Add SELinux support to systemd-nspawn

This patch adds to new options:

-Z PROCESS_LABEL

This specifies the process label to run on processes run within the container.

-L FILE_LABEL

The file label to assign to memory file systems created within the container.

For example if you wanted to wrap an container with SELinux sandbox labels, you could execute a command line the following

chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh

man/systemd-nspawn.xml

@@ -248,6 +248,27 @@
                                 </listitem>
                         </varlistentry>
 
+                        <varlistentry>
+                                <term><option>-L</option></term>
+                                <term><option>--file-label=</option></term>
+
+                                <listitem><para>Sets the mandatory
+                                access control (MAC) file label to be
+                                used by tmpfs file systems in the
+                                container.</para>
+                                </listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><option>-Z</option></term>
+                                <term><option>--process-label=</option></term>
+
+                                <listitem><para>Sets the mandatory
+                                access control (MAC) label to be used by
+                                processes in the container.</para>
+                                </listitem>
+                        </varlistentry>
+
                         <varlistentry>
                                 <term><option>--uuid=</option></term>
 
@@ -456,6 +477,14 @@
                 btrfs snapshot.</para>
         </refsect1>
 
+        <refsect1>
+                <title>Example 6</title>
+
+                <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
+# systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh</programlisting>
+
+                <para>This runs a container with SELinux sandbox labels.</para>
+        </refsect1>
 
         <refsect1>
                 <title>Exit status</title>

src/nspawn/nspawn.c

@@ -41,6 +41,9 @@
 #include <sys/socket.h>
 #include <linux/netlink.h>
 #include <sys/eventfd.h>
+#if HAVE_SELINUX
+#include <selinux/selinux.h>
+#endif
 
 #include "sd-daemon.h"
 #include "sd-bus.h"
@@ -77,6 +80,8 @@ static char *arg_directory = NULL;
 static char *arg_user = NULL;
 static sd_id128_t arg_uuid = {};
 static char *arg_machine = NULL;
+static char *process_label = NULL;
+static char *file_label = NULL;
 static const char *arg_slice = NULL;
 static bool arg_private_network = false;
 static bool arg_read_only = false;
@@ -125,6 +130,8 @@ static int help(void) {
                "     --uuid=UUID            Set a specific machine UUID for the container\n"
                "  -M --machine=NAME         Set the machine name for the container\n"
                "  -S --slice=SLICE          Place the container in the specified slice\n"
+               "  -L --file-label=LABEL     Set the MAC file label to be used by tmpfs file systems in container\n"
+               "  -Z --process-label=LABEL  Set the MAC label to be used by processes in container\n"
                "     --private-network      Disable network in container\n"
                "     --read-only            Mount the root directory read-only\n"
                "     --capability=CAP       In addition to the default, retain specified\n"
@@ -173,6 +180,8 @@ static int parse_argv(int argc, char *argv[]) {
                 { "machine",         required_argument, NULL, 'M'                 },
                 { "slice",           required_argument, NULL, 'S'                 },
                 { "setenv",          required_argument, NULL, ARG_SETENV          },
+                { "process-label",   required_argument, NULL, 'Z'                 },
+                { "file-label",      required_argument, NULL, 'L'                 },
                 {}
         };
 
@@ -181,7 +190,7 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "+hD:u:bM:jS:", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "+hD:u:bL:M:jS:Z:", options, NULL)) >= 0) {
 
                 switch (c) {
 
@@ -247,6 +256,20 @@ static int parse_argv(int argc, char *argv[]) {
 
                         break;
 
+                case 'L':
+                        file_label = strdup(optarg);
+                        if (!file_label)
+                                return log_oom();
+
+                        break;
+
+                case 'Z':
+                        process_label = strdup(optarg);
+                        if (!process_label)
+                                return log_oom();
+
+                        break;
+
                 case ARG_READ_ONLY:
                         arg_read_only = true;
                         break;
@@ -396,6 +419,7 @@ static int mount_all(const char *dest) {
 
         for (k = 0; k < ELEMENTSOF(mount_table); k++) {
                 _cleanup_free_ char *where = NULL;
+                _cleanup_free_ char *options = NULL;
                 int t;
 
                 where = strjoin(dest, "/", mount_table[k].where, NULL);
@@ -418,11 +442,22 @@ static int mount_all(const char *dest) {
 
                 mkdir_p(where, 0755);
 
+#ifdef HAVE_SELINUX
+                if (file_label && (streq_ptr(mount_table[k].what, "tmpfs") ||
+                              streq_ptr(mount_table[k].what, "devpts")))
+                        options = strjoin(mount_table[k].options, ",context=\"", file_label, "\"", NULL);
+                else
+#endif
+                        options = strjoin(mount_table[k].options, NULL);
+
+                if (!options)
+                        return log_oom();
+
                 if (mount(mount_table[k].what,
                           where,
                           mount_table[k].type,
                           mount_table[k].flags,
-                          mount_table[k].options) < 0 &&
+                          options) < 0 &&
                     mount_table[k].fatal) {
 
                         log_error("mount(%s) failed: %m", where);
@@ -1491,6 +1526,11 @@ int main(int argc, char *argv[]) {
                         } else
                                 env_use = (char**) envp;
 
+#if HAVE_SELINUX
+                        if (process_label)
+                                if (setexeccon(process_label) < 0)
+                                        log_error("setexeccon(\"%s\") failed: %m", process_label);
+#endif
                         if (arg_boot) {
                                 char **a;
                                 size_t l;