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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

224
idd/LGCommon/CPipeEndpoint.cpp
View File

@@ -26,11 +26,13 @@
#include <stdint.h>
#include <vector>
const DWORD CPipeEndpoint::CLIENT_RETRY_INITIAL_MS = 100;
const DWORD CPipeEndpoint::CLIENT_RETRY_MAX_MS = 2000;
const DWORD CPipeEndpoint::SERVER_RETRY_MS = 1000;
const DWORD CPipeEndpoint::WRITE_TIMEOUT_MS = 250;
const DWORD CPipeEndpoint::WAIT_FIRST_OBJECT_VALUE = 0;
const DWORD CPipeEndpoint::CLIENT_RETRY_INITIAL_MS = 100;
const DWORD CPipeEndpoint::CLIENT_RETRY_MAX_MS = 2000;
const DWORD CPipeEndpoint::SERVER_RETRY_MS = 1000;
const DWORD CPipeEndpoint::AUTHENTICATION_TIMEOUT_MS = 2000;
const DWORD CPipeEndpoint::AUTHORIZATION_POLL_MS = 1000;
const DWORD CPipeEndpoint::WRITE_TIMEOUT_MS = 250;
const DWORD CPipeEndpoint::WAIT_FIRST_OBJECT_VALUE = 0;
bool CPipeEndpoint::IsDisconnectedError(DWORD error)
{
@@ -55,7 +57,12 @@ CPipeEndpoint::PipeIoResult CPipeEndpoint::WaitForOverlapped(
CancelIoEx(pipe, overlapped);
if (GetOverlappedResult(pipe, overlapped, transferred, TRUE))
return PipeIoResult::Success;
DEBUG_WARN("Named pipe write timed out");
const DWORD error = GetLastError();
if (error == ERROR_OPERATION_ABORTED)
return PipeIoResult::TimedOut;
if (IsDisconnectedError(error))
return PipeIoResult::Disconnected;
DEBUG_WARN_HR(error, "Failed to cancel timed-out named pipe I/O");
return PipeIoResult::Error;
}
@@ -94,7 +101,8 @@ CPipeEndpoint::PipeIoResult CPipeEndpoint::ReadMessage(
HANDLE ioEvent,
void * message,
DWORD messageSize,
DWORD * bytesRead)
DWORD * bytesRead,
DWORD timeoutMs)
{
ResetEvent(ioEvent);
OVERLAPPED overlapped = {};
@@ -106,7 +114,7 @@ CPipeEndpoint::PipeIoResult CPipeEndpoint::ReadMessage(
const DWORD error = GetLastError();
if (error == ERROR_IO_PENDING)
return WaitForOverlapped(
pipe, ioEvent, &overlapped, bytesRead);
pipe, ioEvent, &overlapped, bytesRead, timeoutMs);
if (error == ERROR_OPERATION_ABORTED &&
WaitForSingleObject(m_stopEvent, 0) == WAIT_FIRST_OBJECT_VALUE)
@@ -167,6 +175,8 @@ CPipeEndpoint::PipeIoResult CPipeEndpoint::WriteMessage(
bytesWritten);
result = PipeIoResult::Error;
}
else if (result == PipeIoResult::TimedOut)
DEBUG_WARN("Named pipe write timed out");
return result;
}
@@ -179,27 +189,39 @@ CPipeEndpoint::~CPipeEndpoint()
bool CPipeEndpoint::Start(
const wchar_t * pipeName,
Mode mode,
size_t messageSize)
size_t messageSize,
const SECURITY_ATTRIBUTES * serverSecurity,
DWORD serverOpenMode,
DWORD serverPipeMode)
{
Stop();
if (!pipeName || !*pipeName || !messageSize || messageSize > MAXDWORD)
return false;
m_pipeName = pipeName;
m_mode = mode;
m_messageSize = messageSize;
m_stopEvent = CreateEventW(nullptr, TRUE, FALSE, nullptr);
m_writeEvent = CreateEventW(nullptr, TRUE, FALSE, nullptr);
if (!m_stopEvent || !m_writeEvent)
m_pipeName = pipeName;
m_mode = mode;
m_messageSize = messageSize;
m_hasServerSecurity = serverSecurity != nullptr;
m_serverSecurity = serverSecurity ? *serverSecurity :
SECURITY_ATTRIBUTES {};
m_serverOpenMode = serverOpenMode;
m_serverPipeMode = serverPipeMode;
m_stopEvent = CreateEventW(nullptr, TRUE, FALSE, nullptr);
if (!m_stopEvent)
{
DEBUG_ERROR_HR(GetLastError(), "Failed to create named pipe events");
if (m_writeEvent)
CloseHandle(m_writeEvent);
if (m_stopEvent)
CloseHandle(m_stopEvent);
m_writeEvent = nullptr;
m_stopEvent = nullptr;
const DWORD error = GetLastError();
DEBUG_ERROR_HR(error, "Failed to create the named pipe stop event");
return false;
}
m_writeEvent = CreateEventW(nullptr, TRUE, FALSE, nullptr);
if (!m_writeEvent)
{
const DWORD error = GetLastError();
DEBUG_ERROR_HR(error, "Failed to create the named pipe write event");
CloseHandle(m_stopEvent);
m_stopEvent = nullptr;
return false;
}
@@ -287,6 +309,19 @@ void CPipeEndpoint::Stop()
Atomic::Store(m_connected, false);
}
void CPipeEndpoint::DisconnectClient()
{
Atomic::Store(m_connected, false);
CSRWSharedLock lock(m_pipeLock);
if (m_pipe != INVALID_HANDLE_VALUE &&
!CancelIoEx(m_pipe, nullptr))
{
const DWORD error = GetLastError();
if (error != ERROR_NOT_FOUND)
DEBUG_WARN_HR(error, "Failed to cancel named pipe client I/O");
}
}
bool CPipeEndpoint::Send(const void * message, size_t size)
{
if (!message || size != m_messageSize || !IsRunning() || !IsConnected())
@@ -340,13 +375,14 @@ HANDLE CPipeEndpoint::CreateServerPipe()
HANDLE pipe = CreateNamedPipeW(
m_pipeName.c_str(),
PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED | m_serverOpenMode,
PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT |
m_serverPipeMode,
1,
bufferSize,
bufferSize,
0,
nullptr);
m_hasServerSecurity ? &m_serverSecurity : nullptr);
if (pipe == INVALID_HANDLE_VALUE)
DEBUG_ERROR_HR(GetLastError(), "Failed to create named pipe %ls", m_pipeName.c_str());
return pipe;
@@ -420,13 +456,79 @@ void CPipeEndpoint::RunServer()
continue;
}
if (!IsRunning())
break;
if (!IsRunning() ||
WaitForSingleObject(m_stopEvent, 0) == WAIT_FIRST_OBJECT_VALUE)
break;
bool authenticated = false;
if (m_handler && m_handler->PipeClientAuthenticationRequired())
{
std::vector<uint8_t> message(m_messageSize);
DWORD bytesRead = 0;
const PipeIoResult authResult = ReadMessage(
pipe,
ioEvent,
message.data(),
static_cast<DWORD>(message.size()),
&bytesRead,
AUTHENTICATION_TIMEOUT_MS);
if (authResult == PipeIoResult::Success &&
bytesRead != message.size())
{
DEBUG_WARN(
"Named pipe authentication frame has %lu bytes, expected %llu",
bytesRead,
static_cast<unsigned long long>(message.size()));
}
if (authResult != PipeIoResult::Success ||
bytesRead != message.size() ||
!m_handler->AuthenticatePipeClient(
pipe, message.data(), message.size()))
{
if (authResult == PipeIoResult::TimedOut)
DEBUG_WARN("Named pipe client authentication timed out");
else if (authResult == PipeIoResult::Success)
DEBUG_WARN("Named pipe client authentication failed");
if (!DisconnectNamedPipe(pipe))
{
const DWORD error = GetLastError();
if (error != ERROR_PIPE_NOT_CONNECTED)
{
DEBUG_WARN_HR(error,
"Failed to disconnect unauthenticated named pipe client");
ClosePipe(pipe);
pipe = INVALID_HANDLE_VALUE;
}
}
if (authResult == PipeIoResult::Stopped || !IsRunning())
break;
continue;
}
authenticated = true;
}
if (!IsRunning() ||
WaitForSingleObject(m_stopEvent, 0) == WAIT_FIRST_OBJECT_VALUE ||
(m_handler && !m_handler->PipeClientStillAuthorized(pipe)))
{
if (authenticated && m_handler)
m_handler->OnPipeDisconnected();
if (!DisconnectNamedPipe(pipe))
{
const DWORD error = GetLastError();
if (error != ERROR_PIPE_NOT_CONNECTED)
{
DEBUG_WARN_HR(error,
"Failed to disconnect unauthorized named pipe client");
ClosePipe(pipe);
pipe = INVALID_HANDLE_VALUE;
}
}
if (!IsRunning())
break;
continue;
}
Atomic::Store(m_connected, true);
DEBUG_INFO("Named pipe client connected: %ls", m_pipeName.c_str());
if (m_handler)
@@ -494,7 +596,8 @@ void CPipeEndpoint::RunClient()
DWORD mode = PIPE_READMODE_MESSAGE;
if (!SetNamedPipeHandleState(pipe, &mode, nullptr, nullptr))
{
DEBUG_WARN_HR(GetLastError(), "Failed to set named pipe message mode");
const DWORD error = GetLastError();
DEBUG_WARN_HR(error, "Failed to set named pipe message mode");
CloseHandle(pipe);
if (!WaitForRetry(retryDelay))
break;
@@ -502,6 +605,50 @@ void CPipeEndpoint::RunClient()
continue;
}
if (m_handler && !m_handler->PipeServerIsAuthorized(pipe))
{
DEBUG_WARN("Rejected unauthorized named pipe server: %ls",
m_pipeName.c_str());
CloseHandle(pipe);
if (!WaitForRetry(retryDelay))
break;
retryDelay = (std::min)(retryDelay * 2, CLIENT_RETRY_MAX_MS);
continue;
}
if (!IsRunning() ||
WaitForSingleObject(m_stopEvent, 0) == WAIT_FIRST_OBJECT_VALUE)
{
CloseHandle(pipe);
break;
}
if (m_handler && m_handler->PipeClientHelloRequired())
{
std::vector<uint8_t> hello(m_messageSize);
if (!m_handler->BuildPipeClientHello(hello.data(), hello.size()))
{
DEBUG_WARN("Failed to build named pipe client HELLO");
CloseHandle(pipe);
if (!WaitForRetry(retryDelay))
break;
retryDelay = (std::min)(retryDelay * 2, CLIENT_RETRY_MAX_MS);
continue;
}
const PipeIoResult helloResult = WriteMessage(
pipe, hello.data(), static_cast<DWORD>(hello.size()));
if (helloResult != PipeIoResult::Success)
{
DEBUG_WARN("Failed to send named pipe client HELLO");
CloseHandle(pipe);
if (!WaitForRetry(retryDelay))
break;
retryDelay = (std::min)(retryDelay * 2, CLIENT_RETRY_MAX_MS);
continue;
}
}
if (!IsRunning() ||
WaitForSingleObject(m_stopEvent, 0) == WAIT_FIRST_OBJECT_VALUE)
{
@@ -549,7 +696,18 @@ bool CPipeEndpoint::ReadMessages(HANDLE pipe)
ioEvent,
message.data(),
static_cast<DWORD>(message.size()),
&bytesRead);
&bytesRead,
m_handler && m_handler->PipeClientAuthenticationRequired() ?
AUTHORIZATION_POLL_MS : INFINITE);
if (result == PipeIoResult::TimedOut)
{
if (m_handler && !m_handler->PipeClientStillAuthorized(pipe))
{
success = false;
break;
}
continue;
}
if (result != PipeIoResult::Success)
{
success = result == PipeIoResult::Disconnected ||
@@ -571,6 +729,12 @@ bool CPipeEndpoint::ReadMessages(HANDLE pipe)
WaitForSingleObject(m_stopEvent, 0) == WAIT_FIRST_OBJECT_VALUE)
break;
if (m_handler && !m_handler->PipeClientStillAuthorized(pipe))
{
success = false;
break;
}
if (m_handler && !m_handler->OnPipeMessage(
message.data(), message.size()))
{