sandboxed-api/sandboxed_api/sandbox2/forkserver_bin.cc

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// Copyright 2019 Google LLC
//
// 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
//
// https://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 <sys/prctl.h>
#include <csignal>
#include <cstdlib>
#include "absl/base/log_severity.h"
#include "absl/log/globals.h"
#include "absl/status/status.h"
#include "sandboxed_api/sandbox2/client.h"
#include "sandboxed_api/sandbox2/comms.h"
#include "sandboxed_api/sandbox2/forkserver.h"
#include "sandboxed_api/sandbox2/sanitizer.h"
#include "sandboxed_api/sandbox2/unwind/unwind.h"
#include "sandboxed_api/util/raw_logging.h"
int main() {
// Make sure the logs go stderr.
absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfo);
// Close all non-essential FDs to keep newly opened FD numbers consistent.
absl::Status status = sandbox2::sanitizer::CloseAllFDsExcept(
{0, 1, 2, sandbox2::Comms::kSandbox2ClientCommsFD});
if (!status.ok()) {
SAPI_RAW_LOG(WARNING, "Closing non-essential FDs failed");
}
// Make the process' name easily recognizable with ps/pstree.
if (prctl(PR_SET_NAME, "S2-FORK-SERV", 0, 0, 0) != 0) {
SAPI_RAW_PLOG(WARNING, "prctl(PR_SET_NAME, 'S2-FORK-SERV')");
}
// Don't react (with stack-tracing) to SIGTERM's sent from other processes
// (e.g. from the borglet or SubProcess). This ForkServer should go down if
// the parent goes down (or if the GlobalForkServerComms is closed), which is
// assured by prctl(PR_SET_PDEATHSIG, SIGKILL) being called in the
// ForkServer::Initialize(). We don't want to change behavior of non-global
// ForkServers, hence it's called here and not in the
// ForkServer::Initialize().
struct sigaction sa;
sa.sa_handler = SIG_IGN;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
if (sigaction(SIGTERM, &sa, nullptr) == -1) {
SAPI_RAW_PLOG(WARNING, "sigaction(SIGTERM, sa_handler=SIG_IGN)");
}
sandbox2::Comms comms(sandbox2::Comms::kDefaultConnection);
sandbox2::ForkServer fork_server(&comms);
sandbox2::sanitizer::WaitForSanitizer();
while (!fork_server.IsTerminated()) {
pid_t child_pid = fork_server.ServeRequest();
if (child_pid == 0) {
sandbox2::Client client(&comms);
client.SandboxMeHere();
return sandbox2::RunLibUnwindAndSymbolizer(&comms) ? EXIT_SUCCESS
: EXIT_FAILURE;
}
}
SAPI_RAW_VLOG(1, "ForkServer Comms closed. Exiting");
}