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// Copyright (c) 2011 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/win/src/window.h"
#include <aclapi.h>
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "sandbox/win/src/acl.h"
#include "sandbox/win/src/sid.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.
*winsta = ::CreateWindowStationW(
NULL, 0, GENERIC_READ | WINSTA_CREATEDESKTOP, &attributes);
LocalFree(attributes.lpSecurityDescriptor);
if (*winsta)
return SBOX_ALL_OK;
return SBOX_ERROR_CANNOT_CREATE_WINSTATION;
}
ResultCode CreateAltDesktop(HWINSTA winsta, HDESK* desktop) {
base::string16 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.
*desktop = ::CreateDesktop(desktop_name.c_str(),
NULL,
NULL,
0,
DESKTOP_CREATEWINDOW | DESKTOP_READOBJECTS |
READ_CONTROL | WRITE_DAC | WRITE_OWNER,
&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) {
// Replace the DACL on the new Desktop with a reduced privilege version.
// We can soft fail on this for now, as it's just an extra mitigation.
static const ACCESS_MASK kDesktopDenyMask = WRITE_DAC | WRITE_OWNER |
DELETE |
DESKTOP_CREATEMENU |
DESKTOP_CREATEWINDOW |
DESKTOP_HOOKCONTROL |
DESKTOP_JOURNALPLAYBACK |
DESKTOP_JOURNALRECORD |
DESKTOP_SWITCHDESKTOP;
AddKnownSidToObject(*desktop, SE_WINDOW_OBJECT, Sid(WinRestrictedCodeSid),
DENY_ACCESS, kDesktopDenyMask);
return SBOX_ALL_OK;
}
return SBOX_ERROR_CANNOT_CREATE_DESKTOP;
}
base::string16 GetWindowObjectName(HANDLE handle) {
// Get the size of the name.
DWORD size = 0;
::GetUserObjectInformation(handle, UOI_NAME, NULL, 0, &size);
if (!size) {
NOTREACHED();
return base::string16();
}
// 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 base::string16();
}
return base::string16(name_buffer.get());
}
base::string16 GetFullDesktopName(HWINSTA winsta, HDESK desktop) {
if (!desktop) {
NOTREACHED();
return base::string16();
}
base::string16 name;
if (winsta) {
name = GetWindowObjectName(winsta);
name += L'\\';
}
name += GetWindowObjectName(desktop);
return name;
}
} // namespace sandbox
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