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       PLOG(ERROR) << "Failed to restore the software SAS generation policy";
  69     }
  70   }
  71 }
  72
  73 bool ScopedSoftwareSasPolicy::Apply() {
  74   // Query the currently set SoftwareSASGeneration policy.
  75   LONG result = system_policy_.Open(HKEY_LOCAL_MACHINE,
  76                                     kSystemPolicyKeyName,
  77                                     KEY_QUERY_VALUE | KEY_SET_VALUE |
  78                                         KEY_WOW64_64KEY);
  79   if (result != ERROR_SUCCESS) {
  80     SetLastError(result);
  81     PLOG(ERROR) << "Failed to open 'HKLM\\" << kSystemPolicyKeyName << "'";
  82     return false;
  83   }
  84
  85   bool custom_policy = system_policy_.HasValue(kSoftwareSasValueName);
  86
  87   // Override the default policy (i.e. there is no value in the registry) only.
  88   if (!custom_policy) {
  89     result = system_policy_.WriteValue(kSoftwareSasValueName,
  90                                        kEnableSoftwareSasByServices);
  91     if (result != ERROR_SUCCESS) {
  92       SetLastError(result);
  93       PLOG(ERROR) << "Failed to enable software SAS generation by services";
  94       return false;
  95     } else {
  96       restore_policy_ = true;
  97     }
  98   }
  99
 100   return true;
 101 }
 102
 103 } // namespace
 104
 105 // Sends Secure Attention Sequence using the SendSAS() function from sas.dll.
 106 // This library is shipped starting from Win7/W2K8 R2 only. However Win7 SDK
 107 // includes a redistributable verion of the same library that works on
 108 // Vista/W2K8. We install the latter along with our binaries.
 109 class SasInjectorWin : public SasInjector {
 110  public:
 111   SasInjectorWin();
 112   virtual ~SasInjectorWin();
 113
 114   // SasInjector implementation.
 115   virtual bool InjectSas() override;
 116
 117  private:
 118   base::ScopedNativeLibrary sas_dll_;
 119   SendSasFunc send_sas_;
 120 };
 121
 122 // Emulates Secure Attention Sequence (Ctrl+Alt+Del) by switching to
 123 // the Winlogon desktop and injecting Ctrl+Alt+Del as a hot key.
 124 // N.B. Windows XP/W2K3 only.
 125 class SasInjectorXp : public SasInjector {
 126  public:
 127   SasInjectorXp();
 128   virtual ~SasInjectorXp();
 129
 130   // SasInjector implementation.
 131   virtual bool InjectSas() override;
 132 };
 133
 134 SasInjectorWin::SasInjectorWin() : send_sas_(nullptr) {
 135 }
 136
 137 SasInjectorWin::~SasInjectorWin() {
 138 }
 139
 140 bool SasInjectorWin::InjectSas() {
 141   // Load sas.dll. The library is expected to be in the same folder as this
 142   // binary.
 143   if (!sas_dll_.is_valid()) {
 144     base::FilePath dir_path;
 145     if (!PathService::Get(base::DIR_EXE, &dir_path)) {
 146       LOG(ERROR) << "Failed to get the executable file name.";
 147       return false;
 148     }
 149
 150     sas_dll_.Reset(base::LoadNativeLibrary(dir_path.Append(kSasDllFileName),
 151                                            nullptr));
 152   }
 153   if (!sas_dll_.is_valid()) {
 154     LOG(ERROR) << "Failed to load '" << kSasDllFileName << "'";
 155     return false;
 156   }
 157
 158   // Get the pointer to sas!SendSAS().
 159   if (send_sas_ == nullptr) {
 160     send_sas_ = reinterpret_cast<SendSasFunc>(
 161         sas_dll_.GetFunctionPointer(kSendSasName));
 162   }
 163   if (send_sas_ == nullptr) {
 164     LOG(ERROR) << "Failed to retrieve the address of '" << kSendSasName
 165                << "()'";
 166     return false;
 167   }
 168
 169   // Enable software SAS generation by services and send SAS. SAS can still fail
 170   // if the policy does not allow services to generate software SAS.
 171   ScopedSoftwareSasPolicy enable_sas;
 172   if (!enable_sas.Apply())
 173     return false;
 174
 175   (*send_sas_)(FALSE);
 176   return true;
 177 }
 178
 179 SasInjectorXp::SasInjectorXp() {
 180 }
 181
 182 SasInjectorXp::~SasInjectorXp() {
 183 }
 184
 185 bool SasInjectorXp::InjectSas() {
 186   const wchar_t kWinlogonDesktopName[] = L"Winlogon";
 187   const wchar_t kSasWindowClassName[] = L"SAS window class";
 188   const wchar_t kSasWindowTitle[] = L"SAS window";
 189
 190   scoped_ptr<webrtc::Desktop> winlogon_desktop(
 191       webrtc::Desktop::GetDesktop(kWinlogonDesktopName));
 192   if (!winlogon_desktop.get()) {
 193     PLOG(ERROR) << "Failed to open '" << kWinlogonDesktopName << "' desktop";
 194     return false;
 195   }
 196
 197   webrtc::ScopedThreadDesktop desktop;
 198   if (!desktop.SetThreadDesktop(winlogon_desktop.release())) {
 199     PLOG(ERROR) << "Failed to switch to '" << kWinlogonDesktopName
 200                 << "' desktop";
 201     return false;
 202   }
 203
 204   HWND window = FindWindow(kSasWindowClassName, kSasWindowTitle);
 205   if (!window) {
 206     PLOG(ERROR) << "Failed to find '" << kSasWindowTitle << "' window";
 207     return false;
 208   }
 209
 210   if (PostMessage(window,
 211                   WM_HOTKEY,
 212                   0,
 213                   MAKELONG(MOD_ALT | MOD_CONTROL, VK_DELETE)) == 0) {
 214     PLOG(ERROR) << "Failed to post WM_HOTKEY message";
 215     return false;
 216   }
 217
 218   return true;
 219 }
 220
 221 scoped_ptr<SasInjector> SasInjector::Create() {
 222   if (base::win::GetVersion() < base::win::VERSION_VISTA) {
 223     return make_scoped_ptr(new SasInjectorXp());
 224   } else {
 225     return make_scoped_ptr(new SasInjectorWin());
 226   }
 227 }
 228
 229 } // namespace remoting