init: run vendor commands in a separate SELinux context
One of the major aspects of treble is the compartmentalization of system
and vendor components, however init leaves a huge gap here, as vendor
init scripts run in the same context as system init scripts and thus can
access and modify the same properties, files, etc as the system can.
This change is meant to close that gap. It forks a separate 'subcontext'
init that runs in a different SELinux context with permissions that match
what vendors should have access to. Commands get sent over a socket to
this 'subcontext' init that then runs them in this SELinux context and
returns the result.
Note that not all commands run in the subcontext; some commands such as
those dealing with services only make sense in the context of the main
init process.
Bug: 62875318
Test: init unit tests, boot bullhead, boot sailfish
Change-Id: Idf4a4ebf98842d27b8627f901f961ab9eb412aee
diff --git a/init/subcontext.h b/init/subcontext.h
new file mode 100644
index 0000000..ac77e08
--- /dev/null
+++ b/init/subcontext.h
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2017 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_SUBCONTEXT_H
+#define _INIT_SUBCONTEXT_H
+
+#include <signal.h>
+
+#include <string>
+#include <vector>
+
+#include <android-base/unique_fd.h>
+
+#include "builtins.h"
+
+namespace android {
+namespace init {
+
+extern const std::string kInitContext;
+extern const std::string kVendorContext;
+
+class Subcontext {
+ public:
+ Subcontext(std::string path_prefix, std::string context)
+ : path_prefix_(path_prefix), context_(std::move(context)) {
+ Fork();
+ }
+
+ Result<Success> Execute(const std::vector<std::string>& command);
+ void Restart();
+
+ const std::string& path_prefix() const { return path_prefix_; }
+ const std::string& context() const { return context_; }
+ pid_t pid() const { return pid_; }
+
+ private:
+ void Fork();
+
+ std::string path_prefix_;
+ std::string context_;
+ pid_t pid_;
+ android::base::unique_fd socket_;
+};
+
+// For testing, to kill the subcontext after the test has completed.
+class SubcontextKiller {
+ public:
+ SubcontextKiller(const Subcontext& subcontext) : subcontext_(subcontext) {}
+ ~SubcontextKiller() {
+ if (subcontext_.pid() > 0) {
+ kill(subcontext_.pid(), SIGTERM);
+ kill(subcontext_.pid(), SIGKILL);
+ }
+ }
+
+ private:
+ const Subcontext& subcontext_;
+};
+
+int SubcontextMain(int argc, char** argv, const KeywordFunctionMap* function_map);
+std::vector<Subcontext>* InitializeSubcontexts();
+bool SubcontextChildReap(pid_t pid);
+
+} // namespace init
+} // namespace android
+
+#endif