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is it possible to get that port redirect dynamically upon startup of “my_app”?
WinpkFilter driver should be installed on the system before hand. But in any case you start filtering/redirecting packets only when your application is active and stop this when your application is terminated. So the answer is YES.
is there a chance to configure windows’ firewall to redirect data sent from an external interface to port 25 to our port 10025?
Windows built-in firewall does not support port redirecting services.
does anyone have an idea how to solve this EXCEPT using custom LSP/TDI/NDIS drivers?
Regretfully there is no other way. You can use WinpkFilter library (http://www.ntkernel.com/w&p.php?id=7) to implement port redirector solution though.
can I paste a link here that would be for a Simple Stupid Firewall that I made using winpkfilter example (PacketSniffer and PassThru)
Sure, you can.
Проблема в том, что это драйвер-фильтр
В смысле Intermediate?
Где можно выполнять запросы OID, в OnSend, OnReceive, OnInitialize, OnHalt?
В общем случае запросы можно делать как только нижележащий драйвер готов их обрабатывать и до того как он перестает это делать (то есть OnInitialize и OnHalt использовать пожалуй не очень разумно).
В общем случае нужно следить только за IRQL “Callers of NdisRequest can be running at IRQL <= DISPATCH_LEVEL" и руководстоваться тем когда эта самая статистика нужна.
Anyway, is it ok to have an Article on the subject we treat here with my Application as a solution and a link to the WinpkFilter run-time libraries that are presented on
http://www.ntkernel.com/w&p.php?id=7
or it is in violation of the license agreement?
It is OK to do so. Good luck with your article and hope you will post a link to it here. If you are interested we can also publish it on this web-site.
This is TCP checksum in C, I suppose you should be able to translate to Delphi
//
// Function recalculates TCP checksum
//
VOID
RecalculateTCPChecksum (
PINTERMEDIATE_BUFFER pPacket
)
{
tcphdr_ptr pTcpHeader = NULL;
unsigned short word16, padd = 0;
unsigned int i, sum = 0;
PUCHAR buff;
DWORD dwTcpLen;
iphdr_ptr pIpHeader = (iphdr_ptr)&pPacket->m_IBuffer[sizeof(ether_header)];
// Sanity check
if (pIpHeader->ip_p == IPPROTO_TCP)
{
pTcpHeader = (tcphdr_ptr)(((PUCHAR)pIpHeader) + sizeof(DWORD)*pIpHeader->ip_hl);
}
else
return;
dwTcpLen = ntohs(pIpHeader->ip_len) - pIpHeader->ip_hl*4;//pPacket->m_Length - ((PUCHAR)(pTcpHeader) - pPacket->m_IBuffer);
if ( (dwTcpLen/2)*2 != dwTcpLen )
{
padd=1;
pPacket->m_IBuffer[dwTcpLen + pIpHeader->ip_hl*4 + sizeof(ether_header)] = 0;
}
buff = (PUCHAR)pTcpHeader;
pTcpHeader->th_sum = 0;
// make 16 bit words out of every two adjacent 8 bit words and
// calculate the sum of all 16 vit words
for (i=0; i< dwTcpLen+padd; i=i+2){
word16 =((buff<<8)&0xFF00)+(buff[i+1]&0xFF);
sum = sum + (unsigned long)word16;
}
// add the TCP pseudo header which contains:
// the IP source and destination addresses,
sum = sum + ntohs(pIpHeader->ip_src.S_un.S_un_w.s_w1) + ntohs(pIpHeader->ip_src.S_un.S_un_w.s_w2);
sum = sum + ntohs(pIpHeader->ip_dst.S_un.S_un_w.s_w1) + ntohs(pIpHeader->ip_dst.S_un.S_un_w.s_w2);
// the protocol number and the length of the TCP packet
sum = sum + IPPROTO_TCP + (unsigned short)dwTcpLen;
// keep only the last 16 bits of the 32 bit calculated sum and add the carries
while (sum>>16)
sum = (sum & 0xFFFF)+(sum >> 16);
// Take the one's complement of sum
sum = ~sum;
pTcpHeader->th_sum = htons((unsigned short)sum);
}i’ve tried to change destination ip of ipheader, then recalculate checksum but it didn’t work
You should modify destination IP address in the potgoing packet to redirect address and recalculate packet checksums (both IP and TCP). You should do the reverse operation in the incoming packet associated with the connection you modify.
Is it possible to unaccept a certain kind of packet(e.g. packets with the same source IP addr) just using the use-mode APIs provided in WinpkFilter?
You mean drop these packets? If so then yes you can just skip reinjecting into the stack API calls (SendPacketToMstcp, SendPacketToAdapter) for these packets.
I wonder if the Net Firewall supports a simple one to many NAT.
One to many NAT is not implemented in the current version of NeT Firewall.
if we detect some harmful site(http packet) in winpkfilter we redirect alert site.
Since connection to the harmful site already established it can’t be easily redirected (normally redirection should occure during connection establishment). However, you can terminate connection to the harmful site and drop all packet to/from it, alert user about harmful site, redirect all newly established HTTP user sessions from the registered harmful site to the alert site and etc…
Пишу TDI-фильтр для устройства TCP. Задача фильтра — определять и собирать в буфер сообщения HTTP с последующей выдачей наверх приложению Win32. Через обработчик TDI_SEND может проходить как полноформатное HTTP сообщение, так и отдельные куски, вплоть до отдельных байтов. Интересует вопрос, есть ли способы корректно определить, что передаваемое побайтно сообщение именно HTTP, а не что-то другое.
На уровне TDI все выглядит точно так же как и в обычном сокете, так что есть ли способ по куску данных случайно выхваченого из потока данных сокета достоверно определить HTTP протокол? Маловероятно, если только этот кусок не достаточно велик чтобы содержать достоверные сигнатуры HTTP (заголовки запросов/ответов например). Можно еще смотреть на порты, но вообще говоря HTTP сервер не обязан работать на 80 порту. Единственный достоверный способ – это анализировать весь поток данных, выбирать и опознавать HTTP заголовки.
I am just running the examples, PassThru and PacketSniffer only.
but its not sniffing in the XP-bridge mode.
Well it works OK in test environment and you are the first one who reported problems like this. Could you provide the complete details about it? It would be good if you provide ipconfig output, listadapters output and how do you start passthru sample (with it’s output compared to some other tool which shows you packets). Some broken functionality can be alo caused by installed firewall or some sort of other low level network software.
Also, which version of WinpkFilter are you using?
Can you provide some C code for this purpose ?
The routine below is taken from the Internet Gateway source and implements NAT processing:
unsigned __stdcall CsnatDlg::StartNAT ( void* pArguments )
{
CsnatDlg* pDlg = (CsnatDlg*)pArguments;
HANDLE hEvents[ADAPTER_LIST_SIZE + 1];
CNetworkInterface* hAdapters [ADAPTER_LIST_SIZE + 1];
CNetworkInterface *pNetCard, *pProviderCard;
unsigned dwActiveAdaptersCount = 1;
ADAPTER_MODE Mode;
ETH_REQUEST Request;
INTERMEDIATE_BUFFER PacketBuffer;
DWORD dwWait, dwIndex;
ether_header* pEthHeader;
iphdr* pIpHeader;
tcphdr* pTcpHeader;
udphdr* pUdpHeader;
Mode.dwFlags = MSTCP_FLAG_SENT_TUNNEL|MSTCP_FLAG_RECV_TUNNEL;
hEvents[0] = pDlg->m_hNATTerminateEvent;
// Walk adapters list and initialize provider and clients interfaces
POSITION pos = pDlg->m_NetCardsList.GetHeadPosition();
for (unsigned i = 0; i < pDlg->m_dwAdapterCount; ++i)
{
pNetCard = (CNetworkInterface*)pDlg->m_NetCardsList.GetNext(pos);
if ((pNetCard->m_NATState == CLIENT) || (pNetCard->m_NATState == PROVIDER))
{
hAdapters[dwActiveAdaptersCount] = pNetCard;
hEvents[dwActiveAdaptersCount] = ::CreateEvent(NULL, TRUE, FALSE, NULL);
pDlg->m_NdisApi.SetPacketEvent(pNetCard->m_hAdapter, hEvents[dwActiveAdaptersCount]);
Mode.hAdapterHandle = pNetCard->m_hAdapter;
pDlg->m_NdisApi.SetAdapterMode(&Mode);
dwActiveAdaptersCount++;
if(pNetCard->m_NATState == PROVIDER)
pProviderCard = pNetCard;
}
}
// Initialize Request
ZeroMemory ( &Request, sizeof(ETH_REQUEST) );
ZeroMemory ( &PacketBuffer, sizeof(INTERMEDIATE_BUFFER) );
Request.EthPacket.Buffer = &PacketBuffer;
do
{
dwWait = ::WaitForMultipleObjects(
dwActiveAdaptersCount,
hEvents,
FALSE,
INFINITE
);
dwIndex = dwWait - WAIT_OBJECT_0;
if (!dwIndex)
continue;
::ResetEvent(hEvents[dwIndex]);
Request.hAdapterHandle = hAdapters[dwIndex]->m_hAdapter;
// Read all queued packets from the specified interface
while(pDlg->m_NdisApi.ReadPacket(&Request))
{
pEthHeader = (ether_header*)PacketBuffer.m_IBuffer;
if ( ntohs(pEthHeader->h_proto) == ETH_P_IP )
{
pIpHeader = (iphdr*)(PacketBuffer.m_IBuffer + ETHER_HEADER_LENGTH);
// Check if connection is established from local system (we don't do NAT processing
// for local system)
BOOL bIsLocalAddress = hAdapters[dwIndex]->IsLocalAddress(&pIpHeader->ip_src);
if (bIsLocalAddress && (PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_SEND))
{
// Place packet on the network interface
pDlg->m_NdisApi.SendPacketToAdapter(&Request);
continue;
}
// TCP packet processing
if (pIpHeader->ip_p == IPPROTO_TCP)
{
// This is TCP packet, get TCP header pointer
pTcpHeader = (tcphdr*)(((PUCHAR)pIpHeader) + sizeof(DWORD)*pIpHeader->ip_hl);
// Outgoing TCP packets processing
if ((hAdapters[dwIndex]->m_NATState == PROVIDER)&&
(PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_SEND))
{
CPortNATEntry* pTcpNE = NULL;
if (pTcpHeader->th_flags == TH_SYN)
{
// New TCP connnection established, allocate dynamic NAT entry
pTcpNE = pDlg->m_TcpNatTable.Allocate(pIpHeader->ip_src, pTcpHeader->th_sport, pIpHeader->ip_dst, pTcpHeader->th_dport);
if(pTcpNE)
{
pTcpNE->m_IpNAT = hAdapters[dwIndex]->m_NATIp;
}
}
else
{
// Try to locate xisting NAT entry
pTcpNE = pDlg->m_TcpNatTable.Find(pIpHeader->ip_src, pTcpHeader->th_sport, pIpHeader->ip_dst, pTcpHeader->th_dport);
}
if (pTcpNE)
{
// If NAT entry is found perform NAT processing
pIpHeader->ip_src.S_un.S_addr = htonl(pTcpNE->m_IpNAT.S_un.S_addr);
pTcpHeader->th_sport = htons(pTcpNE->m_usNATPort);
// Recalculate checksums
RecalculateTCPChecksum (&PacketBuffer);
RecalculateIPChecksum(pIpHeader);
}
}
// Incoming TCP packets processing
if ((hAdapters[dwIndex]->m_NATState == PROVIDER)&&
(PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_RECEIVE))
{
// Map connection to the NAT entry if the one exists
CPortNATEntry* pTcpNE = pDlg->m_TcpNatTable.Map(pTcpHeader->th_dport);
if (pTcpNE)
{
// NAT entry exists, make NAT processing
if (htonl(pTcpNE->m_IpDst.S_un.S_addr) == pIpHeader->ip_src.S_un.S_addr)
{
pIpHeader->ip_dst.S_un.S_addr = htonl(pTcpNE->m_IpSrc.S_un.S_addr);
pTcpHeader->th_dport = htons(pTcpNE->m_usSrcPort);
RecalculateTCPChecksum (&PacketBuffer);
RecalculateIPChecksum(pIpHeader);
}
}
}
}
// UDP packets processing
if (pIpHeader->ip_p == IPPROTO_UDP)
{
// This is UDP packet, get UDP header pointer
pUdpHeader = (udphdr*)(((PUCHAR)pIpHeader) + sizeof(DWORD)*pIpHeader->ip_hl);
// DNS hook
// If we receive DNS packet on the NAT client adapter then we redirect it
// to this system configured DNS server
if ((hAdapters[dwIndex]->m_NATState == CLIENT)&&
(PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_RECEIVE))
{
if (ntohs(pUdpHeader->th_dport) == 53/*DNS port*/)
{
// Save the DNS IP used by the NAT client system
hAdapters[dwIndex]->m_LocalDNS.S_un.S_addr = ntohl(pIpHeader->ip_dst.S_un.S_addr);
pIpHeader->ip_dst.S_un.S_addr = pDlg->m_DNSIp.S_un.S_addr;
RecalculateIPChecksum(pIpHeader);
}
}
// DNS reply came, substitute source IP back to the original DNS address
if ((hAdapters[dwIndex]->m_NATState == CLIENT)&&
(PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_SEND))
{
if (ntohs(pUdpHeader->th_sport) == 53/*DNS port*/)
{
pIpHeader->ip_src.S_un.S_addr = htonl(hAdapters[dwIndex]->m_LocalDNS.S_un.S_addr);
RecalculateIPChecksum(pIpHeader);
}
}
// Outgoing UDP NAT processing
if ((hAdapters[dwIndex]->m_NATState == PROVIDER)&&
(PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_SEND))
{
CPortNATEntry* pUdpNE = NULL;
// Try to find existing entry
pUdpNE = pDlg->m_UdpNatTable.Find(pIpHeader->ip_src, pUdpHeader->th_sport, pIpHeader->ip_dst, pUdpHeader->th_dport);
// If not found -> allocate a new one
if (!pUdpNE)
{
pUdpNE = pDlg->m_UdpNatTable.Allocate(pIpHeader->ip_src, pUdpHeader->th_sport, pIpHeader->ip_dst, pUdpHeader->th_dport);
if(pUdpNE)
{
pUdpNE->m_IpNAT = hAdapters[dwIndex]->m_NATIp;
}
}
// NAT processing
if (pUdpNE)
{
pIpHeader->ip_src.S_un.S_addr = htonl(pUdpNE->m_IpNAT.S_un.S_addr);
pUdpHeader->th_sport = htons(pUdpNE->m_usNATPort);
RecalculateUDPChecksum (&PacketBuffer);
RecalculateIPChecksum(pIpHeader);
}
}
// Incoming UDP packets processing
if ((hAdapters[dwIndex]->m_NATState == PROVIDER)&&
(PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_RECEIVE))
{
CPortNATEntry* pUdpNE = pDlg->m_UdpNatTable.Map(pUdpHeader->th_dport);
if (pUdpNE)
{
if (htonl(pUdpNE->m_IpDst.S_un.S_addr) == pIpHeader->ip_src.S_un.S_addr)
{
pIpHeader->ip_dst.S_un.S_addr = htonl(pUdpNE->m_IpSrc.S_un.S_addr);
pUdpHeader->th_dport = htons(pUdpNE->m_usSrcPort);
RecalculateUDPChecksum (&PacketBuffer);
RecalculateIPChecksum(pIpHeader);
}
}
}
}
}
// Reinject packet into the stack
if (PacketBuffer.m_dwDeviceFlags == PACKET_FLAG_ON_SEND)
{
// Place packet on the network interface
pDlg->m_NdisApi.SendPacketToAdapter(&Request);
}
else
{
// Indicate packet to MSTCP
pDlg->m_NdisApi.SendPacketToMstcp(&Request);
}
}
}while (dwIndex);
// Free all NAT entries
pDlg->m_TcpNatTable.RemoveAll();
pDlg->m_UdpNatTable.RemoveAll();
for (unsigned i = 1; i < dwActiveAdaptersCount; ++i)
{
Mode.dwFlags = 0;
Mode.hAdapterHandle = hAdapters->m_hAdapter;
// Set NULL event to release previously set event object
pDlg->m_NdisApi.SetPacketEvent(hAdapters->m_hAdapter, NULL);
// Close Event
if (hEvents)
CloseHandle ( hEvents );
// Set default adapter mode
pDlg->m_NdisApi.SetAdapterMode(&Mode);
// Empty adapter packets queue
pDlg->m_NdisApi.FlushAdapterPacketQueue (hAdapters->m_hAdapter);
}
_endthreadex( 0 );
return 0;
}Complete source code for the Internet Gateway is available to registered WinpkFilter customers.
