Add support for alternate window station.

sandbox/src/window.cc

+// Copyright (c) 2009 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 "sandbox/src/window.h"
+
+#include <aclapi.h>
+
+#include "base/logging.h"
+#include "base/scoped_ptr.h"
+
+namespace {
+
+// Gets the security attributes of a window object referenced by |handle|. The
+// lpSecurityDescriptor member of the SECURITY_ATTRIBUTES parameter returned
+// must be freed using LocalFree by the caller.
+bool GetSecurityAttributes(HANDLE handle, SECURITY_ATTRIBUTES* attributes) {
+  attributes->bInheritHandle = FALSE;
+  attributes->nLength = sizeof(SECURITY_ATTRIBUTES);
+
+  PACL dacl = NULL;
+  DWORD result = ::GetSecurityInfo(handle, SE_WINDOW_OBJECT,
+                                   DACL_SECURITY_INFORMATION, NULL, NULL, &dacl,
+                                   NULL, &attributes->lpSecurityDescriptor);
+  if (ERROR_SUCCESS == result)
+    return true;
+
+  return false;
+}
+
+}
+
+namespace sandbox {
+
+ResultCode CreateAltWindowStation(HWINSTA* winsta) {
+  // Get the security attributes from the current window station; we will
+  // use this as the base security attributes for the new window station.
+  SECURITY_ATTRIBUTES attributes = {0};
+  if (!GetSecurityAttributes(::GetProcessWindowStation(), &attributes)) {
+    return SBOX_ERROR_CANNOT_CREATE_WINSTATION;
+  }
+
+  // Create the window station using NULL for the name to ask the os to
+  // generate it.
+  // TODO(nsylvain): don't ask for WINSTA_ALL_ACCESS if we don't need to.
+  *winsta = ::CreateWindowStationW(NULL, 0, WINSTA_ALL_ACCESS, &attributes);
+  LocalFree(attributes.lpSecurityDescriptor);
+
+  if (*winsta)
+    return SBOX_ALL_OK;
+
+  return SBOX_ERROR_CANNOT_CREATE_WINSTATION;
+}
+
+ResultCode CreateAltDesktop(HWINSTA winsta, HDESK* desktop) {
+  std::wstring desktop_name = L"sbox_alternate_desktop_";
+
+  // Append the current PID to the desktop name.
+  wchar_t buffer[16];
+  _snwprintf_s(buffer, sizeof(buffer) / sizeof(wchar_t), L"0x%X",
+               ::GetCurrentProcessId());
+  desktop_name += buffer;
+
+  // Get the security attributes from the current desktop, we will use this as
+  // the base security attributes for the new desktop.
+  SECURITY_ATTRIBUTES attributes = {0};
+  if (!GetSecurityAttributes(GetThreadDesktop(GetCurrentThreadId()),
+                             &attributes)) {
+    return SBOX_ERROR_CANNOT_CREATE_DESKTOP;
+  }
+
+  // Back up the current window station, in case we need to switch it.
+  HWINSTA current_winsta = ::GetProcessWindowStation();
+
+  if (winsta) {
+    // We need to switch to the alternate window station before creating the
+    // desktop.
+    if (!::SetProcessWindowStation(winsta)) {
+      ::LocalFree(attributes.lpSecurityDescriptor);
+      return SBOX_ERROR_CANNOT_CREATE_DESKTOP;
+    }
+  }
+
+  // Create the destkop.
+  // TODO(nsylvain): don't ask for GENERIC_ALL if we don't need to.
+  *desktop = ::CreateDesktop(desktop_name.c_str(), NULL, NULL, 0, GENERIC_ALL,
+                             &attributes);
+  ::LocalFree(attributes.lpSecurityDescriptor);
+
+  if (winsta) {
+    // Revert to the right window station.
+    if (!::SetProcessWindowStation(current_winsta)) {
+      return SBOX_ERROR_FAILED_TO_SWITCH_BACK_WINSTATION;
+    }
+  }
+
+  if (*desktop)
+    return SBOX_ALL_OK;
+
+  return SBOX_ERROR_CANNOT_CREATE_DESKTOP;
+}
+
+std::wstring GetWindowObjectName(HANDLE handle) {
+  // Get the size of the name.
+  DWORD size = 0;
+  ::GetUserObjectInformation(handle, UOI_NAME, NULL, 0, &size);
+
+  if (!size) {
+    NOTREACHED();
+    return std::wstring();
+  }
+
+  // Create the buffer that will hold the name.
+  scoped_ptr<wchar_t> name_buffer(new wchar_t[size]);
+
+  // Query the name of the object.
+  if (!::GetUserObjectInformation(handle, UOI_NAME, name_buffer.get(), size,
+                                  &size)) {
+    NOTREACHED();
+    return std::wstring();
+  }
+
+  return std::wstring(name_buffer.get());
+}
+
+std::wstring GetFullDesktopName(HWINSTA winsta, HDESK desktop) {
+  if (!desktop) {
+    NOTREACHED();
+    return std::wstring();
+  }
+
+  std::wstring name;
+  if (winsta) {
+    name = GetWindowObjectName(winsta);
+    name += L'\\';
+  }
+
+  name += GetWindowObjectName(desktop);
+  return name;
+}
+
+}  // namespace sandbox