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core: add new option 'tmpfs' to ProtectHome= 

This make ProtectHome= setting can take 'tmpfs'. This is mostly
equivalent to `TemporaryFileSystem=/home /run/user /root`.
This commit is contained in:
Yu Watanabe 2018-02-21 09:13:11 +09:00
parent 4cac89bd7c
commit e4da7d8c79
3 changed files with 33 additions and 9 deletions
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26
man/systemd.exec.xml
View File

@ -788,14 +788,24 @@ CapabilityBoundingSet=~CAP_B CAP_C</programlisting>
<varlistentry>
<term><varname>ProtectHome=</varname></term>
<listitem><para>Takes a boolean argument or <literal>read-only</literal>. If true, the directories
<filename>/home</filename>, <filename>/root</filename> and <filename>/run/user</filename> are made inaccessible
and empty for processes invoked by this unit. If set to <literal>read-only</literal>, the three directories are
made read-only instead. It is recommended to enable this setting for all long-running services (in particular
network-facing ones), to ensure they cannot get access to private user data, unless the services actually
require access to the user's private data. This setting is implied if <varname>DynamicUser=</varname> is
set. For this setting the same restrictions regarding mount propagation and privileges apply as for
<varname>ReadOnlyPaths=</varname> and related calls, see below.</para></listitem>
<listitem><para>Takes a boolean argument or the special values <literal>read-only</literal> or
<literal>tmpfs</literal>. If true, the directories <filename>/home</filename>, <filename>/root</filename> and
<filename>/run/user</filename> are made inaccessible and empty for processes invoked by this unit. If set to
<literal>read-only</literal>, the three directories are made read-only instead. If set to <literal>tmpfs</literal>,
temporary file systems are mounted on the three directories in read-only mode. The value <literal>tmpfs</literal>
is useful to hide home directories not relevant to the processes invoked by the unit, while necessary directories
are still visible by combining with <varname>BindPaths=</varname> or <varname>BindReadOnlyPaths=</varname>.</para>
<para>Setting this to <literal>yes</literal> is mostly equivalent to set the three directories in
<varname>InaccessiblePaths=</varname>. Similary, <literal>read-only</literal> is mostly equivalent to
<varname>ReadOnlyPaths=</varname>, and <literal>tmpfs</literal> is mostly equivalent to
<varname>TemporaryFileSystem=</varname>.</para>
<para> It is recommended to enable this setting for all long-running services (in particular network-facing ones),
to ensure they cannot get access to private user data, unless the services actually require access to the user's
private data. This setting is implied if <varname>DynamicUser=</varname> is set. For this setting the same
restrictions regarding mount propagation and privileges apply as for <varname>ReadOnlyPaths=</varname> and related
calls, see below.</para></listitem>
</varlistentry>
<varlistentry>

15
src/core/namespace.c
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@ -128,6 +128,13 @@ static const MountEntry protect_home_read_only_table[] = {
{ "/root", READONLY, true },
};
/* ProtectHome=tmpfs table */
static const MountEntry protect_home_tmpfs_table[] = {
{ "/home", TMPFS, true, .read_only = true, .options_const = "mode=0755", .flags = MS_NODEV|MS_STRICTATIME },
{ "/run/user", TMPFS, true, .read_only = true, .options_const = "mode=0755", .flags = MS_NODEV|MS_STRICTATIME },
{ "/root", TMPFS, true, .read_only = true, .options_const = "mode=0700", .flags = MS_NODEV|MS_STRICTATIME },
};
/* ProtectHome=yes table */
static const MountEntry protect_home_yes_table[] = {
{ "/home", INACCESSIBLE, true },
@ -354,6 +361,9 @@ static int append_protect_home(MountEntry **p, ProtectHome protect_home, bool ig
case PROTECT_HOME_READ_ONLY:
return append_static_mounts(p, protect_home_read_only_table, ELEMENTSOF(protect_home_read_only_table), ignore_protect);
case PROTECT_HOME_TMPFS:
return append_static_mounts(p, protect_home_tmpfs_table, ELEMENTSOF(protect_home_tmpfs_table), ignore_protect);
case PROTECT_HOME_YES:
return append_static_mounts(p, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect);
@ -1011,7 +1021,9 @@ static unsigned namespace_calculate_mounts(
(protect_home == PROTECT_HOME_YES ?
ELEMENTSOF(protect_home_yes_table) :
((protect_home == PROTECT_HOME_READ_ONLY) ?
ELEMENTSOF(protect_home_read_only_table) : 0));
ELEMENTSOF(protect_home_read_only_table) :
((protect_home == PROTECT_HOME_TMPFS) ?
ELEMENTSOF(protect_home_tmpfs_table) : 0)));
return !!tmp_dir + !!var_tmp_dir +
strv_length(read_write_paths) +
@ -1576,6 +1588,7 @@ static const char *const protect_home_table[_PROTECT_HOME_MAX] = {
[PROTECT_HOME_NO] = "no",
[PROTECT_HOME_YES] = "yes",
[PROTECT_HOME_READ_ONLY] = "read-only",
[PROTECT_HOME_TMPFS] = "tmpfs",
};
DEFINE_STRING_TABLE_LOOKUP(protect_home, ProtectHome);

1
src/core/namespace.h
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@ -34,6 +34,7 @@ typedef enum ProtectHome {
PROTECT_HOME_NO,
PROTECT_HOME_YES,
PROTECT_HOME_READ_ONLY,
PROTECT_HOME_TMPFS,
_PROTECT_HOME_MAX,
_PROTECT_HOME_INVALID = -1
} ProtectHome;