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aircrack-ptw-lib.c

/*
 *  Copyright (c) 2007, 2008, 2009 Erik Tews, Andrei Pychkine and Ralf-Philipp Weinmann.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *
 *  In addition, as a special exception, the copyright holders give
 *  permission to link the code of portions of this program with the
 *  OpenSSL library under certain conditions as described in each
 *  individual source file, and distribute linked combinations
 *  including the two.
 *  You must obey the GNU General Public License in all respects
 *  for all of the code used other than OpenSSL. *  If you modify
 *  file(s) with this exception, you may extend this exception to your
 *  version of the file(s), but you are not obligated to do so. *  If you
 *  do not wish to do so, delete this exception statement from your
 *  version. *  If you delete this exception statement from all source
 *  files in the program, then also delete it here.
 */

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include "pcap.h"
#include "aircrack-ptw-lib.h"
#include "aircrack-ng.h"

#define n PTW_n
#define CONTROLSESSIONS PTW_CONTROLSESSIONS
#define KSBYTES PTW_KSBYTES
#define IVBYTES PTW_IVBYTES
#define TESTBYTES 6


// Internal state of rc4
typedef struct {
      uint8_t i;
      uint8_t j;
      uint8_t s[n];
} rc4state;


// Helper structures for sorting
typedef struct {
      int keybyte;
      uint8_t value;
      int distance;
} sorthelper;

typedef struct {
      int keybyte;
      double difference;
} doublesorthelper;

// The rc4 initial state, the idendity permutation
static const uint8_t rc4initial[] =
{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};


// Values for p_correct_i
static const double eval[] = {
0.00534392069257663,
0.00531787585068872,
0.00531345769225911,
0.00528812219217898,
0.00525997750378221,
0.00522647312237696,
0.00519132541143668,
0.0051477139367225,
0.00510438884847959,
0.00505484662057323,
0.00500502783556246,
0.00495094196451801,
0.0048983441590402};

int tried, max_tries;
int depth[KEYHSBYTES];
PTW_tableentry keytable[KEYHSBYTES][n];

// For sorting
static int compare(const void * ina, const void * inb) {
        PTW_tableentry * a = (PTW_tableentry * )ina;
        PTW_tableentry * b = (PTW_tableentry * )inb;
        if (a->votes > b->votes) {
                return -1;
        } else if (a->votes == b->votes) {
                return 0;
        } else {
                return 1;
        }
}

// For sorting
static int comparedoublesorthelper(const void * ina, const void * inb) {
        doublesorthelper * a = (doublesorthelper * )ina;
        doublesorthelper * b = (doublesorthelper * )inb;
        if (a->difference > b->difference) {
                return 1;
        } else if (a->difference == b->difference) {
                return 0;
        } else {
                return -1;
        }
}


// RC4 key setup
static void rc4init ( uint8_t * key, int keylen, rc4state * state) {
      int i;
      unsigned char j;
      uint8_t tmp;
      memcpy(state->s, &rc4initial, n);
      j = 0;
      for (i = 0; i < n; i++) {
                /*  this should be:
                    j = (j + state->s[i] + key[i % keylen]) % n;
                    but as "j" is declared as unsigned char and n equals 256,
                    we can "optimize" it
                */
            j = (j + state->s[i] + key[i % keylen]);
            tmp = state->s[i];
            state->s[i] = state->s[j];
            state->s[j] = tmp;
      }
      state->i = 0;
      state->j = 0;
}

// RC4 key stream generation
static uint8_t rc4update(rc4state * state) {
      uint8_t tmp;
      uint8_t k;
      state->i++;
      state->j += state->s[state->i];
      tmp = state->s[state->i];
      state->s[state->i] = state->s[state->j];
      state->s[state->j] = tmp;
      k = state->s[state->i] + state->s[state->j];

      return state->s[k];
}

// For sorting
static int comparesorthelper(const void * ina, const void * inb) {
      sorthelper * a = (sorthelper * ) ina;
      sorthelper * b = (sorthelper * ) inb;
      if (a->distance > b->distance) {
            return 1;
      } else if (a->distance == b->distance) {
            return 0;
      } else {
            return -1;
      }
}

/*
 * Guess the values for sigma_i
 * ivlen - how long was the iv (is used differently in original klein attack)
 * iv - IV which was used for this packet
 * keystream - keystream recovered
 * result - buffer for the values of sigma_i
 * kb - how many keybytes should be guessed
 */
static void guesskeybytes(int ivlen, uint8_t * iv, uint8_t * keystream, uint8_t * result, int kb) {
        uint8_t state[n];
        uint8_t j = 0;
        uint8_t tmp;
        int i;
        int jj = ivlen;
        uint8_t ii;
        uint8_t s = 0;
        memcpy(state, rc4initial, n);
        for (i = 0; i < ivlen; i++) {
                j += state[i] + iv[i];
                tmp = state[i];
                state[i] = state[j];
                state[j] = tmp;
        }
        for (i = 0; i < kb; i++) {
                tmp = jj - keystream[jj-1];
                ii = 0;
                while(tmp != state[ii]) {
                        ii++;
                }
                s += state[jj];
                ii -= (j+s);
                result[i] = ii;
                jj++;
        }
        return;
}

/*
 * Is a guessed key correct?
 */
static int correct(PTW_attackstate * state, uint8_t * key, int keylen) {
      int i;
        int j;
        int k;
        uint8_t keybuf[PTW_KSBYTES];
        rc4state rc4state;

      // We need at least 3 sessions to be somehow certain
      if (state->sessions_collected < 3) {
            return 0;
      }

        tried++;

        k = rand()%(state->sessions_collected-10);
        for ( i=k; i < k+10; i++) {
                memcpy(&keybuf[IVBYTES], key, keylen);
                memcpy(keybuf, state->sessions[i].iv, IVBYTES);
                rc4init(keybuf, keylen+IVBYTES, &rc4state);
                for (j = 0; j < TESTBYTES; j++) {
                        if  ((rc4update(&rc4state) ^ state->sessions[i].keystream[j]) != 0) {
                                return 0;
                        }
                }
        }
        return 1;
}

/*
 * Calculate the squaresum of the errors for both distributions
 */
static void getdrv(PTW_tableentry orgtable[][n], int keylen, double * normal, double * ausreiser) {
        int i,j;
      int numvotes = 0;
        double e;
      double e2;
      double emax;
        double help = 0.0;
      double maxhelp = 0;
      double maxi = 0;
        for (i = 0; i < n; i++) {
                numvotes += orgtable[0][i].votes;
        }
        e = numvotes/n;
        for (i = 0; i < keylen; i++) {
            emax = eval[i] * numvotes;
            e2 = ((1.0 - eval[i])/255.0) * numvotes;
            normal[i] = 0;
            ausreiser[i] = 0;
            maxhelp = 0;
            maxi = 0;
            for (j = 0; j < n; j++) {
                  if (orgtable[i][j].votes > maxhelp) {
                        maxhelp = orgtable[i][j].votes;
                        maxi = j;
                  }
            }
                for (j = 0; j < n; j++) {
                  if (j == maxi) {
                        help = (1.0-orgtable[i][j].votes/emax);
                  } else {
                        help = (1.0-orgtable[i][j].votes/e2);
                  }
                  help = help*help;
                  ausreiser[i] += help;
                  help = (1.0-orgtable[i][j].votes/e);
                  help = help*help;
                  normal[i] += help;
                }
        }
}

/*
 * Guess a single keybyte
 */
static int doRound(PTW_tableentry sortedtable[][n], int keybyte, int fixat, uint8_t fixvalue, int * searchborders, uint8_t * key, int keylen, PTW_attackstate * state, uint8_t sum, int * strongbytes, int * bf, int validchars[][n]) {
      int i;
      uint8_t tmp;

      if(!opt.is_quiet && keybyte < 4)
            show_wep_stats( keylen -1, 0, keytable, searchborders, depth, tried );
      if (keybyte > 0) {
            if (!validchars[keybyte-1][key[keybyte-1]]) {
                  return 0;
            }
      }
      if (keybyte == keylen) {
            return correct(state, key, keylen);
      } else if (bf[keybyte] == 1) {
            for (i = 0; i < n; i++) {
                  key[keybyte] = i;
                  if (doRound(sortedtable, keybyte+1, fixat, fixvalue, searchborders, key, keylen, state, sum+i%n, strongbytes, bf, validchars)) {
                        return 1;
                  }
            }
            return 0;
        } else if (keybyte == fixat) {
                key[keybyte] = fixvalue-sum;
                return doRound(sortedtable, keybyte+1, fixat, fixvalue, searchborders, key, keylen, state, fixvalue, strongbytes, bf, validchars);
      } else if (strongbytes[keybyte] == 1) {
            // printf("assuming byte %d to be strong\n", keybyte);
            tmp = 3 + keybyte;
            for (i = keybyte-1; i >= 1; i--) {
                  tmp += 3 + key[i] + i;
                  key[keybyte] = n-tmp;
                  if(doRound(sortedtable, keybyte+1, fixat, fixvalue, searchborders, key, keylen, state, (n-tmp+sum)%n, strongbytes, bf, validchars) == 1) {
                        printf("hit with strongbyte for keybyte %d\n", keybyte);
                        return 1;
                  }
            }
            return 0;
      } else {
            for (i = 0; i < searchborders[keybyte]; i++) {
                    key[keybyte] = sortedtable[keybyte][i].b - sum;
                    if(!opt.is_quiet)
                    {
                        depth[keybyte] = i;
                        keytable[keybyte][i].b = key[keybyte];
                    }
                    if (doRound(sortedtable, keybyte+1, fixat, fixvalue, searchborders, key, keylen, state, sortedtable[keybyte][i].b, strongbytes, bf, validchars)) {
                        return 1;
                  }
            }
            return 0;
      }
}

/*
 * Do the actual computation of the key
 */
static int doComputation(PTW_attackstate * state, uint8_t * key, int keylen, PTW_tableentry table[][n], sorthelper * sh2, int * strongbytes, int keylimit, int * bf, int validchars[][n]) {
      int i,j;
      int choices[KEYHSBYTES];
      int prod;
      int fixat;
      int fixvalue;

        if(!opt.is_quiet)
            memcpy(keytable, table, sizeof(PTW_tableentry) * n * keylen);

      for (i = 0; i < keylen; i++) {
            if (strongbytes[i] == 1) {
                  choices[i] = i;
            } else {
                  choices[i] = 1;
            }
      }
      i = 0;
      prod = 0;
      fixat = -1;
      fixvalue = 0;
        max_tries = keylimit;

      while(prod < keylimit) {
            if (doRound(table, 0, fixat, fixvalue, choices, key, keylen, state, 0, strongbytes, bf, validchars) == 1) {
                  // printf("hit with %d choices\n", prod);
                  if(!opt.is_quiet)
                        show_wep_stats( keylen -1, 1, keytable, choices, depth, tried );
                  return 1;
            }
            while( (i < keylen * (n-1)) && ((strongbytes[sh2[i].keybyte] == 1) || (bf[sh2[i].keybyte] == 1) ) ) {
                  i++;
            }
            if(i >= (keylen * (n-1)))
            {
                  break;
            }
            choices[sh2[i].keybyte]++;
            fixat = sh2[i].keybyte;
            // printf("choices[%d] is now %d\n", sh2[i].keybyte, choices[sh2[i].keybyte]);
            fixvalue = sh2[i].value;
            prod = 1;
            for (j = 0; j < keylen; j++) {
                  prod *= choices[j];
                  if (bf[j] == 1) {
                        prod *= n;
                  }
            }

                /*
            do {
                  i++;
            } while (strongbytes[sh2[i].keybyte] == 1);
            */
            i++;

            if(!opt.is_quiet)
                  show_wep_stats( keylen -1, 0, keytable, choices, depth, tried );

      }
      if(!opt.is_quiet)
            show_wep_stats( keylen -1, 1, keytable, choices, depth, tried );
    return 0;
}


/*
 * Guess which key bytes could be strong and start actual computation of the key
 */
int PTW_computeKey(PTW_attackstate * state, uint8_t * keybuf, int keylen, int testlimit, int * bf, int validchars[][n], int attacks) {
      int strongbytes[KEYHSBYTES];
      double normal[KEYHSBYTES];
      double ausreisser[KEYHSBYTES];
      doublesorthelper helper[KEYHSBYTES];
      int simple, onestrong, twostrong;
      int i,j;
      uint8_t fullkeybuf[PTW_KSBYTES];
      uint8_t guessbuf[PTW_KSBYTES];
      sorthelper(*sh)[n-1];
      PTW_tableentry (*table)[n] = alloca(sizeof(PTW_tableentry) * n * keylen);

        tried=0;
      sh = NULL;

      if (table == NULL) {
            printf("could not allocate memory\n");
            exit(-1);
      }

      if(!(attacks & NO_KLEIN))
      {
            // Try the original klein attack first
            for (i = 0; i < keylen; i++) {
                  memset(&table[i][0], 0, sizeof(PTW_tableentry) * n);
                  for (j = 0; j < n; j++) {
                        table[i][j].b = j;
                  }
                  for (j = 0; j < state->packets_collected; j++) {
                        // fullkeybuf[0] = state->allsessions[j].iv[0];
                        memcpy(fullkeybuf, state->allsessions[j].iv, 3 * sizeof(uint8_t));
                        guesskeybytes(i+3, fullkeybuf, state->allsessions[j].keystream, guessbuf, 1);
                        table[i][guessbuf[0]].votes += state->allsessions[j].weight;
                  }
                  qsort(&table[i][0], n, sizeof(PTW_tableentry), &compare);
                  j = 0;
                  while(!validchars[i][table[i][j].b]) {
                        j++;
                  }
                  // printf("guessing i = %d, b = %d\n", i, table[0][0].b);
                  fullkeybuf[i+3] = table[i][j].b;
            }
            if (correct(state, &fullkeybuf[3], keylen)) {
                  memcpy(keybuf, &fullkeybuf[3], keylen * sizeof(uint8_t));
                  // printf("hit without correction\n");
                  return 1;
            }
      }


      if(!(attacks & NO_PTW))
      {
            memcpy(table, state->table, sizeof(PTW_tableentry) * n * keylen);

            onestrong = (testlimit/10)*2;
            twostrong = (testlimit/10)*1;
            simple = testlimit - onestrong - twostrong;

            // now, sort the table
            for (i = 0; i < keylen; i++) {
                  qsort(&table[i][0], n, sizeof(PTW_tableentry), &compare);
                  strongbytes[i] = 0;
            }

            sh = alloca(sizeof(sorthelper) * (n-1) * keylen);
            if (sh == NULL) {
                  printf("could not allocate memory\n");
                  exit(-1);
            }


            for (i = 0; i < keylen; i++) {
                  for (j = 1; j < n; j++) {
                        sh[i][j-1].distance = table[i][0].votes - table[i][j].votes;
                        sh[i][j-1].value = table[i][j].b;
                        sh[i][j-1].keybyte = i;
                  }
            }
            qsort(sh, (n-1)*keylen, sizeof(sorthelper), &comparesorthelper);


            if (doComputation(state, keybuf, keylen, table, (sorthelper *) sh, strongbytes, simple, bf, validchars)) {
                  return 1;
            }

            // Now one strong byte
            getdrv(state->table, keylen, normal, ausreisser);
            for (i = 0; i < keylen-1; i++) {
                  helper[i].keybyte = i+1;
                  helper[i].difference = normal[i+1] - ausreisser[i+1];
            }
            qsort(helper, keylen-1, sizeof(doublesorthelper), &comparedoublesorthelper);
            // do not use bf-bytes as strongbytes
            i = 0;
            while(bf[helper[i].keybyte] == 1) {
                  i++;
            }
            strongbytes[helper[i].keybyte] = 1;
            if (doComputation(state, keybuf, keylen, table, (sorthelper *) sh, strongbytes, onestrong, bf, validchars)) {
                  return 1;
            }

            // two strong bytes
            i++;
            while(bf[helper[i].keybyte] == 1) {
                  i++;
            }
            strongbytes[helper[i].keybyte] = 1;
            if (doComputation(state, keybuf, keylen, table, (sorthelper *) sh, strongbytes, twostrong, bf, validchars)) {
                  return 1;
            }
      }
      return 0;
}

/*
 * Add a new session to the attack
 * state - state of attack
 * iv - IV used in the session
 * keystream - recovered keystream from the session
 */
int PTW_addsession(PTW_attackstate * state, uint8_t * iv, uint8_t * keystream, int * weight, int total) {
      int i,j;
      int il;
      int ir;
      uint8_t buf[PTW_KEYHSBYTES];

      i = (iv[0] << 16) | (iv[1] << 8) | (iv[2]);
      il = i/8;
      ir = 1 << (i%8);
      if ((state->seen_iv[il] & ir) == 0) {
            state->seen_iv[il] |= ir;
            for (j = 0; j < total; j++) {
                  state->packets_collected++;
                  guesskeybytes(IVBYTES, iv, &keystream[KSBYTES*j], buf, PTW_KEYHSBYTES);
                      for (i = 0; i < KEYHSBYTES; i++) {
                        state->table[i][buf[i]].votes += weight[j];
                      }
                  if (state->allsessions_size < state->packets_collected) {
                        state->allsessions_size = state->allsessions_size << 1;
                        state->allsessions = realloc(state->allsessions, state->allsessions_size * sizeof(PTW_session));
                        if (state->allsessions == NULL) {
                              printf("could not allocate memory\n");
                              exit(-1);
                        }
                  }
                  memcpy(state->allsessions[state->packets_collected-1].iv, iv, IVBYTES);
                  memcpy(state->allsessions[state->packets_collected-1].keystream, &keystream[KSBYTES*j], KSBYTES);
                  state->allsessions[state->packets_collected-1].weight = weight[j];
            }
                if ((state->sessions_collected < CONTROLSESSIONS)) {
                        memcpy(state->sessions[state->sessions_collected].iv, iv, IVBYTES);
                        memcpy(state->sessions[state->sessions_collected].keystream, keystream, KSBYTES);
                        state->sessions_collected++;
                }

            return 1;
      } else {
            return 0;
      }
}

/*
 * Allocate a new attackstate
 */
PTW_attackstate * PTW_newattackstate() {
      int i,k;
      PTW_attackstate * state = NULL;
      state = malloc(sizeof(PTW_attackstate));
      if (state == NULL) {
            return NULL;
      }
      memset(state, 0, sizeof(PTW_attackstate));
      for (i = 0; i < PTW_KEYHSBYTES; i++) {
                for (k = 0; k < n; k++) {
                        state->table[i][k].b = k;
                }
        }
      state->allsessions = malloc(4096 * sizeof(PTW_session));
      state->allsessions_size = 4096;
      if (state->allsessions == NULL) {
            printf("could not allocate memory\n");
            exit(-1);
      }

        return state;
}

/*
 * Free an allocated attackstate
 */
void PTW_freeattackstate(PTW_attackstate * state) {
      free(state->allsessions);
      free(state);
      return;
}

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