heaeat / send_arp

Repository for arp_send homework (feat. gilgil Mentor)

arp_send

Repository for arp_send homework (feat. gilgil Mentor)

How to build

make

How to run

sudo ./send_arp <dev_name> <target_ip> <gateway_ip>

Test

Test Environment

ubuntu 16.04 (on docker)

• container - sender

  ip address : 172.18.0.2

  MAC address : 02:42:ac:12:00:02

• container - target

  ip address : 172.18.0.3

  MAC address : 02:42:ac:12:00:03

• Gateway

  ip address : 172.18.0.1

  MAC address : 02:00:12:12:00:02

Result

Gateway mac address has been tampered with.

Reference

I studied this..!

How ARP packet works?

1. 출발지에서 ARP table에 목적지 MAC주소가 있는지 확인
2. ARP table에 없으면 ARP request 브로드캐스트(브로드캐스트! 만세)
3. ARP request 패킷을 받은 쪽에서 자신의 MAC주소를 ARP reply 패킷으로 알려줌
4. ARP reply패킷을 받은 출발지는 ARP 테이블에 해당 정보를 기록 (중간중간 게이트웨이가 리커버리 하기는 함)

Link

• https://www.winpcap.org/docs/docs_40_2/html/group__wpcap__tut8.html
• https://linux.die.net/man/3/pcap_sendpacket

ARP header structure

Hardware type : 2 byte
Protocol type : 2 byte
H/W address length : 1 byte
protocol address length : 1 byte
Operation : 2 byte
Source MAC : 6 byte
Source IP : 4 byte
Destination MAC : 6 byte
Destination IP : 4 byte