Merge pull request #14037 from poettering/machinectl-pw-agent

spawn ask pw tty agent from "machinectl start"

man/systemd.exec.xml

@@ -402,11 +402,11 @@ CapabilityBoundingSet=~CAP_B CAP_C</programlisting>
         <varname>SystemCallFilter=</varname>, <varname>SystemCallArchitectures=</varname>,
         <varname>RestrictAddressFamilies=</varname>, <varname>RestrictNamespaces=</varname>,
         <varname>PrivateDevices=</varname>, <varname>ProtectKernelTunables=</varname>,
-        <varname>ProtectKernelModules=</varname>, <varname>MemoryDenyWriteExecute=</varname>,
-        <varname>RestrictRealtime=</varname>, <varname>RestrictSUIDSGID=</varname>,
-        <varname>DynamicUser=</varname> or <varname>LockPersonality=</varname> are specified. Note that even
-        if this setting is overridden by them, <command>systemctl show</command> shows the original value of
-        this setting. Also see <ulink
+        <varname>ProtectKernelModules=</varname>, <varname>ProtectKernelLogs=</varname>,
+        <varname>MemoryDenyWriteExecute=</varname>, <varname>RestrictRealtime=</varname>,
+        <varname>RestrictSUIDSGID=</varname>, <varname>DynamicUser=</varname> or <varname>LockPersonality=</varname>
+        are specified. Note that even if this setting is overridden by them, <command>systemctl show</command> shows the
+        original value of this setting. Also see <ulink
         url="https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html">No New Privileges
         Flag</ulink>.</para></listitem>
       </varlistentry>
@@ -1321,6 +1321,22 @@ BindReadOnlyPaths=/var/lib/systemd</programlisting>
         <xi:include href="system-only.xml" xpointer="singular"/></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>ProtectKernelLogs=</varname></term>
+
+        <listitem><para>Takes a boolean argument. If true, access to the kernel log ring buffer will be denied. It is
+        recommended to turn this on for most services that do not need to read from or write to the kernel log ring
+        buffer. Enabling this option removes <constant>CAP_SYSLOG</constant> from the capability bounding set for this
+        unit, and installs a system call filter to block the
+        <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+        system call (not to be confused with the libc API
+        <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+        for userspace logging). The kernel exposes its log buffer to userspace via <filename>/dev/kmsg</filename> and
+        <filename>/proc/kmsg</filename>. If enabled, these are made inaccessible to all the processes in the unit.</para>
+
+        <xi:include href="system-only.xml" xpointer="singular"/></listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>ProtectControlGroups=</varname></term>
 
@@ -1772,8 +1788,8 @@ SystemCallErrorNumber=EPERM</programlisting>
         mappings. Specifically these are the options <varname>PrivateTmp=</varname>,
         <varname>PrivateDevices=</varname>, <varname>ProtectSystem=</varname>, <varname>ProtectHome=</varname>,
         <varname>ProtectKernelTunables=</varname>, <varname>ProtectControlGroups=</varname>,
-        <varname>ReadOnlyPaths=</varname>, <varname>InaccessiblePaths=</varname> and
-        <varname>ReadWritePaths=</varname>.</para></listitem>
+        <varname>ProtectKernelLogs=</varname>, <varname>ReadOnlyPaths=</varname>,
+        <varname>InaccessiblePaths=</varname> and <varname>ReadWritePaths=</varname>.</para></listitem>
       </varlistentry>
 
       <varlistentry>

src/analyze/analyze-security.c

@@ -64,6 +64,7 @@ struct security_info {
         bool protect_control_groups;
         bool protect_kernel_modules;
         bool protect_kernel_tunables;
+        bool protect_kernel_logs;
 
         char *protect_home;
         char *protect_system;
@@ -772,6 +773,16 @@ static const struct security_assessor security_assessor_table[] = {
                 .assess = assess_bool,
                 .offset = offsetof(struct security_info, protect_kernel_tunables),
         },
+        {
+                .id = "ProtectKernelLogs=",
+                .description_good = "Service cannot read from or write to the kernel log ring buffer",
+                .description_bad = "Service may read from or write to the kernel log ring buffer",
+                .url = "https://www.freedesktop.org/software/systemd/man/systemd.exec.html#ProtectKernelLogs=",
+                .weight = 1000,
+                .range = 1,
+                .assess = assess_bool,
+                .offset = offsetof(struct security_info, protect_kernel_logs),
+        },
         {
                 .id = "ProtectHome=",
                 .url = "https://www.freedesktop.org/software/systemd/man/systemd.exec.html#ProtectHome=",
@@ -1906,6 +1917,7 @@ static int acquire_security_info(sd_bus *bus, const char *name, struct security_
                 { "ProtectHostname",         "b",       NULL,                                    offsetof(struct security_info, protect_hostname)          },
                 { "ProtectKernelModules",    "b",       NULL,                                    offsetof(struct security_info, protect_kernel_modules)    },
                 { "ProtectKernelTunables",   "b",       NULL,                                    offsetof(struct security_info, protect_kernel_tunables)   },
+                { "ProtectKernelLogs",       "b",       NULL,                                    offsetof(struct security_info, protect_kernel_logs)       },
                 { "ProtectSystem",           "s",       NULL,                                    offsetof(struct security_info, protect_system)            },
                 { "RemoveIPC",               "b",       NULL,                                    offsetof(struct security_info, remove_ipc)                },
                 { "RestrictAddressFamilies", "(bas)",   property_read_restrict_address_families, 0                                                         },
@@ -1980,6 +1992,9 @@ static int acquire_security_info(sd_bus *bus, const char *name, struct security_
         if (info->protect_kernel_modules)
                 info->capability_bounding_set &= ~(UINT64_C(1) << CAP_SYS_MODULE);
 
+        if (info->protect_kernel_logs)
+                info->capability_bounding_set &= ~(UINT64_C(1) << CAP_SYSLOG);
+
         if (info->private_devices)
                 info->capability_bounding_set &= ~((UINT64_C(1) << CAP_MKNOD) |
                                                    (UINT64_C(1) << CAP_SYS_RAWIO));

src/core/dbus-execute.c

@@ -783,6 +783,7 @@ const sd_bus_vtable bus_exec_vtable[] = {
         SD_BUS_PROPERTY("PrivateDevices", "b", bus_property_get_bool, offsetof(ExecContext, private_devices), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("ProtectKernelTunables", "b", bus_property_get_bool, offsetof(ExecContext, protect_kernel_tunables), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("ProtectKernelModules", "b", bus_property_get_bool, offsetof(ExecContext, protect_kernel_modules), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("ProtectKernelLogs", "b", bus_property_get_bool, offsetof(ExecContext, protect_kernel_logs), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("ProtectControlGroups", "b", bus_property_get_bool, offsetof(ExecContext, protect_control_groups), 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),
@@ -1274,6 +1275,9 @@ int bus_exec_context_set_transient_property(
         if (streq(name, "ProtectKernelModules"))
                 return bus_set_transient_bool(u, name, &c->protect_kernel_modules, message, flags, error);
 
+        if (streq(name, "ProtectKernelLogs"))
+                return bus_set_transient_bool(u, name, &c->protect_kernel_logs, message, flags, error);
+
         if (streq(name, "ProtectControlGroups"))
                 return bus_set_transient_bool(u, name, &c->protect_control_groups, message, flags, error);
 

src/core/execute.c

@@ -1396,6 +1396,7 @@ static bool context_has_no_new_privileges(const ExecContext *c) {
                 exec_context_restrict_namespaces_set(c) ||
                 c->protect_kernel_tunables ||
                 c->protect_kernel_modules ||
+                c->protect_kernel_logs ||
                 c->private_devices ||
                 context_has_syscall_filters(c) ||
                 !set_isempty(c->syscall_archs) ||
@@ -1542,6 +1543,19 @@ static int apply_protect_kernel_modules(const Unit *u, const ExecContext *c) {
         return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_MODULE, SCMP_ACT_ERRNO(EPERM), false);
 }
 
+static int apply_protect_kernel_logs(const Unit *u, const ExecContext *c) {
+        assert(u);
+        assert(c);
+
+        if (!c->protect_kernel_logs)
+                return 0;
+
+        if (skip_seccomp_unavailable(u, "ProtectKernelLogs="))
+                return 0;
+
+        return seccomp_protect_syslog();
+}
+
 static int apply_private_devices(const Unit *u, const ExecContext *c) {
         assert(u);
         assert(c);
@@ -1858,6 +1872,7 @@ static bool exec_needs_mount_namespace(
             context->protect_home != PROTECT_HOME_NO ||
             context->protect_kernel_tunables ||
             context->protect_kernel_modules ||
+            context->protect_kernel_logs ||
             context->protect_control_groups)
                 return true;
 
@@ -2493,6 +2508,7 @@ static int apply_mount_namespace(
                         .protect_control_groups = context->protect_control_groups,
                         .protect_kernel_tunables = context->protect_kernel_tunables,
                         .protect_kernel_modules = context->protect_kernel_modules,
+                        .protect_kernel_logs = context->protect_kernel_logs,
                         .protect_hostname = context->protect_hostname,
                         .mount_apivfs = context->mount_apivfs,
                         .private_mounts = context->private_mounts,
@@ -3679,6 +3695,12 @@ static int exec_child(
                         return log_unit_error_errno(unit, r, "Failed to apply module loading restrictions: %m");
                 }
 
+                r = apply_protect_kernel_logs(unit, context);
+                if (r < 0) {
+                        *exit_status = EXIT_SECCOMP;
+                        return log_unit_error_errno(unit, r, "Failed to apply kernel log restrictions: %m");
+                }
+
                 r = apply_private_devices(unit, context);
                 if (r < 0) {
                         *exit_status = EXIT_SECCOMP;
@@ -4318,6 +4340,7 @@ void exec_context_dump(const ExecContext *c, FILE* f, const char *prefix) {
                 "%sPrivateDevices: %s\n"
                 "%sProtectKernelTunables: %s\n"
                 "%sProtectKernelModules: %s\n"
+                "%sProtectKernelLogs: %s\n"
                 "%sProtectControlGroups: %s\n"
                 "%sPrivateNetwork: %s\n"
                 "%sPrivateUsers: %s\n"
@@ -4338,6 +4361,7 @@ void exec_context_dump(const ExecContext *c, FILE* f, const char *prefix) {
                 prefix, yes_no(c->private_devices),
                 prefix, yes_no(c->protect_kernel_tunables),
                 prefix, yes_no(c->protect_kernel_modules),
+                prefix, yes_no(c->protect_kernel_logs),
                 prefix, yes_no(c->protect_control_groups),
                 prefix, yes_no(c->private_network),
                 prefix, yes_no(c->private_users),

src/core/execute.h

@@ -257,6 +257,7 @@ struct ExecContext {
         bool private_mounts;
         bool protect_kernel_tunables;
         bool protect_kernel_modules;
+        bool protect_kernel_logs;
         bool protect_control_groups;
         ProtectSystem protect_system;
         ProtectHome protect_home;

src/core/load-fragment-gperf.gperf.m4

@@ -115,6 +115,7 @@ $1.PrivateTmp,                   config_parse_bool,                  0,
 $1.PrivateDevices,               config_parse_bool,                  0,                             offsetof($1, exec_context.private_devices)
 $1.ProtectKernelTunables,        config_parse_bool,                  0,                             offsetof($1, exec_context.protect_kernel_tunables)
 $1.ProtectKernelModules,         config_parse_bool,                  0,                             offsetof($1, exec_context.protect_kernel_modules)
+$1.ProtectKernelLogs,            config_parse_bool,                  0,                             offsetof($1, exec_context.protect_kernel_logs)
 $1.ProtectControlGroups,         config_parse_bool,                  0,                             offsetof($1, exec_context.protect_control_groups)
 $1.NetworkNamespacePath,         config_parse_unit_path_printf,      0,                             offsetof($1, exec_context.network_namespace_path)
 $1.PrivateNetwork,               config_parse_bool,                  0,                             offsetof($1, exec_context.private_network)

src/core/namespace.c

@@ -109,6 +109,12 @@ static const MountEntry protect_kernel_modules_table[] = {
         { "/usr/lib/modules",    INACCESSIBLE, true  },
 };
 
+/* ProtectKernelLogs= option */
+static const MountEntry protect_kernel_logs_table[] = {
+        { "/proc/kmsg",          INACCESSIBLE, true },
+        { "/dev/kmsg",           INACCESSIBLE, true },
+};
+
 /*
  * ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of
  * system should be protected by ProtectSystem=
@@ -1147,8 +1153,9 @@ static size_t namespace_calculate_mounts(
                 n_temporary_filesystems +
                 ns_info->private_dev +
                 (ns_info->protect_kernel_tunables ? ELEMENTSOF(protect_kernel_tunables_table) : 0) +
-                (ns_info->protect_control_groups ? 1 : 0) +
                 (ns_info->protect_kernel_modules ? ELEMENTSOF(protect_kernel_modules_table) : 0) +
+                (ns_info->protect_kernel_logs ? ELEMENTSOF(protect_kernel_logs_table) : 0) +
+                (ns_info->protect_control_groups ? 1 : 0) +
                 protect_home_cnt + protect_system_cnt +
                 (ns_info->protect_hostname ? 2 : 0) +
                 (namespace_info_mount_apivfs(ns_info) ? ELEMENTSOF(apivfs_table) : 0);
@@ -1319,6 +1326,12 @@ int setup_namespace(
                                 goto finish;
                 }
 
+                if (ns_info->protect_kernel_logs) {
+                        r = append_static_mounts(&m, protect_kernel_logs_table, ELEMENTSOF(protect_kernel_logs_table), ns_info->ignore_protect_paths);
+                        if (r < 0)
+                                goto finish;
+                }
+
                 if (ns_info->protect_control_groups) {
                         *(m++) = (MountEntry) {
                                 .path_const = "/sys/fs/cgroup",

src/core/namespace.h

@@ -51,6 +51,7 @@ struct NamespaceInfo {
         bool protect_control_groups:1;
         bool protect_kernel_tunables:1;
         bool protect_kernel_modules:1;
+        bool protect_kernel_logs:1;
         bool mount_apivfs:1;
         bool protect_hostname:1;
 };

src/core/unit.c

@@ -4269,6 +4269,9 @@ int unit_patch_contexts(Unit *u) {
                 if (ec->protect_kernel_modules)
                         ec->capability_bounding_set &= ~(UINT64_C(1) << CAP_SYS_MODULE);
 
+                if (ec->protect_kernel_logs)
+                        ec->capability_bounding_set &= ~(UINT64_C(1) << CAP_SYSLOG);
+
                 if (ec->dynamic_user) {
                         if (!ec->user) {
                                 r = user_from_unit_name(u, &ec->user);

src/machine/machinectl.c

@@ -46,6 +46,7 @@
 #include "sigbus.h"
 #include "signal-util.h"
 #include "sort-util.h"
+#include "spawn-ask-password-agent.h"
 #include "spawn-polkit-agent.h"
 #include "stdio-util.h"
 #include "string-table.h"
@@ -1722,6 +1723,7 @@ static int start_machine(int argc, char *argv[], void *userdata) {
         assert(bus);
 
         polkit_agent_open_if_enabled(arg_transport, arg_ask_password);
+        ask_password_agent_open_if_enabled(arg_transport, arg_ask_password);
 
         r = bus_wait_for_jobs_new(bus, &w);
         if (r < 0)

src/shared/bus-unit-util.c

@@ -818,8 +818,8 @@ static int bus_append_execute_property(sd_bus_message *m, const char *field, con
                        "PrivateDevices", "PrivateNetwork", "PrivateUsers", "PrivateMounts",
                        "NoNewPrivileges", "SyslogLevelPrefix", "MemoryDenyWriteExecute", "RestrictRealtime",
                        "DynamicUser", "RemoveIPC", "ProtectKernelTunables", "ProtectKernelModules",
-                       "ProtectControlGroups", "MountAPIVFS", "CPUSchedulingResetOnFork", "LockPersonality",
-                       "ProtectHostname", "RestrictSUIDSGID"))
+                       "ProtectKernelLogs", "ProtectControlGroups", "MountAPIVFS", "CPUSchedulingResetOnFork",
+                       "LockPersonality", "ProtectHostname", "RestrictSUIDSGID"))
                 return bus_append_parse_boolean(m, field, eq);
 
         if (STR_IN_SET(field,

src/shared/seccomp-util.c

@@ -1281,6 +1281,38 @@ int seccomp_protect_sysctl(void) {
         return 0;
 }
 
+int seccomp_protect_syslog(void) {
+        uint32_t arch;
+        int r;
+
+        SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+                _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+
+                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(syslog),
+                                0);
+
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to add syslog() rule for architecture %s, skipping %m", seccomp_arch_to_string(arch));
+                        continue;
+                }
+
+                r = seccomp_load(seccomp);
+                if (ERRNO_IS_SECCOMP_FATAL(r))
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Failed to install syslog 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;

src/shared/seccomp-util.h

@@ -82,6 +82,7 @@ int seccomp_parse_syscall_filter(
 int seccomp_restrict_archs(Set *archs);
 int seccomp_restrict_namespaces(unsigned long retain);
 int seccomp_protect_sysctl(void);
+int seccomp_protect_syslog(void);
 int seccomp_restrict_address_families(Set *address_families, bool whitelist);
 int seccomp_restrict_realtime(void);
 int seccomp_memory_deny_write_execute(void);

src/shared/spawn-ask-password-agent.c

@@ -46,3 +46,16 @@ void ask_password_agent_close(void) {
         (void) wait_for_terminate(agent_pid, NULL);
         agent_pid = 0;
 }
+
+int ask_password_agent_open_if_enabled(BusTransport transport, bool ask_password) {
+
+        /* Open the ask password agent as a child process if necessary */
+
+        if (transport != BUS_TRANSPORT_LOCAL)
+                return 0;
+
+        if (!ask_password)
+                return 0;
+
+        return ask_password_agent_open();
+}

src/shared/spawn-ask-password-agent.h

@@ -1,5 +1,11 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 #pragma once
 
+#include <stdbool.h>
+
+#include "bus-util.h"
+
 int ask_password_agent_open(void);
 void ask_password_agent_close(void);
+
+int ask_password_agent_open_if_enabled(BusTransport transport, bool ask_password);

src/shared/spawn-polkit-agent.c

@@ -83,3 +83,16 @@ void polkit_agent_close(void) {
 }
 
 #endif
+
+int polkit_agent_open_if_enabled(BusTransport transport, bool ask_password) {
+
+        /* Open the polkit agent as a child process if necessary */
+
+        if (transport != BUS_TRANSPORT_LOCAL)
+                return 0;
+
+        if (!ask_password)
+                return 0;
+
+        return polkit_agent_open();
+}

src/shared/spawn-polkit-agent.h

@@ -1,22 +1,11 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 #pragma once
 
+#include <stdbool.h>
+
 #include "bus-util.h"
 
 int polkit_agent_open(void);
 void polkit_agent_close(void);
 
-static inline int polkit_agent_open_if_enabled(
-                BusTransport transport,
-                bool ask_password) {
-
-        /* Open the polkit agent as a child process if necessary */
-
-        if (transport != BUS_TRANSPORT_LOCAL)
-                return 0;
-
-        if (!ask_password)
-                return 0;
-
-        return polkit_agent_open();
-}
+int polkit_agent_open_if_enabled(BusTransport transport, bool ask_password);

src/systemctl/systemctl.c

@@ -236,22 +236,16 @@ static void release_busses(void) {
                 buses[w] = sd_bus_flush_close_unref(buses[w]);
 }
 
-static void ask_password_agent_open_if_enabled(void) {
+static void ask_password_agent_open_maybe(void) {
         /* Open the password agent as a child process if necessary */
 
         if (arg_dry_run)
                 return;
 
-        if (!arg_ask_password)
-                return;
-
         if (arg_scope != UNIT_FILE_SYSTEM)
                 return;
 
-        if (arg_transport != BUS_TRANSPORT_LOCAL)
-                return;
-
-        ask_password_agent_open();
+        ask_password_agent_open_if_enabled(arg_transport, arg_ask_password);
 }
 
 static void polkit_agent_open_maybe(void) {
@@ -3071,7 +3065,7 @@ static int start_unit(int argc, char *argv[], void *userdata) {
         if (r < 0)
                 return r;
 
-        ask_password_agent_open_if_enabled();
+        ask_password_agent_open_maybe();
         polkit_agent_open_maybe();
 
         if (arg_action == ACTION_SYSTEMCTL) {

src/test/test-namespace.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
+#include <fcntl.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 
@@ -9,7 +10,9 @@
 #include "process-util.h"
 #include "string-util.h"
 #include "tests.h"
+#include "user-util.h"
 #include "util.h"
+#include "virt.h"
 
 static void test_tmpdir(const char *id, const char *A, const char *B) {
         _cleanup_free_ char *a, *b;
@@ -48,14 +51,16 @@ static void test_tmpdir(const char *id, const char *A, const char *B) {
         assert_se(rmdir(b) >= 0);
 }
 
-static int test_netns(void) {
+static void test_netns(void) {
         _cleanup_close_pair_ int s[2] = { -1, -1 };
         pid_t pid1, pid2, pid3;
         int r, n = 0;
         siginfo_t si;
 
-        if (geteuid() > 0)
-                return log_tests_skipped("not root");
+        if (geteuid() > 0) {
+                (void) log_tests_skipped("not root");
+                return;
+        }
 
         assert_se(socketpair(AF_UNIX, SOCK_DGRAM, 0, s) >= 0);
 
@@ -102,7 +107,62 @@ static int test_netns(void) {
         n += si.si_status;
 
         assert_se(n == 1);
-        return EXIT_SUCCESS;
+}
+
+static void test_protect_kernel_logs(void) {
+        int r;
+        pid_t pid;
+        static const NamespaceInfo ns_info = {
+                .protect_kernel_logs = true,
+        };
+
+        if (geteuid() > 0) {
+                (void) log_tests_skipped("not root");
+                return;
+        }
+
+        /* In a container we likely don't have access to /dev/kmsg */
+        if (detect_container() > 0) {
+                (void) log_tests_skipped("in container");
+                return;
+        }
+
+
+        pid = fork();
+        assert_se(pid >= 0);
+
+        if (pid == 0) {
+                _cleanup_close_ int fd = -1;
+
+                fd = open("/dev/kmsg", O_RDONLY | O_CLOEXEC);
+                assert_se(fd > 0);
+
+                r = setup_namespace(NULL,
+                                    NULL,
+                                    &ns_info,
+                                    NULL,
+                                    NULL,
+                                    NULL,
+                                    NULL,
+                                    NULL, 0,
+                                    NULL, 0,
+                                    NULL,
+                                    NULL,
+                                    PROTECT_HOME_NO,
+                                    PROTECT_SYSTEM_NO,
+                                    0,
+                                    0,
+                                    NULL);
+                assert_se(r == 0);
+
+                assert_se(setresuid(UID_NOBODY, UID_NOBODY, UID_NOBODY) >= 0);
+                assert_se(open("/dev/kmsg", O_RDONLY | O_CLOEXEC) < 0);
+                assert_se(errno == EACCES);
+
+                _exit(EXIT_SUCCESS);
+        }
+
+        assert_se(wait_for_terminate_and_check("ns-kernellogs", pid, WAIT_LOG) == EXIT_SUCCESS);
 }
 
 int main(int argc, char *argv[]) {
@@ -133,5 +193,8 @@ int main(int argc, char *argv[]) {
 
         test_tmpdir("sys-devices-pci0000:00-0000:00:1a.0-usb3-3\\x2d1-3\\x2d1:1.0-bluetooth-hci0.device", z, zz);
 
-        return test_netns();
+        test_netns();
+        test_protect_kernel_logs();
+
+        return EXIT_SUCCESS;
 }

src/test/test-seccomp.c

@@ -323,6 +323,48 @@ static void test_protect_sysctl(void) {
         assert_se(wait_for_terminate_and_check("sysctlseccomp", pid, WAIT_LOG) == EXIT_SUCCESS);
 }
 
+static void test_protect_syslog(void) {
+        pid_t pid;
+
+        log_info("/* %s */", __func__);
+
+        if (!is_seccomp_available()) {
+                log_notice("Seccomp not available, skipping %s", __func__);
+                return;
+        }
+        if (geteuid() != 0) {
+                log_notice("Not root, skipping %s", __func__);
+                return;
+        }
+
+        /* in containers syslog() is likely missing anyway */
+        if (detect_container() > 0) {
+                log_notice("Testing in container, skipping %s", __func__);
+                return;
+        }
+
+        pid = fork();
+        assert_se(pid >= 0);
+
+        if (pid == 0) {
+#if defined __NR_syslog && __NR_syslog > 0
+                assert_se(syscall(__NR_syslog, -1, NULL, 0) < 0);
+                assert_se(errno == EINVAL);
+#endif
+
+                assert_se(seccomp_protect_syslog() >= 0);
+
+#if defined __NR_syslog && __NR_syslog > 0
+                assert_se(syscall(__NR_syslog, 0, 0, 0) < 0);
+                assert_se(errno == EPERM);
+#endif
+
+                _exit(EXIT_SUCCESS);
+        }
+
+        assert_se(wait_for_terminate_and_check("syslogseccomp", pid, WAIT_LOG) == EXIT_SUCCESS);
+}
+
 static void test_restrict_address_families(void) {
         pid_t pid;
 
@@ -983,6 +1025,7 @@ int main(int argc, char *argv[]) {
         test_filter_sets_ordered();
         test_restrict_namespace();
         test_protect_sysctl();
+        test_protect_syslog();
         test_restrict_address_families();
         test_restrict_realtime();
         test_memory_deny_write_execute_mmap();

test/meson.build

@@ -109,6 +109,8 @@ test_data_files = '''
         test-execute/exec-privatetmp-no.service
         test-execute/exec-privatetmp-yes.service
         test-execute/exec-protecthome-tmpfs-vs-protectsystem-strict.service
+        test-execute/exec-protectkernellogs-yes-capabilities.service
+        test-execute/exec-protectkernellogs-no-capabilities.service
         test-execute/exec-protectkernelmodules-no-capabilities.service
         test-execute/exec-protectkernelmodules-yes-capabilities.service
         test-execute/exec-protectkernelmodules-yes-mount-propagation.service

test/test-execute/exec-protectkernellogs-no-capabilities.service

@@ -0,0 +1,7 @@
+[Unit]
+Description=Test CAP_SYSLOG for ProtectKernelLogs=no
+
+[Service]
+ProtectKernelLogs=no
+ExecStart=/bin/sh -x -c 'capsh --print | grep cap_syslog'
+Type=oneshot

test/test-execute/exec-protectkernellogs-yes-capabilities.service

@@ -0,0 +1,7 @@
+[Unit]
+Description=Test CAP_SYSLOG for ProtectKernelLogs=yes
+
+[Service]
+ProtectKernelLogs=yes
+ExecStart=/bin/sh -x -c '! capsh --print | grep cap_syslog'
+Type=oneshot

units/systemd-coredump@.service.in

@@ -32,6 +32,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 RestrictAddressFamilies=AF_UNIX
 RestrictNamespaces=yes

units/systemd-hostnamed.service.in

@@ -27,6 +27,7 @@ ProtectControlGroups=yes
 ProtectHome=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 ReadWritePaths=/etc
 RestrictAddressFamilies=AF_UNIX

units/systemd-journal-gatewayd.service.in

@@ -24,6 +24,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
 RestrictNamespaces=yes
 RestrictRealtime=yes

units/systemd-journal-remote.service.in

@@ -26,6 +26,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
 RestrictNamespaces=yes

units/systemd-journal-upload.service.in

@@ -24,6 +24,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
 RestrictNamespaces=yes
 RestrictRealtime=yes

units/systemd-localed.service.in

@@ -28,6 +28,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 ReadWritePaths=/etc
 RestrictAddressFamilies=AF_UNIX

units/systemd-logind.service.in

@@ -41,6 +41,7 @@ ProtectControlGroups=yes
 ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 ReadWritePaths=/etc /run
 Restart=always

units/systemd-machined.service.in

@@ -24,6 +24,7 @@ LockPersonality=yes
 MemoryDenyWriteExecute=yes
 NoNewPrivileges=yes
 ProtectHostname=yes
+ProtectKernelLogs=yes
 RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
 RestrictRealtime=yes
 SystemCallArchitectures=native

units/systemd-networkd.service.in

@@ -29,6 +29,7 @@ NoNewPrivileges=yes
 ProtectControlGroups=yes
 ProtectHome=yes
 ProtectKernelModules=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 Restart=on-failure
 RestartSec=0

units/systemd-portabled.service.in

@@ -18,6 +18,7 @@ BusName=org.freedesktop.portable1
 CapabilityBoundingSet=CAP_KILL CAP_SYS_PTRACE CAP_SYS_ADMIN CAP_SETGID CAP_SYS_CHROOT CAP_DAC_READ_SEARCH CAP_DAC_OVERRIDE CAP_CHOWN CAP_FOWNER CAP_FSETID CAP_MKNOD
 MemoryDenyWriteExecute=yes
 ProtectHostname=yes
+ProtectKernelLogs=yes
 RestrictRealtime=yes
 RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
 SystemCallFilter=@system-service @mount

units/systemd-resolved.service.in

@@ -32,6 +32,7 @@ ProtectControlGroups=yes
 ProtectHome=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 Restart=always
 RestartSec=0

units/systemd-timedated.service.in

@@ -27,6 +27,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 ReadWritePaths=/etc
 RestrictAddressFamilies=AF_UNIX

units/systemd-timesyncd.service.in

@@ -32,6 +32,7 @@ ProtectHome=yes
 ProtectHostname=yes
 ProtectKernelModules=yes
 ProtectKernelTunables=yes
+ProtectKernelLogs=yes
 ProtectSystem=strict
 Restart=always
 RestartSec=0