[Chromoting] Call SendSAS() directly from the host.

remoting/host/sas_injector_win.cc

 // 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 "remoting/host/sas_injector.h"
 
 #include <windows.h>
 #include <string>
 
 #include "base/logging.h"
 #include "base/file_path.h"
 #include "base/path_service.h"
 #include "base/scoped_native_library.h"
 #include "base/utf_string_conversions.h"
 #include "base/win/registry.h"
 #include "base/win/windows_version.h"
+#include "remoting/host/win/desktop.h"
+#include "remoting/host/win/scoped_thread_desktop.h"
 
 namespace remoting {
 
 namespace {
 
 // Names of the API and library implementing software SAS generation.
-const FilePath::CharType kSasDllFileName[] =
-    FILE_PATH_LITERAL("sas.dll");
+const FilePath::CharType kSasDllFileName[] = FILE_PATH_LITERAL("sas.dll");
 const char kSendSasName[] = "SendSAS";
 
 // The prototype of SendSAS().
 typedef VOID (WINAPI *SendSasFunc)(BOOL);
 
 // The registry key and value holding the policy controlling software SAS
 // generation.
 const wchar_t kSystemPolicyKeyName[] =
     L"Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\System";
 const wchar_t kSoftwareSasValueName[] = L"SoftwareSASGeneration";
 
-const DWORD kEnableSoftwareSasByServices = 1;
+const DWORD kEnableSoftwareSasByApps = 2;
 
 // Toggles the default software SAS generation policy to enable SAS generation
-// by services. Non-default policy is not changed.
+// by applications. Non-default policy is not changed.
 class ScopedSoftwareSasPolicy {
  public:
   ScopedSoftwareSasPolicy();
   ~ScopedSoftwareSasPolicy();
 
   bool Apply();
 
  private:
   // The handle of the registry key were SoftwareSASGeneration policy is stored.
   base::win::RegKey system_policy_;
@@ skipping 31 matching lines @@
     LOG_GETLASTERROR(ERROR) << "Failed to open 'HKLM\\"
                             << kSystemPolicyKeyName << "'";
     return false;
   }
 
   bool custom_policy = system_policy_.HasValue(kSoftwareSasValueName);
 
   // Override the default policy (i.e. there is no value in the registry) only.
   if (!custom_policy) {
     result = system_policy_.WriteValue(kSoftwareSasValueName,
-                                       kEnableSoftwareSasByServices);
+                                       kEnableSoftwareSasByApps);
     if (result != ERROR_SUCCESS) {
       SetLastError(result);
       LOG_GETLASTERROR(ERROR)
           << "Failed to enable software SAS generation by services";
       return false;
     } else {
       restore_policy_ = true;
     }
   }
 
@@ skipping 12 matching lines @@
   virtual ~SasInjectorWin();
 
   // SasInjector implementation.
   virtual bool InjectSas() OVERRIDE;
 
  private:
   base::ScopedNativeLibrary sas_dll_;
   SendSasFunc send_sas_;
 };
 
+// Emulates Secure Attention Sequence (Ctrl+Alt+Del) by switching to
+// the Winlogon desktop and injecting Ctrl+Alt+Del as a hot key.
+// N.B. Windows XP/W2K3 only.
+class SasInjectorXp : public SasInjector {
+ public:
+  SasInjectorXp();
+  virtual ~SasInjectorXp();
+
+  // SasInjector implementation.
+  virtual bool InjectSas() OVERRIDE;
+};
+
 SasInjectorWin::SasInjectorWin() : send_sas_(NULL) {
 }
 
 SasInjectorWin::~SasInjectorWin() {
 }
 
 bool SasInjectorWin::InjectSas() {
   // Load sas.dll. The library is expected to be in the same folder as this
   // binary.
   if (!sas_dll_.is_valid()) {
@@ skipping 16 matching lines @@
     send_sas_ = static_cast<SendSasFunc>(
         sas_dll_.GetFunctionPointer(kSendSasName));
   }
   if (send_sas_ == NULL) {
     LOG(ERROR) << "Failed to retrieve the address of '" << kSendSasName
                << "()'";
     return false;
   }
 
   // Enable software SAS generation by services and send SAS. SAS can still fail
   // if the policy does not allow services to generate software SAS.

[simonmorris, 2012/08/14 17:29:59]

Does the reference to "services" need updating?

   ScopedSoftwareSasPolicy enable_sas;
   if (!enable_sas.Apply())
     return false;
 
-  (*send_sas_)(FALSE);
+  (*send_sas_)(TRUE);
+  return true;
+}
+
+SasInjectorXp::SasInjectorXp() {
+}
+
+SasInjectorXp::~SasInjectorXp() {
+}
+
+bool SasInjectorXp::InjectSas() {
+  const wchar_t kWinlogonDesktopName[] = L"Winlogon";
+  const wchar_t kSasWindowClassName[] = L"SAS window class";
+  const wchar_t kSasWindowTitle[] = L"SAS window";
+
+  scoped_ptr<remoting::Desktop> winlogon_desktop(
+      remoting::Desktop::GetDesktop(kWinlogonDesktopName));
+  if (!winlogon_desktop.get())
+    return false;
+
+  remoting::ScopedThreadDesktop desktop;
+  if (!desktop.SetThreadDesktop(winlogon_desktop.Pass()))
+    return false;
+
+  HWND window = FindWindow(kSasWindowClassName, kSasWindowTitle);
+  if (!window)
+    return false;
+
+  PostMessage(window,
+              WM_HOTKEY,
+              0,
+              MAKELONG(MOD_ALT | MOD_CONTROL, VK_DELETE));
   return true;
 }
 
 scoped_ptr<SasInjector> SasInjector::Create() {
-  if (base::win::GetVersion() >= base::win::VERSION_VISTA) {
+  if (base::win::GetVersion() < base::win::VERSION_VISTA) {
+    return scoped_ptr<SasInjector>(new SasInjectorXp());
+  } else {
     return scoped_ptr<SasInjector>(new SasInjectorWin());
   }
-
-  return scoped_ptr<SasInjector>();
 }
 
 } // namespace remoting