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 <inttypes.h>
  39 #include "reveng.h"
  40
  41 /* Private declarations */
  42
  43 static const poly_t pzero = PZERO;
  44
  45 /* Definitions */
  46
  47 void
  48 mcpy(model_t *dest, const model_t *src) {
  49         /* Copies the parameters of src to dest.
  50          * dest must be an initialised model.
  51          */
  52         if(!dest || !src) return;
  53         pcpy(&dest->spoly, src->spoly);
  54         pcpy(&dest->init, src->init);
  55         pcpy(&dest->xorout, src->xorout);
  56         pcpy(&dest->check, src->check);
  57         dest->flags = src->flags;
  58         /* link to the name as it is static */
  59         dest->name = src->name;
  60 }
  61
  62 void
  63 mfree(model_t *model) {
  64         /* Frees the parameters of model. */
  65         if(!model) return;
  66         pfree(&model->spoly);
  67         pfree(&model->init);
  68         pfree(&model->xorout);
  69         pfree(&model->check);
  70         /* not name as it is static */
  71         /* not model either, it might point to an array! */
  72 }
  73
  74 int
  75 mcmp(const model_t *a, const model_t *b) {
  76         /* Compares a and b for identical effect, i.e. disregarding
  77          * trailing zeroes in parameter polys.
  78          * Intended for bsearch().
  79          */
  80         int result;
  81         if(!a || !b) return(!b - !a);
  82         if((result = psncmp(&a->spoly, &b->spoly))) return(result);
  83         if((result = psncmp(&a->init, &b->init))) return(result);
  84         if((a->flags & P_REFIN) && (~b->flags & P_REFIN)) return(1);
  85         if((~a->flags & P_REFIN) && (b->flags & P_REFIN)) return(-1);
  86         if((a->flags & P_REFOUT) && (~b->flags & P_REFOUT)) return(1);
  87         if((~a->flags & P_REFOUT) && (b->flags & P_REFOUT)) return(-1);
  88         return(psncmp(&a->xorout, &b->xorout));
  89 }
  90
  91 char *
  92 mtostr(const model_t *model) {
  93         /* Returns a malloc()-ed string containing a Williams model
  94          * record representing the input model.
  95          * mcanon() should be called on the argument before printing.
  96          */
  97         size_t size;
  98         char *polystr, *initstr, *xorotstr, *checkstr, strbuf[512], *string = NULL;
  99
 100         if(!model) return(NULL);
 101         polystr = ptostr(model->spoly, P_RTJUST, 4);
 102         initstr = ptostr(model->init, P_RTJUST, 4);
 103         xorotstr = ptostr(model->xorout, P_RTJUST, 4);
 104         checkstr = ptostr(model->check, P_RTJUST, 4);
 105
 106         sprintf(strbuf, "%lu", plen(model->spoly));
 107         size =
 108                 70
 109                 + (model->name && *model->name ? 2 + strlen(model->name) : 6)
 110                 + strlen(strbuf)
 111                 + (polystr && *polystr ? strlen(polystr) : 6)
 112                 + (initstr && *initstr ? strlen(initstr) : 6)
 113                 + (model->flags & P_REFIN ? 4 : 5)
 114                 + (model->flags & P_REFOUT ? 4 : 5)
 115                 + (xorotstr && *xorotstr ? strlen(xorotstr) : 6)
 116                 + (checkstr && *checkstr ? strlen(checkstr) : 6);
 117         if((string = malloc(size))) {
 118                 sprintf(strbuf, "\"%s\"", model->name);
 119                 sprintf(string,
 120                                 "width=%lu"
 121                                 "poly=0x%s  "
 122                                 "init=0x%s  "
 123                                 "refin=%s  "
 124                                 "refout=%s  "
 125                                 "xorout=0x%s  "
 126                                 "check=0x%s  "
 127                                 "name=%s",
 128                                 plen(model->spoly),
 129                                 polystr && *polystr ? polystr : "(none)",
 130                                 initstr && *initstr ? initstr :  "(none)",
 131                                 (model->flags & P_REFIN) ? "true" : "false",
 132                                 (model->flags & P_REFOUT) ? "true" : "false",
 133                                 xorotstr && *xorotstr ? xorotstr : "(none)",
 134                                 checkstr && *checkstr ? checkstr : "(none)",
 135                                 (model->name && *model->name) ? strbuf : "(none)");
 136         }
 137         free(polystr);
 138         free(initstr);
 139         free(xorotstr);
 140         free(checkstr);
 141         if(!string)
 142                 uerror("cannot allocate memory for model description");
 143         return(string);
 144 }
 145
 146 void
 147 mcanon(model_t *model) {
 148         /* canonicalise a model */
 149         unsigned long dlen;
 150
 151         if(!model) return;
 152
 153         /* extending on the right here. This preserves the functionality
 154          * of a presumed working model.
 155          */
 156         psnorm(&model->spoly);
 157         dlen = plen(model->spoly);
 158         praloc(&model->init, dlen);
 159         praloc(&model->xorout, dlen);
 160
 161         /* only calculate Check if missing.  Relying on all functions
 162          * changing parameters to call mnovel().  This is to ensure that
 163          * the Check value stored in the preset table is printed when
 164          * the model is dumped.  If something goes wrong with the
 165          * calculator then the discrepancy with the stored Check value
 166          * might be noticed.  Storing the Check value with each preset
 167          * is highly preferred.
 168          */
 169         if(!plen(model->check))
 170                 mcheck(model);
 171 }
 172
 173 void
 174 mcheck(model_t *model) {
 175         /* calculate a check for the model */
 176         poly_t checkstr, check;
 177
 178         /* generate the check string with the correct bit order */
 179         checkstr = strtop("313233343536373839", model->flags, 8);
 180         check = pcrc(checkstr, model->spoly, model->init, pzero, model->flags);
 181         if(model->flags & P_REFOUT)
 182                 prev(&check);
 183         psum(&check, model->xorout, 0UL);
 184         model->check = check;
 185         pfree(&checkstr);
 186 }
 187
 188 void
 189 mrev(model_t *model) {
 190         /* reverse the model to calculate reversed CRCs */
 191         /* Here we invert RefIn and RefOut so that the user need only
 192          * reverse the order of characters in the arguments, not the
 193          * characters themselves.  If RefOut=True, the mirror image of
 194          * Init seen through RefOut becomes XorOut, and as RefOut
 195          * becomes false, the XorOut value moved to Init stays upright.
 196          * If RefOut=False, Init transfers to XorOut without reflection
 197          * but the new Init must be reflected to present the same image,
 198          * as RefOut becomes true.
 199          */
 200         poly_t temp;
 201
 202         prcp(&model->spoly);
 203         if(model->flags & P_REFOUT)
 204                 prev(&model->init);
 205         else
 206                 prev(&model->xorout);
 207
 208         /* exchange init and xorout */
 209         temp = model->init;
 210         model->init = model->xorout;
 211         model->xorout = temp;
 212
 213         /* invert refin and refout */
 214         model->flags ^= P_REFIN | P_REFOUT;
 215
 216         mnovel(model);
 217 }
 218
 219 void
 220 mnovel(model_t *model) {
 221         /* remove name and check string from modified model */
 222         model->name = NULL;
 223         pfree(&model->check);
 224 }