Fixing curtain mode using non-default RDP port for Windows host.

remoting/host/desktop_session_win.cc

Index: remoting/host/desktop_session_win.cc
diff --git a/remoting/host/desktop_session_win.cc b/remoting/host/desktop_session_win.cc
index 413b17985ecdab2fc8093ed793e8a40bf74814ff..f1d758667165c542d9d3c119955653c7b3a92f88 100644
--- a/remoting/host/desktop_session_win.cc
+++ b/remoting/host/desktop_session_win.cc
@@ -22,6 +22,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
+#include "base/win/registry.h"
 #include "base/win/scoped_bstr.h"
 #include "base/win/scoped_comptr.h"
 #include "base/win/scoped_handle.h"
@@ -82,10 +83,18 @@ const int kDefaultRdpDpi = 96;
 // The session attach notification should arrive within 30 seconds.
 const int kSessionAttachTimeoutSeconds = 30;
 
+// The default port number used for establishing an RDP session.
+const int kDefaultRdpPort = 3389;
+
+// The values used to establish RDP connections are stored in the registry.
+const wchar_t kRdpTcpSettingsKeyName[] = L"SYSTEM\\CurrentControlSet\\"
+    L"Control\\Terminal Server\\WinStations\\RDP-Tcp";
+const wchar_t kRdpPortValueName[] = L"PortNumber";
+
 // DesktopSession implementation which attaches to the host's physical console.
 // Receives IPC messages from the desktop process, running in the console
 // session, via |WorkerProcessIpcDelegate|, and monitors console session
-// attach/detach events via |WtsConsoleObserer|.
+// attach/detach events via |WtsConsoleObserver|.
 class ConsoleSession : public DesktopSessionWin {
  public:
   // Same as DesktopSessionWin().
@@ -113,7 +122,7 @@ class ConsoleSession : public DesktopSessionWin {
 // DesktopSession implementation which attaches to virtual RDP console.
 // Receives IPC messages from the desktop process, running in the console
 // session, via |WorkerProcessIpcDelegate|, and monitors console session
-// attach/detach events via |WtsConsoleObserer|.
+// attach/detach events via |WtsConsoleObserver|.
 class RdpSession : public DesktopSessionWin {
  public:
   // Same as DesktopSessionWin().
@@ -168,6 +177,11 @@ class RdpSession : public DesktopSessionWin {
     DISALLOW_COPY_AND_ASSIGN(EventHandler);
   };
 
+  // Retrieves a DWORD value from the registry.  Returns true on success.
+  bool RetrieveDwordRegistryValue(const wchar_t* key_name,
+                                  const wchar_t* value_name,
+                                  DWORD* value);
+
   // Used to create an RDP desktop session.
   base::win::ScopedComPtr<IRdpDesktopSession> rdp_desktop_session_;
 
@@ -255,13 +269,22 @@ bool RdpSession::Initialize(const ScreenResolution& resolution) {
       std::min(kMaxRdpScreenHeight,
                std::max(kMinRdpScreenHeight, host_size.height())));
 
+  // Read the port number used by RDP.
+  DWORD server_port;
+  if (!RetrieveDwordRegistryValue(kRdpTcpSettingsKeyName, kRdpPortValueName,
+                                  &server_port) ||
+      server_port > 65535) {
+    server_port = kDefaultRdpPort;

[Jamie, 2016/05/03 00:18:12]

I realize you haven't changed the behaviour here, but this feels wrong. If the
user has attempted to configure something but set a bogus value, we should log
an error and fail (this would especially be true if we logged somewhere the user
could easily read it). Falling back on the default might give them false
confidence that they have done what they intended, leading to confusing
behaviour later on.

[joedow, 2016/05/03 19:07:08]

I think that makes sense.  It wouldn't have worked before but would have been
difficult to track the failure down.  This makes it deterministic which is good.

+  }
+
   // Create an RDP session.
   base::win::ScopedComPtr<IRdpDesktopSessionEventHandler> event_handler(
       new EventHandler(weak_factory_.GetWeakPtr()));
   terminal_id_ = base::GenerateGUID();
   base::win::ScopedBstr terminal_id(base::UTF8ToUTF16(terminal_id_).c_str());
   result = rdp_desktop_session_->Connect(host_size.width(), host_size.height(),
-                                         terminal_id, event_handler.get());
+                                         terminal_id, server_port,
+                                         event_handler.get());
   if (FAILED(result)) {
     LOG(ERROR) << "RdpSession::Create() failed, 0x"
                << std::hex << result << std::dec << ".";
@@ -298,6 +321,27 @@ void RdpSession::InjectSas() {
   rdp_desktop_session_->InjectSas();
 }
 
+bool RdpSession::RetrieveDwordRegistryValue(const wchar_t* key_name,
+                                            const wchar_t* value_name,
+                                            DWORD* value) {
+  DCHECK(key_name);
+  DCHECK(value_name);
+  DCHECK(value);
+
+  base::win::RegKey key(HKEY_LOCAL_MACHINE, key_name, KEY_READ);
+  if (!key.Valid()) {
+    LOG(WARNING) << "Failed to open key: " << key_name;
+    return false;
+  }
+
+  if (key.ReadValueDW(value_name, value) != ERROR_SUCCESS) {
+    LOG(WARNING) << "Failed to read registry value: " << value_name;
+    return false;
+  }
+
+  return true;
+}
+
 RdpSession::EventHandler::EventHandler(
     base::WeakPtr<RdpSession> desktop_session)
     : ref_count_(0),