pf_channel_drdynvc.c

 
#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")
 
typedef enum
{
  CHANNEL_OPENSTATE_WAITING_OPEN_STATUS, 
  CHANNEL_OPENSTATE_OPENED,              
  CHANNEL_OPENSTATE_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);
 
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;
};
 
typedef struct
{
  wHashTable* channels;
  ChannelStateTracker* backTracker;
  ChannelStateTracker* frontTracker;
  wLog* log;
} DynChannelContext;
 
typedef enum
{
  DYNCVC_READ_OK,        
  DYNCVC_READ_ERROR,     
  DYNCVC_READ_INCOMPLETE 
} 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 || (dynChannel->openStatus == CHANNEL_OPENSTATE_CLOSED))
      {
        /* 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) || (dynChannelId > UINT16_MAX))
          return PF_CHANNEL_RESULT_ERROR;
 
        wStream* currentPacket = channelTracker_getCurrentPacket(tracker);
        dev.channel_id = (UINT16)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,
                                               (UINT32)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);
    if (Length > UINT32_MAX)
      return PF_CHANNEL_RESULT_ERROR;
    trackerState->currentDataLength = (UINT32)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;
}