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[idd] helper: run interactive process as desktop user

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Explorer file copies were invisible to the Helper because the service
launched its child with a duplicate of the LocalSystem token and changed
only TokenSessionId. The child therefore remained a System-integrity
process. Windows filtered Explorer's file clipboard formats across that
integrity boundary. Basic text and bitmap formats continued to work.

Keep only the SCM service privileged. Obtain the active session user's
primary token with WTSQueryUserToken. For elevated accounts, prefer the
linked limited token. Validate its session and security properties.
Build the user environment and launch the interactive Helper on
WinSta0\Default. Gate Helper activation until the service has rechecked
the active session and registered the clipboard authority.

Use random lifetime, stop, and activation objects owned by the service.
Give the target logon SID synchronization access only. Recheck the
active console session and service state before activation. Make the
lifetime mutex terminate the Helper if the service exits unexpectedly.
Restart it when the active session, IDD host, or authority changes.

Replace the old process-handle mapping transfer with a device-bound
authority protocol on the LGIdd device interface. The service verifies
the exact driver host instance, duplicates only section map rights into
that process, and registers the session, mapping identifier, and handle.
Bind authority lifetime to its WDF file object, revoke it synchronously
on cleanup, and poll the driver host identity while the child is active.

Restrict the device stack to SYSTEM and isolate LGIdd in a unique UMDF
device group. Restrict the shared section to SYSTEM and the target logon
SID. Apply a medium mandatory label that prevents low-integrity readers
and writers. Map it with read/write rights instead of all access.

Give each clipboard mapping a second random authority identifier. Store
it only inside the logon-SID-protected mapping and send it in the
mandatory HELLO. LGIdd matches it against the service-injected mapping.
This authenticates the user Helper without the unsupported UMDF call to
GetNamedPipeClientSessionId. Have the Helper verify that its pipe server
is in session zero.

Extend the pipe endpoint with bounded authentication reads, cancellable
overlapped I/O, periodic authorization checks, and explicit disconnects.
Serialize authority changes with clipboard attach and detach. Prevent
stale cleanup from tearing down a replacement mapping. Disconnect the
user pipe immediately when its owning authority is revoked.

Run clipboard, OLE, display, configuration, and file access in the
user's interactive process. Retain its process token for worker-thread
file operations instead of querying and impersonating the desktop user
from a System process. Store Helper logs in LocalAppData and grant only
the registry rights needed by interactive configuration and UMDF.

Keep immediate, stage-specific Win32 and HRESULT diagnostics throughout
clipboard capture. Probe CF_HDROP while holding the Win32 clipboard and
enumerate the OLE object's advertised file formats. Validate returned
storage and fall back to Shell item paths when direct retrieval fails.
Validate clipboard sequence changes and defer retries during contention
without publishing incomplete clipboard state.

Complete the 1 MiB transfer work with full-sized Windows copy buffers.
Use full-sized FUSE reads and retain the named 64 KiB X11 chunk limit.
Validate the user-writable mapping with CClipboardRing before attaching.

The pipe, mapping, and authority protocols change together. LGIdd.dll,
the INF, and LGIddHelper.exe must be rebuilt and installed as one
matching set.
This commit is contained in:
Geoffrey McRae
2026-08-15 00:11:01 +10:00
parent e40dc19c7e
commit f9ffce528a
35 changed files with 2803 additions and 665 deletions
Download Patch File Download Diff File Expand all files Collapse all files

301
idd/LGIdd/Device.cpp
View File

@@ -27,11 +27,14 @@
#include <wdf.h>
#include <IddCx.h>
#include <avrt.h>
#include <bcrypt.h>
#include <wrl.h>
#include <limits>
#include <memory>
#include <utility>
#include "CDebug.h"
#include "ClipboardRing.h"
#include "display/CDisplayConfiguration.h"
#include "display/IddCxCompat.h"
#include "display/CDeviceContext.h"
@@ -42,7 +45,275 @@
WDFDEVICE l_wdfDevice = nullptr;
static const UINT IDDCX_VERSION_1_10 = 0x1A00;
static const UINT IDDCX_VERSION_1_10 = 0x1A00;
static uint64_t l_authorityInstanceId[2] = {};
static uint64_t l_authorityProcessCreated = 0;
static uint64_t FileTimeValue(const FILETIME& value)
{
ULARGE_INTEGER result = {};
result.LowPart = value.dwLowDateTime;
result.HighPart = value.dwHighDateTime;
return result.QuadPart;
}
static NTSTATUS InitAuthorityIdentity()
{
FILETIME created = {};
FILETIME exited = {};
FILETIME kernel = {};
FILETIME user = {};
if (!GetProcessTimes(GetCurrentProcess(),
&created, &exited, &kernel, &user))
{
const DWORD error = GetLastError();
DEBUG_ERROR_HR(error,
"Failed to query the LGIdd host process creation time");
return STATUS_UNSUCCESSFUL;
}
for (unsigned attempt = 0; attempt < 2; ++attempt)
{
const NTSTATUS status = BCryptGenRandom(nullptr,
reinterpret_cast<PUCHAR>(l_authorityInstanceId),
sizeof(l_authorityInstanceId), BCRYPT_USE_SYSTEM_PREFERRED_RNG);
if (!NT_SUCCESS(status))
{
DEBUG_ERROR_HR(HRESULT_FROM_NT(status),
"Failed to generate the LGIdd authority instance identifier");
return status;
}
if (l_authorityInstanceId[0] && l_authorityInstanceId[1])
{
l_authorityProcessCreated = FileTimeValue(created);
return STATUS_SUCCESS;
}
}
DEBUG_ERROR_HR(ERROR_INVALID_DATA,
"Generated an invalid LGIdd authority instance identifier");
return STATUS_DATA_ERROR;
}
static bool AuthorityInstanceMatches(const uint64_t (&instanceId)[2])
{
return instanceId[0] == l_authorityInstanceId[0] &&
instanceId[1] == l_authorityInstanceId[1];
}
static void LGIddAuthorityFileCleanup(WDFFILEOBJECT fileObject)
{
g_pipe.CloseClipboardAuthorityFile(fileObject);
}
static void LGIddAuthorityIoDeviceControl(WDFDEVICE device,
WDFREQUEST request, size_t outputLength, size_t inputLength,
ULONG controlCode)
{
UNREFERENCED_PARAMETER(device);
NTSTATUS status = STATUS_INVALID_DEVICE_REQUEST;
ULONG_PTR information = 0;
WDFFILEOBJECT fileObject = WdfRequestGetFileObject(request);
if (!fileObject)
{
DEBUG_WARN(
"LGIdd authority request has no file object");
WdfRequestComplete(request, STATUS_INVALID_HANDLE);
return;
}
switch (controlCode)
{
case IOCTL_LG_IDD_AUTHORITY_GET_HOST:
{
if (inputLength || outputLength < sizeof(LGIddAuthorityHost))
{
DEBUG_WARN(
"Rejected malformed LGIdd authority host request");
status = STATUS_BUFFER_TOO_SMALL;
break;
}
LGIddAuthorityHost * host = nullptr;
status = WdfRequestRetrieveOutputBuffer(request, sizeof(*host),
reinterpret_cast<void **>(&host), nullptr);
if (!NT_SUCCESS(status))
{
DEBUG_WARN_HR(HRESULT_FROM_NT(status),
"Failed to retrieve the LGIdd authority host output buffer");
break;
}
ZeroMemory(host, sizeof(*host));
host->size = sizeof(*host);
host->version = LG_IDD_AUTHORITY_VERSION;
host->processId = GetCurrentProcessId();
host->processCreated = l_authorityProcessCreated;
host->instanceId[0] = l_authorityInstanceId[0];
host->instanceId[1] = l_authorityInstanceId[1];
information = sizeof(*host);
status = STATUS_SUCCESS;
break;
}
case IOCTL_LG_IDD_AUTHORITY_REGISTER:
{
if (inputLength != sizeof(LGIddAuthorityRegistration) || outputLength)
{
DEBUG_WARN(
"Rejected malformed LGIdd authority registration request");
status = STATUS_INFO_LENGTH_MISMATCH;
break;
}
void * input = nullptr;
status = WdfRequestRetrieveInputBuffer(request,
sizeof(LGIddAuthorityRegistration), &input, nullptr);
if (!NT_SUCCESS(status))
{
DEBUG_WARN_HR(HRESULT_FROM_NT(status),
"Failed to retrieve the LGIdd authority registration buffer");
break;
}
const LGIddAuthorityRegistration * registration =
static_cast<const LGIddAuthorityRegistration *>(input);
if (registration->size != sizeof(*registration) ||
registration->version != LG_IDD_AUTHORITY_VERSION ||
registration->reserved ||
!AuthorityInstanceMatches(registration->instanceId) ||
!registration->mappingId[0] || !registration->mappingId[1] ||
!registration->mappingHandle ||
registration->mappingHandle >
static_cast<uint64_t>(
(std::numeric_limits<uintptr_t>::max)()) ||
registration->mappingHandle == static_cast<uint64_t>(
reinterpret_cast<uintptr_t>(INVALID_HANDLE_VALUE)))
{
DEBUG_WARN(
"Rejected invalid LGIdd authority registration data");
status = STATUS_DATA_ERROR;
break;
}
HANDLE rawMapping = reinterpret_cast<HANDLE>(
static_cast<uintptr_t>(registration->mappingHandle));
const auto closeInjectedMapping = [rawMapping]()
{
if (!CloseHandle(rawMapping))
{
const DWORD error = GetLastError();
DEBUG_WARN_HR(error,
"Failed to consume the injected clipboard authority handle");
return false;
}
return true;
};
const ClipboardMapping * view = static_cast<const ClipboardMapping *>(
MapViewOfFileFromApp(rawMapping,
FILE_MAP_READ | FILE_MAP_WRITE, 0, sizeof(ClipboardMapping)));
if (!view)
{
const DWORD error = GetLastError();
DEBUG_WARN_HR(error,
"Failed to validate the injected clipboard authority handle");
closeInjectedMapping();
status = STATUS_INVALID_HANDLE;
break;
}
const uint64_t authorityId[2] =
{ view->authorityId[0], view->authorityId[1] };
if (!UnmapViewOfFile(view))
{
const DWORD error = GetLastError();
DEBUG_WARN_HR(error,
"Failed to unmap the injected clipboard authority handle");
closeInjectedMapping();
status = STATUS_UNSUCCESSFUL;
break;
}
if (!authorityId[0] || !authorityId[1])
{
DEBUG_WARN("Rejected clipboard mapping without an authority ID");
closeInjectedMapping();
status = STATUS_DATA_ERROR;
break;
}
HANDLE mapping = nullptr;
if (!DuplicateHandle(GetCurrentProcess(), rawMapping,
GetCurrentProcess(), &mapping,
SECTION_MAP_READ | SECTION_MAP_WRITE, FALSE, 0))
{
const DWORD error = GetLastError();
DEBUG_WARN_HR(error,
"Failed to privatize the injected clipboard authority handle");
closeInjectedMapping();
status = STATUS_INVALID_HANDLE;
break;
}
if (!closeInjectedMapping())
{
CloseHandle(mapping);
status = STATUS_UNSUCCESSFUL;
break;
}
if (!g_pipe.RegisterClipboardAuthority(fileObject, mapping,
registration->session, registration->mappingId, authorityId))
{
CloseHandle(mapping);
status = STATUS_ACCESS_DENIED;
break;
}
status = STATUS_SUCCESS;
break;
}
case IOCTL_LG_IDD_AUTHORITY_CLEAR:
{
if (inputLength != sizeof(LGIddAuthorityClear) || outputLength)
{
DEBUG_WARN(
"Rejected malformed LGIdd authority clear request");
status = STATUS_INFO_LENGTH_MISMATCH;
break;
}
void * input = nullptr;
status = WdfRequestRetrieveInputBuffer(request,
sizeof(LGIddAuthorityClear), &input, nullptr);
if (!NT_SUCCESS(status))
{
DEBUG_WARN_HR(HRESULT_FROM_NT(status),
"Failed to retrieve the LGIdd authority clear buffer");
break;
}
const LGIddAuthorityClear * clear =
static_cast<const LGIddAuthorityClear *>(input);
if (clear->size != sizeof(*clear) ||
clear->version != LG_IDD_AUTHORITY_VERSION ||
!AuthorityInstanceMatches(clear->instanceId))
{
DEBUG_WARN(
"Rejected invalid LGIdd authority clear data");
status = STATUS_DATA_ERROR;
break;
}
if (!g_pipe.ClearClipboardAuthority(fileObject))
{
status = STATUS_ACCESS_DENIED;
break;
}
status = STATUS_SUCCESS;
break;
}
}
WdfRequestCompleteWithInformation(request, status, information);
}
static bool LGIddCanUseIddCx110DDIs(UINT iddCxVersion)
{
@@ -283,6 +554,13 @@ NTSTATUS LGIddMonitorUnassignSwapChain(IDDCX_MONITOR monitor)
NTSTATUS LGIddCreateDevice(_Inout_ PWDFDEVICE_INIT deviceInit)
{
NTSTATUS status;
if (!l_authorityInstanceId[0] || !l_authorityInstanceId[1])
{
status = InitAuthorityIdentity();
if (!NT_SUCCESS(status))
return status;
}
IDARG_OUT_GETVERSION ver;
status = IddCxGetVersion(&ver);
if (FAILED(status))
@@ -302,6 +580,7 @@ NTSTATUS LGIddCreateDevice(_Inout_ PWDFDEVICE_INIT deviceInit)
IDD_CX_CLIENT_CONFIG config;
IDD_CX_CLIENT_CONFIG_INIT(&config);
config.EvtIddCxAdapterInitFinished = LGIddAdapterInitFinished;
config.EvtIddCxDeviceIoControl = LGIddAuthorityIoDeviceControl;
config.EvtIddCxMonitorGetDefaultDescriptionModes = LGIddMonitorGetDefaultModes;
config.EvtIddCxMonitorAssignSwapChain = LGIddMonitorAssignSwapChain;
config.EvtIddCxMonitorUnassignSwapChain = LGIddMonitorUnassignSwapChain;
@@ -328,6 +607,16 @@ NTSTATUS LGIddCreateDevice(_Inout_ PWDFDEVICE_INIT deviceInit)
if (!NT_SUCCESS(status))
return status;
WDF_FILEOBJECT_CONFIG fileConfig;
WDF_FILEOBJECT_CONFIG_INIT(&fileConfig,
WDF_NO_EVENT_CALLBACK, WDF_NO_EVENT_CALLBACK,
LGIddAuthorityFileCleanup);
WDF_OBJECT_ATTRIBUTES fileAttributes;
WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE(
&fileAttributes, LGIddAuthorityFileContext);
WdfDeviceInitSetFileObjectConfig(
deviceInit, &fileConfig, &fileAttributes);
WDF_OBJECT_ATTRIBUTES deviceAttributes;
WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE(&deviceAttributes, CDeviceContextWrapper);
deviceAttributes.EvtCleanupCallback = [](WDFOBJECT object)
@@ -335,6 +624,7 @@ NTSTATUS LGIddCreateDevice(_Inout_ PWDFDEVICE_INIT deviceInit)
auto * wrapper = WdfObjectGet_CDeviceContextWrapper(object);
if (wrapper)
{
g_pipe.ClearClipboardAuthority();
g_pipe.SetDeviceContext(nullptr);
wrapper->Cleanup();
}
@@ -346,6 +636,15 @@ NTSTATUS LGIddCreateDevice(_Inout_ PWDFDEVICE_INIT deviceInit)
if (!NT_SUCCESS(status))
return status;
status = WdfDeviceCreateDeviceInterface(
device, &GUID_DEVINTERFACE_LGIdd, nullptr);
if (!NT_SUCCESS(status))
{
DEBUG_ERROR_HR(HRESULT_FROM_NT(status),
"Failed to create the LGIdd authority device interface");
return status;
}
/*
* Construct the device context and cache the WDF device BEFORE calling
* IddCxDeviceInitialize. IddCxDeviceInitialize arms the IddCx callbacks, and