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")
 
#define Stream_CheckAndLogRequiredLengthWLogWithBackend(log, s, nmemb, backdata)                 \
  Stream_CheckAndLogRequiredLengthWLogEx(log, WLOG_WARN, s, nmemb, 1, "%s(%s:%" PRIuz ")[%s]", \
                                         __func__, __FILE__, (size_t)__LINE__,                 \
                                         getDirection(backdata))
 
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";
  }
}
 
#define DynvcTrackerLog(log, level, dynChannel, cmd, isBackData, ...)                         \
  dyn_log_((log), (level), (dynChannel), (cmd), (isBackData), __func__, __FILE__, __LINE__, \
           __VA_ARGS__)
 
static const char* getDirection(BOOL isBackData)
{
  return isBackData ? "B->F" : "F->B";
}
 
static void dyn_log_(wLog* log, DWORD level, const pServerDynamicChannelContext* dynChannel,
                     BYTE cmd, BOOL isBackData, const char* fkt, const char* file, size_t line,
                     const char* fmt, ...)
{
  if (!WLog_IsLevelActive(log, level))
    return;
 
  char* prefix = NULL;
  char* msg = NULL;
  size_t prefixlen = 0;
  size_t msglen = 0;
 
  uint32_t channelId = dynChannel ? dynChannel->channelId : UINT32_MAX;
  const char* channelName = dynChannel ? dynChannel->channelName : "<NULL>";
  (void)winpr_asprintf(&prefix, &prefixlen, "DynvcTracker[%s](%s [%s:%" PRIu32 "])",
                       getDirection(isBackData), channelName, drdynvc_get_packet_type(cmd),
                       channelId);
 
  va_list ap;
  va_start(ap, fmt);
  (void)winpr_vasprintf(&msg, &msglen, fmt, ap);
  va_end(ap);
 
  WLog_PrintTextMessage(log, level, line, file, fkt, "%s: %s", prefix, msg);
  free(prefix);
  free(msg);
}
 
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 DynvcTrackerPeekHandleByMode(ChannelStateTracker* tracker,
                                                    DynChannelTrackerState* trackerState,
                                                    pServerDynamicChannelContext* dynChannel,
                                                    BYTE cmd, BOOL firstPacket, BOOL lastPacket)
{
  WINPR_ASSERT(tracker);
  WINPR_ASSERT(trackerState);
  WINPR_ASSERT(dynChannel);
  PfChannelResult result = PF_CHANNEL_RESULT_ERROR;
 
  DynChannelContext* dynChannelContext =
      (DynChannelContext*)channelTracker_getCustomData(tracker);
  WINPR_ASSERT(dynChannelContext);
 
  proxyData* pdata = channelTracker_getPData(tracker);
  WINPR_ASSERT(pdata);
 
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
  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
      {
        DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                        "no intercept callback for channel, dropping packet");
        result = PF_CHANNEL_RESULT_DROP;
      }
      break;
    default:
      DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                      "unknown channel mode %u", 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 PfChannelResult DynvcTrackerHandleClose(ChannelStateTracker* tracker,
                                               pServerDynamicChannelContext* dynChannel,
                                               DynChannelContext* dynChannelContext,
                                               BOOL firstPacket, BOOL lastPacket)
{
  WINPR_ASSERT(dynChannelContext);
 
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
 
  if (!lastPacket || !dynChannel)
    return PF_CHANNEL_RESULT_DROP;
 
  DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, CLOSE_REQUEST_PDU, isBackData,
                  "Close request");
  channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
  if (dynChannel->openStatus != CHANNEL_OPENSTATE_OPENED)
  {
    DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, CLOSE_REQUEST_PDU,
                    isBackData, "is in state %s, expected %s",
                    openstatus2str(dynChannel->openStatus),
                    openstatus2str(CHANNEL_OPENSTATE_OPENED));
  }
  dynChannel->openStatus = CHANNEL_OPENSTATE_CLOSED;
  return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, !isBackData);
}
 
static PfChannelResult DynvcTrackerHandleCreateBack(ChannelStateTracker* tracker, wStream* s,
                                                    DWORD flags, proxyData* pdata,
                                                    pServerDynamicChannelContext* dynChannel,
                                                    DynChannelContext* dynChannelContext,
                                                    UINT64 dynChannelId)
{
  proxyChannelDataEventInfo dev = { 0 };
  const char* name = Stream_ConstPointer(s);
  const size_t nameLen = Stream_GetRemainingLength(s);
  const size_t len = strnlen(name, nameLen);
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
  const BYTE cmd = CREATE_REQUEST_PDU;
 
  if ((len == 0) || (len == nameLen) || (dynChannelId > UINT16_MAX))
  {
    char namebuffer[64] = { 0 };
    (void)_snprintf(namebuffer, sizeof(namebuffer) - 1, "%s", name);
 
    DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                    "channel id %" PRIu64 ", name=%s [%" PRIuz "|%" PRIuz "], status=%s",
                    dynChannelId, namebuffer, len, nameLen,
                    dynChannel ? openstatus2str(dynChannel->openStatus) : "NULL");
    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)
  {
    DynvcTrackerLog(dynChannelContext->log, WLOG_WARN, dynChannel, cmd, isBackData,
                    "Reusing channel id, now %s", 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)
  {
    DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                    "unable to create dynamic channel context data");
    return PF_CHANNEL_RESULT_ERROR;
  }
 
  DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                  "Adding channel");
  if (!HashTable_Insert(dynChannelContext->channels, &dynChannel->channelId, dynChannel))
  {
    DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                    "unable register dynamic channel context data");
    DynamicChannelContext_free(dynChannel);
    return PF_CHANNEL_RESULT_ERROR;
  }
 
  dynChannel->openStatus = CHANNEL_OPENSTATE_WAITING_OPEN_STATUS;
 
  const BOOL firstPacket = (flags & CHANNEL_FLAG_FIRST) ? TRUE : FALSE;
  const BOOL lastPacket = (flags & CHANNEL_FLAG_LAST) ? TRUE : FALSE;
 
  // NOLINTNEXTLINE(clang-analyzer-unix.Malloc): HashTable_Insert owns dynChannel
  return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, FALSE);
}
 
static PfChannelResult DynvcTrackerHandleCreateFront(ChannelStateTracker* tracker, wStream* s,
                                                     DWORD flags,
                                                     WINPR_ATTR_UNUSED proxyData* pdata,
                                                     pServerDynamicChannelContext* dynChannel,
                                                     DynChannelContext* dynChannelContext,
                                                     WINPR_ATTR_UNUSED UINT64 dynChannelId)
{
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
  const BYTE cmd = CREATE_REQUEST_PDU;
 
  /* CREATE_REQUEST_PDU response */
  if (!Stream_CheckAndLogRequiredLengthWLogWithBackend(dynChannelContext->log, s, 4, FALSE))
    return PF_CHANNEL_RESULT_ERROR;
 
  const UINT32 creationStatus = Stream_Get_UINT32(s);
  DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                  "CREATE_RESPONSE openStatus=%" PRIu32, creationStatus);
 
  if (dynChannel && (creationStatus == 0))
    dynChannel->openStatus = CHANNEL_OPENSTATE_OPENED;
 
  const BOOL firstPacket = (flags & CHANNEL_FLAG_FIRST) ? TRUE : FALSE;
  const BOOL lastPacket = (flags & CHANNEL_FLAG_LAST) ? TRUE : FALSE;
 
  return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, TRUE);
}
 
static PfChannelResult DynvcTrackerHandleCreate(ChannelStateTracker* tracker, wStream* s,
                                                DWORD flags,
                                                pServerDynamicChannelContext* dynChannel,
                                                UINT64 dynChannelId)
{
  WINPR_ASSERT(tracker);
  WINPR_ASSERT(s);
 
  DynChannelContext* dynChannelContext =
      (DynChannelContext*)channelTracker_getCustomData(tracker);
  WINPR_ASSERT(dynChannelContext);
 
  const BOOL lastPacket = (flags & CHANNEL_FLAG_LAST) ? TRUE : FALSE;
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
 
  proxyData* pdata = channelTracker_getPData(tracker);
  WINPR_ASSERT(pdata);
 
  /* we only want the full packet */
  if (!lastPacket)
    return PF_CHANNEL_RESULT_DROP;
 
  if (isBackData)
    return DynvcTrackerHandleCreateBack(tracker, s, flags, pdata, dynChannel, dynChannelContext,
                                        dynChannelId);
 
  return DynvcTrackerHandleCreateFront(tracker, s, flags, pdata, dynChannel, dynChannelContext,
                                       dynChannelId);
}
 
static PfChannelResult DynvcTrackerHandleCmdDATA(ChannelStateTracker* tracker,
                                                 pServerDynamicChannelContext* dynChannel,
                                                 wStream* s, BYTE cmd, UINT64 Length,
                                                 BOOL firstPacket, BOOL lastPacket)
{
  WINPR_ASSERT(tracker);
  WINPR_ASSERT(s);
 
  DynChannelContext* dynChannelContext =
      (DynChannelContext*)channelTracker_getCustomData(tracker);
  WINPR_ASSERT(dynChannelContext);
 
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
 
  if (!dynChannel)
  {
    DynvcTrackerLog(dynChannelContext->log, WLOG_WARN, dynChannel, cmd, isBackData,
                    "channel is NULL, dropping packet");
    return PF_CHANNEL_RESULT_DROP;
  }
 
  DynChannelTrackerState* trackerState =
      isBackData ? &dynChannel->backTracker : &dynChannel->frontTracker;
  if (dynChannel->openStatus != CHANNEL_OPENSTATE_OPENED)
  {
    DynvcTrackerLog(dynChannelContext->log, WLOG_WARN, dynChannel, cmd, isBackData,
                    "channel is not opened, dropping packet");
    return PF_CHANNEL_RESULT_DROP;
  }
 
  switch (cmd)
  {
    case DATA_FIRST_PDU:
    case DATA_FIRST_COMPRESSED_PDU:
    {
      DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                      "DATA_FIRST currentPacketLength=%" PRIu64 "", Length);
      if (Length > UINT32_MAX)
      {
        DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                        "Length out of bounds: %" PRIu64, Length);
        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);
      }
    }
    break;
    default:
      break;
  }
 
  switch (cmd)
  {
    case DATA_PDU:
    case DATA_FIRST_PDU:
    {
      size_t extraSize = Stream_GetRemainingLength(s);
 
      trackerState->CurrentDataFragments++;
      trackerState->CurrentDataReceived += WINPR_ASSERTING_INT_CAST(uint32_t, extraSize);
 
      if (dynChannel->packetReassembly)
      {
        if (!trackerState->currentPacket)
        {
          trackerState->currentPacket = Stream_New(NULL, 1024);
          if (!trackerState->currentPacket)
          {
            DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd,
                            isBackData, "unable to create current packet",
                            getDirection(isBackData), dynChannel->channelName,
                            drdynvc_get_packet_type(cmd));
            return PF_CHANNEL_RESULT_ERROR;
          }
        }
 
        if (!Stream_EnsureRemainingCapacity(trackerState->currentPacket, extraSize))
        {
          DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                          "unable to grow current packet", getDirection(isBackData),
                          dynChannel->channelName, drdynvc_get_packet_type(cmd));
          return PF_CHANNEL_RESULT_ERROR;
        }
 
        Stream_Write(trackerState->currentPacket, Stream_ConstPointer(s), extraSize);
      }
      DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                      "frags=%" PRIu32 " received=%" PRIu32 "(%" PRIu32 ")",
                      trackerState->CurrentDataFragments, trackerState->CurrentDataReceived,
                      trackerState->currentDataLength);
    }
    break;
    default:
      break;
  }
 
  switch (cmd)
  {
    case DATA_PDU:
    {
      if (trackerState->currentDataLength)
      {
        if (trackerState->CurrentDataReceived > trackerState->currentDataLength)
        {
          DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                          "reassembled packet (%" PRIu32
                          ") is bigger than announced length (%" PRIu32 ")",
                          trackerState->CurrentDataReceived,
                          trackerState->currentDataLength);
          return PF_CHANNEL_RESULT_ERROR;
        }
      }
      else
      {
        trackerState->CurrentDataFragments = 0;
        trackerState->CurrentDataReceived = 0;
      }
    }
    break;
    default:
      break;
  }
 
  return DynvcTrackerPeekHandleByMode(tracker, trackerState, dynChannel, cmd, firstPacket,
                                      lastPacket);
}
 
static PfChannelResult DynvcTrackerHandleCmd(ChannelStateTracker* tracker,
                                             pServerDynamicChannelContext* dynChannel, wStream* s,
                                             BYTE cmd, UINT32 flags, UINT64 Length,
                                             UINT64 dynChannelId, BOOL firstPacket, BOOL lastPacket)
{
  WINPR_ASSERT(tracker);
  WINPR_ASSERT(s);
 
  DynChannelContext* dynChannelContext =
      (DynChannelContext*)channelTracker_getCustomData(tracker);
  WINPR_ASSERT(dynChannelContext);
 
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
  switch (cmd)
  {
    case CAPABILITY_REQUEST_PDU:
      DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                      "CAPABILITY_%s", isBackData ? "REQUEST" : "RESPONSE");
      channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
      return PF_CHANNEL_RESULT_PASS;
 
    case CREATE_REQUEST_PDU:
      return DynvcTrackerHandleCreate(tracker, s, flags, dynChannel, dynChannelId);
 
    case CLOSE_REQUEST_PDU:
      return DynvcTrackerHandleClose(tracker, dynChannel, dynChannelContext, firstPacket,
                                     lastPacket);
 
    case SOFT_SYNC_REQUEST_PDU:
      /* just pass then as is for now */
      DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                      "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 */
      DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                      "SOFT_SYNC_RESPONSE_PDU");
      channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
      return PF_CHANNEL_RESULT_PASS;
 
    case DATA_FIRST_PDU:
    case DATA_PDU:
      return DynvcTrackerHandleCmdDATA(tracker, dynChannel, s, cmd, Length, firstPacket,
                                       lastPacket);
 
    case DATA_FIRST_COMPRESSED_PDU:
    case DATA_COMPRESSED_PDU:
      DynvcTrackerLog(dynChannelContext->log, WLOG_DEBUG, dynChannel, cmd, isBackData,
                      "TODO: compressed data packets, pass them as is for now");
      channelTracker_setMode(tracker, CHANNEL_TRACKER_PASS);
      return channelTracker_flushCurrent(tracker, firstPacket, lastPacket, !isBackData);
 
    default:
      DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                      "Invalid command ID");
      return PF_CHANNEL_RESULT_ERROR;
  }
}
 
static PfChannelResult DynvcTrackerPeekFn(ChannelStateTracker* tracker, BOOL firstPacket,
                                          BOOL lastPacket)
{
  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);
 
  const BOOL isBackData = (tracker == dynChannelContext->backTracker);
 
  UINT32 flags = lastPacket ? CHANNEL_FLAG_LAST : 0;
  if (firstPacket)
    flags |= CHANNEL_FLAG_FIRST;
  proxyData* pdata = channelTracker_getPData(tracker);
  WINPR_ASSERT(pdata);
 
  {
    wStream* currentPacket = channelTracker_getCurrentPacket(tracker);
    s = Stream_StaticConstInit(&sbuffer, Stream_Buffer(currentPacket),
                               Stream_GetPosition(currentPacket));
  }
 
  if (!Stream_CheckAndLogRequiredLengthWLogWithBackend(dynChannelContext->log, s, 1, isBackData))
    return PF_CHANNEL_RESULT_ERROR;
 
  const BYTE byte0 = Stream_Get_UINT8(s);
  const BYTE 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:
        DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                        "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:
        DynvcTrackerLog(dynChannelContext->log, WLOG_ERROR, dynChannel, cmd, isBackData,
                        "invalid length field");
        return PF_CHANNEL_RESULT_ERROR;
    }
  }
 
  return DynvcTrackerHandleCmd(tracker, dynChannel, s, cmd, flags, Length, dynChannelId,
                               firstPacket, lastPacket);
}
 
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 NULL;
 
  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;
}