fuzz_dhcps6.c

/*
 * Contributed by:
 *  Brandon Hutcheson, Graeme Neilson and Ryan Ko
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <time.h>
#include <pcap.h>
#include <netinet/in.h>
#include <sys/select.h>
#include "thc-ipv6.h"

#define COUNT_FLAG     11
#define COUNT_BYTE      4
#define COUNT_WORD     16
#define COUNT_XOR       2
#define COUNT_EXTEND  256
#define COUNT_DWORD   256

#define NEVER 2000000000
#define TEST_MAX (NEVER - 1)

#define DO_SOL 1
#define DO_REQ 2
#define DO_CON 3
#define DO_REN 4
#define DO_REB 5
#define DO_DEC 6
#define DO_REL 7
#define DO_INF 8

#define STATELESS 0
#define STATEFULL 1

/*
 * Fuzzing data types:
 *  F = flags = 1 byte = 8 bits | flags | 8 ; 256
 *  B = byte = 1 byte | 0 1 254 255 xor XOR | 6 ; 256
 *  X = byte = 1 byte | all values from 0 to 255
 *  W = word = 2 bytes | 0,1,254,255^2 xor XOR | 18 ; 65536
 *  D = double word = 4 bytes | {0,1,254,255}^4 xor XOR | 258 ; 4294967295
 *  . = byte = ignore, jump over
 *
 */
char fuzztype_ether[] = ".............."; //14 byte header
char fuzztype_ip6[] = "........................................"; //40 byte header
char fuzztype_udp[] = "........"; //8 byte header
char fuzztype_dhcp6[] = "X..."; //4 byte header (fuzz message type)
char fuzztype_dhcp6no[] = "...."; //4 byte header (don't fuzz message type)

//OPTION HEADERS
char fuzztype_elapsed_time[] = "WWW"; //6 byte header
char fuzztype_client_identifier[] = "WWWWDWWW"; //18 byte header
char fuzztype_server_identifier[] = "WWWWDWWW"; //18 byte header
char fuzztype_IA_NA[] = "WWDDD"; //16 byte header
char fuzztype_IA_Address[] = "WWXX..............DD";
char fuzztype_FQDN[] = "WWF"; //5 byte header + length of domain string to be added in programatically
char fuzztype_option_request[] = "WWW"; //6 byte header (add extra W for each additional option)

// //Matched solicit from RF manual
// char fuzztype_solicit[] = ".......FFFFFFFFF................BBBXXXX";
// //Still have to add in other types.
// char fuzztype_tran_id[] = "XF..WXBXX..............XX..............";
// char fuzztype_options[] = "........................................";


unsigned char flags[] = { 0, 1, 2, 4, 8, 16, 32, 64, 128, 254, 255 };   // 11
unsigned char bytes[] = { 0, 1, 254, 255 };     // 4
unsigned short int words[] = { 0x0000, 0x0001, 0x00fe, 0x00ff, 0x0100, 0x0101,
  0x01fe, 0x01ff, 0xfe00, 0xfe01, 0xfefe, 0xfeff, 0xff00, 0xff01, 0xfffe,
  0xffff
};                              // 16
unsigned int xors[] = { 0, 0xffffffff };        // 2
unsigned char extends[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
  34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52,
  53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,
  72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90,
  91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107,
  108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122,
  123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,
  138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152,
  153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167,
  168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182,
  183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197,
  198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212,
  213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227,
  228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242,
  243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255
};                              // 256
unsigned int dwords[] = { 0x00000000, 0x00000001, 0x000000fe, 0x000000ff,
  0x00000100, 0x00000101, 0x000001fe, 0x000001ff,
  0x0000fe00, 0x0000fe01, 0x0000fefe, 0x0000feff,
  0x0000ff00, 0x0000ff01, 0x0000fffe, 0x0000ffff,
  0x00010000, 0x00010001, 0x000100fe, 0x000100ff,
  0x00010100, 0x00010101, 0x000101fe, 0x000101ff,
  0x0001fe00, 0x0001fe01, 0x0001fefe, 0x0001feff,
  0x0001ff00, 0x0001ff01, 0x0001fffe, 0x0001ffff,
  0x00fe0000, 0x00fe0001, 0x00fe00fe, 0x00fe00ff,
  0x00fe0100, 0x00fe0101, 0x00fe01fe, 0x00fe01ff,
  0x00fefe00, 0x00fefe01, 0x00fefefe, 0x00fefeff,
  0x00feff00, 0x00feff01, 0x00fefffe, 0x00feffff,
  0x00ff0000, 0x00ff0001, 0x00ff00fe, 0x00ff00ff,
  0x00ff0100, 0x00ff0101, 0x00ff01fe, 0x00ff01ff,
  0x00fffe00, 0x00fffe01, 0x00fffefe, 0x00fffeff,
  0x00ffff00, 0x00ffff01, 0x00fffffe, 0x00ffffff,
  0x01000000, 0x01000001, 0x010000fe, 0x010000ff,
  0x01000100, 0x01000101, 0x010001fe, 0x010001ff,
  0x0100fe00, 0x0100fe01, 0x0100fefe, 0x0100feff,
  0x0100ff00, 0x0100ff01, 0x0100fffe, 0x0100ffff,
  0x01010000, 0x01010001, 0x010100fe, 0x010100ff,
  0x01010100, 0x01010101, 0x010101fe, 0x010101ff,
  0x0101fe00, 0x0101fe01, 0x0101fefe, 0x0101feff,
  0x0101ff00, 0x0101ff01, 0x0101fffe, 0x0101ffff,
  0x01fe0000, 0x01fe0001, 0x01fe00fe, 0x01fe00ff,
  0x01fe0100, 0x01fe0101, 0x01fe01fe, 0x01fe01ff,
  0x01fefe00, 0x01fefe01, 0x01fefefe, 0x01fefeff,
  0x01feff00, 0x01feff01, 0x01fefffe, 0x01feffff,
  0x01ff0000, 0x01ff0001, 0x01ff00fe, 0x01ff00ff,
  0x01ff0100, 0x01ff0101, 0x01ff01fe, 0x01ff01ff,
  0x01fffe00, 0x01fffe01, 0x01fffefe, 0x01fffeff,
  0x01ffff00, 0x01ffff01, 0x01fffffe, 0x01ffffff,
  0xfe000000, 0xfe000001, 0xfe0000fe, 0xfe0000ff,
  0xfe000100, 0xfe000101, 0xfe0001fe, 0xfe0001ff,
  0xfe00fe00, 0xfe00fe01, 0xfe00fefe, 0xfe00feff,
  0xfe00ff00, 0xfe00ff01, 0xfe00fffe, 0xfe00ffff,
  0xfe010000, 0xfe010001, 0xfe0100fe, 0xfe0100ff,
  0xfe010100, 0xfe010101, 0xfe0101fe, 0xfe0101ff,
  0xfe01fe00, 0xfe01fe01, 0xfe01fefe, 0xfe01feff,
  0xfe01ff00, 0xfe01ff01, 0xfe01fffe, 0xfe01ffff,
  0xfefe0000, 0xfefe0001, 0xfefe00fe, 0xfefe00ff,
  0xfefe0100, 0xfefe0101, 0xfefe01fe, 0xfefe01ff,
  0xfefefe00, 0xfefefe01, 0xfefefefe, 0xfefefeff,
  0xfefeff00, 0xfefeff01, 0xfefefffe, 0xfefeffff,
  0xfeff0000, 0xfeff0001, 0xfeff00fe, 0xfeff00ff,
  0xfeff0100, 0xfeff0101, 0xfeff01fe, 0xfeff01ff,
  0xfefffe00, 0xfefffe01, 0xfefffefe, 0xfefffeff,
  0xfeffff00, 0xfeffff01, 0xfefffffe, 0xfeffffff,
  0xff000000, 0xff000001, 0xff0000fe, 0xff0000ff,
  0xff000100, 0xff000101, 0xff0001fe, 0xff0001ff,
  0xff00fe00, 0xff00fe01, 0xff00fefe, 0xff00feff,
  0xff00ff00, 0xff00ff01, 0xff00fffe, 0xff00ffff,
  0xff010000, 0xff010001, 0xff0100fe, 0xff0100ff,
  0xff010100, 0xff010101, 0xff0101fe, 0xff0101ff,
  0xff01fe00, 0xff01fe01, 0xff01fefe, 0xff01feff,
  0xff01ff00, 0xff01ff01, 0xff01fffe, 0xff01ffff,
  0xfffe0000, 0xfffe0001, 0xfffe00fe, 0xfffe00ff,
  0xfffe0100, 0xfffe0101, 0xfffe01fe, 0xfffe01ff,
  0xfffefe00, 0xfffefe01, 0xfffefefe, 0xfffefeff,
  0xfffeff00, 0xfffeff01, 0xfffefffe, 0xfffeffff,
  0xffff0000, 0xffff0001, 0xffff00fe, 0xffff00ff,
  0xffff0100, 0xffff0101, 0xffff01fe, 0xffff01ff,
  0xfffffe00, 0xfffffe01, 0xfffffefe, 0xfffffeff,
  0xffffff00, 0xffffff01, 0xfffffffe, 0xffffffff
};                              // 256
char solicit[] = { 0x01, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x02, 0x00, 0x00,
  0x00, 0x01, 0x00, 0x0e, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03,
  0x00, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00
};

int port = -1;

void help(char *prg) {
  printf("%s %s (c) 2014 by %s %s\n\n", prg, VERSION, "Brandon Hutcheson, Graeme Neilson and Ryan Ko", RESOURCE);
  printf("Syntax: %s [-t number | -T number] [-e number | -T number] [-p number] [-md] [-1|-2|-3|-4|-5|-6|-7|-8] interface [domain-name]\n\n", prg);
  printf("Fuzzes an DHCPv6 packet\n");
  printf("Options:\n");
  printf(" -1         fuzz DHCPv6 Solicit (default)\n");
  printf(" -2         fuzz DHCPv6 Request\n");
  printf(" -3         fuzz DHCPv6 Confirm\n");
  printf(" -4         fuzz DHCPv6 Renew\n"); 
  printf(" -5         fuzz DHCPv6 Rebind\n"); 
  printf(" -6         fuzz DHCPv6 Release\n"); 
  printf(" -7         fuzz DHCPv6 Decline\n"); 
  printf(" -8         fuzz DHCPv6 Information Request\n"); 
  printf(" -m         fuzz the message type as well\n");
  printf(" -t number  continue from test no. number\n");
  printf(" -e number  continue to test no. number\n");
  printf(" -T number  only performs test no. number\n");
  printf(" -n number  how many times to send each packet (default: 1)\n");
  printf(" -f         spoof mac\n");
  printf(" -F         spoof link address\n");
  printf(" -p number  perform an alive check every number of tests (default: none)\n");
  printf(" -d         Use -d to force DNS updates, you can specify a domain name on the commandline.\n");
  printf("You can only define one of -0 ... -4, defaults to -1.\n");
  printf("Returns -1 on error, 0 on tests done and targt alive or 1 on target crash.\n");
  exit(-1);
}

char dnsupdate1[] = { 0, 39, 0, 8, 1, 6, 122, 97, 97, 97, 97, 97 };
char dnsupdate2[] = { 0, 6, 0, 2, 0, 39 };
char dns_option_hdr[256];
int dns_option_hdr_len = 0;
char fuzzbuf[256];
char *interface = NULL, *dns_name = NULL, elapsed[6] = { 0, 8, 0, 2, 0, 0 };
int do_dns = 0, test_start = 0, test_end = TEST_MAX, ping = NEVER, no_send = 1, got_packet = 0;
pcap_t *p = NULL;
int do_type = DO_SOL, fuzz_msg_type = 0;
int timeout = 4;

void ignoreit(u_char *foo, const struct pcap_pkthdr *header, const unsigned char *data) {
  return;
}

int try_send_pkt(char *interface, char *pkt, int *pkt_len) {
  //Try send packet
  int retry_send = 1;
  time_t start_time = time(NULL);
  while(time(NULL) - start_time < timeout && retry_send) {
    if (thc_send_pkt(interface, pkt, pkt_len) < 0) 
      retry_send = 1;
    else
      retry_send = 0;
  }
  if (retry_send) {
    fprintf(stderr, "Timeout error: Unable to send check alive packet within timeout\n");
    exit(-1);
  }
  return 0;
}

int check_alive(pcap_t * p) {
  int ret = -2, len, pkt_len = 0, i;
  time_t t;
  char wdatabuf[1024];
  char *pkt = NULL;
  unsigned char *dst = thc_resolve6("ff02::1:2");
  unsigned char *mac6 = thc_get_own_mac(interface);

  len = sizeof(solicit);
  memcpy(wdatabuf, solicit, len);
   // start0: 1-3 rand, 18-21 rand, 22-27 mac, 32-35 rand
  for (i = 0; i < 3; i++) {
    wdatabuf[i + 1] = rand() % 256;
    wdatabuf[i + 18] = rand() % 256;
    wdatabuf[i + 32] = rand() % 256;
  }
  memcpy(wdatabuf + 22, mac6, 6);

  if ((pkt = thc_create_ipv6_extended(interface, PREFER_LINK, &pkt_len, NULL, dst, 1, 0, 0, 0, 0)) == NULL) {
    fprintf(stderr, "Error: Failed to create check allive ivp6 packet header\n");
    exit(-1);
  }

  if (thc_add_udp(pkt, &pkt_len, 546, 547, 0, wdatabuf, len) < 0) {
    fprintf(stderr, "Error: Failed to create check allive udp packet header\n");
    exit(-1);
  }

  if (thc_generate_pkt(interface, mac6, NULL, pkt, &pkt_len) < 0) {
    fprintf(stderr, "Error: Failed to create check allive packet header\n");
    exit(-1);
  }

  // debug = 1;

  //Empty packet capture queue
  while (thc_pcap_check(p, (char *) ignoreit, NULL) > 0);

  //Send initial solicit request
  try_send_pkt(interface, pkt, &pkt_len);

  //Check for response in loop and timeout if we don't get one
  t = time(NULL);
  while (ret < 0) {
    //Got reply packet; server alive!
    if (thc_pcap_check(p, (char *) ignoreit, NULL) > 0)
      ret = 1;

    //If we still haven't received a packet after 1 second resend the solicit
    if (time(NULL) > t + 1 && ret == -2) {
      if (thc_send_pkt(interface, pkt, &pkt_len) < 0) {  //Don't want to use try_send_pkt as it could take longer than timeout
        usleep(75);
        thc_send_pkt(interface, pkt, &pkt_len);          //Retry sending packet after short time if sending failed
      }
      ret = -1;
    }

    //Fail after 4 seconds
    if (time(NULL) > t + timeout && ret < 0)
      ret = 0;
  }
  if (ret == 0) {
    fprintf(stderr, "Timeout: Failed to receive dhcp solicitation replay in check alive function within %d seconds\n", timeout);
  }

  // debug = 0;

  thc_destroy_packet(pkt);

  return ret > 0 ? 1 : 0;
}

int fuzz_loop(char* pkt, int* pkt_len) {
  int do_fuzz = 1;
  int test_pos = 0, test_ptr = 0, test_cnt = 0, test_current = 0;
  int do_it;
  int i;
  unsigned short int *sip;
  unsigned int *intp;
  int fragment = 0, frag_offset = 0;
  unsigned char *pkt_bak;
  thc_ipv6_hdr *hdr = (thc_ipv6_hdr *) pkt;

  // backup of generated packet
  pkt_bak = malloc(hdr->pkt_len);
  memcpy(pkt_bak, hdr->pkt, hdr->pkt_len);

  printf("Fuzzing packet, starting at fuzz case %d, ending at fuzz case %d:\n", test_start, test_end);
  printf("fuzzbuf(%d): %s\n", strlen(fuzzbuf), fuzzbuf);
  while (do_fuzz) {
    if (test_cnt == 0)
      while (fuzzbuf[test_ptr] == '.') {
        test_ptr++;
        test_pos++;
      }

    if (fuzzbuf[test_ptr] == 0)
      do_fuzz = 0;

    test_cnt++;
    do_it = 1;


    switch (fuzzbuf[test_ptr]) {
    case 0:
      break;
    case 'X':
      if (test_cnt <= COUNT_EXTEND) {
        if (pkt_bak[test_pos] != extends[test_cnt - 1])
          hdr->pkt[test_pos] = extends[test_cnt - 1];
        else
          do_it = 0;
      } else {
        test_cnt = 0;
        test_ptr++;
        test_pos++;
      }
      break;
    case 'B':
      if (test_cnt <= COUNT_BYTE) {
        if (pkt_bak[test_pos] != bytes[test_cnt - 1])
          hdr->pkt[test_pos] = bytes[test_cnt - 1];
        else
          do_it = 0;
      } else {
        i = 0;
        while (i < COUNT_BYTE && do_it) {
          if (bytes[i] == pkt_bak[test_pos])
            do_it = 0;
          i++;
        }
        if (do_it)
          hdr->pkt[test_pos] = hdr->pkt[test_pos] ^ xors[test_cnt - COUNT_BYTE - 1];
      }
      if (test_cnt == COUNT_BYTE + COUNT_XOR) {
        test_cnt = 0;
        test_ptr++;
        test_pos++;
      }
      break;
    case 'F':
      if (test_cnt <= COUNT_FLAG) {
        if (pkt_bak[test_pos] != flags[test_cnt - 1])
          hdr->pkt[test_pos] = flags[test_cnt - 1];
        else
          do_it = 0;
      } else {
        i = 0;
        while (i < COUNT_FLAG && do_it) {
          if (bytes[i] == pkt_bak[test_pos])    // yes, bytes[] is the right one even for flags
            do_it = 0;
          i++;
        }
        if (do_it)
          hdr->pkt[test_pos] = hdr->pkt[test_pos] ^ xors[test_cnt - COUNT_BYTE - 1];
      }
      if (test_cnt == COUNT_FLAG + COUNT_XOR) {
        test_cnt = 0;
        test_ptr++;
        test_pos++;
      }
      break;
    case 'W':
      sip = (unsigned short int *) &pkt_bak[test_pos];
      if (test_cnt <= COUNT_WORD) {
        if (*sip != words[test_cnt - 1])
          memcpy((char *) &hdr->pkt[test_pos], (char *) &words[test_cnt - 1], 2);
        else
          do_it = 0;
      } 
      else {
        i = 0;
        while (i < COUNT_WORD && do_it) {
          if (words[i] == *sip)
            do_it = 0;
          i++;
        }
        if (do_it) {
          i = *sip ^ xors[test_cnt - COUNT_WORD - 1];
          sip = (unsigned short int *) &hdr->pkt[test_pos];
          *sip = i % 65536;
        }
      }
      if (test_cnt == COUNT_WORD + COUNT_XOR) {
        test_cnt = 0;
        test_ptr++;
        test_pos += 2;
      }
      break;
    case 'D':
      intp = (unsigned int *) &pkt_bak[test_pos];
      if (test_cnt <= COUNT_DWORD) {
        if (*intp != dwords[test_cnt - 1])
          memcpy((char *) &hdr->pkt[test_pos], (char *) &dwords[test_cnt - 1], 4);
        else
          do_it = 0;
      } else {
        i = 0;
        while (i < COUNT_DWORD && do_it) {
          if (dwords[i] == *intp)
            do_it = 0;
          i++;
        }
        if (do_it) {
          i = *intp ^ xors[test_cnt - COUNT_DWORD - 1];
          intp = (unsigned int *) &hdr->pkt[test_pos];
          *intp = (unsigned int) i;
//          *intp = (unsigned int) (i % 4294967295);
        }
      }
      if (test_cnt == COUNT_DWORD + COUNT_XOR) {
        test_cnt = 0;
        test_ptr++;
        test_pos += 4;
      }
      break;
    default:
      fprintf(stderr, "This character should not be in the fuzz string, shoot the programmer: %c(%d) position %d string %s\n", fuzzbuf[test_ptr], fuzzbuf[test_ptr], test_ptr,
              fuzzbuf);
      return -1;
      break;
    }

    if (do_it && do_fuzz) {
      if (test_current >= test_start && test_current <= test_end && do_fuzz) {
        printf("[%s] pos[%d]=%c -> %d | pkt[%d] | %d (%d=>%d)| \n", /*fuzzbuf*/"", test_ptr, fuzzbuf[test_ptr], test_cnt, test_pos, test_current, test_start, test_end);

        // Generate new transaction id
        int three_byte_test_current = test_current % 0x1000000;
        memcpy(hdr->pkt + 63, (char *) &three_byte_test_current, 3);

        // Regenerate UDP checksum 
        hdr->pkt[60] = 0;
        hdr->pkt[61] = 0;
        i = checksum_pseudo_header(hdr->original_src, hdr->final_dst, NXT_UDP, &hdr->pkt[54], hdr->pkt_len - 54);
        hdr->pkt[60] = i / 256;
        hdr->pkt[61] = i % 256;

        // send packets
        int k;
        for (k = 0; k < no_send; k++) {
          while(thc_send_pkt(interface, pkt, pkt_len) < 0)
            usleep(1);
        }
        // printf(".");
        usleep(250);

        // TODO: Server up check
        if ((test_current - test_start) % ping == 0 && test_current != 0 && test_start != test_current)
          if (check_alive(p) == 0) {
            i = ((((test_current - test_start) / ping) - 1) * ping) + test_start + 1;
            printf("\nResult: target %s crashed during fuzzing, offending test case no. could be %d to %d\n", thc_ipv62notation(hdr->final_dst), i < 0 ? 0 : i, test_current);
            exit(1);
          }
      }

      // reset to basic packet
      memcpy(hdr->pkt, pkt_bak, hdr->pkt_len);
      test_current++;
    }
  }
  return 0;
}

void construct_from_adv_and_fuzz(u_char *foo, const struct pcap_pkthdr *header, const unsigned char *data) {
  int len = header->caplen, pkt_len = 0, mlen = 10, olen;
  unsigned char *ptr = (unsigned char *) data, *pkt = NULL;
  char *smac, mac[6] = { 0, 0x0d, 0, 0x0d, 0x0d, 0x0e };
  char mybuf[1024] = { 0x03, 0, 0, 0, 0, 8, 0, 2, 0, 0 };
  int done_dns = 0, i;

  //Begin fuzz buffer
  strcat(fuzzbuf, fuzztype_elapsed_time);

  //Set message type
  switch (do_type) {
  case DO_REQ:
    mybuf[0] = 0x03;
    break;
  case DO_CON:
    mybuf[0] = 0x04;
    break;
  case DO_REN:
    mybuf[0] = 0x05;
    break;
  case DO_REL:
    mybuf[0] = 0x08;
    break;
  case DO_DEC:
    mybuf[0] = 0x09;
    break;
  case DO_INF:
    mybuf[0] = 0x0B;
    break;
  default:
    fprintf(stderr, "Error: Unknown do type %d\n", do_type);
    exit(-1);
    break;
  }

  //Skip over header to dhcp header
  if (do_hdr_size) {
    data += do_hdr_size;
    len -= do_hdr_size;
    if ((data[0] & 240) != 0x60)
      return;
  } else {
    data += 14;
    len -= 14;
  }

  if (len < 126 || data[6] != NXT_UDP || data[48] != 2)
    return;

  data += 48;
  len -= 48;

  //Copy transaction id and skip to message options
  memcpy(mybuf + 1, data + 1, 3); 
  data += 4;
  len -= 4;

  //Loop over options till reach end of header
  while (len >= 4) {
    //Set olen to the option length minus type and length fields and check for bogus packet
    if ((olen = data[2] * 256 + data[3]) > len - 4 || olen < 0) { //the 4 here is the 4 bytes for the option type and option length fields
      printf("Information: evil packet received\n");
      olen = 0;
      len = -1;
    }
    else {
      //Copy server identifier or IA_NA to message
      if (data[1] > 1 && data[1] <= 3 && !(data[1] == 2 && do_type == DO_CON) && !(data[1] == 3 && do_type == DO_INF)) { //skip copying server identifier for confirm or IA_NA for information request messages
        memcpy(mybuf + mlen, data, olen + 4);
        mlen += olen + 4;

        //Append server identifier fuzzing
        if (data[1] == 2)
          strcat(fuzzbuf, fuzztype_server_identifier);
        //Append IA_NA fuzzing + IA Address fuzzing
        else if (data[1] == 3) {
          strcat(fuzzbuf, fuzztype_IA_NA);
          if (olen > 12)
            strcat(fuzzbuf, fuzztype_IA_Address);
        }
        // printf("buf(%d): %s\n", strlen(fuzzbuf), fuzzbuf);
      } 
      //Copy client identifier to message
      else if (data[1] == 1) {
        memcpy(mybuf + mlen, data, olen + 4);
        mlen += olen + 4;
        //smac auf client mac in paket setzen
        if (olen == 14)
          smac = (char *) (data + 12);
        else
          smac = mac;

        //Append client identifier fuzzing
        strcat(fuzzbuf, fuzztype_client_identifier);
        // printf("buf(%d): %s\n", strlen(fuzzbuf), fuzzbuf);
      }
      //Copy dns option
      else if (data[1] == 39 && do_dns) {
        memcpy(mybuf + mlen, data, olen + 4);
        mybuf[mlen + 4] = 1;    // force server to write dns entry
        mlen += olen + 4;

        //Append dns fuzzing
        strcat(fuzzbuf, fuzztype_FQDN);
        for (i = 0; i < olen - 1; ++i)
          strcat(fuzzbuf, "B");           //Fuzz the domain name string
        strcat(fuzzbuf, fuzztype_option_request);
        // printf("buf(%d): %s\n", strlen(fuzzbuf), fuzzbuf);

        //Make sure we don't add dns twice
        done_dns = 1;
      }
      data += olen + 4;
      len -= olen + 4;
      if (len < 0) {
        printf("Information: evil packet received\n");
        len = -1;
      }
    }
  }

  //Add saved dns option onto this packet
  if (do_dns && !done_dns) {
    memcpy(mybuf + mlen, dns_option_hdr, dns_option_hdr_len);
    mlen += dns_option_hdr_len;

    //Append dns fuzzing
    olen = dns_option_hdr[2] * 256 + dns_option_hdr[3];
    strcat(fuzzbuf, fuzztype_FQDN);
    for (i = 0; i < olen - 1; ++i)
      strcat(fuzzbuf, "B");           //Fuzz the domain name string
    strcat(fuzzbuf, fuzztype_option_request);
    // printf("buf(%d): %s\n", strlen(fuzzbuf), fuzzbuf);
  }

  //Build and send fuzzed message packets
  if (len >= 0) {
    unsigned char* dst = thc_resolve6("ff02::1:2");

    if ((pkt = thc_create_ipv6_extended(interface, PREFER_LINK, &pkt_len, ptr + 38, dst, 1, 0, 0, 0, 0)) == NULL) {
      fprintf(stderr, "Error: Couldn't create dhcp requests ipv6 header\n");
      exit(-1);
    }

    if (thc_add_udp(pkt, &pkt_len, 546, 547, 0, mybuf, mlen) < 0) {
      fprintf(stderr, "Error: Couldn't create dhcp requests udp header\n");
      exit(-1);
    }

    if (thc_generate_pkt(interface, smac, ptr + 6, pkt, &pkt_len) < 0) {
      fprintf(stderr, "Error: Couldn't create dhcp requests ethernet header\n");
      exit(-1);
    }

    if (fuzz_loop(pkt, &pkt_len) < 0) {
      fprintf(stderr, "Error: Fuzzing request packet failed\n");
      exit(-1);
    }
    else {
      got_packet = 1; //Used to suppress timeout error
    }

    pkt = thc_destroy_packet(pkt);
  }

  //Truncate the fuzz buffer back to it's original length
  fuzzbuf[66] = 0;
  // printf("Trunc fuzzbuf: %s\n", fuzzbuf);
}

int main(int argc, char *argv[]) {
  char mac[6] = { 0, 0x0c, 0, 0, 0, 0 }, *pkt = NULL;
  // defines mac as 6 pieces and defines pkt as null.
  char wdatabuf[1024];
  //builds data buffer and sets memory size at 1024mb
  unsigned char *mac6 = mac, *src, *dst;
  //creates mac6 address usuing
  int i, s, len, pkt_len = 0, dlen = 0;
  int do_all = 1, use_real_mac = 1, use_real_link = 1;
  int state;

  if (argc < 2 || strncmp(argv[1], "-h", 2) == 0)
    help(argv[0]);

  if (getenv("THC_IPV6_PPPOE") != NULL || getenv("THC_IPV6_6IN4") != NULL) printf("WARNING: %s is not working with injection!\n", argv[0]);

  //Parse options
  while ((i = getopt(argc, argv, "123456789mn:t:e:T:dFp:fr")) >= 0) {
    switch (i) {
    case '1':
      do_type = DO_SOL;
      break;
    case '2':
      do_type = DO_REQ;
      break;
    case '3':
      do_type = DO_CON;
      break;
    case '4':
      do_type = DO_REN;
      break;
    case '5':
      do_type = DO_REB;
      break;
    case '6':
      do_type = DO_REL;
      break;
    case '7':
      do_type = DO_DEC;
      break;
    case '8':
      do_type = DO_INF;
      break;
    case 'm':
      fuzz_msg_type = 1;
      break;
    case 'n':
      no_send = atoi(optarg);
      break;
    case 't':
      test_start = atoi(optarg);
      break;
    case 'e':
      test_end = atoi(optarg);
      break;
    case 'T':
      test_end = test_start = atoi(optarg);
      break;
    case 'F':
      use_real_link = 0;        // no break
    case 'f':
      use_real_mac = 0;
      break;
    case 'p':
      ping = atoi(optarg);
      break;
    case 'd':
      do_dns = 1;
      break;
    case 'r':
      i = 0;
      break;                    // just to ignore -r
    default:
      fprintf(stderr, "Error: unknown option -%c\n", i);
      exit(-1);
    }
  }

  //Check options
  if (no_send < 1) {
    fprintf(stderr, "ERROR: -n number must be between one and 2 billion\n");
    exit(-1);
  }

  if (test_end < test_start) {
    printf("don't fuck up the command line options!\n");
    exit(-1);
  }

  memset(mac, 0, sizeof(mac));
  interface = argv[optind];
  dns_name = argv[optind + 1];
  if (use_real_link)
    src = thc_get_own_ipv6(interface, NULL, PREFER_LINK);
  else
    src = thc_resolve6("fe80::");
  if (use_real_mac) {
    mac6 = thc_get_own_mac(interface);
    memcpy(mac, mac6, sizeof(mac));
  }
  dst = thc_resolve6("ff02::1:2");
  setvbuf(stdout, NULL, _IONBF, 0);
  setvbuf(stderr, NULL, _IONBF, 0);

  // only to prevent our system to send icmp port unreachable messages
  if ((s = thc_bind_udp_port(546)) < 0)
    fprintf(stderr, "Warning: could not bind to 546/udp\n");
  if ((p = thc_pcap_init_promisc(interface, "ip6 and udp and dst port 546")) == NULL) {
    fprintf(stderr, "Error: can not open interface %s in promisc mode\n", interface);
    exit(-1);
  }

  //Establish state
  if (do_type == DO_SOL || do_type == DO_REB)
    state = STATELESS;
  else
    state = STATEFULL;

  // generate full fuzz mask for stateless types and partial for statefull types
  strcpy(fuzzbuf, fuzztype_ether);
  strcat(fuzzbuf, fuzztype_ip6);
  strcat(fuzzbuf, fuzztype_udp);
  if (fuzz_msg_type)
    strcat(fuzzbuf, fuzztype_dhcp6);
  else
    strcat(fuzzbuf, fuzztype_dhcp6no);
  if (state == STATELESS) {
    strcat(fuzzbuf, fuzztype_elapsed_time);
    strcat(fuzzbuf, fuzztype_client_identifier);
    strcat(fuzzbuf, fuzztype_IA_NA);
    if (do_dns)
      strcat(fuzzbuf, fuzztype_FQDN);
  }

  /** Generate packet **/
  len = sizeof(solicit);
  memcpy(wdatabuf, solicit, len);

  //Add dns option
  if (do_dns) {
    memcpy(wdatabuf + len, dnsupdate1, sizeof(dnsupdate1));
    memcpy(dns_option_hdr + dns_option_hdr_len, dnsupdate1, sizeof(dnsupdate1));
    dlen = len + 8;
    len += sizeof(dnsupdate1);
    dns_option_hdr_len += sizeof(dnsupdate1);

    //Append domain string prefix fuzz mask
    if (state == STATELESS) { //<-- Do fuzzbuffer later
      for (i = 0; i < 7; ++i) //7 == Length of hard coded domain prefix
        strcat(fuzzbuf, "B");
    }

    if (dns_name != NULL && strlen(dns_name) < 240) {
      if (dns_name[0] != '.') {
        wdatabuf[len] = '.';
        wdatabuf[dlen - 5]++;
        wdatabuf[dlen - 3]++;
        len++;
      }
      memcpy(wdatabuf + len, dns_name, strlen(dns_name) + 1);
      memcpy(dns_option_hdr + dns_option_hdr_len, dns_name, strlen(dns_name) + 1);
      wdatabuf[dlen - 5] += strlen(dns_name) + 1;
      wdatabuf[dlen - 3] += strlen(dns_name) + 1;
      len += strlen(dns_name) + 1;
      dns_option_hdr_len += strlen(dns_name) + 1;

      //Append variable length domain string suffix fuzz mask
      if (state == STATELESS) {
        for (i = 0; i < strlen(dns_name) + 1; ++i)
          strcat(fuzzbuf, "B");
      }
    }
    memcpy(wdatabuf + len, dnsupdate2, sizeof(dnsupdate2));
    memcpy(dns_option_hdr + dns_option_hdr_len, dnsupdate2, sizeof(dnsupdate2));
    len += sizeof(dnsupdate2);
    dns_option_hdr_len += sizeof(dnsupdate2);

    //Append option request (FQDN request) fuzz mask
    if (state == STATELESS){
      strcat(fuzzbuf, fuzztype_option_request);
    }
  }

  //Set message type
  if (state == STATELESS) {
    switch (do_type) {
    case DO_SOL:
      wdatabuf[0] = 0x01;
      break;
    case DO_REB:
      wdatabuf[0] = 0x06;
      break;
    default:
      break;
    }
  }
  
  //random src mac
  if (!use_real_link)
    for (i = 0; i < 8; i++)
      src[i + 8] = rand() % 256;

  // start0: 1-3 rand, 18-21 rand, 22-27 mac, 32-35 rand
  for (i = 0; i < 3; i++) {
    wdatabuf[i + 1] = rand() % 256;
    wdatabuf[i + 18] = rand() % 256;
    wdatabuf[i + 32] = rand() % 256;
    if (!use_real_mac) {
      mac[i * 2] = rand() % 256;
      mac[i * 2 + 1] = rand() % 256;
    }
    if (do_dns)
      wdatabuf[i + dlen] = 'a' + rand() % 26;
  }
  memcpy(wdatabuf + 22, mac, 6);

  if ((pkt = thc_create_ipv6_extended(interface, PREFER_LINK, &pkt_len, src, dst, 1, 0, 0, 0, 0)) == NULL)
    return -1;
  if (thc_add_udp(pkt, &pkt_len, 546, 547, 0, wdatabuf, len) < 0)
    return -1;

  if (thc_generate_pkt(interface, mac6, NULL, pkt, &pkt_len) < 0)
    return -1;

  //Fuzz solicit packet
  if (state == STATELESS) {
    if (fuzz_loop(pkt, &pkt_len) < 0)
      return -1;
  }

  //Fuzz request, confirm or renew paket
  else if (state == STATEFULL) {
    //Send a dhcp solicit to discover dhcpv6 servers
    if (thc_send_pkt(interface, pkt, &pkt_len) < 0) {
      fprintf(stderr, "Error: Failed to send initial solicit packet\n");
      return -1;
    }

    usleep(75); //<-- I don't really know why this is neccessary but it seems to be

    //Construct and fuzz packets using server identifier
    got_packet = 0;
    time_t start_time = time(NULL);
    while(time(NULL) - start_time < timeout) {
      while (thc_pcap_check(p, (char *) construct_from_adv_and_fuzz, NULL) > 0); //got_packet set in callback function
      if (got_packet)
        break;
    }
    if (!got_packet)
       fprintf(stderr, "Timeout: Didn't receive solicited advertisement packet within timeout. Is server down?\n");
  }

  pkt = thc_destroy_packet(pkt);

  // printf("fuzzbuf: %s\n", fuzzbuf);


  return 0;
}