sandbox/win/src/broker_services.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 "sandbox/win/src/broker_services.h"
   6
   7 #include <AclAPI.h>
   8
   9 #include "base/logging.h"
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/threading/platform_thread.h"
  12 #include "base/win/scoped_handle.h"
  13 #include "base/win/scoped_process_information.h"
  14 #include "base/win/startup_information.h"
  15 #include "base/win/windows_version.h"
  16 #include "sandbox/win/src/app_container.h"
  17 #include "sandbox/win/src/process_mitigations.h"
  18 #include "sandbox/win/src/sandbox_policy_base.h"
  19 #include "sandbox/win/src/sandbox.h"
  20 #include "sandbox/win/src/target_process.h"
  21 #include "sandbox/win/src/win2k_threadpool.h"
  22 #include "sandbox/win/src/win_utils.h"
  23
  24 namespace {
  25
  26 // Utility function to associate a completion port to a job object.
  27 bool AssociateCompletionPort(HANDLE job, HANDLE port, void* key) {
  28   JOBOBJECT_ASSOCIATE_COMPLETION_PORT job_acp = { key, port };
  29   return ::SetInformationJobObject(job,
  30                                    JobObjectAssociateCompletionPortInformation,
  31                                    &job_acp, sizeof(job_acp))? true : false;
  32 }
  33
  34 // Utility function to do the cleanup necessary when something goes wrong
  35 // while in SpawnTarget and we must terminate the target process.
  36 sandbox::ResultCode SpawnCleanup(sandbox::TargetProcess* target, DWORD error) {
  37   if (0 == error)
  38     error = ::GetLastError();
  39
  40   target->Terminate();
  41   delete target;
  42   ::SetLastError(error);
  43   return sandbox::SBOX_ERROR_GENERIC;
  44 }
  45
  46 // the different commands that you can send to the worker thread that
  47 // executes TargetEventsThread().
  48 enum {
  49   THREAD_CTRL_NONE,
  50   THREAD_CTRL_REMOVE_PEER,
  51   THREAD_CTRL_QUIT,
  52   THREAD_CTRL_LAST,
  53 };
  54
  55 // Helper structure that allows the Broker to associate a job notification
  56 // with a job object and with a policy.
  57 struct JobTracker {
  58   HANDLE job;
  59   sandbox::PolicyBase* policy;
  60   JobTracker(HANDLE cjob, sandbox::PolicyBase* cpolicy)
  61       : job(cjob), policy(cpolicy) {
  62   }
  63 };
  64
  65 // Helper structure that allows the broker to track peer processes
  66 struct PeerTracker {
  67   HANDLE wait_object;
  68   base::win::ScopedHandle process;
  69   DWORD id;
  70   HANDLE job_port;
  71   PeerTracker(DWORD process_id, HANDLE broker_job_port)
  72       : wait_object(NULL), id(process_id), job_port(broker_job_port) {
  73   }
  74 };
  75
  76 void DeregisterPeerTracker(PeerTracker* peer) {
  77   // Deregistration shouldn't fail, but we leak rather than crash if it does.
  78   if (::UnregisterWaitEx(peer->wait_object, INVALID_HANDLE_VALUE)) {
  79     delete peer;
  80   } else {
  81     NOTREACHED();
  82   }
  83 }
  84
  85 // Utility function to determine whether a token for the specified policy can
  86 // be cached.
  87 bool IsTokenCacheable(const sandbox::PolicyBase* policy) {
  88   const sandbox::AppContainerAttributes* app_container =
  89       policy->GetAppContainer();
  90
  91   // We cannot cache tokens with an app container.
  92   if (app_container)
  93     return false;
  94
  95   return true;
  96 }
  97
  98 // Utility function to pack token values into a key for the cache map.
  99 uint32_t GenerateTokenCacheKey(const sandbox::PolicyBase* policy) {
 100   const size_t kTokenShift = 3;
 101   uint32_t key;
 102
 103   DCHECK(IsTokenCacheable(policy));
 104
 105   // Make sure our token values aren't too large to pack into the key.
 106   static_assert(sandbox::USER_LAST <= (1 << kTokenShift),
 107                 "TokenLevel too large");
 108   static_assert(sandbox::INTEGRITY_LEVEL_LAST <= (1 << kTokenShift),
 109                 "IntegrityLevel too large");
 110   static_assert(sizeof(key) < (kTokenShift * 3),
 111                 "Token key type too small");
 112
 113   // The key is the enum values shifted to avoid overlap and OR'd together.
 114   key = policy->GetInitialTokenLevel();
 115   key <<= kTokenShift;
 116   key |= policy->GetLockdownTokenLevel();
 117   key <<= kTokenShift;
 118   key |= policy->GetIntegrityLevel();
 119
 120   return key;
 121 }
 122
 123 }  // namespace
 124
 125 namespace sandbox {
 126
 127 BrokerServicesBase::BrokerServicesBase()
 128     : thread_pool_(NULL), job_port_(NULL), no_targets_(NULL),
 129       job_thread_(NULL) {
 130 }
 131
 132 // The broker uses a dedicated worker thread that services the job completion
 133 // port to perform policy notifications and associated cleanup tasks.
 134 ResultCode BrokerServicesBase::Init() {
 135   if ((NULL != job_port_) || (NULL != thread_pool_))
 136     return SBOX_ERROR_UNEXPECTED_CALL;
 137
 138   ::InitializeCriticalSection(&lock_);
 139
 140   job_port_ = ::CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
 141   if (NULL == job_port_)
 142     return SBOX_ERROR_GENERIC;
 143
 144   no_targets_ = ::CreateEventW(NULL, TRUE, FALSE, NULL);
 145
 146   job_thread_ = ::CreateThread(NULL, 0,  // Default security and stack.
 147                                TargetEventsThread, this, NULL, NULL);
 148   if (NULL == job_thread_)
 149     return SBOX_ERROR_GENERIC;
 150
 151   return SBOX_ALL_OK;
 152 }
 153
 154 // The destructor should only be called when the Broker process is terminating.
 155 // Since BrokerServicesBase is a singleton, this is called from the CRT
 156 // termination handlers, if this code lives on a DLL it is called during
 157 // DLL_PROCESS_DETACH in other words, holding the loader lock, so we cannot
 158 // wait for threads here.
 159 BrokerServicesBase::~BrokerServicesBase() {
 160   // If there is no port Init() was never called successfully.
 161   if (!job_port_)
 162     return;
 163
 164   // Closing the port causes, that no more Job notifications are delivered to
 165   // the worker thread and also causes the thread to exit. This is what we
 166   // want to do since we are going to close all outstanding Jobs and notifying
 167   // the policy objects ourselves.
 168   ::PostQueuedCompletionStatus(job_port_, 0, THREAD_CTRL_QUIT, FALSE);
 169   ::CloseHandle(job_port_);
 170
 171   if (WAIT_TIMEOUT == ::WaitForSingleObject(job_thread_, 1000)) {
 172     // Cannot clean broker services.
 173     NOTREACHED();
 174     return;
 175   }
 176
 177   JobTrackerList::iterator it;
 178   for (it = tracker_list_.begin(); it != tracker_list_.end(); ++it) {
 179     JobTracker* tracker = (*it);
 180     FreeResources(tracker);
 181     delete tracker;
 182   }
 183   ::CloseHandle(job_thread_);
 184   delete thread_pool_;
 185   ::CloseHandle(no_targets_);
 186
 187   // Cancel the wait events and delete remaining peer trackers.
 188   for (PeerTrackerMap::iterator it = peer_map_.begin();
 189        it != peer_map_.end(); ++it) {
 190     DeregisterPeerTracker(it->second);
 191   }
 192
 193   // If job_port_ isn't NULL, assumes that the lock has been initialized.
 194   if (job_port_)
 195     ::DeleteCriticalSection(&lock_);
 196
 197   // Close any token in the cache.
 198   for (TokenCacheMap::iterator it = token_cache_.begin();
 199        it != token_cache_.end(); ++it) {
 200     ::CloseHandle(it->second.first);
 201     ::CloseHandle(it->second.second);
 202   }
 203 }
 204
 205 TargetPolicy* BrokerServicesBase::CreatePolicy() {
 206   // If you change the type of the object being created here you must also
 207   // change the downcast to it in SpawnTarget().
 208   return new PolicyBase;
 209 }
 210
 211 void BrokerServicesBase::FreeResources(JobTracker* tracker) {
 212   if (NULL != tracker->policy) {
 213     BOOL res = ::TerminateJobObject(tracker->job, SBOX_ALL_OK);
 214     DCHECK(res);
 215     // Closing the job causes the target process to be destroyed so this
 216     // needs to happen before calling OnJobEmpty().
 217     res = ::CloseHandle(tracker->job);
 218     DCHECK(res);
 219     // In OnJobEmpty() we don't actually use the job handle directly.
 220     tracker->policy->OnJobEmpty(tracker->job);
 221     tracker->policy->Release();
 222     tracker->policy = NULL;
 223   }
 224 }
 225
 226 // The worker thread stays in a loop waiting for asynchronous notifications
 227 // from the job objects. Right now we only care about knowing when the last
 228 // process on a job terminates, but in general this is the place to tell
 229 // the policy about events.
 230 DWORD WINAPI BrokerServicesBase::TargetEventsThread(PVOID param) {
 231   if (NULL == param)
 232     return 1;
 233
 234   base::PlatformThread::SetName("BrokerEvent");
 235
 236   BrokerServicesBase* broker = reinterpret_cast<BrokerServicesBase*>(param);
 237   HANDLE port = broker->job_port_;
 238   HANDLE no_targets = broker->no_targets_;
 239
 240   int target_counter = 0;
 241   ::ResetEvent(no_targets);
 242
 243   while (true) {
 244     DWORD events = 0;
 245     ULONG_PTR key = 0;
 246     LPOVERLAPPED ovl = NULL;
 247
 248     if (!::GetQueuedCompletionStatus(port, &events, &key, &ovl, INFINITE))
 249       // this call fails if the port has been closed before we have a
 250       // chance to service the last packet which is 'exit' anyway so
 251       // this is not an error.
 252       return 1;
 253
 254     if (key > THREAD_CTRL_LAST) {
 255       // The notification comes from a job object. There are nine notifications
 256       // that jobs can send and some of them depend on the job attributes set.
 257       JobTracker* tracker = reinterpret_cast<JobTracker*>(key);
 258
 259       switch (events) {
 260         case JOB_OBJECT_MSG_ACTIVE_PROCESS_ZERO: {
 261           // The job object has signaled that the last process associated
 262           // with it has terminated. Assuming there is no way for a process
 263           // to appear out of thin air in this job, it safe to assume that
 264           // we can tell the policy to destroy the target object, and for
 265           // us to release our reference to the policy object.
 266           FreeResources(tracker);
 267           break;
 268         }
 269
 270         case JOB_OBJECT_MSG_NEW_PROCESS: {
 271           ++target_counter;
 272           if (1 == target_counter) {
 273             ::ResetEvent(no_targets);
 274           }
 275           break;
 276         }
 277
 278         case JOB_OBJECT_MSG_EXIT_PROCESS:
 279         case JOB_OBJECT_MSG_ABNORMAL_EXIT_PROCESS: {
 280           {
 281             AutoLock lock(&broker->lock_);
 282             broker->child_process_ids_.erase(reinterpret_cast<DWORD>(ovl));
 283           }
 284           --target_counter;
 285           if (0 == target_counter)
 286             ::SetEvent(no_targets);
 287
 288           DCHECK(target_counter >= 0);
 289           break;
 290         }
 291
 292         case JOB_OBJECT_MSG_ACTIVE_PROCESS_LIMIT: {
 293           break;
 294         }
 295
 296         case JOB_OBJECT_MSG_PROCESS_MEMORY_LIMIT: {
 297           BOOL res = ::TerminateJobObject(tracker->job,
 298                                           SBOX_FATAL_MEMORY_EXCEEDED);
 299           DCHECK(res);
 300           break;
 301         }
 302
 303         default: {
 304           NOTREACHED();
 305           break;
 306         }
 307       }
 308     } else if (THREAD_CTRL_REMOVE_PEER == key) {
 309       // Remove a process from our list of peers.
 310       AutoLock lock(&broker->lock_);
 311       PeerTrackerMap::iterator it =
 312           broker->peer_map_.find(reinterpret_cast<DWORD>(ovl));
 313       DeregisterPeerTracker(it->second);
 314       broker->peer_map_.erase(it);
 315     } else if (THREAD_CTRL_QUIT == key) {
 316       // The broker object is being destroyed so the thread needs to exit.
 317       return 0;
 318     } else {
 319       // We have not implemented more commands.
 320       NOTREACHED();
 321     }
 322   }
 323
 324   NOTREACHED();
 325   return 0;
 326 }
 327
 328 // SpawnTarget does all the interesting sandbox setup and creates the target
 329 // process inside the sandbox.
 330 ResultCode BrokerServicesBase::SpawnTarget(const wchar_t* exe_path,
 331                                            const wchar_t* command_line,
 332                                            TargetPolicy* policy,
 333                                            PROCESS_INFORMATION* target_info) {
 334   if (!exe_path)
 335     return SBOX_ERROR_BAD_PARAMS;
 336
 337   if (!policy)
 338     return SBOX_ERROR_BAD_PARAMS;
 339
 340   // Even though the resources touched by SpawnTarget can be accessed in
 341   // multiple threads, the method itself cannot be called from more than
 342   // 1 thread. This is to protect the global variables used while setting up
 343   // the child process.
 344   static DWORD thread_id = ::GetCurrentThreadId();
 345   DCHECK(thread_id == ::GetCurrentThreadId());
 346
 347   AutoLock lock(&lock_);
 348
 349   // This downcast is safe as long as we control CreatePolicy()
 350   PolicyBase* policy_base = static_cast<PolicyBase*>(policy);
 351
 352   // Construct the tokens and the job object that we are going to associate
 353   // with the soon to be created target process.
 354   HANDLE initial_token_temp;
 355   HANDLE lockdown_token_temp;
 356   ResultCode result = SBOX_ALL_OK;
 357
 358   if (IsTokenCacheable(policy_base)) {
 359     // Create the master tokens only once and save them in a cache. That way
 360     // can just duplicate them to avoid hammering LSASS on every sandboxed
 361     // process launch.
 362     uint32_t token_key = GenerateTokenCacheKey(policy_base);
 363     TokenCacheMap::iterator it = token_cache_.find(token_key);
 364     if (it != token_cache_.end()) {
 365       initial_token_temp = it->second.first;
 366       lockdown_token_temp = it->second.second;
 367     } else {
 368       result =
 369           policy_base->MakeTokens(&initial_token_temp, &lockdown_token_temp);
 370       if (SBOX_ALL_OK != result)
 371         return result;
 372       token_cache_[token_key] =
 373           std::pair<HANDLE, HANDLE>(initial_token_temp, lockdown_token_temp);
 374     }
 375
 376     if (!::DuplicateToken(initial_token_temp, SecurityImpersonation,
 377                           &initial_token_temp)) {
 378       return SBOX_ERROR_GENERIC;
 379     }
 380
 381     if (!::DuplicateTokenEx(lockdown_token_temp, TOKEN_ALL_ACCESS, 0,
 382                             SecurityIdentification, TokenPrimary,
 383                             &lockdown_token_temp)) {
 384       return SBOX_ERROR_GENERIC;
 385     }
 386   } else {
 387     result = policy_base->MakeTokens(&initial_token_temp, &lockdown_token_temp);
 388     if (SBOX_ALL_OK != result)
 389       return result;
 390   }
 391
 392   base::win::ScopedHandle initial_token(initial_token_temp);
 393   base::win::ScopedHandle lockdown_token(lockdown_token_temp);
 394
 395   HANDLE job_temp;
 396   result = policy_base->MakeJobObject(&job_temp);
 397   if (SBOX_ALL_OK != result)
 398     return result;
 399
 400   base::win::ScopedHandle job(job_temp);
 401
 402   // Initialize the startup information from the policy.
 403   base::win::StartupInformation startup_info;
 404   base::string16 desktop = policy_base->GetAlternateDesktop();
 405   if (!desktop.empty()) {
 406     startup_info.startup_info()->lpDesktop =
 407         const_cast<wchar_t*>(desktop.c_str());
 408   }
 409
 410   bool inherit_handles = false;
 411   if (base::win::GetVersion() >= base::win::VERSION_VISTA) {
 412     int attribute_count = 0;
 413     const AppContainerAttributes* app_container =
 414         policy_base->GetAppContainer();
 415     if (app_container)
 416       ++attribute_count;
 417
 418     DWORD64 mitigations;
 419     size_t mitigations_size;
 420     ConvertProcessMitigationsToPolicy(policy->GetProcessMitigations(),
 421                                       &mitigations, &mitigations_size);
 422     if (mitigations)
 423       ++attribute_count;
 424
 425     HANDLE stdout_handle = policy_base->GetStdoutHandle();
 426     HANDLE stderr_handle = policy_base->GetStderrHandle();
 427     HANDLE inherit_handle_list[2];
 428     int inherit_handle_count = 0;
 429     if (stdout_handle != INVALID_HANDLE_VALUE)
 430       inherit_handle_list[inherit_handle_count++] = stdout_handle;
 431     // Handles in the list must be unique.
 432     if (stderr_handle != stdout_handle && stderr_handle != INVALID_HANDLE_VALUE)
 433       inherit_handle_list[inherit_handle_count++] = stderr_handle;
 434     if (inherit_handle_count)
 435       ++attribute_count;
 436
 437     if (!startup_info.InitializeProcThreadAttributeList(attribute_count))
 438       return SBOX_ERROR_PROC_THREAD_ATTRIBUTES;
 439
 440     if (app_container) {
 441       result = app_container->ShareForStartup(&startup_info);
 442       if (SBOX_ALL_OK != result)
 443         return result;
 444     }
 445
 446     if (mitigations) {
 447       if (!startup_info.UpdateProcThreadAttribute(
 448                PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY, &mitigations,
 449                mitigations_size)) {
 450         return SBOX_ERROR_PROC_THREAD_ATTRIBUTES;
 451       }
 452     }
 453
 454     if (inherit_handle_count) {
 455       if (!startup_info.UpdateProcThreadAttribute(
 456               PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
 457               inherit_handle_list,
 458               sizeof(inherit_handle_list[0]) * inherit_handle_count)) {
 459         return SBOX_ERROR_PROC_THREAD_ATTRIBUTES;
 460       }
 461       startup_info.startup_info()->dwFlags |= STARTF_USESTDHANDLES;
 462       startup_info.startup_info()->hStdInput = INVALID_HANDLE_VALUE;
 463       startup_info.startup_info()->hStdOutput = stdout_handle;
 464       startup_info.startup_info()->hStdError = stderr_handle;
 465       // Allowing inheritance of handles is only secure now that we
 466       // have limited which handles will be inherited.
 467       inherit_handles = true;
 468     }
 469   }
 470
 471   // Construct the thread pool here in case it is expensive.
 472   // The thread pool is shared by all the targets
 473   if (NULL == thread_pool_)
 474     thread_pool_ = new Win2kThreadPool();
 475
 476   // Create the TargetProces object and spawn the target suspended. Note that
 477   // Brokerservices does not own the target object. It is owned by the Policy.
 478   base::win::ScopedProcessInformation process_info;
 479   TargetProcess* target = new TargetProcess(initial_token.Take(),
 480                                             lockdown_token.Take(),
 481                                             job.Get(),
 482                                             thread_pool_);
 483
 484   DWORD win_result = target->Create(exe_path, command_line, inherit_handles,
 485                                     startup_info, &process_info);
 486   if (ERROR_SUCCESS != win_result)
 487     return SpawnCleanup(target, win_result);
 488
 489   // Now the policy is the owner of the target.
 490   if (!policy_base->AddTarget(target)) {
 491     return SpawnCleanup(target, 0);
 492   }
 493
 494   // We are going to keep a pointer to the policy because we'll call it when
 495   // the job object generates notifications using the completion port.
 496   policy_base->AddRef();
 497   if (job.IsValid()) {
 498     scoped_ptr<JobTracker> tracker(new JobTracker(job.Take(), policy_base));
 499     if (!AssociateCompletionPort(tracker->job, job_port_, tracker.get()))
 500       return SpawnCleanup(target, 0);
 501     // Save the tracker because in cleanup we might need to force closing
 502     // the Jobs.
 503     tracker_list_.push_back(tracker.release());
 504     child_process_ids_.insert(process_info.process_id());
 505   } else {
 506     // We have to signal the event once here because the completion port will
 507     // never get a message that this target is being terminated thus we should
 508     // not block WaitForAllTargets until we have at least one target with job.
 509     if (child_process_ids_.empty())
 510       ::SetEvent(no_targets_);
 511     // We can not track the life time of such processes and it is responsibility
 512     // of the host application to make sure that spawned targets without jobs
 513     // are terminated when the main application don't need them anymore.
 514   }
 515
 516   *target_info = process_info.Take();
 517   return SBOX_ALL_OK;
 518 }
 519
 520
 521 ResultCode BrokerServicesBase::WaitForAllTargets() {
 522   ::WaitForSingleObject(no_targets_, INFINITE);
 523   return SBOX_ALL_OK;
 524 }
 525
 526 bool BrokerServicesBase::IsActiveTarget(DWORD process_id) {
 527   AutoLock lock(&lock_);
 528   return child_process_ids_.find(process_id) != child_process_ids_.end() ||
 529          peer_map_.find(process_id) != peer_map_.end();
 530 }
 531
 532 VOID CALLBACK BrokerServicesBase::RemovePeer(PVOID parameter, BOOLEAN timeout) {
 533   PeerTracker* peer = reinterpret_cast<PeerTracker*>(parameter);
 534   // Don't check the return code because we this may fail (safely) at shutdown.
 535   ::PostQueuedCompletionStatus(peer->job_port, 0, THREAD_CTRL_REMOVE_PEER,
 536                                reinterpret_cast<LPOVERLAPPED>(peer->id));
 537 }
 538
 539 ResultCode BrokerServicesBase::AddTargetPeer(HANDLE peer_process) {
 540   scoped_ptr<PeerTracker> peer(new PeerTracker(::GetProcessId(peer_process),
 541                                                job_port_));
 542   if (!peer->id)
 543     return SBOX_ERROR_GENERIC;
 544
 545   HANDLE process_handle;
 546   if (!::DuplicateHandle(::GetCurrentProcess(), peer_process,
 547                          ::GetCurrentProcess(), &process_handle,
 548                          SYNCHRONIZE, FALSE, 0)) {
 549     return SBOX_ERROR_GENERIC;
 550   }
 551   peer->process.Set(process_handle);
 552
 553   AutoLock lock(&lock_);
 554   if (!peer_map_.insert(std::make_pair(peer->id, peer.get())).second)
 555     return SBOX_ERROR_BAD_PARAMS;
 556
 557   if (!::RegisterWaitForSingleObject(
 558           &peer->wait_object, peer->process.Get(), RemovePeer, peer.get(),
 559           INFINITE, WT_EXECUTEONLYONCE | WT_EXECUTEINWAITTHREAD)) {
 560     peer_map_.erase(peer->id);
 561     return SBOX_ERROR_GENERIC;
 562   }
 563
 564   // Release the pointer since it will be cleaned up by the callback.
 565   peer.release();
 566   return SBOX_ALL_OK;
 567 }
 568
 569 ResultCode BrokerServicesBase::InstallAppContainer(const wchar_t* sid,
 570                                                    const wchar_t* name) {
 571   if (base::win::OSInfo::GetInstance()->version() < base::win::VERSION_WIN8)
 572     return SBOX_ERROR_UNSUPPORTED;
 573
 574   base::string16 old_name = LookupAppContainer(sid);
 575   if (old_name.empty())
 576     return CreateAppContainer(sid, name);
 577
 578   if (old_name != name)
 579     return SBOX_ERROR_INVALID_APP_CONTAINER;
 580
 581   return SBOX_ALL_OK;
 582 }
 583
 584 ResultCode BrokerServicesBase::UninstallAppContainer(const wchar_t* sid) {
 585   if (base::win::OSInfo::GetInstance()->version() < base::win::VERSION_WIN8)
 586     return SBOX_ERROR_UNSUPPORTED;
 587
 588   base::string16 name = LookupAppContainer(sid);
 589   if (name.empty())
 590     return SBOX_ERROR_INVALID_APP_CONTAINER;
 591
 592   return DeleteAppContainer(sid);
 593 }
 594
 595 }  // namespace sandbox