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/*
* Copyright (C) 2020 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 "snapuserd_transition.h"
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/xattr.h>
#include <unistd.h>
#include <filesystem>
#include <string>
#include <string_view>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/parseint.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
#include <cutils/sockets.h>
#include <fs_avb/fs_avb.h>
#include <libsnapshot/snapshot.h>
#include <private/android_filesystem_config.h>
#include <procinfo/process_map.h>
#include <selinux/android.h>
#include <snapuserd/snapuserd_client.h>
#include "block_dev_initializer.h"
#include "service_utils.h"
#include "util.h"
namespace android {
namespace init {
using namespace std::string_literals;
using android::base::unique_fd;
using android::snapshot::SnapshotManager;
using android::snapshot::SnapuserdClient;
static constexpr char kSnapuserdPath[] = "/system/bin/snapuserd";
static constexpr char kSnapuserdFirstStagePidVar[] = "FIRST_STAGE_SNAPUSERD_PID";
static constexpr char kSnapuserdFirstStageFdVar[] = "FIRST_STAGE_SNAPUSERD_FD";
static constexpr char kSnapuserdFirstStageInfoVar[] = "FIRST_STAGE_SNAPUSERD_INFO";
static constexpr char kSnapuserdLabel[] = "u:object_r:snapuserd_exec:s0";
static constexpr char kSnapuserdSocketLabel[] = "u:object_r:snapuserd_socket:s0";
void LaunchFirstStageSnapuserd(SnapshotDriver driver) {
SocketDescriptor socket_desc;
socket_desc.name = android::snapshot::kSnapuserdSocket;
socket_desc.type = SOCK_STREAM;
socket_desc.perm = 0660;
socket_desc.uid = AID_SYSTEM;
socket_desc.gid = AID_SYSTEM;
// We specify a label here even though it technically is not needed. During
// first_stage_mount there is no sepolicy loaded. Once sepolicy is loaded,
// we bypass the socket entirely.
auto socket = socket_desc.Create(kSnapuserdSocketLabel);
if (!socket.ok()) {
LOG(FATAL) << "Could not create snapuserd socket: " << socket.error();
}
pid_t pid = fork();
if (pid < 0) {
PLOG(FATAL) << "Cannot launch snapuserd; fork failed";
}
if (pid == 0) {
socket->Publish();
if (driver == SnapshotDriver::DM_USER) {
char arg0[] = "/system/bin/snapuserd";
char arg1[] = "-user_snapshot";
char* const argv[] = {arg0, arg1, nullptr};
if (execv(arg0, argv) < 0) {
PLOG(FATAL) << "Cannot launch snapuserd; execv failed";
}
_exit(127);
} else {
char arg0[] = "/system/bin/snapuserd";
char* const argv[] = {arg0, nullptr};
if (execv(arg0, argv) < 0) {
PLOG(FATAL) << "Cannot launch snapuserd; execv failed";
}
_exit(127);
}
}
auto client = SnapuserdClient::Connect(android::snapshot::kSnapuserdSocket, 10s);
if (!client) {
LOG(FATAL) << "Could not connect to first-stage snapuserd";
}
if (client->SupportsSecondStageSocketHandoff()) {
setenv(kSnapuserdFirstStageInfoVar, "socket", 1);
}
setenv(kSnapuserdFirstStagePidVar, std::to_string(pid).c_str(), 1);
LOG(INFO) << "Relaunched snapuserd with pid: " << pid;
}
std::optional<pid_t> GetSnapuserdFirstStagePid() {
const char* pid_str = getenv(kSnapuserdFirstStagePidVar);
if (!pid_str) {
return {};
}
int pid = 0;
if (!android::base::ParseInt(pid_str, &pid)) {
LOG(FATAL) << "Could not parse pid in environment, " << kSnapuserdFirstStagePidVar << "="
<< pid_str;
}
return {pid};
}
static void RelabelLink(const std::string& link) {
selinux_android_restorecon(link.c_str(), 0);
std::string path;
if (android::base::Readlink(link, &path)) {
selinux_android_restorecon(path.c_str(), 0);
}
}
static void RelabelDeviceMapper() {
selinux_android_restorecon("/dev/device-mapper", 0);
std::error_code ec;
for (auto& iter : std::filesystem::directory_iterator("/dev/block", ec)) {
const auto& path = iter.path();
if (android::base::StartsWith(path.string(), "/dev/block/dm-")) {
selinux_android_restorecon(path.string().c_str(), 0);
}
}
}
static std::optional<int> GetRamdiskSnapuserdFd() {
const char* fd_str = getenv(kSnapuserdFirstStageFdVar);
if (!fd_str) {
return {};
}
int fd;
if (!android::base::ParseInt(fd_str, &fd)) {
LOG(FATAL) << "Could not parse fd in environment, " << kSnapuserdFirstStageFdVar << "="
<< fd_str;
}
return {fd};
}
void RestoreconRamdiskSnapuserd(int fd) {
if (fsetxattr(fd, XATTR_NAME_SELINUX, kSnapuserdLabel, strlen(kSnapuserdLabel) + 1, 0) < 0) {
PLOG(FATAL) << "fsetxattr snapuserd failed";
}
}
SnapuserdSelinuxHelper::SnapuserdSelinuxHelper(std::unique_ptr<SnapshotManager>&& sm, pid_t old_pid)
: sm_(std::move(sm)), old_pid_(old_pid) {
// Only dm-user device names change during transitions, so the other
// devices are expected to be present.
sm_->SetUeventRegenCallback([this](const std::string& device) -> bool {
if (android::base::StartsWith(device, "/dev/dm-user/")) {
return block_dev_init_.InitDmUser(android::base::Basename(device));
}
return true;
});
}
static void LockAllSystemPages() {
bool ok = true;
auto callback = [&](const android::procinfo::MapInfo& map) -> void {
if (!ok || android::base::StartsWith(map.name, "/dev/") ||
!android::base::StartsWith(map.name, "/")) {
return;
}
auto start = reinterpret_cast<const void*>(map.start);
auto len = map.end - map.start;
if (!len) {
return;
}
if (mlock(start, len) < 0) {
LOG(ERROR) << "mlock failed, " << start << " for " << len << " bytes.";
ok = false;
}
};
if (!android::procinfo::ReadProcessMaps(getpid(), callback) || !ok) {
LOG(FATAL) << "Could not process /proc/" << getpid() << "/maps file for init, "
<< "falling back to mlockall().";
if (mlockall(MCL_CURRENT) < 0) {
LOG(FATAL) << "mlockall failed";
}
}
}
void SnapuserdSelinuxHelper::StartTransition() {
LOG(INFO) << "Starting SELinux transition of snapuserd";
// The restorecon path reads from /system etc, so make sure any reads have
// been cached before proceeding.
auto handle = selinux_android_file_context_handle();
if (!handle) {
LOG(FATAL) << "Could not create SELinux file context handle";
}
selinux_android_set_sehandle(handle);
// We cannot access /system after the transition, so make sure init is
// pinned in memory.
LockAllSystemPages();
argv_.emplace_back("snapuserd");
argv_.emplace_back("-no_socket");
if (!sm_->DetachSnapuserdForSelinux(&argv_)) {
LOG(FATAL) << "Could not perform selinux transition";
}
// Make sure the process is gone so we don't have any selinux audits.
KillFirstStageSnapuserd(old_pid_);
}
void SnapuserdSelinuxHelper::FinishTransition() {
RelabelLink("/dev/block/by-name/super");
RelabelDeviceMapper();
selinux_android_restorecon("/dev/null", 0);
selinux_android_restorecon("/dev/urandom", 0);
selinux_android_restorecon("/dev/kmsg", 0);
selinux_android_restorecon("/dev/dm-user", SELINUX_ANDROID_RESTORECON_RECURSE);
RelaunchFirstStageSnapuserd();
if (munlockall() < 0) {
PLOG(ERROR) << "munlockall failed";
}
}
/*
* Before starting init second stage, we will wait
* for snapuserd daemon to be up and running; bionic libc
* may read /system/etc/selinux/plat_property_contexts file
* before invoking main() function. This will happen if
* init initializes property during second stage. Any access
* to /system without snapuserd daemon will lead to a deadlock.
*
* Thus, we do a simple probe by reading system partition. This
* read will eventually be serviced by daemon confirming that
* daemon is up and running. Furthermore, we are still in the kernel
* domain and sepolicy has not been enforced yet. Thus, access
* to these device mapper block devices are ok even though
* we may see audit logs.
*/
bool SnapuserdSelinuxHelper::TestSnapuserdIsReady() {
std::string dev = "/dev/block/mapper/system"s + fs_mgr_get_slot_suffix();
android::base::unique_fd fd(open(dev.c_str(), O_RDONLY | O_DIRECT));
if (fd < 0) {
PLOG(ERROR) << "open " << dev << " failed";
return false;
}
void* addr;
ssize_t page_size = getpagesize();
if (posix_memalign(&addr, page_size, page_size) < 0) {
PLOG(ERROR) << "posix_memalign with page size " << page_size;
return false;
}
std::unique_ptr<void, decltype(&::free)> buffer(addr, ::free);
int iter = 0;
while (iter < 10) {
ssize_t n = TEMP_FAILURE_RETRY(pread(fd.get(), buffer.get(), page_size, 0));
if (n < 0) {
// Wait for sometime before retry
std::this_thread::sleep_for(100ms);
} else if (n == page_size) {
return true;
} else {
LOG(ERROR) << "pread returned: " << n << " from: " << dev << " expected: " << page_size;
}
iter += 1;
}
return false;
}
void SnapuserdSelinuxHelper::RelaunchFirstStageSnapuserd() {
auto fd = GetRamdiskSnapuserdFd();
if (!fd) {
LOG(FATAL) << "Environment variable " << kSnapuserdFirstStageFdVar << " was not set!";
}
unsetenv(kSnapuserdFirstStageFdVar);
RestoreconRamdiskSnapuserd(fd.value());
pid_t pid = fork();
if (pid < 0) {
PLOG(FATAL) << "Fork to relaunch snapuserd failed";
}
if (pid > 0) {
// We don't need the descriptor anymore, and it should be closed to
// avoid leaking into subprocesses.
close(fd.value());
setenv(kSnapuserdFirstStagePidVar, std::to_string(pid).c_str(), 1);
LOG(INFO) << "Relaunched snapuserd with pid: " << pid;
if (!TestSnapuserdIsReady()) {
PLOG(FATAL) << "snapuserd daemon failed to launch";
} else {
LOG(INFO) << "snapuserd daemon is up and running";
}
return;
}
// Make sure the descriptor is gone after we exec.
if (fcntl(fd.value(), F_SETFD, FD_CLOEXEC) < 0) {
PLOG(FATAL) << "fcntl FD_CLOEXEC failed for snapuserd fd";
}
std::vector<char*> argv;
for (auto& arg : argv_) {
argv.emplace_back(arg.data());
}
argv.emplace_back(nullptr);
int rv = syscall(SYS_execveat, fd.value(), "", reinterpret_cast<char* const*>(argv.data()),
nullptr, AT_EMPTY_PATH);
if (rv < 0) {
PLOG(FATAL) << "Failed to execveat() snapuserd";
}
}
std::unique_ptr<SnapuserdSelinuxHelper> SnapuserdSelinuxHelper::CreateIfNeeded() {
if (IsRecoveryMode()) {
return nullptr;
}
auto old_pid = GetSnapuserdFirstStagePid();
if (!old_pid) {
return nullptr;
}
auto sm = SnapshotManager::NewForFirstStageMount();
if (!sm) {
LOG(FATAL) << "Unable to create SnapshotManager";
}
return std::make_unique<SnapuserdSelinuxHelper>(std::move(sm), old_pid.value());
}
void KillFirstStageSnapuserd(pid_t pid) {
if (kill(pid, SIGTERM) < 0 && errno != ESRCH) {
LOG(ERROR) << "Kill snapuserd pid failed: " << pid;
} else {
LOG(INFO) << "Sent SIGTERM to snapuserd process " << pid;
}
}
void CleanupSnapuserdSocket() {
auto socket_path = ANDROID_SOCKET_DIR "/"s + android::snapshot::kSnapuserdSocket;
if (access(socket_path.c_str(), F_OK) != 0) {
return;
}
// Tell the daemon to stop accepting connections and to gracefully exit
// once all outstanding handlers have terminated.
if (auto client = SnapuserdClient::Connect(android::snapshot::kSnapuserdSocket, 3s)) {
client->DetachSnapuserd();
}
// Unlink the socket so we can create it again in second-stage.
if (unlink(socket_path.c_str()) < 0) {
PLOG(FATAL) << "unlink " << socket_path << " failed";
}
}
void SaveRamdiskPathToSnapuserd() {
int fd = open(kSnapuserdPath, O_PATH);
if (fd < 0) {
PLOG(FATAL) << "Unable to open snapuserd: " << kSnapuserdPath;
}
auto value = std::to_string(fd);
if (setenv(kSnapuserdFirstStageFdVar, value.c_str(), 1) < 0) {
PLOG(FATAL) << "setenv failed: " << kSnapuserdFirstStageFdVar << "=" << value;
}
}
bool IsFirstStageSnapuserdRunning() {
return GetSnapuserdFirstStagePid().has_value();
}
std::vector<std::string> GetSnapuserdFirstStageInfo() {
const char* pid_str = getenv(kSnapuserdFirstStageInfoVar);
if (!pid_str) {
return {};
}
return android::base::Split(pid_str, ",");
}
} // namespace init
} // namespace android