From 2b4894764e9e92ae9004524ed466b4bdf94b2a34 Mon Sep 17 00:00:00 2001

From: Alban Crequy <alban@endocode.com>

Date: Mon, 18 May 2015 12:20:28 +0200

Subject: [PATCH] core: Private*/Protect* options with RootDirectory

When a service is chrooted with the option RootDirectory=/opt/..., then

the options PrivateDevices, PrivateTmp, ProtectHome, ProtectSystem must

mount the directories under $RootDirectory/{dev,tmp,home,usr,boot}.

The test-ns tool can test setup_namespace() with and without chroot:

 $ sudo TEST_NS_PROJECTS=/home/lennart/projects ./test-ns

 $ sudo TEST_NS_CHROOT=/home/alban/debian-tree TEST_NS_PROJECTS=/home/alban/debian-tree/home/alban/Documents ./test-ns

Cherry-picked from: ee818b89f4890b3a00e93772249fce810f60811e

Resolves: #1421181

---

 src/core/execute.c   |  8 ++++--

 src/core/namespace.c | 80 +++++++++++++++++++++++++++++++++++++++++++++-------

 src/core/namespace.h |  3 +-

 src/test/test-ns.c   | 24 ++++++++++++++--

 4 files changed, 100 insertions(+), 15 deletions(-)

diff --git a/src/core/execute.c b/src/core/execute.c

index 59340ec..863babd 100644

--- a/src/core/execute.c

+++ b/src/core/execute.c

@@ -1305,6 +1305,7 @@ static int exec_child(

         uid_t uid = UID_INVALID;

         gid_t gid = GID_INVALID;

         int i, r;

+        bool needs_mount_namespace;

         assert(command);

         assert(context);

@@ -1593,7 +1594,9 @@ static int exec_child(

                 }

         }

-        if (exec_needs_mount_namespace(context, params, runtime)) {

+        needs_mount_namespace = exec_needs_mount_namespace(context, params, runtime);

+

+        if (needs_mount_namespace) {

                 char *tmp = NULL, *var = NULL;

                 /* The runtime struct only contains the parent

@@ -1610,6 +1613,7 @@ static int exec_child(

                 }

                 r = setup_namespace(

+                                params->apply_chroot ? context->root_directory : NULL,

                                 context->read_write_dirs,

                                 context->read_only_dirs,

                                 context->inaccessible_dirs,

@@ -1635,7 +1639,7 @@ static int exec_child(

         }

         if (params->apply_chroot) {

-                if (context->root_directory)

+                if (!needs_mount_namespace && context->root_directory)

                         if (chroot(context->root_directory) < 0) {

                                 *exit_status = EXIT_CHROOT;

                                 return -errno;

diff --git a/src/core/namespace.c b/src/core/namespace.c

index 00495c1..5747462 100644

--- a/src/core/namespace.c

+++ b/src/core/namespace.c

@@ -44,6 +44,7 @@

 #include "label.h"

 #include "selinux-util.h"

 #include "namespace.h"

+#include "mkdir.h"

 typedef enum MountMode {

         /* This is ordered by priority! */

@@ -132,6 +133,22 @@ static void drop_duplicates(BindMount *m, unsigned *n) {

         *n = t - m;

 }

+static int mount_move_root(const char *path) {

+        if (chdir(path) < 0)

+                return -errno;

+

+        if (mount(path, "/", NULL, MS_MOVE, NULL) < 0)

+                return -errno;

+

+        if (chroot(".") < 0)

+                return -errno;

+

+        if (chdir("/") < 0)

+                return -errno;

+

+        return 0;

+}

+

 static int mount_dev(BindMount *m) {

         static const char devnodes[] =

                 "/dev/null\0"

@@ -231,7 +248,13 @@ static int mount_dev(BindMount *m) {

         dev_setup(temporary_mount);

-        if (mount(dev, "/dev/", NULL, MS_MOVE, NULL) < 0) {

+        /* Create the /dev directory if missing. It is more likely to be

+         * missing when the service is started with RootDirectory. This is

+         * consistent with mount units creating the mount points when missing.

+         */

+        (void) mkdir_p_label(m->path, 0755);

+

+        if (mount(dev, m->path, NULL, MS_MOVE, NULL) < 0) {

                 r = -errno;

                 goto fail;

         }

@@ -410,6 +433,7 @@ static int make_read_only(BindMount *m) {

 }

 int setup_namespace(

+                const char* root_directory,

                 char** read_write_dirs,

                 char** read_only_dirs,

                 char** inaccessible_dirs,

@@ -455,37 +479,56 @@ int setup_namespace(

                         return r;

                 if (tmp_dir) {

-                        m->path = "/tmp";

+                        m->path = prefix_roota(root_directory, "/tmp");

                         m->mode = PRIVATE_TMP;

                         m++;

                 }

                 if (var_tmp_dir) {

-                        m->path = "/var/tmp";

+                        m->path = prefix_roota(root_directory, "/var/tmp");

                         m->mode = PRIVATE_VAR_TMP;

                         m++;

                 }

                 if (private_dev) {

-                        m->path = "/dev";

+                        m->path = prefix_roota(root_directory, "/dev");

                         m->mode = PRIVATE_DEV;

                         m++;

                 }

                 if (bus_endpoint_path) {

-                        m->path = bus_endpoint_path;

+                        m->path = prefix_roota(root_directory, bus_endpoint_path);

                         m->mode = PRIVATE_BUS_ENDPOINT;

                         m++;

                 }

                 if (protect_home != PROTECT_HOME_NO) {

-                        r = append_mounts(&m, STRV_MAKE("-/home", "-/run/user", "-/root"), protect_home == PROTECT_HOME_READ_ONLY ? READONLY : INACCESSIBLE);

+                        const char *home_dir, *run_user_dir, *root_dir;

+

+                        home_dir = prefix_roota(root_directory, "/home");

+                        home_dir = strjoina("-", home_dir);

+                        run_user_dir = prefix_roota(root_directory, "/run/user");

+                        run_user_dir = strjoina("-", run_user_dir);

+                        root_dir = prefix_roota(root_directory, "/root");

+                        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);

                         if (r < 0)

                                 return r;

                 }

                 if (protect_system != PROTECT_SYSTEM_NO) {

-                        r = append_mounts(&m, protect_system == PROTECT_SYSTEM_FULL ? STRV_MAKE("/usr", "-/boot", "/etc") : STRV_MAKE("/usr", "-/boot"), READONLY);

+                        const char *usr_dir, *boot_dir, *etc_dir;

+

+                        usr_dir = prefix_roota(root_directory, "/home");

+                        boot_dir = prefix_roota(root_directory, "/boot");

+                        boot_dir = strjoina("-", boot_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);

                         if (r < 0)

                                 return r;

                 }

@@ -496,12 +539,20 @@ int setup_namespace(

                 drop_duplicates(mounts, &n);

         }

-        if (n > 0) {

+        if (n > 0 || root_directory) {

                 /* Remount / as SLAVE so that nothing now mounted in the namespace

                    shows up in the parent */

                 if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)

                         return -errno;

+        }

+

+        if (root_directory) {

+                /* Turn directory into bind mount */

+                if (mount(root_directory, root_directory, NULL, MS_BIND|MS_REC, NULL) < 0)

+                        return -errno;

+        }

+        if (n > 0) {

                 for (m = mounts; m < mounts + n; ++m) {

                         r = apply_mount(m, tmp_dir, var_tmp_dir);

                         if (r < 0)

@@ -515,12 +566,21 @@ int setup_namespace(

                 }

         }

+        if (root_directory) {

+                /* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */

+                r = mount_move_root(root_directory);

+

+                /* at this point, we cannot rollback */

+                if (r < 0)

+                        return r;

+        }

+

         /* Remount / as the desired mode. Not that this will not

          * reestablish propagation from our side to the host, since

          * what's disconnected is disconnected. */

         if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) {

-                r = -errno;

-                goto fail;

+                /* at this point, we cannot rollback */

+                return -errno;

         }

         return 0;

diff --git a/src/core/namespace.h b/src/core/namespace.h

index 42b92e7..00ab22b 100644

--- a/src/core/namespace.h

+++ b/src/core/namespace.h

@@ -41,7 +41,8 @@ typedef enum ProtectSystem {

         _PROTECT_SYSTEM_INVALID = -1

 } ProtectSystem;

-int setup_namespace(char **read_write_dirs,

+int setup_namespace(const char *chroot,

+                    char **read_write_dirs,

                     char **read_only_dirs,

                     char **inaccessible_dirs,

                     const char *tmp_dir,

diff --git a/src/test/test-ns.c b/src/test/test-ns.c

index 7cd7b77..72a0004 100644

--- a/src/test/test-ns.c

+++ b/src/test/test-ns.c

@@ -42,10 +42,12 @@ int main(int argc, char *argv[]) {

                 NULL

         };

-        const char * const inaccessible[] = {

+        const char *inaccessible[] = {

                 "/home/lennart/projects",

                 NULL

         };

+        char *root_directory;

+        char *projects_directory;

         int r;

         char tmp_dir[] = "/tmp/systemd-private-XXXXXX",

@@ -54,7 +56,20 @@ int main(int argc, char *argv[]) {

         assert_se(mkdtemp(tmp_dir));

         assert_se(mkdtemp(var_tmp_dir));

-        r = setup_namespace((char **) writable,

+        root_directory = getenv("TEST_NS_CHROOT");

+        projects_directory = getenv("TEST_NS_PROJECTS");

+

+        if (projects_directory)

+                inaccessible[0] = projects_directory;

+

+        log_info("Inaccessible directory: '%s'", inaccessible[0]);

+        if (root_directory)

+                log_info("Chroot: '%s'", root_directory);

+        else

+                log_info("Not chrooted");

+

+        r = setup_namespace(root_directory,

+                            (char **) writable,

                             (char **) readonly,

                             (char **) inaccessible,

                             tmp_dir,

@@ -66,6 +81,11 @@ int main(int argc, char *argv[]) {

                             0);

         if (r < 0) {

                 log_error_errno(r, "Failed to setup namespace: %m");

+

+                log_info("Usage:\n"

+                         "  sudo TEST_NS_PROJECTS=/home/lennart/projects ./test-ns\n"

+                         "  sudo TEST_NS_CHROOT=/home/alban/debian-tree TEST_NS_PROJECTS=/home/alban/debian-tree/home/alban/Documents ./test-ns");

+

                 return 1;

         }