b29e482767
New security enhancements have been made and now you can only umount a filesystem when the status file ".<mntpnt>_mount_bind_done" is available in the specified masterdir. The arguments have been changed and now it accepts two for <masterdir> and <dir>.
107 lines
3.3 KiB
C
107 lines
3.3 KiB
C
/*-
|
|
* Copyright (c) 2010-2011 Juan Romero Pardines.
|
|
* 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.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
|
|
*/
|
|
|
|
/*
|
|
* Umounts a mounted filesystem mountpoint as regular user thanks to
|
|
* the CAP_SYS_ADMIN capability flag set on the file. The following
|
|
* arguments are expected: <masterdir> <dir>.
|
|
*
|
|
* As security measure it only accepts to unmount a mount point
|
|
* when the "status" file has been previously written in the masterdir.
|
|
*/
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <stdbool.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include <errno.h>
|
|
#include <sys/param.h>
|
|
#include <sys/mount.h>
|
|
#include <sys/capability.h>
|
|
|
|
#define _PROGNAME "xbps-src-chroot-capumount"
|
|
|
|
void
|
|
usage(void)
|
|
{
|
|
fprintf(stderr, "Usage: %s <masterdir> <dir>\n", _PROGNAME);
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
int
|
|
main(int argc, char **argv)
|
|
{
|
|
cap_t cap;
|
|
cap_flag_value_t effective, permitted;
|
|
char bindf[PATH_MAX - 1];
|
|
int rv;
|
|
|
|
if (argc != 3)
|
|
usage();
|
|
|
|
cap = cap_get_proc();
|
|
if (cap == NULL) {
|
|
fprintf(stderr, "cap_get_proc() returned %s!\n",
|
|
strerror(errno));
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
cap_get_flag(cap, CAP_SYS_ADMIN, CAP_EFFECTIVE, &effective);
|
|
cap_get_flag(cap, CAP_SYS_ADMIN, CAP_PERMITTED, &permitted);
|
|
if ((effective != CAP_SET) && (permitted != CAP_SET)) {
|
|
fprintf(stderr, "E: missing 'cap_sys_admin' capability!\n"
|
|
"Please set it with: setcap cap_sys_admin=ep %s'\n",
|
|
argv[0]);
|
|
cap_free(cap);
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
cap_free(cap);
|
|
|
|
/* Check that status file exists in masterdir */
|
|
rv = snprintf(bindf, sizeof(bindf), "%s/.%s_mount_bind_done",
|
|
argv[1], argv[2]);
|
|
if (rv < 0 || rv >= sizeof(bindf))
|
|
exit(EXIT_FAILURE);
|
|
|
|
if (access(bindf, R_OK) == -1) {
|
|
fprintf(stderr, "E: cannot umount %s/%s, missing "
|
|
"status file\n", argv[1], argv[2]);
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
/* Security check passed, continue mounting */
|
|
rv = snprintf(bindf, sizeof(bindf), "%s/%s", argv[1], argv[2]);
|
|
if (rv < 0 || rv >= sizeof(bindf))
|
|
exit(EXIT_FAILURE);
|
|
|
|
if ((rv = umount(bindf)) != 0) {
|
|
fprintf(stderr, "E: cannot umount %s: %s\n", argv[1],
|
|
strerror(errno));
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
exit(EXIT_SUCCESS);
|
|
}
|