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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 <sys/mount.h>
#include <dirent.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <grp.h>
//#include <ftw.h>
#include <fcntl.h>
#ifndef O_PATH
#define O_PATH 010000000
#endif
static void disable_tab_completion(const char *homedir) {
char *fname;
if (asprintf(&fname, "%s/.inputrc", homedir) == -1)
errExit("asprintf");
// don't create a new one if we already have it
if (access(fname, F_OK)) {
FILE *fp = fopen(fname, "w");
if (!fp)
errExit("fopen");
fprintf(fp, "set disable-completion on\n");
fclose(fp);
if (chmod(fname, 0644))
errExit("chmod");
}
free(fname);
}
static void skel(const char *homedir) {
EUID_ASSERT();
char *fname;
disable_tab_completion(homedir);
// zsh
if (!arg_shell_none && (strcmp(cfg.shell,"/usr/bin/zsh") == 0 || strcmp(cfg.shell,"/bin/zsh") == 0)) {
// copy skel files
if (asprintf(&fname, "%s/.zshrc", homedir) == -1)
errExit("asprintf");
// don't copy it if we already have the file
if (access(fname, F_OK) == 0)
return;
if (is_link(fname)) { // access(3) on dangling symlinks fails, try again using lstat
fprintf(stderr, "Error: invalid %s file\n", fname);
exit(1);
}
if (access("/etc/skel/.zshrc", R_OK) == 0) {
copy_file_as_user("/etc/skel/.zshrc", fname, 0644); // regular user
fs_logger("clone /etc/skel/.zshrc");
fs_logger2("clone", fname);
}
else {
touch_file_as_user(fname, 0644);
fs_logger2("touch", fname);
}
selinux_relabel_path(fname, fname);
free(fname);
}
// csh
else if (!arg_shell_none && strcmp(cfg.shell,"/bin/csh") == 0) {
// copy skel files
if (asprintf(&fname, "%s/.cshrc", homedir) == -1)
errExit("asprintf");
// don't copy it if we already have the file
if (access(fname, F_OK) == 0)
return;
if (is_link(fname)) { // access(3) on dangling symlinks fails, try again using lstat
fprintf(stderr, "Error: invalid %s file\n", fname);
exit(1);
}
if (access("/etc/skel/.cshrc", R_OK) == 0) {
copy_file_as_user("/etc/skel/.cshrc", fname, 0644); // regular user
fs_logger("clone /etc/skel/.cshrc");
fs_logger2("clone", fname);
}
else {
touch_file_as_user(fname, 0644);
fs_logger2("touch", fname);
}
selinux_relabel_path(fname, fname);
free(fname);
}
// bash etc.
else {
// copy skel files
if (asprintf(&fname, "%s/.bashrc", homedir) == -1)
errExit("asprintf");
// don't copy it if we already have the file
if (access(fname, F_OK) == 0)
return;
if (is_link(fname)) { // access(3) on dangling symlinks fails, try again using lstat
fprintf(stderr, "Error: invalid %s file\n", fname);
exit(1);
}
if (access("/etc/skel/.bashrc", R_OK) == 0) {
copy_file_as_user("/etc/skel/.bashrc", fname, 0644); // regular user
fs_logger("clone /etc/skel/.bashrc");
fs_logger2("clone", fname);
}
selinux_relabel_path(fname, fname);
free(fname);
}
}
static int store_xauthority(void) {
EUID_ASSERT();
if (arg_x11_block)
return 0;
// put a copy of .Xauthority in XAUTHORITY_FILE
char *dest = RUN_XAUTHORITY_FILE;
char *src;
if (asprintf(&src, "%s/.Xauthority", cfg.homedir) == -1)
errExit("asprintf");
struct stat s;
if (lstat(src, &s) == 0) {
if (S_ISLNK(s.st_mode)) {
fwarning("invalid .Xauthority file\n");
free(src);
return 0;
}
// create an empty file as root, and change ownership to user
EUID_ROOT();
FILE *fp = fopen(dest, "we");
if (fp) {
fprintf(fp, "\n");
SET_PERMS_STREAM(fp, getuid(), getgid(), 0600);
fclose(fp);
}
else
errExit("fopen");
EUID_USER();
copy_file_as_user(src, dest, 0600); // regular user
selinux_relabel_path(dest, src);
fs_logger2("clone", dest);
free(src);
return 1; // file copied
}
free(src);
return 0;
}
static int store_asoundrc(void) {
EUID_ASSERT();
if (arg_nosound)
return 0;
// put a copy of .asoundrc in ASOUNDRC_FILE
char *dest = RUN_ASOUNDRC_FILE;
char *src;
if (asprintf(&src, "%s/.asoundrc", cfg.homedir) == -1)
errExit("asprintf");
struct stat s;
if (lstat(src, &s) == 0) {
if (S_ISLNK(s.st_mode)) {
// make sure the real path of the file is inside the home directory
/* coverity[toctou] */
char *rp = realpath(src, NULL);
if (!rp) {
fprintf(stderr, "Error: Cannot access %s\n", src);
exit(1);
}
if (strncmp(rp, cfg.homedir, strlen(cfg.homedir)) != 0 || rp[strlen(cfg.homedir)] != '/') {
fprintf(stderr, "Error: .asoundrc is a symbolic link pointing to a file outside home directory\n");
exit(1);
}
free(rp);
}
// create an empty file as root, and change ownership to user
EUID_ROOT();
FILE *fp = fopen(dest, "we");
if (fp) {
fprintf(fp, "\n");
SET_PERMS_STREAM(fp, getuid(), getgid(), 0644);
fclose(fp);
}
else
errExit("fopen");
EUID_USER();
copy_file_as_user(src, dest, 0644); // regular user
fs_logger2("clone", dest);
selinux_relabel_path(dest, src);
free(src);
return 1; // file copied
}
free(src);
return 0;
}
static void copy_xauthority(void) {
EUID_ASSERT();
// copy XAUTHORITY_FILE in the new home directory
char *src = RUN_XAUTHORITY_FILE ;
char *dest;
if (asprintf(&dest, "%s/.Xauthority", cfg.homedir) == -1)
errExit("asprintf");
// if destination is a symbolic link, exit the sandbox!!!
if (is_link(dest)) {
fprintf(stderr, "Error: %s is a symbolic link\n", dest);
exit(1);
}
copy_file_as_user(src, dest, S_IRUSR | S_IWUSR); // regular user
fs_logger2("clone", dest);
selinux_relabel_path(dest, dest);
free(dest);
EUID_ROOT();
unlink(src); // delete the temporary file
EUID_USER();
}
static void copy_asoundrc(void) {
EUID_ASSERT();
// copy ASOUNDRC_FILE in the new home directory
char *src = RUN_ASOUNDRC_FILE ;
char *dest;
if (asprintf(&dest, "%s/.asoundrc", cfg.homedir) == -1)
errExit("asprintf");
// if destination is a symbolic link, exit the sandbox!!!
if (is_link(dest)) {
fprintf(stderr, "Error: %s is a symbolic link\n", dest);
exit(1);
}
copy_file_as_user(src, dest, S_IRUSR | S_IWUSR); // regular user
fs_logger2("clone", dest);
selinux_relabel_path(dest, dest);
free(dest);
EUID_ROOT();
unlink(src); // delete the temporary file
EUID_USER();
}
// private mode (--private=homedir):
// mount homedir on top of /home/user,
// tmpfs on top of /root in nonroot mode,
// set skel files,
// restore .Xauthority
void fs_private_homedir(void) {
char *homedir = cfg.homedir;
char *private_homedir = cfg.home_private;
assert(homedir);
assert(private_homedir);
EUID_ASSERT();
uid_t u = getuid();
// gid_t g = getgid();
int xflag = store_xauthority();
int aflag = store_asoundrc();
// mount bind private_homedir on top of homedir
if (arg_debug)
printf("Mount-bind %s on top of %s\n", private_homedir, homedir);
// get file descriptors for homedir and private_homedir, fails if there is any symlink
int src = safer_openat(-1, private_homedir, O_PATH|O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC);
if (src == -1)
errExit("opening private directory");
int dst = safer_openat(-1, homedir, O_PATH|O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC);
if (dst == -1)
errExit("opening home directory");
// both mount source and target should be owned by the user
struct stat s;
if (fstat(src, &s) == -1)
errExit("fstat");
if (s.st_uid != u) {
fprintf(stderr, "Error: private directory is not owned by the current user\n");
exit(1);
}
if ((S_IRWXU & s.st_mode) != S_IRWXU)
fwarning("no full permissions on private directory\n");
if (fstat(dst, &s) == -1)
errExit("fstat");
if (s.st_uid != u) {
fprintf(stderr, "Error: cannot mount private directory:\n"
"Home directory is not owned by the current user\n");
exit(1);
}
// mount via the links in /proc/self/fd
EUID_ROOT();
if (bind_mount_by_fd(src, dst))
errExit("mount bind");
EUID_USER();
// check /proc/self/mountinfo to confirm the mount is ok
MountData *mptr = get_last_mount();
size_t len = strlen(homedir);
if (strncmp(mptr->dir, homedir, len) != 0 ||
(*(mptr->dir + len) != '\0' && *(mptr->dir + len) != '/'))
errLogExit("invalid private mount");
close(src);
close(dst);
fs_logger3("mount-bind", private_homedir, homedir);
fs_logger2("whitelist", homedir);
// preserve mode and ownership
// if (chown(homedir, s.st_uid, s.st_gid) == -1)
// errExit("mount-bind chown");
// if (chmod(homedir, s.st_mode) == -1)
// errExit("mount-bind chmod");
EUID_ROOT();
if (u != 0) {
// mask /root
if (arg_debug)
printf("Mounting a new /root directory\n");
if (mount("tmpfs", "/root", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_STRICTATIME, "mode=700,gid=0") < 0)
errExit("mounting /root directory");
selinux_relabel_path("/root", "/root");
fs_logger("tmpfs /root");
}
if (u == 0 && !arg_allusers) {
// mask /home
if (arg_debug)
printf("Mounting a new /home directory\n");
if (mount("tmpfs", "/home", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_STRICTATIME, "mode=755,gid=0") < 0)
errExit("mounting /home directory");
selinux_relabel_path("/home", "/home");
fs_logger("tmpfs /home");
}
EUID_USER();
skel(homedir);
if (xflag)
copy_xauthority();
if (aflag)
copy_asoundrc();
}
// private mode (--private):
// mount tmpfs over /home/user,
// tmpfs on top of /root in nonroot mode,
// set skel files,
// restore .Xauthority
void fs_private(void) {
char *homedir = cfg.homedir;
assert(homedir);
EUID_ASSERT();
uid_t u = getuid();
gid_t g = getgid();
int xflag = store_xauthority();
int aflag = store_asoundrc();
EUID_ROOT();
// mask /root
if (arg_debug)
printf("Mounting a new /root directory\n");
if (mount("tmpfs", "/root", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_STRICTATIME, "mode=700,gid=0") < 0)
errExit("mounting /root directory");
selinux_relabel_path("/root", "/root");
fs_logger("tmpfs /root");
// mask /home
if (!arg_allusers) {
if (arg_debug)
printf("Mounting a new /home directory\n");
if (mount("tmpfs", "/home", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_STRICTATIME, "mode=755,gid=0") < 0)
errExit("mounting /home directory");
selinux_relabel_path("/home", "/home");
fs_logger("tmpfs /home");
}
EUID_USER();
if (u != 0) {
if (!arg_allusers && strncmp(homedir, "/home/", 6) == 0) {
// create new empty /home/user directory
if (arg_debug)
printf("Create a new user directory\n");
EUID_ROOT();
if (mkdir(homedir, S_IRWXU) == -1) {
if (mkpath_as_root(homedir) == -1)
errExit("mkpath");
if (mkdir(homedir, S_IRWXU) == -1)
errExit("mkdir");
}
if (chown(homedir, u, g) < 0)
errExit("chown");
EUID_USER();
fs_logger2("mkdir", homedir);
fs_logger2("tmpfs", homedir);
}
else
// mask user home directory
// the directory should be owned by the current user
fs_tmpfs(homedir, 1);
selinux_relabel_path(homedir, homedir);
}
skel(homedir);
if (xflag)
copy_xauthority();
if (aflag)
copy_asoundrc();
}
// check new private home directory (--private= option) - exit if it fails
void fs_check_private_dir(void) {
EUID_ASSERT();
invalid_filename(cfg.home_private, 0); // no globbing
// Expand the home directory
char *tmp = expand_macros(cfg.home_private);
cfg.home_private = realpath(tmp, NULL);
free(tmp);
if (!cfg.home_private
|| !is_dir(cfg.home_private)) {
fprintf(stderr, "Error: invalid private directory\n");
exit(1);
}
}
// check new private working directory (--private-cwd= option) - exit if it fails
void fs_check_private_cwd(const char *dir) {
EUID_ASSERT();
invalid_filename(dir, 0); // no globbing
if (strcmp(dir, ".") == 0 || *dir != '/')
goto errout;
// Expand the working directory
cfg.cwd = expand_macros(dir);
// realpath/is_dir not used because path may not exist outside of jail
if (strstr(cfg.cwd, ".."))
goto errout;
return;
errout:
fprintf(stderr, "Error: invalid private working directory\n");
exit(1);
}
//***********************************************************************************
// --private-home
//***********************************************************************************
static char *check_dir_or_file(const char *name) {
EUID_ASSERT();
assert(name);
// basic checks
invalid_filename(name, 0); // no globbing
if (arg_debug)
printf("Private home: checking %s\n", name);
// expand home directory
char *fname = expand_macros(name);
assert(fname);
// If it doesn't start with '/', it must be relative to homedir
if (fname[0] != '/') {
char* tmp;
if (asprintf(&tmp, "%s/%s", cfg.homedir, fname) == -1)
errExit("asprintf");
free(fname);
fname = tmp;
}
// we allow only files in user home directory or symbolic links to files or directories owned by the user
struct stat s;
if (lstat(fname, &s) == 0 && S_ISLNK(s.st_mode)) {
if (strncmp(fname, cfg.homedir, strlen(cfg.homedir)) != 0 || fname[strlen(cfg.homedir)] != '/')
goto errexit;
if (stat(fname, &s) == 0) {
if (s.st_uid != getuid()) {
fprintf(stderr, "Error: symbolic link %s to file or directory not owned by the user\n", fname);
exit(1);
}
return fname;
}
else // dangling link
goto errexit;
}
else {
// check the file is in user home directory
char *rname = realpath(fname, NULL);
if (!rname || strncmp(rname, cfg.homedir, strlen(cfg.homedir)) != 0)
goto errexit;
// a full home directory is not allowed
char *ptr = rname + strlen(cfg.homedir);
if (*ptr != '/')
goto errexit;
// only top files and directories in user home are allowed
ptr = strchr(++ptr, '/');
if (ptr) {
fprintf(stderr, "Error: only top files and directories in user home are allowed\n");
exit(1);
}
free(fname);
return rname;
}
errexit:
fprintf(stderr, "Error: invalid file %s\n", name);
exit(1);
}
static void duplicate(char *name) {
EUID_ASSERT();
char *fname = check_dir_or_file(name);
if (arg_debug)
printf("Private home: duplicating %s\n", fname);
assert(strncmp(fname, cfg.homedir, strlen(cfg.homedir)) == 0);
struct stat s;
if (lstat(fname, &s) == -1) {
free(fname);
return;
}
else if (S_ISDIR(s.st_mode)) {
// create the directory in RUN_HOME_DIR
char *path;
char *ptr = strrchr(fname, '/');
ptr++;
if (asprintf(&path, "%s/%s", RUN_HOME_DIR, ptr) == -1)
errExit("asprintf");
create_empty_dir_as_user(path, 0755);
sbox_run(SBOX_USER| SBOX_CAPS_NONE | SBOX_SECCOMP, 3, PATH_FCOPY, fname, path);
free(path);
}
else
sbox_run(SBOX_USER| SBOX_CAPS_NONE | SBOX_SECCOMP, 3, PATH_FCOPY, fname, RUN_HOME_DIR);
fs_logger2("clone", fname);
fs_logger_print(); // save the current log
free(fname);
}
// private mode (--private-home=list):
// mount homedir on top of /home/user,
// tmpfs on top of /root in nonroot mode,
// tmpfs on top of /tmp in root mode,
// set skel files,
// restore .Xauthority
void fs_private_home_list(void) {
char *homedir = cfg.homedir;
char *private_list = cfg.home_private_keep;
assert(homedir);
assert(private_list);
EUID_ASSERT();
timetrace_start();
uid_t uid = getuid();
gid_t gid = getgid();
int xflag = store_xauthority();
int aflag = store_asoundrc();
EUID_ROOT();
// create /run/firejail/mnt/home directory
mkdir_attr(RUN_HOME_DIR, 0755, uid, gid);
selinux_relabel_path(RUN_HOME_DIR, homedir);
// save the current log
fs_logger_print();
EUID_USER();
// copy the list of files in the new home directory
if (arg_debug)
printf("Copying files in the new home:\n");
char *dlist = strdup(cfg.home_private_keep);
if (!dlist)
errExit("strdup");
char *ptr = strtok(dlist, ",");
if (!ptr) {
fprintf(stderr, "Error: invalid private-home argument\n");
exit(1);
}
duplicate(ptr);
while ((ptr = strtok(NULL, ",")) != NULL)
duplicate(ptr);
fs_logger_print(); // save the current log
free(dlist);
if (arg_debug)
printf("Mount-bind %s on top of %s\n", RUN_HOME_DIR, homedir);
int fd = safer_openat(-1, homedir, O_PATH|O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC);
if (fd == -1)
errExit("opening home directory");
// home directory should be owned by the user
struct stat s;
if (fstat(fd, &s) == -1)
errExit("fstat");
if (s.st_uid != uid) {
fprintf(stderr, "Error: cannot mount private directory:\n"
"Home directory is not owned by the current user\n");
exit(1);
}
// mount using the file descriptor
EUID_ROOT();
if (bind_mount_path_to_fd(RUN_HOME_DIR, fd))
errExit("mount bind");
EUID_USER();
close(fd);
// check /proc/self/mountinfo to confirm the mount is ok
MountData *mptr = get_last_mount();
if (strcmp(mptr->dir, homedir) != 0 || strcmp(mptr->fstype, "tmpfs") != 0)
errLogExit("invalid private-home mount");
fs_logger2("tmpfs", homedir);
EUID_ROOT();
if (uid != 0) {
// mask /root
if (arg_debug)
printf("Mounting a new /root directory\n");
if (mount("tmpfs", "/root", "tmpfs", MS_NOSUID | MS_NODEV | MS_STRICTATIME, "mode=700,gid=0") < 0)
errExit("mounting /root directory");
selinux_relabel_path("/root", "/root");
fs_logger("tmpfs /root");
}
if (uid == 0 && !arg_allusers) {
// mask /home
if (arg_debug)
printf("Mounting a new /home directory\n");
if (mount("tmpfs", "/home", "tmpfs", MS_NOSUID | MS_NODEV | MS_STRICTATIME, "mode=755,gid=0") < 0)
errExit("mounting /home directory");
selinux_relabel_path("/home", "/home");
fs_logger("tmpfs /home");
}
// mask RUN_HOME_DIR, it is writable and not noexec
if (mount("tmpfs", RUN_HOME_DIR, "tmpfs", MS_NOSUID | MS_NODEV | MS_STRICTATIME, "mode=755,gid=0") < 0)
errExit("mounting tmpfs");
EUID_USER();
skel(homedir);
if (xflag)
copy_xauthority();
if (aflag)
copy_asoundrc();
if (!arg_quiet)
fprintf(stderr, "Home directory installed in %0.2f ms\n", timetrace_end());
}
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