sandboxed-api/sandboxed_api/sandbox2/examples/network_proxy/networkproxy_sandbox.cc

// A demo sandbox for the network binary.

#include <arpa/inet.h>
#include <linux/filter.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <syscall.h>

#include <cstdio>
#include <cstdlib>
#include <string>
#include <vector>

#include "absl/base/macros.h"
#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/log/globals.h"
#include "absl/log/initialize.h"
#include "absl/log/log.h"
#include "sandboxed_api/config.h"
#include "sandboxed_api/sandbox2/comms.h"
#include "sandboxed_api/sandbox2/executor.h"
#include "sandboxed_api/sandbox2/policy.h"
#include "sandboxed_api/sandbox2/policybuilder.h"
#include "sandboxed_api/sandbox2/sandbox2.h"
#include "sandboxed_api/sandbox2/util/bpf_helper.h"
#include "sandboxed_api/util/fileops.h"
#include "sandboxed_api/util/runfiles.h"

ABSL_FLAG(bool, connect_with_handler, true, "Connect using automatic mode.");

namespace {

constexpr char kSandboxeePath[] =
    "sandbox2/examples/network_proxy/networkproxy_bin";

std::unique_ptr<sandbox2::Policy> GetPolicy(absl::string_view sandboxee_path) {
  sandbox2::PolicyBuilder builder;
  builder.AllowExit()
      .AllowMmap()
      .AllowRead()
      .AllowWrite()
      .AllowStat()  // printf, puts
      .AllowOpen()
      .AllowSyscall(__NR_sendto)  // send
      .AllowSyscall(__NR_lseek)
      .AllowSyscall(__NR_munmap)
      .AllowSyscall(__NR_getpid)
      .AllowTcMalloc()
      .AddLibrariesForBinary(sandboxee_path);
  if (absl::GetFlag(FLAGS_connect_with_handler)) {
    builder.AddNetworkProxyHandlerPolicy();
  } else {
    builder.AddNetworkProxyPolicy();
  }
  return builder.AllowIPv6("::1").BuildOrDie();
}

void Server(int port) {
  sapi::file_util::fileops::FDCloser s{
      socket(AF_INET6, SOCK_STREAM | SOCK_CLOEXEC, 0)};
  if (s.get() < 0) {
    PLOG(ERROR) << "socket() failed";
    return;
  }

  {
    int enable = 1;
    if (setsockopt(s.get(), SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(enable)) <
        0) {
      PLOG(ERROR) << "setsockopt(SO_REUSEADDR) failed";
      return;
    }
  }

  // Listen to localhost only.
  struct sockaddr_in6 addr = {};
  addr.sin6_family = AF_INET6;
  addr.sin6_port = htons(port);

  int err = inet_pton(AF_INET6, "::1", &addr.sin6_addr.s6_addr);
  if (err == 0) {
    LOG(ERROR) << "inet_pton() failed";
    return;
  } else if (err == -1) {
    PLOG(ERROR) << "inet_pton() failed";
    return;
  }

  if (bind(s.get(), (struct sockaddr*)&addr, sizeof(addr)) < 0) {
    PLOG(ERROR) << "bind() failed";
    return;
  }

  if (listen(s.get(), 1) < 0) {
    PLOG(ERROR) << "listen() failed";
    return;
  }

  sapi::file_util::fileops::FDCloser client{accept(s.get(), 0, 0)};
  if (client.get() < 0) {
    PLOG(ERROR) << "accept() failed";
    return;
  }

  constexpr char kMsg[] = "Hello World\n";
  if (write(client.get(), kMsg, ABSL_ARRAYSIZE(kMsg) - 1) < 0) {
    PLOG(ERROR) << "write() failed";
  }
}

}  // namespace

int main(int argc, char* argv[]) {
  // This test is incompatible with sanitizers.
  // The `SKIP_SANITIZERS_AND_COVERAGE` macro won't work for us here since we
  // need to return something.
  if constexpr (sapi::sanitizers::IsAny()) {
    return EXIT_SUCCESS;
  }
  if (getenv("COVERAGE") != nullptr) {
    return EXIT_SUCCESS;
  }

  absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfo);
  absl::ParseCommandLine(argc, argv);
  absl::InitializeLog();
  int port = 8085;
  std::thread server_thread{Server, port};
  server_thread.detach();

  // Note: In your own code, use sapi::GetDataDependencyFilePath() instead.
  const std::string path =
      sapi::internal::GetSapiDataDependencyFilePath(kSandboxeePath);
  std::vector<std::string> args = {path};
  if (!absl::GetFlag(FLAGS_connect_with_handler)) {
    args.push_back("--noconnect_with_handler");
  }
  std::vector<std::string> envs = {};

  auto executor = std::make_unique<sandbox2::Executor>(path, args, envs);

  executor
      // Sandboxing is enabled by the binary itself (i.e. the networkproxy_bin
      // is capable of enabling sandboxing on its own).
      ->set_enable_sandbox_before_exec(false)
      // Set cwd to / to get rids of warnings connected with file namespace.
      .set_cwd("/");
  executor
      ->limits()
      // Remove restrictions on the size of address-space of sandboxed
      // processes.
      ->set_rlimit_as(RLIM64_INFINITY)
      // Kill sandboxed processes with a signal (SIGXFSZ) if it writes more than
      // these many bytes to the file-system.
      .set_rlimit_fsize(10000)
      // The CPU time limit in seconds.
      .set_rlimit_cpu(100)
      .set_walltime_limit(absl::Seconds(100));

  auto policy = GetPolicy(path);
  sandbox2::Sandbox2 s2(std::move(executor), std::move(policy));
  auto* comms = s2.comms();

  // Let the sandboxee run.
  if (!s2.RunAsync()) {
    auto result = s2.AwaitResult();
    LOG(ERROR) << "RunAsync failed: " << result.ToString();
    return 2;
  }

  // Send the port number via comms
  if (!comms->SendInt32(port)) {
    LOG(ERROR) << "sandboxee_comms->SendInt32() failed";
    return 3;
  }

  auto result = s2.AwaitResult();
  if (result.final_status() != sandbox2::Result::OK) {
    LOG(ERROR) << "Sandbox error: " << result.ToString();
    return 4;  // e.g. sandbox violation, signal (sigsegv)
  }
  auto code = result.reason_code();
  if (code) {
    LOG(ERROR) << "Sandboxee exited with non-zero: " << code;
    return 5;  // e.g. normal child error
  }

  LOG(INFO) << "Sandboxee finished: " << result.ToString();
  return EXIT_SUCCESS;
}