git.zerfleddert.de Git - proxmark3-svn/blob - client/reveng/model.c

   1 /* model.c
   2  * Greg Cook, 26/Jul/2016
   3  */
   4
   5 /* CRC RevEng: arbitrary-precision CRC calculator and algorithm finder
   6  * Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015, 2016  Gregory Cook
   7  *
   8  * This file is part of CRC RevEng.
   9  *
  10  * CRC RevEng is free software: you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation, either version 3 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * CRC RevEng is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with CRC RevEng.  If not, see <https://www.gnu.org/licenses/>.
  22  */
  23
  24 /* 2016-02-22: split off preset.c
  25  * 2012-03-03: single-line Williams model string conversion
  26  * 2011-09-03: added mrev(), mnovel()
  27  * 2011-01-17: fixed ANSI C warnings (except preset models)
  28  * 2010-12-26: renamed CRC RevEng
  29  * 2010-12-18: minor change to mtostr() output format
  30  * 2010-12-15: added mcmp()
  31  * 2010-12-14: finished mtostr()
  32  * 2010-12-12: started models.c
  33  */
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include "reveng.h"
  39
  40 /* Private declarations */
  41
  42 static const poly_t pzero = PZERO;
  43
  44 /* Definitions */
  45
  46 void
  47 mcpy(model_t *dest, const model_t *src) {
  48         /* Copies the parameters of src to dest.
  49          * dest must be an initialised model.
  50          */
  51         if(!dest || !src) return;
  52         pcpy(&dest->spoly, src->spoly);
  53         pcpy(&dest->init, src->init);
  54         pcpy(&dest->xorout, src->xorout);
  55         pcpy(&dest->check, src->check);
  56         dest->flags = src->flags;
  57         /* link to the name as it is static */
  58         dest->name = src->name;
  59 }
  60
  61 void
  62 mfree(model_t *model) {
  63         /* Frees the parameters of model. */
  64         if(!model) return;
  65         pfree(&model->spoly);
  66         pfree(&model->init);
  67         pfree(&model->xorout);
  68         pfree(&model->check);
  69         /* not name as it is static */
  70         /* not model either, it might point to an array! */
  71 }
  72
  73 int
  74 mcmp(const model_t *a, const model_t *b) {
  75         /* Compares a and b for identical effect, i.e. disregarding
  76          * trailing zeroes in parameter polys.
  77          * Intended for bsearch().
  78          */
  79         int result;
  80         if(!a || !b) return(!b - !a);
  81         if((result = psncmp(&a->spoly, &b->spoly))) return(result);
  82         if((result = psncmp(&a->init, &b->init))) return(result);
  83         if((a->flags & P_REFIN) && (~b->flags & P_REFIN)) return(1);
  84         if((~a->flags & P_REFIN) && (b->flags & P_REFIN)) return(-1);
  85         if((a->flags & P_REFOUT) && (~b->flags & P_REFOUT)) return(1);
  86         if((~a->flags & P_REFOUT) && (b->flags & P_REFOUT)) return(-1);
  87         return(psncmp(&a->xorout, &b->xorout));
  88 }
  89
  90 char *
  91 mtostr(const model_t *model) {
  92         /* Returns a malloc()-ed string containing a Williams model
  93          * record representing the input model.
  94          * mcanon() should be called on the argument before printing.
  95          */
  96         size_t size;
  97         char *polystr, *initstr, *xorotstr, *checkstr, strbuf[512], *string = NULL;
  98
  99         if(!model) return(NULL);
 100         polystr = ptostr(model->spoly, P_RTJUST, 4);
 101         initstr = ptostr(model->init, P_RTJUST, 4);
 102         xorotstr = ptostr(model->xorout, P_RTJUST, 4);
 103         checkstr = ptostr(model->check, P_RTJUST, 4);
 104
 105         sprintf(strbuf, "%lu", plen(model->spoly));
 106         size =
 107                 70
 108                 + (model->name && *model->name ? 2 + strlen(model->name) : 6)
 109                 + strlen(strbuf)
 110                 + (polystr && *polystr ? strlen(polystr) : 6)
 111                 + (initstr && *initstr ? strlen(initstr) : 6)
 112                 + (model->flags & P_REFIN ? 4 : 5)
 113                 + (model->flags & P_REFOUT ? 4 : 5)
 114                 + (xorotstr && *xorotstr ? strlen(xorotstr) : 6)
 115                 + (checkstr && *checkstr ? strlen(checkstr) : 6);
 116         if((string = malloc(size))) {
 117                 sprintf(strbuf, "\"%s\"", model->name);
 118                 sprintf(string,
 119                                 "width=%lu  "
 120                                 "poly=0x%s  "
 121                                 "init=0x%s  "
 122                                 "refin=%s  "
 123                                 "refout=%s  "
 124                                 "xorout=0x%s  "
 125                                 "check=0x%s  "
 126                                 "name=%s",
 127                                 plen(model->spoly),
 128                                 polystr && *polystr ? polystr : "(none)",
 129                                 initstr && *initstr ? initstr :  "(none)",
 130                                 (model->flags & P_REFIN) ? "true" : "false",
 131                                 (model->flags & P_REFOUT) ? "true" : "false",
 132                                 xorotstr && *xorotstr ? xorotstr : "(none)",
 133                                 checkstr && *checkstr ? checkstr : "(none)",
 134                                 (model->name && *model->name) ? strbuf : "(none)");
 135         }
 136         free(polystr);
 137         free(initstr);
 138         free(xorotstr);
 139         free(checkstr);
 140         if(!string)
 141                 uerror("cannot allocate memory for model description");
 142         return(string);
 143 }
 144
 145 void
 146 mcanon(model_t *model) {
 147         /* canonicalise a model */
 148         unsigned long dlen;
 149
 150         if(!model) return;
 151
 152         /* extending on the right here. This preserves the functionality
 153          * of a presumed working model.
 154          */
 155         psnorm(&model->spoly);
 156         dlen = plen(model->spoly);
 157         praloc(&model->init, dlen);
 158         praloc(&model->xorout, dlen);
 159
 160         /* only calculate Check if missing.  Relying on all functions
 161          * changing parameters to call mnovel().  This is to ensure that
 162          * the Check value stored in the preset table is printed when
 163          * the model is dumped.  If something goes wrong with the
 164          * calculator then the discrepancy with the stored Check value
 165          * might be noticed.  Storing the Check value with each preset
 166          * is highly preferred.
 167          */
 168         if(!plen(model->check))
 169                 mcheck(model);
 170 }
 171
 172 void
 173 mcheck(model_t *model) {
 174         /* calculate a check for the model */
 175         poly_t checkstr, check;
 176
 177         /* generate the check string with the correct bit order */
 178         checkstr = strtop("313233343536373839", model->flags, 8);
 179         check = pcrc(checkstr, model->spoly, model->init, pzero, model->flags);
 180         if(model->flags & P_REFOUT)
 181                 prev(&check);
 182         psum(&check, model->xorout, 0UL);
 183         model->check = check;
 184         pfree(&checkstr);
 185 }
 186
 187 void
 188 mrev(model_t *model) {
 189         /* reverse the model to calculate reversed CRCs */
 190         /* Here we invert RefIn and RefOut so that the user need only
 191          * reverse the order of characters in the arguments, not the
 192          * characters themselves.  If RefOut=True, the mirror image of
 193          * Init seen through RefOut becomes XorOut, and as RefOut
 194          * becomes false, the XorOut value moved to Init stays upright.
 195          * If RefOut=False, Init transfers to XorOut without reflection
 196          * but the new Init must be reflected to present the same image,
 197          * as RefOut becomes true.
 198          */
 199         poly_t temp;
 200
 201         prcp(&model->spoly);
 202         if(model->flags & P_REFOUT)
 203                 prev(&model->init);
 204         else
 205                 prev(&model->xorout);
 206
 207         /* exchange init and xorout */
 208         temp = model->init;
 209         model->init = model->xorout;
 210         model->xorout = temp;
 211
 212         /* invert refin and refout */
 213         model->flags ^= P_REFIN | P_REFOUT;
 214
 215         mnovel(model);
 216 }
 217
 218 void
 219 mnovel(model_t *model) {
 220         /* remove name and check string from modified model */
 221         model->name = NULL;
 222         pfree(&model->check);
 223 }