This builds on recently introduced NO_NEW_PRIVS flag to implement unprivileged chroot, enabled by `security.bsd.unprivileged_chroot`. It allows non-root processes to chroot(2), provided they have the NO_NEW_PRIVS flag set. The chroot(8) utility gets a new flag, -n, which sets NO_NEW_PRIVS before chrooting. Reviewed By: kib Sponsored By: EPSRC Relnotes: yes Differential Revision: https://reviews.freebsd.org/D30130
199 lines
4.9 KiB
C
199 lines
4.9 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1988, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if 0
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#ifndef lint
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static const char copyright[] =
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"@(#) Copyright (c) 1988, 1993\n\
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The Regents of the University of California. All rights reserved.\n";
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#endif /* not lint */
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#ifndef lint
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static char sccsid[] = "@(#)chroot.c 8.1 (Berkeley) 6/9/93";
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#endif /* not lint */
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#endif
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/procctl.h>
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#include <ctype.h>
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#include <err.h>
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#include <grp.h>
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#include <limits.h>
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#include <paths.h>
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#include <pwd.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static void usage(void);
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int
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main(int argc, char *argv[])
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{
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struct group *gp;
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struct passwd *pw;
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char *endp, *p, *user, *group, *grouplist;
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const char *shell;
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gid_t gid, *gidlist;
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uid_t uid;
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int arg, ch, error, gids;
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long ngroups_max;
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bool nonpriviledged;
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gid = 0;
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uid = 0;
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user = group = grouplist = NULL;
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nonpriviledged = false;
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while ((ch = getopt(argc, argv, "G:g:u:n")) != -1) {
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switch(ch) {
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case 'u':
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user = optarg;
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if (*user == '\0')
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usage();
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break;
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case 'g':
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group = optarg;
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if (*group == '\0')
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usage();
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break;
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case 'G':
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grouplist = optarg;
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if (*grouplist == '\0')
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usage();
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break;
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case 'n':
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nonpriviledged = true;
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break;
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case '?':
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default:
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usage();
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}
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}
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argc -= optind;
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argv += optind;
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if (argc < 1)
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usage();
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if (group != NULL) {
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if (isdigit((unsigned char)*group)) {
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gid = (gid_t)strtoul(group, &endp, 0);
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if (*endp != '\0')
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goto getgroup;
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} else {
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getgroup:
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if ((gp = getgrnam(group)) != NULL)
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gid = gp->gr_gid;
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else
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errx(1, "no such group `%s'", group);
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}
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}
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ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
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if ((gidlist = malloc(sizeof(gid_t) * ngroups_max)) == NULL)
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err(1, "malloc");
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for (gids = 0;
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(p = strsep(&grouplist, ",")) != NULL && gids < ngroups_max; ) {
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if (*p == '\0')
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continue;
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if (isdigit((unsigned char)*p)) {
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gidlist[gids] = (gid_t)strtoul(p, &endp, 0);
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if (*endp != '\0')
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goto getglist;
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} else {
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getglist:
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if ((gp = getgrnam(p)) != NULL)
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gidlist[gids] = gp->gr_gid;
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else
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errx(1, "no such group `%s'", p);
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}
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gids++;
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}
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if (p != NULL && gids == ngroups_max)
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errx(1, "too many supplementary groups provided");
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if (user != NULL) {
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if (isdigit((unsigned char)*user)) {
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uid = (uid_t)strtoul(user, &endp, 0);
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if (*endp != '\0')
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goto getuser;
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} else {
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getuser:
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if ((pw = getpwnam(user)) != NULL)
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uid = pw->pw_uid;
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else
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errx(1, "no such user `%s'", user);
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}
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}
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if (nonpriviledged) {
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arg = PROC_NO_NEW_PRIVS_ENABLE;
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error = procctl(P_PID, getpid(), PROC_NO_NEW_PRIVS_CTL, &arg);
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if (error != 0)
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err(1, "procctl");
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}
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if (chdir(argv[0]) == -1 || chroot(".") == -1)
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err(1, "%s", argv[0]);
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if (gids && setgroups(gids, gidlist) == -1)
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err(1, "setgroups");
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if (group && setgid(gid) == -1)
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err(1, "setgid");
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if (user && setuid(uid) == -1)
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err(1, "setuid");
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if (argv[1]) {
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execvp(argv[1], &argv[1]);
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err(1, "%s", argv[1]);
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}
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if (!(shell = getenv("SHELL")))
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shell = _PATH_BSHELL;
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execlp(shell, shell, "-i", (char *)NULL);
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err(1, "%s", shell);
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/* NOTREACHED */
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}
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static void
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usage(void)
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{
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(void)fprintf(stderr, "usage: chroot [-g group] [-G group,group,...] "
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"[-u user] [-n ] newroot [command]\n");
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exit(1);
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}
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