)
                errx(1, "too many supplementary groups provided");

        if (user != NULL) {
                if (isdigit(*user)) {
                        uid = (uid_t)strtoul(user, &endp, 0);
                        if (*endp != '\0')
                                goto getuser;
                } else {
 getuser:
                        if ((pw = getpwnam(user)) != NULL)
                                uid = pw->pw_uid;
                        else
                                errx(1, "no such user `%s'", user);
                }
        }

        if (chdir(argv[0]) == -1 || chroot(".") == -1)
                err(1, "%s", argv[0]);

        if (gids && setgroups(gids, gidlist) == -1)
                err(1, "setgroups");
        if (group && setgid(gid) == -1)
                err(1, "setgid");
        if (user && setuid(uid) == -1)
                err(1, "setuid");

        if (argv[1]) {
                execvp(argv[1], &argv[1]);
                err(1, "%s", argv[1]);
        }

        if (!(shell = getenv("SHELL")))
                shell = _PATH_BSHELL;
        execlp(shell, shell, "-i", NULL);
        err(1, "%s", shell);
        /* NOTREACHED */
}

static void
usage(void)
{
        fprintf(stderr, "usage: chroot [-g group] [-G group,group,...] "
            "[-u user] newroot [command]\n");
        exit(1);
}