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dac478c44cee20f584baf9c8fde2a4460839e902
systemd/src/core/exec-invoke.c
Yu Watanabe dac478c44c core: fix typo 
Follow-up for b3415f5dae.
2025-08-26 04:54:19 +09:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <grp.h>
#include <linux/prctl.h>
#include <linux/sched.h>
#include <linux/securebits.h>
#include <poll.h>
#include <sys/eventfd.h>
#include <sys/ioctl.h>
#include <sys/ioprio.h>
#include <sys/keyctl.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/statvfs.h>
#include <unistd.h>
#if HAVE_PAM
#include <security/pam_appl.h>
#endif
#include "sd-messages.h"
#include "apparmor-util.h"
#include "argv-util.h"
#include "ask-password-api.h"
#include "barrier.h"
#include "bitfield.h"
#include "bpf-dlopen.h"
#include "bpf-restrict-fs.h"
#include "btrfs-util.h"
#include "capability-util.h"
#include "cgroup-setup.h"
#include "cgroup.h"
#include "chase.h"
#include "chattr-util.h"
#include "chown-recursive.h"
#include "constants.h"
#include "copy.h"
#include "coredump-util.h"
#include "dissect-image.h"
#include "dynamic-user.h"
#include "env-util.h"
#include "escape.h"
#include "exec-credential.h"
#include "exec-invoke.h"
#include "execute.h"
#include "exit-status.h"
#include "fd-util.h"
#include "fs-util.h"
#include "hexdecoct.h"
#include "hostname-setup.h"
#include "image-policy.h"
#include "io-util.h"
#include "iovec-util.h"
#include "journal-send.h"
#include "manager.h"
#include "memfd-util.h"
#include "mkdir-label.h"
#include "mount-util.h"
#include "namespace-util.h"
#include "nsflags.h"
#include "open-file.h"
#include "osc-context.h"
#include "path-util.h"
#include "percent-util.h"
#include "pidref.h"
#include "proc-cmdline.h"
#include "process-util.h"
#include "psi-util.h"
#include "quota-util.h"
#include "random-util.h"
#include "rlimit-util.h"
#include "seccomp-util.h"
#include "selinux-util.h"
#include "set.h"
#include "signal-util.h"
#include "siphash24.h"
#include "smack-util.h"
#include "socket-util.h"
#include "stat-util.h"
#include "string-table.h"
#include "strv.h"
#include "terminal-util.h"
#include "user-util.h"
#include "utmp-wtmp.h"
#include "vpick.h"
#define IDLE_TIMEOUT_USEC (5*USEC_PER_SEC)
#define IDLE_TIMEOUT2_USEC (1*USEC_PER_SEC)
#define SNDBUF_SIZE (8*1024*1024)
/* Project id range for disk quotas */
#define PROJ_ID_MIN UINT32_C(2147483648)
#define PROJ_ID_MAX UINT32_C(4294967294)
#define PROJ_ID_CLAMP_INTO_QUOTA_RANGE(id) ((uint32_t) ((id) % (PROJ_ID_MAX - PROJ_ID_MIN + 1)) + PROJ_ID_MIN)
static int flag_fds(
const int fds[],
size_t n_socket_fds,
size_t n_fds,
bool nonblock) {
int r;
assert(fds || n_fds == 0);
/* Drops/Sets O_NONBLOCK and FD_CLOEXEC from the file flags.
* O_NONBLOCK only applies to socket activation though. */
for (size_t i = 0; i < n_fds; i++) {
if (i < n_socket_fds) {
r = fd_nonblock(fds[i], nonblock);
if (r < 0)
return r;
}
/* We unconditionally drop FD_CLOEXEC from the fds,
* since after all we want to pass these fds to our
* children */
r = fd_cloexec(fds[i], false);
if (r < 0)
return r;
}
return 0;
}
static int open_null_as(int flags, int nfd) {
int fd;
assert(nfd >= 0);
fd = open("/dev/null", flags|O_NOCTTY);
if (fd < 0)
return -errno;
return move_fd(fd, nfd, false);
}
static int connect_journal_socket(
int fd,
const char *log_namespace,
uid_t uid,
gid_t gid) {
uid_t olduid = UID_INVALID;
gid_t oldgid = GID_INVALID;
const char *j;
int r;
assert(fd >= 0);
j = journal_stream_path(log_namespace);
if (!j)
return -EINVAL;
if (gid_is_valid(gid)) {
oldgid = getgid();
if (setegid(gid) < 0)
return -errno;
}
if (uid_is_valid(uid)) {
olduid = getuid();
if (seteuid(uid) < 0) {
r = -errno;
goto restore_gid;
}
}
r = connect_unix_path(fd, AT_FDCWD, j);
/* If we fail to restore the uid or gid, things will likely fail later on. This should only happen if
an LSM interferes. */
if (uid_is_valid(uid))
(void) seteuid(olduid);
restore_gid:
if (gid_is_valid(gid))
(void) setegid(oldgid);
return r;
}
static int connect_logger_as(
const ExecContext *context,
const ExecParameters *params,
ExecOutput output,
const char *ident,
int nfd,
uid_t uid,
gid_t gid) {
_cleanup_close_ int fd = -EBADF;
int r;
assert(context);
assert(params);
assert(output < _EXEC_OUTPUT_MAX);
assert(ident);
assert(nfd >= 0);
fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (fd < 0)
return -errno;
r = connect_journal_socket(fd, context->log_namespace, uid, gid);
if (r < 0)
return r;
if (shutdown(fd, SHUT_RD) < 0)
return -errno;
(void) fd_inc_sndbuf(fd, SNDBUF_SIZE);
if (dprintf(fd,
"%s\n"
"%s\n"
"%i\n"
"%i\n"
"%i\n"
"%i\n"
"%i\n",
context->syslog_identifier ?: ident,
params->flags & EXEC_PASS_LOG_UNIT ? params->unit_id : "",
context->syslog_priority,
!!context->syslog_level_prefix,
false,
exec_output_is_kmsg(output),
exec_output_is_terminal(output)) < 0)
return -errno;
return move_fd(TAKE_FD(fd), nfd, false);
}
static int open_terminal_as(const char *path, int flags, int nfd) {
int fd;
assert(path);
assert(nfd >= 0);
fd = open_terminal(path, flags | O_NOCTTY);
if (fd < 0)
return fd;
return move_fd(fd, nfd, false);
}
static int acquire_path(const char *path, int flags, mode_t mode) {
_cleanup_close_ int fd = -EBADF;
int r;
assert(path);
if (IN_SET(flags & O_ACCMODE_STRICT, O_WRONLY, O_RDWR))
flags |= O_CREAT;
fd = open(path, flags|O_NOCTTY, mode);
if (fd >= 0)
return TAKE_FD(fd);
if (errno != ENXIO) /* ENXIO is returned when we try to open() an AF_UNIX file system socket on Linux */
return -errno;
/* So, it appears the specified path could be an AF_UNIX socket. Let's see if we can connect to it. */
fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (fd < 0)
return -errno;
r = connect_unix_path(fd, AT_FDCWD, path);
if (IN_SET(r, -ENOTSOCK, -EINVAL))
/* Propagate initial error if we get ENOTSOCK or EINVAL, i.e. we have indication that this
* wasn't an AF_UNIX socket after all */
return -ENXIO;
if (r < 0)
return r;
if ((flags & O_ACCMODE_STRICT) == O_RDONLY)
r = shutdown(fd, SHUT_WR);
else if ((flags & O_ACCMODE_STRICT) == O_WRONLY)
r = shutdown(fd, SHUT_RD);
else
r = 0;
if (r < 0)
return -errno;
return TAKE_FD(fd);
}
static int fixup_input(
const ExecContext *context,
int socket_fd,
bool apply_tty_stdin) {
ExecInput std_input;
assert(context);
std_input = context->std_input;
if (exec_input_is_terminal(std_input) && !apply_tty_stdin)
return EXEC_INPUT_NULL;
if (std_input == EXEC_INPUT_SOCKET && socket_fd < 0)
return EXEC_INPUT_NULL;
if (std_input == EXEC_INPUT_DATA && context->stdin_data_size == 0)
return EXEC_INPUT_NULL;
return std_input;
}
static int fixup_output(ExecOutput output, int socket_fd) {
if (output == EXEC_OUTPUT_SOCKET && socket_fd < 0)
return EXEC_OUTPUT_INHERIT;
return output;
}
static int setup_input(
const ExecContext *context,
const ExecParameters *params,
int socket_fd,
const int named_iofds[static 3]) {
ExecInput i;
int r;
assert(context);
assert(params);
assert(named_iofds);
if (params->stdin_fd >= 0) {
if (dup2(params->stdin_fd, STDIN_FILENO) < 0)
return -errno;
/* Try to make this our controlling tty, if it is a tty */
if (isatty_safe(STDIN_FILENO) && ioctl(STDIN_FILENO, TIOCSCTTY, context->std_input == EXEC_INPUT_TTY_FORCE) < 0)
log_debug_errno(errno, "Failed to make standard input TTY our controlling terminal: %m");
return STDIN_FILENO;
}
i = fixup_input(context, socket_fd, params->flags & EXEC_APPLY_TTY_STDIN);
switch (i) {
case EXEC_INPUT_NULL:
return open_null_as(O_RDONLY, STDIN_FILENO);
case EXEC_INPUT_TTY:
case EXEC_INPUT_TTY_FORCE:
case EXEC_INPUT_TTY_FAIL: {
_cleanup_close_ int tty_fd = -EBADF;
_cleanup_free_ char *resolved = NULL;
const char *tty_path;
tty_path = ASSERT_PTR(exec_context_tty_path(context));
if (tty_is_console(tty_path)) {
r = resolve_dev_console(&resolved);
if (r < 0)
log_debug_errno(r, "Failed to resolve /dev/console, ignoring: %m");
else {
log_debug("Resolved /dev/console to %s", resolved);
tty_path = resolved;
}
}
tty_fd = acquire_terminal(tty_path,
i == EXEC_INPUT_TTY_FAIL ? ACQUIRE_TERMINAL_TRY :
i == EXEC_INPUT_TTY_FORCE ? ACQUIRE_TERMINAL_FORCE :
ACQUIRE_TERMINAL_WAIT,
USEC_INFINITY);
if (tty_fd < 0)
return tty_fd;
r = move_fd(tty_fd, STDIN_FILENO, /* cloexec= */ false);
if (r < 0)
return r;
TAKE_FD(tty_fd);
return r;
}
case EXEC_INPUT_SOCKET:
assert(socket_fd >= 0);
return RET_NERRNO(dup2(socket_fd, STDIN_FILENO));
case EXEC_INPUT_NAMED_FD:
assert(named_iofds[STDIN_FILENO] >= 0);
(void) fd_nonblock(named_iofds[STDIN_FILENO], false);
return RET_NERRNO(dup2(named_iofds[STDIN_FILENO], STDIN_FILENO));
case EXEC_INPUT_DATA: {
int fd;
fd = memfd_new_and_seal("exec-input", context->stdin_data, context->stdin_data_size);
if (fd < 0)
return fd;
return move_fd(fd, STDIN_FILENO, false);
}
case EXEC_INPUT_FILE: {
bool rw;
int fd;
assert(context->stdio_file[STDIN_FILENO]);
rw = (context->std_output == EXEC_OUTPUT_FILE && streq_ptr(context->stdio_file[STDIN_FILENO], context->stdio_file[STDOUT_FILENO])) ||
(context->std_error == EXEC_OUTPUT_FILE && streq_ptr(context->stdio_file[STDIN_FILENO], context->stdio_file[STDERR_FILENO]));
fd = acquire_path(context->stdio_file[STDIN_FILENO], rw ? O_RDWR : O_RDONLY, 0666 & ~context->umask);
if (fd < 0)
return fd;
return move_fd(fd, STDIN_FILENO, false);
}
default:
assert_not_reached();
}
}
static bool can_inherit_stderr_from_stdout(
const ExecContext *context,
ExecOutput o,
ExecOutput e) {
assert(context);
/* Returns true, if given the specified STDERR and STDOUT output we can directly dup() the stdout fd to the
* stderr fd */
if (e == EXEC_OUTPUT_INHERIT)
return true;
if (e != o)
return false;
if (e == EXEC_OUTPUT_NAMED_FD)
return streq_ptr(context->stdio_fdname[STDOUT_FILENO], context->stdio_fdname[STDERR_FILENO]);
if (IN_SET(e, EXEC_OUTPUT_FILE, EXEC_OUTPUT_FILE_APPEND, EXEC_OUTPUT_FILE_TRUNCATE))
return streq_ptr(context->stdio_file[STDOUT_FILENO], context->stdio_file[STDERR_FILENO]);
return true;
}
static int setup_output(
const ExecContext *context,
const ExecParameters *params,
int fileno,
int socket_fd,
const int named_iofds[static 3],
const char *ident,
uid_t uid,
gid_t gid,
dev_t *journal_stream_dev,
ino_t *journal_stream_ino) {
ExecOutput o;
ExecInput i;
int r;
assert(context);
assert(params);
assert(ident);
assert(journal_stream_dev);
assert(journal_stream_ino);
if (fileno == STDOUT_FILENO && params->stdout_fd >= 0) {
if (dup2(params->stdout_fd, STDOUT_FILENO) < 0)
return -errno;
return STDOUT_FILENO;
}
if (fileno == STDERR_FILENO && params->stderr_fd >= 0) {
if (dup2(params->stderr_fd, STDERR_FILENO) < 0)
return -errno;
return STDERR_FILENO;
}
i = fixup_input(context, socket_fd, params->flags & EXEC_APPLY_TTY_STDIN);
o = fixup_output(context->std_output, socket_fd);
// FIXME: we probably should spend some time here to verify that if we inherit an fd from stdin
// (possibly indirect via inheritance from stdout) it is actually opened for write!
if (fileno == STDERR_FILENO) {
ExecOutput e;
e = fixup_output(context->std_error, socket_fd);
/* This expects the input and output are already set up */
/* Don't change the stderr file descriptor if we inherit all
* the way and are not on a tty */
if (e == EXEC_OUTPUT_INHERIT &&
o == EXEC_OUTPUT_INHERIT &&
i == EXEC_INPUT_NULL &&
!exec_input_is_terminal(context->std_input) &&
getppid() != 1)
return fileno;
/* Duplicate from stdout if possible */
if (can_inherit_stderr_from_stdout(context, o, e))
return RET_NERRNO(dup2(STDOUT_FILENO, fileno));
o = e;
} else if (o == EXEC_OUTPUT_INHERIT) {
/* If input got downgraded, inherit the original value */
if (i == EXEC_INPUT_NULL && exec_input_is_terminal(context->std_input))
return open_terminal_as(exec_context_tty_path(context), O_WRONLY, fileno);
/* If the input is connected to anything that's not a /dev/null or a data fd, inherit that... */
if (!IN_SET(i, EXEC_INPUT_NULL, EXEC_INPUT_DATA))
return RET_NERRNO(dup2(STDIN_FILENO, fileno));
/* If we are not started from PID 1 we just inherit STDOUT from our parent process. */
if (getppid() != 1)
return fileno;
/* We need to open /dev/null here anew, to get the right access mode. */
return open_null_as(O_WRONLY, fileno);
}
switch (o) {
case EXEC_OUTPUT_NULL:
return open_null_as(O_WRONLY, fileno);
case EXEC_OUTPUT_TTY:
if (exec_input_is_terminal(i))
return RET_NERRNO(dup2(STDIN_FILENO, fileno));
return open_terminal_as(exec_context_tty_path(context), O_WRONLY, fileno);
case EXEC_OUTPUT_KMSG:
case EXEC_OUTPUT_KMSG_AND_CONSOLE:
case EXEC_OUTPUT_JOURNAL:
case EXEC_OUTPUT_JOURNAL_AND_CONSOLE:
r = connect_logger_as(context, params, o, ident, fileno, uid, gid);
if (r < 0) {
log_warning_errno(r, "Failed to connect %s to the journal socket, ignoring: %m",
fileno == STDOUT_FILENO ? "stdout" : "stderr");
r = open_null_as(O_WRONLY, fileno);
} else {
struct stat st;
/* If we connected this fd to the journal via a stream, patch the device/inode into the passed
* parameters, but only then. This is useful so that we can set $JOURNAL_STREAM that permits
* services to detect whether they are connected to the journal or not.
*
* If both stdout and stderr are connected to a stream then let's make sure to store the data
* about STDERR as that's usually the best way to do logging. */
if (fstat(fileno, &st) >= 0 &&
(*journal_stream_ino == 0 || fileno == STDERR_FILENO)) {
*journal_stream_dev = st.st_dev;
*journal_stream_ino = st.st_ino;
}
}
return r;
case EXEC_OUTPUT_SOCKET:
assert(socket_fd >= 0);
return RET_NERRNO(dup2(socket_fd, fileno));
case EXEC_OUTPUT_NAMED_FD:
assert(named_iofds[fileno] >= 0);
(void) fd_nonblock(named_iofds[fileno], false);
return RET_NERRNO(dup2(named_iofds[fileno], fileno));
case EXEC_OUTPUT_FILE:
case EXEC_OUTPUT_FILE_APPEND:
case EXEC_OUTPUT_FILE_TRUNCATE: {
bool rw;
int fd, flags;
assert(context->stdio_file[fileno]);
rw = context->std_input == EXEC_INPUT_FILE &&
streq_ptr(context->stdio_file[fileno], context->stdio_file[STDIN_FILENO]);
if (rw)
return RET_NERRNO(dup2(STDIN_FILENO, fileno));
flags = O_WRONLY;
if (o == EXEC_OUTPUT_FILE_APPEND)
flags |= O_APPEND;
else if (o == EXEC_OUTPUT_FILE_TRUNCATE)
flags |= O_TRUNC;
fd = acquire_path(context->stdio_file[fileno], flags, 0666 & ~context->umask);
if (fd < 0)
return fd;
return move_fd(fd, fileno, 0);
}
default:
assert_not_reached();
}
}
static int chown_terminal(int fd, uid_t uid) {
int r;
assert(fd >= 0);
/* Before we chown/chmod the TTY, let's ensure this is actually a tty */
if (!isatty_safe(fd))
return 0;
/* This might fail. What matters are the results. */
r = fchmod_and_chown(fd, TTY_MODE, uid, GID_INVALID);
if (r < 0)
return r;
return 1;
}
static int setup_confirm_stdio(
const ExecContext *context,
const char *vc,
int *ret_saved_stdin,
int *ret_saved_stdout) {
_cleanup_close_ int fd = -EBADF, saved_stdin = -EBADF, saved_stdout = -EBADF;
int r;
assert(context);
assert(ret_saved_stdin);
assert(ret_saved_stdout);
saved_stdin = fcntl(STDIN_FILENO, F_DUPFD_CLOEXEC, 3);
if (saved_stdin < 0)
return -errno;
saved_stdout = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 3);
if (saved_stdout < 0)
return -errno;
fd = acquire_terminal(vc, ACQUIRE_TERMINAL_WAIT, DEFAULT_CONFIRM_USEC);
if (fd < 0)
return fd;
_cleanup_close_ int lock_fd = lock_dev_console();
if (lock_fd < 0)
log_debug_errno(lock_fd, "Failed to lock /dev/console, ignoring: %m");
r = chown_terminal(fd, getuid());
if (r < 0)
return r;
r = terminal_reset_defensive(fd, TERMINAL_RESET_SWITCH_TO_TEXT);
if (r < 0)
return r;
r = exec_context_apply_tty_size(context, fd, fd, vc);
if (r < 0)
return r;
r = rearrange_stdio(fd, fd, STDERR_FILENO); /* Invalidates 'fd' also on failure */
TAKE_FD(fd);
if (r < 0)
return r;
*ret_saved_stdin = TAKE_FD(saved_stdin);
*ret_saved_stdout = TAKE_FD(saved_stdout);
return 0;
}
static void write_confirm_error_fd(int err, int fd, const char *unit_id) {
assert(err != 0);
assert(fd >= 0);
assert(unit_id);
errno = abs(err);
if (errno == ETIMEDOUT)
dprintf(fd, "Confirmation question timed out for %s, assuming positive response.\n", unit_id);
else
dprintf(fd, "Couldn't ask confirmation for %s, assuming positive response: %m\n", unit_id);
}
static void write_confirm_error(int err, const char *vc, const char *unit_id) {
_cleanup_close_ int fd = -EBADF;
assert(vc);
fd = open_terminal(vc, O_WRONLY|O_NOCTTY|O_CLOEXEC);
if (fd < 0)
return;
write_confirm_error_fd(err, fd, unit_id);
}
static int restore_confirm_stdio(int *saved_stdin, int *saved_stdout) {
int r = 0;
assert(saved_stdin);
assert(saved_stdout);
release_terminal();
if (*saved_stdin >= 0)
if (dup2(*saved_stdin, STDIN_FILENO) < 0)
r = -errno;
if (*saved_stdout >= 0)
if (dup2(*saved_stdout, STDOUT_FILENO) < 0)
r = -errno;
*saved_stdin = safe_close(*saved_stdin);
*saved_stdout = safe_close(*saved_stdout);
return r;
}
enum {
CONFIRM_PRETEND_FAILURE = -1,
CONFIRM_PRETEND_SUCCESS = 0,
CONFIRM_EXECUTE = 1,
};
static bool confirm_spawn_disabled(void) {
return access("/run/systemd/confirm_spawn_disabled", F_OK) >= 0;
}
static int ask_for_confirmation(const ExecContext *context, const ExecParameters *params, const char *cmdline) {
int saved_stdout = -EBADF, saved_stdin = -EBADF, r;
_cleanup_free_ char *e = NULL;
char c;
assert(context);
assert(params);
/* For any internal errors, assume a positive response. */
r = setup_confirm_stdio(context, params->confirm_spawn, &saved_stdin, &saved_stdout);
if (r < 0) {
write_confirm_error(r, params->confirm_spawn, params->unit_id);
return CONFIRM_EXECUTE;
}
/* confirm_spawn might have been disabled while we were sleeping. */
if (!params->confirm_spawn || confirm_spawn_disabled()) {
r = 1;
goto restore_stdio;
}
e = ellipsize(cmdline, 60, 100);
if (!e) {
log_oom();
r = CONFIRM_EXECUTE;
goto restore_stdio;
}
for (;;) {
r = ask_char(&c, "yfshiDjcn", "Execute %s? [y, f, s – h for help] ", e);
if (r < 0) {
write_confirm_error_fd(r, STDOUT_FILENO, params->unit_id);
r = CONFIRM_EXECUTE;
goto restore_stdio;
}
switch (c) {
case 'c':
printf("Resuming normal execution.\n");
manager_disable_confirm_spawn();
r = 1;
break;
case 'D':
printf(" Unit: %s\n",
params->unit_id);
exec_context_dump(context, stdout, " ");
exec_params_dump(params, stdout, " ");
continue; /* ask again */
case 'f':
printf("Failing execution.\n");
r = CONFIRM_PRETEND_FAILURE;
break;
case 'h':
printf(" c - continue, proceed without asking anymore\n"
" D - dump, show the state of the unit\n"
" f - fail, don't execute the command and pretend it failed\n"
" h - help\n"
" i - info, show a short summary of the unit\n"
" j - jobs, show jobs that are in progress\n"
" s - skip, don't execute the command and pretend it succeeded\n"
" y - yes, execute the command\n");
continue; /* ask again */
case 'i':
printf(" Unit: %s\n"
" Command: %s\n",
params->unit_id, cmdline);
continue; /* ask again */
case 'j':
if (sigqueue(getppid(),
SIGRTMIN+18,
(const union sigval) { .sival_int = MANAGER_SIGNAL_COMMAND_DUMP_JOBS }) < 0)
return -errno;
continue; /* ask again */
case 'n':
/* 'n' was removed in favor of 'f'. */
printf("Didn't understand 'n', did you mean 'f'?\n");
continue; /* ask again */
case 's':
printf("Skipping execution.\n");
r = CONFIRM_PRETEND_SUCCESS;
break;
case 'y':
r = CONFIRM_EXECUTE;
break;
default:
assert_not_reached();
}
break;
}
restore_stdio:
restore_confirm_stdio(&saved_stdin, &saved_stdout);
return r;
}
static int get_fixed_user(
const char *user_or_uid,
bool prefer_nss,
const char **ret_username,
uid_t *ret_uid,
gid_t *ret_gid,
const char **ret_home,
const char **ret_shell) {
int r;
assert(user_or_uid);
assert(ret_username);
r = get_user_creds(&user_or_uid, ret_uid, ret_gid, ret_home, ret_shell,
USER_CREDS_CLEAN|(prefer_nss ? USER_CREDS_PREFER_NSS : 0));
if (r < 0)
return r;
/* user_or_uid is normalized by get_user_creds to username */
*ret_username = user_or_uid;
return 0;
}
static int get_fixed_group(
const char *group_or_gid,
const char **ret_groupname,
gid_t *ret_gid) {
int r;
assert(group_or_gid);
assert(ret_groupname);
r = get_group_creds(&group_or_gid, ret_gid, /* flags = */ 0);
if (r < 0)
return r;
/* group_or_gid is normalized by get_group_creds to groupname */
*ret_groupname = group_or_gid;
return 0;
}
static int get_supplementary_groups(
const ExecContext *c,
const char *user,
gid_t gid,
gid_t **ret_gids) {
int r;
assert(c);
assert(ret_gids);
/*
* If user is given, then lookup GID and supplementary groups list.
* We avoid NSS lookups for gid=0. Also we have to initialize groups
* here and as early as possible so we keep the list of supplementary
* groups of the caller.
*/
bool keep_groups = false;
if (user && gid_is_valid(gid) && gid != 0) {
/* First step, initialize groups from /etc/groups */
if (initgroups(user, gid) < 0)
return -errno;
keep_groups = true;
}
if (strv_isempty(c->supplementary_groups)) {
*ret_gids = NULL;
return 0;
}
/*
* If SupplementaryGroups= was passed then NGROUPS_MAX has to
* be positive, otherwise fail.
*/
errno = 0;
int ngroups_max = (int) sysconf(_SC_NGROUPS_MAX);
if (ngroups_max <= 0)
return errno_or_else(EOPNOTSUPP);
_cleanup_free_ gid_t *l_gids = new(gid_t, ngroups_max);
if (!l_gids)
return -ENOMEM;
int k = 0;
if (keep_groups) {
/*
* Lookup the list of groups that the user belongs to, we
* avoid NSS lookups here too for gid=0.
*/
k = ngroups_max;
if (getgrouplist(user, gid, l_gids, &k) < 0)
return -EINVAL;
}
STRV_FOREACH(i, c->supplementary_groups) {
if (k >= ngroups_max)
return -E2BIG;
const char *g = *i;
r = get_group_creds(&g, l_gids + k, /* flags = */ 0);
if (r < 0)
return r;
k++;
}
if (k == 0) {
*ret_gids = NULL;
return 0;
}
/* Otherwise get the final list of supplementary groups */
gid_t *groups = newdup(gid_t, l_gids, k);
if (!groups)
return -ENOMEM;
*ret_gids = groups;
return k;
}
static int enforce_groups(gid_t gid, const gid_t *supplementary_gids, int ngids) {
int r;
/* Handle SupplementaryGroups= if it is not empty */
if (ngids > 0) {
r = maybe_setgroups(ngids, supplementary_gids);
if (r < 0)
return r;
}
if (gid_is_valid(gid)) {
/* Then set our gids */
if (setresgid(gid, gid, gid) < 0)
return -errno;
}
return 0;
}
static int set_securebits(unsigned bits, unsigned mask) {
unsigned applied;
int current;
current = prctl(PR_GET_SECUREBITS);
if (current < 0)
return -errno;
/* Clear all securebits defined in mask and set bits */
applied = ((unsigned) current & ~mask) | bits;
if ((unsigned) current == applied)
return 0;
if (prctl(PR_SET_SECUREBITS, applied) < 0)
return -errno;
return 1;
}
static int enforce_user(
const ExecContext *context,
uid_t uid,
uint64_t capability_ambient_set) {
int r;
assert(context);
if (!uid_is_valid(uid))
return 0;
/* Sets (but doesn't look up) the UIS and makes sure we keep the capabilities while doing so. For
* setting secure bits the capability CAP_SETPCAP is required, so we also need keep-caps in this
* case. */
if ((capability_ambient_set != 0 || context->secure_bits != 0) && uid != 0) {
/* First step: If we need to keep capabilities but drop privileges we need to make sure we
* keep our caps, while we drop privileges. Add KEEP_CAPS to the securebits */
r = set_securebits(1U << SECURE_KEEP_CAPS, 0);
if (r < 0)
return r;
}
/* Second step: actually set the uids */
if (setresuid(uid, uid, uid) < 0)
return -errno;
/* At this point we should have all necessary capabilities but are otherwise a normal user. However,
* the caps might got corrupted due to the setresuid() so we need clean them up later. This is done
* outside of this call. */
return 0;
}
#if HAVE_PAM
static void pam_response_free_array(struct pam_response *responses, size_t n_responses) {
assert(responses || n_responses == 0);
FOREACH_ARRAY(resp, responses, n_responses)
erase_and_free(resp->resp);
free(responses);
}
typedef struct AskPasswordConvData {
const ExecContext *context;
const ExecParameters *params;
} AskPasswordConvData;
static int ask_password_conv(
int num_msg,
const struct pam_message *msg[],
struct pam_response **ret,
void *userdata) {
AskPasswordConvData *data = ASSERT_PTR(userdata);
bool set_credential_env_var = false;
int r;
assert(num_msg >= 0);
assert(msg);
assert(data->context);
assert(data->params);
size_t n = num_msg;
struct pam_response *responses = new0(struct pam_response, n);
if (!responses)
return PAM_BUF_ERR;
CLEANUP_ARRAY(responses, n, pam_response_free_array);
for (size_t i = 0; i < n; i++) {
const struct pam_message *mi = *msg + i;
switch (mi->msg_style) {
case PAM_PROMPT_ECHO_ON:
case PAM_PROMPT_ECHO_OFF: {
/* Locally set the $CREDENTIALS_DIRECTORY to the credentials directory we just populated */
if (!set_credential_env_var) {
_cleanup_free_ char *creds_dir = NULL;
r = exec_context_get_credential_directory(data->context, data->params, data->params->unit_id, &creds_dir);
if (r < 0)
return log_error_errno(r, "Failed to determine credentials directory: %m");
if (creds_dir) {
if (setenv("CREDENTIALS_DIRECTORY", creds_dir, /* overwrite= */ true) < 0)
return log_error_errno(r, "Failed to set $CREDENTIALS_DIRECTORY: %m");
} else
(void) unsetenv("CREDENTIALS_DIRECTORY");
set_credential_env_var = true;
}
_cleanup_free_ char *credential_name = strjoin("pam.authtok.", data->context->pam_name);
if (!credential_name)
return log_oom();
AskPasswordRequest req = {
.message = mi->msg,
.credential = credential_name,
.tty_fd = -EBADF,
.hup_fd = -EBADF,
.until = usec_add(now(CLOCK_MONOTONIC), 15 * USEC_PER_SEC),
};
_cleanup_strv_free_erase_ char **acquired = NULL;
r = ask_password_auto(
&req,
ASK_PASSWORD_ACCEPT_CACHED|
ASK_PASSWORD_NO_TTY|
(mi->msg_style == PAM_PROMPT_ECHO_ON ? ASK_PASSWORD_ECHO : 0),
&acquired);
if (r < 0) {
log_error_errno(r, "Failed to query for password: %m");
return PAM_CONV_ERR;
}
responses[i].resp = strdup(ASSERT_PTR(acquired[0]));
if (!responses[i].resp) {
log_oom();
return PAM_BUF_ERR;
}
break;
}
case PAM_ERROR_MSG:
log_error("PAM: %s", mi->msg);
break;
case PAM_TEXT_INFO:
log_info("PAM: %s", mi->msg);
break;
default:
return PAM_CONV_ERR;
}
}
*ret = TAKE_PTR(responses);
n = 0;
return PAM_SUCCESS;
}
static int pam_close_session_and_delete_credentials(pam_handle_t *handle, int flags) {
int r, s;
assert(handle);
r = pam_close_session(handle, flags);
if (r != PAM_SUCCESS)
log_debug("pam_close_session() failed: %s", pam_strerror(handle, r));
s = pam_setcred(handle, PAM_DELETE_CRED | flags);
if (s != PAM_SUCCESS)
log_debug("pam_setcred(PAM_DELETE_CRED) failed: %s", pam_strerror(handle, s));
return r != PAM_SUCCESS ? r : s;
}
#endif
static int attach_to_subcgroup(
const ExecContext *context,
const CGroupContext *cgroup_context,
const ExecParameters *params,
const char *prefix) {
_cleanup_free_ char *subgroup = NULL;
int r;
assert(context);
assert(cgroup_context);
assert(params);
/* If we're a control process that needs a subgroup, we've already been spawned into it as otherwise
* we'd violate the "no inner processes" rule, so no need to do anything. */
if (exec_params_needs_control_subcgroup(params))
return 0;
r = exec_params_get_cgroup_path(params, cgroup_context, prefix, &subgroup);
if (r < 0)
return log_error_errno(r, "Failed to acquire cgroup path: %m");
/* No subgroup required? Then there's nothing to do. */
if (r == 0)
return 0;
r = cg_attach(subgroup, 0);
if (r == -EUCLEAN)
return log_error_errno(r,
"Failed to attach process " PID_FMT " to cgroup '%s', "
"because the cgroup or one of its parents or "
"siblings is in the threaded mode.",
getpid_cached(), subgroup);
if (r < 0)
return log_error_errno(r,
"Failed to attach process " PID_FMT " to cgroup %s: %m",
getpid_cached(), subgroup);
return 0;
}
#if HAVE_PAM
static int exec_context_get_tty_for_pam(const ExecContext *context, char **ret) {
_cleanup_free_ char *tty = NULL;
int r;
assert(context);
assert(ret);
/* First, let's get TTY from STDIN. We may already set STDIN in setup_output(). */
r = getttyname_malloc(STDIN_FILENO, &tty);
if (r == -ENOMEM)
return log_oom_debug();
if (r >= 0) {
_cleanup_free_ char *q = path_join("/dev/", tty);
if (!q)
return log_oom_debug();
log_debug("Got TTY '%s' from STDIN.", q);
*ret = TAKE_PTR(q);
return 1;
}
/* Next, let's try to use the TTY specified in TTYPath=. */
const char *t = exec_context_tty_path(context);
if (!t) {
*ret = NULL;
return 0;
}
/* If /dev/console is specified, resolve it. */
if (tty_is_console(t)) {
r = resolve_dev_console(&tty);
if (r < 0) {
log_debug_errno(r, "Failed to resolve /dev/console, ignoring: %m");
*ret = NULL;
return 0;
}
log_debug("Got TTY '%s' from /dev/console.", tty);
*ret = TAKE_PTR(tty);
return 1;
}
/* Otherwise, use the specified TTY as is. */
if (path_startswith(t, "/dev/"))
tty = strdup(t);
else
tty = path_join("/dev/", t);
if (!tty)
return log_oom_debug();
log_debug("Got TTY '%s' from TTYPath= setting.", tty);
*ret = TAKE_PTR(tty);
return 1;
}
#endif
static int setup_pam(
const ExecContext *context,
const CGroupContext *cgroup_context,
ExecParameters *params,
const char *user,
uid_t uid,
gid_t gid,
char ***env, /* updated on success */
const int fds[], size_t n_fds,
bool needs_sandboxing,
int exec_fd) {
#if HAVE_PAM
AskPasswordConvData conv_data = {
.context = context,
.params = params,
};
const struct pam_conv conv = {
.conv = ask_password_conv,
.appdata_ptr = &conv_data,
};
_cleanup_(barrier_destroy) Barrier barrier = BARRIER_NULL;
_cleanup_strv_free_ char **e = NULL;
_cleanup_free_ char *tty = NULL;
pam_handle_t *handle = NULL;
sigset_t old_ss;
int pam_code = PAM_SUCCESS, r;
bool close_session = false;
pid_t parent_pid;
int flags = 0;
assert(context);
assert(params);
assert(user);
assert(uid_is_valid(uid));
assert(gid_is_valid(gid));
assert(fds || n_fds == 0);
assert(env);
/* We set up PAM in the parent process, then fork. The child
* will then stay around until killed via PR_GET_PDEATHSIG or
* systemd via the cgroup logic. It will then remove the PAM
* session again. The parent process will exec() the actual
* daemon. We do things this way to ensure that the main PID
* of the daemon is the one we initially fork()ed. */
r = barrier_create(&barrier);
if (r < 0)
goto fail;
if (log_get_max_level() < LOG_DEBUG)
flags |= PAM_SILENT;
pam_code = pam_start(context->pam_name, user, &conv, &handle);
if (pam_code != PAM_SUCCESS) {
handle = NULL;
goto fail;
}
r = exec_context_get_tty_for_pam(context, &tty);
if (r < 0)
goto fail;
if (r > 0) {
pam_code = pam_set_item(handle, PAM_TTY, tty);
if (pam_code != PAM_SUCCESS)
goto fail;
}
STRV_FOREACH(nv, *env) {
pam_code = pam_putenv(handle, *nv);
if (pam_code != PAM_SUCCESS)
goto fail;
}
pam_code = pam_acct_mgmt(handle, flags);
if (pam_code != PAM_SUCCESS)
goto fail;
pam_code = pam_setcred(handle, PAM_ESTABLISH_CRED | flags);
if (pam_code != PAM_SUCCESS)
log_debug("pam_setcred(PAM_ESTABLISH_CRED) failed, ignoring: %s", pam_strerror(handle, pam_code));
pam_code = pam_open_session(handle, flags);
if (pam_code != PAM_SUCCESS)
goto fail;
close_session = true;
e = pam_getenvlist(handle);
if (!e) {
pam_code = PAM_BUF_ERR;
goto fail;
}
/* Block SIGTERM, so that we know that it won't get lost in the child */
assert_se(sigprocmask_many(SIG_BLOCK, &old_ss, SIGTERM) >= 0);
parent_pid = getpid_cached();
r = safe_fork("(sd-pam)", 0, NULL);
if (r < 0)
goto fail;
if (r == 0) {
int ret = EXIT_PAM;
if (needs_sandboxing && exec_needs_cgroup_namespace(context) && params->cgroup_path) {
/* Move PAM process into subgroup immediately if the main process hasn't been moved
* into the subgroup yet (when cgroup namespacing is enabled) and a subgroup is
* configured. */
r = attach_to_subcgroup(context, cgroup_context, params, params->cgroup_path);
if (r < 0)
return r;
}
/* The child's job is to reset the PAM session on termination */
barrier_set_role(&barrier, BARRIER_CHILD);
/* Make sure we don't keep open the passed fds in this child. We assume that otherwise only
* those fds are open here that have been opened by PAM. */
(void) close_many(fds, n_fds);
/* Also close the 'exec_fd' in the child, since the service manager waits for the EOF induced
* by the execve() to wait for completion, and if we'd keep the fd open here in the child
* we'd never signal completion. */
exec_fd = safe_close(exec_fd);
/* Drop privileges - we don't need any to pam_close_session and this will make
* PR_SET_PDEATHSIG work in most cases. If this fails, ignore the error - but expect sd-pam
* threads to fail to exit normally */
r = fully_set_uid_gid(uid, gid, /* supplementary_gids= */ NULL, /* n_supplementary_gids= */ 0);
if (r < 0)
log_warning_errno(r, "Failed to drop privileges in sd-pam: %m");
(void) ignore_signals(SIGPIPE);
/* Wait until our parent died. This will only work if the above setresuid() succeeds,
* otherwise the kernel will not allow unprivileged parents kill their privileged children
* this way. We rely on the control groups kill logic to do the rest for us. */
if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
goto child_finish;
/* Tell the parent that our setup is done. This is especially important regarding dropping
* privileges. Otherwise, unit setup might race against our setresuid(2) call.
*
* If the parent aborted, we'll detect this below, hence ignore return failure here. */
(void) barrier_place(&barrier);
/* Check if our parent process might already have died? */
if (getppid() == parent_pid) {
sigset_t ss;
int sig;
assert_se(sigemptyset(&ss) >= 0);
assert_se(sigaddset(&ss, SIGTERM) >= 0);
assert_se(sigwait(&ss, &sig) == 0);
assert(sig == SIGTERM);
}
/* If our parent died we'll end the session */
if (getppid() != parent_pid) {
pam_code = pam_close_session_and_delete_credentials(handle, flags);
if (pam_code != PAM_SUCCESS)
goto child_finish;
}
ret = 0;
child_finish:
/* NB: pam_end() when called in child processes should set PAM_DATA_SILENT to let the module
* know about this. See pam_end(3) */
(void) pam_end(handle, pam_code | flags | PAM_DATA_SILENT);
_exit(ret);
}
barrier_set_role(&barrier, BARRIER_PARENT);
/* If the child was forked off successfully it will do all the cleanups, so forget about the handle
* here. */
handle = NULL;
/* Unblock SIGTERM again in the parent */
assert_se(sigprocmask(SIG_SETMASK, &old_ss, NULL) >= 0);
/* We close the log explicitly here, since the PAM modules might have opened it, but we don't want
* this fd around. */
closelog();
/* Synchronously wait for the child to initialize. We don't care for errors as we cannot
* recover. However, warn loudly if it happens. */
if (!barrier_place_and_sync(&barrier))
log_error("PAM initialization failed");
return strv_free_and_replace(*env, e);
fail:
if (pam_code != PAM_SUCCESS) {
log_error("PAM failed: %s", pam_strerror(handle, pam_code));
r = -EPERM; /* PAM errors do not map to errno */
} else
log_error_errno(r, "PAM failed: %m");
if (handle) {
if (close_session)
pam_code = pam_close_session_and_delete_credentials(handle, flags);
(void) pam_end(handle, pam_code | flags);
}
closelog();
return r;
#else
return 0;
#endif
}
static void rename_process_from_path(const char *path) {
_cleanup_free_ char *buf = NULL;
const char *p;
assert(path);
/* This resulting string must fit in 10 chars (i.e. the length of "/sbin/init") to look pretty in
* /bin/ps */
if (path_extract_filename(path, &buf) < 0) {
rename_process("(...)");
return;
}
size_t l = strlen(buf);
if (l > 8) {
/* The end of the process name is usually more interesting, since the first bit might just be
* "systemd-" */
p = buf + l - 8;
l = 8;
} else
p = buf;
char process_name[11];
process_name[0] = '(';
memcpy(process_name+1, p, l);
process_name[1+l] = ')';
process_name[1+l+1] = 0;
(void) rename_process(process_name);
}
static bool context_has_address_families(const ExecContext *c) {
assert(c);
return c->address_families_allow_list ||
!set_isempty(c->address_families);
}
static bool context_has_syscall_filters(const ExecContext *c) {
assert(c);
return c->syscall_allow_list ||
!hashmap_isempty(c->syscall_filter);
}
static bool context_has_syscall_logs(const ExecContext *c) {
assert(c);
return c->syscall_log_allow_list ||
!hashmap_isempty(c->syscall_log);
}
static bool context_has_seccomp(const ExecContext *c) {
assert(c);
/* We need NNP if we have any form of seccomp and are unprivileged */
return c->lock_personality ||
c->memory_deny_write_execute ||
c->private_devices ||
c->protect_clock ||
c->protect_hostname == PROTECT_HOSTNAME_YES ||
c->protect_kernel_tunables ||
c->protect_kernel_modules ||
c->protect_kernel_logs ||
context_has_address_families(c) ||
exec_context_restrict_namespaces_set(c) ||
c->restrict_realtime ||
c->restrict_suid_sgid ||
!set_isempty(c->syscall_archs) ||
context_has_syscall_filters(c) ||
context_has_syscall_logs(c);
}
static bool context_has_no_new_privileges(const ExecContext *c) {
assert(c);
if (c->no_new_privileges)
return true;
if (have_effective_cap(CAP_SYS_ADMIN) > 0) /* if we are privileged, we don't need NNP */
return false;
return context_has_seccomp(c);
}
#if HAVE_SECCOMP
static bool seccomp_allows_drop_privileges(const ExecContext *c) {
void *id, *val;
bool have_capget = false, have_capset = false, have_prctl = false;
assert(c);
/* No syscall filter, we are allowed to drop privileges */
if (hashmap_isempty(c->syscall_filter))
return true;
HASHMAP_FOREACH_KEY(val, id, c->syscall_filter) {
_cleanup_free_ char *name = NULL;
name = seccomp_syscall_resolve_num_arch(SCMP_ARCH_NATIVE, PTR_TO_INT(id) - 1);
if (streq(name, "capget"))
have_capget = true;
else if (streq(name, "capset"))
have_capset = true;
else if (streq(name, "prctl"))
have_prctl = true;
}
if (c->syscall_allow_list)
return have_capget && have_capset && have_prctl;
else
return !(have_capget || have_capset || have_prctl);
}
static bool skip_seccomp_unavailable(const char *msg) {
assert(msg);
if (is_seccomp_available())
return false;
log_debug("SECCOMP features not detected in the kernel, skipping %s", msg);
return true;
}
static int apply_syscall_filter(const ExecContext *c, const ExecParameters *p) {
uint32_t negative_action, default_action, action;
int r;
assert(c);
assert(p);
if (!context_has_syscall_filters(c))
return 0;
if (skip_seccomp_unavailable("SystemCallFilter="))
return 0;
negative_action = c->syscall_errno == SECCOMP_ERROR_NUMBER_KILL ? scmp_act_kill_process() : SCMP_ACT_ERRNO(c->syscall_errno);
if (c->syscall_allow_list) {
default_action = negative_action;
action = SCMP_ACT_ALLOW;
} else {
default_action = SCMP_ACT_ALLOW;
action = negative_action;
}
/* Sending over exec_fd or handoff_timestamp_fd requires write() syscall. */
if (p->exec_fd >= 0 || p->handoff_timestamp_fd >= 0) {
r = seccomp_filter_set_add_by_name(c->syscall_filter, c->syscall_allow_list, "write");
if (r < 0)
return r;
}
return seccomp_load_syscall_filter_set_raw(default_action, c->syscall_filter, action, false);
}
static int apply_syscall_log(const ExecContext *c, const ExecParameters *p) {
#ifdef SCMP_ACT_LOG
uint32_t default_action, action;
#endif
assert(c);
assert(p);
if (!context_has_syscall_logs(c))
return 0;
#ifdef SCMP_ACT_LOG
if (skip_seccomp_unavailable("SystemCallLog="))
return 0;
if (c->syscall_log_allow_list) {
/* Log nothing but the ones listed */
default_action = SCMP_ACT_ALLOW;
action = SCMP_ACT_LOG;
} else {
/* Log everything but the ones listed */
default_action = SCMP_ACT_LOG;
action = SCMP_ACT_ALLOW;
}
return seccomp_load_syscall_filter_set_raw(default_action, c->syscall_log, action, false);
#else
/* old libseccomp */
log_debug( "SECCOMP feature SCMP_ACT_LOG not available, skipping SystemCallLog=");
return 0;
#endif
}
static int apply_syscall_archs(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (set_isempty(c->syscall_archs))
return 0;
if (skip_seccomp_unavailable("SystemCallArchitectures="))
return 0;
return seccomp_restrict_archs(c->syscall_archs);
}
static int apply_address_families(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (!context_has_address_families(c))
return 0;
if (skip_seccomp_unavailable("RestrictAddressFamilies="))
return 0;
return seccomp_restrict_address_families(c->address_families, c->address_families_allow_list);
}
static int apply_memory_deny_write_execute(const ExecContext *c, const ExecParameters *p) {
int r;
assert(c);
assert(p);
if (!c->memory_deny_write_execute)
return 0;
/* use prctl() if kernel supports it (6.3) */
r = prctl(PR_SET_MDWE, PR_MDWE_REFUSE_EXEC_GAIN, 0, 0, 0);
if (r == 0) {
log_debug("Enabled MemoryDenyWriteExecute= with PR_SET_MDWE");
return 0;
}
if (r < 0 && errno != EINVAL)
return log_debug_errno(errno, "Failed to enable MemoryDenyWriteExecute= with PR_SET_MDWE: %m");
/* else use seccomp */
log_debug("Kernel doesn't support PR_SET_MDWE: falling back to seccomp");
if (skip_seccomp_unavailable("MemoryDenyWriteExecute="))
return 0;
return seccomp_memory_deny_write_execute();
}
static int apply_restrict_realtime(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (!c->restrict_realtime)
return 0;
if (skip_seccomp_unavailable("RestrictRealtime="))
return 0;
return seccomp_restrict_realtime();
}
static int apply_restrict_suid_sgid(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (!c->restrict_suid_sgid)
return 0;
if (skip_seccomp_unavailable("RestrictSUIDSGID="))
return 0;
return seccomp_restrict_suid_sgid();
}
static int apply_protect_sysctl(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
/* Turn off the legacy sysctl() system call. Many distributions turn this off while building the kernel, but
* let's protect even those systems where this is left on in the kernel. */
if (!c->protect_kernel_tunables)
return 0;
if (skip_seccomp_unavailable("ProtectKernelTunables="))
return 0;
return seccomp_protect_sysctl();
}
static int apply_protect_kernel_modules(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
/* Turn off module syscalls on ProtectKernelModules=yes */
if (!c->protect_kernel_modules)
return 0;
if (skip_seccomp_unavailable("ProtectKernelModules="))
return 0;
return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_MODULE, SCMP_ACT_ERRNO(EPERM), false);
}
static int apply_protect_kernel_logs(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (!c->protect_kernel_logs)
return 0;
if (skip_seccomp_unavailable("ProtectKernelLogs="))
return 0;
return seccomp_protect_syslog();
}
static int apply_protect_clock(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (!c->protect_clock)
return 0;
if (skip_seccomp_unavailable("ProtectClock="))
return 0;
return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_CLOCK, SCMP_ACT_ERRNO(EPERM), false);
}
static int apply_private_devices(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
/* If PrivateDevices= is set, also turn off iopl and all @raw-io syscalls. */
if (!c->private_devices)
return 0;
if (skip_seccomp_unavailable("PrivateDevices="))
return 0;
return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_RAW_IO, SCMP_ACT_ERRNO(EPERM), false);
}
static int apply_restrict_namespaces(const ExecContext *c, const ExecParameters *p) {
assert(c);
assert(p);
if (!exec_context_restrict_namespaces_set(c))
return 0;
if (skip_seccomp_unavailable("RestrictNamespaces="))
return 0;
return seccomp_restrict_namespaces(c->restrict_namespaces);
}
static int apply_lock_personality(const ExecContext *c, const ExecParameters *p) {
unsigned long personality;
int r;
assert(c);
assert(p);
if (!c->lock_personality)
return 0;
if (skip_seccomp_unavailable("LockPersonality="))
return 0;
personality = c->personality;
/* If personality is not specified, use either PER_LINUX or PER_LINUX32 depending on what is currently set. */
if (personality == PERSONALITY_INVALID) {
r = opinionated_personality(&personality);
if (r < 0)
return r;
}
return seccomp_lock_personality(personality);
}
#endif
#if HAVE_LIBBPF
static int apply_restrict_filesystems(const ExecContext *c, const ExecParameters *p) {
int r;
assert(c);
assert(p);
if (!exec_context_restrict_filesystems_set(c))
return 0;
if (p->bpf_restrict_fs_map_fd < 0) {
/* LSM BPF is unsupported or lsm_bpf_setup failed */
log_debug("LSM BPF not supported, skipping RestrictFileSystems=");
return 0;
}
/* We are in a new binary, so dl-open again */
r = dlopen_bpf();
if (r < 0)
return r;
return bpf_restrict_fs_update(c->restrict_filesystems, p->cgroup_id, p->bpf_restrict_fs_map_fd, c->restrict_filesystems_allow_list);
}
#endif
static int apply_protect_hostname(const ExecContext *c, const ExecParameters *p, int *ret_exit_status) {
int r;
assert(c);
assert(p);
assert(ret_exit_status);
if (c->protect_hostname == PROTECT_HOSTNAME_NO)
return 0;
if (namespace_type_supported(NAMESPACE_UTS)) {
if (unshare(CLONE_NEWUTS) < 0) {
if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) {
*ret_exit_status = EXIT_NAMESPACE;
return log_error_errno(errno, "Failed to set up UTS namespacing: %m");
}
log_warning("ProtectHostname=%s is configured, but UTS namespace setup is prohibited (container manager?), ignoring namespace setup.",
protect_hostname_to_string(c->protect_hostname));
} else if (c->private_hostname) {
r = sethostname_idempotent(c->private_hostname);
if (r < 0) {
*ret_exit_status = EXIT_NAMESPACE;
return log_error_errno(r, "Failed to set private hostname '%s': %m", c->private_hostname);
}
}
} else
log_warning("ProtectHostname=%s is configured, but the kernel does not support UTS namespaces, ignoring namespace setup.",
protect_hostname_to_string(c->protect_hostname));
#if HAVE_SECCOMP
if (c->protect_hostname == PROTECT_HOSTNAME_YES) {
if (skip_seccomp_unavailable("ProtectHostname="))
return 0;
r = seccomp_protect_hostname();
if (r < 0) {
*ret_exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply hostname restrictions: %m");
}
}
#endif
return 1;
}
static void do_idle_pipe_dance(int idle_pipe[static 4]) {
assert(idle_pipe);
idle_pipe[1] = safe_close(idle_pipe[1]);
idle_pipe[2] = safe_close(idle_pipe[2]);
if (idle_pipe[0] >= 0) {
int r;
r = fd_wait_for_event(idle_pipe[0], POLLHUP, IDLE_TIMEOUT_USEC);
if (idle_pipe[3] >= 0 && r == 0 /* timeout */) {
ssize_t n;
/* Signal systemd that we are bored and want to continue. */
n = write(idle_pipe[3], "x", 1);
if (n > 0)
/* Wait for systemd to react to the signal above. */
(void) fd_wait_for_event(idle_pipe[0], POLLHUP, IDLE_TIMEOUT2_USEC);
}
idle_pipe[0] = safe_close(idle_pipe[0]);
}
idle_pipe[3] = safe_close(idle_pipe[3]);
}
static const char *exec_directory_env_name_to_string(ExecDirectoryType t);
/* And this table also maps ExecDirectoryType, to the environment variable we pass the selected directory to
* the service payload in. */
static const char* const exec_directory_env_name_table[_EXEC_DIRECTORY_TYPE_MAX] = {
[EXEC_DIRECTORY_RUNTIME] = "RUNTIME_DIRECTORY",
[EXEC_DIRECTORY_STATE] = "STATE_DIRECTORY",
[EXEC_DIRECTORY_CACHE] = "CACHE_DIRECTORY",
[EXEC_DIRECTORY_LOGS] = "LOGS_DIRECTORY",
[EXEC_DIRECTORY_CONFIGURATION] = "CONFIGURATION_DIRECTORY",
};
DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(exec_directory_env_name, ExecDirectoryType);
static int build_environment(
const ExecContext *c,
const ExecParameters *p,
const CGroupContext *cgroup_context,
size_t n_fds,
const char *home,
const char *username,
const char *shell,
dev_t journal_stream_dev,
ino_t journal_stream_ino,
const char *memory_pressure_path,
bool needs_sandboxing,
char ***ret) {
_cleanup_strv_free_ char **our_env = NULL;
size_t n_env = 0;
char *x;
int r;
assert(c);
assert(p);
assert(cgroup_context);
assert(ret);
#define N_ENV_VARS 19
our_env = new0(char*, N_ENV_VARS + _EXEC_DIRECTORY_TYPE_MAX + 1);
if (!our_env)
return -ENOMEM;
if (n_fds > 0) {
_cleanup_free_ char *joined = NULL;
if (asprintf(&x, "LISTEN_PID="PID_FMT, getpid_cached()) < 0)
return -ENOMEM;
our_env[n_env++] = x;
if (asprintf(&x, "LISTEN_FDS=%zu", n_fds) < 0)
return -ENOMEM;
our_env[n_env++] = x;
joined = strv_join(p->fd_names, ":");
if (!joined)
return -ENOMEM;
x = strjoin("LISTEN_FDNAMES=", joined);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
if ((p->flags & EXEC_SET_WATCHDOG) && p->watchdog_usec > 0) {
if (asprintf(&x, "WATCHDOG_PID="PID_FMT, getpid_cached()) < 0)
return -ENOMEM;
our_env[n_env++] = x;
if (asprintf(&x, "WATCHDOG_USEC="USEC_FMT, p->watchdog_usec) < 0)
return -ENOMEM;
our_env[n_env++] = x;
}
/* If this is D-Bus, tell the nss-systemd module, since it relies on being able to use blocking
* Varlink calls back to us for look up dynamic users in PID 1. Break the deadlock between D-Bus and
* PID 1 by disabling use of PID1' NSS interface for looking up dynamic users. */
if (p->flags & EXEC_NSS_DYNAMIC_BYPASS) {
x = strdup("SYSTEMD_NSS_DYNAMIC_BYPASS=1");
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
/* We query "root" if this is a system unit and User= is not specified. $USER is always set. $HOME
* could cause problem for e.g. getty, since login doesn't override $HOME, and $LOGNAME and $SHELL don't
* really make much sense since we're not logged in. Hence we conditionalize the three based on
* SetLoginEnvironment= switch. */
if (!username && !c->dynamic_user && p->runtime_scope == RUNTIME_SCOPE_SYSTEM) {
assert(!c->user);
r = get_fixed_user("root", /* prefer_nss = */ false, &username, NULL, NULL, &home, &shell);
if (r < 0)
return log_debug_errno(r, "Failed to determine user credentials for root: %m");
}
bool set_user_login_env = exec_context_get_set_login_environment(c);
if (username) {
x = strjoin("USER=", username);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
if (set_user_login_env) {
x = strjoin("LOGNAME=", username);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
}
/* Note that we don't set $HOME or $SHELL if they are not particularly enlightening anyway
* (i.e. are "/" or "/bin/nologin"). */
if (home && set_user_login_env && !empty_or_root(home)) {
x = strjoin("HOME=", home);
if (!x)
return -ENOMEM;
path_simplify(x + 5);
our_env[n_env++] = x;
}
if (shell && set_user_login_env && !shell_is_placeholder(shell)) {
x = strjoin("SHELL=", shell);
if (!x)
return -ENOMEM;
path_simplify(x + 6);
our_env[n_env++] = x;
}
if (!sd_id128_is_null(p->invocation_id)) {
assert(p->invocation_id_string);
x = strjoin("INVOCATION_ID=", p->invocation_id_string);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
if (journal_stream_dev != 0 && journal_stream_ino != 0) {
if (asprintf(&x, "JOURNAL_STREAM=" DEV_FMT ":" INO_FMT, journal_stream_dev, journal_stream_ino) < 0)
return -ENOMEM;
our_env[n_env++] = x;
}
if (c->log_namespace) {
x = strjoin("LOG_NAMESPACE=", c->log_namespace);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
_cleanup_free_ char *joined = NULL;
const char *n;
if (!p->prefix[t])
continue;
if (c->directories[t].n_items == 0)
continue;
n = exec_directory_env_name_to_string(t);
if (!n)
continue;
for (size_t i = 0; i < c->directories[t].n_items; i++) {
_cleanup_free_ char *prefixed = NULL;
prefixed = path_join(p->prefix[t], c->directories[t].items[i].path);
if (!prefixed)
return -ENOMEM;
if (!strextend_with_separator(&joined, ":", prefixed))
return -ENOMEM;
}
x = strjoin(n, "=", joined);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
_cleanup_free_ char *creds_dir = NULL;
r = exec_context_get_credential_directory(c, p, p->unit_id, &creds_dir);
if (r < 0)
return r;
if (r > 0) {
x = strjoin("CREDENTIALS_DIRECTORY=", creds_dir);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
if (asprintf(&x, "SYSTEMD_EXEC_PID=" PID_FMT, getpid_cached()) < 0)
return -ENOMEM;
our_env[n_env++] = x;
if (memory_pressure_path) {
x = strjoin("MEMORY_PRESSURE_WATCH=", memory_pressure_path);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
if (!path_equal(memory_pressure_path, "/dev/null")) {
_cleanup_free_ char *b = NULL, *e = NULL;
if (asprintf(&b, "%s " USEC_FMT " " USEC_FMT,
MEMORY_PRESSURE_DEFAULT_TYPE,
cgroup_context->memory_pressure_threshold_usec == USEC_INFINITY ? MEMORY_PRESSURE_DEFAULT_THRESHOLD_USEC :
CLAMP(cgroup_context->memory_pressure_threshold_usec, 1U, MEMORY_PRESSURE_DEFAULT_WINDOW_USEC),
MEMORY_PRESSURE_DEFAULT_WINDOW_USEC) < 0)
return -ENOMEM;
if (base64mem(b, strlen(b) + 1, &e) < 0)
return -ENOMEM;
x = strjoin("MEMORY_PRESSURE_WRITE=", e);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
}
if (p->notify_socket) {
x = strjoin("NOTIFY_SOCKET=", exec_get_private_notify_socket_path(c, p, needs_sandboxing) ?: p->notify_socket);
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
assert(c->private_var_tmp >= 0 && c->private_var_tmp < _PRIVATE_TMP_MAX);
if (needs_sandboxing && c->private_tmp != c->private_var_tmp) {
assert(c->private_tmp == PRIVATE_TMP_DISCONNECTED);
assert(c->private_var_tmp == PRIVATE_TMP_NO);
/* When private tmpfs is enabled only on /tmp/, then explicitly set $TMPDIR to suggest the
* service to use /tmp/. */
x = strdup("TMPDIR=/tmp");
if (!x)
return -ENOMEM;
our_env[n_env++] = x;
}
assert(n_env <= N_ENV_VARS + _EXEC_DIRECTORY_TYPE_MAX);
#undef N_ENV_VARS
*ret = TAKE_PTR(our_env);
return 0;
}
static int build_pass_environment(const ExecContext *c, char ***ret) {
_cleanup_strv_free_ char **pass_env = NULL;
size_t n_env = 0;
assert(c);
assert(ret);
STRV_FOREACH(i, c->pass_environment) {
_cleanup_free_ char *x = NULL;
char *v;
v = getenv(*i);
if (!v)
continue;
x = strjoin(*i, "=", v);
if (!x)
return -ENOMEM;
if (!GREEDY_REALLOC(pass_env, n_env + 2))
return -ENOMEM;
pass_env[n_env++] = TAKE_PTR(x);
pass_env[n_env] = NULL;
}
*ret = TAKE_PTR(pass_env);
return 0;
}
static int setup_private_users_child(int unshare_ready_fd, const char *uid_map, const char *gid_map, bool allow_setgroups) {
int r;
/* Child process, running in the original user namespace. Let's update the parent's UID/GID map from
* here, after the parent opened its own user namespace. */
pid_t ppid = getppid();
/* Wait until the parent unshared the user namespace */
uint64_t c;
ssize_t n = read(unshare_ready_fd, &c, sizeof(c));
if (n < 0)
return log_debug_errno(errno, "Failed to read from signaling eventfd: %m");
if (n != sizeof(c))
return log_debug_errno(SYNTHETIC_ERRNO(EIO), "Short read from signaling eventfd.");
/* Disable the setgroups() system call in the child user namespace, for good, unless PrivateUsers=full
* and using the system service manager. */
const char *a = procfs_file_alloca(ppid, "setgroups");
const char *setgroups = allow_setgroups ? "allow" : "deny";
r = write_string_file(a, setgroups, WRITE_STRING_FILE_DISABLE_BUFFER);
if (r < 0)
return log_debug_errno(r, "Failed to write '%s' to %s: %m", setgroups, a);
/* First write the GID map */
a = procfs_file_alloca(ppid, "gid_map");
r = write_string_file(a, gid_map, WRITE_STRING_FILE_DISABLE_BUFFER);
if (r < 0)
return log_debug_errno(r, "Failed to write GID map to %s: %m", a);
/* Then write the UID map */
a = procfs_file_alloca(ppid, "uid_map");
r = write_string_file(a, uid_map, WRITE_STRING_FILE_DISABLE_BUFFER);
if (r < 0)
return log_debug_errno(r, "Failed to write UID map to %s: %m", a);
return 0;
}
static int bpffs_helper(const ExecContext *c, int socket_fd) {
assert(c);
assert(socket_fd >= 0);
_cleanup_close_ int fs_fd = receive_one_fd(socket_fd, /* flags = */ 0);
if (fs_fd < 0)
return log_debug_errno(fs_fd, "Failed to receive file descriptor from parent: %m");
char number[STRLEN("0x") + sizeof(c->bpf_delegate_commands) * 2 + 1];
xsprintf(number, "0x%"PRIx64, c->bpf_delegate_commands);
if (fsconfig(fs_fd, FSCONFIG_SET_STRING, "delegate_cmds", number, /* aux = */ 0) < 0)
return log_debug_errno(errno, "Failed to FSCONFIG_SET_STRING: %m");
xsprintf(number, "0x%"PRIx64, c->bpf_delegate_maps);
if (fsconfig(fs_fd, FSCONFIG_SET_STRING, "delegate_maps", number, /* aux = */ 0) < 0)
return log_debug_errno(errno, "Failed to FSCONFIG_SET_STRING: %m");
xsprintf(number, "0x%"PRIx64, c->bpf_delegate_programs);
if (fsconfig(fs_fd, FSCONFIG_SET_STRING, "delegate_progs", number, /* aux = */ 0) < 0)
return log_debug_errno(errno, "Failed to FSCONFIG_SET_STRING: %m");
xsprintf(number, "0x%"PRIx64, c->bpf_delegate_attachments);
if (fsconfig(fs_fd, FSCONFIG_SET_STRING, "delegate_attachs", number, /* aux = */ 0) < 0)
return log_debug_errno(errno, "Failed to FSCONFIG_SET_STRING: %m");
if (fsconfig(fs_fd, FSCONFIG_CMD_CREATE, /* key = */ NULL, /* value = */ NULL, /* aux = */ 0) < 0)
return log_debug_errno(errno, "Failed to create bpffs superblock: %m");
return 0;
}
static int bpffs_prepare(
const ExecContext *c,
PidRef *ret_pid,
int *ret_sock_fd,
int *ret_errno_pipe) {
_cleanup_close_pair_ int socket_fds[2] = EBADF_PAIR, errno_pipe[2] = EBADF_PAIR;
int r;
assert(ret_sock_fd);
assert(ret_pid);
assert(ret_errno_pipe);
r = pipe2(errno_pipe, O_CLOEXEC|O_NONBLOCK);
if (r < 0)
return log_debug_errno(errno, "Failed to create pipe: %m");
r = socketpair(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC, 0, socket_fds);
if (r < 0)
return log_debug_errno(errno, "Failed to create socket pair: %m");
r = pidref_safe_fork("(sd-bpffs)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL, ret_pid);
if (r < 0)
return log_debug_errno(r, "Failed to fork bpffs privileged helper: %m");
if (r == 0) {
errno_pipe[0] = safe_close(errno_pipe[0]);
socket_fds[0] = safe_close(socket_fds[0]);
report_errno_and_exit(errno_pipe[1], bpffs_helper(c, socket_fds[1]));
}
*ret_sock_fd = TAKE_FD(socket_fds[0]);
*ret_errno_pipe = TAKE_FD(errno_pipe[0]);
return 0;
}
static int setup_private_users(PrivateUsers private_users, uid_t ouid, gid_t ogid, uid_t uid, gid_t gid, bool allow_setgroups) {
_cleanup_free_ char *uid_map = NULL, *gid_map = NULL;
_cleanup_close_pair_ int errno_pipe[2] = EBADF_PAIR;
_cleanup_close_ int unshare_ready_fd = -EBADF;
_cleanup_(sigkill_waitp) pid_t pid = 0;
uint64_t c = 1;
ssize_t n;
int r;
/* Set up a user namespace and map the original UID/GID (IDs from before any user or group changes, i.e.
* the IDs from the user or system manager(s)) to itself, the selected UID/GID to itself, and everything else to
* nobody. In order to be able to write this mapping we need CAP_SETUID in the original user namespace, which
* we however lack after opening the user namespace. To work around this we fork() a temporary child process,
* which waits for the parent to create the new user namespace while staying in the original namespace. The
* child then writes the UID mapping, under full privileges. The parent waits for the child to finish and
* continues execution normally.
* For unprivileged users (i.e. without capabilities), the root to root mapping is excluded. As such, it
* does not need CAP_SETUID to write the single line mapping to itself. */
if (private_users == PRIVATE_USERS_NO)
return 0;
if (private_users == PRIVATE_USERS_IDENTITY) {
uid_map = strdup("0 0 65536\n");
if (!uid_map)
return -ENOMEM;
} else if (private_users == PRIVATE_USERS_FULL) {
/* Map all UID/GID from original to new user namespace. We can't use `0 0 UINT32_MAX` because
* this is the same UID/GID map as the init user namespace and systemd's running_in_userns()
* checks whether its in a user namespace by comparing uid_map/gid_map to `0 0 UINT32_MAX`.
* Thus, we still map all UIDs/GIDs but do it using two extents to differentiate the new user
* namespace from the init namespace:
* 0 0 1
* 1 1 UINT32_MAX - 1
*
* systemd will remove the heuristic in running_in_userns() and use namespace inodes in version 258
* (PR #35382). But some users may be running a container image with older systemd < 258 so we keep
* this uid_map/gid_map hack until version 259 for version N-1 compatibility.
*
* TODO: Switch to `0 0 UINT32_MAX` in systemd v259.
*
* Note the kernel defines the UID range between 0 and UINT32_MAX so we map all UIDs even though
* the UID range beyond INT32_MAX (e.g. i.e. the range above the signed 32-bit range) is
* icky. For example, setfsuid() returns the old UID as signed integer. But units can decide to
* use these UIDs/GIDs so we need to map them. */
r = asprintf(&uid_map, "0 0 1\n"
"1 1 " UID_FMT "\n", (uid_t) (UINT32_MAX - 1));
if (r < 0)
return -ENOMEM;
/* Can only set up multiple mappings with CAP_SETUID. */
} else if (have_effective_cap(CAP_SETUID) > 0 && uid != ouid && uid_is_valid(uid)) {
r = asprintf(&uid_map,
UID_FMT " " UID_FMT " 1\n" /* Map $OUID → $OUID */
UID_FMT " " UID_FMT " 1\n", /* Map $UID → $UID */
ouid, ouid, uid, uid);
if (r < 0)
return -ENOMEM;
} else {
r = asprintf(&uid_map,
UID_FMT " " UID_FMT " 1\n", /* Map $OUID → $OUID */
ouid, ouid);
if (r < 0)
return -ENOMEM;
}
if (private_users == PRIVATE_USERS_IDENTITY) {
gid_map = strdup("0 0 65536\n");
if (!gid_map)
return -ENOMEM;
} else if (private_users == PRIVATE_USERS_FULL) {
r = asprintf(&gid_map, "0 0 1\n"
"1 1 " GID_FMT "\n", (gid_t) (UINT32_MAX - 1));
if (r < 0)
return -ENOMEM;
/* Can only set up multiple mappings with CAP_SETGID. */
} else if (have_effective_cap(CAP_SETGID) > 0 && gid != ogid && gid_is_valid(gid)) {
r = asprintf(&gid_map,
GID_FMT " " GID_FMT " 1\n" /* Map $OGID → $OGID */
GID_FMT " " GID_FMT " 1\n", /* Map $GID → $GID */
ogid, ogid, gid, gid);
if (r < 0)
return -ENOMEM;
} else {
r = asprintf(&gid_map,
GID_FMT " " GID_FMT " 1\n", /* Map $OGID -> $OGID */
ogid, ogid);
if (r < 0)
return -ENOMEM;
}
/* Create a communication channel so that the parent can tell the child when it finished creating the user
* namespace. */
unshare_ready_fd = eventfd(0, EFD_CLOEXEC);
if (unshare_ready_fd < 0)
return -errno;
/* Create a communication channel so that the child can tell the parent a proper error code in case it
* failed. */
if (pipe2(errno_pipe, O_CLOEXEC) < 0)
return -errno;
r = safe_fork("(sd-userns)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL, &pid);
if (r < 0)
return r;
if (r == 0) {
errno_pipe[0] = safe_close(errno_pipe[0]);
r = setup_private_users_child(unshare_ready_fd, uid_map, gid_map, allow_setgroups);
if (r < 0)
report_errno_and_exit(errno_pipe[1], r);
_exit(EXIT_SUCCESS);
}
errno_pipe[1] = safe_close(errno_pipe[1]);
if (unshare(CLONE_NEWUSER) < 0)
return log_debug_errno(errno, "Failed to unshare user namespace: %m");
/* Let the child know that the namespace is ready now */
if (write(unshare_ready_fd, &c, sizeof(c)) < 0)
return -errno;
/* Try to read an error code from the child */
n = read(errno_pipe[0], &r, sizeof(r));
if (n < 0)
return -errno;
if (n == sizeof(r)) { /* an error code was sent to us */
if (r < 0)
return r;
return -EIO;
}
if (n != 0) /* on success we should have read 0 bytes */
return -EIO;
r = wait_for_terminate_and_check("(sd-userns)", TAKE_PID(pid), 0);
if (r < 0)
return r;
if (r != EXIT_SUCCESS) /* If something strange happened with the child, let's consider this fatal, too */
return -EIO;
return 1;
}
static int can_mount_proc(void) {
_cleanup_close_pair_ int errno_pipe[2] = EBADF_PAIR;
_cleanup_(sigkill_waitp) pid_t pid = 0;
ssize_t n;
int r;
/* If running via unprivileged user manager and /proc/ is masked (e.g. /proc/kmsg is over-mounted with tmpfs
* like systemd-nspawn does), then mounting /proc/ will fail with EPERM. This is due to a kernel restriction
* where unprivileged user namespaces cannot mount a less restrictive instance of /proc. */
/* Create a communication channel so that the child can tell the parent a proper error code in case it
* failed. */
if (pipe2(errno_pipe, O_CLOEXEC) < 0)
return log_debug_errno(errno, "Failed to create pipe for communicating with child process (sd-proc-check): %m");
/* Fork a child process into its own mount and PID namespace. Note safe_fork() already remounts / as SLAVE
* with FORK_MOUNTNS_SLAVE. */
r = safe_fork("(sd-proc-check)",
FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL|FORK_NEW_MOUNTNS|FORK_MOUNTNS_SLAVE|FORK_NEW_PIDNS, &pid);
if (r < 0)
return log_debug_errno(r, "Failed to fork child process (sd-proc-check): %m");
if (r == 0) {
errno_pipe[0] = safe_close(errno_pipe[0]);
/* Try mounting /proc on /dev/shm/. No need to clean up the mount since the mount
* namespace will be cleaned up once the process exits. */
r = mount_follow_verbose(LOG_DEBUG, "proc", "/dev/shm/", "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
if (r < 0) {
(void) write(errno_pipe[1], &r, sizeof(r));
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
errno_pipe[1] = safe_close(errno_pipe[1]);
/* Try to read an error code from the child */
n = read(errno_pipe[0], &r, sizeof(r));
if (n < 0)
return log_debug_errno(errno, "Failed to read errno from pipe with child process (sd-proc-check): %m");
if (n == sizeof(r)) { /* an error code was sent to us */
/* This is the expected case where proc cannot be mounted due to permissions. */
if (ERRNO_IS_NEG_PRIVILEGE(r))
return 0;
if (r < 0)
return r;
return -EIO;
}
if (n != 0) /* on success we should have read 0 bytes */
return -EIO;
r = wait_for_terminate_and_check("(sd-proc-check)", TAKE_PID(pid), 0 /* flags= */);
if (r < 0)
return log_debug_errno(r, "Failed to wait for (sd-proc-check) child process to terminate: %m");
if (r != EXIT_SUCCESS) /* If something strange happened with the child, let's consider this fatal, too */
return log_debug_errno(SYNTHETIC_ERRNO(EIO), "Child process (sd-proc-check) exited with unexpected exit status '%d'.", r);
return 1;
}
static int setup_private_pids(const ExecContext *c, ExecParameters *p) {
_cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
_cleanup_close_pair_ int errno_pipe[2] = EBADF_PAIR;
ssize_t n;
int r, q;
assert(c);
assert(p);
assert(p->pidref_transport_fd >= 0);
/* The first process created after unsharing a pid namespace becomes PID 1 in the pid namespace, so
* we have to fork after unsharing the pid namespace to become PID 1. The parent sends the child
* pidref to the manager and exits while the child process continues with the rest of exec_invoke()
* and finally executes the actual payload. */
/* Create a communication channel so that the parent can tell the child a proper error code in case it
* failed to send child pidref to the manager. */
if (pipe2(errno_pipe, O_CLOEXEC) < 0)
return log_debug_errno(errno, "Failed to create pipe for communicating with parent process: %m");
/* Set FORK_DETACH to immediately re-parent the child process to the invoking manager process. */
r = pidref_safe_fork("(sd-pidns-child)", FORK_NEW_PIDNS|FORK_DETACH, &pidref);
if (r < 0)
return log_debug_errno(r, "Failed to fork child into new pid namespace: %m");
if (r > 0) {
errno_pipe[0] = safe_close(errno_pipe[0]);
/* In the parent process, we send the child pidref to the manager and exit.
* If PIDFD is not supported, only the child PID is sent. The server then
* uses the child PID to set the new exec main process. */
q = send_one_fd_iov(
p->pidref_transport_fd,
pidref.fd,
&IOVEC_MAKE(&pidref.pid, sizeof(pidref.pid)),
/*iovlen=*/ 1,
/*flags=*/ 0);
/* Send error code to child process. */
(void) write(errno_pipe[1], &q, sizeof(q));
/* Exit here so we only go through the destructors in exec_invoke only once - in the child - as
* some destructors have external effects. The main codepaths continue in the child process. */
_exit(q < 0 ? EXIT_FAILURE : EXIT_SUCCESS);
}
errno_pipe[1] = safe_close(errno_pipe[1]);
p->pidref_transport_fd = safe_close(p->pidref_transport_fd);
/* Try to read an error code from the parent. Note a child process cannot wait for the parent so we always
* receive an errno even on success. */
n = read(errno_pipe[0], &r, sizeof(r));
if (n < 0)
return log_debug_errno(errno, "Failed to read errno from pipe with parent process: %m");
if (n != sizeof(r))
return log_debug_errno(SYNTHETIC_ERRNO(EIO), "Failed to read enough bytes from pipe with parent process");
if (r < 0)
return log_debug_errno(r, "Failed to send child pidref to manager: %m");
/* NOTE! This function returns in the child process only. */
return r;
}
static int create_many_symlinks(const char *root, const char *source, char **symlinks) {
_cleanup_free_ char *src_abs = NULL;
int r;
assert(source);
src_abs = path_join(root, source);
if (!src_abs)
return -ENOMEM;
STRV_FOREACH(dst, symlinks) {
_cleanup_free_ char *dst_abs = NULL;
dst_abs = path_join(root, *dst);
if (!dst_abs)
return -ENOMEM;
r = mkdir_parents_label(dst_abs, 0755);
if (r < 0)
return r;
r = symlink_idempotent(src_abs, dst_abs, true);
if (r < 0)
return r;
}
return 0;
}
static int set_exec_storage_quota(int fd, uint32_t proj_id, const QuotaLimit *ql) {
int r;
uint64_t block_limit = 0, inode_limit = 0;
assert(fd >= 0);
assert(ql);
if (ql->quota_absolute == 0 || ql->quota_scale == 0)
/* Limit of 0 means no usage is allowed. For quotactl, use 1 as the limit, since 0 means that
* hard limits are disabled */
block_limit = inode_limit = 1;
else if (ql->quota_absolute == UINT64_MAX) {
_cleanup_close_ int fd_parent = -EBADF;
/* Use target_dir's parent when setting quotas. If a FD for target_dir has been previously
* used for quotactl_fd(SET) and is passed again for fstatvfs(), the total number of blocks is not
* reported accurately (instead, the block limit is reported as total blocks). Thus, use the FD
* associated with the parent, so that total blocks is accurate */
fd_parent = openat(fd, "..", O_PATH|O_CLOEXEC|O_DIRECTORY);
if (fd_parent < 0)
return -errno;
uint32_t xattr_flags = 0;
r = read_fs_xattr_fd(fd_parent, &xattr_flags, /* ret_projid = */ NULL);
if (r < 0)
return r;
/* Refuse if parent has FS_XFLAG_PROJINHERIT since this will mean the total number of blocks will not
* be reported accurately */
if (FLAGS_SET(xattr_flags, FS_XFLAG_PROJINHERIT))
return -ENOMEDIUM;
struct statvfs disk_st;
if (fstatvfs(fd_parent, &disk_st) < 0)
return -errno;
block_limit = (uint64_t) DIV_ROUND_UP((uint64_t)((double) (disk_st.f_frsize * disk_st.f_blocks) / UINT32_MAX * ql->quota_scale), QIF_DQBLKSIZE);
inode_limit = (uint64_t) ((double) disk_st.f_files / UINT32_MAX * ql->quota_scale);
} else
block_limit = (uint64_t) DIV_ROUND_UP(ql->quota_absolute, QIF_DQBLKSIZE);
struct dqblk req = {
.dqb_bhardlimit = block_limit,
.dqb_ihardlimit = inode_limit,
.dqb_valid = QIF_LIMITS,
};
r = quotactl_fd_with_fallback(fd, QCMD_FIXED(Q_SETQUOTA, PRJQUOTA), proj_id, &req);
if (r < 0)
return r;
log_debug("Storage quotas set for project id %" PRIu32 ". Block limit = %" PRIu64 ", inode limit = %" PRIu64, proj_id, block_limit, inode_limit);
return 0;
}
static int unset_exec_storage_quota(int fd, uint32_t proj_id, bool quota_accounting) {
int r, quota_supported;
struct dqblk req;
assert(fd >= 0);
quota_supported = quota_query_proj_id(fd, proj_id, &req);
if (quota_supported < 0)
return log_debug_errno(quota_supported, "Failed to query disk quota for project ID %" PRIu32 ": %m", proj_id);
/* Do not enforce quotas anymore */
if (quota_supported && FLAGS_SET(req.dqb_valid, QIF_BLIMITS) && (req.dqb_bhardlimit > 0 || req.dqb_ihardlimit > 0)) {
req.dqb_bhardlimit = 0, req.dqb_ihardlimit = 0;
r = quotactl_fd_with_fallback(fd, QCMD_FIXED(Q_SETQUOTA, PRJQUOTA), proj_id, &req);
if (r < 0)
return log_debug_errno(r, "Failed to disable project quotas for project ID %" PRIu32 ": %m", proj_id);
log_debug("Storage quotas for project ID %" PRIu32 " were disabled", proj_id);
}
/* Release project ID if no accounting needed */
if (!quota_accounting) {
r = set_proj_id_recursive(fd, 0);
if (r < 0)
log_warning_errno(r, "Failed to release project ID %" PRIu32 ", ignoring: %m", proj_id);
}
return 0;
}
static int apply_exec_quotas(
const char *target_dir,
const char *cgroup_path,
ExecDirectoryType type,
const QuotaLimit *ql,
uint32_t *exec_dt_proj_id, /* in/out */
bool *already_enforced) { /* in/out */
_cleanup_close_ int fd = -EBADF;
int r, quota_supported = 0;
assert(target_dir);
assert(cgroup_path);
assert(ql);
assert(exec_dt_proj_id);
assert(already_enforced);
/* Do not apply to the Runtime directory since tmpfs does not support project IDs yet */
if (!IN_SET(type, EXEC_DIRECTORY_STATE, EXEC_DIRECTORY_CACHE, EXEC_DIRECTORY_LOGS))
return 0;
fd = open(target_dir, O_PATH|O_CLOEXEC|O_DIRECTORY);
if (fd < 0)
return log_debug_errno(errno, "Failed to open %s: %m", target_dir);
/* Get the project ID of the current directory */
uint32_t proj_id;
r = read_fs_xattr_fd(fd, /* ret_xflags = */ NULL, &proj_id);
if (ERRNO_IS_NEG_IOCTL_NOT_SUPPORTED(r)) {
log_debug_errno(r, "Not applying storage quotas. FS_IOC_FSGETXATTR not supported for %s: %m", target_dir);
return 0;
}
if (r < 0)
return log_debug_errno(r, "Failed to retrieve project ID for %s: %m", target_dir);
/* If the first directory of this ExecType already has a project ID, adopt it as the project ID for all dirs of this ExecType */
bool proj_id_exists = PROJ_ID_MIN <= proj_id && proj_id <= PROJ_ID_MAX;
if (proj_id_exists && *exec_dt_proj_id == 0)
*exec_dt_proj_id = proj_id;
/* Check if enforcement should be disabled. Do not release project ID if accounting is enabled */
if (!ql->quota_enforce) {
if (proj_id_exists) {
r = unset_exec_storage_quota(fd, proj_id, ql->quota_accounting);
if (r < 0)
return log_debug_errno(r, "Failed to unset project quotas for %s: %m", target_dir);
}
if (!ql->quota_accounting)
return 0;
}
if (*exec_dt_proj_id > 0 && *exec_dt_proj_id != proj_id) {
/* Set the existing project ID only if the current directory's ID does not exist or does not match */
proj_id = *exec_dt_proj_id;
r = quota_proj_id_set_recursive(fd, proj_id, false);
if (r < 0)
return log_debug_errno(r, "Failed to set project ID for %s: %m", target_dir);
} else if (*exec_dt_proj_id == 0) {
/* Only generate a new project ID if it's the first directory of this ExecType to be processed and does not have an existing ID */
static const sd_id128_t k = SD_ID128_ARRAY(e1,4a,79,9b,64,40,41,4a,a8,46,c2,f3,f9,19,4f,01);
_cleanup_free_ char *proj_id_plain = NULL;
/* Generate candidate project id */
proj_id_plain = strjoin(cgroup_path, "|", exec_directory_type_to_string(type));
if (!proj_id_plain)
return log_oom_debug();
struct siphash state;
siphash24_init(&state, k.bytes);
siphash24_compress_string(proj_id_plain, &state);
proj_id = PROJ_ID_CLAMP_INTO_QUOTA_RANGE(siphash24_finalize(&state));
#define MAX_PROJ_ID_RETRIES 10
for (unsigned attempt = 0;; attempt++) {
if (attempt >= MAX_PROJ_ID_RETRIES)
return log_debug_errno(SYNTHETIC_ERRNO(EBUSY), "Failed to generate unique project ID for '%s'.", target_dir);
/* Check if project quotas are supported */
struct dqblk req;
quota_supported = quota_query_proj_id(fd, proj_id, &req);
if (quota_supported < 0)
return log_debug_errno(quota_supported, "Failed to query disk quota for project ID %" PRIu32 ": %m", proj_id);
if (!quota_supported) {
log_debug("Not applying storage quotas. Project quotas are not supported for %s", target_dir);
return 0;
}
if (!quota_dqblk_is_populated(&req)) {
int proj_id_was_set = quota_proj_id_set_recursive(fd, proj_id, true);
if (proj_id_was_set < 0)
return log_debug_errno(proj_id_was_set, "Failed to set project ID for %s: %m", target_dir);
if (proj_id_was_set) {
*exec_dt_proj_id = proj_id;
log_debug("Project ID %u generated for %s", proj_id, target_dir);
break;
}
}
proj_id = (uint32_t) (random_u64_range(PROJ_ID_MAX - PROJ_ID_MIN + 1) + PROJ_ID_MIN);
}
}
if (ql->quota_enforce && !*already_enforced) {
if (!quota_supported) {
struct dqblk req;
quota_supported = quota_query_proj_id(fd, proj_id, &req);
if (quota_supported < 0)
return log_debug_errno(quota_supported, "Failed to query disk quota for project ID %" PRIu32 ": %m", proj_id);
if (!quota_supported) {
log_debug("Not applying storage quotas. Project quotas are not supported for %s", target_dir);
return 0;
}
}
r = set_exec_storage_quota(fd, proj_id, ql);
if (r < 0)
return log_debug_errno(r, "Failed to set storage quotas for %s: %m", target_dir);
*already_enforced = true;
}
return r;
}
static int setup_exec_directory(
const ExecContext *context,
const ExecParameters *params,
uid_t uid,
gid_t gid,
ExecDirectoryType type,
bool needs_mount_namespace,
int *exit_status) {
static const int exit_status_table[_EXEC_DIRECTORY_TYPE_MAX] = {
[EXEC_DIRECTORY_RUNTIME] = EXIT_RUNTIME_DIRECTORY,
[EXEC_DIRECTORY_STATE] = EXIT_STATE_DIRECTORY,
[EXEC_DIRECTORY_CACHE] = EXIT_CACHE_DIRECTORY,
[EXEC_DIRECTORY_LOGS] = EXIT_LOGS_DIRECTORY,
[EXEC_DIRECTORY_CONFIGURATION] = EXIT_CONFIGURATION_DIRECTORY,
};
int r;
assert(context);
assert(params);
assert(type >= 0 && type < _EXEC_DIRECTORY_TYPE_MAX);
assert(exit_status);
if (!params->prefix[type])
return 0;
if (params->flags & EXEC_CHOWN_DIRECTORIES) {
if (!uid_is_valid(uid))
uid = 0;
if (!gid_is_valid(gid))
gid = 0;
}
uint32_t exec_dt_proj_id = 0;
bool quota_already_enforced = false;
FOREACH_ARRAY(i, context->directories[type].items, context->directories[type].n_items) {
_cleanup_free_ char *p = NULL, *pp = NULL;
p = path_join(params->prefix[type], i->path);
if (!p) {
r = -ENOMEM;
goto fail;
}
r = mkdir_parents_label(p, 0755);
if (r < 0)
goto fail;
if (IN_SET(type, EXEC_DIRECTORY_STATE, EXEC_DIRECTORY_LOGS) && params->runtime_scope == RUNTIME_SCOPE_USER) {
/* If we are in user mode, and a configuration directory exists but a state directory
* doesn't exist, then we likely are upgrading from an older systemd version that
* didn't know the more recent addition to the xdg-basedir spec: the $XDG_STATE_HOME
* directory. In older systemd versions EXEC_DIRECTORY_STATE was aliased to
* EXEC_DIRECTORY_CONFIGURATION, with the advent of $XDG_STATE_HOME it is now
* separated. If a service has both dirs configured but only the configuration dir
* exists and the state dir does not, we assume we are looking at an update
* situation. Hence, create a compatibility symlink, so that all expectations are
* met.
*
* (We also do something similar with the log directory, which still doesn't exist in
* the xdg basedir spec. We'll make it a subdir of the state dir.) */
/* this assumes the state dir is always created before the configuration dir */
assert_cc(EXEC_DIRECTORY_STATE < EXEC_DIRECTORY_LOGS);
assert_cc(EXEC_DIRECTORY_LOGS < EXEC_DIRECTORY_CONFIGURATION);
r = access_nofollow(p, F_OK);
if (r == -ENOENT) {
_cleanup_free_ char *q = NULL;
/* OK, we know that the state dir does not exist. Let's see if the dir exists
* under the configuration hierarchy. */
if (type == EXEC_DIRECTORY_STATE)
q = path_join(params->prefix[EXEC_DIRECTORY_CONFIGURATION], i->path);
else if (type == EXEC_DIRECTORY_LOGS)
q = path_join(params->prefix[EXEC_DIRECTORY_CONFIGURATION], "log", i->path);
else
assert_not_reached();
if (!q) {
r = -ENOMEM;
goto fail;
}
r = access_nofollow(q, F_OK);
if (r >= 0) {
/* It does exist! This hence looks like an update. Symlink the
* configuration directory into the state directory. */
r = symlink_idempotent(q, p, /* make_relative= */ true);
if (r < 0)
goto fail;
log_notice("Unit state directory %s missing but matching configuration directory %s exists, assuming update from systemd 253 or older, creating compatibility symlink.", p, q);
continue;
} else if (r != -ENOENT)
log_warning_errno(r, "Unable to detect whether unit configuration directory '%s' exists, assuming not: %m", q);
} else if (r < 0)
log_warning_errno(r, "Unable to detect whether unit state directory '%s' is missing, assuming it is: %m", p);
}
if (exec_directory_is_private(context, type)) {
/* So, here's one extra complication when dealing with DynamicUser=1 units. In that
* case we want to avoid leaving a directory around fully accessible that is owned by
* a dynamic user whose UID is later on reused. To lock this down we use the same
* trick used by container managers to prohibit host users to get access to files of
* the same UID in containers: we place everything inside a directory that has an
* access mode of 0700 and is owned root:root, so that it acts as security boundary
* for unprivileged host code. We then use fs namespacing to make this directory
* permeable for the service itself.
*
* Specifically: for a service which wants a special directory "foo/" we first create
* a directory "private/" with access mode 0700 owned by root:root. Then we place
* "foo" inside of that directory (i.e. "private/foo/"), and make "foo" a symlink to
* "private/foo". This way, privileged host users can access "foo/" as usual, but
* unprivileged host users can't look into it. Inside of the namespace of the unit
* "private/" is replaced by a more liberally accessible tmpfs, into which the host's
* "private/foo/" is mounted under the same name, thus disabling the access boundary
* for the service and making sure it only gets access to the dirs it needs but no
* others. Tricky? Yes, absolutely, but it works!
*
* Note that we don't do this for EXEC_DIRECTORY_CONFIGURATION as that's assumed not
* to be owned by the service itself.
*
* Also, note that we don't do this for EXEC_DIRECTORY_RUNTIME as that's often used
* for sharing files or sockets with other services. */
pp = path_join(params->prefix[type], "private");
if (!pp) {
r = -ENOMEM;
goto fail;
}
/* First set up private root if it doesn't exist yet, with access mode 0700 and owned by root:root */
r = mkdir_safe_label(pp, 0700, 0, 0, MKDIR_WARN_MODE);
if (r < 0)
goto fail;
if (!path_extend(&pp, i->path)) {
r = -ENOMEM;
goto fail;
}
/* Create all directories between the configured directory and this private root, and mark them 0755 */
r = mkdir_parents_label(pp, 0755);
if (r < 0)
goto fail;
if (is_dir(p, false) > 0 &&
(access_nofollow(pp, F_OK) == -ENOENT)) {
/* Hmm, the private directory doesn't exist yet, but the normal one exists? If so, move
* it over. Most likely the service has been upgraded from one that didn't use
* DynamicUser=1, to one that does. */
log_info("Found pre-existing public %s= directory %s, migrating to %s.\n"
"Apparently, service previously had DynamicUser= turned off, and has now turned it on.",
exec_directory_type_to_string(type), p, pp);
r = RET_NERRNO(rename(p, pp));
if (r < 0)
goto fail;
} else {
/* Otherwise, create the actual directory for the service */
r = mkdir_label(pp, context->directories[type].mode);
if (r < 0 && r != -EEXIST)
goto fail;
}
if (!FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE)) {
/* And link it up from the original place.
* Notes
* 1) If a mount namespace is going to be used, then this symlink remains on
* the host, and a new one for the child namespace will be created later.
* 2) It is not necessary to create this symlink when one of its parent
* directories is specified and already created. E.g.
* StateDirectory=foo foo/bar
* In that case, the inode points to pp and p for "foo/bar" are the same:
* pp = "/var/lib/private/foo/bar"
* p = "/var/lib/foo/bar"
* and, /var/lib/foo is a symlink to /var/lib/private/foo. So, not only
* we do not need to create the symlink, but we cannot create the symlink.
* See issue #24783. */
r = symlink_idempotent(pp, p, true);
if (r < 0)
goto fail;
}
} else {
_cleanup_free_ char *target = NULL;
if (EXEC_DIRECTORY_TYPE_SHALL_CHOWN(type) &&
readlink_and_make_absolute(p, &target) >= 0) {
_cleanup_free_ char *q = NULL, *q_resolved = NULL, *target_resolved = NULL;
/* This already exists and is a symlink? Interesting. Maybe it's one created
* by DynamicUser=1 (see above)?
*
* We do this for all directory types except for ConfigurationDirectory=,
* since they all support the private/ symlink logic at least in some
* configurations, see above. */
r = chase(target, NULL, 0, &target_resolved, NULL);
if (r < 0)
goto fail;
q = path_join(params->prefix[type], "private", i->path);
if (!q) {
r = -ENOMEM;
goto fail;
}
/* /var/lib or friends may be symlinks. So, let's chase them also. */
r = chase(q, NULL, CHASE_NONEXISTENT, &q_resolved, NULL);
if (r < 0)
goto fail;
if (path_equal(q_resolved, target_resolved)) {
/* Hmm, apparently DynamicUser= was once turned on for this service,
* but is no longer. Let's move the directory back up. */
log_info("Found pre-existing private %s= directory %s, migrating to %s.\n"
"Apparently, service previously had DynamicUser= turned on, and has now turned it off.",
exec_directory_type_to_string(type), q, p);
r = RET_NERRNO(unlink(p));
if (r < 0)
goto fail;
r = RET_NERRNO(rename(q, p));
if (r < 0)
goto fail;
}
}
r = mkdir_label(p, context->directories[type].mode);
if (r < 0) {
if (r != -EEXIST)
goto fail;
if (!EXEC_DIRECTORY_TYPE_SHALL_CHOWN(type)) {
struct stat st;
/* Don't change the owner/access mode of the configuration directory,
* as in the common case it is not written to by a service, and shall
* not be writable. */
r = RET_NERRNO(stat(p, &st));
if (r < 0)
goto fail;
/* Still complain if the access mode doesn't match */
if (((st.st_mode ^ context->directories[type].mode) & 07777) != 0)
log_warning("%s \'%s\' already exists but the mode is different. "
"(File system: %o %sMode: %o)",
exec_directory_type_to_string(type), i->path,
st.st_mode & 07777, exec_directory_type_to_string(type), context->directories[type].mode & 07777);
continue;
}
}
}
/* Lock down the access mode (we use chmod_and_chown() to make this idempotent. We don't
* specify UID/GID here, so that path_chown_recursive() can optimize things depending on the
* current UID/GID ownership.) */
const char *target_dir = pp ?: p;
r = chmod_and_chown(target_dir, context->directories[type].mode, UID_INVALID, GID_INVALID);
if (r < 0)
goto fail;
/* Skip the rest (which deals with ownership) in user mode, since ownership changes are not
* available to user code anyway */
if (params->runtime_scope != RUNTIME_SCOPE_SYSTEM)
continue;
int idmapping_supported = is_idmapping_supported(target_dir);
if (idmapping_supported < 0) {
r = log_debug_errno(idmapping_supported, "Unable to determine if ID mapping is supported on mount '%s': %m", target_dir);
goto fail;
}
log_debug("ID-mapping is%ssupported for exec directory %s", idmapping_supported ? " " : " not ", target_dir);
/* Change the ownership of the whole tree, if necessary. When dynamic users are used we
* drop the suid/sgid bits, since we really don't want SUID/SGID files for dynamic UID/GID
* assignments to exist. */
uid_t chown_uid = uid;
gid_t chown_gid = gid;
bool do_chown = false;
if (uid == 0 || gid == 0 || !idmapping_supported) {
do_chown = true;
i->idmapped = false;
} else {
/* Use 'nobody' uid/gid for exec directories if ID-mapping is supported. For backward compatibility,
* continue doing chmod/chown if the directory was chmod/chowned before (if uid/gid is not 'nobody') */
struct stat st;
r = RET_NERRNO(stat(target_dir, &st));
if (r < 0)
goto fail;
if (st.st_uid == UID_NOBODY && st.st_gid == GID_NOBODY) {
do_chown = false;
i->idmapped = true;
} else if (exec_directory_is_private(context, type) && st.st_uid == 0 && st.st_gid == 0) {
chown_uid = UID_NOBODY;
chown_gid = GID_NOBODY;
do_chown = true;
i->idmapped = true;
} else {
do_chown = true;
i->idmapped = false;
}
}
if (do_chown) {
r = path_chown_recursive(target_dir, chown_uid, chown_gid, context->dynamic_user ? 01777 : 07777, AT_SYMLINK_FOLLOW);
if (r < 0)
goto fail;
}
/* Apply storage quotas and accounting */
r = apply_exec_quotas(target_dir, params->cgroup_path, type, &context->directories[type].exec_quota, &exec_dt_proj_id, &quota_already_enforced);
if (r < 0)
goto fail;
}
/* If we are not going to run in a namespace, set up the symlinks - otherwise
* they are set up later, to allow configuring empty var/run/etc. */
if (!needs_mount_namespace)
FOREACH_ARRAY(i, context->directories[type].items, context->directories[type].n_items) {
r = create_many_symlinks(params->prefix[type], i->path, i->symlinks);
if (r < 0)
goto fail;
}
return 0;
fail:
*exit_status = exit_status_table[type];
return r;
}
#if ENABLE_SMACK
static int setup_smack(
const ExecContext *context,
const ExecParameters *params,
int executable_fd) {
int r;
assert(context);
assert(params);
assert(executable_fd >= 0);
if (context->smack_process_label) {
r = mac_smack_apply_pid(0, context->smack_process_label);
if (r < 0)
return r;
} else if (params->fallback_smack_process_label) {
_cleanup_free_ char *exec_label = NULL;
r = mac_smack_read_fd(executable_fd, SMACK_ATTR_EXEC, &exec_label);
if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
return r;
r = mac_smack_apply_pid(0, exec_label ?: params->fallback_smack_process_label);
if (r < 0)
return r;
}
return 0;
}
#endif
static int compile_bind_mounts(
const ExecContext *context,
const ExecParameters *params,
uid_t exec_directory_uid, /* only used for id-mapped mounts Exec directories */
gid_t exec_directory_gid, /* only used for id-mapped mounts Exec directories */
BindMount **ret_bind_mounts,
size_t *ret_n_bind_mounts,
char ***ret_empty_directories) {
_cleanup_strv_free_ char **empty_directories = NULL;
BindMount *bind_mounts = NULL;
size_t n, h = 0;
int r;
assert(context);
assert(params);
assert(ret_bind_mounts);
assert(ret_n_bind_mounts);
assert(ret_empty_directories);
CLEANUP_ARRAY(bind_mounts, h, bind_mount_free_many);
n = context->n_bind_mounts;
for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
if (!params->prefix[t])
continue;
FOREACH_ARRAY(i, context->directories[t].items, context->directories[t].n_items)
n += !FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE) || FLAGS_SET(i->flags, EXEC_DIRECTORY_READ_ONLY);
}
if (n <= 0) {
*ret_bind_mounts = NULL;
*ret_n_bind_mounts = 0;
*ret_empty_directories = NULL;
return 0;
}
bind_mounts = new(BindMount, n);
if (!bind_mounts)
return -ENOMEM;
FOREACH_ARRAY(item, context->bind_mounts, context->n_bind_mounts) {
r = bind_mount_add(&bind_mounts, &h, item);
if (r < 0)
return r;
}
for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
if (!params->prefix[t])
continue;
if (context->directories[t].n_items == 0)
continue;
if (exec_directory_is_private(context, t) &&
!exec_context_with_rootfs(context)) {
char *private_root;
/* So this is for a dynamic user, and we need to make sure the process can access its own
* directory. For that we overmount the usually inaccessible "private" subdirectory with a
* tmpfs that makes it accessible and is empty except for the submounts we do this for. */
private_root = path_join(params->prefix[t], "private");
if (!private_root)
return -ENOMEM;
r = strv_consume(&empty_directories, private_root);
if (r < 0)
return r;
}
FOREACH_ARRAY(i, context->directories[t].items, context->directories[t].n_items) {
_cleanup_free_ char *s = NULL, *d = NULL;
/* When one of the parent directories is in the list, we cannot create the symlink
* for the child directory. See also the comments in setup_exec_directory().
* But if it needs to be read only, then we have to create a bind mount anyway to
* make it so. */
if (FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE) && !FLAGS_SET(i->flags, EXEC_DIRECTORY_READ_ONLY))
continue;
if (exec_directory_is_private(context, t))
s = path_join(params->prefix[t], "private", i->path);
else
s = path_join(params->prefix[t], i->path);
if (!s)
return -ENOMEM;
if (exec_directory_is_private(context, t) &&
exec_context_with_rootfs(context))
/* When RootDirectory= or RootImage= are set, then the symbolic link to the private
* directory is not created on the root directory. So, let's bind-mount the directory
* on the 'non-private' place. */
d = path_join(params->prefix[t], i->path);
else
d = strdup(s);
if (!d)
return -ENOMEM;
bind_mounts[h++] = (BindMount) {
.source = TAKE_PTR(s),
.destination = TAKE_PTR(d),
.nosuid = context->dynamic_user, /* don't allow suid/sgid when DynamicUser= is on */
.recursive = true,
.read_only = FLAGS_SET(i->flags, EXEC_DIRECTORY_READ_ONLY),
.idmapped = i->idmapped,
.uid = exec_directory_uid,
.gid = exec_directory_gid,
};
}
}
assert(h == n);
*ret_bind_mounts = TAKE_PTR(bind_mounts);
*ret_n_bind_mounts = n;
*ret_empty_directories = TAKE_PTR(empty_directories);
return (int) n;
}
/* ret_symlinks will contain a list of pairs src:dest that describes
* the symlinks to create later on. For example, the symlinks needed
* to safely give private directories to DynamicUser=1 users. */
static int compile_symlinks(
const ExecContext *context,
const ExecParameters *params,
bool setup_os_release_symlink,
char ***ret_symlinks) {
_cleanup_strv_free_ char **symlinks = NULL;
int r;
assert(context);
assert(params);
assert(ret_symlinks);
for (ExecDirectoryType dt = 0; dt < _EXEC_DIRECTORY_TYPE_MAX; dt++)
FOREACH_ARRAY(i, context->directories[dt].items, context->directories[dt].n_items) {
_cleanup_free_ char *private_path = NULL, *path = NULL;
STRV_FOREACH(symlink, i->symlinks) {
_cleanup_free_ char *src_abs = NULL, *dst_abs = NULL;
src_abs = path_join(params->prefix[dt], i->path);
dst_abs = path_join(params->prefix[dt], *symlink);
if (!src_abs || !dst_abs)
return -ENOMEM;
r = strv_consume_pair(&symlinks, TAKE_PTR(src_abs), TAKE_PTR(dst_abs));
if (r < 0)
return r;
}
if (!exec_directory_is_private(context, dt) ||
exec_context_with_rootfs(context) ||
FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE))
continue;
private_path = path_join(params->prefix[dt], "private", i->path);
if (!private_path)
return -ENOMEM;
path = path_join(params->prefix[dt], i->path);
if (!path)
return -ENOMEM;
r = strv_consume_pair(&symlinks, TAKE_PTR(private_path), TAKE_PTR(path));
if (r < 0)
return r;
}
/* We make the host's os-release available via a symlink, so that we can copy it atomically
* and readers will never get a half-written version. Note that, while the paths specified here are
* absolute, when they are processed in namespace.c they will be made relative automatically, i.e.:
* 'os-release -> .os-release-stage/os-release' is what will be created. */
if (setup_os_release_symlink) {
r = strv_extend_many(
&symlinks,
"/run/host/.os-release-stage/os-release",
"/run/host/os-release");
if (r < 0)
return r;
}
*ret_symlinks = TAKE_PTR(symlinks);
return 0;
}
static bool insist_on_sandboxing(
const ExecContext *context,
const char *root_dir,
const char *root_image,
const BindMount *bind_mounts,
size_t n_bind_mounts) {
assert(context);
assert(n_bind_mounts == 0 || bind_mounts);
/* Checks whether we need to insist on fs namespacing. i.e. whether we have settings configured that
* would alter the view on the file system beyond making things read-only or invisible, i.e. would
* rearrange stuff in a way we cannot ignore gracefully. */
if (context->n_temporary_filesystems > 0)
return true;
if (root_dir || root_image)
return true;
if (context->n_mount_images > 0)
return true;
if (context->dynamic_user)
return true;
if (context->n_extension_images > 0 || !strv_isempty(context->extension_directories))
return true;
/* If there are any bind mounts set that don't map back onto themselves, fs namespacing becomes
* essential. */
FOREACH_ARRAY(i, bind_mounts, n_bind_mounts)
if (!path_equal(i->source, i->destination))
return true;
if (context->log_namespace)
return true;
return false;
}
static int setup_ephemeral(
const ExecContext *context,
ExecRuntime *runtime,
char **root_image, /* both input and output! modified if ephemeral logic enabled */
char **root_directory, /* ditto */
char **reterr_path) {
_cleanup_close_ int fd = -EBADF;
_cleanup_free_ char *new_root = NULL;
int r;
assert(context);
assert(runtime);
assert(root_image);
assert(root_directory);
if (!*root_image && !*root_directory)
return 0;
if (!runtime->ephemeral_copy)
return 0;
assert(runtime->ephemeral_storage_socket[0] >= 0);
assert(runtime->ephemeral_storage_socket[1] >= 0);
new_root = strdup(runtime->ephemeral_copy);
if (!new_root)
return log_oom_debug();
r = posix_lock(runtime->ephemeral_storage_socket[0], LOCK_EX);
if (r < 0)
return log_debug_errno(r, "Failed to lock ephemeral storage socket: %m");
CLEANUP_POSIX_UNLOCK(runtime->ephemeral_storage_socket[0]);
fd = receive_one_fd(runtime->ephemeral_storage_socket[0], MSG_PEEK|MSG_DONTWAIT);
if (fd >= 0)
/* We got an fd! That means ephemeral has already been set up, so nothing to do here. */
return 0;
if (fd != -EAGAIN)
return log_debug_errno(fd, "Failed to receive file descriptor queued on ephemeral storage socket: %m");
if (*root_image) {
log_debug("Making ephemeral copy of %s to %s", *root_image, new_root);
fd = copy_file(*root_image, new_root, O_EXCL, 0600,
COPY_LOCK_BSD|COPY_REFLINK|COPY_CRTIME|COPY_NOCOW_AFTER);
if (fd < 0) {
*reterr_path = strdup(*root_image);
return log_debug_errno(fd, "Failed to copy image %s to %s: %m",
*root_image, new_root);
}
} else {
assert(*root_directory);
log_debug("Making ephemeral snapshot of %s to %s", *root_directory, new_root);
fd = btrfs_subvol_snapshot_at(
AT_FDCWD, *root_directory,
AT_FDCWD, new_root,
BTRFS_SNAPSHOT_FALLBACK_COPY |
BTRFS_SNAPSHOT_FALLBACK_DIRECTORY |
BTRFS_SNAPSHOT_RECURSIVE |
BTRFS_SNAPSHOT_LOCK_BSD);
if (fd < 0) {
*reterr_path = strdup(*root_directory);
return log_debug_errno(fd, "Failed to snapshot directory %s to %s: %m",
*root_directory, new_root);
}
}
r = send_one_fd(runtime->ephemeral_storage_socket[1], fd, MSG_DONTWAIT);
if (r < 0)
return log_debug_errno(r, "Failed to queue file descriptor on ephemeral storage socket: %m");
if (*root_image)
free_and_replace(*root_image, new_root);
else {
assert(*root_directory);
free_and_replace(*root_directory, new_root);
}
return 1;
}
static int verity_settings_prepare(
VeritySettings *verity,
const char *root_image,
const void *root_hash,
size_t root_hash_size,
const char *root_hash_path,
const void *root_hash_sig,
size_t root_hash_sig_size,
const char *root_hash_sig_path,
const char *verity_data_path) {
int r;
assert(verity);
if (root_hash) {
void *d;
d = memdup(root_hash, root_hash_size);
if (!d)
return -ENOMEM;
free_and_replace(verity->root_hash, d);
verity->root_hash_size = root_hash_size;
verity->designator = PARTITION_ROOT;
}
if (root_hash_sig) {
void *d;
d = memdup(root_hash_sig, root_hash_sig_size);
if (!d)
return -ENOMEM;
free_and_replace(verity->root_hash_sig, d);
verity->root_hash_sig_size = root_hash_sig_size;
verity->designator = PARTITION_ROOT;
}
if (verity_data_path) {
r = free_and_strdup(&verity->data_path, verity_data_path);
if (r < 0)
return r;
}
r = verity_settings_load(
verity,
root_image,
root_hash_path,
root_hash_sig_path);
if (r < 0)
return log_debug_errno(r, "Failed to load root hash: %m");
return 0;
}
static int pick_versions(
const ExecContext *context,
const ExecParameters *params,
char **ret_root_image,
char **ret_root_directory,
char **reterr_path) {
int r;
assert(context);
assert(params);
assert(ret_root_image);
assert(ret_root_directory);
if (context->root_image) {
_cleanup_(pick_result_done) PickResult result = PICK_RESULT_NULL;
r = path_pick(/* toplevel_path= */ NULL,
/* toplevel_fd= */ AT_FDCWD,
context->root_image,
&pick_filter_image_raw,
PICK_ARCHITECTURE|PICK_TRIES|PICK_RESOLVE,
&result);
if (r < 0) {
*reterr_path = strdup(context->root_image);
return r;
}
if (!result.path) {
*reterr_path = strdup(context->root_image);
return log_debug_errno(SYNTHETIC_ERRNO(ENOENT), "No matching entry in .v/ directory %s found.", context->root_image);
}
*ret_root_image = TAKE_PTR(result.path);
*ret_root_directory = NULL;
return r;
}
if (context->root_directory) {
_cleanup_(pick_result_done) PickResult result = PICK_RESULT_NULL;
r = path_pick(/* toplevel_path= */ NULL,
/* toplevel_fd= */ AT_FDCWD,
context->root_directory,
&pick_filter_image_dir,
PICK_ARCHITECTURE|PICK_TRIES|PICK_RESOLVE,
&result);
if (r < 0) {
*reterr_path = strdup(context->root_directory);
return r;
}
if (!result.path) {
*reterr_path = strdup(context->root_directory);
return log_debug_errno(SYNTHETIC_ERRNO(ENOENT), "No matching entry in .v/ directory %s found.", context->root_directory);
}
*ret_root_image = NULL;
*ret_root_directory = TAKE_PTR(result.path);
return r;
}
*ret_root_image = *ret_root_directory = NULL;
return 0;
}
static int apply_mount_namespace(
ExecCommandFlags command_flags,
const ExecContext *context,
const ExecParameters *params,
ExecRuntime *runtime,
const char *memory_pressure_path,
bool needs_sandboxing,
uid_t exec_directory_uid,
gid_t exec_directory_gid,
PidRef *bpffs_pidref,
int bpffs_socket_fd,
int bpffs_errno_pipe,
char **reterr_path) {
_cleanup_(verity_settings_done) VeritySettings verity = VERITY_SETTINGS_DEFAULT;
_cleanup_strv_free_ char **empty_directories = NULL, **symlinks = NULL,
**read_write_paths_cleanup = NULL;
_cleanup_free_ char *creds_path = NULL, *incoming_dir = NULL, *propagate_dir = NULL,
*private_namespace_dir = NULL, *host_os_release_stage = NULL, *root_image = NULL, *root_dir = NULL;
const char *tmp_dir = NULL, *var_tmp_dir = NULL;
char **read_write_paths;
bool setup_os_release_symlink;
BindMount *bind_mounts = NULL;
size_t n_bind_mounts = 0;
int r;
assert(context);
assert(params);
assert(runtime);
CLEANUP_ARRAY(bind_mounts, n_bind_mounts, bind_mount_free_many);
if (params->flags & EXEC_APPLY_CHROOT) {
r = pick_versions(
context,
params,
&root_image,
&root_dir,
reterr_path);
if (r < 0)
return r;
r = setup_ephemeral(
context,
runtime,
&root_image,
&root_dir,
reterr_path);
if (r < 0)
return r;
}
r = compile_bind_mounts(context, params, exec_directory_uid, exec_directory_gid, &bind_mounts, &n_bind_mounts, &empty_directories);
if (r < 0)
return r;
/* We need to make the pressure path writable even if /sys/fs/cgroups is made read-only, as the
* service will need to write to it in order to start the notifications. */
if (exec_is_cgroup_mount_read_only(context) && memory_pressure_path && !streq(memory_pressure_path, "/dev/null")) {
read_write_paths_cleanup = strv_copy(context->read_write_paths);
if (!read_write_paths_cleanup)
return -ENOMEM;
r = strv_extend(&read_write_paths_cleanup, memory_pressure_path);
if (r < 0)
return r;
read_write_paths = read_write_paths_cleanup;
} else
read_write_paths = context->read_write_paths;
if (needs_sandboxing) {
/* The runtime struct only contains the parent of the private /tmp, which is non-accessible
* to world users. Inside of it there's a /tmp that is sticky, and that's the one we want to
* use here. This does not apply when we are using /run/systemd/empty as fallback. */
if (context->private_tmp == PRIVATE_TMP_CONNECTED && runtime->shared) {
if (streq_ptr(runtime->shared->tmp_dir, RUN_SYSTEMD_EMPTY))
tmp_dir = runtime->shared->tmp_dir;
else if (runtime->shared->tmp_dir)
tmp_dir = strjoina(runtime->shared->tmp_dir, "/tmp");
if (streq_ptr(runtime->shared->var_tmp_dir, RUN_SYSTEMD_EMPTY))
var_tmp_dir = runtime->shared->var_tmp_dir;
else if (runtime->shared->var_tmp_dir)
var_tmp_dir = strjoina(runtime->shared->var_tmp_dir, "/tmp");
}
}
/* Symlinks (exec dirs, os-release) are set up after other mounts, before they are made read-only. */
setup_os_release_symlink = needs_sandboxing && exec_context_get_effective_mount_apivfs(context) && (root_dir || root_image);
r = compile_symlinks(context, params, setup_os_release_symlink, &symlinks);
if (r < 0)
return r;
if (context->mount_propagation_flag == MS_SHARED)
log_debug("shared mount propagation hidden by other fs namespacing unit settings: ignoring");
r = exec_context_get_credential_directory(context, params, params->unit_id, &creds_path);
if (r < 0)
return r;
if (params->runtime_scope == RUNTIME_SCOPE_SYSTEM) {
propagate_dir = path_join("/run/systemd/propagate/", params->unit_id);
if (!propagate_dir)
return -ENOMEM;
incoming_dir = strdup("/run/systemd/incoming");
if (!incoming_dir)
return -ENOMEM;
private_namespace_dir = strdup("/run/systemd");
if (!private_namespace_dir)
return -ENOMEM;
/* If running under a different root filesystem, propagate the host's os-release. We make a
* copy rather than just bind mounting it, so that it can be updated on soft-reboot. */
if (setup_os_release_symlink) {
host_os_release_stage = strdup("/run/systemd/propagate/.os-release-stage");
if (!host_os_release_stage)
return -ENOMEM;
}
} else {
assert(params->runtime_scope == RUNTIME_SCOPE_USER);
if (asprintf(&private_namespace_dir, "/run/user/" UID_FMT "/systemd", geteuid()) < 0)
return -ENOMEM;
if (setup_os_release_symlink) {
if (asprintf(&host_os_release_stage,
"/run/user/" UID_FMT "/systemd/propagate/.os-release-stage",
geteuid()) < 0)
return -ENOMEM;
}
}
if (root_image) {
r = verity_settings_prepare(
&verity,
root_image,
context->root_hash, context->root_hash_size, context->root_hash_path,
context->root_hash_sig, context->root_hash_sig_size, context->root_hash_sig_path,
context->root_verity);
if (r < 0)
return r;
}
NamespaceParameters parameters = {
.runtime_scope = params->runtime_scope,
.root_directory = root_dir,
.root_image = root_image,
.root_image_options = context->root_image_options,
.root_image_policy = context->root_image_policy ?: &image_policy_service,
.read_write_paths = read_write_paths,
.read_only_paths = needs_sandboxing ? context->read_only_paths : NULL,
.inaccessible_paths = needs_sandboxing ? context->inaccessible_paths : NULL,
.exec_paths = needs_sandboxing ? context->exec_paths : NULL,
.no_exec_paths = needs_sandboxing ? context->no_exec_paths : NULL,
.empty_directories = empty_directories,
.symlinks = symlinks,
.bind_mounts = bind_mounts,
.n_bind_mounts = n_bind_mounts,
.temporary_filesystems = context->temporary_filesystems,
.n_temporary_filesystems = context->n_temporary_filesystems,
.mount_images = context->mount_images,
.n_mount_images = context->n_mount_images,
.mount_image_policy = context->mount_image_policy ?: &image_policy_service,
.tmp_dir = tmp_dir,
.var_tmp_dir = var_tmp_dir,
.creds_path = creds_path,
.log_namespace = context->log_namespace,
.mount_propagation_flag = context->mount_propagation_flag,
.verity = &verity,
.extension_images = context->extension_images,
.n_extension_images = context->n_extension_images,
.extension_image_policy = context->extension_image_policy ?: &image_policy_sysext,
.extension_directories = context->extension_directories,
.propagate_dir = propagate_dir,
.incoming_dir = incoming_dir,
.private_namespace_dir = private_namespace_dir,
.host_notify_socket = params->notify_socket,
.notify_socket_path = exec_get_private_notify_socket_path(context, params, needs_sandboxing),
.host_os_release_stage = host_os_release_stage,
/* If DynamicUser=no and RootDirectory= is set then lets pass a relaxed sandbox info,
* otherwise enforce it, don't ignore protected paths and fail if we are enable to apply the
* sandbox inside the mount namespace. */
.ignore_protect_paths = !needs_sandboxing && !context->dynamic_user && root_dir,
.protect_control_groups = needs_sandboxing ? exec_get_protect_control_groups(context) : PROTECT_CONTROL_GROUPS_NO,
.protect_kernel_tunables = needs_sandboxing && context->protect_kernel_tunables,
.protect_kernel_modules = needs_sandboxing && context->protect_kernel_modules,
.protect_kernel_logs = needs_sandboxing && context->protect_kernel_logs,
.private_dev = needs_sandboxing && context->private_devices,
.private_network = needs_sandboxing && exec_needs_network_namespace(context),
.private_ipc = needs_sandboxing && exec_needs_ipc_namespace(context),
.private_pids = needs_sandboxing && exec_needs_pid_namespace(context, params) ? context->private_pids : PRIVATE_PIDS_NO,
.private_tmp = needs_sandboxing ? context->private_tmp : PRIVATE_TMP_NO,
.private_var_tmp = needs_sandboxing ? context->private_var_tmp : PRIVATE_TMP_NO,
.mount_apivfs = needs_sandboxing && exec_context_get_effective_mount_apivfs(context),
.bind_log_sockets = needs_sandboxing && exec_context_get_effective_bind_log_sockets(context),
/* If NNP is on, we can turn on MS_NOSUID, since it won't have any effect anymore. */
.mount_nosuid = needs_sandboxing && context->no_new_privileges && !mac_selinux_use(),
.protect_home = needs_sandboxing ? context->protect_home : PROTECT_HOME_NO,
.protect_hostname = needs_sandboxing ? context->protect_hostname : PROTECT_HOSTNAME_NO,
.protect_system = needs_sandboxing ? context->protect_system : PROTECT_SYSTEM_NO,
.protect_proc = needs_sandboxing ? context->protect_proc : PROTECT_PROC_DEFAULT,
.proc_subset = needs_sandboxing ? context->proc_subset : PROC_SUBSET_ALL,
.private_bpf = needs_sandboxing ? context->private_bpf : PRIVATE_BPF_NO,
.bpffs_pidref = bpffs_pidref,
.bpffs_socket_fd = bpffs_socket_fd,
.bpffs_errno_pipe = bpffs_errno_pipe,
};
r = setup_namespace(&parameters, reterr_path);
/* If we couldn't set up the namespace this is probably due to a missing capability. setup_namespace() reports
* that with a special, recognizable error ENOANO. In this case, silently proceed, but only if exclusively
* sandboxing options were used, i.e. nothing such as RootDirectory= or BindMount= that would result in a
* completely different execution environment. */
if (r == -ENOANO) {
if (insist_on_sandboxing(
context,
root_dir, root_image,
bind_mounts,
n_bind_mounts))
return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
"Failed to set up namespace, and refusing to continue since "
"the selected namespacing options alter mount environment non-trivially.\n"
"Bind mounts: %zu, temporary filesystems: %zu, root directory: %s, root image: %s, dynamic user: %s",
n_bind_mounts,
context->n_temporary_filesystems,
yes_no(root_dir),
yes_no(root_image),
yes_no(context->dynamic_user));
log_debug("Failed to set up namespace, assuming containerized execution and ignoring.");
return 0;
}
return r;
}
static int apply_working_directory(
const ExecContext *context,
const ExecParameters *params,
ExecRuntime *runtime,
const char *pwent_home,
char * const *env) {
const char *wd;
int r;
assert(context);
assert(params);
assert(runtime);
if (context->working_directory_home) {
/* Preferably use the data from $HOME, in case it was updated by a PAM module */
wd = strv_env_get(env, "HOME");
if (!wd) {
/* If that's not available, use the data from the struct passwd entry: */
if (!pwent_home)
return -ENXIO;
wd = pwent_home;
}
} else
wd = empty_to_root(context->working_directory);
if (params->flags & EXEC_APPLY_CHROOT)
r = RET_NERRNO(chdir(wd));
else {
_cleanup_close_ int dfd = -EBADF;
r = chase(wd,
runtime->ephemeral_copy ?: context->root_directory,
CHASE_PREFIX_ROOT|CHASE_AT_RESOLVE_IN_ROOT|CHASE_TRIGGER_AUTOFS,
/* ret_path= */ NULL,
&dfd);
if (r >= 0)
r = RET_NERRNO(fchdir(dfd));
}
return context->working_directory_missing_ok ? 0 : r;
}
static int apply_root_directory(
const ExecContext *context,
const ExecParameters *params,
ExecRuntime *runtime,
const bool needs_mount_ns,
int *exit_status) {
assert(context);
assert(params);
assert(runtime);
assert(exit_status);
if (params->flags & EXEC_APPLY_CHROOT)
if (!needs_mount_ns && context->root_directory)
if (chroot(runtime->ephemeral_copy ?: context->root_directory) < 0) {
*exit_status = EXIT_CHROOT;
return -errno;
}
return 0;
}
static int setup_keyring(
const ExecContext *context,
const ExecParameters *p,
uid_t uid,
gid_t gid) {
key_serial_t keyring;
int r = 0;
uid_t saved_uid;
gid_t saved_gid;
assert(context);
assert(p);
/* Let's set up a new per-service "session" kernel keyring for each system service. This has the benefit that
* each service runs with its own keyring shared among all processes of the service, but with no hook-up beyond
* that scope, and in particular no link to the per-UID keyring. If we don't do this the keyring will be
* automatically created on-demand and then linked to the per-UID keyring, by the kernel. The kernel's built-in
* on-demand behaviour is very appropriate for login users, but probably not so much for system services, where
* UIDs are not necessarily specific to a service but reused (at least in the case of UID 0). */
if (context->keyring_mode == EXEC_KEYRING_INHERIT)
return 0;
/* Acquiring a reference to the user keyring is nasty. We briefly change identity in order to get things set up
* properly by the kernel. If we don't do that then we can't create it atomically, and that sucks for parallel
* execution. This mimics what pam_keyinit does, too. Setting up session keyring, to be owned by the right user
* & group is just as nasty as acquiring a reference to the user keyring. */
saved_uid = getuid();
saved_gid = getgid();
if (gid_is_valid(gid) && gid != saved_gid) {
if (setregid(gid, -1) < 0)
return log_error_errno(errno, "Failed to change GID for user keyring: %m");
}
if (uid_is_valid(uid) && uid != saved_uid) {
if (setreuid(uid, -1) < 0) {
r = log_error_errno(errno, "Failed to change UID for user keyring: %m");
goto out;
}
}
keyring = keyctl(KEYCTL_JOIN_SESSION_KEYRING, 0, 0, 0, 0);
if (keyring == -1) {
if (errno == ENOSYS)
log_debug_errno(errno, "Kernel keyring not supported, ignoring.");
else if (ERRNO_IS_PRIVILEGE(errno))
log_debug_errno(errno, "Kernel keyring access prohibited, ignoring.");
else if (errno == EDQUOT)
log_debug_errno(errno, "Out of kernel keyrings to allocate, ignoring.");
else
r = log_error_errno(errno, "Setting up kernel keyring failed: %m");
goto out;
}
/* When requested link the user keyring into the session keyring. */
if (context->keyring_mode == EXEC_KEYRING_SHARED) {
if (keyctl(KEYCTL_LINK,
KEY_SPEC_USER_KEYRING,
KEY_SPEC_SESSION_KEYRING, 0, 0) < 0) {
r = log_error_errno(errno, "Failed to link user keyring into session keyring: %m");
goto out;
}
}
/* Restore uid/gid back */
if (uid_is_valid(uid) && uid != saved_uid) {
if (setreuid(saved_uid, -1) < 0) {
r = log_error_errno(errno, "Failed to change UID back for user keyring: %m");
goto out;
}
}
if (gid_is_valid(gid) && gid != saved_gid) {
if (setregid(saved_gid, -1) < 0)
return log_error_errno(errno, "Failed to change GID back for user keyring: %m");
}
/* Populate the keyring with the invocation ID by default, as original saved_uid. */
if (!sd_id128_is_null(p->invocation_id)) {
key_serial_t key;
key = add_key("user",
"invocation_id",
&p->invocation_id,
sizeof(p->invocation_id),
KEY_SPEC_SESSION_KEYRING);
if (key == -1)
log_debug_errno(errno, "Failed to add invocation ID to keyring, ignoring: %m");
else {
if (keyctl(KEYCTL_SETPERM, key,
KEY_POS_VIEW|KEY_POS_READ|KEY_POS_SEARCH|
KEY_USR_VIEW|KEY_USR_READ|KEY_USR_SEARCH, 0, 0) < 0)
r = log_error_errno(errno, "Failed to restrict invocation ID permission: %m");
}
}
out:
/* Revert back uid & gid for the last time, and exit */
/* no extra logging, as only the first already reported error matters */
if (getuid() != saved_uid)
(void) setreuid(saved_uid, -1);
if (getgid() != saved_gid)
(void) setregid(saved_gid, -1);
return r;
}
static void append_socket_pair(int *array, size_t *n, const int pair[static 2]) {
assert(array);
assert(n);
assert(pair);
if (pair[0] >= 0)
array[(*n)++] = pair[0];
if (pair[1] >= 0)
array[(*n)++] = pair[1];
}
static int close_remaining_fds(
const ExecParameters *params,
const ExecRuntime *runtime,
int socket_fd,
const int *fds,
size_t n_fds) {
size_t n_dont_close = 0;
int dont_close[n_fds + 17];
assert(params);
assert(runtime);
if (params->stdin_fd >= 0)
dont_close[n_dont_close++] = params->stdin_fd;
if (params->stdout_fd >= 0)
dont_close[n_dont_close++] = params->stdout_fd;
if (params->stderr_fd >= 0)
dont_close[n_dont_close++] = params->stderr_fd;
if (socket_fd >= 0)
dont_close[n_dont_close++] = socket_fd;
if (n_fds > 0) {
memcpy(dont_close + n_dont_close, fds, sizeof(int) * n_fds);
n_dont_close += n_fds;
}
append_socket_pair(dont_close, &n_dont_close, runtime->ephemeral_storage_socket);
if (runtime->shared) {
append_socket_pair(dont_close, &n_dont_close, runtime->shared->netns_storage_socket);
append_socket_pair(dont_close, &n_dont_close, runtime->shared->ipcns_storage_socket);
}
if (runtime->dynamic_creds) {
if (runtime->dynamic_creds->user)
append_socket_pair(dont_close, &n_dont_close, runtime->dynamic_creds->user->storage_socket);
if (runtime->dynamic_creds->group)
append_socket_pair(dont_close, &n_dont_close, runtime->dynamic_creds->group->storage_socket);
}
if (params->user_lookup_fd >= 0)
dont_close[n_dont_close++] = params->user_lookup_fd;
if (params->handoff_timestamp_fd >= 0)
dont_close[n_dont_close++] = params->handoff_timestamp_fd;
if (params->pidref_transport_fd >= 0)
dont_close[n_dont_close++] = params->pidref_transport_fd;
assert(n_dont_close <= ELEMENTSOF(dont_close));
return close_all_fds(dont_close, n_dont_close);
}
static int send_user_lookup(
const char *unit_id,
int user_lookup_fd,
uid_t uid,
gid_t gid) {
assert(unit_id);
/* Send the resolved UID/GID to PID 1 after we learnt it. We send a single datagram, containing the UID/GID
* data as well as the unit name. Note that we suppress sending this if no user/group to resolve was
* specified. */
if (user_lookup_fd < 0)
return 0;
if (!uid_is_valid(uid) && !gid_is_valid(gid))
return 0;
if (writev(user_lookup_fd,
(struct iovec[]) {
IOVEC_MAKE(&uid, sizeof(uid)),
IOVEC_MAKE(&gid, sizeof(gid)),
IOVEC_MAKE_STRING(unit_id) }, 3) < 0)
return -errno;
return 0;
}
static int acquire_home(const ExecContext *c, const char **home, char **ret_buf) {
int r;
assert(c);
assert(home);
assert(ret_buf);
/* If WorkingDirectory=~ is set, try to acquire a usable home directory. */
if (*home) /* Already acquired from get_fixed_user()? */
return 0;
if (!c->working_directory_home)
return 0;
if (c->dynamic_user || (c->user && is_this_me(c->user) <= 0))
return -EADDRNOTAVAIL;
r = get_home_dir(ret_buf);
if (r < 0)
return r;
*home = *ret_buf;
return 1;
}
static int compile_suggested_paths(const ExecContext *c, const ExecParameters *p, char ***ret) {
_cleanup_strv_free_ char ** list = NULL;
int r;
assert(c);
assert(p);
assert(ret);
assert(c->dynamic_user);
/* Compile a list of paths that it might make sense to read the owning UID from to use as initial candidate for
* dynamic UID allocation, in order to save us from doing costly recursive chown()s of the special
* directories. */
for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
if (!EXEC_DIRECTORY_TYPE_SHALL_CHOWN(t))
continue;
if (!p->prefix[t])
continue;
for (size_t i = 0; i < c->directories[t].n_items; i++) {
char *e;
if (exec_directory_is_private(c, t))
e = path_join(p->prefix[t], "private", c->directories[t].items[i].path);
else
e = path_join(p->prefix[t], c->directories[t].items[i].path);
if (!e)
return -ENOMEM;
r = strv_consume(&list, e);
if (r < 0)
return r;
}
}
*ret = TAKE_PTR(list);
return 0;
}
static int exec_context_cpu_affinity_from_numa(const ExecContext *c, CPUSet *ret) {
int r;
assert(c);
assert(ret);
if (!c->numa_policy.nodes.set) {
log_debug("Can't derive CPU affinity mask from NUMA mask because NUMA mask is not set, ignoring");
*ret = (CPUSet) {};
return 0;
}
_cleanup_(cpu_set_done) CPUSet s = {};
r = numa_to_cpu_set(&c->numa_policy, &s);
if (r < 0)
return r;
*ret = TAKE_STRUCT(s);
return 0;
}
static int add_shifted_fd(int *fds, size_t fds_size, size_t *n_fds, int *fd) {
int r;
assert(fds);
assert(n_fds);
assert(*n_fds < fds_size);
assert(fd);
if (*fd < 0)
return 0;
if (*fd < 3 + (int) *n_fds) {
/* Let's move the fd up, so that it's outside of the fd range we will use to store
* the fds we pass to the process (or which are closed only during execve). */
r = fcntl(*fd, F_DUPFD_CLOEXEC, 3 + (int) *n_fds);
if (r < 0)
return -errno;
close_and_replace(*fd, r);
}
fds[(*n_fds)++] = *fd;
return 1;
}
static int connect_unix_harder(const OpenFile *of, int ofd) {
static const int socket_types[] = { SOCK_DGRAM, SOCK_STREAM, SOCK_SEQPACKET };
union sockaddr_union addr = {
.un.sun_family = AF_UNIX,
};
socklen_t sa_len;
int r;
assert(of);
assert(ofd >= 0);
r = sockaddr_un_set_path(&addr.un, FORMAT_PROC_FD_PATH(ofd));
if (r < 0)
return log_debug_errno(r, "Failed to set sockaddr for '%s': %m", of->path);
sa_len = r;
FOREACH_ELEMENT(i, socket_types) {
_cleanup_close_ int fd = -EBADF;
fd = socket(AF_UNIX, *i|SOCK_CLOEXEC, 0);
if (fd < 0)
return log_debug_errno(errno, "Failed to create socket for '%s': %m", of->path);
r = RET_NERRNO(connect(fd, &addr.sa, sa_len));
if (r >= 0)
return TAKE_FD(fd);
if (r != -EPROTOTYPE)
return log_debug_errno(r, "Failed to connect to socket for '%s': %m", of->path);
}
return log_debug_errno(SYNTHETIC_ERRNO(EPROTOTYPE), "No suitable socket type to connect to socket '%s'.", of->path);
}
static int get_open_file_fd(const OpenFile *of) {
_cleanup_close_ int fd = -EBADF, ofd = -EBADF;
struct stat st;
assert(of);
ofd = open(of->path, O_PATH | O_CLOEXEC);
if (ofd < 0)
return log_debug_errno(errno, "Failed to open '%s' as O_PATH: %m", of->path);
if (fstat(ofd, &st) < 0)
return log_debug_errno( errno, "Failed to stat '%s': %m", of->path);
if (S_ISSOCK(st.st_mode)) {
fd = connect_unix_harder(of, ofd);
if (fd < 0)
return fd;
if (FLAGS_SET(of->flags, OPENFILE_READ_ONLY) && shutdown(fd, SHUT_WR) < 0)
return log_debug_errno(errno, "Failed to shutdown send for socket '%s': %m", of->path);
log_debug("Opened socket '%s' as fd %d.", of->path, fd);
} else {
int flags = FLAGS_SET(of->flags, OPENFILE_READ_ONLY) ? O_RDONLY : O_RDWR;
if (FLAGS_SET(of->flags, OPENFILE_APPEND))
flags |= O_APPEND;
else if (FLAGS_SET(of->flags, OPENFILE_TRUNCATE))
flags |= O_TRUNC;
fd = fd_reopen(ofd, flags|O_NOCTTY|O_CLOEXEC);
if (fd < 0)
return log_debug_errno(fd, "Failed to reopen file '%s': %m", of->path);
log_debug("Opened file '%s' as fd %d.", of->path, fd);
}
return TAKE_FD(fd);
}
static int collect_open_file_fds(ExecParameters *p, size_t *n_fds) {
assert(p);
assert(n_fds);
LIST_FOREACH(open_files, of, p->open_files) {
_cleanup_close_ int fd = -EBADF;
fd = get_open_file_fd(of);
if (fd < 0) {
if (FLAGS_SET(of->flags, OPENFILE_GRACEFUL)) {
log_full_errno(fd == -ENOENT || ERRNO_IS_NEG_PRIVILEGE(fd) ? LOG_DEBUG : LOG_WARNING,
fd,
"Failed to get OpenFile= file descriptor for '%s', ignoring: %m",
of->path);
continue;
}
return log_error_errno(fd, "Failed to get OpenFile= file descriptor for '%s': %m", of->path);
}
if (!GREEDY_REALLOC(p->fds, *n_fds + 1))
return log_oom();
if (strv_extend(&p->fd_names, of->fdname) < 0)
return log_oom();
p->fds[(*n_fds)++] = TAKE_FD(fd);
}
return 0;
}
static void log_command_line(
const ExecContext *context,
const ExecParameters *params,
const char *msg,
const char *executable,
char **argv) {
assert(context);
assert(params);
assert(msg);
assert(executable);
if (!DEBUG_LOGGING)
return;
_cleanup_free_ char *cmdline = quote_command_line(argv, SHELL_ESCAPE_EMPTY);
log_struct(LOG_DEBUG,
LOG_ITEM("EXECUTABLE=%s", executable),
LOG_EXEC_MESSAGE(params, "%s: %s", msg, strnull(cmdline)),
LOG_EXEC_INVOCATION_ID(params));
}
static bool exec_needs_cap_sys_admin(const ExecContext *context, const ExecParameters *params) {
assert(context);
return context->private_users != PRIVATE_USERS_NO ||
context->private_tmp != PRIVATE_TMP_NO ||
context->private_devices ||
context->private_network ||
context->network_namespace_path ||
context->private_ipc ||
context->ipc_namespace_path ||
context->private_mounts > 0 ||
context->mount_apivfs > 0 ||
context->bind_log_sockets > 0 ||
context->n_bind_mounts > 0 ||
context->n_temporary_filesystems > 0 ||
context->root_directory ||
!strv_isempty(context->extension_directories) ||
context->protect_system != PROTECT_SYSTEM_NO ||
context->protect_home != PROTECT_HOME_NO ||
exec_needs_pid_namespace(context, params) ||
context->protect_kernel_tunables ||
context->protect_kernel_modules ||
context->protect_kernel_logs ||
exec_needs_cgroup_mount(context) ||
context->protect_clock ||
context->protect_hostname != PROTECT_HOSTNAME_NO ||
!strv_isempty(context->read_write_paths) ||
!strv_isempty(context->read_only_paths) ||
!strv_isempty(context->inaccessible_paths) ||
!strv_isempty(context->exec_paths) ||
!strv_isempty(context->no_exec_paths) ||
context->delegate_namespaces != NAMESPACE_FLAGS_INITIAL;
}
static PrivateUsers exec_context_get_effective_private_users(
const ExecContext *context,
const ExecParameters *params) {
assert(context);
assert(params);
if (context->private_users != PRIVATE_USERS_NO)
return context->private_users;
/* If any namespace is delegated with DelegateNamespaces=, always set up a user namespace. */
if (context->delegate_namespaces != NAMESPACE_FLAGS_INITIAL)
return PRIVATE_USERS_SELF;
return PRIVATE_USERS_NO;
}
static bool exec_namespace_is_delegated(
const ExecContext *context,
const ExecParameters *params,
bool have_cap_sys_admin,
unsigned long namespace) {
assert(context);
assert(params);
assert(namespace != CLONE_NEWUSER);
/* If we need unprivileged private users, we've already unshared a user namespace by the time we call
* setup_delegated_namespaces() for the first time so let's make sure we do all other namespace
* unsharing in the first call to setup_delegated_namespaces() by returning false here. */
if (!have_cap_sys_admin && exec_needs_cap_sys_admin(context, params))
return false;
if (context->delegate_namespaces == NAMESPACE_FLAGS_INITIAL)
return params->runtime_scope == RUNTIME_SCOPE_USER;
if (FLAGS_SET(context->delegate_namespaces, namespace))
return true;
/* Various namespaces imply mountns for private procfs/sysfs/cgroupfs instances, which means when
* those are delegated mountns must be deferred too.
*
* The list should stay in sync with exec_needs_mount_namespace(). */
if (namespace == CLONE_NEWNS)
return context->delegate_namespaces & (CLONE_NEWPID|CLONE_NEWCGROUP|CLONE_NEWNET);
return false;
}
static int setup_delegated_namespaces(
const ExecContext *context,
ExecParameters *params,
ExecRuntime *runtime,
bool delegate,
const char *memory_pressure_path,
uid_t uid,
uid_t gid,
const ExecCommand *command,
bool needs_sandboxing,
bool have_cap_sys_admin,
PidRef *bpffs_pidref,
int bpffs_socket_fd,
int bpffs_errno_pipe,
int *reterr_exit_status) {
int r;
/* This function is called twice, once before unsharing the user namespace, and once after unsharing
* the user namespace. When called before unsharing the user namespace, "delegate" is set to "false".
* When called after unsharing the user namespace, "delegate" is set to "true". The net effect is
* that all namespaces that should not be delegated are unshared when this function is called the
* first time and all namespaces that should be delegated are unshared when this function is called
* the second time. */
assert(context);
assert(params);
assert(runtime);
assert(reterr_exit_status);
if (exec_needs_network_namespace(context) &&
exec_namespace_is_delegated(context, params, have_cap_sys_admin, CLONE_NEWNET) == delegate &&
runtime->shared && runtime->shared->netns_storage_socket[0] >= 0) {
/* Try to enable network namespacing if network namespacing is available and we have
* CAP_NET_ADMIN in the current user namespace (either the system manager one or the unit's
* own user namespace). We need CAP_NET_ADMIN to be able to configure the loopback device in
* the new network namespace. And if we don't have that, then we could only create a network
* namespace without the ability to set up "lo". Hence gracefully skip things then. */
if (namespace_type_supported(NAMESPACE_NET) && have_effective_cap(CAP_NET_ADMIN) > 0) {
r = setup_shareable_ns(runtime->shared->netns_storage_socket, CLONE_NEWNET);
if (ERRNO_IS_NEG_PRIVILEGE(r))
log_notice_errno(r, "PrivateNetwork=yes is configured, but network namespace setup not permitted, proceeding without: %m");
else if (r < 0) {
*reterr_exit_status = EXIT_NETWORK;
return log_error_errno(r, "Failed to set up network namespacing: %m");
} else
log_debug("Set up %snetwork namespace", delegate ? "delegated " : "");
} else if (context->network_namespace_path) {
*reterr_exit_status = EXIT_NETWORK;
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "NetworkNamespacePath= is not supported, refusing.");
} else
log_notice("PrivateNetwork=yes is configured, but the kernel does not support or we lack privileges for network namespace, proceeding without.");
}
if (exec_needs_ipc_namespace(context) &&
exec_namespace_is_delegated(context, params, have_cap_sys_admin, CLONE_NEWIPC) == delegate &&
runtime->shared && runtime->shared->ipcns_storage_socket[0] >= 0) {
if (namespace_type_supported(NAMESPACE_IPC)) {
r = setup_shareable_ns(runtime->shared->ipcns_storage_socket, CLONE_NEWIPC);
if (ERRNO_IS_NEG_PRIVILEGE(r))
log_warning_errno(r, "PrivateIPC=yes is configured, but IPC namespace setup failed, ignoring: %m");
else if (r < 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(r, "Failed to set up IPC namespacing: %m");
} else
log_debug("Set up %sIPC namespace", delegate ? "delegated " : "");
} else if (context->ipc_namespace_path) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "IPCNamespacePath= is not supported, refusing.");
} else
log_warning("PrivateIPC=yes is configured, but the kernel does not support IPC namespaces, ignoring.");
}
if (needs_sandboxing && exec_needs_cgroup_namespace(context) &&
exec_namespace_is_delegated(context, params, have_cap_sys_admin, CLONE_NEWCGROUP) == delegate) {
if (unshare(CLONE_NEWCGROUP) < 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(errno, "Failed to set up cgroup namespacing: %m");
}
log_debug("Set up %scgroup namespace", delegate ? "delegated " : "");
}
/* Unshare a new PID namespace before setting up mounts to ensure /proc/ is mounted with only processes in PID namespace visible.
* Note PrivatePIDs=yes implies MountAPIVFS=yes so we'll always ensure procfs is remounted. */
if (needs_sandboxing && exec_needs_pid_namespace(context, params) &&
exec_namespace_is_delegated(context, params, have_cap_sys_admin, CLONE_NEWPID) == delegate) {
if (params->pidref_transport_fd < 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(SYNTHETIC_ERRNO(ENOTCONN), "PidRef socket is not set up.");
}
/* If we had CAP_SYS_ADMIN prior to joining the user namespace, then we are privileged and don't need
* to check if we can mount /proc/.
*
* We need to check prior to entering the user namespace because if we're running unprivileged or in a
* system without CAP_SYS_ADMIN, then we can have CAP_SYS_ADMIN in the current user namespace but not
* once we unshare a mount namespace. */
if (!have_cap_sys_admin || delegate) {
r = can_mount_proc();
if (r < 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(r, "Failed to detect if /proc/ can be remounted: %m");
}
if (r == 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(SYNTHETIC_ERRNO(EPERM),
"PrivatePIDs=yes is configured, but /proc/ cannot be re-mounted due to lack of privileges, refusing.");
}
}
r = setup_private_pids(context, params);
if (r < 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(r, "Failed to set up pid namespace: %m");
}
log_debug("Set up %spid namespace", delegate ? "delegated " : "");
}
/* If PrivatePIDs= yes is configured, we're now running as pid 1 in a pid namespace! */
if (exec_needs_mount_namespace(context, params, runtime) &&
exec_namespace_is_delegated(context, params, have_cap_sys_admin, CLONE_NEWNS) == delegate) {
_cleanup_free_ char *error_path = NULL;
r = apply_mount_namespace(command->flags,
context,
params,
runtime,
memory_pressure_path,
needs_sandboxing,
uid,
gid,
bpffs_pidref,
bpffs_socket_fd,
bpffs_errno_pipe,
&error_path);
if (r < 0) {
*reterr_exit_status = EXIT_NAMESPACE;
return log_error_errno(r, "Failed to set up mount namespacing%s%s: %m",
error_path ? ": " : "", strempty(error_path));
}
log_debug("Set up %smount namespace", delegate ? "delegated " : "");
}
if (needs_sandboxing &&
exec_namespace_is_delegated(context, params, have_cap_sys_admin, CLONE_NEWUTS) == delegate) {
r = apply_protect_hostname(context, params, reterr_exit_status);
if (r < 0)
return r;
if (r > 0)
log_debug("Set up %sUTS namespace", delegate ? "delegated " : "");
}
return 0;
}
static bool exec_context_shall_confirm_spawn(const ExecContext *context) {
assert(context);
if (confirm_spawn_disabled())
return false;
/* For some reasons units remaining in the same process group
* as PID 1 fail to acquire the console even if it's not used
* by any process. So skip the confirmation question for them. */
return !context->same_pgrp;
}
static int exec_context_named_iofds(
const ExecContext *c,
const ExecParameters *p,
int named_iofds[static 3]) {
size_t targets;
const char* stdio_fdname[3];
size_t n_fds;
assert(c);
assert(p);
assert(named_iofds);
targets = (c->std_input == EXEC_INPUT_NAMED_FD) +
(c->std_output == EXEC_OUTPUT_NAMED_FD) +
(c->std_error == EXEC_OUTPUT_NAMED_FD);
for (size_t i = 0; i < 3; i++)
stdio_fdname[i] = exec_context_fdname(c, i);
n_fds = p->n_storage_fds + p->n_socket_fds + p->n_extra_fds;
for (size_t i = 0; i < n_fds && targets > 0; i++)
if (named_iofds[STDIN_FILENO] < 0 &&
c->std_input == EXEC_INPUT_NAMED_FD &&
stdio_fdname[STDIN_FILENO] &&
streq(p->fd_names[i], stdio_fdname[STDIN_FILENO])) {
named_iofds[STDIN_FILENO] = p->fds[i];
targets--;
} else if (named_iofds[STDOUT_FILENO] < 0 &&
c->std_output == EXEC_OUTPUT_NAMED_FD &&
stdio_fdname[STDOUT_FILENO] &&
streq(p->fd_names[i], stdio_fdname[STDOUT_FILENO])) {
named_iofds[STDOUT_FILENO] = p->fds[i];
targets--;
} else if (named_iofds[STDERR_FILENO] < 0 &&
c->std_error == EXEC_OUTPUT_NAMED_FD &&
stdio_fdname[STDERR_FILENO] &&
streq(p->fd_names[i], stdio_fdname[STDERR_FILENO])) {
named_iofds[STDERR_FILENO] = p->fds[i];
targets--;
}
return targets == 0 ? 0 : -ENOENT;
}
static void exec_shared_runtime_close(ExecSharedRuntime *shared) {
if (!shared)
return;
safe_close_pair(shared->netns_storage_socket);
safe_close_pair(shared->ipcns_storage_socket);
}
static void exec_runtime_close(ExecRuntime *rt) {
if (!rt)
return;
safe_close_pair(rt->ephemeral_storage_socket);
exec_shared_runtime_close(rt->shared);
dynamic_creds_close(rt->dynamic_creds);
}
static void exec_params_close(ExecParameters *p) {
if (!p)
return;
p->stdin_fd = safe_close(p->stdin_fd);
p->stdout_fd = safe_close(p->stdout_fd);
p->stderr_fd = safe_close(p->stderr_fd);
}
static int exec_fd_mark_hot(
const ExecContext *c,
ExecParameters *p,
bool hot,
int *reterr_exit_status) {
assert(c);
assert(p);
if (p->exec_fd < 0)
return 0;
uint8_t x = hot;
if (write(p->exec_fd, &x, sizeof(x)) < 0) {
if (reterr_exit_status)
*reterr_exit_status = EXIT_EXEC;
return log_error_errno(errno, "Failed to mark exec_fd as %s: %m", hot ? "hot" : "cold");
}
return 1;
}
static int send_handoff_timestamp(
const ExecContext *c,
ExecParameters *p,
int *reterr_exit_status) {
assert(c);
assert(p);
if (p->handoff_timestamp_fd < 0)
return 0;
dual_timestamp dt;
dual_timestamp_now(&dt);
if (write(p->handoff_timestamp_fd, (const usec_t[2]) { dt.realtime, dt.monotonic }, sizeof(usec_t) * 2) < 0) {
if (reterr_exit_status)
*reterr_exit_status = EXIT_EXEC;
return log_error_errno(errno, "Failed to send handoff timestamp: %m");
}
return 1;
}
static void prepare_terminal(
const ExecContext *context,
ExecParameters *p) {
_cleanup_close_ int lock_fd = -EBADF;
/* This is the "constructive" reset, i.e. is about preparing things for our invocation rather than
* cleaning up things from older invocations. */
assert(context);
assert(p);
/* We only try to reset things if we there's the chance our stdout points to a TTY */
if (!(context->std_output == EXEC_OUTPUT_TTY ||
(context->std_output == EXEC_OUTPUT_INHERIT && exec_input_is_terminal(context->std_input)) ||
context->std_output == EXEC_OUTPUT_NAMED_FD ||
p->stdout_fd >= 0))
return;
/* Let's explicitly determine whether to reset via ANSI sequences or not, taking our ExecContext
* information into account */
bool use_ansi = exec_context_shall_ansi_seq_reset(context);
if (context->tty_reset) {
/* When we are resetting the TTY, then let's create a lock first, to synchronize access. This
* in particular matters as concurrent resets and the TTY size ANSI DSR logic done by the
* exec_context_apply_tty_size() below might interfere */
lock_fd = lock_dev_console();
if (lock_fd < 0)
log_debug_errno(lock_fd, "Failed to lock /dev/console, ignoring: %m");
/* We explicitly control whether to send ansi sequences or not here, since we want to consult
* the env vars explicitly configured in the ExecContext, rather than our own environment
* block. */
(void) terminal_reset_defensive(STDOUT_FILENO, use_ansi ? TERMINAL_RESET_FORCE_ANSI_SEQ : TERMINAL_RESET_AVOID_ANSI_SEQ);
}
(void) exec_context_apply_tty_size(context, STDIN_FILENO, STDOUT_FILENO, /* tty_path= */ NULL);
if (use_ansi)
(void) osc_context_open_service(p->unit_id, p->invocation_id, /* ret_seq= */ NULL);
}
static int setup_term_environment(const ExecContext *context, char ***env) {
int r;
assert(context);
assert(env);
/* Already specified by user? */
if (strv_env_get(*env, "TERM"))
return 0;
/* Do we need $TERM at all? */
if (!exec_context_has_tty(context))
return 0;
const char *tty_path = exec_context_tty_path(context);
if (tty_path) {
/* If we are forked off PID 1 and we are supposed to operate on /dev/console, then let's try
* to inherit the $TERM set for PID 1. This is useful for containers so that the $TERM the
* container manager passes to PID 1 ends up all the way in the console login shown.
*
* Note that if this doesn't work out we won't bother with querying systemd.tty.term.console
* kernel cmdline option or DCS anymore either, because pid1 also imports $TERM based on those
* and it should have showed up as our $TERM if there were anything. */
if (tty_is_console(tty_path) && getppid() == 1) {
const char *term = strv_find_prefix(environ, "TERM=");
if (term) {
r = strv_env_replace_strdup(env, term);
if (r < 0)
return r;
FOREACH_STRING(i, "COLORTERM=", "NO_COLOR=") {
const char *s = strv_find_prefix(environ, i);
if (!s)
continue;
r = strv_env_replace_strdup(env, s);
if (r < 0)
return r;
}
return 1;
}
} else {
if (in_charset(skip_dev_prefix(tty_path), ALPHANUMERICAL)) {
_cleanup_free_ char *key = NULL, *cmdline = NULL;
key = strjoin("systemd.tty.term.", skip_dev_prefix(tty_path));
if (!key)
return -ENOMEM;
r = proc_cmdline_get_key(key, /* flags = */ 0, &cmdline);
if (r > 0)
return strv_env_assign(env, "TERM", cmdline);
if (r < 0)
log_debug_errno(r, "Failed to read '%s' from kernel cmdline, ignoring: %m", key);
}
/* This handles real virtual terminals (returning "linux") and
* any terminals which support the DCS +q query sequence. */
_cleanup_free_ char *dcs_term = NULL;
r = query_term_for_tty(tty_path, &dcs_term);
if (r >= 0)
return strv_env_assign(env, "TERM", dcs_term);
}
}
/* If $TERM is not known and we pick a fallback default, then let's also set
* $COLORTERM=truecolor. That's because our fallback default is vt220, which is
* generally a safe bet (as it supports PageUp/PageDown unlike vt100, and is quite
* universally available in terminfo/termcap), except for the fact that real DEC
* vt220 gear never actually supported color. Most tools these days generate color on
* vt220 anyway, ignoring the physical capabilities of the real hardware, but some
* tools actually believe in the historical truth. Which is unfortunate since *we*
* *don't* care about the historical truth, we just want sane defaults if nothing
* better is explicitly configured. It's 2025 after all, at the time of writing,
* pretty much all terminal emulators actually *do* support color, hence if we don't
* know any better let's explicitly claim color support via $COLORTERM. Or in other
* words: we now explicitly claim to be connected to a franken-vt220 with true color
* support. */
r = strv_env_replace_strdup(env, "COLORTERM=truecolor");
if (r < 0)
return r;
return strv_env_replace_strdup(env, "TERM=" FALLBACK_TERM);
}
int exec_invoke(
const ExecCommand *command,
const ExecContext *context,
ExecParameters *params,
ExecRuntime *runtime,
const CGroupContext *cgroup_context,
int *exit_status) {
_cleanup_strv_free_ char **our_env = NULL, **pass_env = NULL, **joined_exec_search_path = NULL, **accum_env = NULL;
int r;
const char *username = NULL, *groupname = NULL;
_cleanup_free_ char *home_buffer = NULL, *memory_pressure_path = NULL, *own_user = NULL;
const char *pwent_home = NULL, *shell = NULL;
dev_t journal_stream_dev = 0;
ino_t journal_stream_ino = 0;
bool needs_sandboxing, /* Do we need to set up full sandboxing? (i.e. all namespacing, all MAC stuff, caps, yadda yadda */
needs_setuid, /* Do we need to do the actual setresuid()/setresgid() calls? */
needs_mount_namespace, /* Do we need to set up a mount namespace for this kernel? */
have_cap_sys_admin,
userns_set_up = false,
keep_seccomp_privileges = false;
#if HAVE_SELINUX
_cleanup_free_ char *mac_selinux_context_net = NULL;
bool use_selinux = false;
#endif
#if ENABLE_SMACK
bool use_smack = false;
#endif
#if HAVE_APPARMOR
bool use_apparmor = false;
#endif
#if HAVE_SECCOMP
uint64_t saved_bset = 0;
#endif
uid_t saved_uid = getuid();
gid_t saved_gid = getgid();
uid_t uid = UID_INVALID;
gid_t gid = GID_INVALID;
size_t n_fds, /* fds to pass to the child */
n_keep_fds; /* total number of fds not to close */
int secure_bits;
_cleanup_free_ gid_t *gids = NULL, *gids_after_pam = NULL;
int ngids = 0, ngids_after_pam = 0;
int socket_fd = -EBADF, named_iofds[3] = EBADF_TRIPLET;
_cleanup_close_ int bpffs_socket_fd = -EBADF, bpffs_errno_pipe = -EBADF;
size_t n_storage_fds, n_socket_fds, n_extra_fds;
_cleanup_(pidref_done_sigkill_wait) PidRef bpffs_pidref = PIDREF_NULL;
assert(command);
assert(context);
assert(params);
assert(runtime);
assert(cgroup_context);
assert(exit_status);
LOG_CONTEXT_PUSH_EXEC(context, params);
/* Explicitly test for CVE-2021-4034 inspired invocations */
if (!command->path || strv_isempty(command->argv)) {
*exit_status = EXIT_EXEC;
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid command line arguments.");
}
if (context->std_input == EXEC_INPUT_SOCKET ||
context->std_output == EXEC_OUTPUT_SOCKET ||
context->std_error == EXEC_OUTPUT_SOCKET) {
if (params->n_socket_fds > 1)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Got more than one socket.");
if (params->n_socket_fds == 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Got no socket.");
socket_fd = params->fds[0];
n_storage_fds = n_socket_fds = n_extra_fds = 0;
} else {
n_socket_fds = params->n_socket_fds;
n_storage_fds = params->n_storage_fds;
n_extra_fds = params->n_extra_fds;
}
n_fds = n_socket_fds + n_storage_fds + n_extra_fds;
r = exec_context_named_iofds(context, params, named_iofds);
if (r < 0)
return log_error_errno(r, "Failed to load a named file descriptor: %m");
rename_process_from_path(command->path);
/* We reset exactly these signals, since they are the only ones we set to SIG_IGN in the main
* daemon. All others we leave untouched because we set them to SIG_DFL or a valid handler initially,
* both of which will be demoted to SIG_DFL. */
(void) default_signals(SIGNALS_CRASH_HANDLER,
SIGNALS_IGNORE);
if (context->ignore_sigpipe)
(void) ignore_signals(SIGPIPE);
r = reset_signal_mask();
if (r < 0) {
*exit_status = EXIT_SIGNAL_MASK;
return log_error_errno(r, "Failed to set process signal mask: %m");
}
if (params->idle_pipe)
do_idle_pipe_dance(params->idle_pipe);
/* Close fds we don't need very early to make sure we don't block init reexecution because it cannot bind its
* sockets. Among the fds we close are the logging fds, and we want to keep them closed, so that we don't have
* any fds open we don't really want open during the transition. In order to make logging work, we switch the
* log subsystem into open_when_needed mode, so that it reopens the logs on every single log call. */
log_forget_fds();
log_set_open_when_needed(true);
log_settle_target();
/* In case anything used libc syslog(), close this here, too */
closelog();
r = collect_open_file_fds(params, &n_fds);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to get OpenFile= file descriptors: %m");
}
int keep_fds[n_fds + 4];
memcpy_safe(keep_fds, params->fds, n_fds * sizeof(int));
n_keep_fds = n_fds;
r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &params->exec_fd);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to collect shifted fd: %m");
}
r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &params->handoff_timestamp_fd);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to collect shifted fd: %m");
}
#if HAVE_LIBBPF
r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &params->bpf_restrict_fs_map_fd);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to collect shifted fd: %m");
}
#endif
r = close_remaining_fds(params, runtime, socket_fd, keep_fds, n_keep_fds);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to close unwanted file descriptors: %m");
}
if (!context->same_pgrp &&
setsid() < 0) {
*exit_status = EXIT_SETSID;
return log_error_errno(errno, "Failed to create new process session: %m");
}
/* Now, reset the TTY associated to this service "destructively" (i.e. possibly even hang up or
* disallocate the VT), to get rid of any prior uses of the device. Note that we do not keep any fd
* open here, hence some of the settings made here might vanish again, depending on the TTY driver
* used. A 2nd ("constructive") initialization after we opened the input/output fds we actually want
* will fix this. Note that we pass a NULL invocation ID here – as exec_context_tty_reset() expects
* the invocation ID associated with the OSC 3008 context ID to close. But we don't want to close any
* OSC 3008 context here, and opening a fresh OSC 3008 context happens a bit further down. */
exec_context_tty_reset(context, params, /* invocation_id= */ SD_ID128_NULL);
if (params->shall_confirm_spawn && exec_context_shall_confirm_spawn(context)) {
_cleanup_free_ char *cmdline = NULL;
cmdline = quote_command_line(command->argv, SHELL_ESCAPE_EMPTY);
if (!cmdline) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
r = ask_for_confirmation(context, params, cmdline);
if (r != CONFIRM_EXECUTE) {
if (r == CONFIRM_PRETEND_SUCCESS) {
*exit_status = EXIT_SUCCESS;
return 0;
}
*exit_status = EXIT_CONFIRM;
return log_error_errno(SYNTHETIC_ERRNO(ECANCELED), "Execution cancelled by the user.");
}
}
/* We are about to invoke NSS and PAM modules. Let's tell them what we are doing here, maybe they care. This is
* used by nss-resolve to disable itself when we are about to start systemd-resolved, to avoid deadlocks. Note
* that these env vars do not survive the execve(), which means they really only apply to the PAM and NSS
* invocations themselves. Also note that while we'll only invoke NSS modules involved in user management they
* might internally call into other NSS modules that are involved in hostname resolution, we never know. */
if (setenv("SYSTEMD_ACTIVATION_UNIT", params->unit_id, true) != 0 ||
setenv("SYSTEMD_ACTIVATION_SCOPE", runtime_scope_to_string(params->runtime_scope), true) != 0) {
*exit_status = EXIT_MEMORY;
return log_error_errno(errno, "Failed to update environment: %m");
}
if (context->dynamic_user && runtime->dynamic_creds) {
_cleanup_strv_free_ char **suggested_paths = NULL;
/* On top of that, make sure we bypass our own NSS module nss-systemd comprehensively for any NSS
* checks, if DynamicUser=1 is used, as we shouldn't create a feedback loop with ourselves here. */
if (putenv((char*) "SYSTEMD_NSS_DYNAMIC_BYPASS=1") != 0) {
*exit_status = EXIT_USER;
return log_error_errno(errno, "Failed to update environment: %m");
}
r = compile_suggested_paths(context, params, &suggested_paths);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
r = dynamic_creds_realize(runtime->dynamic_creds, suggested_paths, &uid, &gid);
if (r < 0) {
*exit_status = EXIT_USER;
if (r == -EILSEQ)
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
"Failed to update dynamic user credentials: User or group with specified name already exists.");
return log_error_errno(r, "Failed to update dynamic user credentials: %m");
}
if (!uid_is_valid(uid)) {
*exit_status = EXIT_USER;
return log_error_errno(SYNTHETIC_ERRNO(ESRCH), "UID validation failed for \""UID_FMT"\".", uid);
}
if (!gid_is_valid(gid)) {
*exit_status = EXIT_USER;
return log_error_errno(SYNTHETIC_ERRNO(ESRCH), "GID validation failed for \""GID_FMT"\".", gid);
}
if (runtime->dynamic_creds->user)
username = runtime->dynamic_creds->user->name;
} else {
const char *u;
if (context->user)
u = context->user;
else if (context->pam_name || FLAGS_SET(command->flags, EXEC_COMMAND_VIA_SHELL)) {
/* If PAM is enabled but no user name is explicitly selected, then use our own one. */
own_user = getusername_malloc();
if (!own_user) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to determine my own user ID: %m");
}
u = own_user;
} else
u = NULL;
if (u) {
/* We can't use nss unconditionally for root without risking deadlocks if some IPC services
* will be started by pid1 and are ordered after us. But if SetLoginEnvironment= is
* enabled *explicitly* (i.e. no exec_context_get_set_login_environment() here),
* or PAM shall be invoked, let's consult NSS even for root, so that the user
* gets accurate $SHELL in session(-like) contexts. */
r = get_fixed_user(u,
/* prefer_nss = */ context->set_login_environment > 0 || context->pam_name,
&username, &uid, &gid, &pwent_home, &shell);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to determine user credentials: %m");
}
}
if (context->group) {
r = get_fixed_group(context->group, &groupname, &gid);
if (r < 0) {
*exit_status = EXIT_GROUP;
return log_error_errno(r, "Failed to determine group credentials: %m");
}
}
}
/* Initialize user supplementary groups and get SupplementaryGroups= ones */
ngids = get_supplementary_groups(context, username, gid, &gids);
if (ngids < 0) {
*exit_status = EXIT_GROUP;
return log_error_errno(ngids, "Failed to determine supplementary groups: %m");
}
r = send_user_lookup(params->unit_id, params->user_lookup_fd, uid, gid);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to send user credentials to PID1: %m");
}
params->user_lookup_fd = safe_close(params->user_lookup_fd);
r = acquire_home(context, &pwent_home, &home_buffer);
if (r < 0) {
*exit_status = EXIT_CHDIR;
return log_error_errno(r, "Failed to determine $HOME for the invoking user: %m");
}
/* If a socket is connected to STDIN/STDOUT/STDERR, we must drop O_NONBLOCK */
if (socket_fd >= 0)
(void) fd_nonblock(socket_fd, false);
/* We need sandboxing if the caller asked us to apply it and the command isn't explicitly excepted
* from it. */
needs_sandboxing = (params->flags & EXEC_APPLY_SANDBOXING) && !(command->flags & EXEC_COMMAND_FULLY_PRIVILEGED);
/* Journald will try to look-up our cgroup in order to populate _SYSTEMD_CGROUP and _SYSTEMD_UNIT fields.
* Hence we need to migrate to the target cgroup from init.scope before connecting to journald */
if (params->cgroup_path) {
_cleanup_free_ char *subcgroup = NULL;
r = exec_params_get_cgroup_path(params, cgroup_context, params->cgroup_path, &subcgroup);
if (r < 0) {
*exit_status = EXIT_CGROUP;
return log_error_errno(r, "Failed to acquire cgroup path: %m");
}
if (r > 0) {
/* If there is a subcgroup required, let's make sure to create it now. */
r = cg_create(subcgroup);
if (r < 0)
return log_error_errno(r, "Failed to create subcgroup '%s': %m", subcgroup);
}
/* If we need a cgroup namespace, we cannot yet move the service to its configured subgroup,
* as unsharing the cgroup namespace later on makes the current cgroup the root of the
* namespace and we want the root of the namespace to be the main service cgroup and not the
* subgroup. One edge case is if we're a control process that needs to be spawned in a
* subgroup, in this case, we have no choice as moving into the main service cgroup might
* violate the no inner processes rule of cgroupv2. */
const char *cgtarget = needs_sandboxing && exec_needs_cgroup_namespace(context) &&
!exec_params_needs_control_subcgroup(params)
? params->cgroup_path : subcgroup;
r = cg_attach(cgtarget, 0);
if (r == -EUCLEAN) {
*exit_status = EXIT_CGROUP;
return log_error_errno(r,
"Failed to attach process to cgroup '%s', "
"because the cgroup or one of its parents or "
"siblings is in the threaded mode.", cgtarget);
}
if (r < 0) {
*exit_status = EXIT_CGROUP;
return log_error_errno(r, "Failed to attach to cgroup %s: %m", cgtarget);
}
}
if (context->network_namespace_path && runtime->shared && runtime->shared->netns_storage_socket[0] >= 0) {
r = open_shareable_ns_path(runtime->shared->netns_storage_socket, context->network_namespace_path, CLONE_NEWNET);
if (r < 0) {
*exit_status = EXIT_NETWORK;
return log_error_errno(r, "Failed to open network namespace path %s: %m", context->network_namespace_path);
}
}
if (context->ipc_namespace_path && runtime->shared && runtime->shared->ipcns_storage_socket[0] >= 0) {
r = open_shareable_ns_path(runtime->shared->ipcns_storage_socket, context->ipc_namespace_path, CLONE_NEWIPC);
if (r < 0) {
*exit_status = EXIT_NAMESPACE;
return log_error_errno(r, "Failed to open IPC namespace path %s: %m", context->ipc_namespace_path);
}
}
r = setup_input(context, params, socket_fd, named_iofds);
if (r < 0) {
*exit_status = EXIT_STDIN;
return log_error_errno(r, "Failed to set up standard input: %m");
}
_cleanup_free_ char *fname = NULL;
r = path_extract_filename(command->path, &fname);
if (r < 0) {
*exit_status = EXIT_STDOUT;
return log_error_errno(r, "Failed to extract filename from path %s: %m", command->path);
}
r = setup_output(context, params, STDOUT_FILENO, socket_fd, named_iofds, fname, uid, gid, &journal_stream_dev, &journal_stream_ino);
if (r < 0) {
*exit_status = EXIT_STDOUT;
return log_error_errno(r, "Failed to set up standard output: %m");
}
r = setup_output(context, params, STDERR_FILENO, socket_fd, named_iofds, fname, uid, gid, &journal_stream_dev, &journal_stream_ino);
if (r < 0) {
*exit_status = EXIT_STDERR;
return log_error_errno(r, "Failed to set up standard error output: %m");
}
/* Now that stdin/stdout are definiely opened, properly initialize it with our desired
* settings. Note: this is a "constructive" reset, it prepares things for us to use. This is
* different from the "destructive" TTY reset further up. Also note: we apply this on stdin/stdout in
* case this is a tty, regardless if we opened it ourselves or got it passed in pre-opened. */
prepare_terminal(context, params);
if (context->oom_score_adjust_set) {
/* When we can't make this change due to EPERM, then let's silently skip over it. User
* namespaces prohibit write access to this file, and we shouldn't trip up over that. */
r = set_oom_score_adjust(context->oom_score_adjust);
if (ERRNO_IS_NEG_PRIVILEGE(r))
log_debug_errno(r, "Failed to adjust OOM setting, assuming containerized execution, ignoring: %m");
else if (r < 0) {
*exit_status = EXIT_OOM_ADJUST;
return log_error_errno(r, "Failed to adjust OOM setting: %m");
}
}
if (context->coredump_filter_set) {
r = set_coredump_filter(context->coredump_filter);
if (ERRNO_IS_NEG_PRIVILEGE(r))
log_debug_errno(r, "Failed to adjust coredump_filter, ignoring: %m");
else if (r < 0) {
*exit_status = EXIT_LIMITS;
return log_error_errno(r, "Failed to adjust coredump_filter: %m");
}
}
if (context->cpu_sched_set) {
struct sched_attr attr = {
.size = sizeof(attr),
.sched_policy = context->cpu_sched_policy,
.sched_priority = context->cpu_sched_priority,
.sched_flags = context->cpu_sched_reset_on_fork ? SCHED_FLAG_RESET_ON_FORK : 0,
};
r = sched_setattr(/* pid= */ 0, &attr, /* flags= */ 0);
if (r < 0) {
*exit_status = EXIT_SETSCHEDULER;
return log_error_errno(errno, "Failed to set up CPU scheduling: %m");
}
}
/*
* Set nice value _after_ the call to sched_setattr() because struct sched_attr includes sched_nice
* which we do not set, thus it will clobber any previously set nice value. Scheduling policy might
* be reasonably set together with nice value e.g. in case of SCHED_BATCH (see sched(7)).
* It would be ideal to set both with the same call, but we cannot easily do so because of all the
* extra logic in setpriority_closest().
*/
if (context->nice_set) {
r = setpriority_closest(context->nice);
if (r < 0) {
*exit_status = EXIT_NICE;
return log_error_errno(r, "Failed to set up process scheduling priority (nice level): %m");
}
}
if (context->cpu_affinity_from_numa || context->cpu_set.set) {
_cleanup_(cpu_set_done) CPUSet converted_cpu_set = {};
const CPUSet *cpu_set;
if (context->cpu_affinity_from_numa) {
r = exec_context_cpu_affinity_from_numa(context, &converted_cpu_set);
if (r < 0) {
*exit_status = EXIT_CPUAFFINITY;
return log_error_errno(r, "Failed to derive CPU affinity mask from NUMA mask: %m");
}
cpu_set = &converted_cpu_set;
} else
cpu_set = &context->cpu_set;
if (sched_setaffinity(0, cpu_set->allocated, cpu_set->set) < 0) {
*exit_status = EXIT_CPUAFFINITY;
return log_error_errno(errno, "Failed to set up CPU affinity: %m");
}
}
if (mpol_is_valid(numa_policy_get_type(&context->numa_policy))) {
r = apply_numa_policy(&context->numa_policy);
if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
log_debug_errno(r, "NUMA support not available, ignoring.");
else if (r < 0) {
*exit_status = EXIT_NUMA_POLICY;
return log_error_errno(r, "Failed to set NUMA memory policy: %m");
}
}
if (context->ioprio_is_set)
if (ioprio_set(IOPRIO_WHO_PROCESS, 0, context->ioprio) < 0) {
*exit_status = EXIT_IOPRIO;
return log_error_errno(errno, "Failed to set up IO scheduling priority: %m");
}
if (context->timer_slack_nsec != NSEC_INFINITY)
if (prctl(PR_SET_TIMERSLACK, context->timer_slack_nsec) < 0) {
*exit_status = EXIT_TIMERSLACK;
return log_error_errno(errno, "Failed to set up timer slack: %m");
}
if (context->personality != PERSONALITY_INVALID) {
r = safe_personality(context->personality);
if (r < 0) {
*exit_status = EXIT_PERSONALITY;
return log_error_errno(r, "Failed to set up execution domain (personality): %m");
}
}
if (context->memory_ksm >= 0)
if (prctl(PR_SET_MEMORY_MERGE, context->memory_ksm, 0, 0, 0) < 0) {
if (ERRNO_IS_NOT_SUPPORTED(errno))
log_debug_errno(errno, "KSM support not available, ignoring.");
else {
*exit_status = EXIT_KSM;
return log_error_errno(errno, "Failed to set KSM: %m");
}
}
#if ENABLE_UTMP
if (context->utmp_id) {
_cleanup_free_ char *username_alloc = NULL;
if (!username && context->utmp_mode == EXEC_UTMP_USER) {
username_alloc = uid_to_name(uid_is_valid(uid) ? uid : saved_uid);
if (!username_alloc) {
*exit_status = EXIT_USER;
return log_oom();
}
}
const char *line = context->tty_path ?
(path_startswith(context->tty_path, "/dev/") ?: context->tty_path) :
NULL;
utmp_put_init_process(context->utmp_id, getpid_cached(), getsid(0),
line,
context->utmp_mode == EXEC_UTMP_INIT ? INIT_PROCESS :
context->utmp_mode == EXEC_UTMP_LOGIN ? LOGIN_PROCESS :
USER_PROCESS,
username ?: username_alloc);
}
#endif
if (uid_is_valid(uid)) {
r = chown_terminal(STDIN_FILENO, uid);
if (r < 0) {
*exit_status = EXIT_STDIN;
return log_error_errno(r, "Failed to change ownership of terminal: %m");
}
}
if (params->cgroup_path) {
/* If delegation is enabled we'll pass ownership of the cgroup to the user of the new process. On cgroup v1
* this is only about systemd's own hierarchy, i.e. not the controller hierarchies, simply because that's not
* safe. On cgroup v2 there's only one hierarchy anyway, and delegation is safe there, hence in that case only
* touch a single hierarchy too. */
if (params->flags & EXEC_CGROUP_DELEGATE) {
_cleanup_free_ char *p = NULL;
r = cg_set_access(params->cgroup_path, uid, gid);
if (r < 0) {
*exit_status = EXIT_CGROUP;
return log_error_errno(r, "Failed to adjust control group access: %m");
}
r = exec_params_get_cgroup_path(params, cgroup_context, params->cgroup_path, &p);
if (r < 0) {
*exit_status = EXIT_CGROUP;
return log_error_errno(r, "Failed to acquire cgroup path: %m");
}
if (r > 0) {
r = cg_set_access_recursive(p, uid, gid);
if (r < 0) {
*exit_status = EXIT_CGROUP;
return log_error_errno(r, "Failed to adjust control subgroup access: %m");
}
}
}
if (is_pressure_supported() > 0) {
if (cgroup_context_want_memory_pressure(cgroup_context)) {
r = cg_get_path("memory", params->cgroup_path, "memory.pressure", &memory_pressure_path);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
r = chmod_and_chown(memory_pressure_path, 0644, uid, gid);
if (r < 0) {
log_full_errno(r == -ENOENT || ERRNO_IS_PRIVILEGE(r) ? LOG_DEBUG : LOG_WARNING, r,
"Failed to adjust ownership of '%s', ignoring: %m", memory_pressure_path);
memory_pressure_path = mfree(memory_pressure_path);
}
/* First we use the current cgroup path to chmod and chown the memory pressure path, then pass the path relative
* to the cgroup namespace to environment variables and mounts. If chown/chmod fails, we should not pass memory
* pressure path environment variable or read-write mount to the unit. This is why we check if
* memory_pressure_path != NULL in the conditional below. */
if (memory_pressure_path && needs_sandboxing && exec_needs_cgroup_namespace(context)) {
memory_pressure_path = mfree(memory_pressure_path);
r = cg_get_path("memory", "/", "memory.pressure", &memory_pressure_path);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
}
} else if (cgroup_context->memory_pressure_watch == CGROUP_PRESSURE_WATCH_NO) {
memory_pressure_path = strdup("/dev/null"); /* /dev/null is explicit indicator for turning of memory pressure watch */
if (!memory_pressure_path) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
}
}
}
needs_mount_namespace = exec_needs_mount_namespace(context, params, runtime);
for (ExecDirectoryType dt = 0; dt < _EXEC_DIRECTORY_TYPE_MAX; dt++) {
r = setup_exec_directory(context, params, uid, gid, dt, needs_mount_namespace, exit_status);
if (r < 0)
return log_error_errno(r, "Failed to set up special execution directory in %s: %m", params->prefix[dt]);
}
r = exec_setup_credentials(context, cgroup_context, params, params->unit_id, uid, gid);
if (r < 0) {
*exit_status = EXIT_CREDENTIALS;
return log_error_errno(r, "Failed to set up credentials: %m");
}
r = build_environment(
context,
params,
cgroup_context,
n_fds,
pwent_home,
username,
shell,
journal_stream_dev,
journal_stream_ino,
memory_pressure_path,
needs_sandboxing,
&our_env);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
r = build_pass_environment(context, &pass_env);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
/* The $PATH variable is set to the default path in params->environment. However, this is overridden
* if user-specified fields have $PATH set. The intention is to also override $PATH if the unit does
* not specify PATH but the unit has ExecSearchPath. */
if (!strv_isempty(context->exec_search_path)) {
_cleanup_free_ char *joined = NULL;
joined = strv_join(context->exec_search_path, ":");
if (!joined) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
r = strv_env_assign(&joined_exec_search_path, "PATH", joined);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
}
accum_env = strv_env_merge(params->environment,
our_env,
joined_exec_search_path,
pass_env,
context->environment,
params->files_env);
if (!accum_env) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
strv_env_clean(accum_env);
(void) umask(context->umask);
r = setup_term_environment(context, &accum_env);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_error_errno(r, "Failed to construct $TERM: %m");
}
r = setup_keyring(context, params, uid, gid);
if (r < 0) {
*exit_status = EXIT_KEYRING;
return log_error_errno(r, "Failed to set up kernel keyring: %m");
}
/* We need setresuid() if the caller asked us to apply sandboxing and the command isn't explicitly
* excepted from either whole sandboxing or just setresuid() itself. */
needs_setuid = (params->flags & EXEC_APPLY_SANDBOXING) && !(command->flags & (EXEC_COMMAND_FULLY_PRIVILEGED|EXEC_COMMAND_NO_SETUID));
uint64_t capability_ambient_set = context->capability_ambient_set;
/* Check CAP_SYS_ADMIN before we enter user namespace to see if we can mount /proc even though its masked. */
have_cap_sys_admin = have_effective_cap(CAP_SYS_ADMIN) > 0;
if (needs_sandboxing) {
/* MAC enablement checks need to be done before a new mount ns is created, as they rely on
* /sys being present. The actual MAC context application will happen later, as late as
* possible, to avoid impacting our own code paths. */
#if HAVE_SELINUX
use_selinux = mac_selinux_use();
#endif
#if ENABLE_SMACK
use_smack = mac_smack_use();
#endif
#if HAVE_APPARMOR
if (mac_apparmor_use()) {
r = dlopen_libapparmor();
if (r < 0 && !ERRNO_IS_NEG_NOT_SUPPORTED(r))
log_warning_errno(r, "Failed to load libapparmor, ignoring: %m");
use_apparmor = r >= 0;
}
#endif
}
if (needs_sandboxing) {
int which_failed;
/* Let's set the resource limits before we call into PAM, so that pam_limits wins over what
* is set here. (See below.) */
r = setrlimit_closest_all((const struct rlimit* const *) context->rlimit, &which_failed);
if (r < 0) {
*exit_status = EXIT_LIMITS;
return log_error_errno(r, "Failed to adjust resource limit RLIMIT_%s: %m", rlimit_to_string(which_failed));
}
}
if (needs_setuid && context->pam_name && username) {
/* Let's call into PAM after we set up our own idea of resource limits so that pam_limits
* wins here. (See above.) */
/* All fds passed in the fds array will be closed in the pam child process. */
r = setup_pam(context, cgroup_context, params, username, uid, gid, &accum_env,
params->fds, n_fds, needs_sandboxing, params->exec_fd);
if (r < 0) {
*exit_status = EXIT_PAM;
return log_error_errno(r, "Failed to set up PAM session: %m");
}
/* PAM modules might have set some ambient caps. Query them here and merge them into
* the caps we want to set in the end, so that we don't end up unsetting them. */
uint64_t ambient_after_pam;
r = capability_get_ambient(&ambient_after_pam);
if (r < 0) {
*exit_status = EXIT_CAPABILITIES;
return log_error_errno(r, "Failed to query ambient caps: %m");
}
capability_ambient_set |= ambient_after_pam;
ngids_after_pam = getgroups_alloc(&gids_after_pam);
if (ngids_after_pam < 0) {
*exit_status = EXIT_GROUP;
return log_error_errno(ngids_after_pam, "Failed to obtain groups after setting up PAM: %m");
}
}
if (context->private_bpf != PRIVATE_BPF_NO) {
/* To create a BPF token, the bpffs has to be mounted with the fsopen()/fsmount() API.
* More specifically, fsopen() must be called within the user namespace, then all the
* fsconfig() as privileged user, and finally and fsmount() and move_mount() in
* the user namespace.
* To do this, we split the code into a bpffs_prepare() and mount_bpffs() functions,
* the first runs as privileged user the second as unprivileged one, and they coordinate
* by sending messages and file descriptors via a socket pair.
* The user and mount namespaces need to be unshared in this exact order and before
* the fsopen() call for the fsopen() API to work as unprivileged.
* This is the kernel sample doing this:
* https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/prog_tests/token.c
*/
r = bpffs_prepare(context, &bpffs_pidref, &bpffs_socket_fd, &bpffs_errno_pipe);
if (r < 0) {
*exit_status = EXIT_BPF;
return log_error_errno(r, "Failed to mount bpffs in bpffs_prepare(): %m");
}
}
if (needs_sandboxing && !have_cap_sys_admin && exec_needs_cap_sys_admin(context, params)) {
/* If we're unprivileged, set up the user namespace first to enable use of the other namespaces.
* Users with CAP_SYS_ADMIN can set up user namespaces last because they will be able to
* set up all of the other namespaces (i.e. network, mount, UTS) without a user namespace. */
PrivateUsers pu = exec_context_get_effective_private_users(context, params);
if (pu == PRIVATE_USERS_NO)
pu = PRIVATE_USERS_SELF;
/* The kernel requires /proc/pid/setgroups be set to "deny" prior to writing /proc/pid/gid_map in
* unprivileged user namespaces. */
r = setup_private_users(pu, saved_uid, saved_gid, uid, gid, /* allow_setgroups= */ false);
/* If it was requested explicitly and we can't set it up, fail early. Otherwise, continue and let
* the actual requested operations fail (or silently continue). */
if (r < 0 && context->private_users != PRIVATE_USERS_NO) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to set up user namespacing for unprivileged user: %m");
}
if (r < 0)
log_info_errno(r, "Failed to set up user namespacing for unprivileged user, ignoring: %m");
else {
assert(r > 0);
userns_set_up = true;
log_debug("Set up unprivileged user namespace");
}
}
/* Call setup_delegated_namespaces() the first time to unshare all non-delegated namespaces. */
r = setup_delegated_namespaces(
context,
params,
runtime,
/* delegate= */ false,
memory_pressure_path,
uid,
gid,
command,
needs_sandboxing,
have_cap_sys_admin,
&bpffs_pidref,
bpffs_socket_fd,
bpffs_errno_pipe,
exit_status);
if (r < 0)
return r;
/* Drop groups as early as possible.
* This needs to be done after PrivateDevices=yes setup as device nodes should be owned by the host's root.
* For non-root in a userns, devices will be owned by the user/group before the group change, and nobody. */
if (needs_setuid) {
_cleanup_free_ gid_t *gids_to_enforce = NULL;
int ngids_to_enforce;
ngids_to_enforce = merge_gid_lists(gids,
ngids,
gids_after_pam,
ngids_after_pam,
&gids_to_enforce);
if (ngids_to_enforce < 0) {
*exit_status = EXIT_GROUP;
return log_error_errno(ngids_to_enforce, "Failed to merge group lists. Group membership might be incorrect: %m");
}
r = enforce_groups(gid, gids_to_enforce, ngids_to_enforce);
if (r < 0) {
*exit_status = EXIT_GROUP;
return log_error_errno(r, "Changing group credentials failed: %m");
}
}
/* If the user namespace was not set up above, try to do it now.
* It's preferred to set up the user namespace later (after all other namespaces) so as not to be
* restricted by rules pertaining to combining user namespaces with other namespaces (e.g. in the
* case of mount namespaces being less privileged when the mount point list is copied from a
* different user namespace). */
if (needs_sandboxing && !userns_set_up) {
PrivateUsers pu = exec_context_get_effective_private_users(context, params);
r = setup_private_users(pu, saved_uid, saved_gid, uid, gid,
/* allow_setgroups= */ pu == PRIVATE_USERS_FULL);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to set up user namespacing: %m");
}
if (r > 0)
log_debug("Set up privileged user namespace");
}
/* Call setup_delegated_namespaces() the second time to unshare all delegated namespaces. */
r = setup_delegated_namespaces(
context,
params,
runtime,
/* delegate= */ true,
memory_pressure_path,
uid,
gid,
command,
needs_sandboxing,
have_cap_sys_admin,
&bpffs_pidref,
bpffs_socket_fd,
bpffs_errno_pipe,
exit_status);
if (r < 0)
return r;
/* Kill unnecessary process, for the case that e.g. when the bpffs mount point is hidden. */
pidref_done_sigkill_wait(&bpffs_pidref);
if (needs_sandboxing && exec_needs_cgroup_namespace(context) && params->cgroup_path) {
/* Move ourselves into the subcgroup now *after* we've unshared the cgroup namespace, which
* ensures the root of the cgroup namespace is the top level service cgroup and not the
* subcgroup. Adjust the prefix accordingly since we're in a cgroup namespace now. */
r = attach_to_subcgroup(context, cgroup_context, params, /* prefix= */ NULL);
if (r < 0) {
*exit_status = EXIT_CGROUP;
return r;
}
}
/* Now that the mount namespace has been set up and privileges adjusted, let's look for the thing we
* shall execute. */
const char *path = command->path;
if (FLAGS_SET(command->flags, EXEC_COMMAND_VIA_SHELL)) {
if (shell_is_placeholder(shell)) {
log_debug("Shell prefixing requested for user without default shell, using /bin/sh: %s",
strna(username));
assert(streq(path, _PATH_BSHELL));
} else
path = shell;
}
_cleanup_free_ char *executable = NULL;
_cleanup_close_ int executable_fd = -EBADF;
r = find_executable_full(path, /* root= */ NULL, context->exec_search_path, false, &executable, &executable_fd);
if (r < 0) {
*exit_status = EXIT_EXEC;
log_struct_errno(LOG_NOTICE, r,
LOG_MESSAGE_ID(SD_MESSAGE_SPAWN_FAILED_STR),
LOG_EXEC_MESSAGE(params, "Unable to locate executable '%s': %m", path),
LOG_ITEM("EXECUTABLE=%s", path));
/* If the error will be ignored by manager, tune down the log level here. Missing executable
* is very much expected in this case. */
return r != -ENOMEM && FLAGS_SET(command->flags, EXEC_COMMAND_IGNORE_FAILURE) ? 1 : r;
}
r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &executable_fd);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to collect shifted fd: %m");
}
#if HAVE_SELINUX
if (needs_sandboxing && use_selinux && params->selinux_context_net) {
int fd = -EBADF;
if (socket_fd >= 0)
fd = socket_fd;
else if (params->n_socket_fds == 1)
/* If stdin is not connected to a socket but we are triggered by exactly one socket unit then we
* use context from that fd to compute the label. */
fd = params->fds[0];
if (fd >= 0) {
r = mac_selinux_get_child_mls_label(fd, executable, context->selinux_context, &mac_selinux_context_net);
if (r < 0) {
if (!context->selinux_context_ignore) {
*exit_status = EXIT_SELINUX_CONTEXT;
return log_error_errno(r, "Failed to determine SELinux context: %m");
}
log_debug_errno(r, "Failed to determine SELinux context, ignoring: %m");
}
}
}
#endif
/* We repeat the fd closing here, to make sure that nothing is leaked from the PAM modules. Note that
* we are more aggressive this time, since we don't need socket_fd and the netns and ipcns fds any
* more. We do keep exec_fd and handoff_timestamp_fd however, if we have it, since we need to keep
* them open until the final execve(). But first, close the remaining sockets in the context
* objects. */
exec_runtime_close(runtime);
exec_params_close(params);
r = close_all_fds(keep_fds, n_keep_fds);
if (r >= 0)
r = pack_fds(params->fds, n_fds);
if (r >= 0)
r = flag_fds(params->fds, n_socket_fds, n_fds, context->non_blocking);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_error_errno(r, "Failed to adjust passed file descriptors: %m");
}
/* At this point, the fds we want to pass to the program are all ready and set up, with O_CLOEXEC turned off
* and at the right fd numbers. The are no other fds open, with one exception: the exec_fd if it is defined,
* and it has O_CLOEXEC set, after all we want it to be closed by the execve(), so that our parent knows we
* came this far. */
secure_bits = context->secure_bits;
if (needs_sandboxing) {
uint64_t bset;
/* Set the RTPRIO resource limit to 0, but only if nothing else was explicitly requested.
* (Note this is placed after the general resource limit initialization, see above, in order
* to take precedence.) */
if (context->restrict_realtime && !context->rlimit[RLIMIT_RTPRIO]) {
if (setrlimit(RLIMIT_RTPRIO, &RLIMIT_MAKE_CONST(0)) < 0) {
*exit_status = EXIT_LIMITS;
return log_error_errno(errno, "Failed to adjust RLIMIT_RTPRIO resource limit: %m");
}
}
#if ENABLE_SMACK
/* LSM Smack needs the capability CAP_MAC_ADMIN to change the current execution security context of the
* process. This is the latest place before dropping capabilities. Other MAC context are set later. */
if (use_smack) {
r = setup_smack(context, params, executable_fd);
if (r < 0 && !context->smack_process_label_ignore) {
*exit_status = EXIT_SMACK_PROCESS_LABEL;
return log_error_errno(r, "Failed to set SMACK process label: %m");
}
}
#endif
bset = context->capability_bounding_set;
#if HAVE_SECCOMP
/* If the service has any form of a seccomp filter and it allows dropping privileges, we'll
* keep the needed privileges to apply it even if we're not root. */
if (needs_setuid &&
uid_is_valid(uid) &&
context_has_seccomp(context) &&
seccomp_allows_drop_privileges(context)) {
keep_seccomp_privileges = true;
if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
*exit_status = EXIT_USER;
return log_error_errno(errno, "Failed to enable keep capabilities flag: %m");
}
/* Save the current bounding set so we can restore it after applying the seccomp
* filter */
saved_bset = bset;
bset |= (UINT64_C(1) << CAP_SYS_ADMIN) |
(UINT64_C(1) << CAP_SETPCAP);
}
#endif
if (!cap_test_all(bset)) {
r = capability_bounding_set_drop(bset, /* right_now= */ false);
if (r < 0) {
*exit_status = EXIT_CAPABILITIES;
return log_error_errno(r, "Failed to drop capabilities: %m");
}
}
/* Ambient capabilities are cleared during setresuid() (in enforce_user()) even with
* keep-caps set.
*
* To be able to raise the ambient capabilities after setresuid() they have to be added to
* the inherited set and keep caps has to be set (done in enforce_user()). After setresuid()
* the ambient capabilities can be raised as they are present in the permitted and
* inhertiable set. However it is possible that someone wants to set ambient capabilities
* without changing the user, so we also set the ambient capabilities here.
*
* The requested ambient capabilities are raised in the inheritable set if the second
* argument is true. */
if (capability_ambient_set != 0) {
r = capability_ambient_set_apply(capability_ambient_set, /* also_inherit= */ true);
if (r < 0) {
*exit_status = EXIT_CAPABILITIES;
return log_error_errno(r, "Failed to apply ambient capabilities (before UID change): %m");
}
}
}
/* chroot to root directory first, before we lose the ability to chroot */
r = apply_root_directory(context, params, runtime, needs_mount_namespace, exit_status);
if (r < 0)
return log_error_errno(r, "Chrooting to the requested root directory failed: %m");
if (needs_setuid) {
if (uid_is_valid(uid)) {
r = enforce_user(context, uid, capability_ambient_set);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to change UID to " UID_FMT ": %m", uid);
}
if (keep_seccomp_privileges) {
if (!BIT_SET(capability_ambient_set, CAP_SETUID)) {
r = drop_capability(CAP_SETUID);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to drop CAP_SETUID: %m");
}
}
r = keep_capability(CAP_SYS_ADMIN);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to keep CAP_SYS_ADMIN: %m");
}
r = keep_capability(CAP_SETPCAP);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to keep CAP_SETPCAP: %m");
}
}
if (capability_ambient_set != 0) {
/* Raise the ambient capabilities after user change. */
r = capability_ambient_set_apply(capability_ambient_set, /* also_inherit= */ false);
if (r < 0) {
*exit_status = EXIT_CAPABILITIES;
return log_error_errno(r, "Failed to apply ambient capabilities (after UID change): %m");
}
}
}
}
/* Apply working directory here, because the working directory might be on NFS and only the user
* running this service might have the correct privilege to change to the working directory. Also, it
* is absolutely 💣 crucial 💣 we applied all mount namespacing rearrangements before this, so that
* the cwd cannot be used to pin directories outside of the sandbox. */
r = apply_working_directory(context, params, runtime, pwent_home, accum_env);
if (r < 0) {
*exit_status = EXIT_CHDIR;
return log_error_errno(r, "Changing to the requested working directory failed: %m");
}
if (needs_sandboxing) {
/* Apply other MAC contexts late, but before seccomp syscall filtering, as those should really be last to
* influence our own codepaths as little as possible. Moreover, applying MAC contexts usually requires
* syscalls that are subject to seccomp filtering, hence should probably be applied before the syscalls
* are restricted. */
#if HAVE_SELINUX
if (use_selinux) {
char *exec_context = mac_selinux_context_net ?: context->selinux_context;
if (exec_context) {
r = setexeccon(exec_context);
if (r < 0) {
if (!context->selinux_context_ignore) {
*exit_status = EXIT_SELINUX_CONTEXT;
return log_error_errno(r, "Failed to change SELinux context to %s: %m", exec_context);
}
log_debug_errno(r, "Failed to change SELinux context to %s, ignoring: %m", exec_context);
}
}
}
#endif
#if HAVE_APPARMOR
if (use_apparmor && context->apparmor_profile) {
r = ASSERT_PTR(sym_aa_change_onexec)(context->apparmor_profile);
if (r < 0 && !context->apparmor_profile_ignore) {
*exit_status = EXIT_APPARMOR_PROFILE;
return log_error_errno(errno, "Failed to prepare AppArmor profile change to %s: %m",
context->apparmor_profile);
}
}
#endif
/* PR_GET_SECUREBITS is not privileged, while PR_SET_SECUREBITS is. So to suppress potential
* EPERMs we'll try not to call PR_SET_SECUREBITS unless necessary. Setting securebits
* requires CAP_SETPCAP. */
if (prctl(PR_GET_SECUREBITS) != secure_bits) {
/* CAP_SETPCAP is required to set securebits. This capability is raised into the
* effective set here.
*
* The effective set is overwritten during execve() with the following values:
*
* - ambient set (for non-root processes)
*
* - (inheritable | bounding) set for root processes)
*
* Hence there is no security impact to raise it in the effective set before execve
*/
r = capability_gain_cap_setpcap(/* ret_before_caps = */ NULL);
if (r < 0) {
*exit_status = EXIT_CAPABILITIES;
return log_error_errno(r, "Failed to gain CAP_SETPCAP for setting secure bits");
}
if (prctl(PR_SET_SECUREBITS, secure_bits) < 0) {
*exit_status = EXIT_SECUREBITS;
return log_error_errno(errno, "Failed to set process secure bits: %m");
}
}
if (context_has_no_new_privileges(context))
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
*exit_status = EXIT_NO_NEW_PRIVILEGES;
return log_error_errno(errno, "Failed to disable new privileges: %m");
}
#if HAVE_SECCOMP
r = apply_address_families(context, params);
if (r < 0) {
*exit_status = EXIT_ADDRESS_FAMILIES;
return log_error_errno(r, "Failed to restrict address families: %m");
}
r = apply_memory_deny_write_execute(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to disable writing to executable memory: %m");
}
r = apply_restrict_realtime(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply realtime restrictions: %m");
}
r = apply_restrict_suid_sgid(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply SUID/SGID restrictions: %m");
}
r = apply_restrict_namespaces(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply namespace restrictions: %m");
}
r = apply_protect_sysctl(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply sysctl restrictions: %m");
}
r = apply_protect_kernel_modules(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply module loading restrictions: %m");
}
r = apply_protect_kernel_logs(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply kernel log restrictions: %m");
}
r = apply_protect_clock(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply clock restrictions: %m");
}
r = apply_private_devices(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to set up private devices: %m");
}
r = apply_syscall_archs(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply syscall architecture restrictions: %m");
}
r = apply_lock_personality(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to lock personalities: %m");
}
r = apply_syscall_log(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply system call log filters: %m");
}
#endif
#if HAVE_LIBBPF
r = apply_restrict_filesystems(context, params);
if (r < 0) {
*exit_status = EXIT_BPF;
return log_error_errno(r, "Failed to restrict filesystems: %m");
}
#endif
#if HAVE_SECCOMP
/* This really should remain as close to the execve() as possible, to make sure our own code is affected
* by the filter as little as possible. */
r = apply_syscall_filter(context, params);
if (r < 0) {
*exit_status = EXIT_SECCOMP;
return log_error_errno(r, "Failed to apply system call filters: %m");
}
if (keep_seccomp_privileges) {
/* Restore the capability bounding set with what's expected from the service + the
* ambient capabilities hack */
if (!cap_test_all(saved_bset)) {
r = capability_bounding_set_drop(saved_bset, /* right_now= */ false);
if (r < 0) {
*exit_status = EXIT_CAPABILITIES;
return log_error_errno(r, "Failed to drop bset capabilities: %m");
}
}
/* Only drop CAP_SYS_ADMIN if it's not in the bounding set, otherwise we'll break
* applications that use it. */
if (!BIT_SET(saved_bset, CAP_SYS_ADMIN)) {
r = drop_capability(CAP_SYS_ADMIN);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to drop CAP_SYS_ADMIN: %m");
}
}
/* Only drop CAP_SETPCAP if it's not in the bounding set, otherwise we'll break
* applications that use it. */
if (!BIT_SET(saved_bset, CAP_SETPCAP)) {
r = drop_capability(CAP_SETPCAP);
if (r < 0) {
*exit_status = EXIT_USER;
return log_error_errno(r, "Failed to drop CAP_SETPCAP: %m");
}
}
if (prctl(PR_SET_KEEPCAPS, 0) < 0) {
*exit_status = EXIT_USER;
return log_error_errno(errno, "Failed to drop keep capabilities flag: %m");
}
}
#endif
}
if (!strv_isempty(context->unset_environment)) {
char **ee = NULL;
ee = strv_env_delete(accum_env, 1, context->unset_environment);
if (!ee) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
strv_free_and_replace(accum_env, ee);
}
_cleanup_strv_free_ char **replaced_argv = NULL, **argv_via_shell = NULL;
char **final_argv = FLAGS_SET(command->flags, EXEC_COMMAND_VIA_SHELL) ? strv_skip(command->argv, 1) : command->argv;
if (final_argv && !FLAGS_SET(command->flags, EXEC_COMMAND_NO_ENV_EXPAND)) {
_cleanup_strv_free_ char **unset_variables = NULL, **bad_variables = NULL;
r = replace_env_argv(final_argv, accum_env, &replaced_argv, &unset_variables, &bad_variables);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_error_errno(r, "Failed to replace environment variables: %m");
}
final_argv = replaced_argv;
if (!strv_isempty(unset_variables)) {
_cleanup_free_ char *ju = strv_join(unset_variables, ", ");
log_warning("Referenced but unset environment variable evaluates to an empty string: %s", strna(ju));
}
if (!strv_isempty(bad_variables)) {
_cleanup_free_ char *jb = strv_join(bad_variables, ", ");
log_warning("Invalid environment variable name evaluates to an empty string: %s", strna(jb));
}
}
if (FLAGS_SET(command->flags, EXEC_COMMAND_VIA_SHELL)) {
r = strv_extendf(&argv_via_shell, "%s%s", command->argv[0][0] == '-' ? "-" : "", path);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
if (!strv_isempty(final_argv)) {
_cleanup_free_ char *cmdline_joined = NULL;
cmdline_joined = strv_join(final_argv, " ");
if (!cmdline_joined) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
r = strv_extend_many(&argv_via_shell, "-c", cmdline_joined);
if (r < 0) {
*exit_status = EXIT_MEMORY;
return log_oom();
}
}
final_argv = argv_via_shell;
}
log_command_line(context, params, "Executing", executable, final_argv);
/* We have finished with all our initializations. Let's now let the manager know that. From this
* point on, if the manager sees POLLHUP on the exec_fd, then execve() was successful. */
r = exec_fd_mark_hot(context, params, /* hot= */ true, exit_status);
if (r < 0)
return r;
/* As last thing before the execve(), let's send the handoff timestamp */
r = send_handoff_timestamp(context, params, exit_status);
if (r < 0) {
/* If this handoff timestamp failed, let's undo the marking as hot */
(void) exec_fd_mark_hot(context, params, /* hot= */ false, /* reterr_exit_status= */ NULL);
return r;
}
/* NB: we leave executable_fd, exec_fd, handoff_timestamp_fd open here. This is safe, because they
* have O_CLOEXEC set, and the execve() below will thus automatically close them. In fact, for
* exec_fd this is pretty much the whole raison d'etre. */
r = fexecve_or_execve(executable_fd, executable, final_argv, accum_env);
/* The execve() failed, let's undo the marking as hot */
(void) exec_fd_mark_hot(context, params, /* hot= */ false, /* reterr_exit_status= */ NULL);
*exit_status = EXIT_EXEC;
return log_error_errno(r, "Failed to execute %s: %m", executable);
}
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