rawpacket.h

In this article, I will explain how to create UDP packets and then send them to a remote server thro

//Copyright Emmanuel Herrera 2008
#include "Includes.h"

class RawPacket
{
public:
	unsigned char* FinalPacket;
	void CreatePacket(unsigned char* SourceMAC,
					  unsigned char* DestinationMAC,
					  unsigned int   SourceIP,
					  unsigned int   DestinationIP,
					  unsigned short SourcePort,
					  unsigned short DestinationPort,
					  unsigned char* UserData,
					  unsigned int   DataLen);
	unsigned int UserDataLen;

	void SendPacket(pcap_if_t* Device);
private:
	unsigned short CalculateUDPChecksum(unsigned char* UserData,int UserDataLen,UINT SourceIP,UINT DestIP,USHORT SourcePort, USHORT DestinationPort, UCHAR Protocol);
	unsigned short CalculateIPChecksum(UINT TotalLen,UINT ID,UINT SourceIP,UINT DestIP);
};
void RawPacket::CreatePacket
					 (unsigned char* SourceMAC,
					  unsigned char* DestinationMAC,
					  unsigned int   SourceIP,
					  unsigned int   DestIP,
					  unsigned short SourcePort,
					  unsigned short DestinationPort,
					  unsigned char* UserData,
					  unsigned int   UserDataLen)
{
	RawPacket::UserDataLen = UserDataLen;
	FinalPacket = new unsigned char [UserDataLen + 42]; // Reserve enough memory for the length of the data plus 42 bytes of headers 
	USHORT TotalLen = UserDataLen + 20 + 8; // IP Header uses length of data plus length of ip header (usually 20 bytes) plus lenght of udp header (usually 8)
	//Beginning of Ethernet II Header
	memcpy((void*)FinalPacket,(void*)DestinationMAC,6);
	memcpy((void*)(FinalPacket+6),(void*)SourceMAC,6);
	USHORT TmpType = 8;
	memcpy((void*)(FinalPacket+12),(void*)&TmpType,2); //The type of protocol used. (USHORT) Type 0x08 is UDP. You can change this for other protocols (e.g. TCP)
	// Beginning of IP Header
	memcpy((void*)(FinalPacket+14),(void*)"\x45",1); //The Version (4) in the first 3 bits  and the header length on the last 5. (Im not sure, if someone could correct me plz do)
													 //If you wanna do any IPv6 stuff, you will need to change this. but i still don't know how to do ipv6 myself =s 
	memcpy((void*)(FinalPacket+15),(void*)"\x00",1); //Differntiated services field. Usually 0 
	TmpType = htons(TotalLen);
	memcpy((void*)(FinalPacket+16),(void*)&TmpType,2);
	TmpType = htons(0x1337);
	memcpy((void*)(FinalPacket+18),(void*)&TmpType,2);// Identification. Usually not needed to be anything specific, esp in udp. 2 bytes (Here it is 0x1337
	memcpy((void*)(FinalPacket+20),(void*)"\x00",1); // Flags. These are not usually used in UDP either, more used in TCP for fragmentation and syn acks i think 
	memcpy((void*)(FinalPacket+21),(void*)"\x00",1); // Offset
	memcpy((void*)(FinalPacket+22),(void*)"\x80",1); // Time to live. Determines the amount of time the packet can spend trying to get to the other computer. (I see 128 used often for this)
	memcpy((void*)(FinalPacket+23),(void*)"\x11",1);// Protocol. UDP is 0x11 (17) TCP is 6 ICMP is 1 etc
	memcpy((void*)(FinalPacket+24),(void*)"\x00\x00",2); //checksum 
	memcpy((void*)(FinalPacket+26),(void*)&SourceIP,4); //inet_addr does htonl() for us
	memcpy((void*)(FinalPacket+30),(void*)&DestIP,4);
	//Beginning of UDP Header
	TmpType = htons(SourcePort);
	memcpy((void*)(FinalPacket+34),(void*)&TmpType,2);
	TmpType = htons(DestinationPort);
	memcpy((void*)(FinalPacket+36),(void*)&TmpType,2);
	USHORT UDPTotalLen = htons(UserDataLen + 8); // UDP Length does not include length of IP header
	memcpy((void*)(FinalPacket+38),(void*)&UDPTotalLen,2);
	//memcpy((void*)(FinalPacket+40),(void*)&TmpType,2); //checksum
	memcpy((void*)(FinalPacket+42),(void*)UserData,UserDataLen);

	unsigned short UDPChecksum = CalculateUDPChecksum(UserData,UserDataLen,SourceIP,DestIP,htons(SourcePort),htons(DestinationPort),0x11);
	memcpy((void*)(FinalPacket+40),(void*)&UDPChecksum,2);

	unsigned short IPChecksum = htons(CalculateIPChecksum(TotalLen,0x1337,SourceIP,DestIP));
	memcpy((void*)(FinalPacket+24),(void*)&IPChecksum,2);
	
	return;
	
}
unsigned short RawPacket::CalculateIPChecksum(UINT TotalLen,UINT ID,UINT SourceIP,UINT DestIP)
{
	unsigned short CheckSum = 0;
	for(int i = 14;i<34;i+=2)
	{
		unsigned short Tmp = BytesTo16(FinalPacket[i],FinalPacket[i+1]);
		unsigned short Difference = 65535 - CheckSum;
		CheckSum += Tmp;
		if(Tmp > Difference){CheckSum += 1;}
	}
	CheckSum = ~CheckSum;
	return CheckSum;
}
unsigned short RawPacket::CalculateUDPChecksum(unsigned char* UserData,int UserDataLen,UINT SourceIP,UINT DestIP,USHORT SourcePort, USHORT DestinationPort, UCHAR Protocol)
{
	unsigned short CheckSum = 0;
	unsigned short PseudoLength = UserDataLen + 8 + 9; //Length of PseudoHeader = Data Length + 8 bytes UDP header (2Bytes Length,2 Bytes Dst Port, 2 Bytes Src Port, 2 Bytes Checksum)
														//+ Two 4 byte IP's + 1 byte protocol
	PseudoLength += PseudoLength % 2; //If bytes are not an even number, add an extra.
	unsigned short Length = UserDataLen + 8; // This is just UDP + Data length. needed for actual data in udp header

	unsigned char* PseudoHeader = new unsigned char [PseudoLength]; 
	for(int i = 0;i < PseudoLength;i++){PseudoHeader[i] = 0x00;}

	PseudoHeader[0] = 0x11;

	memcpy((void*)(PseudoHeader+1),(void*)(FinalPacket+26),8); // Source and Dest IP

	Length = htons(Length);
	memcpy((void*)(PseudoHeader+9),(void*)&Length,2);
	memcpy((void*)(PseudoHeader+11),(void*)&Length,2); 

	memcpy((void*)(PseudoHeader+13),(void*)(FinalPacket+34),2);
	memcpy((void*)(PseudoHeader+15),(void*)(FinalPacket+36),2);

	memcpy((void*)(PseudoHeader+17),(void*)UserData,UserDataLen);


	for(int i = 0;i < PseudoLength;i+=2)
    {
        unsigned short Tmp = BytesTo16(PseudoHeader[i],PseudoHeader[i+1]);
        unsigned short Difference = 65535 - CheckSum;
        CheckSum += Tmp;
        if(Tmp > Difference){CheckSum += 1;}
    }
	CheckSum = ~CheckSum; //One's complement
	return CheckSum;
}
void RawPacket::SendPacket(pcap_if_t* Device)
{
	char Error[256];
	pcap_t* t;
	t = pcap_open(Device->name,65535,PCAP_OPENFLAG_DATATX_UDP,1,NULL,Error);//FP for send
	pcap_sendpacket(t,FinalPacket,UserDataLen + 42);
	pcap_close(t);


}