tap.c

linux或unix下回话劫持工具

/*
 *
 *	This is free software. You can redistribute it and/or modify under
 *	the terms of the GNU General Public License version 2.
 *
 * 	Copyright (C) 1998 by kra
 *
 */
#ifndef _WITH_LINUX_KERNEL_HDR
#define _WITH_LINUX_KERNEL_HDR
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <netdb.h>
#include <sys/ioctl.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <linux/if.h>

extern int socket(int domain, int type, int protocol);
extern unsigned short int htons(unsigned short int hostshort);

#define HL_MODE_NR 0
extern char *host_lookup(unsigned int in, int use_mode);
extern int verbose;

unsigned char my_eth_mac[ETH_ALEN];
unsigned int my_eth_ip;

int tap(char *device, int promisc_mode)
{
	
	int fd;				
	struct ifreq ifr;   /* Link-layer interface request structure */
        	            /* Ethernet code for IP 0x0800==ETH_P_IP */
	/*
	 * here ETH_P_IP  - je to jedno, stejne pres nej poslu ARP packet
	 * 		    nevim ale jestli ho prijmu?
	 */
	/*
	 * look at tcpdump
	 */
	if ((fd = socket(AF_INET, SOCK_PACKET, 
			/*htons(ETH_P_IP)*/ htons(ETH_P_ALL))) < 0) {
	        if (verbose)
			perror("(tap) SOCK_PACKET allocation problems [fatal]");
	        exit(1);					           
	}
	strcpy(ifr.ifr_name, device);				
	if ((ioctl(fd, SIOCGIFFLAGS, &ifr)) < 0) {    /* Get the device info */
	        if (verbose)
			perror("(tap) Can't get device flags [fatal]");
	        close(fd);
      		exit(1);
	}
	if (!promisc_mode)
		ifr.ifr_flags &= ~IFF_PROMISC;    /* Unset promiscuous mode */
	else
		ifr.ifr_flags |= IFF_PROMISC;        /* Set promiscuous mode */
#if 0
	if (ifr.ifr_flags & IFF_SOFTHEADERS) {
		printf("had softheaders\n");
		ifr.ifr_flags ^= IFF_SOFTHEADERS;
	}
#endif
	if ((ioctl(fd, SIOCSIFFLAGS, &ifr)) < 0) {    /* Set flags */
        	if (verbose)
			perror("(tap) Can't set/unset promiscuous mode [fatal]");
		close(fd);
		exit(1);
	}
	if(!promisc_mode){
        	close(fd);
	        return 0;
	} else {
		if (ioctl(fd, SIOCGIFADDR, &ifr) < 0) {
			if (verbose)
				perror("(tap) Can't get interface IP address");
			tap(device, 0);
			exit(1);
		}
		my_eth_ip = *(unsigned int *) (ifr.ifr_addr.sa_data + 2);
		if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
			if (verbose)
				perror("(tap) Can't get interface HW address");
			tap(device, 0);
			exit(1);
		}
		memcpy(my_eth_mac, ifr.ifr_hwaddr.sa_data, ETH_ALEN);
		if (verbose)
			printf("listeining on %s %s %s\n", device,
			       host_lookup(my_eth_ip, HL_MODE_NR),
			       my_eth_mac);
		return fd;
	}
}