freebsd-dev/sbin/mount_nullfs/mount_nullfs.c
Doug Rabson a3f714c4ff Add support for mounting single files in nullfs
My main use-case for this is to support mounting config files and secrets
into OCI containers. My current workaround copies the files into the
container which is messy and risks secrets leaking into container images
if the cleanup fails.

Reviewed by:	mjg, kib
Tested by:	pho
Differential Revision: https://reviews.freebsd.org/D37478
2022-12-19 16:44:54 +00:00

145 lines
4.1 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1992, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software donated to Berkeley by
* Jan-Simon Pendry.
*
* 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.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1992, 1993, 1994\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)mount_null.c 8.6 (Berkeley) 4/26/95";
#endif
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
#include <sys/param.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>
#include "mntopts.h"
static void usage(void) __dead2;
static int
stat_realpath(const char *path, char *resolved, struct stat *sbp)
{
if (realpath(path, resolved) == NULL || stat(resolved, sbp) != 0)
return (1);
return (0);
}
int
main(int argc, char *argv[])
{
struct iovec *iov;
char *p, *val;
char mountpoint[MAXPATHLEN];
char target[MAXPATHLEN];
char errmsg[255];
int ch, iovlen;
char nullfs[] = "nullfs";
struct stat target_stat;
struct stat mountpoint_stat;
iov = NULL;
iovlen = 0;
errmsg[0] = '\0';
while ((ch = getopt(argc, argv, "o:")) != -1)
switch(ch) {
case 'o':
val = strdup("");
p = strchr(optarg, '=');
if (p != NULL) {
free(val);
*p = '\0';
val = p + 1;
}
build_iovec(&iov, &iovlen, optarg, val, (size_t)-1);
break;
case '?':
default:
usage();
}
argc -= optind;
argv += optind;
if (argc != 2)
usage();
/* resolve target and mountpoint with realpath(3) */
if (stat_realpath(argv[0], target, &target_stat) != 0)
err(EX_USAGE, "%s", target);
if (stat_realpath(argv[1], mountpoint, &mountpoint_stat) != 0)
err(EX_USAGE, "%s", mountpoint);
if (!S_ISDIR(target_stat.st_mode) && !S_ISREG(target_stat.st_mode))
errx(EX_USAGE, "%s: must be either a file or directory",
target);
if ((target_stat.st_mode & S_IFMT) !=
(mountpoint_stat.st_mode & S_IFMT))
errx(EX_USAGE,
"%s: must be same type as %s (file or directory)",
mountpoint, target);
build_iovec(&iov, &iovlen, "fstype", nullfs, (size_t)-1);
build_iovec(&iov, &iovlen, "fspath", mountpoint, (size_t)-1);
build_iovec(&iov, &iovlen, "target", target, (size_t)-1);
build_iovec(&iov, &iovlen, "errmsg", errmsg, sizeof(errmsg));
if (nmount(iov, iovlen, 0) < 0) {
if (errmsg[0] != 0)
err(1, "%s: %s", mountpoint, errmsg);
else
err(1, "%s", mountpoint);
}
exit(0);
}
static void
usage(void)
{
(void)fprintf(stderr,
"usage: mount_nullfs [-o options] target mount-point\n");
exit(1);
}