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From f79283a86531e3bbf0854b5f126b7b291fadfb43 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Wed, 20 Mar 2019 19:09:09 +0100
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Subject: [PATCH] core: expose SUID/SGID restriction as new unit setting
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 RestrictSUIDSGID=
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(cherry picked from commit f69567cbe26d09eac9d387c0be0fc32c65a83ada)
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Related: #1687512
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---
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 src/core/dbus-execute.c                     |  4 ++++
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 src/core/execute.c                          | 22 +++++++++++++++++++++
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 src/core/execute.h                          |  1 +
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 src/core/load-fragment-gperf.gperf.m4       |  2 ++
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 src/shared/bus-unit-util.c                  |  2 +-
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 test/fuzz/fuzz-unit-file/directives.service |  1 +
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 6 files changed, 31 insertions(+), 1 deletion(-)
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diff --git a/src/core/dbus-execute.c b/src/core/dbus-execute.c
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index 198f149210..e7c0b893d1 100644
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--- a/src/core/dbus-execute.c
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+++ b/src/core/dbus-execute.c
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@@ -815,6 +815,7 @@ const sd_bus_vtable bus_exec_vtable[] = {
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         SD_BUS_PROPERTY("ConfigurationDirectory", "as", NULL, offsetof(ExecContext, directories[EXEC_DIRECTORY_CONFIGURATION].paths), SD_BUS_VTABLE_PROPERTY_CONST),
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         SD_BUS_PROPERTY("MemoryDenyWriteExecute", "b", bus_property_get_bool, offsetof(ExecContext, memory_deny_write_execute), SD_BUS_VTABLE_PROPERTY_CONST),
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         SD_BUS_PROPERTY("RestrictRealtime", "b", bus_property_get_bool, offsetof(ExecContext, restrict_realtime), SD_BUS_VTABLE_PROPERTY_CONST),
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+        SD_BUS_PROPERTY("RestrictSUIDSGID", "b", bus_property_get_bool, offsetof(ExecContext, restrict_suid_sgid), SD_BUS_VTABLE_PROPERTY_CONST),
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         SD_BUS_PROPERTY("RestrictNamespaces", "t", bus_property_get_ulong, offsetof(ExecContext, restrict_namespaces), SD_BUS_VTABLE_PROPERTY_CONST),
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         SD_BUS_PROPERTY("BindPaths", "a(ssbt)", property_get_bind_paths, 0, SD_BUS_VTABLE_PROPERTY_CONST),
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         SD_BUS_PROPERTY("BindReadOnlyPaths", "a(ssbt)", property_get_bind_paths, 0, SD_BUS_VTABLE_PROPERTY_CONST),
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@@ -1179,6 +1180,9 @@ int bus_exec_context_set_transient_property(
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         if (streq(name, "RestrictRealtime"))
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                 return bus_set_transient_bool(u, name, &c->restrict_realtime, message, flags, error);
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+        if (streq(name, "RestrictSUIDSGID"))
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+                return bus_set_transient_bool(u, name, &c->restrict_suid_sgid, message, flags, error);
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+
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         if (streq(name, "DynamicUser"))
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                 return bus_set_transient_bool(u, name, &c->dynamic_user, message, flags, error);
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diff --git a/src/core/execute.c b/src/core/execute.c
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index 56aa89e1ec..f012023224 100644
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--- a/src/core/execute.c
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+++ b/src/core/execute.c
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@@ -1366,6 +1366,7 @@ static bool context_has_no_new_privileges(const ExecContext *c) {
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         return context_has_address_families(c) ||
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                 c->memory_deny_write_execute ||
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                 c->restrict_realtime ||
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+                c->restrict_suid_sgid ||
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                 exec_context_restrict_namespaces_set(c) ||
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                 c->protect_kernel_tunables ||
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                 c->protect_kernel_modules ||
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@@ -1470,6 +1471,19 @@ static int apply_restrict_realtime(const Unit* u, const ExecContext *c) {
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         return seccomp_restrict_realtime();
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 }
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+static int apply_restrict_suid_sgid(const Unit* u, const ExecContext *c) {
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+        assert(u);
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+        assert(c);
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+
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+        if (!c->restrict_suid_sgid)
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+                return 0;
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+
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+        if (skip_seccomp_unavailable(u, "RestrictSUIDSGID="))
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+                return 0;
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+
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+        return seccomp_restrict_suid_sgid();
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+}
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+
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 static int apply_protect_sysctl(const Unit *u, const ExecContext *c) {
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         assert(u);
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         assert(c);
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@@ -3404,6 +3418,12 @@ static int exec_child(
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                         return log_unit_error_errno(unit, r, "Failed to apply realtime restrictions: %m");
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                 }
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+                r = apply_restrict_suid_sgid(unit, context);
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+                if (r < 0) {
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+                        *exit_status = EXIT_SECCOMP;
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+                        return log_unit_error_errno(unit, r, "Failed to apply SUID/SGID restrictions: %m");
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+                }
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+
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                 r = apply_restrict_namespaces(unit, context);
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                 if (r < 0) {
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                         *exit_status = EXIT_SECCOMP;
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@@ -4023,6 +4043,7 @@ void exec_context_dump(const ExecContext *c, FILE* f, const char *prefix) {
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                 "%sIgnoreSIGPIPE: %s\n"
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                 "%sMemoryDenyWriteExecute: %s\n"
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                 "%sRestrictRealtime: %s\n"
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+                "%sRestrictSUIDSGID: %s\n"
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                 "%sKeyringMode: %s\n",
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                 prefix, c->umask,
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                 prefix, c->working_directory ? c->working_directory : "/",
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@@ -4041,6 +4062,7 @@ void exec_context_dump(const ExecContext *c, FILE* f, const char *prefix) {
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                 prefix, yes_no(c->ignore_sigpipe),
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                 prefix, yes_no(c->memory_deny_write_execute),
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                 prefix, yes_no(c->restrict_realtime),
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+                prefix, yes_no(c->restrict_suid_sgid),
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                 prefix, exec_keyring_mode_to_string(c->keyring_mode));
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         if (c->root_image)
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diff --git a/src/core/execute.h b/src/core/execute.h
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index b2eb55f8f5..2266355962 100644
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--- a/src/core/execute.h
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+++ b/src/core/execute.h
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@@ -245,6 +245,7 @@ struct ExecContext {
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          * that the autofs logic detects that it belongs to us and we
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          * don't enter a trigger loop. */
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         bool same_pgrp;
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+        bool restrict_suid_sgid;
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         unsigned long personality;
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         bool lock_personality;
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diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
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index cdf4d14c4e..49e938d0ce 100644
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--- a/src/core/load-fragment-gperf.gperf.m4
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+++ b/src/core/load-fragment-gperf.gperf.m4
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@@ -76,6 +76,7 @@ $1.SystemCallErrorNumber,        config_parse_syscall_errno,         0,
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 $1.MemoryDenyWriteExecute,       config_parse_bool,                  0,                             offsetof($1, exec_context.memory_deny_write_execute)
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 $1.RestrictNamespaces,           config_parse_restrict_namespaces,   0,                             offsetof($1, exec_context)
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 $1.RestrictRealtime,             config_parse_bool,                  0,                             offsetof($1, exec_context.restrict_realtime)
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+$1.RestrictSUIDSGID,             config_parse_bool,                  0,                             offsetof($1, exec_context.restrict_suid_sgid)
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 $1.RestrictAddressFamilies,      config_parse_address_families,      0,                             offsetof($1, exec_context)
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 $1.LockPersonality,              config_parse_bool,                  0,                             offsetof($1, exec_context.lock_personality)',
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 `$1.SystemCallFilter,            config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
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@@ -84,6 +85,7 @@ $1.SystemCallErrorNumber,        config_parse_warn_compat,           DISABLED_CO
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 $1.MemoryDenyWriteExecute,       config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
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 $1.RestrictNamespaces,           config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
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 $1.RestrictRealtime,             config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
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+$1.RestrictSUIDSGID,             config_parse_warn_compat,           DISABLED_CONFIGURATION         0
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 $1.RestrictAddressFamilies,      config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
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 $1.LockPersonality,              config_parse_warn_compat,           DISABLED_CONFIGURATION,        0')
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 $1.LimitCPU,                     config_parse_rlimit,                RLIMIT_CPU,                    offsetof($1, exec_context.rlimit)
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diff --git a/src/shared/bus-unit-util.c b/src/shared/bus-unit-util.c
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index 055edd6e22..3c42e97b7a 100644
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--- a/src/shared/bus-unit-util.c
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+++ b/src/shared/bus-unit-util.c
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@@ -697,7 +697,7 @@ static int bus_append_execute_property(sd_bus_message *m, const char *field, con
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                        "PrivateMounts", "NoNewPrivileges", "SyslogLevelPrefix",
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                        "MemoryDenyWriteExecute", "RestrictRealtime", "DynamicUser", "RemoveIPC",
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                        "ProtectKernelTunables", "ProtectKernelModules", "ProtectControlGroups",
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-                       "MountAPIVFS", "CPUSchedulingResetOnFork", "LockPersonality"))
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+                       "MountAPIVFS", "CPUSchedulingResetOnFork", "LockPersonality" "RestrictSUIDSGID"))
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                 return bus_append_parse_boolean(m, field, eq);
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diff --git a/test/fuzz/fuzz-unit-file/directives.service b/test/fuzz/fuzz-unit-file/directives.service
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index d8d1fc68b8..eab1820e20 100644
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--- a/test/fuzz/fuzz-unit-file/directives.service
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+++ b/test/fuzz/fuzz-unit-file/directives.service
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@@ -849,6 +849,7 @@ ReserveVT=
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 RestrictAddressFamilies=
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 RestrictNamespaces=
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 RestrictRealtime=
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+RestrictSUIDSGID=
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 RuntimeDirectory=
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 RuntimeDirectoryMode=
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 RuntimeDirectoryPreserve=