components/nacl/loader/nacl_helper_linux.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // A mini-zygote specifically for Native Client.
   6
   7 #include "components/nacl/loader/nacl_helper_linux.h"
   8
   9 #include <errno.h>
  10 #include <fcntl.h>
  11 #include <signal.h>
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <sys/socket.h>
  15 #include <sys/stat.h>
  16 #include <sys/types.h>
  17
  18 #include <string>
  19 #include <vector>
  20
  21 #include "base/at_exit.h"
  22 #include "base/command_line.h"
  23 #include "base/files/scoped_file.h"
  24 #include "base/logging.h"
  25 #include "base/memory/scoped_ptr.h"
  26 #include "base/memory/scoped_vector.h"
  27 #include "base/message_loop/message_loop.h"
  28 #include "base/posix/eintr_wrapper.h"
  29 #include "base/posix/global_descriptors.h"
  30 #include "base/posix/unix_domain_socket_linux.h"
  31 #include "base/process/kill.h"
  32 #include "base/process/process_handle.h"
  33 #include "base/rand_util.h"
  34 #include "components/nacl/common/nacl_switches.h"
  35 #include "components/nacl/loader/nacl_listener.h"
  36 #include "components/nacl/loader/nonsfi/nonsfi_listener.h"
  37 #include "components/nacl/loader/sandbox_linux/nacl_sandbox_linux.h"
  38 #include "content/public/common/content_descriptors.h"
  39 #include "content/public/common/send_zygote_child_ping_linux.h"
  40 #include "content/public/common/zygote_fork_delegate_linux.h"
  41 #include "crypto/nss_util.h"
  42 #include "ipc/ipc_descriptors.h"
  43 #include "ipc/ipc_switches.h"
  44 #include "sandbox/linux/services/libc_urandom_override.h"
  45
  46 #if !defined(OS_NACL_NONSFI)
  47 #include "third_party/mojo/src/mojo/edk/embedder/embedder.h"
  48 #include "third_party/mojo/src/mojo/edk/embedder/simple_platform_support.h"
  49 #endif
  50
  51 #if defined(OS_NACL_NONSFI)
  52 #include "native_client/src/public/nonsfi/irt_exception_handling.h"
  53 #else
  54 #include <link.h>
  55 #include "components/nacl/loader/nonsfi/irt_exception_handling.h"
  56 #endif
  57
  58 namespace {
  59
  60 struct NaClLoaderSystemInfo {
  61   size_t prereserved_sandbox_size;
  62   long number_of_cores;
  63 };
  64
  65 // Replace |file_descriptor| with the reading end of a closed pipe.
  66 void ReplaceFDWithDummy(int file_descriptor) {
  67   // Make sure that file_descriptor is an open descriptor.
  68   PCHECK(-1 != fcntl(file_descriptor, F_GETFD, 0));
  69   int pipefd[2];
  70   PCHECK(0 == pipe(pipefd));
  71   PCHECK(-1 != dup2(pipefd[0], file_descriptor));
  72   PCHECK(0 == IGNORE_EINTR(close(pipefd[0])));
  73   PCHECK(0 == IGNORE_EINTR(close(pipefd[1])));
  74 }
  75
  76 // The child must mimic the behavior of zygote_main_linux.cc on the child
  77 // side of the fork. See zygote_main_linux.cc:HandleForkRequest from
  78 //   if (!child) {
  79 void BecomeNaClLoader(base::ScopedFD browser_fd,
  80                       const NaClLoaderSystemInfo& system_info,
  81                       bool uses_nonsfi_mode,
  82                       nacl::NaClSandbox* nacl_sandbox) {
  83   DCHECK(nacl_sandbox);
  84   VLOG(1) << "NaCl loader: setting up IPC descriptor";
  85   // Close or shutdown IPC channels that we don't need anymore.
  86   PCHECK(0 == IGNORE_EINTR(close(kNaClZygoteDescriptor)));
  87   // In Non-SFI mode, it's important to close any non-expected IPC channels.
  88   if (uses_nonsfi_mode) {
  89     // The low-level kSandboxIPCChannel is used by renderers and NaCl for
  90     // various operations. See the LinuxSandbox::METHOD_* methods. NaCl uses
  91     // LinuxSandbox::METHOD_MAKE_SHARED_MEMORY_SEGMENT in SFI mode, so this
  92     // should only be closed in Non-SFI mode.
  93     // This file descriptor is insidiously used by a number of APIs. Closing it
  94     // could lead to difficult to debug issues. Instead of closing it, replace
  95     // it with a dummy.
  96     const int sandbox_ipc_channel =
  97         base::GlobalDescriptors::kBaseDescriptor + kSandboxIPCChannel;
  98
  99     ReplaceFDWithDummy(sandbox_ipc_channel);
 100
 101     // Install crash signal handlers before disallowing system calls.
 102 #if defined(OS_NACL_NONSFI)
 103     nonsfi_initialize_signal_handler();
 104 #else
 105     nacl::nonsfi::InitializeSignalHandler();
 106 #endif
 107   }
 108
 109   // Always ignore SIGPIPE, for consistency with other Chrome processes and
 110   // because some IPC code, such as sync_socket_posix.cc, requires this.
 111   // We do this before seccomp-bpf is initialized.
 112   PCHECK(signal(SIGPIPE, SIG_IGN) != SIG_ERR);
 113
 114   // Finish layer-1 sandbox initialization and initialize the layer-2 sandbox.
 115   CHECK(!nacl_sandbox->HasOpenDirectory());
 116 #if !defined(OS_NACL_NONSFI)
 117   // Currently Layer-two sandbox is not yet supported on nacl_helper_nonsfi.
 118   // TODO(hidehiko): Enable the sandbox.
 119   nacl_sandbox->InitializeLayerTwoSandbox(uses_nonsfi_mode);
 120 #endif
 121   nacl_sandbox->SealLayerOneSandbox();
 122   nacl_sandbox->CheckSandboxingStateWithPolicy();
 123
 124   base::GlobalDescriptors::GetInstance()->Set(kPrimaryIPCChannel,
 125                                               browser_fd.release());
 126
 127   base::MessageLoopForIO main_message_loop;
 128 #if defined(OS_NACL_NONSFI)
 129   CHECK(uses_nonsfi_mode);
 130   nacl::nonsfi::NonSfiListener listener;
 131   listener.Listen();
 132 #else
 133   // TODO(hidehiko): Drop Non-SFI supporting from nacl_helper after the
 134   // nacl_helper_nonsfi switching is done.
 135   if (uses_nonsfi_mode) {
 136     nacl::nonsfi::NonSfiListener listener;
 137     listener.Listen();
 138   } else {
 139     NaClListener listener;
 140     listener.set_prereserved_sandbox_size(system_info.prereserved_sandbox_size);
 141     listener.set_number_of_cores(system_info.number_of_cores);
 142     listener.Listen();
 143   }
 144 #endif
 145   _exit(0);
 146 }
 147
 148 // Start the NaCl loader in a child created by the NaCl loader Zygote.
 149 void ChildNaClLoaderInit(ScopedVector<base::ScopedFD> child_fds,
 150                          const NaClLoaderSystemInfo& system_info,
 151                          bool uses_nonsfi_mode,
 152                          nacl::NaClSandbox* nacl_sandbox,
 153                          const std::string& channel_id) {
 154   DCHECK(child_fds.size() >
 155          std::max(content::ZygoteForkDelegate::kPIDOracleFDIndex,
 156                   content::ZygoteForkDelegate::kBrowserFDIndex));
 157
 158   // Ping the PID oracle socket.
 159   CHECK(content::SendZygoteChildPing(
 160       child_fds[content::ZygoteForkDelegate::kPIDOracleFDIndex]->get()));
 161
 162   base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
 163       switches::kProcessChannelID, channel_id);
 164
 165   // Save the browser socket and close the rest.
 166   base::ScopedFD browser_fd(
 167       child_fds[content::ZygoteForkDelegate::kBrowserFDIndex]->Pass());
 168   child_fds.clear();
 169
 170   BecomeNaClLoader(
 171       browser_fd.Pass(), system_info, uses_nonsfi_mode, nacl_sandbox);
 172   _exit(1);
 173 }
 174
 175 // Handle a fork request from the Zygote.
 176 // Some of this code was lifted from
 177 // content/browser/zygote_main_linux.cc:ForkWithRealPid()
 178 bool HandleForkRequest(ScopedVector<base::ScopedFD> child_fds,
 179                        const NaClLoaderSystemInfo& system_info,
 180                        nacl::NaClSandbox* nacl_sandbox,
 181                        PickleIterator* input_iter,
 182                        Pickle* output_pickle) {
 183   bool uses_nonsfi_mode;
 184   if (!input_iter->ReadBool(&uses_nonsfi_mode)) {
 185     LOG(ERROR) << "Could not read uses_nonsfi_mode status";
 186     return false;
 187   }
 188
 189   std::string channel_id;
 190   if (!input_iter->ReadString(&channel_id)) {
 191     LOG(ERROR) << "Could not read channel_id string";
 192     return false;
 193   }
 194
 195   if (content::ZygoteForkDelegate::kNumPassedFDs != child_fds.size()) {
 196     LOG(ERROR) << "nacl_helper: unexpected number of fds, got "
 197         << child_fds.size();
 198     return false;
 199   }
 200
 201   VLOG(1) << "nacl_helper: forking";
 202   pid_t child_pid = fork();
 203   if (child_pid < 0) {
 204     PLOG(ERROR) << "*** fork() failed.";
 205   }
 206
 207   if (child_pid == 0) {
 208     ChildNaClLoaderInit(child_fds.Pass(),
 209                         system_info,
 210                         uses_nonsfi_mode,
 211                         nacl_sandbox,
 212                         channel_id);
 213     NOTREACHED();
 214   }
 215
 216   // I am the parent.
 217   // First, close the dummy_fd so the sandbox won't find me when
 218   // looking for the child's pid in /proc. Also close other fds.
 219   child_fds.clear();
 220   VLOG(1) << "nacl_helper: child_pid is " << child_pid;
 221
 222   // Now send child_pid (eventually -1 if fork failed) to the Chrome Zygote.
 223   output_pickle->WriteInt(child_pid);
 224   return true;
 225 }
 226
 227 bool HandleGetTerminationStatusRequest(PickleIterator* input_iter,
 228                                        Pickle* output_pickle) {
 229   pid_t child_to_wait;
 230   if (!input_iter->ReadInt(&child_to_wait)) {
 231     LOG(ERROR) << "Could not read pid to wait for";
 232     return false;
 233   }
 234
 235   bool known_dead;
 236   if (!input_iter->ReadBool(&known_dead)) {
 237     LOG(ERROR) << "Could not read known_dead status";
 238     return false;
 239   }
 240   // TODO(jln): With NaCl, known_dead seems to never be set to true (unless
 241   // called from the Zygote's kZygoteCommandReap command). This means that we
 242   // will sometimes detect the process as still running when it's not. Fix
 243   // this!
 244
 245   int exit_code;
 246   base::TerminationStatus status;
 247   if (known_dead)
 248     status = base::GetKnownDeadTerminationStatus(child_to_wait, &exit_code);
 249   else
 250     status = base::GetTerminationStatus(child_to_wait, &exit_code);
 251   output_pickle->WriteInt(static_cast<int>(status));
 252   output_pickle->WriteInt(exit_code);
 253   return true;
 254 }
 255
 256 // Honor a command |command_type|. Eventual command parameters are
 257 // available in |input_iter| and eventual file descriptors attached to
 258 // the command are in |attached_fds|.
 259 // Reply to the command on |reply_fds|.
 260 bool HonorRequestAndReply(int reply_fd,
 261                           int command_type,
 262                           ScopedVector<base::ScopedFD> attached_fds,
 263                           const NaClLoaderSystemInfo& system_info,
 264                           nacl::NaClSandbox* nacl_sandbox,
 265                           PickleIterator* input_iter) {
 266   Pickle write_pickle;
 267   bool have_to_reply = false;
 268   // Commands must write anything to send back to |write_pickle|.
 269   switch (command_type) {
 270     case nacl::kNaClForkRequest:
 271       have_to_reply = HandleForkRequest(attached_fds.Pass(),
 272                                         system_info,
 273                                         nacl_sandbox,
 274                                         input_iter,
 275                                         &write_pickle);
 276       break;
 277     case nacl::kNaClGetTerminationStatusRequest:
 278       have_to_reply =
 279           HandleGetTerminationStatusRequest(input_iter, &write_pickle);
 280       break;
 281     default:
 282       LOG(ERROR) << "Unsupported command from Zygote";
 283       return false;
 284   }
 285   if (!have_to_reply)
 286     return false;
 287   const std::vector<int> empty;  // We never send file descriptors back.
 288   if (!UnixDomainSocket::SendMsg(reply_fd, write_pickle.data(),
 289                                  write_pickle.size(), empty)) {
 290     LOG(ERROR) << "*** send() to zygote failed";
 291     return false;
 292   }
 293   return true;
 294 }
 295
 296 // Read a request from the Zygote from |zygote_ipc_fd| and handle it.
 297 // Die on EOF from |zygote_ipc_fd|.
 298 bool HandleZygoteRequest(int zygote_ipc_fd,
 299                          const NaClLoaderSystemInfo& system_info,
 300                          nacl::NaClSandbox* nacl_sandbox) {
 301   ScopedVector<base::ScopedFD> fds;
 302   char buf[kNaClMaxIPCMessageLength];
 303   const ssize_t msglen = UnixDomainSocket::RecvMsg(zygote_ipc_fd,
 304       &buf, sizeof(buf), &fds);
 305   // If the Zygote has started handling requests, we should be sandboxed via
 306   // the setuid sandbox.
 307   if (!nacl_sandbox->layer_one_enabled()) {
 308     LOG(ERROR) << "NaCl helper process running without a sandbox!\n"
 309       << "Most likely you need to configure your SUID sandbox "
 310       << "correctly";
 311   }
 312   if (msglen == 0 || (msglen == -1 && errno == ECONNRESET)) {
 313     // EOF from the browser. Goodbye!
 314     _exit(0);
 315   }
 316   if (msglen < 0) {
 317     PLOG(ERROR) << "nacl_helper: receive from zygote failed";
 318     return false;
 319   }
 320
 321   Pickle read_pickle(buf, msglen);
 322   PickleIterator read_iter(read_pickle);
 323   int command_type;
 324   if (!read_iter.ReadInt(&command_type)) {
 325     LOG(ERROR) << "Unable to read command from Zygote";
 326     return false;
 327   }
 328   return HonorRequestAndReply(zygote_ipc_fd,
 329                               command_type,
 330                               fds.Pass(),
 331                               system_info,
 332                               nacl_sandbox,
 333                               &read_iter);
 334 }
 335
 336 #if !defined(OS_NACL_NONSFI)
 337 static const char kNaClHelperReservedAtZero[] = "reserved_at_zero";
 338 static const char kNaClHelperRDebug[] = "r_debug";
 339
 340 // Since we were started by nacl_helper_bootstrap rather than in the
 341 // usual way, the debugger cannot figure out where our executable
 342 // or the dynamic linker or the shared libraries are in memory,
 343 // so it won't find any symbols.  But we can fake it out to find us.
 344 //
 345 // The zygote passes --r_debug=0xXXXXXXXXXXXXXXXX.
 346 // nacl_helper_bootstrap replaces the Xs with the address of its _r_debug
 347 // structure.  The debugger will look for that symbol by name to
 348 // discover the addresses of key dynamic linker data structures.
 349 // Since all it knows about is the original main executable, which
 350 // is the bootstrap program, it finds the symbol defined there.  The
 351 // dynamic linker's structure is somewhere else, but it is filled in
 352 // after initialization.  The parts that really matter to the
 353 // debugger never change.  So we just copy the contents of the
 354 // dynamic linker's structure into the address provided by the option.
 355 // Hereafter, if someone attaches a debugger (or examines a core dump),
 356 // the debugger will find all the symbols in the normal way.
 357 //
 358 // Non-SFI mode does not use nacl_helper_bootstrap, so it doesn't need to
 359 // process the --r_debug option.
 360 static void CheckRDebug(char* argv0) {
 361   std::string r_debug_switch_value =
 362       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 363           kNaClHelperRDebug);
 364   if (!r_debug_switch_value.empty()) {
 365     char* endp;
 366     uintptr_t r_debug_addr = strtoul(r_debug_switch_value.c_str(), &endp, 0);
 367     if (r_debug_addr != 0 && *endp == '\0') {
 368       r_debug* bootstrap_r_debug = reinterpret_cast<r_debug*>(r_debug_addr);
 369       *bootstrap_r_debug = _r_debug;
 370
 371       // Since the main executable (the bootstrap program) does not
 372       // have a dynamic section, the debugger will not skip the
 373       // first element of the link_map list as it usually would for
 374       // an executable or PIE that was loaded normally.  But the
 375       // dynamic linker has set l_name for the PIE to "" as is
 376       // normal for the main executable.  So the debugger doesn't
 377       // know which file it is.  Fill in the actual file name, which
 378       // came in as our argv[0].
 379       link_map* l = _r_debug.r_map;
 380       if (l->l_name[0] == '\0')
 381         l->l_name = argv0;
 382     }
 383   }
 384 }
 385
 386 // The zygote passes --reserved_at_zero=0xXXXXXXXXXXXXXXXX.
 387 // nacl_helper_bootstrap replaces the Xs with the amount of prereserved
 388 // sandbox memory.
 389 //
 390 // CheckReservedAtZero parses the value of the argument reserved_at_zero
 391 // and returns the amount of prereserved sandbox memory.
 392 static size_t CheckReservedAtZero() {
 393   size_t prereserved_sandbox_size = 0;
 394   std::string reserved_at_zero_switch_value =
 395       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 396           kNaClHelperReservedAtZero);
 397   if (!reserved_at_zero_switch_value.empty()) {
 398     char* endp;
 399     prereserved_sandbox_size =
 400         strtoul(reserved_at_zero_switch_value.c_str(), &endp, 0);
 401     if (*endp != '\0')
 402       LOG(ERROR) << "Could not parse reserved_at_zero argument value of "
 403                  << reserved_at_zero_switch_value;
 404   }
 405   return prereserved_sandbox_size;
 406 }
 407 #endif
 408
 409 }  // namespace
 410
 411 #if defined(ADDRESS_SANITIZER)
 412 // Do not install the SIGSEGV handler in ASan. This should make the NaCl
 413 // platform qualification test pass.
 414 // detect_odr_violation=0: http://crbug.com/376306
 415 static const char kAsanDefaultOptionsNaCl[] =
 416     "handle_segv=0:detect_odr_violation=0";
 417
 418 // Override the default ASan options for the NaCl helper.
 419 // __asan_default_options should not be instrumented, because it is called
 420 // before ASan is initialized.
 421 extern "C"
 422 __attribute__((no_sanitize_address))
 423 // The function isn't referenced from the executable itself. Make sure it isn't
 424 // stripped by the linker.
 425 __attribute__((used))
 426 __attribute__((visibility("default")))
 427 const char* __asan_default_options() {
 428   return kAsanDefaultOptionsNaCl;
 429 }
 430 #endif
 431
 432 int main(int argc, char* argv[]) {
 433   base::CommandLine::Init(argc, argv);
 434   base::AtExitManager exit_manager;
 435   base::RandUint64();  // acquire /dev/urandom fd before sandbox is raised
 436
 437 #if !defined(OS_NACL_NONSFI)
 438   // NSS is only needed for SFI NaCl.
 439   // Allows NSS to fopen() /dev/urandom.
 440   sandbox::InitLibcUrandomOverrides();
 441 #if defined(USE_NSS)
 442   // Configure NSS for use inside the NaCl process.
 443   // The fork check has not caused problems for NaCl, but this appears to be
 444   // best practice (see other places LoadNSSLibraries is called.)
 445   crypto::DisableNSSForkCheck();
 446   // Without this line on Linux, HMAC::Init will instantiate a singleton that
 447   // in turn attempts to open a file.  Disabling this behavior avoids a ~70 ms
 448   // stall the first time HMAC is used.
 449   crypto::ForceNSSNoDBInit();
 450   // Load shared libraries before sandbox is raised.
 451   // NSS is needed to perform hashing for validation caching.
 452   crypto::LoadNSSLibraries();
 453 #endif  // defined(USE_NSS)
 454 #endif  // defined(OS_NACL_NONSFI)
 455   const NaClLoaderSystemInfo system_info = {
 456 #if !defined(OS_NACL_NONSFI)
 457     // These are not used by nacl_helper_nonsfi.
 458     CheckReservedAtZero(),
 459     sysconf(_SC_NPROCESSORS_ONLN)
 460 #endif
 461   };
 462
 463 #if !defined(OS_NACL_NONSFI)
 464   CheckRDebug(argv[0]);
 465 #endif
 466
 467 // TODO(teravest): Enable mojo for nonsfi. http://crbug.com/473418
 468 #if !defined(OS_NACL_NONSFI)
 469   mojo::embedder::Init(
 470       make_scoped_ptr(new mojo::embedder::SimplePlatformSupport()));
 471 #endif
 472
 473   scoped_ptr<nacl::NaClSandbox> nacl_sandbox(new nacl::NaClSandbox);
 474   // Make sure that the early initialization did not start any spurious
 475   // threads.
 476 #if !defined(THREAD_SANITIZER)
 477   CHECK(nacl_sandbox->IsSingleThreaded());
 478 #endif
 479
 480   const bool is_init_process = 1 == getpid();
 481   nacl_sandbox->InitializeLayerOneSandbox();
 482   CHECK_EQ(is_init_process, nacl_sandbox->layer_one_enabled());
 483
 484   const std::vector<int> empty;
 485   // Send the zygote a message to let it know we are ready to help
 486   if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor,
 487                                  kNaClHelperStartupAck,
 488                                  sizeof(kNaClHelperStartupAck), empty)) {
 489     LOG(ERROR) << "*** send() to zygote failed";
 490   }
 491
 492   // Now handle requests from the Zygote.
 493   while (true) {
 494     bool request_handled = HandleZygoteRequest(
 495         kNaClZygoteDescriptor, system_info, nacl_sandbox.get());
 496     // Do not turn this into a CHECK() without thinking about robustness
 497     // against malicious IPC requests.
 498     DCHECK(request_handled);
 499   }
 500   NOTREACHED();
 501 }