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/*
* 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.
*/
#include "subcontext.h"
#include <fcntl.h>
#include <poll.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <unistd.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/strings.h>
#include <selinux/android.h>
#include "action.h"
#include "builtins.h"
#include "mount_namespace.h"
#include "proto_utils.h"
#include "util.h"
#ifdef INIT_FULL_SOURCES
#include <android/api-level.h>
#include "property_service.h"
#include "selabel.h"
#include "selinux.h"
#else
#include "host_init_stubs.h"
#endif
using android::base::GetExecutablePath;
using android::base::GetProperty;
using android::base::Join;
using android::base::Socketpair;
using android::base::Split;
using android::base::StartsWith;
using android::base::unique_fd;
namespace android {
namespace init {
namespace {
std::string shutdown_command;
static bool subcontext_terminated_by_shutdown;
static std::unique_ptr<Subcontext> subcontext;
class SubcontextProcess {
public:
SubcontextProcess(const BuiltinFunctionMap* function_map, std::string context, int init_fd)
: function_map_(function_map), context_(std::move(context)), init_fd_(init_fd){};
void MainLoop();
private:
void RunCommand(const SubcontextCommand::ExecuteCommand& execute_command,
SubcontextReply* reply) const;
void ExpandArgs(const SubcontextCommand::ExpandArgsCommand& expand_args_command,
SubcontextReply* reply) const;
const BuiltinFunctionMap* function_map_;
const std::string context_;
const int init_fd_;
};
void SubcontextProcess::RunCommand(const SubcontextCommand::ExecuteCommand& execute_command,
SubcontextReply* reply) const {
// Need to use ArraySplice instead of this code.
auto args = std::vector<std::string>();
for (const auto& string : execute_command.args()) {
args.emplace_back(string);
}
auto map_result = function_map_->Find(args);
Result<void> result;
if (!map_result.ok()) {
result = Error() << "Cannot find command: " << map_result.error();
} else {
result = RunBuiltinFunction(map_result->function, args, context_);
}
if (result.ok()) {
reply->set_success(true);
} else {
auto* failure = reply->mutable_failure();
failure->set_error_string(result.error().message());
failure->set_error_errno(result.error().code());
}
}
void SubcontextProcess::ExpandArgs(const SubcontextCommand::ExpandArgsCommand& expand_args_command,
SubcontextReply* reply) const {
for (const auto& arg : expand_args_command.args()) {
auto expanded_arg = ExpandProps(arg);
if (!expanded_arg.ok()) {
auto* failure = reply->mutable_failure();
failure->set_error_string(expanded_arg.error().message());
failure->set_error_errno(0);
return;
} else {
auto* expand_args_reply = reply->mutable_expand_args_reply();
expand_args_reply->add_expanded_args(*expanded_arg);
}
}
}
void SubcontextProcess::MainLoop() {
pollfd ufd[1];
ufd[0].events = POLLIN;
ufd[0].fd = init_fd_;
while (true) {
ufd[0].revents = 0;
int nr = TEMP_FAILURE_RETRY(poll(ufd, arraysize(ufd), -1));
if (nr == 0) continue;
if (nr < 0) {
PLOG(FATAL) << "poll() of subcontext socket failed, continuing";
}
auto init_message = ReadMessage(init_fd_);
if (!init_message.ok()) {
if (init_message.error().code() == 0) {
// If the init file descriptor was closed, let's exit quietly. If
// this was accidental, init will restart us. If init died, this
// avoids calling abort(3) unnecessarily.
return;
}
LOG(FATAL) << "Could not read message from init: " << init_message.error();
}
auto subcontext_command = SubcontextCommand();
if (!subcontext_command.ParseFromString(*init_message)) {
LOG(FATAL) << "Unable to parse message from init";
}
auto reply = SubcontextReply();
switch (subcontext_command.command_case()) {
case SubcontextCommand::kExecuteCommand: {
RunCommand(subcontext_command.execute_command(), &reply);
break;
}
case SubcontextCommand::kExpandArgsCommand: {
ExpandArgs(subcontext_command.expand_args_command(), &reply);
break;
}
default:
LOG(FATAL) << "Unknown message type from init: "
<< subcontext_command.command_case();
}
if (!shutdown_command.empty()) {
reply.set_trigger_shutdown(shutdown_command);
shutdown_command.clear();
}
if (auto result = SendMessage(init_fd_, reply); !result.ok()) {
LOG(FATAL) << "Failed to send message to init: " << result.error();
}
}
}
} // namespace
int SubcontextMain(int argc, char** argv, const BuiltinFunctionMap* function_map) {
if (argc < 4) LOG(FATAL) << "Fewer than 4 args specified to subcontext (" << argc << ")";
auto context = std::string(argv[2]);
auto init_fd = std::atoi(argv[3]);
SelabelInitialize();
trigger_shutdown = [](const std::string& command) { shutdown_command = command; };
auto subcontext_process = SubcontextProcess(function_map, context, init_fd);
// Restore prio before main loop
setpriority(PRIO_PROCESS, 0, 0);
subcontext_process.MainLoop();
return 0;
}
void Subcontext::Fork() {
unique_fd subcontext_socket;
if (!Socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0, &socket_, &subcontext_socket)) {
LOG(FATAL) << "Could not create socket pair to communicate to subcontext";
return;
}
auto result = fork();
if (result == -1) {
LOG(FATAL) << "Could not fork subcontext";
} else if (result == 0) {
socket_.reset();
// We explicitly do not use O_CLOEXEC here, such that we can reference this FD by number
// in the subcontext process after we exec.
int child_fd = dup(subcontext_socket); // NOLINT(android-cloexec-dup)
if (child_fd < 0) {
PLOG(FATAL) << "Could not dup child_fd";
}
// We don't switch contexts if we're running the unit tests. We don't use std::optional,
// since we still need a real context string to pass to the builtin functions.
if (context_ != kTestContext) {
if (setexeccon(context_.c_str()) < 0) {
PLOG(FATAL) << "Could not set execcon for '" << context_ << "'";
}
}
#if defined(__ANDROID__)
// subcontext init runs in "default" mount namespace
// so that it can access /apex/*
if (auto result = SwitchToMountNamespaceIfNeeded(NS_DEFAULT); !result.ok()) {
LOG(FATAL) << "Could not switch to \"default\" mount namespace: " << result.error();
}
#endif
auto init_path = GetExecutablePath();
auto child_fd_string = std::to_string(child_fd);
const char* args[] = {init_path.c_str(), "subcontext", context_.c_str(),
child_fd_string.c_str(), nullptr};
execv(init_path.data(), const_cast<char**>(args));
PLOG(FATAL) << "Could not execv subcontext init";
} else {
subcontext_socket.reset();
pid_ = result;
LOG(INFO) << "Forked subcontext for '" << context_ << "' with pid " << pid_;
}
}
void Subcontext::Restart() {
LOG(ERROR) << "Restarting subcontext '" << context_ << "'";
if (pid_) {
kill(pid_, SIGKILL);
}
pid_ = 0;
socket_.reset();
Fork();
}
bool Subcontext::PathMatchesSubcontext(const std::string& path) {
for (const auto& prefix : path_prefixes_) {
if (StartsWith(path, prefix)) {
return true;
}
}
return false;
}
Result<SubcontextReply> Subcontext::TransmitMessage(const SubcontextCommand& subcontext_command) {
if (auto result = SendMessage(socket_, subcontext_command); !result.ok()) {
Restart();
return ErrnoError() << "Failed to send message to subcontext";
}
auto subcontext_message = ReadMessage(socket_);
if (!subcontext_message.ok()) {
Restart();
return Error() << "Failed to receive result from subcontext: " << subcontext_message.error();
}
auto subcontext_reply = SubcontextReply{};
if (!subcontext_reply.ParseFromString(*subcontext_message)) {
Restart();
return Error() << "Unable to parse message from subcontext";
}
if (subcontext_reply.has_trigger_shutdown()) {
trigger_shutdown(subcontext_reply.trigger_shutdown());
}
return subcontext_reply;
}
Result<void> Subcontext::Execute(const std::vector<std::string>& args) {
auto subcontext_command = SubcontextCommand();
std::copy(
args.begin(), args.end(),
RepeatedPtrFieldBackInserter(subcontext_command.mutable_execute_command()->mutable_args()));
auto subcontext_reply = TransmitMessage(subcontext_command);
if (!subcontext_reply.ok()) {
return subcontext_reply.error();
}
if (subcontext_reply->reply_case() == SubcontextReply::kFailure) {
auto& failure = subcontext_reply->failure();
return ResultError<>(failure.error_string(), failure.error_errno());
}
if (subcontext_reply->reply_case() != SubcontextReply::kSuccess) {
return Error() << "Unexpected message type from subcontext: "
<< subcontext_reply->reply_case();
}
return {};
}
Result<std::vector<std::string>> Subcontext::ExpandArgs(const std::vector<std::string>& args) {
auto subcontext_command = SubcontextCommand{};
std::copy(args.begin(), args.end(),
RepeatedPtrFieldBackInserter(
subcontext_command.mutable_expand_args_command()->mutable_args()));
auto subcontext_reply = TransmitMessage(subcontext_command);
if (!subcontext_reply.ok()) {
return subcontext_reply.error();
}
if (subcontext_reply->reply_case() == SubcontextReply::kFailure) {
auto& failure = subcontext_reply->failure();
return ResultError<>(failure.error_string(), failure.error_errno());
}
if (subcontext_reply->reply_case() != SubcontextReply::kExpandArgsReply) {
return Error() << "Unexpected message type from subcontext: "
<< subcontext_reply->reply_case();
}
auto& reply = subcontext_reply->expand_args_reply();
auto expanded_args = std::vector<std::string>{};
for (const auto& string : reply.expanded_args()) {
expanded_args.emplace_back(string);
}
return expanded_args;
}
void InitializeSubcontext() {
if (IsMicrodroid()) {
LOG(INFO) << "Not using subcontext for microdroid";
return;
}
if (SelinuxGetVendorAndroidVersion() >= __ANDROID_API_P__) {
subcontext.reset(
new Subcontext(std::vector<std::string>{"/vendor", "/odm"}, kVendorContext));
}
}
void InitializeHostSubcontext(std::vector<std::string> vendor_prefixes) {
subcontext.reset(new Subcontext(vendor_prefixes, kVendorContext, /*host=*/true));
}
Subcontext* GetSubcontext() {
return subcontext.get();
}
bool SubcontextChildReap(pid_t pid) {
if (!subcontext) {
return false;
}
if (subcontext->pid() == pid) {
if (!subcontext_terminated_by_shutdown) {
subcontext->Restart();
}
return true;
}
return false;
}
void SubcontextTerminate() {
subcontext_terminated_by_shutdown = true;
kill(subcontext->pid(), SIGTERM);
}
} // namespace init
} // namespace android