init: if vendor_init can read a property, let it be a trigger too

There is a list of 'stable_properties' that vendor_init can use as
property triggers for Treble property compliance.  This list came about
since init parses init scripts before all partitions are mounted and
therefore before all property context files are available, such that
init cannot use the normal SELinux mechanisms for determining if a
given property is vendor_init readable.

Currently though, we require all partitions that would contain
property context files to be mounted during first stage mount, so we
can use the normal SELinux mechanisms here, so this change deprecates
the stable_properties list and moves init to use SELinux to determine
if a property can be a trigger.

Bug: 71814576
Test: vendor_init fails to use non-readable properties as a trigger
Test: vendor_init successfully uses readable properties as a trigger
Change-Id: I6a914e8c212a3418cbf4a8a07215056aad2e0162

init/action_parser.cpp

@@ -19,7 +19,11 @@
 #include <android-base/properties.h>
 #include <android-base/strings.h>
 
-#include "stable_properties.h"
+#if defined(__ANDROID__)
+#include "property_service.h"
+#else
+#include "host_init_stubs.h"
+#endif
 
 using android::base::GetBoolProperty;
 using android::base::StartsWith;
@@ -36,15 +40,7 @@ bool IsActionableProperty(Subcontext* subcontext, const std::string& prop_name)
         return true;
     }
 
-    if (kExportedActionableProperties.count(prop_name) == 1) {
-        return true;
-    }
-    for (const auto& prefix : kPartnerPrefixes) {
-        if (android::base::StartsWith(prop_name, prefix)) {
-            return true;
-        }
-    }
-    return false;
+    return CanReadProperty(subcontext->context(), prop_name);
 }
 
 Result<Success> ParsePropertyTrigger(const std::string& trigger, Subcontext* subcontext,

init/host_init_stubs.cpp

@@ -30,6 +30,9 @@ namespace init {
 std::string default_console = "/dev/console";
 
 // property_service.h
+bool CanReadProperty(const std::string& source_context, const std::string& name) {
+    return true;
+}
 uint32_t SetProperty(const std::string& key, const std::string& value) {
     android::base::SetProperty(key, value);
     return 0;

init/host_init_stubs.h

@@ -39,6 +39,7 @@ namespace init {
 extern std::string default_console;
 
 // property_service.h
+bool CanReadProperty(const std::string& source_context, const std::string& name);
 extern uint32_t (*property_set)(const std::string& name, const std::string& value);
 uint32_t HandlePropertySet(const std::string& name, const std::string& value,
                            const std::string& source_context, const ucred& cr, std::string* error);

init/property_service.cpp

@@ -111,6 +111,22 @@ void property_init() {
         LOG(FATAL) << "Failed to load serialized property info file";
     }
 }
+
+bool CanReadProperty(const std::string& source_context, const std::string& name) {
+    const char* target_context = nullptr;
+    property_info_area->GetPropertyInfo(name.c_str(), &target_context, nullptr);
+
+    PropertyAuditData audit_data;
+
+    audit_data.name = name.c_str();
+
+    ucred cr = {.pid = 0, .uid = 0, .gid = 0};
+    audit_data.cr = &cr;
+
+    return selinux_check_access(source_context.c_str(), target_context, "file", "read",
+                                &audit_data) == 0;
+}
+
 static bool CheckMacPerms(const std::string& name, const char* target_context,
                           const char* source_context, const ucred& cr) {
     if (!target_context || !source_context) {

init/property_service.h

@@ -26,6 +26,8 @@
 namespace android {
 namespace init {
 
+bool CanReadProperty(const std::string& source_context, const std::string& name);
+
 extern uint32_t (*property_set)(const std::string& name, const std::string& value);
 
 uint32_t HandlePropertySet(const std::string& name, const std::string& value,

init/stable_properties.h

@@ -1,67 +0,0 @@
-/*
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef _INIT_STABLE_PROPERTIES_H
-#define _INIT_STABLE_PROPERTIES_H
-
-#include <set>
-#include <string>
-
-namespace android {
-namespace init {
-
-static constexpr const char* kPartnerPrefixes[] = {
-    "init.svc.vendor.", "ro.vendor.", "persist.vendor.", "vendor.", "init.svc.odm.", "ro.odm.",
-    "persist.odm.",     "odm.",       "ro.boot.",
-};
-
-static const std::set<std::string> kExportedActionableProperties = {
-    "dev.bootcomplete",
-    "init.svc.console",
-    "init.svc.dumpstatez",
-    "init.svc.mediadrm",
-    "init.svc.surfaceflinger",
-    "init.svc.zygote",
-    "persist.bluetooth.btsnoopenable",
-    "persist.sys.crash_rcu",
-    "persist.sys.usb.usbradio.config",
-    "persist.sys.zram_enabled",
-    "ro.board.platform",
-    "ro.bootmode",
-    "ro.build.type",
-    "ro.crypto.state",
-    "ro.crypto.type",
-    "ro.debuggable",
-    "sys.boot_completed",
-    "sys.boot_from_charger_mode",
-    "sys.retaildemo.enabled",
-    "sys.shutdown.requested",
-    "sys.usb.config",
-    "sys.usb.configfs",
-    "sys.usb.ffs.mtp.ready",
-    "sys.usb.ffs.ready",
-    "sys.user.0.ce_available",
-    "sys.vdso",
-    "vold.decrypt",
-    "vold.post_fs_data_done",
-    "vts.native_server.on",
-    "wlan.driver.status",
-};
-
-}  // namespace init
-}  // namespace android
-
-#endif