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 "native_client/src/public/nonsfi/irt_exception_handling.h"
  48 #else
  49 #include <link.h>
  50 #include "components/nacl/loader/nonsfi/irt_exception_handling.h"
  51 #endif
  52
  53 namespace {
  54
  55 struct NaClLoaderSystemInfo {
  56   size_t prereserved_sandbox_size;
  57   long number_of_cores;
  58 };
  59
  60 // Replace |file_descriptor| with the reading end of a closed pipe.
  61 void ReplaceFDWithDummy(int file_descriptor) {
  62   // Make sure that file_descriptor is an open descriptor.
  63   PCHECK(-1 != fcntl(file_descriptor, F_GETFD, 0));
  64   int pipefd[2];
  65   PCHECK(0 == pipe(pipefd));
  66   PCHECK(-1 != dup2(pipefd[0], file_descriptor));
  67   PCHECK(0 == IGNORE_EINTR(close(pipefd[0])));
  68   PCHECK(0 == IGNORE_EINTR(close(pipefd[1])));
  69 }
  70
  71 // The child must mimic the behavior of zygote_main_linux.cc on the child
  72 // side of the fork. See zygote_main_linux.cc:HandleForkRequest from
  73 //   if (!child) {
  74 void BecomeNaClLoader(base::ScopedFD browser_fd,
  75                       const NaClLoaderSystemInfo& system_info,
  76                       bool uses_nonsfi_mode,
  77                       nacl::NaClSandbox* nacl_sandbox) {
  78 #if !defined(OS_NACL_NONSFI)
  79   // Currently sandbox is disabled for nacl_helper_nonsfi.
  80   // TODO(hidehiko): Enable sandbox.
  81   DCHECK(nacl_sandbox);
  82 #endif
  83   VLOG(1) << "NaCl loader: setting up IPC descriptor";
  84   // Close or shutdown IPC channels that we don't need anymore.
  85   PCHECK(0 == IGNORE_EINTR(close(kNaClZygoteDescriptor)));
  86   // In Non-SFI mode, it's important to close any non-expected IPC channels.
  87   if (uses_nonsfi_mode) {
  88     // The low-level kSandboxIPCChannel is used by renderers and NaCl for
  89     // various operations. See the LinuxSandbox::METHOD_* methods. NaCl uses
  90     // LinuxSandbox::METHOD_MAKE_SHARED_MEMORY_SEGMENT in SFI mode, so this
  91     // should only be closed in Non-SFI mode.
  92     // This file descriptor is insidiously used by a number of APIs. Closing it
  93     // could lead to difficult to debug issues. Instead of closing it, replace
  94     // it with a dummy.
  95     const int sandbox_ipc_channel =
  96         base::GlobalDescriptors::kBaseDescriptor + kSandboxIPCChannel;
  97
  98     ReplaceFDWithDummy(sandbox_ipc_channel);
  99
 100     // Install crash signal handlers before disallowing system calls.
 101 #if defined(OS_NACL_NONSFI)
 102     nonsfi_initialize_signal_handler();
 103 #else
 104     nacl::nonsfi::InitializeSignalHandler();
 105 #endif
 106   }
 107
 108   // Always ignore SIGPIPE, for consistency with other Chrome processes and
 109   // because some IPC code, such as sync_socket_posix.cc, requires this.
 110   // We do this before seccomp-bpf is initialized.
 111   PCHECK(signal(SIGPIPE, SIG_IGN) != SIG_ERR);
 112
 113 #if !defined(OS_NACL_NONSFI)
 114   // Currently sandbox is disabled for nacl_helper_nonsfi.
 115   // TODO(hidehiko): Enable sandbox.
 116   // Finish layer-1 sandbox initialization and initialize the layer-2 sandbox.
 117   CHECK(!nacl_sandbox->HasOpenDirectory());
 118   nacl_sandbox->InitializeLayerTwoSandbox(uses_nonsfi_mode);
 119   nacl_sandbox->SealLayerOneSandbox();
 120   nacl_sandbox->CheckSandboxingStateWithPolicy();
 121 #endif
 122
 123   base::GlobalDescriptors::GetInstance()->Set(kPrimaryIPCChannel,
 124                                               browser_fd.release());
 125
 126   base::MessageLoopForIO main_message_loop;
 127 #if defined(OS_NACL_NONSFI)
 128   CHECK(uses_nonsfi_mode);
 129   nacl::nonsfi::NonSfiListener listener;
 130   listener.Listen();
 131 #else
 132   // TODO(hidehiko): Drop Non-SFI supporting from nacl_helper after the
 133   // nacl_helper_nonsfi switching is done.
 134   if (uses_nonsfi_mode) {
 135     nacl::nonsfi::NonSfiListener listener;
 136     listener.Listen();
 137   } else {
 138     NaClListener listener;
 139     listener.set_prereserved_sandbox_size(system_info.prereserved_sandbox_size);
 140     listener.set_number_of_cores(system_info.number_of_cores);
 141     listener.Listen();
 142   }
 143 #endif
 144   _exit(0);
 145 }
 146
 147 // Start the NaCl loader in a child created by the NaCl loader Zygote.
 148 void ChildNaClLoaderInit(ScopedVector<base::ScopedFD> child_fds,
 149                          const NaClLoaderSystemInfo& system_info,
 150                          bool uses_nonsfi_mode,
 151                          nacl::NaClSandbox* nacl_sandbox,
 152                          const std::string& channel_id) {
 153   DCHECK(child_fds.size() >
 154          std::max(content::ZygoteForkDelegate::kPIDOracleFDIndex,
 155                   content::ZygoteForkDelegate::kBrowserFDIndex));
 156
 157   // Ping the PID oracle socket.
 158   CHECK(content::SendZygoteChildPing(
 159       child_fds[content::ZygoteForkDelegate::kPIDOracleFDIndex]->get()));
 160
 161   base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
 162       switches::kProcessChannelID, channel_id);
 163
 164   // Save the browser socket and close the rest.
 165   base::ScopedFD browser_fd(
 166       child_fds[content::ZygoteForkDelegate::kBrowserFDIndex]->Pass());
 167   child_fds.clear();
 168
 169   BecomeNaClLoader(
 170       browser_fd.Pass(), system_info, uses_nonsfi_mode, nacl_sandbox);
 171   _exit(1);
 172 }
 173
 174 // Handle a fork request from the Zygote.
 175 // Some of this code was lifted from
 176 // content/browser/zygote_main_linux.cc:ForkWithRealPid()
 177 bool HandleForkRequest(ScopedVector<base::ScopedFD> child_fds,
 178                        const NaClLoaderSystemInfo& system_info,
 179                        nacl::NaClSandbox* nacl_sandbox,
 180                        PickleIterator* input_iter,
 181                        Pickle* output_pickle) {
 182   bool uses_nonsfi_mode;
 183   if (!input_iter->ReadBool(&uses_nonsfi_mode)) {
 184     LOG(ERROR) << "Could not read uses_nonsfi_mode status";
 185     return false;
 186   }
 187
 188   std::string channel_id;
 189   if (!input_iter->ReadString(&channel_id)) {
 190     LOG(ERROR) << "Could not read channel_id string";
 191     return false;
 192   }
 193
 194   if (content::ZygoteForkDelegate::kNumPassedFDs != child_fds.size()) {
 195     LOG(ERROR) << "nacl_helper: unexpected number of fds, got "
 196         << child_fds.size();
 197     return false;
 198   }
 199
 200   VLOG(1) << "nacl_helper: forking";
 201   pid_t child_pid = fork();
 202   if (child_pid < 0) {
 203     PLOG(ERROR) << "*** fork() failed.";
 204   }
 205
 206   if (child_pid == 0) {
 207     ChildNaClLoaderInit(child_fds.Pass(),
 208                         system_info,
 209                         uses_nonsfi_mode,
 210                         nacl_sandbox,
 211                         channel_id);
 212     NOTREACHED();
 213   }
 214
 215   // I am the parent.
 216   // First, close the dummy_fd so the sandbox won't find me when
 217   // looking for the child's pid in /proc. Also close other fds.
 218   child_fds.clear();
 219   VLOG(1) << "nacl_helper: child_pid is " << child_pid;
 220
 221   // Now send child_pid (eventually -1 if fork failed) to the Chrome Zygote.
 222   output_pickle->WriteInt(child_pid);
 223   return true;
 224 }
 225
 226 bool HandleGetTerminationStatusRequest(PickleIterator* input_iter,
 227                                        Pickle* output_pickle) {
 228   pid_t child_to_wait;
 229   if (!input_iter->ReadInt(&child_to_wait)) {
 230     LOG(ERROR) << "Could not read pid to wait for";
 231     return false;
 232   }
 233
 234   bool known_dead;
 235   if (!input_iter->ReadBool(&known_dead)) {
 236     LOG(ERROR) << "Could not read known_dead status";
 237     return false;
 238   }
 239   // TODO(jln): With NaCl, known_dead seems to never be set to true (unless
 240   // called from the Zygote's kZygoteCommandReap command). This means that we
 241   // will sometimes detect the process as still running when it's not. Fix
 242   // this!
 243
 244   int exit_code;
 245   base::TerminationStatus status;
 246   if (known_dead)
 247     status = base::GetKnownDeadTerminationStatus(child_to_wait, &exit_code);
 248   else
 249     status = base::GetTerminationStatus(child_to_wait, &exit_code);
 250   output_pickle->WriteInt(static_cast<int>(status));
 251   output_pickle->WriteInt(exit_code);
 252   return true;
 253 }
 254
 255 // Honor a command |command_type|. Eventual command parameters are
 256 // available in |input_iter| and eventual file descriptors attached to
 257 // the command are in |attached_fds|.
 258 // Reply to the command on |reply_fds|.
 259 bool HonorRequestAndReply(int reply_fd,
 260                           int command_type,
 261                           ScopedVector<base::ScopedFD> attached_fds,
 262                           const NaClLoaderSystemInfo& system_info,
 263                           nacl::NaClSandbox* nacl_sandbox,
 264                           PickleIterator* input_iter) {
 265   Pickle write_pickle;
 266   bool have_to_reply = false;
 267   // Commands must write anything to send back to |write_pickle|.
 268   switch (command_type) {
 269     case nacl::kNaClForkRequest:
 270       have_to_reply = HandleForkRequest(attached_fds.Pass(),
 271                                         system_info,
 272                                         nacl_sandbox,
 273                                         input_iter,
 274                                         &write_pickle);
 275       break;
 276     case nacl::kNaClGetTerminationStatusRequest:
 277       have_to_reply =
 278           HandleGetTerminationStatusRequest(input_iter, &write_pickle);
 279       break;
 280     default:
 281       LOG(ERROR) << "Unsupported command from Zygote";
 282       return false;
 283   }
 284   if (!have_to_reply)
 285     return false;
 286   const std::vector<int> empty;  // We never send file descriptors back.
 287   if (!UnixDomainSocket::SendMsg(reply_fd, write_pickle.data(),
 288                                  write_pickle.size(), empty)) {
 289     LOG(ERROR) << "*** send() to zygote failed";
 290     return false;
 291   }
 292   return true;
 293 }
 294
 295 // Read a request from the Zygote from |zygote_ipc_fd| and handle it.
 296 // Die on EOF from |zygote_ipc_fd|.
 297 bool HandleZygoteRequest(int zygote_ipc_fd,
 298                          const NaClLoaderSystemInfo& system_info,
 299                          nacl::NaClSandbox* nacl_sandbox) {
 300   ScopedVector<base::ScopedFD> fds;
 301   char buf[kNaClMaxIPCMessageLength];
 302   const ssize_t msglen = UnixDomainSocket::RecvMsg(zygote_ipc_fd,
 303       &buf, sizeof(buf), &fds);
 304 #if !defined(OS_NACL_NONSFI)
 305   // Currently sandbox is disabled for nacl_helper_nonsfi.
 306   // TODO(hidehiko): Enable sandbox.
 307   // If the Zygote has started handling requests, we should be sandboxed via
 308   // the setuid sandbox.
 309   if (!nacl_sandbox->layer_one_enabled()) {
 310     LOG(ERROR) << "NaCl helper process running without a sandbox!\n"
 311       << "Most likely you need to configure your SUID sandbox "
 312       << "correctly";
 313   }
 314 #endif
 315   if (msglen == 0 || (msglen == -1 && errno == ECONNRESET)) {
 316     // EOF from the browser. Goodbye!
 317     _exit(0);
 318   }
 319   if (msglen < 0) {
 320     PLOG(ERROR) << "nacl_helper: receive from zygote failed";
 321     return false;
 322   }
 323
 324   Pickle read_pickle(buf, msglen);
 325   PickleIterator read_iter(read_pickle);
 326   int command_type;
 327   if (!read_iter.ReadInt(&command_type)) {
 328     LOG(ERROR) << "Unable to read command from Zygote";
 329     return false;
 330   }
 331   return HonorRequestAndReply(zygote_ipc_fd,
 332                               command_type,
 333                               fds.Pass(),
 334                               system_info,
 335                               nacl_sandbox,
 336                               &read_iter);
 337 }
 338
 339 #if !defined(OS_NACL_NONSFI)
 340 static const char kNaClHelperReservedAtZero[] = "reserved_at_zero";
 341 static const char kNaClHelperRDebug[] = "r_debug";
 342
 343 // Since we were started by nacl_helper_bootstrap rather than in the
 344 // usual way, the debugger cannot figure out where our executable
 345 // or the dynamic linker or the shared libraries are in memory,
 346 // so it won't find any symbols.  But we can fake it out to find us.
 347 //
 348 // The zygote passes --r_debug=0xXXXXXXXXXXXXXXXX.
 349 // nacl_helper_bootstrap replaces the Xs with the address of its _r_debug
 350 // structure.  The debugger will look for that symbol by name to
 351 // discover the addresses of key dynamic linker data structures.
 352 // Since all it knows about is the original main executable, which
 353 // is the bootstrap program, it finds the symbol defined there.  The
 354 // dynamic linker's structure is somewhere else, but it is filled in
 355 // after initialization.  The parts that really matter to the
 356 // debugger never change.  So we just copy the contents of the
 357 // dynamic linker's structure into the address provided by the option.
 358 // Hereafter, if someone attaches a debugger (or examines a core dump),
 359 // the debugger will find all the symbols in the normal way.
 360 //
 361 // Non-SFI mode does not use nacl_helper_bootstrap, so it doesn't need to
 362 // process the --r_debug option.
 363 static void CheckRDebug(char* argv0) {
 364   std::string r_debug_switch_value =
 365       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 366           kNaClHelperRDebug);
 367   if (!r_debug_switch_value.empty()) {
 368     char* endp;
 369     uintptr_t r_debug_addr = strtoul(r_debug_switch_value.c_str(), &endp, 0);
 370     if (r_debug_addr != 0 && *endp == '\0') {
 371       r_debug* bootstrap_r_debug = reinterpret_cast<r_debug*>(r_debug_addr);
 372       *bootstrap_r_debug = _r_debug;
 373
 374       // Since the main executable (the bootstrap program) does not
 375       // have a dynamic section, the debugger will not skip the
 376       // first element of the link_map list as it usually would for
 377       // an executable or PIE that was loaded normally.  But the
 378       // dynamic linker has set l_name for the PIE to "" as is
 379       // normal for the main executable.  So the debugger doesn't
 380       // know which file it is.  Fill in the actual file name, which
 381       // came in as our argv[0].
 382       link_map* l = _r_debug.r_map;
 383       if (l->l_name[0] == '\0')
 384         l->l_name = argv0;
 385     }
 386   }
 387 }
 388
 389 // The zygote passes --reserved_at_zero=0xXXXXXXXXXXXXXXXX.
 390 // nacl_helper_bootstrap replaces the Xs with the amount of prereserved
 391 // sandbox memory.
 392 //
 393 // CheckReservedAtZero parses the value of the argument reserved_at_zero
 394 // and returns the amount of prereserved sandbox memory.
 395 static size_t CheckReservedAtZero() {
 396   size_t prereserved_sandbox_size = 0;
 397   std::string reserved_at_zero_switch_value =
 398       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 399           kNaClHelperReservedAtZero);
 400   if (!reserved_at_zero_switch_value.empty()) {
 401     char* endp;
 402     prereserved_sandbox_size =
 403         strtoul(reserved_at_zero_switch_value.c_str(), &endp, 0);
 404     if (*endp != '\0')
 405       LOG(ERROR) << "Could not parse reserved_at_zero argument value of "
 406                  << reserved_at_zero_switch_value;
 407   }
 408   return prereserved_sandbox_size;
 409 }
 410 #endif
 411
 412 }  // namespace
 413
 414 #if defined(ADDRESS_SANITIZER)
 415 // Do not install the SIGSEGV handler in ASan. This should make the NaCl
 416 // platform qualification test pass.
 417 static const char kAsanDefaultOptionsNaCl[] = "handle_segv=0";
 418
 419 // Override the default ASan options for the NaCl helper.
 420 // __asan_default_options should not be instrumented, because it is called
 421 // before ASan is initialized.
 422 extern "C"
 423 __attribute__((no_sanitize_address))
 424 // The function isn't referenced from the executable itself. Make sure it isn't
 425 // stripped by the linker.
 426 __attribute__((used))
 427 __attribute__((visibility("default")))
 428 const char* __asan_default_options() {
 429   return kAsanDefaultOptionsNaCl;
 430 }
 431 #endif
 432
 433 int main(int argc, char* argv[]) {
 434   base::CommandLine::Init(argc, argv);
 435   base::AtExitManager exit_manager;
 436   base::RandUint64();  // acquire /dev/urandom fd before sandbox is raised
 437
 438 #if !defined(OS_NACL_NONSFI)
 439   // NSS is only needed for SFI NaCl.
 440   // Allows NSS to fopen() /dev/urandom.
 441   sandbox::InitLibcUrandomOverrides();
 442 #if defined(USE_NSS)
 443   // Configure NSS for use inside the NaCl process.
 444   // The fork check has not caused problems for NaCl, but this appears to be
 445   // best practice (see other places LoadNSSLibraries is called.)
 446   crypto::DisableNSSForkCheck();
 447   // Without this line on Linux, HMAC::Init will instantiate a singleton that
 448   // in turn attempts to open a file.  Disabling this behavior avoids a ~70 ms
 449   // stall the first time HMAC is used.
 450   crypto::ForceNSSNoDBInit();
 451   // Load shared libraries before sandbox is raised.
 452   // NSS is needed to perform hashing for validation caching.
 453   crypto::LoadNSSLibraries();
 454 #endif  // defined(USE_NSS)
 455 #endif  // defined(OS_NACL_NONSFI)
 456   const NaClLoaderSystemInfo system_info = {
 457 #if !defined(OS_NACL_NONSFI)
 458     // These are not used by nacl_helper_nonsfi.
 459     CheckReservedAtZero(),
 460     sysconf(_SC_NPROCESSORS_ONLN)
 461 #endif
 462   };
 463
 464 #if !defined(OS_NACL_NONSFI)
 465   CheckRDebug(argv[0]);
 466 #endif
 467
 468 #if defined(OS_NACL_NONSFI)
 469   // Currently sandbox is disabled for nacl_helper_nonsfi.
 470   // TODO(hidehiko): Enable sandbox.
 471   scoped_ptr<nacl::NaClSandbox> nacl_sandbox;
 472 #else
 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 #endif  // defined(OS_NACL_NONSFI)
 484
 485   const std::vector<int> empty;
 486   // Send the zygote a message to let it know we are ready to help
 487   if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor,
 488                                  kNaClHelperStartupAck,
 489                                  sizeof(kNaClHelperStartupAck), empty)) {
 490     LOG(ERROR) << "*** send() to zygote failed";
 491   }
 492
 493   // Now handle requests from the Zygote.
 494   while (true) {
 495     bool request_handled = HandleZygoteRequest(
 496         kNaClZygoteDescriptor, system_info, nacl_sandbox.get());
 497     // Do not turn this into a CHECK() without thinking about robustness
 498     // against malicious IPC requests.
 499     DCHECK(request_handled);
 500   }
 501   NOTREACHED();
 502 }