seccomp: rework seccomp code, to improve compat with some archs

This substantially reworks the seccomp code, to ensure better
compatibility with some architectures, including i386.

So far we relied on libseccomp's internal handling of the multiple
syscall ABIs supported on Linux. This is problematic however, as it does
not define clear semantics if an ABI is not able to support specific
seccomp rules we install.

This rework hence changes a couple of things:

- We no longer use seccomp_rule_add(), but only
  seccomp_rule_add_exact(), and fail the installation of a filter if the
  architecture doesn't support it.

- We no longer rely on adding multiple syscall architectures to a single filter,
  but instead install a separate filter for each syscall architecture
  supported. This way, we can install a strict filter for x86-64, while
  permitting a less strict filter for i386.

- All high-level filter additions are now moved from execute.c to
  seccomp-util.c, so that we can test them independently of the service
  execution logic.

- Tests have been added for all types of our seccomp filters.

- SystemCallFilters= and SystemCallArchitectures= are now implemented in
  independent filters and installation logic, as they semantically are
  very much independent of each other.

Fixes: #4575

1 files changed, 531 insertions, 121 deletions

diff --git a/src/shared/seccomp-util.c b/src/shared/seccomp-util.c
index 5972d8e3e0..497426f605 100644
--- a/src/shared/seccomp-util.c
+++ b/src/shared/seccomp-util.c
@@ -18,17 +18,52 @@
 ***/
 
 #include <errno.h>
+#include <linux/seccomp.h>
 #include <seccomp.h>
 #include <stddef.h>
+#include <sys/mman.h>
 #include <sys/prctl.h>
-#include <linux/seccomp.h>
+#include <sys/shm.h>
 
+#include "af-list.h"
 #include "alloc-util.h"
 #include "macro.h"
 #include "nsflags.h"
 #include "seccomp-util.h"
 #include "string-util.h"
 #include "util.h"
+#include "errno-list.h"
+
+const uint32_t seccomp_local_archs[] = {
+
+#if defined(__i386__) || defined(__x86_64__)
+                SCMP_ARCH_X86,
+                SCMP_ARCH_X86_64,
+                SCMP_ARCH_X32,
+
+#elif defined(__arm__) || defined(__aarch64__)
+                SCMP_ARCH_ARM,
+                SCMP_ARCH_AARCH64,
+
+#elif defined(__mips__) || defined(__mips64__)
+                SCMP_ARCH_MIPS,
+                SCMP_ARCH_MIPS64,
+                SCMP_ARCH_MIPS64N32,
+                SCMP_ARCH_MIPSEL,
+                SCMP_ARCH_MIPSEL64,
+                SCMP_ARCH_MIPSEL64N32,
+
+#elif defined(__powerpc__) || defined(__powerpc64__)
+                SCMP_ARCH_PPC,
+                SCMP_ARCH_PPC64,
+                SCMP_ARCH_PPC64LE,
+
+#elif defined(__s390__) || defined(__s390x__)
+                SCMP_ARCH_S390,
+                SCMP_ARCH_S390X,
+#endif
+                (uint32_t) -1
+        };
 
 const char* seccomp_arch_to_string(uint32_t c) {
         /* Maintain order used in <seccomp.h>.
@@ -122,18 +157,37 @@ int seccomp_arch_from_string(const char *n, uint32_t *ret) {
         return 0;
 }
 
-int seccomp_init_conservative(scmp_filter_ctx *ret, uint32_t default_action) {
+int seccomp_init_for_arch(scmp_filter_ctx *ret, uint32_t arch, uint32_t default_action) {
         scmp_filter_ctx seccomp;
         int r;
 
-        /* Much like seccomp_init(), but tries to be a bit more conservative in its defaults: all secondary archs are
-         * added by default, and NNP is turned off. */
+        /* Much like seccomp_init(), but initializes the filter for one specific architecture only, without affecting
+         * any others. Also, turns off the NNP fiddling. */
 
         seccomp = seccomp_init(default_action);
         if (!seccomp)
                 return -ENOMEM;
 
-        r = seccomp_add_secondary_archs(seccomp);
+        if (arch != SCMP_ARCH_NATIVE &&
+            arch != seccomp_arch_native()) {
+
+                r = seccomp_arch_add(seccomp, arch);
+                if (r < 0)
+                        goto finish;
+
+                r = seccomp_arch_remove(seccomp, seccomp_arch_native());
+                if (r < 0)
+                        goto finish;
+
+                assert(seccomp_arch_exist(seccomp, arch) >= 0);
+                assert(seccomp_arch_exist(seccomp, SCMP_ARCH_NATIVE) == -EEXIST);
+                assert(seccomp_arch_exist(seccomp, seccomp_arch_native()) == -EEXIST);
+        } else {
+                assert(seccomp_arch_exist(seccomp, SCMP_ARCH_NATIVE) >= 0);
+                assert(seccomp_arch_exist(seccomp, seccomp_arch_native()) >= 0);
+        }
+
+        r = seccomp_attr_set(seccomp, SCMP_FLTATR_ACT_BADARCH, SCMP_ACT_ALLOW);
         if (r < 0)
                 goto finish;
 
@@ -149,56 +203,6 @@ finish:
         return r;
 }
 
-int seccomp_add_secondary_archs(scmp_filter_ctx ctx) {
-
-        /* Add in all possible secondary archs we are aware of that
-         * this kernel might support. */
-
-        static const int seccomp_arches[] = {
-#if defined(__i386__) || defined(__x86_64__)
-                SCMP_ARCH_X86,
-                SCMP_ARCH_X86_64,
-                SCMP_ARCH_X32,
-
-#elif defined(__arm__) || defined(__aarch64__)
-                SCMP_ARCH_ARM,
-                SCMP_ARCH_AARCH64,
-
-#elif defined(__arm__) || defined(__aarch64__)
-                SCMP_ARCH_ARM,
-                SCMP_ARCH_AARCH64,
-
-#elif defined(__mips__) || defined(__mips64__)
-                SCMP_ARCH_MIPS,
-                SCMP_ARCH_MIPS64,
-                SCMP_ARCH_MIPS64N32,
-                SCMP_ARCH_MIPSEL,
-                SCMP_ARCH_MIPSEL64,
-                SCMP_ARCH_MIPSEL64N32,
-
-#elif defined(__powerpc__) || defined(__powerpc64__)
-                SCMP_ARCH_PPC,
-                SCMP_ARCH_PPC64,
-                SCMP_ARCH_PPC64LE,
-
-#elif defined(__s390__) || defined(__s390x__)
-                SCMP_ARCH_S390,
-                SCMP_ARCH_S390X,
-#endif
-        };
-
-        unsigned i;
-        int r;
-
-        for (i = 0; i < ELEMENTSOF(seccomp_arches); i++) {
-                r = seccomp_arch_add(ctx, seccomp_arches[i]);
-                if (r < 0 && r != -EEXIST)
-                        return r;
-        }
-
-        return 0;
-}
-
 static bool is_basic_seccomp_available(void) {
         int r;
         r = prctl(PR_GET_SECCOMP, 0, 0, 0, 0);
@@ -612,7 +616,12 @@ const SyscallFilterSet *syscall_filter_set_find(const char *name) {
         return NULL;
 }
 
-int seccomp_add_syscall_filter_set(scmp_filter_ctx seccomp, const SyscallFilterSet *set, uint32_t action) {
+static int seccomp_add_syscall_filter_set(
+                scmp_filter_ctx seccomp,
+                uint32_t default_action,
+                const SyscallFilterSet *set,
+                uint32_t action) {
+
         const char *sys;
         int r;
 
@@ -629,47 +638,102 @@ int seccomp_add_syscall_filter_set(scmp_filter_ctx seccomp, const SyscallFilterS
                         if (!other)
                                 return -EINVAL;
 
-                        r = seccomp_add_syscall_filter_set(seccomp, other, action);
+                        r = seccomp_add_syscall_filter_set(seccomp, default_action, other, action);
+                        if (r < 0)
+                                return r;
                 } else {
                         id = seccomp_syscall_resolve_name(sys);
                         if (id == __NR_SCMP_ERROR)
-                                return -EINVAL;
+                                return -EINVAL; /* Not known at all? Then that's a real error */
 
-                        r = seccomp_rule_add(seccomp, action, id, 0);
+                        r = seccomp_rule_add_exact(seccomp, action, id, 0);
+                        if (r < 0)
+                                /* If the system call is not known on this architecture, then that's fine, let's ignore it */
+                                log_debug_errno(r, "Failed to add rule for system call %s, ignoring: %m", sys);
                 }
+        }
+
+        return 0;
+}
+
+int seccomp_load_syscall_filter_set(uint32_t default_action, const SyscallFilterSet *set, uint32_t action) {
+        uint32_t arch;
+        int r;
+
+        assert(set);
+
+        /* The one-stop solution: allocate a seccomp object, add the specified filter to it, and apply it. Once for
+         * earch local arch. */
+
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
+
+                r = seccomp_init_for_arch(&seccomp, arch, default_action);
                 if (r < 0)
                         return r;
+
+                r = seccomp_add_syscall_filter_set(seccomp, default_action, set, action);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add filter set, ignoring: %m");
+                        continue;
+                }
+
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
         }
 
         return 0;
 }
 
-int seccomp_load_filter_set(uint32_t default_action, const SyscallFilterSet *set, uint32_t action) {
-        scmp_filter_ctx seccomp;
+int seccomp_load_syscall_filter_set_raw(uint32_t default_action, Set* set, uint32_t action) {
+        uint32_t arch;
         int r;
 
-        assert(set);
+        /* Similar to seccomp_load_syscall_filter_set(), but takes a raw Set* of syscalls, instead of a
+         * SyscallFilterSet* table. */
 
-        /* The one-stop solution: allocate a seccomp object, add a filter to it, and apply it */
+        if (set_isempty(set) && default_action == SCMP_ACT_ALLOW)
+                return 0;
 
-        r = seccomp_init_conservative(&seccomp, default_action);
-        if (r < 0)
-                return r;
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+                Iterator i;
+                void *id;
 
-        r = seccomp_add_syscall_filter_set(seccomp, set, action);
-        if (r < 0)
-                goto finish;
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
 
-        r = seccomp_load(seccomp);
+                r = seccomp_init_for_arch(&seccomp, arch, default_action);
+                if (r < 0)
+                        return r;
 
-finish:
-        seccomp_release(seccomp);
-        return r;
+                SET_FOREACH(id, set, i) {
+                        r = seccomp_rule_add_exact(seccomp, action, PTR_TO_INT(id) - 1, 0);
+                        if (r < 0) {
+                                /* If the system call is not known on this architecture, then that's fine, let's ignore it */
+                                _cleanup_free_ char *n = NULL;
+
+                                n = seccomp_syscall_resolve_num_arch(arch, PTR_TO_INT(id) - 1);
+                                log_debug_errno(r, "Failed to add rule for system call %s, ignoring: %m", strna(n));
+                        }
+                }
+
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+        }
+
+        return 0;
 }
 
 int seccomp_restrict_namespaces(unsigned long retain) {
-        scmp_filter_ctx seccomp;
-        unsigned i;
+        uint32_t arch;
         int r;
 
         if (log_get_max_level() >= LOG_DEBUG) {
@@ -683,74 +747,420 @@ int seccomp_restrict_namespaces(unsigned long retain) {
         if ((retain & NAMESPACE_FLAGS_ALL) == NAMESPACE_FLAGS_ALL)
                 return 0;
 
-        r = seccomp_init_conservative(&seccomp, SCMP_ACT_ALLOW);
-        if (r < 0)
-                return r;
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+                unsigned i;
 
-        if ((retain & NAMESPACE_FLAGS_ALL) == 0)
-                /* If every single kind of namespace shall be prohibited, then let's block the whole setns() syscall
-                 * altogether. */
-                r = seccomp_rule_add(
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
+
+                r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
+                if (r < 0)
+                        return r;
+
+                if ((retain & NAMESPACE_FLAGS_ALL) == 0)
+                        /* If every single kind of namespace shall be prohibited, then let's block the whole setns() syscall
+                         * altogether. */
+                        r = seccomp_rule_add_exact(
+                                        seccomp,
+                                        SCMP_ACT_ERRNO(EPERM),
+                                        SCMP_SYS(setns),
+                                        0);
+                else
+                        /* Otherwise, block only the invocations with the appropriate flags in the loop below, but also the
+                         * special invocation with a zero flags argument, right here. */
+                        r = seccomp_rule_add_exact(
+                                        seccomp,
+                                        SCMP_ACT_ERRNO(EPERM),
+                                        SCMP_SYS(setns),
+                                        1,
+                                        SCMP_A1(SCMP_CMP_EQ, 0));
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add setns() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                        continue;
+                }
+
+                for (i = 0; namespace_flag_map[i].name; i++) {
+                        unsigned long f;
+
+                        f = namespace_flag_map[i].flag;
+                        if ((retain & f) == f) {
+                                log_debug("Permitting %s.", namespace_flag_map[i].name);
+                                continue;
+                        }
+
+                        log_debug("Blocking %s.", namespace_flag_map[i].name);
+
+                        r = seccomp_rule_add_exact(
+                                        seccomp,
+                                        SCMP_ACT_ERRNO(EPERM),
+                                        SCMP_SYS(unshare),
+                                        1,
+                                        SCMP_A0(SCMP_CMP_MASKED_EQ, f, f));
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to add unshare() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                break;
+                        }
+
+                        r = seccomp_rule_add_exact(
+                                        seccomp,
+                                        SCMP_ACT_ERRNO(EPERM),
+                                        SCMP_SYS(clone),
+                                        1,
+                                        SCMP_A0(SCMP_CMP_MASKED_EQ, f, f));
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to add clone() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                break;
+                        }
+
+                        if ((retain & NAMESPACE_FLAGS_ALL) != 0) {
+                                r = seccomp_rule_add_exact(
+                                                seccomp,
+                                                SCMP_ACT_ERRNO(EPERM),
+                                                SCMP_SYS(setns),
+                                                1,
+                                                SCMP_A1(SCMP_CMP_MASKED_EQ, f, f));
+                                if (r < 0) {
+                                        log_debug_errno(r, "Failed to add setns() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                        break;
+                                }
+                        }
+                }
+                if (r < 0)
+                        continue;
+
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install namespace restriction rules for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+        }
+
+        return 0;
+}
+
+int seccomp_protect_sysctl(void) {
+        uint32_t arch;
+        int r;
+
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
+
+                r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
+                if (r < 0)
+                        return r;
+
+                r = seccomp_rule_add_exact(
                                 seccomp,
                                 SCMP_ACT_ERRNO(EPERM),
-                                SCMP_SYS(setns),
+                                SCMP_SYS(_sysctl),
                                 0);
-        else
-                /* Otherwise, block only the invocations with the appropriate flags in the loop below, but also the
-                 * special invocation with a zero flags argument, right here. */
-                r = seccomp_rule_add(
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add _sysctl() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                        continue;
+                }
+
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install sysctl protection rules for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+        }
+
+        return 0;
+}
+
+int seccomp_restrict_address_families(Set *address_families, bool whitelist) {
+        uint32_t arch;
+        int r;
+
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+                Iterator i;
+
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
+
+                r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
+                if (r < 0)
+                        return r;
+
+                if (whitelist) {
+                        int af, first = 0, last = 0;
+                        void *afp;
+
+                        /* If this is a whitelist, we first block the address families that are out of range and then
+                         * everything that is not in the set. First, we find the lowest and highest address family in
+                         * the set. */
+
+                        SET_FOREACH(afp, address_families, i) {
+                                af = PTR_TO_INT(afp);
+
+                                if (af <= 0 || af >= af_max())
+                                        continue;
+
+                                if (first == 0 || af < first)
+                                        first = af;
+
+                                if (last == 0 || af > last)
+                                        last = af;
+                        }
+
+                        assert((first == 0) == (last == 0));
+
+                        if (first == 0) {
+
+                                /* No entries in the valid range, block everything */
+                                r = seccomp_rule_add_exact(
+                                                seccomp,
+                                                SCMP_ACT_ERRNO(EAFNOSUPPORT),
+                                                SCMP_SYS(socket),
+                                                0);
+                                if (r < 0) {
+                                        log_debug_errno(r, "Failed to add socket() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                        continue;
+                                }
+
+                        } else {
+
+                                /* Block everything below the first entry */
+                                r = seccomp_rule_add_exact(
+                                                seccomp,
+                                                SCMP_ACT_ERRNO(EAFNOSUPPORT),
+                                                SCMP_SYS(socket),
+                                                1,
+                                                SCMP_A0(SCMP_CMP_LT, first));
+                                if (r < 0) {
+                                        log_debug_errno(r, "Failed to add socket() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                        continue;
+                                }
+
+                                /* Block everything above the last entry */
+                                r = seccomp_rule_add_exact(
+                                                seccomp,
+                                                SCMP_ACT_ERRNO(EAFNOSUPPORT),
+                                                SCMP_SYS(socket),
+                                                1,
+                                                SCMP_A0(SCMP_CMP_GT, last));
+                                if (r < 0) {
+                                        log_debug_errno(r, "Failed to add socket() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                        continue;
+                                }
+
+                                /* Block everything between the first and last entry */
+                                for (af = 1; af < af_max(); af++) {
+
+                                        if (set_contains(address_families, INT_TO_PTR(af)))
+                                                continue;
+
+                                        r = seccomp_rule_add_exact(
+                                                        seccomp,
+                                                        SCMP_ACT_ERRNO(EAFNOSUPPORT),
+                                                        SCMP_SYS(socket),
+                                                        1,
+                                                        SCMP_A0(SCMP_CMP_EQ, af));
+                                        if (r < 0)
+                                                break;
+                                }
+
+                                if (r < 0) {
+                                        log_debug_errno(r, "Failed to add socket() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                        continue;
+                                }
+                        }
+
+                } else {
+                        void *af;
+
+                        /* If this is a blacklist, then generate one rule for
+                         * each address family that are then combined in OR
+                         * checks. */
+
+                        SET_FOREACH(af, address_families, i) {
+
+                                r = seccomp_rule_add_exact(
+                                                seccomp,
+                                                SCMP_ACT_ERRNO(EAFNOSUPPORT),
+                                                SCMP_SYS(socket),
+                                                1,
+                                                SCMP_A0(SCMP_CMP_EQ, PTR_TO_INT(af)));
+                                if (r < 0)
+                                        break;
+                        }
+
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to add socket() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                continue;
+                        }
+                }
+
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install socket family rules for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+        }
+
+        return 0;
+}
+
+int seccomp_restrict_realtime(void) {
+        static const int permitted_policies[] = {
+                SCHED_OTHER,
+                SCHED_BATCH,
+                SCHED_IDLE,
+        };
+
+        int r, max_policy = 0;
+        uint32_t arch;
+        unsigned i;
+
+        /* Determine the highest policy constant we want to allow */
+        for (i = 0; i < ELEMENTSOF(permitted_policies); i++)
+                if (permitted_policies[i] > max_policy)
+                        max_policy = permitted_policies[i];
+
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+                int p;
+
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
+
+                r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
+                if (r < 0)
+                        return r;
+
+                /* Go through all policies with lower values than that, and block them -- unless they appear in the
+                 * whitelist. */
+                for (p = 0; p < max_policy; p++) {
+                        bool good = false;
+
+                        /* Check if this is in the whitelist. */
+                        for (i = 0; i < ELEMENTSOF(permitted_policies); i++)
+                                if (permitted_policies[i] == p) {
+                                        good = true;
+                                        break;
+                                }
+
+                        if (good)
+                                continue;
+
+                        /* Deny this policy */
+                        r = seccomp_rule_add_exact(
+                                        seccomp,
+                                        SCMP_ACT_ERRNO(EPERM),
+                                        SCMP_SYS(sched_setscheduler),
+                                        1,
+                                        SCMP_A1(SCMP_CMP_EQ, p));
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to add scheduler rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                                continue;
+                        }
+                }
+
+                /* Blacklist all other policies, i.e. the ones with higher values. Note that all comparisons are
+                 * unsigned here, hence no need no check for < 0 values. */
+                r = seccomp_rule_add_exact(
                                 seccomp,
                                 SCMP_ACT_ERRNO(EPERM),
-                                SCMP_SYS(setns),
+                                SCMP_SYS(sched_setscheduler),
                                 1,
-                                SCMP_A1(SCMP_CMP_EQ, 0));
-        if (r < 0)
-                goto finish;
+                                SCMP_A1(SCMP_CMP_GT, max_policy));
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add scheduler rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                        continue;
+                }
 
-        for (i = 0; namespace_flag_map[i].name; i++) {
-                unsigned long f;
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install realtime protection rules for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+        }
+
+        return 0;
+}
+
+int seccomp_memory_deny_write_execute(void) {
+        uint32_t arch;
+        int r;
+
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
 
-                f = namespace_flag_map[i].flag;
-                if ((retain & f) == f) {
-                        log_debug("Permitting %s.", namespace_flag_map[i].name);
+                log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
+
+                r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
+                if (r < 0)
+                        return r;
+
+                r = seccomp_rule_add_exact(
+                                seccomp,
+                                SCMP_ACT_ERRNO(EPERM),
+                                SCMP_SYS(mmap),
+                                1,
+                                SCMP_A2(SCMP_CMP_MASKED_EQ, PROT_EXEC|PROT_WRITE, PROT_EXEC|PROT_WRITE));
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add mmap() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
                         continue;
                 }
 
-                log_debug("Blocking %s.", namespace_flag_map[i].name);
-
-                r = seccomp_rule_add(
+                r = seccomp_rule_add_exact(
                                 seccomp,
                                 SCMP_ACT_ERRNO(EPERM),
-                                SCMP_SYS(unshare),
+                                SCMP_SYS(mprotect),
                                 1,
-                                SCMP_A0(SCMP_CMP_MASKED_EQ, f, f));
-                if (r < 0)
-                        goto finish;
+                                SCMP_A2(SCMP_CMP_MASKED_EQ, PROT_EXEC, PROT_EXEC));
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add mprotect() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                        continue;
+                }
 
-                r = seccomp_rule_add(
+                r = seccomp_rule_add_exact(
                                 seccomp,
                                 SCMP_ACT_ERRNO(EPERM),
-                                SCMP_SYS(clone),
+                                SCMP_SYS(shmat),
                                 1,
-                                SCMP_A0(SCMP_CMP_MASKED_EQ, f, f));
+                                SCMP_A2(SCMP_CMP_MASKED_EQ, SHM_EXEC, SHM_EXEC));
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add shmat() rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+                        continue;
+                }
+
+                r = seccomp_load(seccomp);
+                if (IN_SET(r, -EPERM, -EACCES))
+                        return r;
                 if (r < 0)
-                        goto finish;
+                        log_debug_errno(r, "Failed to install MemoryDenyWriteExecute= rule for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
+        }
 
-                if ((retain & NAMESPACE_FLAGS_ALL) != 0) {
-                        r = seccomp_rule_add(
-                                        seccomp,
-                                        SCMP_ACT_ERRNO(EPERM),
-                                        SCMP_SYS(setns),
-                                        1,
-                                        SCMP_A1(SCMP_CMP_MASKED_EQ, f, f));
-                        if (r < 0)
-                                goto finish;
-                }
+        return 0;
+}
+
+int seccomp_restrict_archs(Set *archs) {
+        _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+        Iterator i;
+        void *id;
+        int r;
+
+        /* This installs a filter with no rules, but that restricts the system call architectures to the specified
+         * list. */
+
+        seccomp = seccomp_init(SCMP_ACT_ALLOW);
+        if (!seccomp)
+                return -ENOMEM;
+
+        SET_FOREACH(id, archs, i) {
+                r = seccomp_arch_add(seccomp, PTR_TO_UINT32(id) - 1);
+                if (r == -EEXIST)
+                        continue;
+                if (r < 0)
+                        return r;
         }
 
-        r = seccomp_load(seccomp);
+        r = seccomp_attr_set(seccomp, SCMP_FLTATR_CTL_NNP, 0);
+        if (r < 0)
+                return r;
 
-finish:
-        seccomp_release(seccomp);
-        return r;
+        return seccomp_load(seccomp);
 }