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flatpak-builder/xdg-app-helper.c

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/* xdg-app-helper
* Copyright (C) 2014 Alexander Larsson
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
*/
#define _GNU_SOURCE /* Required for CLONE_NEWNS */
#include <assert.h>
#include <arpa/inet.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <linux/loop.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <net/if.h>
#include <netinet/in.h>
#include <sched.h>
#include <signal.h>
#include <poll.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/eventfd.h>
#include <sys/signalfd.h>
#include <sys/capability.h>
#include <sys/prctl.h>
#include <unistd.h>
#if 0
#define __debug__(x) printf x
#else
#define __debug__(x)
#endif
#define N_ELEMENTS(arr) (sizeof (arr) / sizeof ((arr)[0]))
#define TRUE 1
#define FALSE 0
typedef int bool;
#define READ_END 0
#define WRITE_END 1
static void
die_with_error (const char *format, ...)
{
va_list args;
int errsv;
errsv = errno;
va_start (args, format);
vfprintf (stderr, format, args);
va_end (args);
fprintf (stderr, ": %s\n", strerror (errsv));
exit (1);
}
static void
die (const char *format, ...)
{
va_list args;
va_start (args, format);
vfprintf (stderr, format, args);
va_end (args);
fprintf (stderr, "\n");
exit (1);
}
static void *
xmalloc (size_t size)
{
void *res = malloc (size);
if (res == NULL)
die ("oom");
return res;
}
static void *
xrealloc (void *ptr, size_t size)
{
void *res = realloc (ptr, size);
if (size != 0 && res == NULL)
die ("oom");
return res;
}
static char *
xstrdup (const char *str)
{
char *res;
assert (str != NULL);
res = strdup (str);
if (res == NULL)
die ("oom");
return res;
}
static void
xsetenv (const char *name, const char *value, int overwrite)
{
if (setenv (name, value, overwrite))
die ("setenv failed");
}
static void
xunsetenv (const char *name)
{
if (unsetenv(name))
die ("unsetenv failed");
}
char *
strconcat (const char *s1,
const char *s2)
{
size_t len = 0;
char *res;
if (s1)
len += strlen (s1);
if (s2)
len += strlen (s2);
res = xmalloc (len + 1);
*res = 0;
if (s1)
strcat (res, s1);
if (s2)
strcat (res, s2);
return res;
}
char *
strconcat3 (const char *s1,
const char *s2,
const char *s3)
{
size_t len = 0;
char *res;
if (s1)
len += strlen (s1);
if (s2)
len += strlen (s2);
if (s3)
len += strlen (s3);
res = xmalloc (len + 1);
*res = 0;
if (s1)
strcat (res, s1);
if (s2)
strcat (res, s2);
if (s3)
strcat (res, s3);
return res;
}
char *
strconcat_len (const char *s1,
const char *s2,
size_t s2_len)
{
size_t len = 0;
char *res;
if (s1)
len += strlen (s1);
if (s2)
len += s2_len;
res = xmalloc (len + 1);
*res = 0;
if (s1)
strcat (res, s1);
if (s2)
strncat (res, s2, s2_len);
return res;
}
char*
strdup_printf (const char *format,
...)
{
char *buffer = NULL;
va_list args;
va_start (args, format);
vasprintf (&buffer, format, args);
va_end (args);
if (buffer == NULL)
die ("oom");
return buffer;
}
static inline int raw_clone(unsigned long flags, void *child_stack) {
#if defined(__s390__) || defined(__CRIS__)
/* On s390 and cris the order of the first and second arguments
* of the raw clone() system call is reversed. */
return (int) syscall(__NR_clone, child_stack, flags);
#else
return (int) syscall(__NR_clone, flags, child_stack);
#endif
}
void
usage (char **argv)
{
fprintf (stderr, "usage: %s [OPTIONS...] RUNTIMEPATH COMMAND [ARGS...]\n\n", argv[0]);
fprintf (stderr,
" -a Specify path for application (mounted at /self)\n"
" -b SOURCE=DEST Bind extra source directory into DEST (must be in /usr, /self, /run/host)\n"
" -d SOCKETPATH Use SOCKETPATH as dbus session bus\n"
" -D SOCKETPATH Use SOCKETPATH as dbus system bus\n"
" -e Make /self/exports writable\n"
" -E Make /etc a pure symlink to /usr/etc\n"
" -f Mount the host filesystems\n"
" -g Allow use of direct rendering graphics\n"
" -F Mount the host filesystems read-only\n"
" -H Mount the users home directory (implied by -f)\n"
" -i Share IPC namespace with session\n"
" -I APPID Set app id (used to find app data)\n"
" -l Lock .ref files in all mounts\n"
" -m PATH Set path to xdg-app-session-helper output\n"
" -n Share network namespace with session\n"
" -p SOCKETPATH Use SOCKETPATH as pulseaudio connection\n"
" -s Share Shm namespace with session\n"
" -v PATH Mount PATH as /var\n"
" -w Make /self writable\n"
" -W Make /usr writable\n"
" -x SOCKETPATH Use SOCKETPATH as X display\n"
" -y SOCKETPATH Use SOCKETPATH as Wayland display\n"
);
exit (1);
}
static int
pivot_root (const char * new_root, const char * put_old)
{
#ifdef __NR_pivot_root
return syscall(__NR_pivot_root, new_root, put_old);
#else
errno = ENOSYS;
return -1;
#endif
}
typedef enum {
FILE_TYPE_REGULAR,
FILE_TYPE_DIR,
FILE_TYPE_SYMLINK,
FILE_TYPE_SYSTEM_SYMLINK,
FILE_TYPE_BIND,
FILE_TYPE_BIND_RO,
FILE_TYPE_MOUNT,
FILE_TYPE_REMOUNT,
FILE_TYPE_DEVICE,
FILE_TYPE_SHM,
} file_type_t;
typedef enum {
FILE_FLAGS_NONE = 0,
FILE_FLAGS_NON_FATAL = 1 << 0,
FILE_FLAGS_IF_LAST_FAILED = 1 << 1,
FILE_FLAGS_DEVICES = 1 << 2,
} file_flags_t;
typedef struct {
file_type_t type;
const char *name;
mode_t mode;
const char *data;
file_flags_t flags;
int *option;
} create_table_t;
typedef struct {
const char *what;
const char *where;
const char *type;
const char *options;
unsigned long flags;
} mount_table_t;
int
ascii_isdigit (char c)
{
return c >= '0' && c <= '9';
}
static bool create_etc_symlink = FALSE;
static bool create_etc_dir = TRUE;
static bool create_monitor_links = FALSE;
static bool allow_dri = FALSE;
static const create_table_t create[] = {
{ FILE_TYPE_DIR, ".oldroot", 0755 },
{ FILE_TYPE_DIR, "usr", 0755 },
{ FILE_TYPE_DIR, "tmp", 01777 },
{ FILE_TYPE_DIR, "self", 0755},
{ FILE_TYPE_DIR, "run", 0755},
{ FILE_TYPE_DIR, "run/host", 0755},
{ FILE_TYPE_DIR, "run/dbus", 0755},
{ FILE_TYPE_DIR, "run/media", 0755},
{ FILE_TYPE_DIR, "run/user", 0755},
{ FILE_TYPE_DIR, "run/user/%1$d", 0700, NULL},
{ FILE_TYPE_DIR, "run/user/%1$d/pulse", 0700, NULL},
{ FILE_TYPE_DIR, "run/user/%1$d/dconf", 0700, NULL},
{ FILE_TYPE_DIR, "run/user/%1$d/xdg-app-monitor", 0700, NULL},
{ FILE_TYPE_REGULAR, "run/user/%1$d/pulse/native", 0700, NULL},
{ FILE_TYPE_DIR, "var", 0755},
{ FILE_TYPE_SYMLINK, "var/tmp", 0755, "/tmp"},
{ FILE_TYPE_SYMLINK, "var/run", 0755, "/run"},
{ FILE_TYPE_SYSTEM_SYMLINK, "lib32", 0755, NULL},
{ FILE_TYPE_SYSTEM_SYMLINK, "lib64", 0755, NULL},
{ FILE_TYPE_SYSTEM_SYMLINK, "lib", 0755, "usr/lib"},
{ FILE_TYPE_SYSTEM_SYMLINK, "bin", 0755, "usr/bin" },
{ FILE_TYPE_SYSTEM_SYMLINK, "sbin", 0755, "usr/sbin"},
{ FILE_TYPE_SYMLINK, "etc", 0755, "usr/etc", 0, &create_etc_symlink},
{ FILE_TYPE_DIR, "etc", 0755, NULL, 0, &create_etc_dir},
{ FILE_TYPE_REGULAR, "etc/passwd", 0755, NULL, 0, &create_etc_dir},
{ FILE_TYPE_REGULAR, "etc/group", 0755, NULL, 0, &create_etc_dir},
{ FILE_TYPE_SYMLINK, "etc/resolv.conf", 0755, "/run/user/%1$d/xdg-app-monitor/resolv.conf", 0, &create_monitor_links},
{ FILE_TYPE_REGULAR, "etc/machine-id", 0755, NULL, 0, &create_etc_dir},
{ FILE_TYPE_DIR, "tmp/.X11-unix", 0755 },
{ FILE_TYPE_REGULAR, "tmp/.X11-unix/X99", 0755 },
{ FILE_TYPE_DIR, "proc", 0755},
{ FILE_TYPE_MOUNT, "proc"},
{ FILE_TYPE_BIND_RO, "proc/sys", 0755, "proc/sys"},
{ FILE_TYPE_BIND_RO, "proc/sysrq-trigger", 0755, "proc/sysrq-trigger"},
{ FILE_TYPE_BIND_RO, "proc/irq", 0755, "proc/irq"},
{ FILE_TYPE_BIND_RO, "proc/bus", 0755, "proc/bus"},
{ FILE_TYPE_DIR, "sys", 0755},
{ FILE_TYPE_MOUNT, "sys"},
{ FILE_TYPE_DIR, "dev", 0755},
{ FILE_TYPE_MOUNT, "dev"},
{ FILE_TYPE_DIR, "dev/pts", 0755},
{ FILE_TYPE_MOUNT, "dev/pts"},
{ FILE_TYPE_DIR, "dev/shm", 0755},
{ FILE_TYPE_SHM, "dev/shm"},
{ FILE_TYPE_DEVICE, "dev/null", 0666},
{ FILE_TYPE_DEVICE, "dev/zero", 0666},
{ FILE_TYPE_DEVICE, "dev/full", 0666},
{ FILE_TYPE_DEVICE, "dev/random", 0666},
{ FILE_TYPE_DEVICE, "dev/urandom", 0666},
{ FILE_TYPE_DEVICE, "dev/tty", 0666},
{ FILE_TYPE_DIR, "dev/dri", 0755},
{ FILE_TYPE_BIND_RO, "dev/dri", 0755, "/dev/dri", FILE_FLAGS_NON_FATAL|FILE_FLAGS_DEVICES, &allow_dri},
{ FILE_TYPE_REMOUNT, "dev", MS_RDONLY|MS_NOSUID|MS_NOEXEC},
};
/* warning: Don't create any actual files here, as we could potentially
write over bind mounts to the system */
static const create_table_t create_post[] = {
{ FILE_TYPE_BIND_RO, "etc/passwd", 0444, "/etc/passwd", 0},
{ FILE_TYPE_BIND_RO, "etc/group", 0444, "/etc/group", 0},
{ FILE_TYPE_BIND_RO, "etc/machine-id", 0444, "/etc/machine-id", FILE_FLAGS_NON_FATAL},
{ FILE_TYPE_BIND_RO, "etc/machine-id", 0444, "/var/lib/dbus/machine-id", FILE_FLAGS_NON_FATAL | FILE_FLAGS_IF_LAST_FAILED},
};
static const mount_table_t mount_table[] = {
{ "proc", "proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV },
{ "sysfs", "sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV },
{ "tmpfs", "dev", "tmpfs", "mode=755", MS_NOSUID|MS_STRICTATIME },
{ "devpts", "dev/pts", "devpts","newinstance,ptmxmode=0666,mode=620,gid=5", MS_NOSUID|MS_NOEXEC },
{ "tmpfs", "dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME },
};
const char *dont_mount_in_root[] = {
".", "..", "lib", "lib32", "lib64", "bin", "sbin", "usr", "boot", "root",
"tmp", "etc", "self", "run", "proc", "sys", "dev", "var"
};
typedef enum {
BIND_READONLY = (1<<0),
BIND_PRIVATE = (1<<1),
BIND_DEVICES = (1<<2),
BIND_RECURSIVE = (1<<3),
} bind_option_t;
typedef struct {
char *src;
char *dest;
} ExtraDir;
#define MAX_EXTRA_DIRS 32
#define MAX_LOCK_DIRS (MAX_EXTRA_DIRS+2)
static int n_lock_dirs = 0;
static const char *lock_dirs[MAX_LOCK_DIRS];
static void
lock_dir (const char *dir)
{
char *file = strconcat3 ("/", dir, "/.ref");
struct flock lock = {0};
int fd;
fd = open (file, O_RDONLY | O_CLOEXEC);
free (file);
if (fd != -1)
{
lock.l_type = F_RDLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0;
if (fcntl(fd, F_SETLK, &lock) < 0)
{
printf ("lock failed\n");
close (fd);
}
}
}
static void
add_lock_dir (const char *dir)
{
/* We need to lock the dirs in pid1 because otherwise the
locks are not held by the right process and will not live
for the full duration of the sandbox. */
if (n_lock_dirs < MAX_LOCK_DIRS)
lock_dirs[n_lock_dirs++] = dir;
}
static void
lock_all_dirs (void)
{
int i;
for (i = 0; i < n_lock_dirs; i++)
lock_dir (lock_dirs[i]);
}
static char *
load_file (const char *path)
{
int fd;
char *data;
ssize_t data_read;
ssize_t data_len;
ssize_t res;
fd = open (path, O_CLOEXEC | O_RDONLY);
if (fd == -1)
return NULL;
data_read = 0;
data_len = 4080;
data = xmalloc (data_len);
do
{
if (data_len >= data_read + 1)
{
data_len *= 2;
data = xrealloc (data, data_len);
}
do
res = read (fd, data + data_read, data_len - data_read - 1);
while (res < 0 && errno == EINTR);
if (res < 0)
{
int errsv = errno;
free (data);
errno = errsv;
return NULL;
}
data_read += res;
}
while (res > 0);
data[data_read] = 0;
close (fd);
return data;
}
static char *
skip_line (char *line)
{
while (*line != 0 && *line != '\n')
line++;
if (*line == '\n')
line++;
return line;
}
static char *
skip_token (char *line, bool eat_whitespace)
{
while (*line != ' ' && *line != '\n')
line++;
if (eat_whitespace && *line == ' ')
line++;
return line;
}
static bool
str_has_prefix (const char *str,
const char *prefix)
{
return strncmp (str, prefix, strlen (prefix)) == 0;
}
char **
get_submounts (const char *parent_mount)
{
char *mountpoint, *mountpoint_end;
char **submounts;
int i, n_submounts, submounts_size;
char *mountinfo;
char *line;
mountinfo = load_file ("/proc/self/mountinfo");
if (mountinfo == NULL)
return NULL;
submounts_size = 8;
n_submounts = 0;
submounts = xmalloc (sizeof (char *) * submounts_size);
line = mountinfo;
while (*line != 0)
{
for (i = 0; i < 4; i++)
line = skip_token (line, TRUE);
mountpoint = line;
line = skip_token (line, FALSE);
mountpoint_end = line;
line = skip_line (line);
*mountpoint_end = 0;
if (*mountpoint == '/' &&
str_has_prefix (mountpoint + 1, parent_mount) &&
*(mountpoint + 1 + strlen (parent_mount)) == '/')
{
if (n_submounts + 1 >= submounts_size)
{
submounts_size *= 2;
submounts = xrealloc (submounts, sizeof (char *) * submounts_size);
}
submounts[n_submounts++] = xstrdup (mountpoint + 1);
}
}
submounts[n_submounts] = NULL;
free (mountinfo);
return submounts;
}
static int
bind_mount (const char *src, const char *dest, bind_option_t options)
{
bool readonly = (options & BIND_READONLY) != 0;
bool private = (options & BIND_PRIVATE) != 0;
bool devices = (options & BIND_DEVICES) != 0;
bool recursive = (options & BIND_RECURSIVE) != 0;
char **submounts;
int i;
if (mount (src, dest, NULL, MS_MGC_VAL|MS_BIND|(recursive?MS_REC:0), NULL) != 0)
return 1;
if (private)
{
if (mount ("none", dest,
NULL, MS_REC|MS_PRIVATE, NULL) != 0)
return 2;
}
if (mount ("none", dest,
NULL, MS_MGC_VAL|MS_BIND|MS_REMOUNT|(devices?0:MS_NODEV)|MS_NOSUID|(readonly?MS_RDONLY:0), NULL) != 0)
return 3;
/* We need to work around the fact that a bind mount does not apply the flags, so we need to manually
* apply the flags to all submounts in the recursive case.
* Note: This does not apply the flags to mounts which are later propagated into this namespace.
*/
if (recursive)
{
submounts = get_submounts (dest);
if (submounts == NULL)
return 4;
for (i = 0; submounts[i] != NULL; i++)
{
if (mount ("none", submounts[i],
NULL, MS_MGC_VAL|MS_BIND|MS_REMOUNT|(devices?0:MS_NODEV)|MS_NOSUID|(readonly?MS_RDONLY:0), NULL) != 0)
return 5;
free (submounts[i]);
}
free (submounts);
}
return 0;
}
static int
mkdir_with_parents (const char *pathname,
int mode)
{
char *fn, *p;
struct stat buf;
if (pathname == NULL || *pathname == '\0')
{
errno = EINVAL;
return 1;
}
fn = xstrdup (pathname);
p = fn;
while (*p == '/')
p++;
do
{
while (*p && *p != '/')
p++;
if (!*p)
p = NULL;
else
*p = '\0';
if (stat (fn, &buf) != 0)
{
if (mkdir (fn, mode) == -1 && errno != EEXIST)
{
int errsave = errno;
free (fn);
errno = errsave;
return -1;
}
}
else if (!S_ISDIR (buf.st_mode))
{
free (fn);
errno = ENOTDIR;
return -1;
}
if (p)
{
*p++ = '/';
while (*p && *p == '/')
p++;
}
}
while (p);
free (fn);
return 0;
}
static int
write_to_file (int fd, const char *content)
{
ssize_t len = strlen (content);
ssize_t res;
while (len > 0)
{
res = write (fd, content, len);
if (res < 0 && errno == EINTR)
continue;
if (res <= 0)
return -1;
len -= res;
content += res;
}
return 0;
}
static int
create_file (const char *path, mode_t mode, const char *content)
{
int fd;
int res;
fd = creat (path, mode);
if (fd == -1)
return -1;
res = 0;
if (content)
res = write_to_file (fd, content);
close (fd);
return res;
}
static void
create_files (const create_table_t *create, int n_create, int ignore_shm, int system_mode)
{
bool last_failed = FALSE;
int i;
for (i = 0; i < n_create; i++)
{
char *name;
char *data = NULL;
mode_t mode = create[i].mode;
file_flags_t flags = create[i].flags;
int *option = create[i].option;
char *in_root;
int k;
bool found;
int res;
if ((flags & FILE_FLAGS_IF_LAST_FAILED) &&
!last_failed)
continue;
if (option && !*option)
continue;
name = strdup_printf (create[i].name, getuid());
if (create[i].data)
data = strdup_printf (create[i].data, getuid());
last_failed = FALSE;
switch (create[i].type)
{
case FILE_TYPE_DIR:
if (mkdir (name, mode) != 0)
die_with_error ("creating dir %s", name);
break;
case FILE_TYPE_REGULAR:
if (create_file (name, mode, NULL))
die_with_error ("creating file %s", name);
break;
case FILE_TYPE_SYSTEM_SYMLINK:
if (system_mode)
{
struct stat buf;
in_root = strconcat ("/", name);
if (stat (in_root, &buf) == 0)
{
if (mkdir (name, mode) != 0)
die_with_error ("creating dir %s", name);
if (bind_mount (in_root, name, BIND_PRIVATE | BIND_READONLY))
die_with_error ("mount %s", name);
}
free (in_root);
break;
}
if (data == NULL)
break;
/* else Fall through */
case FILE_TYPE_SYMLINK:
if (symlink (data, name) != 0)
die_with_error ("creating symlink %s", name);
break;
case FILE_TYPE_BIND:
case FILE_TYPE_BIND_RO:
if ((res = bind_mount (data, name,
0 |
((create[i].type == FILE_TYPE_BIND_RO) ? BIND_READONLY : 0) |
((flags & FILE_FLAGS_DEVICES) ? BIND_DEVICES : 0))))
{
if (res > 1 || (flags & FILE_FLAGS_NON_FATAL) == 0)
die_with_error ("mounting bindmount %s", name);
last_failed = TRUE;
}
break;
case FILE_TYPE_SHM:
if (ignore_shm)
break;
/* NOTE: Fall through, treat as mount */
case FILE_TYPE_MOUNT:
found = FALSE;
for (k = 0; k < N_ELEMENTS(mount_table); k++)
{
if (strcmp (mount_table[k].where, name) == 0)
{
if (mount(mount_table[k].what,
mount_table[k].where,
mount_table[k].type,
mount_table[k].flags,
mount_table[k].options) < 0)
die_with_error ("Mounting %s", name);
found = TRUE;
}
}
if (!found)
die ("Unable to find mount %s\n", name);
break;
case FILE_TYPE_REMOUNT:
if (mount ("none", name,
NULL, MS_MGC_VAL|MS_REMOUNT|mode, NULL) != 0)
die_with_error ("Unable to remount %s\n", name);
break;
case FILE_TYPE_DEVICE:
if (create_file (name, mode, NULL))
die_with_error ("creating file %s", name);
in_root = strconcat ("/", name);
if ((res = bind_mount (in_root, name,
BIND_DEVICES)))
{
if (res > 1 || (flags & FILE_FLAGS_NON_FATAL) == 0)
die_with_error ("binding device %s", name);
}
free (in_root);
break;
default:
die ("Unknown create type %d\n", create[i].type);
}
free (name);
free (data);
}
}
static void
link_extra_etc_dirs ()
{
DIR *dir;
struct dirent *dirent;
dir = opendir("usr/etc");
if (dir != NULL)
{
while ((dirent = readdir(dir)))
{
char *dst_path;
char *src_path;
struct stat st;
src_path = strconcat ("etc/", dirent->d_name);
if (stat (src_path, &st) == 0)
{
free (src_path);
continue;
}
dst_path = strconcat ("/usr/etc/", dirent->d_name);
if (symlink (dst_path, src_path) != 0)
die_with_error ("symlink %s", src_path);
free (dst_path);
free (src_path);
}
}
}
static void
mount_extra_root_dirs (int readonly)
{
DIR *dir;
struct dirent *dirent;
int i;
/* Bind mount most dirs in / into the new root */
dir = opendir("/");
if (dir != NULL)
{
while ((dirent = readdir(dir)))
{
bool dont_mount = FALSE;
char *path;
struct stat st;
for (i = 0; i < N_ELEMENTS(dont_mount_in_root); i++)
{
if (strcmp (dirent->d_name, dont_mount_in_root[i]) == 0)
{
dont_mount = TRUE;
break;
}
}
if (dont_mount)
continue;
path = strconcat ("/", dirent->d_name);
if (stat (path, &st) != 0)
{
free (path);
continue;
}
if (S_ISDIR(st.st_mode))
{
if (mkdir (dirent->d_name, 0755) != 0)
die_with_error (dirent->d_name);
if (bind_mount (path, dirent->d_name, BIND_RECURSIVE | (readonly ? BIND_READONLY : 0)))
die_with_error ("mount root subdir %s", dirent->d_name);
}
free (path);
}
}
}
static void
create_homedir (int mount_real_home, const char *app_id)
{
const char *home;
const char *relative_home;
const char *writable_home;
char *app_id_dir;
const char *relative_app_id_dir;
struct stat st;
home = getenv("HOME");
if (home == NULL)
return;
relative_home = home;
while (*relative_home == '/')
relative_home++;
if (mkdir_with_parents (relative_home, 0755))
die_with_error ("unable to create %s", relative_home);
if (mount_real_home)
{
writable_home = home;
if (bind_mount (writable_home, relative_home, BIND_RECURSIVE))
die_with_error ("unable to mount %s", home);
}
else if (app_id != NULL)
{
app_id_dir = strconcat3 (home, "/.var/app/", app_id);
if (stat (app_id_dir, &st) == 0 && S_ISDIR (st.st_mode))
{
relative_app_id_dir = app_id_dir;
while (*relative_app_id_dir == '/')
relative_app_id_dir++;
if (mkdir_with_parents (relative_app_id_dir, 0755))
die_with_error ("unable to create %s", relative_app_id_dir);
if (bind_mount (app_id_dir, relative_app_id_dir, 0))
die_with_error ("unable to mount %s", home);
}
free (app_id_dir);
}
}
static void *
add_rta (struct nlmsghdr *header, int type, size_t size)
{
struct rtattr *rta;
size_t rta_size = RTA_LENGTH(size);
rta = (struct rtattr*)((char *)header + NLMSG_ALIGN(header->nlmsg_len));
rta->rta_type = type;
rta->rta_len = rta_size;
header->nlmsg_len = NLMSG_ALIGN(header->nlmsg_len) + rta_size;
return RTA_DATA(rta);
}
static int
rtnl_send_request (int rtnl_fd, struct nlmsghdr *header)
{
struct sockaddr_nl dst_addr = { AF_NETLINK, 0 };
ssize_t sent;
sent = sendto (rtnl_fd, (void *)header, header->nlmsg_len, 0,
(struct sockaddr *)&dst_addr, sizeof (dst_addr));
if (sent < 0)
return 1;
return 0;
}
static int
rtnl_read_reply (int rtnl_fd, int seq_nr)
{
char buffer[1024];
ssize_t received;
struct nlmsghdr *rheader;
while (1)
{
received = recv (rtnl_fd, buffer, sizeof(buffer), 0);
if (received < 0)
return 1;
rheader = (struct nlmsghdr *)buffer;
while (received >= NLMSG_HDRLEN)
{
if (rheader->nlmsg_seq != seq_nr)
return 1;
if (rheader->nlmsg_pid != getpid ())
return 1;
if (rheader->nlmsg_type == NLMSG_ERROR)
{
uint32_t *err = NLMSG_DATA(rheader);
if (*err == 0)
return 0;
return 1;
}
if (rheader->nlmsg_type == NLMSG_DONE)
return 0;
rheader = NLMSG_NEXT(rheader, received);
}
}
}
static int
rtnl_do_request (int rtnl_fd, struct nlmsghdr *header)
{
if (!rtnl_send_request (rtnl_fd, header))
return 1;
if (!rtnl_read_reply (rtnl_fd, header->nlmsg_seq))
return 1;
return 0;
}
static struct nlmsghdr *
rtnl_setup_request (char *buffer, int type, int flags, size_t size)
{
struct nlmsghdr *header;
size_t len = NLMSG_LENGTH (size);
static uint32_t counter = 0;
memset (buffer, 0, len);
header = (struct nlmsghdr *)buffer;
header->nlmsg_len = len;
header->nlmsg_type = type;
header->nlmsg_flags = flags | NLM_F_REQUEST;
header->nlmsg_seq = counter++;
header->nlmsg_pid = getpid ();
return (struct nlmsghdr *)header;
}
static int
loopback_setup (void)
{
int r, if_loopback;
int rtnl_fd = -1;
char buffer[1024];
struct sockaddr_nl src_addr = { AF_NETLINK, 0 };
struct nlmsghdr *header;
struct ifaddrmsg *addmsg;
struct ifinfomsg *infomsg;
struct in_addr *ip_addr;
int res = 1;
src_addr.nl_pid = getpid ();
if_loopback = (int) if_nametoindex ("lo");
if (if_loopback <= 0)
goto error;
rtnl_fd = socket (PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE);
if (rtnl_fd < 0)
goto error;
r = bind (rtnl_fd, (struct sockaddr *)&src_addr, sizeof (src_addr));
if (r < 0)
goto error;
header = rtnl_setup_request (buffer, RTM_NEWADDR,
NLM_F_CREATE|NLM_F_EXCL|NLM_F_ACK,
sizeof (struct ifaddrmsg));
addmsg = NLMSG_DATA(header);
addmsg->ifa_family = AF_INET;
addmsg->ifa_prefixlen = 8;
addmsg->ifa_flags = IFA_F_PERMANENT;
addmsg->ifa_scope = RT_SCOPE_HOST;
addmsg->ifa_index = if_loopback;
ip_addr = add_rta (header, IFA_LOCAL, sizeof (*ip_addr));
ip_addr->s_addr = htonl(INADDR_LOOPBACK);
ip_addr = add_rta (header, IFA_ADDRESS, sizeof (*ip_addr));
ip_addr->s_addr = htonl(INADDR_LOOPBACK);
assert (header->nlmsg_len < sizeof (buffer));
if (rtnl_do_request (rtnl_fd, header))
goto error;
header = rtnl_setup_request (buffer, RTM_NEWLINK,
NLM_F_ACK,
sizeof (struct ifinfomsg));
infomsg = NLMSG_DATA(header);
infomsg->ifi_family = AF_UNSPEC;
infomsg->ifi_type = 0;
infomsg->ifi_index = if_loopback;
infomsg->ifi_flags = IFF_UP;
infomsg->ifi_change = IFF_UP;
assert (header->nlmsg_len < sizeof (buffer));
if (rtnl_do_request (rtnl_fd, header))
goto error;
res = 0;
error:
if (rtnl_fd != -1)
close (rtnl_fd);
return res;
}
static void
block_sigchild (void)
{
sigset_t mask;
sigemptyset (&mask);
sigaddset (&mask, SIGCHLD);
if (sigprocmask (SIG_BLOCK, &mask, NULL) == -1)
die_with_error ("sigprocmask");
}
/* This stays around for as long as the initial process in the app does
* and when that exits it exits, propagating the exit status. We do this
* by having pid1 in the sandbox detect this exit and tell the monitor
* the exit status via a eventfd. We also track the exit of the sandbox
* pid1 via a signalfd for SIGCHLD, and exit with an error in this case.
* This is to catch e.g. problems during setup. */
static void
monitor_child (int event_fd)
{
int res;
uint64_t val;
ssize_t s;
int signal_fd;
sigset_t mask;
struct pollfd fds[2];
struct signalfd_siginfo fdsi;
sigemptyset (&mask);
sigaddset (&mask, SIGCHLD);
signal_fd = signalfd (-1, &mask, SFD_CLOEXEC | SFD_NONBLOCK);
if (signal_fd == -1)
die_with_error ("signalfd");
fds[0].fd = event_fd;
fds[0].events = POLLIN;
fds[1].fd = signal_fd;
fds[1].events = POLLIN;
while (1)
{
fds[0].revents = fds[1].revents = 0;
res = poll (fds, 2, -1);
if (res == -1 && errno != EINTR)
die_with_error ("poll");
s = read (event_fd, &val, 8);
if (s == -1 && errno != EINTR && errno != EAGAIN)
die_with_error ("read eventfd");
else if (s == 8)
exit ((int)val - 1);
s = read (signal_fd, &fdsi, sizeof (struct signalfd_siginfo));
if (s == -1 && errno != EINTR && errno != EAGAIN)
die_with_error ("read signalfd");
else if (s == sizeof(struct signalfd_siginfo))
{
if (fdsi.ssi_signo != SIGCHLD)
die ("Read unexpected signal\n");
exit (1);
}
}
}
/* This is pid1 in the app sandbox. It is needed because we're using
* pid namespaces, and someone has to reap zombies in it. We also detect
* when the initial process (pid 2) dies and report its exit status to
* the monitor so that it can return it to the original spawner.
*
* When there are no other processes in the sandbox the wait will return
* ECHILD, and we then exit pid1 to clean up the sandbox. */
static int
do_init (int event_fd, pid_t initial_pid)
{
int initial_exit_status = 1;
/* Grab a read on all .ref files to make it possible to detect that
it is in use. This lock will automatically go away when this
process dies */
lock_all_dirs ();
while (1)
{
pid_t child;
int status;
child = wait (&status);
if (child == initial_pid)
{
uint64_t val;
if (WIFEXITED (status))
initial_exit_status = WEXITSTATUS(status);
val = initial_exit_status + 1;
write (event_fd, &val, 8);
}
if (child == -1 && errno != EINTR)
{
if (errno != ECHILD)
die_with_error ("init wait()");
break;
}
}
return initial_exit_status;
}
#define REQUIRED_CAPS (CAP_TO_MASK(CAP_SYS_ADMIN))
static void
acquire_caps (void)
{
struct __user_cap_header_struct hdr;
struct __user_cap_data_struct data;
if (getuid () != geteuid ())
{
/* Tell kernel not clear capabilities when dropping root */
if (prctl (PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0)
die_with_error ("prctl(PR_SET_KEEPCAPS) failed");
/* Drop root uid, but retain the required permitted caps */
if (setuid (getuid ()) < 0)
die_with_error ("unable to drop privs");
}
memset (&hdr, 0, sizeof(hdr));
hdr.version = _LINUX_CAPABILITY_VERSION;
/* Drop all non-require capabilities */
data.effective = REQUIRED_CAPS;
data.permitted = REQUIRED_CAPS;
data.inheritable = 0;
if (capset (&hdr, &data) < 0)
die_with_error ("capset failed");
}
static void
drop_caps (void)
{
struct __user_cap_header_struct hdr;
struct __user_cap_data_struct data;
memset (&hdr, 0, sizeof(hdr));
hdr.version = _LINUX_CAPABILITY_VERSION;
data.effective = 0;
data.permitted = 0;
data.inheritable = 0;
if (capset (&hdr, &data) < 0)
die_with_error ("capset failed");
}
int
main (int argc,
char **argv)
{
mode_t old_umask;
char *newroot;
char *runtime_path = NULL;
char *app_path = NULL;
char *monitor_path = NULL;
char *app_id = NULL;
char *var_path = NULL;
ExtraDir extra_dirs[MAX_EXTRA_DIRS];
int n_extra_dirs = 0;
char *pulseaudio_socket = NULL;
char *x11_socket = NULL;
char *wayland_socket = NULL;
char *system_dbus_socket = NULL;
char *session_dbus_socket = NULL;
char *xdg_runtime_dir;
char *tz_val;
char **args;
char *tmp;
int n_args;
bool system_mode = FALSE;
bool share_shm = FALSE;
bool network = FALSE;
bool ipc = FALSE;
bool mount_host_fs = FALSE;
bool mount_host_fs_ro = FALSE;
bool mount_home = FALSE;
bool lock_files = FALSE;
bool writable = FALSE;
bool writable_app = FALSE;
bool writable_exports = FALSE;
char old_cwd[256];
int c, i;
pid_t pid;
int event_fd;
/* Get the capabilities we need, drop root */
acquire_caps ();
/* Never gain any more privs during exec */
if (prctl (PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0)
die_with_error ("prctl(PR_SET_NO_NEW_CAPS) failed");
while ((c = getopt (argc, argv, "+inWweEsfFHa:m:b:p:x:ly:d:D:v:I:g")) >= 0)
{
switch (c)
{
case 'a':
app_path = optarg;
break;
case 'b':
tmp = strchr (optarg, '=');
if (tmp == NULL || tmp[1] == 0)
usage (argv);
*tmp = 0;
tmp = tmp + 1;
if (n_extra_dirs == MAX_EXTRA_DIRS)
die ("Too many extra directories");
if (strncmp (optarg, "/usr/", strlen ("/usr/")) != 0 &&
strncmp (optarg, "/self/", strlen ("/self/")) != 0 &&
strncmp (optarg, "/run/host/", strlen ("/run/host/")) != 0)
die ("Extra directories must be in /usr, /self or /run/host");
extra_dirs[n_extra_dirs].dest = optarg + 1;
extra_dirs[n_extra_dirs].src = tmp;
n_extra_dirs++;
break;
case 'd':
session_dbus_socket = optarg;
break;
case 'D':
system_dbus_socket = optarg;
break;
case 'e':
writable_exports = TRUE;
break;
case 'E':
create_etc_symlink = TRUE;
create_etc_dir = FALSE;
break;
case 'f':
mount_host_fs = TRUE;
break;
case 'F':
mount_host_fs = TRUE;
mount_host_fs_ro = TRUE;
break;
case 'g':
allow_dri = TRUE;
break;
case 'H':
mount_home = TRUE;
break;
case 'i':
ipc = TRUE;
break;
case 'I':
app_id = optarg;
break;
case 'l':
lock_files = TRUE;
break;
case 'm':
monitor_path = optarg;
break;
case 'n':
network = TRUE;
break;
case 'p':
pulseaudio_socket = optarg;
break;
case 's':
share_shm = TRUE;
break;
case 'v':
var_path = optarg;
break;
case 'w':
writable_app = TRUE;
break;
case 'W':
writable = TRUE;
break;
case 'x':
x11_socket = optarg;
break;
case 'y':
wayland_socket = optarg;
break;
default: /* '?' */
usage (argv);
}
}
args = &argv[optind];
n_args = argc - optind;
if (monitor_path != NULL && create_etc_dir)
create_monitor_links = TRUE;
if (n_args < 2)
usage (argv);
runtime_path = args[0];
args++;
n_args--;
if (strcmp (runtime_path, "/usr") == 0)
system_mode = TRUE;
/* The initial code is run with high permissions
(at least CAP_SYS_ADMIN), so take lots of care. */
__debug__(("Creating xdg-app-root dir\n"));
newroot = strdup_printf ("/run/user/%d/.xdg-app-root", getuid());
if (mkdir (newroot, 0755) && errno != EEXIST)
{
free (newroot);
newroot = strdup_printf ("/tmp/.xdg-app-root", getuid());
if (mkdir (newroot, 0755) && errno != EEXIST)
die_with_error ("Creating xdg-app-root failed");
}
__debug__(("creating new namespace\n"));
event_fd = eventfd (0, EFD_CLOEXEC | EFD_NONBLOCK);
block_sigchild (); /* Block before we clone to avoid races */
pid = raw_clone (SIGCHLD | CLONE_NEWNS | CLONE_NEWPID |
(network ? 0 : CLONE_NEWNET) |
(ipc ? 0 : CLONE_NEWIPC),
NULL);
if (pid == -1)
die_with_error ("Creating new namespace failed");
if (pid != 0)
{
/* Drop all extra caps in the monitor child process */
drop_caps ();
monitor_child (event_fd);
exit (0); /* Should not be reached, but better safe... */
}
old_umask = umask (0);
/* Mark everything as slave, so that we still
* receive mounts from the real root, but don't
* propagate mounts to the real root. */
if (mount (NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)
die_with_error ("Failed to make / slave");
/* Create a tmpfs which we will use as / in the namespace */
if (mount ("", newroot, "tmpfs", MS_NODEV|MS_NOEXEC|MS_NOSUID, NULL) != 0)
die_with_error ("Failed to mount tmpfs");
getcwd (old_cwd, sizeof (old_cwd));
if (chdir (newroot) != 0)
die_with_error ("chdir");
create_files (create, N_ELEMENTS (create), share_shm, system_mode);
if (share_shm)
{
if (bind_mount ("/dev/shm", "dev/shm", BIND_DEVICES))
die_with_error ("mount /dev/shm");
}
if (bind_mount (runtime_path, "usr", BIND_PRIVATE | (writable?0:BIND_READONLY)))
die_with_error ("mount usr");
if (lock_files)
add_lock_dir ("usr");
if (app_path != NULL)
{
if (bind_mount (app_path, "self", BIND_PRIVATE | (writable_app?0:BIND_READONLY)))
die_with_error ("mount self");
if (lock_files)
add_lock_dir ("self");
if (!writable_app && writable_exports)
{
char *exports = strconcat (app_path, "/exports");
if (bind_mount (exports, "self/exports", BIND_PRIVATE))
die_with_error ("mount self/exports");
free (exports);
}
}
for (i = 0; i < n_extra_dirs; i++)
{
if (mkdir_with_parents (extra_dirs[i].dest, 0755))
die_with_error ("create extra dir %s", extra_dirs[i].dest);
if (bind_mount (extra_dirs[i].src, extra_dirs[i].dest, BIND_PRIVATE | BIND_READONLY))
die_with_error ("mount extra dir %s", extra_dirs[i].src);
if (lock_files)
add_lock_dir (extra_dirs[i].dest);
}
if (var_path != NULL)
{
if (bind_mount (var_path, "var", BIND_PRIVATE))
die_with_error ("mount var");
}
create_files (create_post, N_ELEMENTS (create_post), share_shm, system_mode);
if (create_etc_dir)
link_extra_etc_dirs ();
if (monitor_path)
{
char *monitor_mount_path = strdup_printf ("run/user/%d/xdg-app-monitor", getuid());
if (bind_mount (monitor_path, monitor_mount_path, BIND_READONLY))
die ("can't bind monitor dir");
free (monitor_mount_path);
}
/* Bind mount in X socket
* This is a bit iffy, as Xlib typically uses abstract unix domain sockets
* to connect to X, but that is not namespaced. We instead set DISPLAY=99
* and point /tmp/.X11-unix/X99 to the right X socket. Any Xserver listening
* to global abstract unix domain sockets are still accessible to the app
* though...
*/
if (x11_socket)
{
struct stat st;
if (stat (x11_socket, &st) == 0 && S_ISSOCK (st.st_mode))
{
if (bind_mount (x11_socket, "tmp/.X11-unix/X99", 0))
die ("can't bind X11 socket");
xsetenv ("DISPLAY", ":99.0", 1);
}
else
{
xunsetenv ("DISPLAY");
}
}
/* Bind mount in the Wayland socket */
if (wayland_socket != 0)
{
char *wayland_path_relative = strdup_printf ("run/user/%d/wayland-0", getuid());
if (create_file (wayland_path_relative, 0666, NULL) ||
bind_mount (wayland_socket, wayland_path_relative, 0))
die ("can't bind Wayland socket %s -> %s: %s", wayland_socket, wayland_path_relative, strerror (errno));
free (wayland_path_relative);
}
if (pulseaudio_socket != NULL)
{
char *pulse_path_relative = strdup_printf ("run/user/%d/pulse/native", getuid());
char *pulse_server = strdup_printf ("unix:/run/user/%d/pulse/native", getuid());
char *config_path_relative = strdup_printf ("run/user/%d/pulse/config", getuid());
char *config_path_absolute = strdup_printf ("/run/user/%d/pulse/config", getuid());
char *client_config = strdup_printf ("enable-shm=%s\n", share_shm ? "yes" : "no");
if (create_file (config_path_relative, 0666, client_config) == 0 &&
bind_mount (pulseaudio_socket, pulse_path_relative, BIND_READONLY) == 0)
{
xsetenv ("PULSE_SERVER", pulse_server, 1);
xsetenv ("PULSE_CLIENTCONFIG", config_path_absolute, 1);
}
else
{
xunsetenv ("PULSE_SERVER");
}
free (pulse_path_relative);
free (pulse_server);
free (config_path_relative);
free (config_path_absolute);
free (client_config);
}
if (system_dbus_socket != NULL)
{
if (create_file ("run/dbus/system_bus_socket", 0666, NULL) == 0 &&
bind_mount (system_dbus_socket, "run/dbus/system_bus_socket", 0) == 0)
xsetenv ("DBUS_SYSTEM_BUS_ADDRESS", "unix:path=/var/run/dbus/system_bus_socket", 1);
else
xunsetenv ("DBUS_SYSTEM_BUS_ADDRESS");
}
if (session_dbus_socket != NULL)
{
char *session_dbus_socket_path_relative = strdup_printf ("run/user/%d/bus", getuid());
char *session_dbus_address = strdup_printf ("unix:path=/run/user/%d/bus", getuid());
if (create_file (session_dbus_socket_path_relative, 0666, NULL) == 0 &&
bind_mount (session_dbus_socket, session_dbus_socket_path_relative, 0) == 0)
xsetenv ("DBUS_SESSION_BUS_ADDRESS", session_dbus_address, 1);
else
xunsetenv ("DBUS_SESSION_BUS_ADDRESS");
free (session_dbus_socket_path_relative);
free (session_dbus_address);
}
if (mount_host_fs || mount_home)
{
char *dconf_run_path_relative = strdup_printf ("run/user/%d/dconf", getuid());
char *dconf_run_path_absolute = strdup_printf ("/run/user/%d/dconf", getuid());
bind_mount (dconf_run_path_absolute, dconf_run_path_relative, 0);
}
if (mount_host_fs)
{
mount_extra_root_dirs (mount_host_fs_ro);
bind_mount ("/run/media", "run/media", BIND_RECURSIVE | (mount_host_fs_ro ? BIND_READONLY : 0));
}
if (!mount_host_fs)
create_homedir (mount_home, app_id);
if (!network)
loopback_setup ();
if (pivot_root (newroot, ".oldroot"))
die_with_error ("pivot_root");
chdir ("/");
/* The old root better be rprivate or we will send unmount events to the parent namespace */
if (mount (".oldroot", ".oldroot", NULL, MS_REC|MS_PRIVATE, NULL) != 0)
die_with_error ("Failed to make old root rprivate");
if (umount2 (".oldroot", MNT_DETACH))
die_with_error ("unmount oldroot");
umask (old_umask);
/* Now we have everything we need CAP_SYS_ADMIN for, so drop it */
drop_caps ();
chdir (old_cwd);
xsetenv ("PATH", "/self/bin:/usr/bin", 1);
xsetenv ("LD_LIBRARY_PATH", "/self/lib", 1);
xsetenv ("XDG_CONFIG_DIRS","/self/etc/xdg:/etc/xdg", 1);
xsetenv ("XDG_DATA_DIRS", "/self/share:/usr/share", 1);
xsetenv ("GI_TYPELIB_PATH", "/self/lib/girepository-1.0", 1);
xdg_runtime_dir = strdup_printf ("/run/user/%d", getuid());
xsetenv ("XDG_RUNTIME_DIR", xdg_runtime_dir, 1);
free (xdg_runtime_dir);
if (monitor_path)
{
tz_val = strdup_printf (":/run/user/%d/xdg-app-monitor/localtime", getuid());
xsetenv ("TZ", tz_val, 0);
free (tz_val);
}
__debug__(("forking for child\n"));
pid = fork ();
if (pid == -1)
die_with_error("Can't fork for child");
if (pid == 0)
{
__debug__(("launch executable %s\n", args[0]));
if (execvp (args[0], args) == -1)
die_with_error ("execvp %s", args[0]);
return 0;
}
strncpy (argv[0], "xdg-app-init\0", strlen (argv[0]));
return do_init (event_fd, pid);
}
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