mirror of
https://github.com/google/sandboxed-api.git
synced 2024-03-22 13:11:30 +08:00
336 lines
10 KiB
C++
336 lines
10 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 <sched.h>
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#include <sys/mman.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 <climits>
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#include <csignal>
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#include <cstdlib>
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#include <memory>
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#include <string>
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#include <vector>
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#include "absl/cleanup/cleanup.h"
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#include "absl/flags/declare.h"
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#include "absl/flags/flag.h"
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#include "absl/log/log.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/raw_logging.h"
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ABSL_DECLARE_FLAG(bool, sandbox2_forkserver_use_waitpid);
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namespace sandbox2 {
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namespace file_util = ::sapi::file_util;
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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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} // namespace
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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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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(std::string, sandbox2_forkserver_binary_path, "",
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"Path to forkserver_bin binary");
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ABSL_FLAG(sandbox2::GlobalForkserverStartModeSet,
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sandbox2_forkserver_start_mode,
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sandbox2::GlobalForkserverStartModeSet(
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sandbox2::GlobalForkserverStartMode::kOnDemand)
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,
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"When Sandbox2 Forkserver process should be started");
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namespace sandbox2 {
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namespace {
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GlobalForkserverStartModeSet GetForkserverStartMode() {
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return absl::GetFlag(FLAGS_sandbox2_forkserver_start_mode);
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}
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struct ForkserverArgs {
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int exec_fd;
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int comms_fd;
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bool use_waitpid;
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};
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int LaunchForkserver(void* vargs) {
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auto* args = static_cast<ForkserverArgs*>(vargs);
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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 (args->exec_fd == Comms::kSandbox2ClientCommsFD) {
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args->exec_fd = dup(args->exec_fd);
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SAPI_RAW_PCHECK(args->exec_fd != -1, "duping exec fd failed");
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fcntl(args->exec_fd, F_SETFD, FD_CLOEXEC);
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}
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SAPI_RAW_PCHECK(dup2(args->comms_fd, Comms::kSandbox2ClientCommsFD) != -1,
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"duping comms fd failed");
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char proc_name[] = "S2-FORK-SERV";
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char use_waitpid[] = "--sandbox2_forkserver_use_waitpid";
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char* argv[] = {proc_name, nullptr, nullptr};
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if (args->use_waitpid) {
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argv[1] = use_waitpid;
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}
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util::Execveat(args->exec_fd, "", argv, environ, AT_EMPTY_PATH);
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SAPI_RAW_PLOG(FATAL, "Could not launch forkserver binary");
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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::ErrnoToStatus(
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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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int sv[2];
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if (socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, sv) == -1) {
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return absl::ErrnoToStatus(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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const size_t stack_size = PTHREAD_STACK_MIN;
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int clone_flags = CLONE_VM | CLONE_VFORK | SIGCHLD;
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// CLONE_VM does not play well with TSan.
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if constexpr (sapi::sanitizers::IsTSan()) {
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clone_flags &= ~CLONE_VM & ~CLONE_VFORK;
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}
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char* stack =
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static_cast<char*>(mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0));
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if (stack == MAP_FAILED) {
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return absl::ErrnoToStatus(errno, "Allocating stack failed");
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}
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absl::Cleanup stack_dealloc = [stack, stack_size] {
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munmap(stack, stack_size);
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};
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ForkserverArgs args = {
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.exec_fd = exec_fd,
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.comms_fd = sv[0],
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.use_waitpid = absl::GetFlag(FLAGS_sandbox2_forkserver_use_waitpid),
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};
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pid_t pid = clone(LaunchForkserver, &stack[stack_size], clone_flags, &args,
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nullptr, nullptr, nullptr);
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if (pid == -1) {
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return absl::ErrnoToStatus(errno, "Forking forkserver process failed");
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}
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close(sv[0]);
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return std::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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SandboxeeProcess GlobalForkClient::SendRequest(const ForkRequest& request,
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int exec_fd, int comms_fd) {
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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 SandboxeeProcess();
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}
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SandboxeeProcess process =
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instance_->fork_client_.SendRequest(request, exec_fd, comms_fd);
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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 process;
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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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