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ostbuild: ostbuild-user-chroot: New Linux-specific utility for safe chroots

This commit is contained in:
Colin Walters 2011-12-04 16:44:19 -05:00
parent f812720fc6
commit 7093ed4c57
1 changed files with 92 additions and 0 deletions
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src/ostbuild/ostbuild-user-chroot.c Normal file
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/* -*- mode: c; tab-width: 2; indent-tabs-mode: nil -*-
*
* user-chroot: A setuid program that allows non-root users to safely chroot(2)
*
* Copyright 2011 Colin Walters <walters@verbum.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*
*/
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/prctl.h>
#include <linux/securebits.h>
static void
fatal_errno (const char *message) __attribute__ ((noreturn));
static void
fatal_errno (const char *message)
{
perror (message);
exit (1);
}
int
main (int argc,
char **argv)
{
const char *chroot_dir;
const char *program;
uid_t ruid, euid, suid;
gid_t rgid, egid, sgid;
if (argc < 3)
{
fprintf (stderr, "usage: %s DIR PROGRAM ARGS...\n", argv[0]);
exit (1);
}
chroot_dir = argv[1];
program = argv[2];
if (getresgid (&rgid, &egid, &sgid) < 0)
fatal_errno ("getresgid");
if (getresuid (&ruid, &euid, &suid) < 0)
fatal_errno ("getresuid");
if (ruid == 0)
{
fprintf (stderr, "error: ruid is 0\n");
exit (1);
}
if (rgid == 0)
rgid = ruid;
/* Ensure we can't execute setuid programs - see prctl(2) and capabilities(7) */
if (prctl (PR_SET_SECUREBITS,
SECBIT_NOROOT | SECBIT_NOROOT_LOCKED) < 0)
fatal_errno ("prctl");
if (chroot (chroot_dir) < 0)
fatal_errno ("chroot");
if (chdir ("/") < 0)
fatal_errno ("chdir");
/* These are irrevocable - see setuid(2) */
if (setgid (rgid) < 0)
fatal_errno ("setgid");
if (setuid (ruid) < 0)
fatal_errno ("setuid");
if (execv (program, argv + 2) < 0)
fatal_errno ("execv");
return 1;
}