content/common/sandbox_linux/sandbox_linux.cc

   1 // Copyright (c) 2012 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 #include <dirent.h>
   6 #include <fcntl.h>
   7 #include <sys/resource.h>
   8 #include <sys/stat.h>
   9 #include <sys/time.h>
  10 #include <sys/types.h>
  11 #include <unistd.h>
  12
  13 #include <limits>
  14
  15 #include "base/bind.h"
  16 #include "base/callback_helpers.h"
  17 #include "base/command_line.h"
  18 #include "base/debug/stack_trace.h"
  19 #include "base/files/scoped_file.h"
  20 #include "base/logging.h"
  21 #include "base/memory/scoped_ptr.h"
  22 #include "base/memory/singleton.h"
  23 #include "base/posix/eintr_wrapper.h"
  24 #include "base/strings/string_number_conversions.h"
  25 #include "base/sys_info.h"
  26 #include "base/time/time.h"
  27 #include "build/build_config.h"
  28 #include "content/common/sandbox_linux/sandbox_linux.h"
  29 #include "content/common/sandbox_linux/sandbox_seccomp_bpf_linux.h"
  30 #include "content/public/common/content_switches.h"
  31 #include "content/public/common/sandbox_linux.h"
  32 #include "sandbox/linux/services/credentials.h"
  33 #include "sandbox/linux/services/thread_helpers.h"
  34 #include "sandbox/linux/services/yama.h"
  35 #include "sandbox/linux/suid/client/setuid_sandbox_client.h"
  36
  37 #if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
  38      defined(LEAK_SANITIZER) || defined(UNDEFINED_SANITIZER)
  39 #include <sanitizer/common_interface_defs.h>
  40 #endif
  41
  42 using sandbox::Yama;
  43
  44 namespace {
  45
  46 struct FDCloser {
  47   inline void operator()(int* fd) const {
  48     DCHECK(fd);
  49     PCHECK(0 == IGNORE_EINTR(close(*fd)));
  50     *fd = -1;
  51   }
  52 };
  53
  54 void LogSandboxStarted(const std::string& sandbox_name) {
  55   const base::CommandLine& command_line =
  56       *base::CommandLine::ForCurrentProcess();
  57   const std::string process_type =
  58       command_line.GetSwitchValueASCII(switches::kProcessType);
  59   const std::string activated_sandbox =
  60       "Activated " + sandbox_name + " sandbox for process type: " +
  61       process_type + ".";
  62   VLOG(1) << activated_sandbox;
  63 }
  64
  65 #if !defined(ADDRESS_SANITIZER) && !defined(MEMORY_SANITIZER)
  66 bool AddResourceLimit(int resource, rlim_t limit) {
  67   struct rlimit old_rlimit;
  68   if (getrlimit(resource, &old_rlimit))
  69     return false;
  70   // Make sure we don't raise the existing limit.
  71   const struct rlimit new_rlimit = {
  72       std::min(old_rlimit.rlim_cur, limit),
  73       std::min(old_rlimit.rlim_max, limit)
  74       };
  75   int rc = setrlimit(resource, &new_rlimit);
  76   return rc == 0;
  77 }
  78 #endif
  79
  80 bool IsRunningTSAN() {
  81 #if defined(THREAD_SANITIZER)
  82   return true;
  83 #else
  84   return false;
  85 #endif
  86 }
  87
  88 // Try to open /proc/self/task/ with the help of |proc_fd|. |proc_fd| can be
  89 // -1. Will return -1 on error and set errno like open(2).
  90 int OpenProcTaskFd(int proc_fd) {
  91   int proc_self_task = -1;
  92   if (proc_fd >= 0) {
  93     // If a handle to /proc is available, use it. This allows to bypass file
  94     // system restrictions.
  95     proc_self_task = openat(proc_fd, "self/task/", O_RDONLY | O_DIRECTORY);
  96   } else {
  97     // Otherwise, make an attempt to access the file system directly.
  98     proc_self_task = open("/proc/self/task/", O_RDONLY | O_DIRECTORY);
  99   }
 100   return proc_self_task;
 101 }
 102
 103 }  // namespace
 104
 105 namespace content {
 106
 107 LinuxSandbox::LinuxSandbox()
 108     : proc_fd_(-1),
 109       seccomp_bpf_started_(false),
 110       sandbox_status_flags_(kSandboxLinuxInvalid),
 111       pre_initialized_(false),
 112       seccomp_bpf_supported_(false),
 113       yama_is_enforcing_(false),
 114       setuid_sandbox_client_(sandbox::SetuidSandboxClient::Create())
 115 {
 116   if (setuid_sandbox_client_ == NULL) {
 117     LOG(FATAL) << "Failed to instantiate the setuid sandbox client.";
 118   }
 119 #if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
 120      defined(LEAK_SANITIZER) || defined(UNDEFINED_SANITIZER)
 121   sanitizer_args_ = make_scoped_ptr(new __sanitizer_sandbox_arguments);
 122   *sanitizer_args_ = {0};
 123 #endif
 124 }
 125
 126 LinuxSandbox::~LinuxSandbox() {
 127 }
 128
 129 LinuxSandbox* LinuxSandbox::GetInstance() {
 130   LinuxSandbox* instance = Singleton<LinuxSandbox>::get();
 131   CHECK(instance);
 132   return instance;
 133 }
 134
 135 void LinuxSandbox::PreinitializeSandbox() {
 136   CHECK(!pre_initialized_);
 137   seccomp_bpf_supported_ = false;
 138 #if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
 139     defined(LEAK_SANITIZER) || defined(UNDEFINED_SANITIZER)
 140   // Sanitizers need to open some resources before the sandbox is enabled.
 141   // This should not fork, not launch threads, not open a directory.
 142   __sanitizer_sandbox_on_notify(sanitizer_args());
 143   sanitizer_args_.reset();
 144 #endif
 145
 146 #if !defined(NDEBUG)
 147   // The in-process stack dumping needs to open /proc/self/maps and cache
 148   // its contents before the sandbox is enabled.  It also pre-opens the
 149   // object files that are already loaded in the process address space.
 150   base::debug::EnableInProcessStackDumpingForSandbox();
 151
 152   // Open proc_fd_ only in Debug mode so that forgetting to close it doesn't
 153   // produce a sandbox escape in Release mode.
 154   proc_fd_ = open("/proc", O_DIRECTORY | O_RDONLY | O_CLOEXEC);
 155   CHECK_GE(proc_fd_, 0);
 156 #endif  // !defined(NDEBUG)
 157   // We "pre-warm" the code that detects supports for seccomp BPF.
 158   if (SandboxSeccompBPF::IsSeccompBPFDesired()) {
 159     if (!SandboxSeccompBPF::SupportsSandbox()) {
 160       VLOG(1) << "Lacking support for seccomp-bpf sandbox.";
 161     } else {
 162       seccomp_bpf_supported_ = true;
 163     }
 164   }
 165
 166   // Yama is a "global", system-level status. We assume it will not regress
 167   // after startup.
 168   const int yama_status = Yama::GetStatus();
 169   yama_is_enforcing_ = (yama_status & Yama::STATUS_PRESENT) &&
 170                        (yama_status & Yama::STATUS_ENFORCING);
 171   pre_initialized_ = true;
 172 }
 173
 174 bool LinuxSandbox::InitializeSandbox() {
 175   LinuxSandbox* linux_sandbox = LinuxSandbox::GetInstance();
 176   return linux_sandbox->InitializeSandboxImpl();
 177 }
 178
 179 void LinuxSandbox::StopThread(base::Thread* thread) {
 180   LinuxSandbox* linux_sandbox = LinuxSandbox::GetInstance();
 181   linux_sandbox->StopThreadImpl(thread);
 182 }
 183
 184 int LinuxSandbox::GetStatus() {
 185   CHECK(pre_initialized_);
 186   if (kSandboxLinuxInvalid == sandbox_status_flags_) {
 187     // Initialize sandbox_status_flags_.
 188     sandbox_status_flags_ = 0;
 189     if (setuid_sandbox_client_->IsSandboxed()) {
 190       sandbox_status_flags_ |= kSandboxLinuxSUID;
 191       if (setuid_sandbox_client_->IsInNewPIDNamespace())
 192         sandbox_status_flags_ |= kSandboxLinuxPIDNS;
 193       if (setuid_sandbox_client_->IsInNewNETNamespace())
 194         sandbox_status_flags_ |= kSandboxLinuxNetNS;
 195     }
 196
 197     // We report whether the sandbox will be activated when renderers, workers
 198     // and PPAPI plugins go through sandbox initialization.
 199     if (seccomp_bpf_supported() &&
 200         SandboxSeccompBPF::ShouldEnableSeccompBPF(switches::kRendererProcess)) {
 201       sandbox_status_flags_ |= kSandboxLinuxSeccompBPF;
 202     }
 203
 204     if (yama_is_enforcing_) {
 205       sandbox_status_flags_ |= kSandboxLinuxYama;
 206     }
 207   }
 208
 209   return sandbox_status_flags_;
 210 }
 211
 212 // Threads are counted via /proc/self/task. This is a little hairy because of
 213 // PID namespaces and existing sandboxes, so "self" must really be used instead
 214 // of using the pid.
 215 bool LinuxSandbox::IsSingleThreaded() const {
 216   bool is_single_threaded = false;
 217   base::ScopedFD proc_self_task(OpenProcTaskFd(proc_fd_));
 218
 219 // In Debug mode, it's mandatory to be able to count threads to catch bugs.
 220 #if !defined(NDEBUG)
 221   // Using CHECK here since we want to check all the cases where
 222   // !defined(NDEBUG)
 223   // gets built.
 224   CHECK(proc_self_task.is_valid())
 225       << "Could not count threads, the sandbox was not "
 226       << "pre-initialized properly.";
 227 #endif  // !defined(NDEBUG)
 228
 229   if (!proc_self_task.is_valid()) {
 230     // Pretend to be monothreaded if it can't be determined (for instance the
 231     // setuid sandbox is already engaged but no proc_fd_ is available).
 232     is_single_threaded = true;
 233   } else {
 234     is_single_threaded =
 235         sandbox::ThreadHelpers::IsSingleThreaded(proc_self_task.get());
 236   }
 237
 238   return is_single_threaded;
 239 }
 240
 241 bool LinuxSandbox::seccomp_bpf_started() const {
 242   return seccomp_bpf_started_;
 243 }
 244
 245 sandbox::SetuidSandboxClient*
 246     LinuxSandbox::setuid_sandbox_client() const {
 247   return setuid_sandbox_client_.get();
 248 }
 249
 250 // For seccomp-bpf, we use the SandboxSeccompBPF class.
 251 bool LinuxSandbox::StartSeccompBPF(const std::string& process_type) {
 252   CHECK(!seccomp_bpf_started_);
 253   CHECK(pre_initialized_);
 254   if (seccomp_bpf_supported())
 255     seccomp_bpf_started_ = SandboxSeccompBPF::StartSandbox(process_type);
 256
 257   if (seccomp_bpf_started_)
 258     LogSandboxStarted("seccomp-bpf");
 259
 260   return seccomp_bpf_started_;
 261 }
 262
 263 bool LinuxSandbox::InitializeSandboxImpl() {
 264   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
 265   const std::string process_type =
 266       command_line->GetSwitchValueASCII(switches::kProcessType);
 267
 268   // We need to make absolutely sure that our sandbox is "sealed" before
 269   // returning.
 270   // Unretained() since the current object is a Singleton.
 271   base::ScopedClosureRunner sandbox_sealer(
 272       base::Bind(&LinuxSandbox::SealSandbox, base::Unretained(this)));
 273   // Make sure that this function enables sandboxes as promised by GetStatus().
 274   // Unretained() since the current object is a Singleton.
 275   base::ScopedClosureRunner sandbox_promise_keeper(
 276       base::Bind(&LinuxSandbox::CheckForBrokenPromises,
 277                  base::Unretained(this),
 278                  process_type));
 279
 280   // No matter what, it's always an error to call InitializeSandbox() after
 281   // threads have been created.
 282   if (!IsSingleThreaded()) {
 283     std::string error_message = "InitializeSandbox() called with multiple "
 284                                 "threads in process " + process_type;
 285     // TSAN starts a helper thread, so we don't start the sandbox and don't
 286     // even report an error about it.
 287     if (IsRunningTSAN())
 288       return false;
 289
 290     // The GPU process is allowed to call InitializeSandbox() with threads.
 291     bool sandbox_failure_fatal = process_type != switches::kGpuProcess;
 292     // This can be disabled with the '--gpu-sandbox-failures-fatal' flag.
 293     // Setting the flag with no value or any value different than 'yes' or 'no'
 294     // is equal to setting '--gpu-sandbox-failures-fatal=yes'.
 295     if (process_type == switches::kGpuProcess &&
 296         command_line->HasSwitch(switches::kGpuSandboxFailuresFatal)) {
 297       const std::string switch_value =
 298           command_line->GetSwitchValueASCII(switches::kGpuSandboxFailuresFatal);
 299       sandbox_failure_fatal = switch_value != "no";
 300     }
 301
 302     if (sandbox_failure_fatal)
 303       LOG(FATAL) << error_message;
 304
 305     LOG(ERROR) << error_message;
 306     return false;
 307   }
 308
 309   // Only one thread is running, pre-initialize if not already done.
 310   if (!pre_initialized_)
 311     PreinitializeSandbox();
 312
 313   DCHECK(!HasOpenDirectories()) <<
 314       "InitializeSandbox() called after unexpected directories have been " <<
 315       "opened. This breaks the security of the setuid sandbox.";
 316
 317   // Attempt to limit the future size of the address space of the process.
 318   LimitAddressSpace(process_type);
 319
 320   // Try to enable seccomp-bpf.
 321   bool seccomp_bpf_started = StartSeccompBPF(process_type);
 322
 323   return seccomp_bpf_started;
 324 }
 325
 326 void LinuxSandbox::StopThreadImpl(base::Thread* thread) {
 327   DCHECK(thread);
 328   StopThreadAndEnsureNotCounted(thread);
 329 }
 330
 331 bool LinuxSandbox::seccomp_bpf_supported() const {
 332   CHECK(pre_initialized_);
 333   return seccomp_bpf_supported_;
 334 }
 335
 336 bool LinuxSandbox::LimitAddressSpace(const std::string& process_type) {
 337   (void) process_type;
 338 #if !defined(ADDRESS_SANITIZER) && !defined(MEMORY_SANITIZER)
 339   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
 340   if (command_line->HasSwitch(switches::kNoSandbox)) {
 341     return false;
 342   }
 343
 344   // Limit the address space to 4GB.
 345   // This is in the hope of making some kernel exploits more complex and less
 346   // reliable. It also limits sprays a little on 64-bit.
 347   rlim_t address_space_limit = std::numeric_limits<uint32_t>::max();
 348 #if defined(__LP64__)
 349   // On 64 bits, V8 and possibly others will reserve massive memory ranges and
 350   // rely on on-demand paging for allocation.  Unfortunately, even
 351   // MADV_DONTNEED ranges  count towards RLIMIT_AS so this is not an option.
 352   // See crbug.com/169327 for a discussion.
 353   // On the GPU process, irrespective of V8, we can exhaust a 4GB address space
 354   // under normal usage, see crbug.com/271119
 355   // For now, increase limit to 16GB for renderer and worker and gpu processes
 356   // to accomodate.
 357   if (process_type == switches::kRendererProcess ||
 358       process_type == switches::kGpuProcess) {
 359     address_space_limit = 1L << 34;
 360   }
 361 #endif  // defined(__LP64__)
 362
 363   // On all platforms, add a limit to the brk() heap that would prevent
 364   // allocations that can't be index by an int.
 365   const rlim_t kNewDataSegmentMaxSize = std::numeric_limits<int>::max();
 366
 367   bool limited_as = AddResourceLimit(RLIMIT_AS, address_space_limit);
 368   bool limited_data = AddResourceLimit(RLIMIT_DATA, kNewDataSegmentMaxSize);
 369
 370   // Cache the resource limit before turning on the sandbox.
 371   base::SysInfo::AmountOfVirtualMemory();
 372
 373   return limited_as && limited_data;
 374 #else
 375   base::SysInfo::AmountOfVirtualMemory();
 376   return false;
 377 #endif  // !defined(ADDRESS_SANITIZER) && !defined(MEMORY_SANITIZER)
 378 }
 379
 380 bool LinuxSandbox::HasOpenDirectories() const {
 381   return sandbox::Credentials().HasOpenDirectory(proc_fd_);
 382 }
 383
 384 void LinuxSandbox::SealSandbox() {
 385   if (proc_fd_ >= 0) {
 386     int ret = IGNORE_EINTR(close(proc_fd_));
 387     CHECK_EQ(0, ret);
 388     proc_fd_ = -1;
 389   }
 390 }
 391
 392 void LinuxSandbox::CheckForBrokenPromises(const std::string& process_type) {
 393   // Make sure that any promise made with GetStatus() wasn't broken.
 394   bool promised_seccomp_bpf_would_start = false;
 395   if (process_type == switches::kRendererProcess ||
 396       process_type == switches::kPpapiPluginProcess) {
 397     promised_seccomp_bpf_would_start =
 398         (sandbox_status_flags_ != kSandboxLinuxInvalid) &&
 399         (GetStatus() & kSandboxLinuxSeccompBPF);
 400   }
 401   if (promised_seccomp_bpf_would_start) {
 402     CHECK(seccomp_bpf_started_);
 403   }
 404 }
 405
 406 void LinuxSandbox::StopThreadAndEnsureNotCounted(base::Thread* thread) const {
 407   DCHECK(thread);
 408   base::ScopedFD proc_self_task(OpenProcTaskFd(proc_fd_));
 409   PCHECK(proc_self_task.is_valid());
 410   CHECK(sandbox::ThreadHelpers::StopThreadAndWatchProcFS(proc_self_task.get(),
 411                                                          thread));
 412 }
 413
 414 }  // namespace content