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

remoting/host/sas_injector_win.cc

Index: remoting/host/sas_injector_win.cc
diff --git a/remoting/host/sas_injector_win.cc b/remoting/host/sas_injector_win.cc
index 0bf453f6a69c63f6d8f7e0e7d00eceb55346561a..3e5bea80aea92cbe8ec4de0d81605ae8d416e827 100644
--- a/remoting/host/sas_injector_win.cc
+++ b/remoting/host/sas_injector_win.cc
@@ -14,14 +14,15 @@
 #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().
@@ -33,10 +34,10 @@ 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();
@@ -88,7 +89,7 @@ bool ScopedSoftwareSasPolicy::Apply() {
   // 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)
@@ -121,6 +122,18 @@ class SasInjectorWin : public SasInjector {
   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) {
 }
 
@@ -157,7 +170,7 @@ bool SasInjectorWin::InjectSas() {
   }
 
   // Enable software SAS generation by services and send SAS. SAS can still fail
-  // if the policy does not allow services to generate software SAS.
+  // if the policy does not allow applications to generate software SAS.
   ScopedSoftwareSasPolicy enable_sas;
   if (!enable_sas.Apply())
     return false;
@@ -166,12 +179,43 @@ bool SasInjectorWin::InjectSas() {
   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