1 files changed, 711 insertions, 0 deletions

diff --git a/server/proxy/channels/pf_channel_drdynvc.c b/server/proxy/channels/pf_channel_drdynvc.c
new file mode 100644
index 0000000..9d8cab9
--- /dev/null
+++ b/server/proxy/channels/pf_channel_drdynvc.c
@@ -0,0 +1,711 @@
+/**
+ * FreeRDP: A Remote Desktop Protocol Implementation
+ * pf_channel_drdynvc
+ *
+ * Copyright 2022 David Fort <contact@hardening-consulting.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <winpr/assert.h>
+
+#include <freerdp/channels/drdynvc.h>
+#include <freerdp/utils/drdynvc.h>
+#include <freerdp/server/proxy/proxy_log.h>
+
+#include "pf_channel_drdynvc.h"
+#include "../pf_channel.h"
+#include "../proxy_modules.h"
+#include "../pf_utils.h"
+
+#define DTAG PROXY_TAG("drdynvc")
+
+/** @brief channel opened status */
+typedef enum
+{
+	CHANNEL_OPENSTATE_WAITING_OPEN_STATUS, /*!< dynamic channel waiting for create response */
+	CHANNEL_OPENSTATE_OPENED,              /*!< opened */
+	CHANNEL_OPENSTATE_CLOSED               /*!< dynamic channel has been opened then closed */
+} PfDynChannelOpenStatus;
+
+typedef struct p_server_dynamic_channel_context pServerDynamicChannelContext;
+typedef struct DynChannelTrackerState DynChannelTrackerState;
+
+typedef PfChannelResult (*dynamic_channel_on_data_fn)(pServerContext* ps,
+                                                      pServerDynamicChannelContext* channel,
+                                                      BOOL isBackData, ChannelStateTracker* tracker,
+                                                      BOOL firstPacket, BOOL lastPacket);
+
+/** @brief tracker state for a drdynvc stream */
+struct DynChannelTrackerState
+{
+	UINT32 currentDataLength;
+	UINT32 CurrentDataReceived;
+	UINT32 CurrentDataFragments;
+	wStream* currentPacket;
+	dynamic_channel_on_data_fn dataCallback;
+};
+
+typedef void (*channel_data_dtor_fn)(void** user_data);
+
+struct p_server_dynamic_channel_context
+{
+	char* channelName;
+	UINT32 channelId;
+	PfDynChannelOpenStatus openStatus;
+	pf_utils_channel_mode channelMode;
+	BOOL packetReassembly;
+	DynChannelTrackerState backTracker;
+	DynChannelTrackerState frontTracker;
+
+	void* channelData;
+	channel_data_dtor_fn channelDataDtor;
+};
+
+/** @brief context for the dynamic channel */
+typedef struct
+{
+	wHashTable* channels;
+	ChannelStateTracker* backTracker;
+	ChannelStateTracker* frontTracker;
+	wLog* log;
+} DynChannelContext;
+
+/** @brief result of dynamic channel packet treatment */
+typedef enum
+{
+	DYNCVC_READ_OK,        /*!< read was OK */
+	DYNCVC_READ_ERROR,     /*!< an error happened during read */
+	DYNCVC_READ_INCOMPLETE /*!< missing bytes to read the complete packet */
+} DynvcReadResult;
+
+static const char* openstatus2str(PfDynChannelOpenStatus status)
+{
+	switch (status)
+	{
+		case CHANNEL_OPENSTATE_WAITING_OPEN_STATUS:
+			return "CHANNEL_OPENSTATE_WAITING_OPEN_STATUS";
+		case CHANNEL_OPENSTATE_CLOSED:
+			return "CHANNEL_OPENSTATE_CLOSED";
+		case CHANNEL_OPENSTATE_OPENED:
+			return "CHANNEL_OPENSTATE_OPENED";
+		default:
+			return "CHANNEL_OPENSTATE_UNKNOWN";
+	}
+}
+
+static PfChannelResult data_cb(pServerContext* ps, pServerDynamicChannelContext* channel,
+                               BOOL isBackData, ChannelStateTracker* tracker, BOOL firstPacket,
+                               BOOL lastPacket)
+{
+	WINPR_ASSERT(ps);
+	WINPR_ASSERT(channel);
+	WINPR_ASSERT(tracker);
+	WINPR_ASSERT(ps->pdata);
+
+	wStream* currentPacket = channelTracker_getCurrentPacket(tracker);
+	proxyDynChannelInterceptData dyn = { .name = channel->channelName,
+		                                 .channelId = channel->channelId,
+		                                 .data = currentPacket,
+		                                 .isBackData = isBackData,
+		                                 .first = firstPacket,
+		                                 .last = lastPacket,
+		                                 .rewritten = FALSE,
+		                                 .packetSize = channelTracker_getCurrentPacketSize(tracker),
+		                                 .result = PF_CHANNEL_RESULT_ERROR };
+	Stream_SealLength(dyn.data);
+	if (!pf_modules_run_filter(ps->pdata->module, FILTER_TYPE_INTERCEPT_CHANNEL, ps->pdata, &dyn))
+		return PF_CHANNEL_RESULT_ERROR;
+
+	channelTracker_setCurrentPacketSize(tracker, dyn.packetSize);
+	if (dyn.rewritten)
+		return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, !isBackData);
+	return dyn.result;
+}
+
+static pServerDynamicChannelContext* DynamicChannelContext_new(wLog* log, pServerContext* ps,
+                                                               const char* name, UINT32 id)
+{
+	WINPR_ASSERT(log);
+
+	pServerDynamicChannelContext* ret = calloc(1, sizeof(*ret));
+	if (!ret)
+	{
+		WLog_Print(log, WLOG_ERROR, "error allocating dynamic channel context '%s'", name);
+		return NULL;
+	}
+
+	ret->channelId = id;
+	ret->channelName = _strdup(name);
+	if (!ret->channelName)
+	{
+		WLog_Print(log, WLOG_ERROR, "error allocating name in dynamic channel context '%s'", name);
+		free(ret);
+		return NULL;
+	}
+
+	ret->frontTracker.dataCallback = data_cb;
+	ret->backTracker.dataCallback = data_cb;
+
+	proxyChannelToInterceptData dyn = { .name = name, .channelId = id, .intercept = FALSE };
+	if (pf_modules_run_filter(ps->pdata->module, FILTER_TYPE_DYN_INTERCEPT_LIST, ps->pdata, &dyn) &&
+	    dyn.intercept)
+		ret->channelMode = PF_UTILS_CHANNEL_INTERCEPT;
+	else
+		ret->channelMode = pf_utils_get_channel_mode(ps->pdata->config, name);
+	ret->openStatus = CHANNEL_OPENSTATE_OPENED;
+	ret->packetReassembly = (ret->channelMode == PF_UTILS_CHANNEL_INTERCEPT);
+
+	return ret;
+}
+
+static void DynamicChannelContext_free(void* ptr)
+{
+	pServerDynamicChannelContext* c = (pServerDynamicChannelContext*)ptr;
+	if (!c)
+		return;
+
+	if (c->backTracker.currentPacket)
+		Stream_Free(c->backTracker.currentPacket, TRUE);
+
+	if (c->frontTracker.currentPacket)
+		Stream_Free(c->frontTracker.currentPacket, TRUE);
+
+	if (c->channelDataDtor)
+		c->channelDataDtor(&c->channelData);
+
+	free(c->channelName);
+	free(c);
+}
+
+static UINT32 ChannelId_Hash(const void* key)
+{
+	const UINT32* v = (const UINT32*)key;
+	return *v;
+}
+
+static BOOL ChannelId_Compare(const void* objA, const void* objB)
+{
+	const UINT32* v1 = objA;
+	const UINT32* v2 = objB;
+	return (*v1 == *v2);
+}
+
+static DynvcReadResult dynvc_read_varInt(wLog* log, wStream* s, size_t len, UINT64* varInt,
+                                         BOOL last)
+{
+	WINPR_ASSERT(varInt);
+	switch (len)
+	{
+		case 0x00:
+			if (!Stream_CheckAndLogRequiredLengthWLog(log, s, 1))
+				return last ? DYNCVC_READ_ERROR : DYNCVC_READ_INCOMPLETE;
+			Stream_Read_UINT8(s, *varInt);
+			break;
+		case 0x01:
+			if (!Stream_CheckAndLogRequiredLengthWLog(log, s, 2))
+				return last ? DYNCVC_READ_ERROR : DYNCVC_READ_INCOMPLETE;
+			Stream_Read_UINT16(s, *varInt);
+			break;
+		case 0x02:
+			if (!Stream_CheckAndLogRequiredLengthWLog(log, s, 4))
+				return last ? DYNCVC_READ_ERROR : DYNCVC_READ_INCOMPLETE;
+			Stream_Read_UINT32(s, *varInt);
+			break;
+		case 0x03:
+		default:
+			WLog_Print(log, WLOG_ERROR, "Unknown int len %" PRIuz, len);
+			return DYNCVC_READ_ERROR;
+	}
+	return DYNCVC_READ_OK;
+}
+
+static PfChannelResult DynvcTrackerPeekFn(ChannelStateTracker* tracker, BOOL firstPacket,
+                                          BOOL lastPacket)
+{
+	BYTE cmd = 0;
+	BYTE byte0 = 0;
+	wStream* s = NULL;
+	wStream sbuffer;
+	BOOL haveChannelId = 0;
+	BOOL haveLength = 0;
+	UINT64 dynChannelId = 0;
+	UINT64 Length = 0;
+	pServerDynamicChannelContext* dynChannel = NULL;
+
+	WINPR_ASSERT(tracker);
+
+	DynChannelContext* dynChannelContext =
+	    (DynChannelContext*)channelTracker_getCustomData(tracker);
+	WINPR_ASSERT(dynChannelContext);
+
+	BOOL isBackData = (tracker == dynChannelContext->backTracker);
+	DynChannelTrackerState* trackerState = NULL;
+
+	UINT32 flags = lastPacket ? CHANNEL_FLAG_LAST : 0;
+	proxyData* pdata = channelTracker_getPData(tracker);
+	WINPR_ASSERT(pdata);
+
+	const char* direction = isBackData ? "B->F" : "F->B";
+
+	{
+		wStream* currentPacket = channelTracker_getCurrentPacket(tracker);
+		s = Stream_StaticConstInit(&sbuffer, Stream_Buffer(currentPacket),
+		                           Stream_GetPosition(currentPacket));
+	}
+
+	if (!Stream_CheckAndLogRequiredLengthWLog(dynChannelContext->log, s, 1))
+		return PF_CHANNEL_RESULT_ERROR;
+
+	Stream_Read_UINT8(s, byte0);
+	cmd = byte0 >> 4;
+
+	switch (cmd)
+	{
+		case CREATE_REQUEST_PDU:
+		case CLOSE_REQUEST_PDU:
+		case DATA_PDU:
+		case DATA_COMPRESSED_PDU:
+			haveChannelId = TRUE;
+			haveLength = FALSE;
+			break;
+		case DATA_FIRST_PDU:
+		case DATA_FIRST_COMPRESSED_PDU:
+			haveLength = TRUE;
+			haveChannelId = TRUE;
+			break;
+		default:
+			haveChannelId = FALSE;
+			haveLength = FALSE;
+			break;
+	}
+
+	if (haveChannelId)
+	{
+		BYTE cbId = byte0 & 0x03;
+
+		switch (dynvc_read_varInt(dynChannelContext->log, s, cbId, &dynChannelId, lastPacket))
+		{
+			case DYNCVC_READ_OK:
+				break;
+			case DYNCVC_READ_INCOMPLETE:
+				return PF_CHANNEL_RESULT_DROP;
+			case DYNCVC_READ_ERROR:
+			default:
+				WLog_Print(dynChannelContext->log, WLOG_ERROR,
+				           "DynvcTrackerPeekFn: invalid channelId field");
+				return PF_CHANNEL_RESULT_ERROR;
+		}
+
+		/* we always try to retrieve the dynamic channel in case it would have been opened
+		 * and closed
+		 */
+		dynChannel = (pServerDynamicChannelContext*)HashTable_GetItemValue(
+		    dynChannelContext->channels, &dynChannelId);
+		if (cmd != CREATE_REQUEST_PDU || !isBackData)
+		{
+			if (!dynChannel)
+			{
+				/* we've not found the target channel, so we drop this chunk, plus all the rest of
+				 * the packet */
+				channelTracker_setMode(tracker, CHANNEL_TRACKER_DROP);
+				return PF_CHANNEL_RESULT_DROP;
+			}
+		}
+	}
+
+	if (haveLength)
+	{
+		BYTE lenLen = (byte0 >> 2) & 0x03;
+		switch (dynvc_read_varInt(dynChannelContext->log, s, lenLen, &Length, lastPacket))
+		{
+			case DYNCVC_READ_OK:
+				break;
+			case DYNCVC_READ_INCOMPLETE:
+				return PF_CHANNEL_RESULT_DROP;
+			case DYNCVC_READ_ERROR:
+			default:
+				WLog_Print(dynChannelContext->log, WLOG_ERROR,
+				           "DynvcTrackerPeekFn: invalid length field");
+				return PF_CHANNEL_RESULT_ERROR;
+		}
+	}
+
+	switch (cmd)
+	{
+		case CAPABILITY_REQUEST_PDU:
+			WLog_Print(dynChannelContext->log, WLOG_DEBUG, "DynvcTracker: %s CAPABILITY_%s",
+			           direction, isBackData ? "REQUEST" : "RESPONSE");
+			channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
+			return PF_CHANNEL_RESULT_PASS;
+
+		case CREATE_REQUEST_PDU:
+		{
+			UINT32 creationStatus = 0;
+
+			/* we only want the full packet */
+			if (!lastPacket)
+				return PF_CHANNEL_RESULT_DROP;
+
+			if (isBackData)
+			{
+				proxyChannelDataEventInfo dev = { 0 };
+				const char* name = Stream_ConstPointer(s);
+				const size_t nameLen = Stream_GetRemainingLength(s);
+
+				const size_t len = strnlen(name, nameLen);
+				if ((len == 0) || (len == nameLen))
+					return PF_CHANNEL_RESULT_ERROR;
+
+				wStream* currentPacket = channelTracker_getCurrentPacket(tracker);
+				dev.channel_id = dynChannelId;
+				dev.channel_name = name;
+				dev.data = Stream_Buffer(s);
+				dev.data_len = Stream_GetPosition(currentPacket);
+				dev.flags = flags;
+				dev.total_size = Stream_GetPosition(currentPacket);
+
+				if (dynChannel)
+				{
+					WLog_Print(
+					    dynChannelContext->log, WLOG_WARN,
+					    "Reusing channel id %" PRIu32 ", previously %s [state %s, mode %s], now %s",
+					    dynChannel->channelId, dynChannel->channelName,
+					    openstatus2str(dynChannel->openStatus),
+					    pf_utils_channel_mode_string(dynChannel->channelMode), dev.channel_name);
+
+					HashTable_Remove(dynChannelContext->channels, &dynChannel->channelId);
+				}
+
+				if (!pf_modules_run_filter(pdata->module,
+				                           FILTER_TYPE_CLIENT_PASSTHROUGH_DYN_CHANNEL_CREATE, pdata,
+				                           &dev))
+					return PF_CHANNEL_RESULT_DROP; /* Silently drop */
+
+				dynChannel = DynamicChannelContext_new(dynChannelContext->log, pdata->ps, name,
+				                                       dynChannelId);
+				if (!dynChannel)
+				{
+					WLog_Print(dynChannelContext->log, WLOG_ERROR,
+					           "unable to create dynamic channel context data");
+					return PF_CHANNEL_RESULT_ERROR;
+				}
+
+				WLog_Print(dynChannelContext->log, WLOG_DEBUG, "Adding channel '%s'[%d]",
+				           dynChannel->channelName, dynChannel->channelId);
+				if (!HashTable_Insert(dynChannelContext->channels, &dynChannel->channelId,
+				                      dynChannel))
+				{
+					WLog_Print(dynChannelContext->log, WLOG_ERROR,
+					           "unable register dynamic channel context data");
+					DynamicChannelContext_free(dynChannel);
+					return PF_CHANNEL_RESULT_ERROR;
+				}
+
+				dynChannel->openStatus = CHANNEL_OPENSTATE_WAITING_OPEN_STATUS;
+
+				// NOLINTNEXTLINE(clang-analyzer-unix.Malloc): HashTable_Insert owns dynChannel
+				return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, FALSE);
+			}
+
+			/* CREATE_REQUEST_PDU response */
+			if (!Stream_CheckAndLogRequiredLengthWLog(dynChannelContext->log, s, 4))
+				return PF_CHANNEL_RESULT_ERROR;
+
+			Stream_Read_UINT32(s, creationStatus);
+			WLog_Print(dynChannelContext->log, WLOG_DEBUG,
+			           "DynvcTracker(%" PRIu64 ",%s): %s CREATE_RESPONSE openStatus=%" PRIu32,
+			           dynChannelId, dynChannel->channelName, direction, creationStatus);
+
+			if (creationStatus == 0)
+				dynChannel->openStatus = CHANNEL_OPENSTATE_OPENED;
+
+			return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, TRUE);
+		}
+
+		case CLOSE_REQUEST_PDU:
+			if (!lastPacket)
+				return PF_CHANNEL_RESULT_DROP;
+
+			WLog_Print(dynChannelContext->log, WLOG_DEBUG,
+			           "DynvcTracker(%s): %s Close request on channel", dynChannel->channelName,
+			           direction);
+			channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
+			if (dynChannel->openStatus != CHANNEL_OPENSTATE_OPENED)
+			{
+				WLog_Print(dynChannelContext->log, WLOG_WARN,
+				           "DynvcTracker(%s): is in state %s, expected %s", dynChannel->channelName,
+				           openstatus2str(dynChannel->openStatus),
+				           openstatus2str(CHANNEL_OPENSTATE_OPENED));
+			}
+			dynChannel->openStatus = CHANNEL_OPENSTATE_CLOSED;
+			return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, !isBackData);
+
+		case SOFT_SYNC_REQUEST_PDU:
+			/* just pass then as is for now */
+			WLog_Print(dynChannelContext->log, WLOG_DEBUG, "SOFT_SYNC_REQUEST_PDU");
+			channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
+			/*TODO: return pf_treat_softsync_req(pdata, s);*/
+			return PF_CHANNEL_RESULT_PASS;
+
+		case SOFT_SYNC_RESPONSE_PDU:
+			/* just pass then as is for now */
+			WLog_Print(dynChannelContext->log, WLOG_DEBUG, "SOFT_SYNC_RESPONSE_PDU");
+			channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
+			return PF_CHANNEL_RESULT_PASS;
+
+		case DATA_FIRST_PDU:
+		case DATA_PDU:
+			/* treat these below */
+			trackerState = isBackData ? &dynChannel->backTracker : &dynChannel->frontTracker;
+			break;
+
+		case DATA_FIRST_COMPRESSED_PDU:
+		case DATA_COMPRESSED_PDU:
+			WLog_Print(dynChannelContext->log, WLOG_DEBUG,
+			           "TODO: compressed data packets, pass them as is for now");
+			channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
+			return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, !isBackData);
+
+		default:
+			return PF_CHANNEL_RESULT_ERROR;
+	}
+
+	if (dynChannel->openStatus != CHANNEL_OPENSTATE_OPENED)
+	{
+		WLog_Print(dynChannelContext->log, WLOG_ERROR,
+		           "DynvcTracker(%s [%s]): channel is not opened", dynChannel->channelName,
+		           drdynvc_get_packet_type(cmd));
+		return PF_CHANNEL_RESULT_ERROR;
+	}
+
+	if ((cmd == DATA_FIRST_PDU) || (cmd == DATA_FIRST_COMPRESSED_PDU))
+	{
+		WLog_Print(dynChannelContext->log, WLOG_DEBUG,
+		           "DynvcTracker(%s [%s]): %s DATA_FIRST currentPacketLength=%" PRIu64 "",
+		           dynChannel->channelName, drdynvc_get_packet_type(cmd), direction, Length);
+		trackerState->currentDataLength = Length;
+		trackerState->CurrentDataReceived = 0;
+		trackerState->CurrentDataFragments = 0;
+
+		if (dynChannel->packetReassembly)
+		{
+			if (trackerState->currentPacket)
+				Stream_SetPosition(trackerState->currentPacket, 0);
+		}
+	}
+
+	if (cmd == DATA_PDU || cmd == DATA_FIRST_PDU)
+	{
+		size_t extraSize = Stream_GetRemainingLength(s);
+
+		trackerState->CurrentDataFragments++;
+		trackerState->CurrentDataReceived += extraSize;
+
+		if (dynChannel->packetReassembly)
+		{
+			if (!trackerState->currentPacket)
+			{
+				trackerState->currentPacket = Stream_New(NULL, 1024);
+				if (!trackerState->currentPacket)
+				{
+					WLog_Print(dynChannelContext->log, WLOG_ERROR,
+					           "unable to create current packet");
+					return PF_CHANNEL_RESULT_ERROR;
+				}
+			}
+
+			if (!Stream_EnsureRemainingCapacity(trackerState->currentPacket, extraSize))
+			{
+				WLog_Print(dynChannelContext->log, WLOG_ERROR, "unable to grow current packet");
+				return PF_CHANNEL_RESULT_ERROR;
+			}
+
+			Stream_Write(trackerState->currentPacket, Stream_ConstPointer(s), extraSize);
+		}
+		WLog_Print(dynChannelContext->log, WLOG_DEBUG,
+		           "DynvcTracker(%s [%s]): %s frags=%" PRIu32 " received=%" PRIu32 "(%" PRIu32 ")",
+		           dynChannel->channelName, drdynvc_get_packet_type(cmd), direction,
+		           trackerState->CurrentDataFragments, trackerState->CurrentDataReceived,
+		           trackerState->currentDataLength);
+	}
+
+	if (cmd == DATA_PDU)
+	{
+		if (trackerState->currentDataLength)
+		{
+			if (trackerState->CurrentDataReceived > trackerState->currentDataLength)
+			{
+				WLog_Print(dynChannelContext->log, WLOG_ERROR,
+				           "DynvcTracker (%s  [%s]): reassembled packet (%" PRIu32
+				           ") is bigger than announced length (%" PRIu32 ")",
+				           dynChannel->channelName, drdynvc_get_packet_type(cmd),
+				           trackerState->CurrentDataReceived, trackerState->currentDataLength);
+				return PF_CHANNEL_RESULT_ERROR;
+			}
+		}
+		else
+		{
+			trackerState->CurrentDataFragments = 0;
+			trackerState->CurrentDataReceived = 0;
+		}
+	}
+
+	PfChannelResult result = PF_CHANNEL_RESULT_ERROR;
+	switch (dynChannel->channelMode)
+	{
+		case PF_UTILS_CHANNEL_PASSTHROUGH:
+			result = channelTracker_flushCurrent(tracker, firstPacket, lastPacket, !isBackData);
+			break;
+		case PF_UTILS_CHANNEL_BLOCK:
+			channelTracker_setMode(tracker, CHANNEL_TRACKER_DROP);
+			result = PF_CHANNEL_RESULT_DROP;
+			break;
+		case PF_UTILS_CHANNEL_INTERCEPT:
+			if (trackerState->dataCallback)
+			{
+				result = trackerState->dataCallback(pdata->ps, dynChannel, isBackData, tracker,
+				                                    firstPacket, lastPacket);
+			}
+			else
+			{
+				WLog_Print(dynChannelContext->log, WLOG_ERROR,
+				           "no intercept callback for channel %s(fromBack=%d), dropping packet",
+				           dynChannel->channelName, isBackData);
+				result = PF_CHANNEL_RESULT_DROP;
+			}
+			break;
+		default:
+			WLog_Print(dynChannelContext->log, WLOG_ERROR, "unknown channel mode %d",
+			           dynChannel->channelMode);
+			result = PF_CHANNEL_RESULT_ERROR;
+			break;
+	}
+
+	if (!trackerState->currentDataLength ||
+	    (trackerState->CurrentDataReceived == trackerState->currentDataLength))
+	{
+		trackerState->currentDataLength = 0;
+		trackerState->CurrentDataFragments = 0;
+		trackerState->CurrentDataReceived = 0;
+
+		if (dynChannel->packetReassembly && trackerState->currentPacket)
+			Stream_SetPosition(trackerState->currentPacket, 0);
+	}
+
+	return result;
+}
+
+static void DynChannelContext_free(void* context)
+{
+	DynChannelContext* c = context;
+	if (!c)
+		return;
+	channelTracker_free(c->backTracker);
+	channelTracker_free(c->frontTracker);
+	HashTable_Free(c->channels);
+	free(c);
+}
+
+static const char* dynamic_context(void* arg)
+{
+	proxyData* pdata = arg;
+	if (!pdata)
+		return "pdata=null";
+	return pdata->session_id;
+}
+
+static DynChannelContext* DynChannelContext_new(proxyData* pdata,
+                                                pServerStaticChannelContext* channel)
+{
+	DynChannelContext* dyn = calloc(1, sizeof(DynChannelContext));
+	if (!dyn)
+		return FALSE;
+
+	dyn->log = WLog_Get(DTAG);
+	WINPR_ASSERT(dyn->log);
+	WLog_SetContext(dyn->log, dynamic_context, pdata);
+
+	dyn->backTracker = channelTracker_new(channel, DynvcTrackerPeekFn, dyn);
+	if (!dyn->backTracker)
+		goto fail;
+	if (!channelTracker_setPData(dyn->backTracker, pdata))
+		goto fail;
+
+	dyn->frontTracker = channelTracker_new(channel, DynvcTrackerPeekFn, dyn);
+	if (!dyn->frontTracker)
+		goto fail;
+	if (!channelTracker_setPData(dyn->frontTracker, pdata))
+		goto fail;
+
+	dyn->channels = HashTable_New(FALSE);
+	if (!dyn->channels)
+		goto fail;
+
+	if (!HashTable_SetHashFunction(dyn->channels, ChannelId_Hash))
+		goto fail;
+
+	wObject* kobj = HashTable_KeyObject(dyn->channels);
+	WINPR_ASSERT(kobj);
+	kobj->fnObjectEquals = ChannelId_Compare;
+
+	wObject* vobj = HashTable_ValueObject(dyn->channels);
+	WINPR_ASSERT(vobj);
+	vobj->fnObjectFree = DynamicChannelContext_free;
+
+	return dyn;
+
+fail:
+	DynChannelContext_free(dyn);
+	return NULL;
+}
+
+static PfChannelResult pf_dynvc_back_data(proxyData* pdata,
+                                          const pServerStaticChannelContext* channel,
+                                          const BYTE* xdata, size_t xsize, UINT32 flags,
+                                          size_t totalSize)
+{
+	WINPR_ASSERT(channel);
+
+	DynChannelContext* dyn = (DynChannelContext*)channel->context;
+	WINPR_UNUSED(pdata);
+	WINPR_ASSERT(dyn);
+
+	return channelTracker_update(dyn->backTracker, xdata, xsize, flags, totalSize);
+}
+
+static PfChannelResult pf_dynvc_front_data(proxyData* pdata,
+                                           const pServerStaticChannelContext* channel,
+                                           const BYTE* xdata, size_t xsize, UINT32 flags,
+                                           size_t totalSize)
+{
+	WINPR_ASSERT(channel);
+
+	DynChannelContext* dyn = (DynChannelContext*)channel->context;
+	WINPR_UNUSED(pdata);
+	WINPR_ASSERT(dyn);
+
+	return channelTracker_update(dyn->frontTracker, xdata, xsize, flags, totalSize);
+}
+
+BOOL pf_channel_setup_drdynvc(proxyData* pdata, pServerStaticChannelContext* channel)
+{
+	DynChannelContext* ret = DynChannelContext_new(pdata, channel);
+	if (!ret)
+		return FALSE;
+
+	channel->onBackData = pf_dynvc_back_data;
+	channel->onFrontData = pf_dynvc_front_data;
+	channel->contextDtor = DynChannelContext_free;
+	channel->context = ret;
+	return TRUE;
+}