/*      $NetBSD: chroot.c,v 1.19 2011/09/20 14:28:52 christos Exp $     */

/*
 * 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.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1988, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)chroot.c    8.1 (Berkeley) 6/9/93";
#else
__RCSID("$NetBSD: chroot.c,v 1.19 2011/09/20 14:28:52 christos Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>

#include <err.h>
#include <errno.h>
#include <grp.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <unistd.h>

static void     usage(void) __dead;

static int
getnum(const char *str, uintmax_t *num)
{
        char *ep;

        errno = 0;

        *num = strtoumax(str, &ep, 0);
        if (str[0] == '\0' || *ep != '\0') {
                errno = EINVAL;
                return -1;
        }

        if (errno == ERANGE && *num == UINTMAX_MAX)
                return -1;

        return 0;
}


static gid_t
getgroup(const char *group)
{
        uintmax_t       num;
        struct group    *gp;

        if ((gp = getgrnam(group)) != NULL)
                return gp->gr_gid;

        if (getnum(group, &num) == -1)
            errx(1, "no such group `%s'", group);

        return (gid_t)num;
}

static uid_t
getuser(const char *user)
{
        uintmax_t       num;
        struct passwd   *pw;

        if ((pw = getpwnam(user)) != NULL)
                return pw->pw_uid;

        if (getnum(user, &num) == -1)
                errx(1, "no such user `%s'", user);

        return (uid_t)num;
}

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

        user = NULL;
        group = NULL;
        grouplist = NULL;
        gid = 0;
        uid = 0;
        gids = 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;
                case '?':
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        if (argc < 1)
                usage();

        if (user != NULL)
                uid = getuser(user);

        if (group != NULL)
                gid = getgroup(group);

        if (grouplist != NULL) {
                while ((p = strsep(&grouplist, ",")) != NULL) {
                        if (*p == '\0')
                                continue;

                        if (gids == NGROUPS_MAX)
                                errx(1,
                                    "too many supplementary groups provided");

                        gidlist[gids++] = getgroup(p);
                }
        }

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

static void
usage(void)
{

        (void)fprintf(stderr, "Usage: %s [-G group,group,...] [-g group] "
            "[-u user] newroot [command]\n", getprogname());
        exit(1);
}