mirror of
https://github.com/google/sandboxed-api.git
synced 2024-03-22 13:11:30 +08:00
314 lines
9.7 KiB
C++
314 lines
9.7 KiB
C++
// Copyright 2019 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Implementation of the sandbox2::ForkServer class.
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#include "sandboxed_api/sandbox2/global_forkclient.h"
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#include <fcntl.h>
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#include <sys/prctl.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <syscall.h>
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#include <unistd.h>
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#include <csignal>
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#include <cstdlib>
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#include <string>
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#include <vector>
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#include <glog/logging.h>
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#include "sandboxed_api/util/flag.h"
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#include "absl/memory/memory.h"
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#include "absl/status/status.h"
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#include "absl/status/statusor.h"
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#include "absl/strings/ascii.h"
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#include "absl/strings/str_cat.h"
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#include "absl/strings/str_join.h"
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#include "absl/strings/str_split.h"
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#include "absl/strings/string_view.h"
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#include "absl/synchronization/mutex.h"
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#include "sandboxed_api/config.h"
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#include "sandboxed_api/embed_file.h"
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#include "sandboxed_api/sandbox2/comms.h"
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#include "sandboxed_api/sandbox2/fork_client.h"
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#include "sandboxed_api/sandbox2/forkserver_bin_embed.h"
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#include "sandboxed_api/sandbox2/util.h"
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#include "sandboxed_api/util/fileops.h"
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#include "sandboxed_api/util/os_error.h"
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#include "sandboxed_api/util/raw_logging.h"
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#include "sandboxed_api/util/status_macros.h"
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namespace sandbox2 {
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namespace file_util = ::sapi::file_util;
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bool AbslParseFlag(absl::string_view text, GlobalForkserverStartModeSet* out,
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std::string* error) {
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*out = {};
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if (text == "never") {
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return true;
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}
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for (absl::string_view mode : absl::StrSplit(text, ',')) {
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mode = absl::StripAsciiWhitespace(mode);
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if (mode == "ondemand") {
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*out |= GlobalForkserverStartMode::kOnDemand;
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} else {
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*error = absl::StrCat("Invalid forkserver start mode: ", mode);
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return false;
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}
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}
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return true;
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}
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namespace {
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std::string ToString(GlobalForkserverStartMode mode) {
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switch (mode) {
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case GlobalForkserverStartMode::kOnDemand:
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return "ondemand";
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default:
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return "unknown";
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}
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}
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bool ValidateStartMode(const char*, const std::string& flag) {
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GlobalForkserverStartModeSet unused;
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std::string error;
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if (!AbslParseFlag(flag, &unused, &error)) {
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SAPI_RAW_LOG(ERROR, "%s", error.c_str());
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return false;
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}
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return true;
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}
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} // namespace
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std::string AbslUnparseFlag(GlobalForkserverStartModeSet in) {
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std::vector<std::string> str_modes;
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for (size_t i = 0; i < GlobalForkserverStartModeSet::kSize; ++i) {
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auto mode = static_cast<GlobalForkserverStartMode>(i);
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if (in.contains(mode)) {
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str_modes.push_back(ToString(mode));
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}
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}
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if (str_modes.empty()) {
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return "never";
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}
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return absl::StrJoin(str_modes, ",");
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}
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} // namespace sandbox2
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ABSL_FLAG(string, sandbox2_forkserver_binary_path, "",
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"Path to forkserver_bin binary");
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ABSL_FLAG(string, sandbox2_forkserver_start_mode, "ondemand",
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"When Sandbox2 Forkserver process should be started");
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DEFINE_validator(sandbox2_forkserver_start_mode, &sandbox2::ValidateStartMode);
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namespace sandbox2 {
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namespace {
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GlobalForkserverStartModeSet GetForkserverStartMode() {
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GlobalForkserverStartModeSet rv;
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std::string error;
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CHECK(AbslParseFlag(absl::GetFlag(FLAGS_sandbox2_forkserver_start_mode), &rv,
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&error));
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return rv;
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}
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absl::StatusOr<std::unique_ptr<GlobalForkClient>> StartGlobalForkServer() {
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SAPI_RAW_LOG(INFO, "Starting global forkserver");
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// Allow passing of a spearate forkserver_bin via flag
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int exec_fd = -1;
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if (!absl::GetFlag(FLAGS_sandbox2_forkserver_binary_path).empty()) {
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exec_fd = open(absl::GetFlag(FLAGS_sandbox2_forkserver_binary_path).c_str(),
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O_RDONLY);
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}
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if (exec_fd < 0) {
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// For Android we expect the forkserver_bin in the flag
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if constexpr (sapi::host_os::IsAndroid()) {
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return absl::InternalError(sapi::OsErrorMessage(
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errno,
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"Open init binary passed via --sandbox2_forkserver_binary_path"));
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}
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// Extract the fd when it's owned by EmbedFile
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exec_fd = sapi::EmbedFile::instance()->GetDupFdForFileToc(
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forkserver_bin_embed_create());
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}
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if (exec_fd < 0) {
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return absl::InternalError("Getting FD for init binary failed");
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}
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file_util::fileops::FDCloser exec_fd_closer(exec_fd);
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std::string proc_name = "S2-FORK-SERV";
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int sv[2];
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if (socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, sv) == -1) {
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return absl::InternalError(
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sapi::OsErrorMessage(errno, "Creating socket pair failed"));
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}
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// Fork the fork-server, and clean-up the resources (close remote sockets).
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pid_t pid = util::ForkWithFlags(SIGCHLD);
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if (pid == -1) {
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return absl::InternalError(
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sapi::OsErrorMessage(errno, "Forking forkserver process failed"));
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}
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// Child.
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if (pid == 0) {
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// Move the comms FD to the proper, expected FD number.
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// The new FD will not be CLOEXEC, which is what we want.
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// If exec_fd == Comms::kSandbox2ClientCommsFD then it would be replaced by
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// the comms fd and result in EACCESS at execveat.
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// So first move exec_fd to another fd number.
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if (exec_fd == Comms::kSandbox2ClientCommsFD) {
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exec_fd = dup(exec_fd);
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SAPI_RAW_PCHECK(exec_fd != -1, "duping exec fd failed");
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fcntl(exec_fd, F_SETFD, FD_CLOEXEC);
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}
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SAPI_RAW_PCHECK(dup2(sv[0], Comms::kSandbox2ClientCommsFD) != -1,
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"duping comms fd failed");
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char* const args[] = {proc_name.data(), nullptr};
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char* const envp[] = {nullptr};
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syscall(__NR_execveat, exec_fd, "", args, envp, AT_EMPTY_PATH);
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SAPI_RAW_PLOG(FATAL, "Could not launch forkserver binary");
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abort();
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}
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close(sv[0]);
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return absl::make_unique<GlobalForkClient>(sv[1], pid);
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}
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void WaitForForkserver(pid_t pid) {
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int status;
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pid_t wpid = TEMP_FAILURE_RETRY(waitpid(pid, &status, 0));
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if (wpid != pid) {
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SAPI_RAW_PLOG(ERROR, "Waiting for %d failed", pid);
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}
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if (WIFEXITED(status)) {
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int exit_code = WEXITSTATUS(status);
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if (exit_code == 0) {
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SAPI_RAW_LOG(INFO, "forkserver (pid=%d) terminated normally", pid);
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} else {
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SAPI_RAW_LOG(WARNING, "forkserver (pid=%d) terminated with exit code %d",
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pid, exit_code);
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}
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} else if (WIFSIGNALED(status)) {
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SAPI_RAW_LOG(WARNING, "forkserver (pid=%d) terminated by signal %d", pid,
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WTERMSIG(status));
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}
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}
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} // namespace
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absl::Mutex GlobalForkClient::instance_mutex_(absl::kConstInit);
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GlobalForkClient* GlobalForkClient::instance_ = nullptr;
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void GlobalForkClient::EnsureStarted(GlobalForkserverStartMode mode) {
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absl::MutexLock lock(&instance_mutex_);
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EnsureStartedLocked(mode);
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}
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void GlobalForkClient::EnsureStartedLocked(GlobalForkserverStartMode mode) {
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if (instance_) {
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return;
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}
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if (getenv(kForkServerDisableEnv)) {
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SAPI_RAW_LOG(ERROR,
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"Start of the Global Fork-Server prevented by the %s "
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"environment variable present",
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kForkServerDisableEnv);
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return;
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}
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if (!GetForkserverStartMode().contains(mode)) {
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SAPI_RAW_LOG(
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ERROR, "Start of the Global Fork-Server prevented by commandline flag");
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return;
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}
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absl::StatusOr<std::unique_ptr<GlobalForkClient>> forkserver =
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StartGlobalForkServer();
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if (!forkserver.ok()) {
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SAPI_RAW_LOG(ERROR, "Starting forkserver failed: %s",
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forkserver.status().message().data());
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}
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instance_ = forkserver->release();
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}
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void GlobalForkClient::ForceStart() {
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absl::MutexLock lock(&GlobalForkClient::instance_mutex_);
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SAPI_RAW_CHECK(instance_ == nullptr,
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"A force start requested when the Global Fork-Server was "
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"already running");
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absl::StatusOr<std::unique_ptr<GlobalForkClient>> forkserver =
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StartGlobalForkServer();
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SAPI_RAW_CHECK(forkserver.ok(), forkserver.status().message().data());
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instance_ = forkserver->release();
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}
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void GlobalForkClient::Shutdown() {
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pid_t pid = -1;
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{
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absl::MutexLock lock(&GlobalForkClient::instance_mutex_);
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if (instance_) {
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pid = instance_->fork_client_.pid();
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}
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delete instance_;
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instance_ = nullptr;
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}
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if (pid != -1) {
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WaitForForkserver(pid);
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}
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}
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pid_t GlobalForkClient::SendRequest(const ForkRequest& request, int exec_fd,
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int comms_fd, int user_ns_fd,
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pid_t* init_pid) {
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absl::ReleasableMutexLock lock(&GlobalForkClient::instance_mutex_);
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EnsureStartedLocked(GlobalForkserverStartMode::kOnDemand);
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if (!instance_) {
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return -1;
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}
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pid_t pid = instance_->fork_client_.SendRequest(request, exec_fd, comms_fd,
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user_ns_fd, init_pid);
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if (instance_->comms_.IsTerminated()) {
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LOG(ERROR) << "Global forkserver connection terminated";
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pid_t server_pid = instance_->fork_client_.pid();
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delete instance_;
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instance_ = nullptr;
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// Don't wait for process exit while still holding the lock and potentially
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// blocking other threads.
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lock.Release();
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WaitForForkserver(server_pid);
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}
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return pid;
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}
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pid_t GlobalForkClient::GetPid() {
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absl::MutexLock lock(&instance_mutex_);
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EnsureStartedLocked(GlobalForkserverStartMode::kOnDemand);
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if (!instance_) {
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return -1;
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}
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return instance_->fork_client_.pid();
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}
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bool GlobalForkClient::IsStarted() {
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absl::ReaderMutexLock lock(&instance_mutex_);
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return instance_ != nullptr;
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}
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} // namespace sandbox2
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