machined: move logic for bind mounting into containers from machinectl to machined

This extends the bus interface, adding BindMountMachine() for bind
mounting directories from the host into the container.

5 files changed, 263 insertions, 190 deletions

diff --git a/src/machine/machine-dbus.c b/src/machine/machine-dbus.c
index b46f0a8dac..246c2cfd05 100644
--- a/src/machine/machine-dbus.c
+++ b/src/machine/machine-dbus.c
@@ -22,6 +22,7 @@
 #include <errno.h>
 #include <string.h>
 #include <arpa/inet.h>
+#include <sys/mount.h>
 
 #include "bus-util.h"
 #include "bus-label.h"
@@ -32,6 +33,7 @@
 #include "in-addr-util.h"
 #include "local-addresses.h"
 #include "path-util.h"
+#include "mkdir.h"
 #include "bus-internal.h"
 #include "machine.h"
 #include "machine-dbus.h"
@@ -518,6 +520,211 @@ int bus_machine_method_open_login(sd_bus *bus, sd_bus_message *message, void *us
         return sd_bus_send(bus, reply, NULL);
 }
 
+int bus_machine_method_bind_mount(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_close_pair_ int errno_pipe_fd[2] = { -1, -1 };
+        char mount_slave[] = "/tmp/propagate.XXXXXX", *mount_tmp, *mount_outside, *p;
+        bool mount_slave_created = false, mount_slave_mounted = false,
+                mount_tmp_created = false, mount_tmp_mounted = false,
+                mount_outside_created = false, mount_outside_mounted = false;
+        const char *dest, *src;
+        Machine *m = userdata;
+        int read_only, make_directory;
+        pid_t child;
+        siginfo_t si;
+        int r;
+
+        if (m->class != MACHINE_CONTAINER)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_NOT_SUPPORTED, "Bind mounting is only supported on container machines.");
+
+        r = sd_bus_message_read(message, "ssbb", &src, &dest, &read_only, &make_directory);
+        if (r < 0)
+                return r;
+
+        if (!path_is_absolute(src) || !path_is_safe(src))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Source path must be absolute and not contain ../.");
+
+        if (isempty(dest))
+                dest = src;
+        else if (!path_is_absolute(dest) || !path_is_safe(dest))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Source path must be absolute and not contain ../.");
+
+        /* One day, when bind mounting /proc/self/fd/n works across
+         * namespace boundaries we should rework this logic to make
+         * use of it... */
+
+        p = strjoina("/run/systemd/nspawn/propagate/", m->name, "/");
+        if (laccess(p, F_OK) < 0)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_NOT_SUPPORTED, "Container does not allow propagation of mount points.");
+
+        /* Our goal is to install a new bind mount into the container,
+           possibly read-only. This is irritatingly complex
+           unfortunately, currently.
+
+           First, we start by creating a private playground in /tmp,
+           that we can mount MS_SLAVE. (Which is necessary, since
+           MS_MOUNT cannot be applied to mounts with MS_SHARED parent
+           mounts.) */
+
+        if (!mkdtemp(mount_slave))
+                return sd_bus_error_set_errnof(error, errno, "Failed to create playground %s: %m", mount_slave);
+
+        mount_slave_created = true;
+
+        if (mount(mount_slave, mount_slave, NULL, MS_BIND, NULL) < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to make bind mount %s: %m", mount_slave);
+                goto finish;
+        }
+
+        mount_slave_mounted = true;
+
+        if (mount(NULL, mount_slave, NULL, MS_SLAVE, NULL) < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to remount slave %s: %m", mount_slave);
+                goto finish;
+        }
+
+        /* Second, we mount the source directory to a directory inside
+           of our MS_SLAVE playground. */
+        mount_tmp = strjoina(mount_slave, "/mount");
+        if (mkdir(mount_tmp, 0700) < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to create temporary mount point %s: %m", mount_tmp);
+                goto finish;
+        }
+
+        mount_tmp_created = true;
+
+        if (mount(src, mount_tmp, NULL, MS_BIND, NULL) < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to overmount %s: %m", mount_tmp);
+                goto finish;
+        }
+
+        mount_tmp_mounted = true;
+
+        /* Third, we remount the new bind mount read-only if requested. */
+        if (read_only)
+                if (mount(NULL, mount_tmp, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY, NULL) < 0) {
+                        r = sd_bus_error_set_errnof(error, errno, "Failed to remount read-only %s: %m", mount_tmp);
+                        goto finish;
+                }
+
+        /* Fourth, we move the new bind mount into the propagation
+         * directory. This way it will appear there read-only
+         * right-away. */
+
+        mount_outside = strjoina("/run/systemd/nspawn/propagate/", m->name, "/XXXXXX");
+        if (!mkdtemp(mount_outside)) {
+                r = sd_bus_error_set_errnof(error, errno, "Cannot create propagation directory %s: %m", mount_outside);
+                goto finish;
+        }
+
+        mount_outside_created = true;
+
+        if (mount(mount_tmp, mount_outside, NULL, MS_MOVE, NULL) < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to move %s to %s: %m", mount_tmp, mount_outside);
+                goto finish;
+        }
+
+        mount_outside_mounted = true;
+        mount_tmp_mounted = false;
+
+        (void) rmdir(mount_tmp);
+        mount_tmp_created = false;
+
+        (void) umount(mount_slave);
+        mount_slave_mounted = false;
+
+        (void) rmdir(mount_slave);
+        mount_slave_created = false;
+
+        if (pipe2(errno_pipe_fd, O_CLOEXEC|O_NONBLOCK) < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to create pipe: %m");
+                goto finish;
+        }
+
+        child = fork();
+        if (child < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to fork(): %m");
+                goto finish;
+        }
+
+        if (child == 0) {
+                const char *mount_inside;
+                int mntfd;
+                const char *q;
+
+                errno_pipe_fd[0] = safe_close(errno_pipe_fd[0]);
+
+                q = procfs_file_alloca(m->leader, "ns/mnt");
+                mntfd = open(q, O_RDONLY|O_NOCTTY|O_CLOEXEC);
+                if (mntfd < 0) {
+                        r = log_error_errno(errno, "Failed to open mount namespace of leader: %m");
+                        goto child_fail;
+                }
+
+                if (setns(mntfd, CLONE_NEWNS) < 0) {
+                        r = log_error_errno(errno, "Failed to join namespace of leader: %m");
+                        goto child_fail;
+                }
+
+                if (make_directory)
+                        (void) mkdir_p(dest, 0755);
+
+                /* Fifth, move the mount to the right place inside */
+                mount_inside = strjoina("/run/systemd/nspawn/incoming/", basename(mount_outside));
+                if (mount(mount_inside, dest, NULL, MS_MOVE, NULL) < 0) {
+                        r = log_error_errno(errno, "Failed to mount: %m");
+                        goto child_fail;
+                }
+
+                _exit(EXIT_SUCCESS);
+
+        child_fail:
+                (void) write(errno_pipe_fd[1], &r, sizeof(r));
+                errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]);
+
+                _exit(EXIT_FAILURE);
+        }
+
+        errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]);
+
+        r = wait_for_terminate(child, &si);
+        if (r < 0) {
+                r = sd_bus_error_set_errnof(error, errno, "Failed to wait for client: %m");
+                goto finish;
+        }
+        if (si.si_code != CLD_EXITED) {
+                r = sd_bus_error_setf(error, SD_BUS_ERROR_FAILED, "Client died abnormally.");
+                goto finish;
+        }
+        if (si.si_status != EXIT_SUCCESS) {
+
+                if (read(errno_pipe_fd[0], &r, sizeof(r)) == sizeof(r))
+                        r = sd_bus_error_set_errnof(error, r, "Failed to mount in container: %m");
+                else
+                        r = sd_bus_error_setf(error, SD_BUS_ERROR_FAILED, "Client failed.");
+                goto finish;
+        }
+
+        r = sd_bus_reply_method_return(message, NULL);
+
+finish:
+        if (mount_outside_mounted)
+                umount(mount_outside);
+        if (mount_outside_created)
+                rmdir(mount_outside);
+
+        if (mount_tmp_mounted)
+                umount(mount_tmp);
+        if (mount_tmp_created)
+                rmdir(mount_tmp);
+
+        if (mount_slave_mounted)
+                umount(mount_slave);
+        if (mount_slave_created)
+                rmdir(mount_slave);
+
+        return r;
+}
+
 const sd_bus_vtable machine_vtable[] = {
         SD_BUS_VTABLE_START(0),
         SD_BUS_PROPERTY("Name", "s", NULL, offsetof(Machine, name), SD_BUS_VTABLE_PROPERTY_CONST),
@@ -537,6 +744,7 @@ const sd_bus_vtable machine_vtable[] = {
         SD_BUS_METHOD("GetOSRelease", NULL, "a{ss}", bus_machine_method_get_os_release, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("OpenPTY", NULL, "hs", bus_machine_method_open_pty, 0),
         SD_BUS_METHOD("OpenLogin", NULL, "hs", bus_machine_method_open_login, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("BindMount", "ssbb", NULL, bus_machine_method_bind_mount, 0),
         SD_BUS_VTABLE_END
 };
 
diff --git a/src/machine/machine-dbus.h b/src/machine/machine-dbus.h
index 601252722d..474fec7b10 100644
--- a/src/machine/machine-dbus.h
+++ b/src/machine/machine-dbus.h
@@ -36,6 +36,7 @@ int bus_machine_method_get_addresses(sd_bus *bus, sd_bus_message *message, void
 int bus_machine_method_get_os_release(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
 int bus_machine_method_open_pty(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
 int bus_machine_method_open_login(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
+int bus_machine_method_bind_mount(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
 
 int machine_send_signal(Machine *m, bool new_machine);
 int machine_send_create_reply(Machine *m, sd_bus_error *error);
diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index 9f8c68b184..c1cc5e7eb5 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -901,14 +901,14 @@ static int show_image(int argc, char *argv[], void *userdata) {
                 const char *path = NULL;
 
                 r = sd_bus_call_method(
-                                        bus,
-                                        "org.freedesktop.machine1",
-                                        "/org/freedesktop/machine1",
-                                        "org.freedesktop.machine1.Manager",
-                                        "GetImage",
-                                        &error,
-                                        &reply,
-                                        "s", argv[i]);
+                                bus,
+                                "org.freedesktop.machine1",
+                                "/org/freedesktop/machine1",
+                                "org.freedesktop.machine1.Manager",
+                                "GetImage",
+                                &error,
+                                &reply,
+                                "s", argv[i]);
                 if (r < 0) {
                         log_error("Could not get path to image: %s", bus_error_message(&error, -r));
                         return r;
@@ -930,7 +930,7 @@ static int show_image(int argc, char *argv[], void *userdata) {
 static int kill_machine(int argc, char *argv[], void *userdata) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         sd_bus *bus = userdata;
-        int i;
+        int r, i;
 
         assert(bus);
 
@@ -940,8 +940,6 @@ static int kill_machine(int argc, char *argv[], void *userdata) {
                 arg_kill_who = "all";
 
         for (i = 1; i < argc; i++) {
-                int r;
-
                 r = sd_bus_call_method(
                                 bus,
                                 "org.freedesktop.machine1",
@@ -1143,187 +1141,32 @@ static int copy_files(int argc, char *argv[], void *userdata) {
 }
 
 static int bind_mount(int argc, char *argv[], void *userdata) {
-        char mount_slave[] = "/tmp/propagate.XXXXXX", *mount_tmp, *mount_outside, *p;
+        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         sd_bus *bus = userdata;
-        pid_t child, leader;
-        const char *dest;
-        siginfo_t si;
-        bool mount_slave_created = false, mount_slave_mounted = false,
-                mount_tmp_created = false, mount_tmp_mounted = false,
-                mount_outside_created = false, mount_outside_mounted = false;
         int r;
 
         assert(bus);
 
-        /* One day, when bind mounting /proc/self/fd/n works across
-         * namespace boundaries we should rework this logic to make
-         * use of it... */
-
-        dest = argv[3] ?: argv[2];
-        if (!path_is_absolute(dest)) {
-                log_error("Destination path not absolute.");
-                return -EINVAL;
-        }
-
-        p = strjoina("/run/systemd/nspawn/propagate/", argv[1], "/");
-        if (access(p, F_OK) < 0) {
-                log_error("Container does not allow propagation of mount points.");
-                return -ENOTSUP;
-        }
-
-        r = machine_get_leader(bus, argv[1], &leader);
-        if (r < 0)
-                return r;
-
-        /* Our goal is to install a new bind mount into the container,
-           possibly read-only. This is irritatingly complex
-           unfortunately, currently.
-
-           First, we start by creating a private playground in /tmp,
-           that we can mount MS_SLAVE. (Which is necessary, since
-           MS_MOUNT cannot be applied to mounts with MS_SHARED parent
-           mounts.) */
-
-        if (!mkdtemp(mount_slave))
-                return log_error_errno(errno, "Failed to create playground: %m");
-
-        mount_slave_created = true;
-
-        if (mount(mount_slave, mount_slave, NULL, MS_BIND, NULL) < 0) {
-                r = log_error_errno(errno, "Failed to make bind mount: %m");
-                goto finish;
-        }
-
-        mount_slave_mounted = true;
-
-        if (mount(NULL, mount_slave, NULL, MS_SLAVE, NULL) < 0) {
-                r = log_error_errno(errno, "Failed to remount slave: %m");
-                goto finish;
-        }
-
-        /* Second, we mount the source directory to a directory inside
-           of our MS_SLAVE playground. */
-        mount_tmp = strjoina(mount_slave, "/mount");
-        if (mkdir(mount_tmp, 0700) < 0) {
-                r = log_error_errno(errno, "Failed to create temporary mount: %m");
-                goto finish;
-        }
-
-        mount_tmp_created = true;
-
-        if (mount(argv[2], mount_tmp, NULL, MS_BIND, NULL) < 0) {
-                r = log_error_errno(errno, "Failed to overmount: %m");
-                goto finish;
-        }
-
-        mount_tmp_mounted = true;
-
-        /* Third, we remount the new bind mount read-only if requested. */
-        if (arg_read_only)
-                if (mount(NULL, mount_tmp, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY, NULL) < 0) {
-                        r = log_error_errno(errno, "Failed to mark read-only: %m");
-                        goto finish;
-                }
-
-        /* Fourth, we move the new bind mount into the propagation
-         * directory. This way it will appear there read-only
-         * right-away. */
-
-        mount_outside = strjoina("/run/systemd/nspawn/propagate/", argv[1], "/XXXXXX");
-        if (!mkdtemp(mount_outside)) {
-                r = log_error_errno(errno, "Cannot create propagation directory: %m");
-                goto finish;
-        }
-
-        mount_outside_created = true;
-
-        if (mount(mount_tmp, mount_outside, NULL, MS_MOVE, NULL) < 0) {
-                r = log_error_errno(errno, "Failed to move: %m");
-                goto finish;
-        }
-
-        mount_outside_mounted = true;
-        mount_tmp_mounted = false;
-
-        (void) rmdir(mount_tmp);
-        mount_tmp_created = false;
-
-        (void) umount(mount_slave);
-        mount_slave_mounted = false;
-
-        (void) rmdir(mount_slave);
-        mount_slave_created = false;
-
-        child = fork();
-        if (child < 0) {
-                r = log_error_errno(errno, "Failed to fork(): %m");
-                goto finish;
-        }
-
-        if (child == 0) {
-                const char *mount_inside;
-                int mntfd;
-                const char *q;
-
-                q = procfs_file_alloca(leader, "ns/mnt");
-                mntfd = open(q, O_RDONLY|O_NOCTTY|O_CLOEXEC);
-                if (mntfd < 0) {
-                        log_error_errno(errno, "Failed to open mount namespace of leader: %m");
-                        _exit(EXIT_FAILURE);
-                }
-
-                if (setns(mntfd, CLONE_NEWNS) < 0) {
-                        log_error_errno(errno, "Failed to join namespace of leader: %m");
-                        _exit(EXIT_FAILURE);
-                }
-
-                if (arg_mkdir)
-                        mkdir_p(dest, 0755);
-
-                /* Fifth, move the mount to the right place inside */
-                mount_inside = strjoina("/run/systemd/nspawn/incoming/", basename(mount_outside));
-                if (mount(mount_inside, dest, NULL, MS_MOVE, NULL) < 0) {
-                        log_error_errno(errno, "Failed to mount: %m");
-                        _exit(EXIT_FAILURE);
-                }
-
-                _exit(EXIT_SUCCESS);
-        }
-
-        r = wait_for_terminate(child, &si);
+        r = sd_bus_call_method(
+                        bus,
+                        "org.freedesktop.machine1",
+                        "/org/freedesktop/machine1",
+                        "org.freedesktop.machine1.Manager",
+                        "BindMountMachine",
+                        &error,
+                        NULL,
+                        "sssbb",
+                        argv[1],
+                        argv[2],
+                        argv[3],
+                        arg_read_only,
+                        arg_mkdir);
         if (r < 0) {
-                log_error_errno(r, "Failed to wait for client: %m");
-                goto finish;
-        }
-        if (si.si_code != CLD_EXITED) {
-                log_error("Client died abnormally.");
-                r = -EIO;
-                goto finish;
-        }
-        if (si.si_status != EXIT_SUCCESS) {
-                r = -EIO;
-                goto finish;
+                log_error("Failed to bind mount: %s", bus_error_message(&error, -r));
+                return r;
         }
 
-        r = 0;
-
-finish:
-        if (mount_outside_mounted)
-                umount(mount_outside);
-        if (mount_outside_created)
-                rmdir(mount_outside);
-
-        if (mount_tmp_mounted)
-                umount(mount_tmp);
-        if (mount_tmp_created)
-                umount(mount_tmp);
-
-        if (mount_slave_mounted)
-                umount(mount_slave);
-        if (mount_slave_created)
-                umount(mount_slave);
-
-        return r;
+        return 0;
 }
 
 static int on_machine_removed(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
diff --git a/src/machine/machined-dbus.c b/src/machine/machined-dbus.c
index ac19695c92..2b06d994a8 100644
--- a/src/machine/machined-dbus.c
+++ b/src/machine/machined-dbus.c
@@ -559,6 +559,27 @@ static int method_open_machine_login(sd_bus *bus, sd_bus_message *message, void
         return bus_machine_method_open_login(bus, message, machine, error);
 }
 
+static int method_bind_mount_machine(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        Manager *m = userdata;
+        Machine *machine;
+        const char *name;
+        int r;
+
+        assert(bus);
+        assert(message);
+        assert(m);
+
+        r = sd_bus_message_read(message, "s", &name);
+        if (r < 0)
+                return r;
+
+        machine = hashmap_get(m->machines, name);
+        if (!machine)
+                return sd_bus_error_setf(error, BUS_ERROR_NO_SUCH_MACHINE, "No machine '%s' known", name);
+
+        return bus_machine_method_bind_mount(bus, message, machine, error);
+}
+
 static int method_remove_image(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         _cleanup_(image_unrefp) Image* i = NULL;
         const char *name;
@@ -672,6 +693,7 @@ const sd_bus_vtable manager_vtable[] = {
         SD_BUS_METHOD("RenameImage", "ss", NULL, method_rename_image, 0),
         SD_BUS_METHOD("CloneImage", "ssb", NULL, method_clone_image, 0),
         SD_BUS_METHOD("MarkImageReadOnly", "sb", NULL, method_mark_image_read_only, 0),
+        SD_BUS_METHOD("BindMountMachine", "sssbb", NULL, method_bind_mount_machine, 0),
         SD_BUS_SIGNAL("MachineNew", "so", 0),
         SD_BUS_SIGNAL("MachineRemoved", "so", 0),
         SD_BUS_VTABLE_END
diff --git a/units/systemd-machined.service.in b/units/systemd-machined.service.in
index 15f34d9db7..19c33959d6 100644
--- a/units/systemd-machined.service.in
+++ b/units/systemd-machined.service.in
@@ -15,10 +15,9 @@ After=machine.slice
 [Service]
 ExecStart=@rootlibexecdir@/systemd-machined
 BusName=org.freedesktop.machine1
-CapabilityBoundingSet=CAP_KILL CAP_SYS_PTRACE CAP_SYS_ADMIN CAP_SETGID CAP_SYS_CHROOT CAP_DAC_READ_SEARCH
+CapabilityBoundingSet=CAP_KILL CAP_SYS_PTRACE CAP_SYS_ADMIN CAP_SETGID CAP_SYS_CHROOT CAP_DAC_READ_SEARCH CAP_DAC_OVERRIDE
 WatchdogSec=1min
-PrivateTmp=yes
-PrivateDevices=yes
-PrivateNetwork=yes
-ProtectSystem=full
-ProtectHome=yes
+
+# Note that machined cannot be placed in a mount namespace, since it
+# needs access to the host's mount namespace in order to implement the
+# "machinectl bind" operation.