mirror of
https://github.com/google/sandboxed-api.git
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118 lines
3.8 KiB
C++
118 lines
3.8 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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// http://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 <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 "absl/base/attributes.h"
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#include "absl/strings/str_cat.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/forkserver.h"
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#include "sandboxed_api/sandbox2/forkserver_bin_embed.h"
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#include "sandboxed_api/sandbox2/sanitizer.h"
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#include "sandboxed_api/sandbox2/util/strerror.h"
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#include "sandboxed_api/util/raw_logging.h"
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namespace sandbox2 {
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// Global ForkClient object linking with the global ForkServer.
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static ForkClient* global_fork_client = nullptr;
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static pid_t global_fork_server_pid = -1;
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ForkClient* GetGlobalForkClient() {
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SAPI_RAW_CHECK(global_fork_client != nullptr,
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"global fork client not initialized");
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return global_fork_client;
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}
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pid_t GetGlobalForkServerPid() { return global_fork_server_pid; }
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static void StartGlobalForkServer() {
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SAPI_RAW_CHECK(global_fork_client == nullptr,
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"global fork server already initialized");
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if (getenv(kForkServerDisableEnv)) {
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SAPI_RAW_VLOG(1,
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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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sanitizer::WaitForTsan();
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// We should be really single-threaded now, as it's the point of the whole
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// exercise.
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int num_threads = sanitizer::GetNumberOfThreads(getpid());
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if (num_threads != 1) {
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SAPI_RAW_LOG(ERROR,
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"BADNESS MAY HAPPEN. ForkServer::Init() created in a "
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"multi-threaded context, %d threads present",
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num_threads);
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}
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int sv[2];
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SAPI_RAW_CHECK(socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, sv) != -1,
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"creating socket pair");
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// Fork the fork-server, and clean-up the resources (close remote sockets).
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pid_t pid;
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{
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pid = fork();
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}
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SAPI_RAW_PCHECK(pid != -1, "during fork");
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// Parent.
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if (pid > 0) {
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close(sv[0]);
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global_fork_client = new ForkClient{new Comms{sv[1]}};
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global_fork_server_pid = pid;
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return;
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}
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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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dup2(sv[0], Comms::kSandbox2ClientCommsFD);
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int exec_fd = sapi::EmbedFile::GetEmbedFileSingleton()->GetFdForFileToc(
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forkserver_bin_embed_create());
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SAPI_RAW_CHECK(exec_fd >= 0, "Getting FD for init binary failed");
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char* const args[] = {strdup("S2-FORK-SERV"), 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_PCHECK(false, "Could not launch forkserver binary");
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}
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} // namespace sandbox2
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// Run the ForkServer from the constructor, when no other threads are present.
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// Because it's possible to start thread-inducing initializers before
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// RunInitializers() (base/googleinit.h) it's not enough to just register
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// a 0000_<name> initializer instead.
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ABSL_ATTRIBUTE_UNUSED
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__attribute__((constructor)) static void StartSandbox2Forkserver() {
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sandbox2::StartGlobalForkServer();
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}
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