root/sandbox/win/src/target_services.cc

DEFINITIONS

1. FlushRegKey
2. FlushCachedRegHandles
3. CloseOpenHandles
4. Init
5. LowerToken
6. GetState
7. GetInstance
8. TestIPCPing
9. IsKernel32Loaded
10. InitCalled
11. RevertedToSelf
12. SetKernel32Loaded
13. SetInitCalled
14. SetRevertedToSelf
15. DuplicateHandle

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "sandbox/win/src/target_services.h"

#include <process.h>

#include "base/basictypes.h"
#include "sandbox/win/src/crosscall_client.h"
#include "sandbox/win/src/handle_closer_agent.h"
#include "sandbox/win/src/handle_interception.h"
#include "sandbox/win/src/ipc_tags.h"
#include "sandbox/win/src/process_mitigations.h"
#include "sandbox/win/src/restricted_token_utils.h"
#include "sandbox/win/src/sandbox.h"
#include "sandbox/win/src/sandbox_types.h"
#include "sandbox/win/src/sharedmem_ipc_client.h"
#include "sandbox/win/src/sandbox_nt_util.h"

namespace {

// Flushing a cached key is triggered by just opening the key and closing the
// resulting handle. RegDisablePredefinedCache() is the documented way to flush
// HKCU so do not use it with this function.
bool FlushRegKey(HKEY root) {
  HKEY key;
  if (ERROR_SUCCESS == ::RegOpenKeyExW(root, NULL, 0, MAXIMUM_ALLOWED, &key)) {
    if (ERROR_SUCCESS != ::RegCloseKey(key))
      return false;
  }
  return true;
}

// This function forces advapi32.dll to release some internally cached handles
// that were made during calls to RegOpenkey and RegOpenKeyEx if it is called
// with a more restrictive token. Returns true if the flushing is succesful
// although this behavior is undocumented and there is no guarantee that in
// fact this will happen in future versions of windows.
bool FlushCachedRegHandles() {
  return (FlushRegKey(HKEY_LOCAL_MACHINE) &&
          FlushRegKey(HKEY_CLASSES_ROOT) &&
          FlushRegKey(HKEY_USERS));
}

// Checks if we have handle entries pending and runs the closer.
bool CloseOpenHandles() {
  if (sandbox::HandleCloserAgent::NeedsHandlesClosed()) {
    sandbox::HandleCloserAgent handle_closer;

    handle_closer.InitializeHandlesToClose();
    if (!handle_closer.CloseHandles())
      return false;
  }

  return true;
}

}  // namespace

namespace sandbox {

SANDBOX_INTERCEPT IntegrityLevel g_shared_delayed_integrity_level =
    INTEGRITY_LEVEL_LAST;
SANDBOX_INTERCEPT MitigationFlags g_shared_delayed_mitigations = 0;

TargetServicesBase::TargetServicesBase() {
}

ResultCode TargetServicesBase::Init() {
  process_state_.SetInitCalled();
  return SBOX_ALL_OK;
}

// Failure here is a breach of security so the process is terminated.
void TargetServicesBase::LowerToken() {
  if (ERROR_SUCCESS !=
      SetProcessIntegrityLevel(g_shared_delayed_integrity_level))
    ::TerminateProcess(::GetCurrentProcess(), SBOX_FATAL_INTEGRITY);
  process_state_.SetRevertedToSelf();
  // If the client code as called RegOpenKey, advapi32.dll has cached some
  // handles. The following code gets rid of them.
  if (!::RevertToSelf())
    ::TerminateProcess(::GetCurrentProcess(), SBOX_FATAL_DROPTOKEN);
  if (!FlushCachedRegHandles())
    ::TerminateProcess(::GetCurrentProcess(), SBOX_FATAL_FLUSHANDLES);
  if (ERROR_SUCCESS != ::RegDisablePredefinedCache())
    ::TerminateProcess(::GetCurrentProcess(), SBOX_FATAL_CACHEDISABLE);
  if (!CloseOpenHandles())
    ::TerminateProcess(::GetCurrentProcess(), SBOX_FATAL_CLOSEHANDLES);
  // Enabling mitigations must happen last otherwise handle closing breaks
  if (g_shared_delayed_mitigations &&
      !ApplyProcessMitigationsToCurrentProcess(g_shared_delayed_mitigations))
    ::TerminateProcess(::GetCurrentProcess(), SBOX_FATAL_MITIGATION);
}

ProcessState* TargetServicesBase::GetState() {
  return &process_state_;
}

TargetServicesBase* TargetServicesBase::GetInstance() {
  static TargetServicesBase instance;
  return &instance;
}

// The broker services a 'test' IPC service with the IPC_PING_TAG tag.
bool TargetServicesBase::TestIPCPing(int version) {
  void* memory = GetGlobalIPCMemory();
  if (NULL == memory) {
    return false;
  }
  SharedMemIPCClient ipc(memory);
  CrossCallReturn answer = {0};

  if (1 == version) {
    uint32 tick1 = ::GetTickCount();
    uint32 cookie = 717115;
    ResultCode code = CrossCall(ipc, IPC_PING1_TAG, cookie, &answer);

    if (SBOX_ALL_OK != code) {
      return false;
    }
    // We should get two extended returns values from the IPC, one is the
    // tick count on the broker and the other is the cookie times two.
    if ((answer.extended_count != 2)) {
      return false;
    }
    // We test the first extended answer to be within the bounds of the tick
    // count only if there was no tick count wraparound.
    uint32 tick2 = ::GetTickCount();
    if (tick2 >= tick1) {
      if ((answer.extended[0].unsigned_int < tick1) ||
          (answer.extended[0].unsigned_int > tick2)) {
        return false;
      }
    }

    if (answer.extended[1].unsigned_int != cookie * 2) {
      return false;
    }
  } else if (2 == version) {
    uint32 cookie = 717111;
    InOutCountedBuffer counted_buffer(&cookie, sizeof(cookie));
    ResultCode code = CrossCall(ipc, IPC_PING2_TAG, counted_buffer, &answer);

    if (SBOX_ALL_OK != code) {
      return false;
    }
    if (cookie != 717111 * 3) {
      return false;
    }
  } else {
    return false;
  }
  return true;
}

bool ProcessState::IsKernel32Loaded() {
  return process_state_ != 0;
}

bool ProcessState::InitCalled() {
  return process_state_ > 1;
}

bool ProcessState::RevertedToSelf() {
  return process_state_ > 2;
}

void ProcessState::SetKernel32Loaded() {
  if (!process_state_)
    process_state_ = 1;
}

void ProcessState::SetInitCalled() {
  if (process_state_ < 2)
    process_state_ = 2;
}

void ProcessState::SetRevertedToSelf() {
  if (process_state_ < 3)
    process_state_ = 3;
}

ResultCode TargetServicesBase::DuplicateHandle(HANDLE source_handle,
                                               DWORD target_process_id,
                                               HANDLE* target_handle,
                                               DWORD desired_access,
                                               DWORD options) {
  return sandbox::DuplicateHandleProxy(source_handle, target_process_id,
                                       target_handle, desired_access, options);
}

}  // namespace sandbox