diff options
| -rw-r--r-- | man/systemd.exec.xml | 65 | ||||
| -rw-r--r-- | src/core/dbus-execute.c | 7 | ||||
| -rw-r--r-- | src/core/execute.c | 168 | ||||
| -rw-r--r-- | src/core/execute.h | 1 | ||||
| -rw-r--r-- | src/core/load-fragment-gperf.gperf.m4 | 3 | ||||
| -rw-r--r-- | src/shared/bus-unit-util.c | 2 |
6 files changed, 215 insertions, 31 deletions
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml index 58ba582911..2190da55d4 100644 --- a/man/systemd.exec.xml +++ b/man/systemd.exec.xml @@ -107,36 +107,29 @@ <varlistentry> <term><varname>WorkingDirectory=</varname></term> - <listitem><para>Takes a directory path relative to the service's root - directory specified by <varname>RootDirectory=</varname>, or the - special value <literal>~</literal>. Sets the working directory - for executed processes. If set to <literal>~</literal>, the - home directory of the user specified in - <varname>User=</varname> is used. If not set, defaults to the - root directory when systemd is running as a system instance - and the respective user's home directory if run as user. If - the setting is prefixed with the <literal>-</literal> - character, a missing working directory is not considered - fatal. If <varname>RootDirectory=</varname> is not set, then - <varname>WorkingDirectory=</varname> is relative to the root of - the system running the service manager. - Note that setting this parameter might result in - additional dependencies to be added to the unit (see - above).</para></listitem> + <listitem><para>Takes a directory path relative to the service's root directory specified by + <varname>RootDirectory=</varname>, or the special value <literal>~</literal>. Sets the working directory for + executed processes. If set to <literal>~</literal>, the home directory of the user specified in + <varname>User=</varname> is used. If not set, defaults to the root directory when systemd is running as a + system instance and the respective user's home directory if run as user. If the setting is prefixed with the + <literal>-</literal> character, a missing working directory is not considered fatal. If + <varname>RootDirectory=</varname> is not set, then <varname>WorkingDirectory=</varname> is relative to the root + of the system running the service manager. Note that setting this parameter might result in additional + dependencies to be added to the unit (see above).</para></listitem> </varlistentry> <varlistentry> <term><varname>RootDirectory=</varname></term> - <listitem><para>Takes a directory path relative to the host's root directory - (i.e. the root of the system running the service manager). Sets the - root directory for executed processes, with the <citerefentry - project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry> - system call. If this is used, it must be ensured that the - process binary and all its auxiliary files are available in - the <function>chroot()</function> jail. Note that setting this - parameter might result in additional dependencies to be added - to the unit (see above).</para></listitem> + <listitem><para>Takes a directory path relative to the host's root directory (i.e. the root of the system + running the service manager). Sets the root directory for executed processes, with the <citerefentry + project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry> system + call. If this is used, it must be ensured that the process binary and all its auxiliary files are available in + the <function>chroot()</function> jail. Note that setting this parameter might result in additional + dependencies to be added to the unit (see above).</para> + + <para>The <varname>PrivateUsers=</varname> setting is particularly useful in conjunction with + <varname>RootDirectory=</varname>. For details, see below.</para></listitem> </varlistentry> <varlistentry> @@ -999,6 +992,28 @@ </varlistentry> <varlistentry> + <term><varname>PrivateUsers=</varname></term> + + <listitem><para>Takes a boolean argument. If true, sets up a new user namespace for the executed processes and + configures a minimal user and group mapping, that maps the <literal>root</literal> user and group as well as + the unit's own user and group to themselves and everything else to the <literal>nobody</literal> user and + group. This is useful to securely detach the user and group databases used by the unit from the rest of the + system, and thus to create an effective sandbox environment. All files, directories, processes, IPC objects and + other resources owned by users/groups not equalling <literal>root</literal> or the unit's own will stay visible + from within the unit but appear owned by the <literal>nobody</literal> user and group. If this mode is enabled, + all unit processes are run without privileges in the host user namespace (regardless if the unit's own + user/group is <literal>root</literal> or not). Specifically this means that the process will have zero process + capabilities on the host's user namespace, but full capabilities within the service's user namespace. Settings + such as <varname>CapabilityBoundingSet=</varname> will affect only the latter, and there's no way to acquire + additional capabilities in the host's user namespace. Defaults to off.</para> + + <para>This setting is particularly useful in conjunction with <varname>RootDirectory=</varname>, as the need to + synchronize the user and group databases in the root directory and on the host is reduced, as the only users + and groups who need to be matched are <literal>root</literal>, <literal>nobody</literal> and the unit's own + user and group.</para></listitem> + </varlistentry> + + <varlistentry> <term><varname>ProtectSystem=</varname></term> <listitem><para>Takes a boolean argument or diff --git a/src/core/dbus-execute.c b/src/core/dbus-execute.c index 9c50cd93e5..4b3bbfbc7d 100644 --- a/src/core/dbus-execute.c +++ b/src/core/dbus-execute.c @@ -705,8 +705,9 @@ const sd_bus_vtable bus_exec_vtable[] = { SD_BUS_PROPERTY("InaccessiblePaths", "as", NULL, offsetof(ExecContext, inaccessible_paths), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("MountFlags", "t", bus_property_get_ulong, offsetof(ExecContext, mount_flags), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("PrivateTmp", "b", bus_property_get_bool, offsetof(ExecContext, private_tmp), SD_BUS_VTABLE_PROPERTY_CONST), - SD_BUS_PROPERTY("PrivateNetwork", "b", bus_property_get_bool, offsetof(ExecContext, private_network), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("PrivateDevices", "b", bus_property_get_bool, offsetof(ExecContext, private_devices), SD_BUS_VTABLE_PROPERTY_CONST), + SD_BUS_PROPERTY("PrivateNetwork", "b", bus_property_get_bool, offsetof(ExecContext, private_network), SD_BUS_VTABLE_PROPERTY_CONST), + SD_BUS_PROPERTY("PrivateUsers", "b", bus_property_get_bool, offsetof(ExecContext, private_users), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("ProtectHome", "s", bus_property_get_protect_home, offsetof(ExecContext, protect_home), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("ProtectSystem", "s", bus_property_get_protect_system, offsetof(ExecContext, protect_system), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("SameProcessGroup", "b", bus_property_get_bool, offsetof(ExecContext, same_pgrp), SD_BUS_VTABLE_PROPERTY_CONST), @@ -1068,7 +1069,7 @@ int bus_exec_context_set_transient_property( } else if (STR_IN_SET(name, "IgnoreSIGPIPE", "TTYVHangup", "TTYReset", - "PrivateTmp", "PrivateDevices", "PrivateNetwork", + "PrivateTmp", "PrivateDevices", "PrivateNetwork", "PrivateUsers", "NoNewPrivileges", "SyslogLevelPrefix", "MemoryDenyWriteExecute", "RestrictRealtime", "DynamicUser")) { int b; @@ -1090,6 +1091,8 @@ int bus_exec_context_set_transient_property( c->private_devices = b; else if (streq(name, "PrivateNetwork")) c->private_network = b; + else if (streq(name, "PrivateUsers")) + c->private_users = b; else if (streq(name, "NoNewPrivileges")) c->no_new_privileges = b; else if (streq(name, "SyslogLevelPrefix")) diff --git a/src/core/execute.c b/src/core/execute.c index 26e9cd5339..cec3b3cf40 100644 --- a/src/core/execute.c +++ b/src/core/execute.c @@ -25,6 +25,7 @@ #include <signal.h> #include <string.h> #include <sys/capability.h> +#include <sys/eventfd.h> #include <sys/mman.h> #include <sys/personality.h> #include <sys/prctl.h> @@ -1526,6 +1527,159 @@ static bool exec_needs_mount_namespace( return false; } +static int setup_private_users(uid_t uid, gid_t gid) { + _cleanup_free_ char *uid_map = NULL, *gid_map = NULL; + _cleanup_close_pair_ int errno_pipe[2] = { -1, -1 }; + _cleanup_close_ int unshare_ready_fd = -1; + _cleanup_(sigkill_waitp) pid_t pid = 0; + uint64_t c = 1; + siginfo_t si; + ssize_t n; + int r; + + /* Set up a user namespace and map root to root, the selected UID/GID to itself, and everything else to + * nobody. In order to be able to write this mapping we need CAP_SETUID in the original user namespace, which + * we however lack after opening the user namespace. To work around this we fork() a temporary child process, + * which waits for the parent to create the new user namespace while staying in the original namespace. The + * child then writes the UID mapping, under full privileges. The parent waits for the child to finish and + * continues execution normally. */ + + if (uid != 0 && uid_is_valid(uid)) + asprintf(&uid_map, + "0 0 1\n" /* Map root → root */ + UID_FMT " " UID_FMT " 1\n", /* Map $UID → $UID */ + uid, uid); /* The case where the above is the same */ + else + uid_map = strdup("0 0 1\n"); + if (!uid_map) + return -ENOMEM; + + if (gid != 0 && gid_is_valid(gid)) + asprintf(&gid_map, + "0 0 1\n" /* Map root → root */ + GID_FMT " " GID_FMT " 1\n", /* Map $GID → $GID */ + gid, gid); + else + gid_map = strdup("0 0 1\n"); /* The case where the above is the same */ + if (!gid_map) + return -ENOMEM; + + /* Create a communication channel so that the parent can tell the child when it finished creating the user + * namespace. */ + unshare_ready_fd = eventfd(0, EFD_CLOEXEC); + if (unshare_ready_fd < 0) + return -errno; + + /* Create a communication channel so that the child can tell the parent a proper error code in case it + * failed. */ + if (pipe2(errno_pipe, O_CLOEXEC) < 0) + return -errno; + + pid = fork(); + if (pid < 0) + return -errno; + + if (pid == 0) { + _cleanup_close_ int fd = -1; + const char *a; + pid_t ppid; + + /* Child process, running in the original user namespace. Let's update the parent's UID/GID map from + * here, after the parent opened its own user namespace. */ + + ppid = getppid(); + errno_pipe[0] = safe_close(errno_pipe[0]); + + /* Wait until the parent unshared the user namespace */ + if (read(unshare_ready_fd, &c, sizeof(c)) < 0) { + r = -errno; + goto child_fail; + } + + /* Disable the setgroups() system call in the child user namespace, for good. */ + a = procfs_file_alloca(ppid, "setgroups"); + fd = open(a, O_WRONLY|O_CLOEXEC); + if (fd < 0) { + if (errno != ENOENT) { + r = -errno; + goto child_fail; + } + + /* If the file is missing the kernel is too old, let's continue anyway. */ + } else { + if (write(fd, "deny\n", 5) < 0) { + r = -errno; + goto child_fail; + } + + fd = safe_close(fd); + } + + /* First write the GID map */ + a = procfs_file_alloca(ppid, "gid_map"); + fd = open(a, O_WRONLY|O_CLOEXEC); + if (fd < 0) { + r = -errno; + goto child_fail; + } + if (write(fd, gid_map, strlen(gid_map)) < 0) { + r = -errno; + goto child_fail; + } + fd = safe_close(fd); + + /* The write the UID map */ + a = procfs_file_alloca(ppid, "uid_map"); + fd = open(a, O_WRONLY|O_CLOEXEC); + if (fd < 0) { + r = -errno; + goto child_fail; + } + if (write(fd, uid_map, strlen(uid_map)) < 0) { + r = -errno; + goto child_fail; + } + + _exit(EXIT_SUCCESS); + + child_fail: + (void) write(errno_pipe[1], &r, sizeof(r)); + _exit(EXIT_FAILURE); + } + + errno_pipe[1] = safe_close(errno_pipe[1]); + + if (unshare(CLONE_NEWUSER) < 0) + return -errno; + + /* Let the child know that the namespace is ready now */ + if (write(unshare_ready_fd, &c, sizeof(c)) < 0) + return -errno; + + /* Try to read an error code from the child */ + n = read(errno_pipe[0], &r, sizeof(r)); + if (n < 0) + return -errno; + if (n == sizeof(r)) { /* an error code was sent to us */ + if (r < 0) + return r; + return -EIO; + } + if (n != 0) /* on success we should have read 0 bytes */ + return -EIO; + + r = wait_for_terminate(pid, &si); + if (r < 0) + return r; + pid = 0; + + /* If something strange happened with the child, let's consider this fatal, too */ + if (si.si_code != CLD_EXITED || si.si_status != 0) + return -EIO; + + return 0; +} + static void append_socket_pair(int *array, unsigned *n, int pair[2]) { assert(array); assert(n); @@ -2037,6 +2191,14 @@ static int exec_child( } #endif + if (params->apply_permissions && context->private_users) { + r = setup_private_users(uid, gid); + if (r < 0) { + *exit_status = EXIT_USER; + return r; + } + } + /* We repeat the fd closing here, to make sure that * nothing is leaked from the PAM modules. Note that * we are more aggressive this time since socket_fd @@ -2598,8 +2760,9 @@ void exec_context_dump(ExecContext *c, FILE* f, const char *prefix) { "%sRootDirectory: %s\n" "%sNonBlocking: %s\n" "%sPrivateTmp: %s\n" - "%sPrivateNetwork: %s\n" "%sPrivateDevices: %s\n" + "%sPrivateNetwork: %s\n" + "%sPrivateUsers: %s\n" "%sProtectHome: %s\n" "%sProtectSystem: %s\n" "%sIgnoreSIGPIPE: %s\n" @@ -2610,8 +2773,9 @@ void exec_context_dump(ExecContext *c, FILE* f, const char *prefix) { prefix, c->root_directory ? c->root_directory : "/", prefix, yes_no(c->non_blocking), prefix, yes_no(c->private_tmp), - prefix, yes_no(c->private_network), prefix, yes_no(c->private_devices), + prefix, yes_no(c->private_network), + prefix, yes_no(c->private_users), prefix, protect_home_to_string(c->protect_home), prefix, protect_system_to_string(c->protect_system), prefix, yes_no(c->ignore_sigpipe), diff --git a/src/core/execute.h b/src/core/execute.h index 48cc18fbb3..5fac3e85e8 100644 --- a/src/core/execute.h +++ b/src/core/execute.h @@ -171,6 +171,7 @@ struct ExecContext { bool private_tmp; bool private_network; bool private_devices; + bool private_users; ProtectSystem protect_system; ProtectHome protect_home; diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4 index 396f847213..251155b428 100644 --- a/src/core/load-fragment-gperf.gperf.m4 +++ b/src/core/load-fragment-gperf.gperf.m4 @@ -88,8 +88,9 @@ $1.ReadWritePaths, config_parse_namespace_path_strv, 0, $1.ReadOnlyPaths, config_parse_namespace_path_strv, 0, offsetof($1, exec_context.read_only_paths) $1.InaccessiblePaths, config_parse_namespace_path_strv, 0, offsetof($1, exec_context.inaccessible_paths) $1.PrivateTmp, config_parse_bool, 0, offsetof($1, exec_context.private_tmp) -$1.PrivateNetwork, config_parse_bool, 0, offsetof($1, exec_context.private_network) $1.PrivateDevices, config_parse_bool, 0, offsetof($1, exec_context.private_devices) +$1.PrivateNetwork, config_parse_bool, 0, offsetof($1, exec_context.private_network) +$1.PrivateUsers, config_parse_bool, 0, offsetof($1, exec_context.private_users) $1.ProtectSystem, config_parse_protect_system, 0, offsetof($1, exec_context) $1.ProtectHome, config_parse_protect_home, 0, offsetof($1, exec_context) $1.MountFlags, config_parse_exec_mount_flags, 0, offsetof($1, exec_context) diff --git a/src/shared/bus-unit-util.c b/src/shared/bus-unit-util.c index 14bf8ad627..9d8061b539 100644 --- a/src/shared/bus-unit-util.c +++ b/src/shared/bus-unit-util.c @@ -202,7 +202,7 @@ int bus_append_unit_property_assignment(sd_bus_message *m, const char *assignmen "CPUAccounting", "MemoryAccounting", "IOAccounting", "BlockIOAccounting", "TasksAccounting", "SendSIGHUP", "SendSIGKILL", "WakeSystem", "DefaultDependencies", "IgnoreSIGPIPE", "TTYVHangup", "TTYReset", "RemainAfterExit", - "PrivateTmp", "PrivateDevices", "PrivateNetwork", "NoNewPrivileges", + "PrivateTmp", "PrivateDevices", "PrivateNetwork", "PrivateUsers", "NoNewPrivileges", "SyslogLevelPrefix", "Delegate", "RemainAfterElapse", "MemoryDenyWriteExecute", "RestrictRealtime", "DynamicUser")) { |