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revsicrevsic
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Create repository Packet-Injector
0 parents  commit bdc3c17

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lines changed

‎.gitignore

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*.o
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http_inject

‎Makefile

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CC = g++
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TARGET = http_inject
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OBJECTS = Protocol/Tcp.o Protocol/IPv4.o Protocol/Ethernet.o PacketInjector.o main.o
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all : $(TARGET)
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$(TARGET): $(OBJECTS)
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$(CC) -o $@ $^ -lpcap
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clean:
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rm -rf *.o Protocol/*.o http_inejct

‎PacketInjector.cpp

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#include "PacketInjector.h"
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PacketInjector::PacketInjector(pcap_t* p_handle) : handle(p_handle)
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{}
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int PacketInjector::run(const unsigned char* p_packet) {
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packet = p_packet;
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Ethernet eth = Ethernet(packet);
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if (eth.phdr->ether_type == ETHER_TYPE_IPv4) {
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IPv4 ip = IPv4(packet + ETHER_HEAD_LEN);
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if (ip.phdr->ip_protocol == IP_PRTCL_TCP) {
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int ip_len = ntohs(ip.phdr->ip_len);
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int ip_hdrlen = ip.phdr->ip_header_len << 2;
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TCP tcp = TCP(packet + ETHER_HEAD_LEN + ip_hdrlen, ip_len - ip_hdrlen);
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if (tcp.phdr->tcp_dport == TCP_PORT_HTTP) {
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if (tcp.pdat.length && !strncmp((char *)tcp.pdat.data, "GET", 3)) {
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char *tmp = strchr((char *)tcp.pdat.data, '\n');
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if (tmp) *tmp = '\0';
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std::cout << "[*] blocked : " << tcp.pdat.data << std::endl;
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int result = sendBackwardFin(eth, ip, tcp);
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if (result == -1) {
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std::cout << "[*] err : " << pcap_geterr(handle) << std::endl;
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return -1;
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}
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}
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}
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}
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}
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}
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int PacketInjector::sendForwardFin(IPv4& ip, TCP& tcp) {
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int tcp_hdrlen = tcp.phdr->tcp_header_len << 2;
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tcp.phdr->tcp_flags |= 1;
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tcp.phdr->tcp_seq_num = htonl(ntohl(tcp.phdr->tcp_seq_num) + tcp.pdat.length);
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int ip_hdrlen = ip.phdr->ip_header_len << 2;
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int ip_len = ip_hdrlen + tcp_hdrlen + strlen(BLOCK_MSG);
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ip.phdr->ip_len = htons(ip_len);
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strcpy((char *)tcp.pdat.data, BLOCK_MSG);
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tcp.pdat.length = strlen(BLOCK_MSG);
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ip.makeChecksum();
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tcp.makeChecksum(ip);
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int total_len = ETHER_HEAD_LEN + ip_len;
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int result = pcap_sendpacket(handle, packet, total_len);
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return result;
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}
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int PacketInjector::sendBackwardFin(Ethernet& eth, IPv4& ip, TCP& tcp) {
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for (int i = 0; i < ETHER_ADDR_LEN; ++i) {
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u_int8_t etmp = eth.phdr->ether_dhost[i];
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eth.phdr->ether_dhost[i] = eth.phdr->ether_shost[i];
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eth.phdr->ether_shost[i] = etmp;
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}
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struct in_addr itmp = ip.phdr->ip_dst;
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ip.phdr->ip_dst = ip.phdr->ip_src;
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ip.phdr->ip_src = itmp;
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u_int16_t ptmp = tcp.phdr->tcp_dport;
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tcp.phdr->tcp_dport = tcp.phdr->tcp_sport;
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tcp.phdr->tcp_sport = ptmp;
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tcp.phdr->tcp_flags |= TCP_FLAG_FIN;
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u_int32_t atmp = tcp.phdr->tcp_ack_num;
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tcp.phdr->tcp_ack_num = htonl(ntohl(tcp.phdr->tcp_seq_num) + tcp.pdat.length);
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tcp.phdr->tcp_seq_num = atmp;
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int tcp_hdrlen = tcp.phdr->tcp_header_len << 2;
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int ip_hdrlen = ip.phdr->ip_header_len << 2;
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int ip_len = ip_hdrlen + tcp_hdrlen + strlen(BLOCK_MSG);
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ip.phdr->ip_len = htons(ip_len);
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strcpy((char *)tcp.pdat.data, BLOCK_MSG);
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tcp.pdat.length = strlen(BLOCK_MSG);
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ip.makeChecksum();
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tcp.makeChecksum(ip);
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int total_len = ETHER_HEAD_LEN + ip_len;
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int result = pcap_sendpacket(handle, packet, total_len);
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return result;
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}

‎PacketInjector.h

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#ifndef PACKET_INJECTOR_H
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#define PACKET_INJECTOR_H
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#include <iostream>
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#include <string.h>
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#include <pcap.h>
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#include "Protocol/Ethernet.h"
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#include "Protocol/IPv4.h"
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#include "Protocol/Tcp.h"
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#define BLOCK_MSG "HTTP/1.1 302 Found\nLocation: https://en.wikipedia.org/wiki/HTTP_302\n"
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#define TCP_FLAG_FIN 1
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class PacketInjector {
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private:
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pcap_t* handle;
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const unsigned char* packet;
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public:
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PacketInjector(pcap_t* p_handle);
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int run(const unsigned char* p_packet);
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int sendForwardFin(IPv4& ip, TCP& tcp);
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int sendBackwardFin(Ethernet& eth, IPv4& ip, TCP& tcp);
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};
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#endif

‎Protocol/Ethernet.cpp

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#include "Ethernet.h"
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Ethernet::Ethernet(const u_char* packet) {
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phdr = (Ethernet_Header *)packet;
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}

‎Protocol/Ethernet.h

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#ifndef ETHERNET_H
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#define ETHERNET_H
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#include <arpa/inet.h>
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#define ETHER_ADDR_LEN 6
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#define ETHER_HEAD_LEN 14
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#define ETHER_TYPE_IPv4 htons(0x0800)
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class Ethernet {
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private:
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struct Ethernet_Header {
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u_int8_t ether_dhost[ETHER_ADDR_LEN];
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u_int8_t ether_shost[ETHER_ADDR_LEN];
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u_int16_t ether_type;
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};
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public:
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Ethernet_Header* phdr;
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Ethernet(const u_char* packet);
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};
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#endif

‎Protocol/IPv4.cpp

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#include "IPv4.h"
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IPv4::IPv4(const u_char* packet) {
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phdr = (IPv4_Header *)packet;
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}
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void IPv4::makeChecksum() {
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int chksum = 0;
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unsigned short *shorter = (unsigned short *)phdr;
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phdr->ip_checksum = 0;
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int len = phdr->ip_header_len << 1;
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for (int i = 0; i < len; ++i) {
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chksum += shorter[i];
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}
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chksum = (chksum >> 16) + (chksum & 0xFFFF);
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chksum += (chksum >> 16);
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chksum ^= 0xFFFF;
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phdr->ip_checksum = chksum;
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}

‎Protocol/IPv4.h

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#ifndef IPV4_H
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#define IPV4_H
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#include <sys/types.h>
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#include <arpa/inet.h>
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#define IP_PRTCL_TCP 6
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class IPv4 {
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private:
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struct IPv4_Header {
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u_int8_t ip_header_len:4;
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u_int8_t ip_version:4;
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u_int8_t ip_type;
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u_int16_t ip_len;
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u_int16_t ip_id;
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u_int16_t ip_offset;
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u_int8_t ip_ttl;
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u_int8_t ip_protocol;
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u_int16_t ip_checksum;
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struct in_addr ip_src, ip_dst;
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};
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public:
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IPv4_Header* phdr;
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IPv4(const u_char* packet);
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void makeChecksum();
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};
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#endif

‎Protocol/Tcp.cpp

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#include "Tcp.h"
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#include <stdio.h>
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TCP::TCP(const u_char *packet, int seg_len) {
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phdr = (TCP_Header *)packet;
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int tcp_hdrlen = phdr->tcp_header_len << 2;
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pdat.length = seg_len - tcp_hdrlen;
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pdat.data = packet + tcp_hdrlen;
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}
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void TCP::makeChecksum(IPv4& ip) {
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int i, chksum = 0;
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int dlen = phdr->tcp_header_len << 1;
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unsigned short *shorter = (unsigned short *)phdr;
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phdr->tcp_checksum = 0;
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for (i = 0; i < dlen; ++i) {
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chksum += shorter[i];
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}
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dlen = pdat.length >> 1;
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shorter = (unsigned short *)pdat.data;
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for (i = 0; i < dlen; ++i) {
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chksum += shorter[i];
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}
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if (pdat.length & 1) {
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chksum += shorter[i] & 0x00ff;
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}
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shorter = (unsigned short *)&ip.phdr->ip_src;
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chksum += shorter[0] + shorter[1];
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shorter = (unsigned short *)&ip.phdr->ip_dst;
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chksum += shorter[0] + shorter[1];
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chksum += htons(6);
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chksum += htons((phdr->tcp_header_len << 2) + pdat.length);
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chksum = (chksum >> 16) + (chksum & 0xFFFF);
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chksum += (chksum >> 16);
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chksum ^= 0xFFFF;
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phdr->tcp_checksum = chksum;
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}

‎Protocol/Tcp.h

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#ifndef TCP_H
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#define TCP_H
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#include <arpa/inet.h>
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#include <string.h>
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#include "IPv4.h"
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#define TCP_PORT_HTTP htons(80)
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class TCP {
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private:
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struct TCP_Header {
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u_int16_t tcp_sport, tcp_dport;
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u_int32_t tcp_seq_num;
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u_int32_t tcp_ack_num;
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u_int8_t tcp_reserved:4;
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u_int8_t tcp_header_len:4;
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u_int8_t tcp_flags;
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u_int16_t tcp_window;
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u_int16_t tcp_checksum;
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u_int16_t tcp_urgent;
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};
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struct TCP_Data {
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u_int32_t length;
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const u_int8_t *data;
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};
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public:
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TCP_Header *phdr;
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TCP_Data pdat;
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TCP(const u_char *packet, int seg_len);
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void makeChecksum(IPv4& ip);
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};
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#endif

‎README.md

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#Packet-Injection
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detect HTTP GET packet and inject packets

‎main.cpp

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#include <iostream>
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#include <pcap.h>
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#include "PacketInjector.h"
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int main (int argc, char** argv) {
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char errbuf[PCAP_ERRBUF_SIZE];
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char *dev = pcap_lookupdev(errbuf);
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if (dev == NULL) {
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std::cout << "[*] Couldn't find default device : " << errbuf << std::endl;
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return -1;
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}
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pcap_t *handle = pcap_open_live(dev, BUFSIZ, 1, 0, errbuf);
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if (handle == NULL) {
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std::cout << "[*] Couldn't open device : " << errbuf << std::endl;
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return -1;
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}
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struct pcap_pkthdr *header;
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const unsigned char *packet;
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PacketInjector pi = PacketInjector(handle);
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while (1) {
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int ret = pcap_next_ex(handle, &header, &packet);
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if (ret == 0) continue;
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else if (ret < 0) {
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std::cout << "[*] Couldn't receive packets." << std::endl;
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return -1;
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}
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pi.run(packet);
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}
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return 0;
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}

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