remoting/host/sas_injector_win.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 "remoting/host/sas_injector.h"
   6
   7 #include <windows.h>
   8 #include <string>
   9
  10 #include "base/files/file_path.h"
  11 #include "base/logging.h"
  12 #include "base/path_service.h"
  13 #include "base/scoped_native_library.h"
  14 #include "base/strings/utf_string_conversions.h"
  15 #include "base/win/registry.h"
  16 #include "base/win/windows_version.h"
  17 #include "third_party/webrtc/modules/desktop_capture/win/desktop.h"
  18 #include "third_party/webrtc/modules/desktop_capture/win/scoped_thread_desktop.h"
  19
  20 namespace remoting {
  21
  22 namespace {
  23
  24 // Names of the API and library implementing software SAS generation.
  25 const base::FilePath::CharType kSasDllFileName[] = FILE_PATH_LITERAL("sas.dll");
  26 const char kSendSasName[] = "SendSAS";
  27
  28 // The prototype of SendSAS().
  29 typedef VOID (WINAPI *SendSasFunc)(BOOL);
  30
  31 // The registry key and value holding the policy controlling software SAS
  32 // generation.
  33 const wchar_t kSystemPolicyKeyName[] =
  34     L"Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\System";
  35 const wchar_t kSoftwareSasValueName[] = L"SoftwareSASGeneration";
  36
  37 const DWORD kEnableSoftwareSasByServices = 1;
  38
  39 // Toggles the default software SAS generation policy to enable SAS generation
  40 // by services. Non-default policy is not changed.
  41 class ScopedSoftwareSasPolicy {
  42  public:
  43   ScopedSoftwareSasPolicy();
  44   ~ScopedSoftwareSasPolicy();
  45
  46   bool Apply();
  47
  48  private:
  49   // The handle of the registry key were SoftwareSASGeneration policy is stored.
  50   base::win::RegKey system_policy_;
  51
  52   // True if the policy needs to be restored.
  53   bool restore_policy_;
  54
  55   DISALLOW_COPY_AND_ASSIGN(ScopedSoftwareSasPolicy);
  56 };
  57
  58 ScopedSoftwareSasPolicy::ScopedSoftwareSasPolicy()
  59     : restore_policy_(false) {
  60 }
  61
  62 ScopedSoftwareSasPolicy::~ScopedSoftwareSasPolicy() {
  63   // Restore the default policy by deleting the value that we have set.
  64   if (restore_policy_) {
  65     LONG result = system_policy_.DeleteValue(kSoftwareSasValueName);
  66     if (result != ERROR_SUCCESS) {
  67       SetLastError(result);
  68       LOG_GETLASTERROR(ERROR)
  69           << "Failed to restore the software SAS generation policy";
  70     }
  71   }
  72 }
  73
  74 bool ScopedSoftwareSasPolicy::Apply() {
  75   // Query the currently set SoftwareSASGeneration policy.
  76   LONG result = system_policy_.Open(HKEY_LOCAL_MACHINE,
  77                                     kSystemPolicyKeyName,
  78                                     KEY_QUERY_VALUE | KEY_SET_VALUE |
  79                                         KEY_WOW64_64KEY);
  80   if (result != ERROR_SUCCESS) {
  81     SetLastError(result);
  82     LOG_GETLASTERROR(ERROR) << "Failed to open 'HKLM\\"
  83                             << kSystemPolicyKeyName << "'";
  84     return false;
  85   }
  86
  87   bool custom_policy = system_policy_.HasValue(kSoftwareSasValueName);
  88
  89   // Override the default policy (i.e. there is no value in the registry) only.
  90   if (!custom_policy) {
  91     result = system_policy_.WriteValue(kSoftwareSasValueName,
  92                                        kEnableSoftwareSasByServices);
  93     if (result != ERROR_SUCCESS) {
  94       SetLastError(result);
  95       LOG_GETLASTERROR(ERROR)
  96           << "Failed to enable software SAS generation by services";
  97       return false;
  98     } else {
  99       restore_policy_ = true;
 100     }
 101   }
 102
 103   return true;
 104 }
 105
 106 } // namespace
 107
 108 // Sends Secure Attention Sequence using the SendSAS() function from sas.dll.
 109 // This library is shipped starting from Win7/W2K8 R2 only. However Win7 SDK
 110 // includes a redistributable verion of the same library that works on
 111 // Vista/W2K8. We install the latter along with our binaries.
 112 class SasInjectorWin : public SasInjector {
 113  public:
 114   SasInjectorWin();
 115   virtual ~SasInjectorWin();
 116
 117   // SasInjector implementation.
 118   virtual bool InjectSas() OVERRIDE;
 119
 120  private:
 121   base::ScopedNativeLibrary sas_dll_;
 122   SendSasFunc send_sas_;
 123 };
 124
 125 // Emulates Secure Attention Sequence (Ctrl+Alt+Del) by switching to
 126 // the Winlogon desktop and injecting Ctrl+Alt+Del as a hot key.
 127 // N.B. Windows XP/W2K3 only.
 128 class SasInjectorXp : public SasInjector {
 129  public:
 130   SasInjectorXp();
 131   virtual ~SasInjectorXp();
 132
 133   // SasInjector implementation.
 134   virtual bool InjectSas() OVERRIDE;
 135 };
 136
 137 SasInjectorWin::SasInjectorWin() : send_sas_(NULL) {
 138 }
 139
 140 SasInjectorWin::~SasInjectorWin() {
 141 }
 142
 143 bool SasInjectorWin::InjectSas() {
 144   // Load sas.dll. The library is expected to be in the same folder as this
 145   // binary.
 146   if (!sas_dll_.is_valid()) {
 147     base::FilePath dir_path;
 148     if (!PathService::Get(base::DIR_EXE, &dir_path)) {
 149       LOG(ERROR) << "Failed to get the executable file name.";
 150       return false;
 151     }
 152
 153     sas_dll_.Reset(base::LoadNativeLibrary(dir_path.Append(kSasDllFileName),
 154                                            NULL));
 155   }
 156   if (!sas_dll_.is_valid()) {
 157     LOG(ERROR) << "Failed to load '" << kSasDllFileName << "'";
 158     return false;
 159   }
 160
 161   // Get the pointer to sas!SendSAS().
 162   if (send_sas_ == NULL) {
 163     send_sas_ = static_cast<SendSasFunc>(
 164         sas_dll_.GetFunctionPointer(kSendSasName));
 165   }
 166   if (send_sas_ == NULL) {
 167     LOG(ERROR) << "Failed to retrieve the address of '" << kSendSasName
 168                << "()'";
 169     return false;
 170   }
 171
 172   // Enable software SAS generation by services and send SAS. SAS can still fail
 173   // if the policy does not allow services to generate software SAS.
 174   ScopedSoftwareSasPolicy enable_sas;
 175   if (!enable_sas.Apply())
 176     return false;
 177
 178   (*send_sas_)(FALSE);
 179   return true;
 180 }
 181
 182 SasInjectorXp::SasInjectorXp() {
 183 }
 184
 185 SasInjectorXp::~SasInjectorXp() {
 186 }
 187
 188 bool SasInjectorXp::InjectSas() {
 189   const wchar_t kWinlogonDesktopName[] = L"Winlogon";
 190   const wchar_t kSasWindowClassName[] = L"SAS window class";
 191   const wchar_t kSasWindowTitle[] = L"SAS window";
 192
 193   scoped_ptr<webrtc::Desktop> winlogon_desktop(
 194       webrtc::Desktop::GetDesktop(kWinlogonDesktopName));
 195   if (!winlogon_desktop.get()) {
 196     LOG_GETLASTERROR(ERROR)
 197         << "Failed to open '" << kWinlogonDesktopName << "' desktop";
 198     return false;
 199   }
 200
 201   webrtc::ScopedThreadDesktop desktop;
 202   if (!desktop.SetThreadDesktop(winlogon_desktop.release())) {
 203     LOG_GETLASTERROR(ERROR)
 204         << "Failed to switch to '" << kWinlogonDesktopName << "' desktop";
 205     return false;
 206   }
 207
 208   HWND window = FindWindow(kSasWindowClassName, kSasWindowTitle);
 209   if (!window) {
 210     LOG_GETLASTERROR(ERROR)
 211         << "Failed to find '" << kSasWindowTitle << "' window";
 212     return false;
 213   }
 214
 215   if (PostMessage(window,
 216                   WM_HOTKEY,
 217                   0,
 218                   MAKELONG(MOD_ALT | MOD_CONTROL, VK_DELETE)) == 0) {
 219     LOG_GETLASTERROR(ERROR)
 220         << "Failed to post WM_HOTKEY message";
 221     return false;
 222   }
 223
 224   return true;
 225 }
 226
 227 scoped_ptr<SasInjector> SasInjector::Create() {
 228   if (base::win::GetVersion() < base::win::VERSION_VISTA) {
 229     return scoped_ptr<SasInjector>(new SasInjectorXp());
 230   } else {
 231     return scoped_ptr<SasInjector>(new SasInjectorWin());
 232   }
 233 }
 234
 235 } // namespace remoting