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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.
Повторюсь:
Надо для 6.0 и только!DDKBUILD старый продукт, начинался как раз под VC6, сам им не пользуюсь, но думаю и там он еще работает. Если нет ищите старые версии…
P.S. А вежливости Вас в школе видимо недоучили 🙄
DDKBUILD от http://www.hollistech.com/
We are your customer and have baught Individual User License only.
Since Individual license does not include any drivers customization it can be implemented for the extra fee only.
When we are trying to sniff using WinpkFilter, on the XP Bridge, we don’t see any packets. I mean we can’t sniff.
Please clarify. Are you trying to use listening mode or tunnel mode? Have you tried PassThru and PacketSniffer samples over the bridge or it was your own code? In general WinpkFilter intercepts all packets between XP bridge and TCP/IP stack, so if there any packets and driver is used correctly then you can’t miss them.
Yes, we require that feature. Can you please tell me how I can get that that?
This modification is available to WinpkFilter Source Code and Developer (as a custom build) licensees. If you our customer and own one of the licenses mentioned above then please e-mail support@ntkernel.com with your order details (license, order ID and approximate date of purchase) in order to get customized WinpkFilter build.
where i edit ?
If you have access to the source code then you should modify the proc.h in line 22
#define INT_BUF_POOL_SIZE 500
change to
#define INT_BUF_POOL_SIZE 1000 //or 1500
Thats right, when you are not using bridge TCP/IP is bound to your LAN adapters (and you can normally see them), but when using bridge – it is bound to the bridge network adapter (bridge itself is intermediate driver which binds like a protocol to LAN adapters and has network interface on top of it, in this case TCP/IP is bound to this interface and since WinpkFilter driver puts itself between TCP/IP and its adapters then you can see only a bridge).
If you require filtering over raw LAN adapters even if XP bridge is used then it is also possible (in general it is just a simple driver modification and we had a customer who requested this feature before).
а в “железных” маршрутизаторах типа циски используется такой же алгоритм?
Что там в сиске, не знает никто кроме разработчиков сиски.
есть ли оценки его эффективности?
Тут есть какая-то теория:
http://www.lan2net.ru/shaper.shtml
