/* -----------------------------------------
     REMOTE promiscuous ethernet detector.
       Compiles and runs ok on RH5/GlibC
   -----------------------------------------
         (c) 1998 savage@apostols.org
   -----------------------------------------
   Scan your subnet, and detect promiscuous
   machinez. It really works, not a joke.
   ----------------------------------------- */
   
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <malloc.h>
#include <ctype.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/tcp.h>
#include <net/if.h>

/*#include <net/ethernet.h>*/
#include <linux/if_ether.h>

#include <sys/ioctl.h>
#include <fcntl.h>
#include <time.h>

#define MAX_PACK_LEN 2000
#define ETHER_HEADER_LEN 14
#define ARPREQUEST 1
#define ARPREPLY 2
#define perr(s) fprintf(stderr,s)

struct ether_hdr
  {
    u_char dst_mac[6], src_mac[6], pkt_type[2];
    u_short hw_type, pro_type;
    u_char hw_len, pro_len;
    u_short arp_op;
    u_char sender_eth[6];
    u_char sender_ip[4];
    u_char target_eth[6];
    u_char target_ip[4];
  };

union
  {
    u_char full_packet[MAX_PACK_LEN];
    struct ether_hdr ether_header;
  }
a;

#define full_packet a.full_packet
#define ether_header a.ether_header

char * 
inetaddr ( u_int32_t ip ) 
{
  struct in_addr in;
  in.s_addr = ip;
  return inet_ntoa(in);
}

char *
hwaddr (u_char * s)
{
  static char buf[30];
  sprintf (buf, "%02X:%02X:%02X:%02X:%02X:%02X", s[0], s[1], s[2], s[3], s[4], s[5]);
  return buf;
}

void
main (int argc, char **argv)
{
  int rec;
  int len, from_len, rsflags;
  struct ifreq if_data;
  struct sockaddr from;
  u_int8_t myMAC[6];
  u_int32_t myIP, myNETMASK, myBROADCAST, ip, dip;

  if (geteuid () != 0) {
      perr ("You must be root to run this program!\n");
      exit (0);
    }

  if (argc != 2)
    {
      perr ("Usage: scanpromisc eth0\n");
      exit (0);
    }

  if ((rec = socket (AF_INET, SOCK_PACKET, htons (ETH_P_ARP))) < 0)
    {
      perror("socket");
      exit (0);
    }

  printf ("----------------------------------------------------------\n");
  strcpy (if_data.ifr_name, argv[1]);
  if (ioctl (rec, SIOCGIFHWADDR, &if_data) < 0)
    perr ("can't get HW addres of my interface!\n");
  memcpy (myMAC, if_data.ifr_hwaddr.sa_data, 6);
  printf ("> My HW Addr: %s\n", hwaddr (myMAC));

  if (ioctl (rec, SIOCGIFADDR, &if_data) < 0)
    perr ("can't get IP addres of my interface!\n");
  memcpy ((void *) &ip, (void *) &if_data.ifr_addr.sa_data + 2, 4);
  myIP = ntohl (ip);
  printf ("> My IP Addr: %s\n", inetaddr(ip));

  if (ioctl (rec, SIOCGIFNETMASK, &if_data) < 0)
    perr ("can't get NETMASK addres of my interface!\n");
  memcpy ((void *) &ip, (void *) &if_data.ifr_netmask.sa_data + 2, 4);
  myNETMASK = ntohl (ip);
  printf ("> My NETMASK: %s\n", inetaddr(ip));

  if (ioctl (rec, SIOCGIFBRDADDR, &if_data) < 0)
    perr ("can't get BROADCAST addres of my interface!\n");
  memcpy ((void *) &ip, (void *) &if_data.ifr_broadaddr.sa_data + 2, 4);
  myBROADCAST = ntohl (ip);
  printf ("> My BROADCAST: %s\n", inetaddr(ip));

  printf ("----------------------------------------------------------\n");
  printf("> Waiting for an ARP pkt (don't ask why) ... "); fflush(stdout);
  len = recvfrom (rec, full_packet, MAX_PACK_LEN, 0, &from, &from_len);
  printf("Ok!\n");

  if ((rsflags = fcntl (rec, F_GETFL)) == -1)
    {
      perror ("fcntl F_GETFL");
      exit (1);
    }

  if (fcntl (rec, F_SETFL, rsflags | O_NONBLOCK) == -1)
    {
      perror ("fcntl F_SETFL");
      exit (1);
    }
  printf ("----------------------------------------------------------\n");
  printf ("> Scanning ....\n");
  for (dip = (myIP & myNETMASK) + 1; dip < myBROADCAST; dip++)
    {

      memcpy (ether_header.dst_mac, "666666", 6);
      memcpy (ether_header.target_eth, "\0\0\0\0\0\0", 6);
      ip = htonl (dip);
      memcpy (ether_header.target_ip, &ip, 4);

      memcpy (ether_header.src_mac, myMAC, 6);
      memcpy (ether_header.sender_eth, ether_header.src_mac, 6);
      ip = htonl (myIP);
      memcpy (ether_header.sender_ip, &ip, 4);

      ether_header.arp_op = htons (ARPREQUEST);
      ether_header.hw_type = 0x0100;
      ether_header.hw_len = 6;
      ether_header.pro_type = 8;
      ether_header.pro_len = 4;

      if( sendto (rec, full_packet, sizeof (struct ether_hdr), 0, &from, from_len) < 0)
          perror ("sendto");

      usleep (333);             

      len = recvfrom (rec, full_packet, MAX_PACK_LEN, 0, &from, &from_len);
      if (len <= ETHER_HEADER_LEN)
        continue;

      memcpy (&ip, ether_header.target_ip, 4);

      if (ntohs (ether_header.arp_op) == ARPREPLY
          && ntohl (ip) == myIP)
        {
          memcpy (&ip, ether_header.sender_ip, 4);
          printf ("*> Host %s, %s **** Promiscuous mode detected !!!\n",
                  inetaddr (ip),
                  hwaddr (ether_header.sender_eth));
        }

    }

  printf ("> End.\n");

  exit (0);
}