<varlistentry>
<term><varname>ProtectSystem=</varname></term>
- <listitem><para>Takes a boolean argument or
- <literal>full</literal>. If true, mounts the
- <filename>/usr</filename> and <filename>/boot</filename>
- directories read-only for processes invoked by this unit. If
- set to <literal>full</literal>, the <filename>/etc</filename>
- directory is mounted read-only, too. This setting ensures that
- any modification of the vendor-supplied operating system (and
- optionally its configuration) is prohibited for the service.
- It is recommended to enable this setting for all long-running
- services, unless they are involved with system updates or need
- to modify the operating system in other ways. Note however
- that processes retaining the CAP_SYS_ADMIN capability can undo
- the effect of this setting. This setting is hence particularly
- useful for daemons which have this capability removed, for
- example with <varname>CapabilityBoundingSet=</varname>.
- Defaults to off.</para></listitem>
+ <listitem><para>Takes a boolean argument or the special values <literal>full</literal> or
+ <literal>strict</literal>. If true, mounts the <filename>/usr</filename> and <filename>/boot</filename>
+ directories read-only for processes invoked by this unit. If set to <literal>full</literal>, the
+ <filename>/etc</filename> directory is mounted read-only, too. If set to <literal>strict</literal> the entire
+ file system hierarchy is mounted read-only, except for the API file system subtrees <filename>/dev</filename>,
+ <filename>/proc</filename> and <filename>/sys</filename> (protect these directories using
+ <varname>PrivateDevices=</varname>, <varname>ProtectKernelTunables=</varname>,
+ <varname>ProtectControlGroups=</varname>). This setting ensures that any modification of the vendor-supplied
+ operating system (and optionally its configuration, and local mounts) is prohibited for the service. It is
+ recommended to enable this setting for all long-running services, unless they are involved with system updates
+ or need to modify the operating system in other ways. If this option is used,
+ <varname>ReadWritePaths=</varname> may be used to exclude specific directories from being made read-only. Note
+ that processes retaining the <constant>CAP_SYS_ADMIN</constant> capability (and with no system call filter that
+ prohibits mount-related system calls applied) can undo the effect of this setting. This setting is hence
+ particularly useful for daemons which have this either the <literal>@mount</literal> set filtered using
+ <varname>SystemCallFilter=</varname>, or have the <constant>CAP_SYS_ADMIN</constant> capability removed, for
+ example with <varname>CapabilityBoundingSet=</varname>. Defaults to off.</para></listitem>
</varlistentry>
<varlistentry>
private_dev +
(protect_sysctl ? 3 : 0) +
(protect_cgroups != protect_sysctl) +
- (protect_home != PROTECT_HOME_NO ? 3 : 0) +
- (protect_system != PROTECT_SYSTEM_NO ? 2 : 0) +
- (protect_system == PROTECT_SYSTEM_FULL ? 1 : 0);
+ (protect_home != PROTECT_HOME_NO || protect_system == PROTECT_SYSTEM_STRICT ? 3 : 0) +
+ (protect_system == PROTECT_SYSTEM_STRICT ?
+ (2 + !private_dev + !protect_sysctl) :
+ ((protect_system != PROTECT_SYSTEM_NO ? 3 : 0) +
+ (protect_system == PROTECT_SYSTEM_FULL ? 1 : 0)));
if (n > 0) {
m = mounts = (BindMount *) alloca0(n * sizeof(BindMount));
m++;
}
- if (protect_home != PROTECT_HOME_NO) {
+ if (protect_home != PROTECT_HOME_NO || protect_system == PROTECT_SYSTEM_STRICT) {
const char *home_dir, *run_user_dir, *root_dir;
+ /* If protection of $HOME and $XDG_RUNTIME_DIR is requested, then go for it. If we are in
+ * strict system protection mode, then also add entries for these directories, but mark them
+ * writable. This is because we want ProtectHome= and ProtectSystem= to be fully orthogonal. */
+
home_dir = prefix_roota(root_directory, "/home");
home_dir = strjoina("-", home_dir);
run_user_dir = prefix_roota(root_directory, "/run/user");
root_dir = strjoina("-", root_dir);
r = append_mounts(&m, STRV_MAKE(home_dir, run_user_dir, root_dir),
- protect_home == PROTECT_HOME_READ_ONLY ? READONLY : INACCESSIBLE);
+ protect_home == PROTECT_HOME_READ_ONLY ? READONLY :
+ protect_home == PROTECT_HOME_YES ? INACCESSIBLE : READWRITE);
if (r < 0)
return r;
}
- if (protect_system != PROTECT_SYSTEM_NO) {
- const char *usr_dir, *boot_dir, *etc_dir;
+ if (protect_system == PROTECT_SYSTEM_STRICT) {
+ /* In strict mode, we mount everything read-only, except for /proc, /dev, /sys which are the
+ * kernel API VFS, which are left writable, but PrivateDevices= + ProtectKernelTunables=
+ * protect those, and these options should be fully orthogonal. (And of course /home and
+ * friends are also left writable, as ProtectHome= shall manage those, orthogonally, see
+ * above). */
+
+ m->path = prefix_roota(root_directory, "/");
+ m->mode = READONLY;
+ m++;
+
+ m->path = prefix_roota(root_directory, "/proc");
+ m->mode = READWRITE;
+ m++;
+
+ if (!private_dev) {
+ m->path = prefix_roota(root_directory, "/dev");
+ m->mode = READWRITE;
+ m++;
+ }
+ if (!protect_sysctl) {
+ m->path = prefix_roota(root_directory, "/sys");
+ m->mode = READWRITE;
+ m++;
+ }
+
+ } else if (protect_system != PROTECT_SYSTEM_NO) {
+ const char *usr_dir, *boot_dir, *efi_dir, *etc_dir;
+
+ /* In any other mode we simply mark the relevant three directories ready-only. */
usr_dir = prefix_roota(root_directory, "/usr");
boot_dir = prefix_roota(root_directory, "/boot");
boot_dir = strjoina("-", boot_dir);
+ efi_dir = prefix_roota(root_directory, "/efi");
+ efi_dir = strjoina("-", efi_dir);
etc_dir = prefix_roota(root_directory, "/etc");
r = append_mounts(&m, protect_system == PROTECT_SYSTEM_FULL
- ? STRV_MAKE(usr_dir, boot_dir, etc_dir)
- : STRV_MAKE(usr_dir, boot_dir), READONLY);
+ ? STRV_MAKE(usr_dir, boot_dir, efi_dir, etc_dir)
+ : STRV_MAKE(usr_dir, boot_dir, efi_dir), READONLY);
if (r < 0)
return r;
}
[PROTECT_SYSTEM_NO] = "no",
[PROTECT_SYSTEM_YES] = "yes",
[PROTECT_SYSTEM_FULL] = "full",
+ [PROTECT_SYSTEM_STRICT] = "strict",
};
DEFINE_STRING_TABLE_LOOKUP(protect_system, ProtectSystem);