core: add pre-defined syscall groups to SystemCallFilter= (#3053) (#3157)

Implement sets of system calls to help constructing system call
filters. A set starts with '@' to distinguish from a system call.

Closes: #3053, #3157

man/systemd.exec.xml

@@ -1193,7 +1193,78 @@
         <function>read</function> and <function>write</function>, and
         right after it add a blacklisting of
         <function>write</function>, then <function>write</function>
-        will be removed from the set.) </para></listitem>
+        will be removed from the set.)</para>
+
+        <para>As the number of possible system
+        calls is large, predefined sets of system calls are provided.
+        A set starts with <literal>@</literal> character, followed by
+        name of the set.
+
+        <table>
+          <title>Currently predefined system call sets</title>
+
+          <tgroup cols='2'>
+            <colspec colname='set' />
+            <colspec colname='description' />
+            <thead>
+              <row>
+                <entry>Set</entry>
+                <entry>Description</entry>
+              </row>
+            </thead>
+            <tbody>
+              <row>
+                <entry>@clock</entry>
+                <entry>System calls for changing the system clock (<function>adjtimex()</function>,
+                <function>settimeofday()</function>)</entry>
+              </row>
+              <row>
+                <entry>@io-event</entry>
+                <entry>Event loop use (<function>poll()</function>, <function>select()</function>,
+                <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                <function>eventfd()</function>...)</entry>
+              </row>
+              <row>
+                <entry>@ipc</entry>
+                <entry>SysV IPC, POSIX Message Queues or other IPC (<citerefentry project='man-pages'><refentrytitle>mq_overview</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                <citerefentry project='man-pages'><refentrytitle>svipc</refentrytitle><manvolnum>7</manvolnum></citerefentry>)</entry>
+              </row>
+              <row>
+                <entry>@module</entry>
+                <entry>Kernel module control (<function>create_module()</function>, <function>init_module()</function>...)</entry>
+              </row>
+              <row>
+                <entry>@mount</entry>
+                <entry>File system mounting and unmounting (<function>chroot()</function>, <function>mount()</function>...)</entry>
+              </row>
+              <row>
+                <entry>@network-io</entry>
+                <entry>Socket I/O (including local AF_UNIX):
+                <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                <citerefentry project='man-pages'><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry></entry>
+              </row>
+              <row>
+                <entry>@obsolete</entry>
+                <entry>Unusual, obsolete or unimplemented (<function>fattach()</function>, <function>gtty()</function>, <function>vm86()</function>...)</entry>
+              </row>
+              <row>
+                <entry>@privileged</entry>
+                <entry>All system calls which need superuser capabilities (<citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>)</entry>
+              </row>
+              <row>
+                <entry>@process</entry>
+                <entry>Process control, execution, namespaces (<function>execve()</function>, <function>kill()</function>, <citerefentry project='man-pages'><refentrytitle>namespaces</refentrytitle><manvolnum>7</manvolnum></citerefentry>...)</entry>
+              </row>
+              <row>
+                <entry>@raw-io</entry>
+                <entry>Raw I/O ports (<function>ioperm()</function>, <function>iopl()</function>, <function>pciconfig_read()</function>...)</entry>
+              </row>
+            </tbody>
+          </tgroup>
+        </table>
+
+        Note, that as new system calls are added to the kernel, additional system calls might be added to the groups
+        above, so the contents of the sets may change between systemd versions.</para></listitem>
       </varlistentry>
 
       <varlistentry>

src/core/load-fragment.c

@@ -2396,6 +2396,55 @@ int config_parse_documentation(const char *unit,
 }
 
 #ifdef HAVE_SECCOMP
+static int syscall_filter_parse_one(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                ExecContext *c,
+                bool invert,
+                const char *t,
+                bool warn) {
+        int r;
+
+        if (*t == '@') {
+                const SystemCallFilterSet *set;
+
+                for (set = syscall_filter_sets; set->set_name; set++)
+                        if (streq(set->set_name, t)) {
+                                const char *sys;
+
+                                NULSTR_FOREACH(sys, set->value) {
+                                        r = syscall_filter_parse_one(unit, filename, line, c, invert, sys, false);
+                                        if (r < 0)
+                                                return r;
+                                }
+                                break;
+                        }
+        } else {
+                int id;
+
+                id = seccomp_syscall_resolve_name(t);
+                if (id < 0)  {
+                        if (warn)
+                                log_syntax(unit, LOG_ERR, filename, line, 0, "Failed to parse system call, ignoring: %s", t);
+                        return 0;
+                }
+
+                /* If we previously wanted to forbid a syscall and now
+                 * we want to allow it, then remove it from the list
+                 */
+                if (!invert == c->syscall_whitelist) {
+                        r = set_put(c->syscall_filter, INT_TO_PTR(id + 1));
+                        if (r == 0)
+                                return 0;
+                        if (r < 0)
+                                return log_oom();
+                } else
+                        set_remove(c->syscall_filter, INT_TO_PTR(id + 1));
+        }
+        return 0;
+}
+
 int config_parse_syscall_filter(
                 const char *unit,
                 const char *filename,
@@ -2408,13 +2457,6 @@ int config_parse_syscall_filter(
                 void *data,
                 void *userdata) {
 
-        static const char default_syscalls[] =
-                "execve\0"
-                "exit\0"
-                "exit_group\0"
-                "rt_sigreturn\0"
-                "sigreturn\0";
-
         ExecContext *c = data;
         Unit *u = userdata;
         bool invert = false;
@@ -2448,53 +2490,26 @@ int config_parse_syscall_filter(
                         /* Allow everything but the ones listed */
                         c->syscall_whitelist = false;
                 else {
-                        const char *i;
-
                         /* Allow nothing but the ones listed */
                         c->syscall_whitelist = true;
 
                         /* Accept default syscalls if we are on a whitelist */
-                        NULSTR_FOREACH(i, default_syscalls)  {
+                        r = syscall_filter_parse_one(unit, filename, line, c, false, "@default", false);
-                                int id;
+                        if (r < 0)
-
+                                return r;
-                                id = seccomp_syscall_resolve_name(i);
-                                if (id < 0)
-                                        continue;
-
-                                r = set_put(c->syscall_filter, INT_TO_PTR(id + 1));
-                                if (r == 0)
-                                        continue;
-                                if (r < 0)
-                                        return log_oom();
-                        }
                 }
         }
 
         FOREACH_WORD_QUOTED(word, l, rvalue, state) {
                 _cleanup_free_ char *t = NULL;
-                int id;
 
                 t = strndup(word, l);
                 if (!t)
                         return log_oom();
 
-                id = seccomp_syscall_resolve_name(t);
+                r = syscall_filter_parse_one(unit, filename, line, c, invert, t, true);
-                if (id < 0)  {
+                if (r < 0)
-                        log_syntax(unit, LOG_ERR, filename, line, 0, "Failed to parse system call, ignoring: %s", t);
+                        return r;
-                        continue;
-                }
-
-                /* If we previously wanted to forbid a syscall and now
-                 * we want to allow it, then remove it from the list
-                 */
-                if (!invert == c->syscall_whitelist)  {
-                        r = set_put(c->syscall_filter, INT_TO_PTR(id + 1));
-                        if (r == 0)
-                                continue;
-                        if (r < 0)
-                                return log_oom();
-                } else
-                        set_remove(c->syscall_filter, INT_TO_PTR(id + 1));
         }
         if (!isempty(state))
                 log_syntax(unit, LOG_ERR, filename, line, 0, "Trailing garbage, ignoring.");

src/shared/seccomp-util.c

@@ -88,3 +88,219 @@ int seccomp_add_secondary_archs(scmp_filter_ctx *c) {
         return 0;
 
 }
+
+const SystemCallFilterSet syscall_filter_sets[] = {
+        {
+                /* Clock */
+                .set_name = "@clock",
+                .value =
+                "adjtimex\0"
+                "settimeofday\0"
+        }, {
+                /* Default list */
+                .set_name = "@default",
+                .value =
+                "execve\0"
+                "exit\0"
+                "exit_group\0"
+                "rt_sigreturn\0"
+                "sigreturn\0"
+        }, {
+                /* Event loop use */
+                .set_name = "@io-event",
+                .value =
+                "_newselect\0"
+                "epoll_create1\0"
+                "epoll_create\0"
+                "epoll_ctl\0"
+                "epoll_ctl_old\0"
+                "epoll_pwait\0"
+                "epoll_wait\0"
+                "epoll_wait_old\0"
+                "eventfd2\0"
+                "eventfd\0"
+                "poll\0"
+                "ppoll\0"
+                "pselect6\0"
+                "select\0"
+        }, {
+                /* Message queues, SYSV IPC or other IPC: unusual */
+                .set_name = "@ipc",
+                .value = "ipc\0"
+                "mq_getsetattr\0"
+                "mq_notify\0"
+                "mq_open\0"
+                "mq_timedreceive\0"
+                "mq_timedsend\0"
+                "mq_unlink\0"
+                "msgctl\0"
+                "msgget\0"
+                "msgrcv\0"
+                "msgsnd\0"
+                "process_vm_readv\0"
+                "process_vm_writev\0"
+                "semctl\0"
+                "semget\0"
+                "semop\0"
+                "semtimedop\0"
+                "shmat\0"
+                "shmctl\0"
+                "shmdt\0"
+                "shmget\0"
+        }, {
+                /* Kernel module control */
+                .set_name = "@module",
+                .value =
+                "create_module\0"
+                "delete_module\0"
+                "finit_module\0"
+                "init_module\0"
+        }, {
+                /* Mounting */
+                .set_name = "@mount",
+                .value =
+                "chroot\0"
+                "mount\0"
+                "oldumount\0"
+                "pivot_root\0"
+                "umount2\0"
+                "umount\0"
+        }, {
+                /* Network or Unix socket IO, should not be needed if not network facing */
+                .set_name = "@network-io",
+                .value =
+                "accept4\0"
+                "accept\0"
+                "bind\0"
+                "connect\0"
+                "getpeername\0"
+                "getsockname\0"
+                "getsockopt\0"
+                "listen\0"
+                "recv\0"
+                "recvfrom\0"
+                "recvmmsg\0"
+                "recvmsg\0"
+                "send\0"
+                "sendmmsg\0"
+                "sendmsg\0"
+                "sendto\0"
+                "setsockopt\0"
+                "shutdown\0"
+                "socket\0"
+                "socketcall\0"
+                "socketpair\0"
+        }, {
+                /* Unusual, obsolete or unimplemented, some unknown even to libseccomp */
+                .set_name = "@obsolete",
+                .value =
+                "_sysctl\0"
+                "afs_syscall\0"
+                "break\0"
+                "fattach\0"
+                "fdetach\0"
+                "ftime\0"
+                "get_kernel_syms\0"
+                "get_mempolicy\0"
+                "getmsg\0"
+                "getpmsg\0"
+                "gtty\0"
+                "isastream\0"
+                "lock\0"
+                "madvise1\0"
+                "modify_ldt\0"
+                "mpx\0"
+                "pciconfig_iobase\0"
+                "perf_event_open\0"
+                "prof\0"
+                "profil\0"
+                "putmsg\0"
+                "putpmsg\0"
+                "query_module\0"
+                "rtas\0"
+                "s390_runtime_instr\0"
+                "security\0"
+                "sgetmask\0"
+                "ssetmask\0"
+                "stty\0"
+                "subpage_prot\0"
+                "switch_endian\0"
+                "sys_debug_setcontext\0"
+                "tuxcall\0"
+                "ulimit\0"
+                "uselib\0"
+                "vm86\0"
+                "vm86old\0"
+                "vserver\0"
+        }, {
+                /* Nice grab-bag of all system calls which need superuser capabilities */
+                .set_name = "@privileged",
+                .value =
+                "@clock\0"
+                "@module\0"
+                "@raw-io\0"
+                "acct\0"
+                "bdflush\0"
+                "bpf\0"
+                "chown32\0"
+                "chown\0"
+                "chroot\0"
+                "fchown32\0"
+                "fchown\0"
+                "fchownat\0"
+                "kexec_file_load\0"
+                "kexec_load\0"
+                "lchown32\0"
+                "lchown\0"
+                "nfsservctl\0"
+                "pivot_root\0"
+                "quotactl\0"
+                "reboot\0"
+                "setdomainname\0"
+                "setfsuid32\0"
+                "setfsuid\0"
+                "setgroups32\0"
+                "setgroups\0"
+                "sethostname\0"
+                "setresuid32\0"
+                "setresuid\0"
+                "setreuid32\0"
+                "setreuid\0"
+                "setuid32\0"
+                "setuid\0"
+                "stime\0"
+                "swapoff\0"
+                "swapon\0"
+                "sysctl\0"
+                "vhangup\0"
+        }, {
+                /* Process control, execution, namespaces */
+                .set_name = "@process",
+                .value =
+                "arch_prctl\0"
+                "clone\0"
+                "execve\0"
+                "execveat\0"
+                "fork\0"
+                "kill\0"
+                "prctl\0"
+                "setns\0"
+                "tgkill\0"
+                "tkill\0"
+                "unshare\0"
+                "vfork\0"
+        }, {
+                /* Raw I/O ports */
+                .set_name = "@raw-io",
+                .value =
+                "ioperm\0"
+                "iopl\0"
+                "pciconfig_read\0"
+                "pciconfig_write\0"
+                "s390_pci_mmio_read\0"
+                "s390_pci_mmio_write\0"
+        }, {
+                .set_name = NULL,
+                .value = NULL
+        }
+};

src/shared/seccomp-util.h

@@ -26,3 +26,10 @@ const char* seccomp_arch_to_string(uint32_t c);
 int seccomp_arch_from_string(const char *n, uint32_t *ret);
 
 int seccomp_add_secondary_archs(scmp_filter_ctx *c);
+
+typedef struct SystemCallFilterSet {
+        const char *set_name;
+        const char *value;
+} SystemCallFilterSet;
+
+extern const SystemCallFilterSet syscall_filter_sets[];