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fs.c
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fs.c
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/*
* Copyright (C) 2014-2021 Firejail Authors
*
* This file is part of firejail project
*
* 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 will 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "firejail.h"
#include "../include/gcov_wrapper.h"
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/wait.h>
#include <linux/limits.h>
#include <fnmatch.h>
#include <glob.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#ifndef O_PATH
#define O_PATH 010000000
#endif
#define MAX_BUF 4096
#define EMPTY_STRING ("")
// check noblacklist statements not matched by a proper blacklist in disable-*.inc files
//#define TEST_NO_BLACKLIST_MATCHING
//***********************************************
// process profile file
//***********************************************
static void fs_remount_rec(const char *dir, OPERATION op);
static char *opstr[] = {
[BLACKLIST_FILE] = "blacklist",
[BLACKLIST_NOLOG] = "blacklist-nolog",
[MOUNT_READONLY] = "read-only",
[MOUNT_TMPFS] = "tmpfs",
[MOUNT_NOEXEC] = "noexec",
[MOUNT_RDWR] = "read-write",
[MOUNT_RDWR_NOCHECK] = "read-write",
};
static void disable_file(OPERATION op, const char *filename) {
assert(filename);
assert(op <OPERATION_MAX);
EUID_ASSERT();
// Resolve all symlinks
char* fname = realpath(filename, NULL);
if (fname == NULL && errno != EACCES) {
return;
}
if (fname == NULL && errno == EACCES) {
// realpath and stat functions will fail on FUSE filesystems
// they don't seem to like a uid of 0
// force mounting
int fd = open(filename, O_PATH|O_CLOEXEC);
if (fd < 0) {
if (arg_debug)
printf("Warning (blacklisting): cannot open %s: %s\n", filename, strerror(errno));
return;
}
EUID_ROOT();
int err = bind_mount_path_to_fd(RUN_RO_DIR, fd);
if (err != 0)
err = bind_mount_path_to_fd(RUN_RO_FILE, fd);
EUID_USER();
close(fd);
if (err == 0) {
if (arg_debug)
printf("Disable %s\n", filename);
if (op == BLACKLIST_FILE)
fs_logger2("blacklist", filename);
else
fs_logger2("blacklist-nolog", filename);
}
else if (arg_debug)
printf("Warning (blacklisting): cannot mount on %s\n", filename);
return;
}
// if the file is not present, do nothing
assert(fname);
struct stat s;
if (stat(fname, &s) < 0) {
if (arg_debug)
printf("Warning (blacklisting): cannot access %s: %s\n", fname, strerror(errno));
free(fname);
return;
}
// check for firejail executable
// we might have a file found in ${PATH} pointing to /usr/bin/firejail
// blacklisting it here will end up breaking situations like user clicks on a link in Thunderbird
// and expects Firefox to open in the same sandbox
if (strcmp(BINDIR "/firejail", fname) == 0) {
free(fname);
return;
}
// modify the file
if (op == BLACKLIST_FILE || op == BLACKLIST_NOLOG) {
// some distros put all executables under /usr/bin and make /bin a symbolic link
if ((strcmp(fname, "/bin") == 0 || strcmp(fname, "/usr/bin") == 0) &&
is_link(filename) &&
S_ISDIR(s.st_mode)) {
fwarning("%s directory link was not blacklisted\n", filename);
}
else {
if (arg_debug) {
if (strcmp(filename, fname))
printf("Disable %s (requested %s)\n", fname, filename);
else
printf("Disable %s\n", fname);
}
else if (arg_debug_blacklists) {
printf("Disable %s", fname);
if (op == BLACKLIST_FILE)
printf("\n");
else
printf(" - no logging\n");
}
int fd = open(fname, O_PATH|O_CLOEXEC);
if (fd < 0) {
if (arg_debug)
printf("Warning (blacklisting): cannot open %s: %s\n", fname, strerror(errno));
free(fname);
return;
}
EUID_ROOT();
if (S_ISDIR(s.st_mode)) {
if (bind_mount_path_to_fd(RUN_RO_DIR, fd) < 0)
errExit("disable file");
}
else {
if (bind_mount_path_to_fd(RUN_RO_FILE, fd) < 0)
errExit("disable file");
}
EUID_USER();
close(fd);
if (op == BLACKLIST_FILE)
fs_logger2("blacklist", fname);
else
fs_logger2("blacklist-nolog", fname);
// files in /etc will be reprocessed during /etc rebuild
if (strncmp(fname, "/etc/", 5) == 0) {
ProfileEntry *prf = malloc(sizeof(ProfileEntry));
if (!prf)
errExit("malloc");
memset(prf, 0, sizeof(ProfileEntry));
prf->data = strdup(fname);
if (!prf->data)
errExit("strdup");
prf->next = cfg.profile_rebuild_etc;
cfg.profile_rebuild_etc = prf;
}
}
}
else if (op == MOUNT_READONLY || op == MOUNT_RDWR || op == MOUNT_NOEXEC) {
fs_remount_rec(fname, op);
}
else if (op == MOUNT_TMPFS) {
if (!S_ISDIR(s.st_mode)) {
fwarning("%s is not a directory; cannot mount a tmpfs on top of it.\n", fname);
free(fname);
return;
}
uid_t uid = getuid();
if (uid != 0) {
// only user owned directories in user home
if (s.st_uid != uid ||
strncmp(cfg.homedir, fname, strlen(cfg.homedir)) != 0 ||
fname[strlen(cfg.homedir)] != '/') {
fwarning("you are not allowed to mount a tmpfs on %s\n", fname);
free(fname);
return;
}
}
fs_tmpfs(fname, uid);
EUID_USER(); // fs_tmpfs returns with EUID 0
selinux_relabel_path(fname, fname);
}
else
assert(0);
free(fname);
}
#ifdef TEST_NO_BLACKLIST_MATCHING
static int nbcheck_start = 0;
static size_t nbcheck_size = 0;
static int *nbcheck = NULL;
#endif
// Treat pattern as a shell glob pattern and blacklist matching files
static void globbing(OPERATION op, const char *pattern, const char *noblacklist[], size_t noblacklist_len) {
assert(pattern);
EUID_ASSERT();
#ifdef TEST_NO_BLACKLIST_MATCHING
if (nbcheck_start == 0) {
nbcheck_start = 1;
nbcheck_size = noblacklist_len;
nbcheck = malloc(sizeof(int) * noblacklist_len);
if (nbcheck == NULL)
errExit("malloc");
memset(nbcheck, 0, sizeof(int) * noblacklist_len);
}
#endif
glob_t globbuf;
// Profiles contain blacklists for files that might not exist on a user's machine.
// GLOB_NOCHECK makes that okay.
int globerr = glob(pattern, GLOB_NOCHECK | GLOB_NOSORT | GLOB_PERIOD, NULL, &globbuf);
if (globerr) {
fprintf(stderr, "Error: failed to glob pattern %s\n", pattern);
exit(1);
}
size_t i, j;
for (i = 0; i < globbuf.gl_pathc; i++) {
char *path = globbuf.gl_pathv[i];
assert(path);
// /home/me/.* can glob to /home/me/.. which would blacklist /home/
const char *base = gnu_basename(path);
if (strcmp(base, ".") == 0 || strcmp(base, "..") == 0)
continue;
// noblacklist is expected to be short in normal cases, so stupid and correct brute force is okay
bool okay_to_blacklist = true;
if (op == BLACKLIST_FILE || op == BLACKLIST_NOLOG) {
for (j = 0; j < noblacklist_len; j++) {
int result = fnmatch(noblacklist[j], path, FNM_PATHNAME);
if (result == FNM_NOMATCH)
continue;
else if (result == 0) {
okay_to_blacklist = false;
#ifdef TEST_NO_BLACKLIST_MATCHING
if (j < nbcheck_size) // noblacklist checking
nbcheck[j] = 1;
#endif
break;
}
else {
fprintf(stderr, "Error: failed to compare path %s with pattern %s\n", path, noblacklist[j]);
exit(1);
}
}
}
if (okay_to_blacklist)
disable_file(op, path);
else if (arg_debug)
printf("Not blacklist %s\n", path);
}
globfree(&globbuf);
}
// blacklist files or directories by mounting empty files on top of them
void fs_blacklist(void) {
ProfileEntry *entry = cfg.profile;
if (!entry)
return;
size_t noblacklist_c = 0;
size_t noblacklist_m = 32;
char **noblacklist = calloc(noblacklist_m, sizeof(*noblacklist));
if (noblacklist == NULL)
errExit("failed allocating memory for noblacklist entries");
EUID_USER();
while (entry) {
OPERATION op = OPERATION_MAX;
char *ptr;
// whitelist commands handled by fs_whitelist()
if (strncmp(entry->data, "whitelist ", 10) == 0 ||
strncmp(entry->data, "nowhitelist ", 12) == 0 ||
strncmp(entry->data, "dbus-", 5) == 0 ||
*entry->data == '\0') {
entry = entry->next;
continue;
}
// process bind command
if (strncmp(entry->data, "bind ", 5) == 0) {
struct stat s;
char *dname1 = entry->data + 5;
char *dname2 = split_comma(dname1);
if (dname2 == NULL ||
stat(dname1, &s) == -1 ||
stat(dname2, &s) == -1) {
fprintf(stderr, "Error: invalid bind command, directory missing\n");
entry = entry->next;
continue;
}
// mount --bind olddir newdir
if (arg_debug)
printf("Mount-bind %s on top of %s\n", dname1, dname2);
// preserve dname2 mode and ownership
// EUID_ROOT(); - option not accessible to non-root users
if (mount(dname1, dname2, NULL, MS_BIND|MS_REC, NULL) < 0)
errExit("mount bind");
/* coverity[toctou] */
if (set_perms(dname2, s.st_uid, s.st_gid,s.st_mode))
errExit("set_perms");
// EUID_USER();
entry = entry->next;
continue;
}
// Process noblacklist command
if (strncmp(entry->data, "noblacklist ", 12) == 0) {
char **enames;
int i;
if (strncmp(entry->data + 12, "${PATH}", 7) == 0) {
// expand ${PATH} macro
char **paths = build_paths();
unsigned int npaths = count_paths();
enames = calloc(npaths, sizeof(char *));
if (!enames)
errExit("calloc");
for (i = 0; paths[i]; i++) {
if (asprintf(&enames[i], "%s%s", paths[i],
entry->data + 19) == -1)
errExit("asprintf");
}
assert(enames[npaths-1] == 0);
}
else {
// expand ${HOME} macro if found or pass as is
enames = calloc(2, sizeof(char *));
if (!enames)
errExit("calloc");
enames[0] = expand_macros(entry->data + 12);
assert(enames[1] == 0);
}
for (i = 0; enames[i]; i++) {
if (noblacklist_c >= noblacklist_m) {
noblacklist_m *= 2;
noblacklist = realloc(noblacklist, sizeof(*noblacklist) * noblacklist_m);
if (noblacklist == NULL)
errExit("failed increasing memory for noblacklist entries");
}
noblacklist[noblacklist_c++] = enames[i];
}
free(enames);
entry = entry->next;
continue;
}
// process blacklist command
if (strncmp(entry->data, "blacklist ", 10) == 0) {
ptr = entry->data + 10;
op = BLACKLIST_FILE;
}
else if (strncmp(entry->data, "blacklist-nolog ", 16) == 0) {
ptr = entry->data + 16;
op = BLACKLIST_NOLOG;
}
else if (strncmp(entry->data, "read-only ", 10) == 0) {
ptr = entry->data + 10;
op = MOUNT_READONLY;
}
else if (strncmp(entry->data, "read-write ", 11) == 0) {
ptr = entry->data + 11;
op = MOUNT_RDWR;
}
else if (strncmp(entry->data, "noexec ", 7) == 0) {
ptr = entry->data + 7;
op = MOUNT_NOEXEC;
}
else if (strncmp(entry->data, "tmpfs ", 6) == 0) {
ptr = entry->data + 6;
op = MOUNT_TMPFS;
}
else if (strncmp(entry->data, "mkdir ", 6) == 0) {
fs_mkdir(entry->data + 6);
entry = entry->next;
continue;
}
else if (strncmp(entry->data, "mkfile ", 7) == 0) {
fs_mkfile(entry->data + 7);
entry = entry->next;
continue;
}
else {
fprintf(stderr, "Error: invalid profile line %s\n", entry->data);
entry = entry->next;
continue;
}
// replace home macro in blacklist array
char *new_name = expand_macros(ptr);
ptr = new_name;
// expand path macro - look for the file in /usr/local/bin, /usr/local/sbin, /bin, /usr/bin, /sbin and /usr/sbin directories
if (ptr) {
if (strncmp(ptr, "${PATH}", 7) == 0) {
char *fname = ptr + 7;
size_t fname_len = strlen(fname);
char **paths = build_paths(); //{"/usr/local/bin", "/usr/local/sbin", "/bin", "/usr/bin/", "/sbin", "/usr/sbin", NULL};
int i = 0;
while (paths[i] != NULL) {
char *path = paths[i];
i++;
char newname[strlen(path) + fname_len + 1];
sprintf(newname, "%s%s", path, fname);
globbing(op, newname, (const char**)noblacklist, noblacklist_c);
}
}
else
globbing(op, ptr, (const char**)noblacklist, noblacklist_c);
}
if (new_name)
free(new_name);
entry = entry->next;
}
size_t i;
#ifdef TEST_NO_BLACKLIST_MATCHING
// noblacklist checking
for (i = 0; i < nbcheck_size; i++)
if (!arg_quiet && !nbcheck[i])
printf("TESTING warning: noblacklist %s not matched by a proper blacklist command in disable*.inc\n",
noblacklist[i]);
// free memory
if (nbcheck) {
free(nbcheck);
nbcheck = NULL;
nbcheck_size = 0;
}
#endif
for (i = 0; i < noblacklist_c; i++)
free(noblacklist[i]);
free(noblacklist);
EUID_ROOT();
}
//***********************************************
// mount namespace
//***********************************************
// mount a writable tmpfs on directory; requires a resolved path
void fs_tmpfs(const char *dir, unsigned check_owner) {
EUID_USER();
assert(dir);
if (arg_debug)
printf("Mounting tmpfs on %s, check owner: %s\n", dir, (check_owner)? "yes": "no");
// get a file descriptor for dir, fails if there is any symlink
int fd = safer_openat(-1, dir, O_PATH|O_DIRECTORY|O_|O_CLOEXEC);
if (fd == -1)
errExit("while opening directory");
struct stat s;
if (fstat(fd, &s) == -1)
errExit("fstat");
if (check_owner && s.st_uid != getuid()) {
fprintf(stderr, "Error: cannot mount tmpfs on %s: not owned by the current user\n", dir);
exit(1);
}
// preserve ownership, mode
char *options;
if (asprintf(&options, "mode=%o,uid=%u,gid=%u", s.st_mode & 07777, s.st_uid, s.st_gid) == -1)
errExit("asprintf");
// preserve mount flags, but remove read-only flag
struct statvfs buf;
if (fstatvfs(fd, &buf) == -1)
errExit("fstatvfs");
unsigned long flags = buf.f_flag & ~(MS_RDONLY|MS_BIND|MS_REMOUNT);
// mount via the symbolic link in /proc/self/fd
EUID_ROOT();
char *proc;
if (asprintf(&proc, "/proc/self/fd/%d", fd) == -1)
errExit("asprintf");
if (mount("tmpfs", proc, "tmpfs", flags|MS_NOSUID|MS_NODEV, options) < 0)
errExit("mounting tmpfs");
// check the last mount operation
MountData *mdata = get_last_mount();
if (strcmp(mdata->fstype, "tmpfs") != 0 || strcmp(mdata->dir, dir) != 0)
errLogExit("invalid tmpfs mount");
fs_logger2("tmpfs", dir);
free(options);
free(proc);
close(fd);
}
// remount path, preserving other mount flags; requires a resolved path
static void fs_remount_simple(const char *path, OPERATION op) {
EUID_ASSERT();
assert(path);
// open path without following symbolic links
int fd = safer_openat(-1, path, O_PATH|O_|O_CLOEXEC);
if (fd < 0)
goto out;
struct stat s;
if (fstat(fd, &s) < 0) {
// fstat can fail with EACCES if path is a FUSE mount,
// mounted without 'allow_root' or 'allow_other'
if (errno != EACCES)
errExit("fstat");
close(fd);
goto out;
}
// get mount flags
struct statvfs buf;
if (fstatvfs(fd, &buf) < 0) {
close(fd);
goto out;
}
unsigned long flags = buf.f_flag;
// read-write option
if (op == MOUNT_RDWR || op == MOUNT_RDWR_NOCHECK) {
// nothing to do if there is no read-only flag
if ((flags & MS_RDONLY) == 0) {
close(fd);
return;
}
// allow only user owned directories, except the user is root
if (op != MOUNT_RDWR_NOCHECK && getuid() != 0 && s.st_uid != getuid()) {
fwarning("you are not allowed to change %s to read-write\n", path);
close(fd);
return;
}
flags &= ~MS_RDONLY;
}
// noexec option
else if (op == MOUNT_NOEXEC) {
// nothing to do if path is mounted noexec already
if ((flags & (MS_NOEXEC|MS_NODEV|MS_NOSUID)) == (MS_NOEXEC|MS_NODEV|MS_NOSUID)) {
close(fd);
return;
}
flags |= MS_NOEXEC|MS_NODEV|MS_NOSUID;
}
// read-only option
else if (op == MOUNT_READONLY) {
// nothing to do if path is mounted read-only already
if ((flags & MS_RDONLY) == MS_RDONLY) {
close(fd);
return;
}
flags |= MS_RDONLY;
}
else
assert(0);
if (arg_debug)
printf("Mounting %s %s\n", opstr[op], path);
// make path a mount point:
// mount --bind path path
EUID_ROOT();
int err = bind_mount_by_fd(fd, fd);
EUID_USER();
if (err) {
close(fd);
goto out;
}
// remount the mount point
// need to open path again
int fd2 = safer_openat(-1, path, O_PATH|O_|O_CLOEXEC);
close(fd); // earliest timepoint to close fd
if (fd2 < 0)
goto out;
// device and inode number should be the same
struct stat s2;
if (fstat(fd2, &s2) < 0)
errExit("fstat");
if (s.st_dev != s2.st_dev || s.st_ino != s2.st_ino)
errLogExit("invalid %s mount", opstr[op]);
EUID_ROOT();
err = remount_by_fd(fd2, flags);
EUID_USER();
close(fd2);
if (err)
goto out;
// run a sanity check on /proc/self/mountinfo and confirm that target of the last
// mount operation was path; if there are other mount points contained inside path,
// one of those will show up as target of the last mount operation instead
MountData *mptr = get_last_mount();
size_t len = strlen(path);
if ((strncmp(mptr->dir, path, len) != 0 ||
(*(mptr->dir + len) != '\0' && *(mptr->dir + len) != '/'))
&& strcmp(path, "/") != 0) // support read-only=/
errLogExit("invalid %s mount", opstr[op]);
fs_logger2(opstr[op], path);
return;
out:
fwarning("not remounting %s\n", path);
}
// remount recursively; requires a resolved path
static void fs_remount_rec(const char *dir, OPERATION op) {
EUID_ASSERT();
assert(dir);
struct stat s;
if (stat(dir, &s) != 0)
return;
if (!S_ISDIR(s.st_mode)) {
// no need to search in /proc/self/mountinfo for submounts if not a directory
fs_remount_simple(dir, op);
return;
}
// get mount point of the directory
int mountid = get_mount_id(dir);
if (mountid == -1)
return;
if (mountid == -2) {
// falling back to a simple remount on old kernels
static int mount_warning = 0;
if (!mount_warning) {
fwarning("read-only, read-write and noexec options are not applied recursively\n");
mount_warning = 1;
}
fs_remount_simple(dir, op);
return;
}
// build array with all mount points that need to get remounted
char **arr = build_mount_array(mountid, dir);
assert(arr);
// remount
char **tmp = arr;
while (*tmp) {
fs_remount_simple(*tmp, op);
free(*tmp++);
}
free(arr);
}
// resolve a path and remount it
void fs_remount(const char *path, OPERATION op, int rec) {
assert(path);
int called_as_root = 0;
if (geteuid() == 0)
called_as_root = 1;
if (called_as_root)
EUID_USER();
char *rpath = realpath(path, NULL);
if (rpath) {
if (rec)
fs_remount_rec(rpath, op);
else
fs_remount_simple(rpath, op);
free(rpath);
}
if (called_as_root)
EUID_ROOT();
}
// Disable /mnt, /media, /run/mount and /run/media access
void fs_mnt(const int enforce) {
EUID_USER();
if (enforce) {
// disable-mnt set in firejail.config
// overriding with noblacklist is not possible in this case
disable_file(BLACKLIST_FILE, "/mnt");
disable_file(BLACKLIST_FILE, "/media");
disable_file(BLACKLIST_FILE, "/run/mount");
disable_file(BLACKLIST_FILE, "/run/media");
}
else {
profile_add("blacklist /mnt");
profile_add("blacklist /media");
profile_add("blacklist /run/mount");
profile_add("blacklist /run/media");
}
EUID_ROOT();
}
// mount /proc and /sys directories
void fs_proc_sys_dev_boot(void) {
// remount /proc/sys readonly
if (arg_debug)
printf("Mounting read-only /proc/sys\n");
if (mount("/proc/sys", "/proc/sys", NULL, MS_BIND | MS_REC, NULL) < 0 ||
mount(NULL, "/proc/sys", NULL, MS_BIND | MS_REMOUNT | MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_REC, NULL) < 0)
errExit("mounting /proc/sys");
fs_logger("read-only /proc/sys");
/* Mount a version of /sys that describes the network namespace */
if (arg_debug)
printf("Remounting /sys directory\n");
// sysfs not yet mounted in overlays, so don't try to unmount it
// expect that unmounting /sys fails in a chroot, no need to print a warning in that case
if (!arg_overlay) {
if (umount2("/sys", MNT_DETACH) < 0 && !cfg.chrootdir)
fwarning("failed to unmount /sys\n");
}
if (mount("sysfs", "/sys", "sysfs", MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REC, NULL) < 0)
fwarning("failed to mount /sys\n");
else
fs_logger("remount /sys");
EUID_USER();
disable_file(BLACKLIST_FILE, "/sys/firmware");
disable_file(BLACKLIST_FILE, "/sys/hypervisor");
{ // allow user access to some directories in /sys/ by specifying 'noblacklist' option
profile_add("blacklist /sys/fs");
profile_add("blacklist /sys/module");
}
disable_file(BLACKLIST_FILE, "/sys/power");
disable_file(BLACKLIST_FILE, "/sys/kernel/debug");
disable_file(BLACKLIST_FILE, "/sys/kernel/vmcoreinfo");
disable_file(BLACKLIST_FILE, "/sys/kernel/uevent_helper");
// various /proc/sys files
disable_file(BLACKLIST_FILE, "/proc/sys/security");
disable_file(BLACKLIST_FILE, "/proc/sys/efi/vars");
disable_file(BLACKLIST_FILE, "/proc/sys/fs/binfmt_misc");
disable_file(BLACKLIST_FILE, "/proc/sys/kernel/core_pattern");
disable_file(BLACKLIST_FILE, "/proc/sys/kernel/modprobe");
disable_file(BLACKLIST_FILE, "/proc/sysrq-trigger");
disable_file(BLACKLIST_FILE, "/proc/sys/kernel/hotplug");
disable_file(BLACKLIST_FILE, "/proc/sys/vm/panic_on_oom");
// various /proc files
disable_file(BLACKLIST_FILE, "/proc/irq");
disable_file(BLACKLIST_FILE, "/proc/bus");
// move /proc/config.gz to disable-common.inc
//disable_file(BLACKLIST_FILE, "/proc/config.gz");
disable_file(BLACKLIST_FILE, "/proc/sched_debug");
disable_file(BLACKLIST_FILE, "/proc/timer_list");
disable_file(BLACKLIST_FILE, "/proc/timer_stats");
disable_file(BLACKLIST_FILE, "/proc/kcore");
disable_file(BLACKLIST_FILE, "/proc/kallsyms");
disable_file(BLACKLIST_FILE, "/proc/mem");
disable_file(BLACKLIST_FILE, "/proc/kmem");
// remove kernel symbol information
if (!arg_allow_debuggers) {
disable_file(BLACKLIST_FILE, "/usr/src/linux");
disable_file(BLACKLIST_FILE, "/lib/modules");
disable_file(BLACKLIST_FILE, "/usr/lib/debug");
disable_file(BLACKLIST_FILE, "/boot");
}
// disable /selinux
disable_file(BLACKLIST_FILE, "/selinux");
// disable /dev/port
disable_file(BLACKLIST_FILE, "/dev/port");
// disable various ipc sockets in /run/user
if (!arg_writable_run_user) {
char *fname;
if (asprintf(&fname, "/run/user/%d", getuid()) == -1)
errExit("asprintf");
if (is_dir(fname)) { // older distros don't have this directory
// disable /run/user/{uid}/gnupg
char *fnamegpg;
if (asprintf(&fnamegpg, "/run/user/%d/gnupg", getuid()) == -1)
errExit("asprintf");
if (create_empty_dir_as_user(fnamegpg, 0700))
fs_logger2("create", fnamegpg);
disable_file(BLACKLIST_FILE, fnamegpg);
free(fnamegpg);
// disable /run/user/{uid}/systemd
char *fnamesysd;
if (asprintf(&fnamesysd, "/run/user/%d/systemd", getuid()) == -1)
errExit("asprintf");
if (create_empty_dir_as_user(fnamesysd, 0755))
fs_logger2("create", fnamesysd);
disable_file(BLACKLIST_FILE, fnamesysd);
free(fnamesysd);
}
free(fname);
}
if (getuid() != 0) {
// disable /dev/kmsg and /proc/kmsg
disable_file(BLACKLIST_FILE, "/dev/kmsg");
disable_file(BLACKLIST_FILE, "/proc/kmsg");
}
EUID_ROOT();
}
// disable firejail configuration in ~/.config/firejail
void disable_config(void) {
EUID_USER();
char *fname;
if (asprintf(&fname, "%s/.config/firejail", cfg.homedir) == -1)
errExit("asprintf");
disable_file(BLACKLIST_FILE, fname);
free(fname);
// disable run time information
disable_file(BLACKLIST_FILE, RUN_FIREJAIL_NETWORK_DIR);
disable_file(BLACKLIST_FILE, RUN_FIREJAIL_BANDWIDTH_DIR);
disable_file(BLACKLIST_FILE, RUN_FIREJAIL_NAME_DIR);
disable_file(BLACKLIST_FILE, RUN_FIREJAIL_PROFILE_DIR);
disable_file(BLACKLIST_FILE, RUN_FIREJAIL_X11_DIR);
EUID_ROOT();
}
// build a basic read-only filesystem
void fs_basic_fs(void) {
uid_t uid = getuid();
// mount a new proc filesystem
if (arg_debug)
printf("Mounting /proc filesystem representing the PID namespace\n");
if (mount("proc", "/proc", "proc", MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_REC, NULL) < 0)
errExit("mounting /proc");
EUID_USER();
if (arg_debug)
printf("Basic read-only filesystem:\n");
if (!arg_writable_etc) {
fs_remount("/etc", MOUNT_READONLY, 1);
if (uid)
fs_remount("/etc", MOUNT_NOEXEC, 1);
}
if (!arg_writable_var) {
fs_remount("/var", MOUNT_READONLY, 1);
if (uid)
fs_remount("/var", MOUNT_NOEXEC, 1);
}
fs_remount("/usr", MOUNT_READONLY, 1);
fs_remount("/bin", MOUNT_READONLY, 1);
fs_remount("/sbin", MOUNT_READONLY, 1);
fs_remount("/lib", MOUNT_READONLY, 1);
fs_remount("/lib64", MOUNT_READONLY, 1);
fs_remount("/lib32", MOUNT_READONLY, 1);
fs_remount("/libx32", MOUNT_READONLY, 1);
EUID_ROOT();
// update /var directory in order to support multiple sandboxes running on the same root directory
fs_var_lock();
if (!arg_keep_var_tmp)
fs_var_tmp();
if (!arg_writable_var_log)
fs_var_log();
else
fs_remount("/var/log", MOUNT_RDWR_NOCHECK, 0);
fs_var_lib();
fs_var_cache();
fs_var_utmp();
fs_machineid();
// don't leak user information
restrict_users();
// when starting as root, firejail config is not disabled;
if (uid)
disable_config();
}
#ifdef HAVE_OVERLAYFS
char *fs_check_overlay_dir(const char *subdirname, int allow_reuse) {
assert(subdirname);
EUID_ASSERT();
struct stat s;
char *dirname;
if (asprintf(&dirname, "%s/.firejail", cfg.homedir) == -1)
errExit("asprintf");
// check if ~/.firejail already exists
if (lstat(dirname, &s) == 0) {
if (!S_ISDIR(s.st_mode)) {
if (S_ISLNK(s.st_mode))
fprintf(stderr, "Error: %s is a symbolic link\n", dirname);
else
fprintf(stderr, "Error: %s is not a directory\n", dirname);
exit(1);
}
if (s.st_uid != getuid()) {
fprintf(stderr, "Error: %s is not owned by the current user\n", dirname);
exit(1);
}
}
else {
// create ~/.firejail directory
create_empty_dir_as_user(dirname, 0700);
if (stat(dirname, &s) == -1) {
fprintf(stderr, "Error: cannot create directory %s\n", dirname);
exit(1);
}
}
free(dirname);
// check overlay directory
if (asprintf(&dirname, "%s/.firejail/%s", cfg.homedir, subdirname) == -1)
errExit("asprintf");
if (lstat(dirname, &s) == 0) {
if (!S_ISDIR(s.st_mode)) {
if (S_ISLNK(s.st_mode))
fprintf(stderr, "Error: %s is a symbolic link\n", dirname);
else
fprintf(stderr, "Error: %s is not a directory\n", dirname);
exit(1);
}
if (s.st_uid != 0) {
fprintf(stderr, "Error: overlay directory %s is not owned by the root user\n", dirname);
exit(1);
}
if (allow_reuse == 0) {
fprintf(stderr, "Error: overlay directory exists, but reuse is not allowed\n");
exit(1);
}
}
return dirname;
}
// mount overlayfs on top of / directory
// mounting an overlay and chrooting into it:
//
// Old Ubuntu kernel
// # cd ~
// # mkdir -p overlay/root
// # mkdir -p overlay/diff
// # mount -t overlayfs -o lowerdir=/,upperdir=/root/overlay/diff overlayfs /root/overlay/root
// # chroot /root/overlay/root
// to shutdown, first exit the chroot and then unmount the overlay
// # exit
// # umount /root/overlay/root
//
// Kernels 3.18+
// # cd ~
// # mkdir -p overlay/root
// # mkdir -p overlay/diff
// # mkdir -p overlay/work
// # mount -t overlay -o lowerdir=/,upperdir=/root/overlay/diff,workdir=/root/overlay/work overlay /root/overlay/root
// # cat /etc/mtab | grep overlay
// /root/overlay /root/overlay/root overlay rw,relatime,lowerdir=/,upperdir=/root/overlay/diff,workdir=/root/overlay/work 0 0
// # chroot /root/overlay/root
// to shutdown, first exit the chroot and then unmount the overlay
// # exit
// # umount /root/overlay/root
// to do: fix the code below; also, it might work without /dev, but consider keeping /dev/shm; add locking mechanism for overlay-clean
#include <sys/utsname.h>
void fs_overlayfs(void) {
struct stat s;
// check kernel version
struct utsname u;
int rv = uname(&u);