common/crc.c

   1 //-----------------------------------------------------------------------------
   2 // Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
   3 //
   4 // This program is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // This program is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // See LICENSE.txt for the text of the license.
  15 //-----------------------------------------------------------------------------
  16 // Generic CRC calculation code.
  17 //-----------------------------------------------------------------------------
  18 // the Check value below in the comments is CRC of the string '123456789'
  19 //
  20 #include "crc.h"
  21
  22 #include "commonutil.h"
  23
  24 void crc_init_ref(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor, bool refin, bool refout) {
  25     crc_init(crc, order, polynom, initial_value, final_xor);
  26     crc->refin = refin;
  27     crc->refout = refout;
  28     crc_clear(crc);
  29 }
  30
  31 void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor) {
  32     crc->order = order;
  33     crc->topbit = BITMASK(order - 1);
  34     crc->polynom = polynom;
  35     crc->initial_value = initial_value;
  36     crc->final_xor = final_xor;
  37     crc->mask = (1L << order) - 1;
  38     crc->refin = false;
  39     crc->refout = false;
  40     crc_clear(crc);
  41 }
  42
  43 void crc_clear(crc_t *crc) {
  44
  45     crc->state = crc->initial_value & crc->mask;
  46     if (crc->refin)
  47         crc->state = reflect(crc->state, crc->order);
  48 }
  49
  50 void crc_update2(crc_t *crc, uint32_t data, int data_width) {
  51
  52     if (crc->refin)
  53         data = reflect(data, data_width);
  54
  55     // Bring the next byte into the remainder.
  56     crc->state ^= data << (crc->order - data_width);
  57
  58     for (uint8_t bit = data_width; bit > 0; --bit) {
  59
  60         if (crc->state & crc->topbit)
  61             crc->state = (crc->state << 1) ^ crc->polynom;
  62         else
  63             crc->state = (crc->state << 1);
  64     }
  65 }
  66
  67 void crc_update(crc_t *crc, uint32_t data, int data_width) {
  68     if (crc->refin)
  69         data = reflect(data, data_width);
  70
  71     int i;
  72     for (i = 0; i < data_width; i++) {
  73         int oldstate = crc->state;
  74         crc->state = crc->state >> 1;
  75         if ((oldstate ^ data) & 1) {
  76             crc->state ^= crc->polynom;
  77         }
  78         data >>= 1;
  79     }
  80 }
  81
  82 uint32_t crc_finish(crc_t *crc) {
  83     uint32_t val = crc->state;
  84     if (crc->refout)
  85         val = reflect(val, crc->order);
  86     return (val ^ crc->final_xor) & crc->mask;
  87 }
  88
  89 /*
  90 static void print_crc(crc_t *crc) {
  91     printf(" Order  %d\n Poly   %x\n Init   %x\n Final  %x\n Mask   %x\n topbit %x\n RefIn  %s\n RefOut %s\n State  %x\n",
  92         crc->order,
  93         crc->polynom,
  94         crc->initial_value,
  95         crc->final_xor,
  96         crc->mask,
  97         crc->topbit,
  98         (crc->refin) ? "TRUE":"FALSE",
  99         (crc->refout) ? "TRUE":"FALSE",
 100         crc->state
 101     );
 102 }
 103 */
 104
 105 // width=8  poly=0x31  init=0x00  refin=true  refout=true  xorout=0x00  check=0xA1  name="CRC-8/MAXIM"
 106 uint32_t CRC8Maxim(uint8_t *buff, size_t size) {
 107     crc_t crc;
 108     crc_init_ref(&crc, 8, 0x31, 0, 0, true, true);
 109     for (size_t i = 0; i < size; ++i) {
 110         crc_update2(&crc, buff[i], 8);
 111     }
 112     return crc_finish(&crc);
 113 }
 114 // width=8 poly=0x1d, init=0xc7 (0xe3 - WRONG! but it mentioned in MAD datasheet) refin=false  refout=false  xorout=0x00 name="CRC-8/MIFARE-MAD"
 115 uint32_t CRC8Mad(uint8_t *buff, size_t size) {
 116     crc_t crc;
 117     crc_init_ref(&crc, 8, 0x1d, 0xc7, 0, false, false);
 118     for (size_t i = 0; i < size; ++i) {
 119         crc_update2(&crc, buff[i], 8);
 120     }
 121     return crc_finish(&crc);
 122 }
 123 // width=4  poly=0xC, reversed poly=0x7  init=0x5   refin=true  refout=true  xorout=0x0000  check=  name="CRC-4/LEGIC"
 124 uint32_t CRC4Legic(uint8_t *buff, size_t size) {
 125     crc_t crc;
 126     crc_init_ref(&crc, 4, 0x19 >> 1, 0x5, 0, true, true);
 127     crc_update2(&crc, 1, 1); /* CMD_READ */
 128     crc_update2(&crc, buff[0], 8);
 129     crc_update2(&crc, buff[1], 8);
 130     return reflect(crc_finish(&crc), 4);
 131 }
 132 // width=8  poly=0x63, reversed poly=0x8D  init=0x55  refin=true  refout=true  xorout=0x0000  check=0xC6  name="CRC-8/LEGIC"
 133 // the CRC needs to be reversed before returned.
 134 uint32_t CRC8Legic(uint8_t *buff, size_t size) {
 135     crc_t crc;
 136     crc_init_ref(&crc, 8, 0x63, 0x55, 0, true, true);
 137     for (size_t i = 0; i < size; ++i) {
 138         crc_update2(&crc, buff[i], 8);
 139     }
 140     return reflect8(crc_finish(&crc));
 141 }
 142 // width=8  poly=0x7, init=0x2C  refin=false  refout=false  xorout=0x0000  check=0 name="CRC-8/CARDX"
 143 uint32_t CRC8Cardx(uint8_t *buff, size_t size) {
 144     crc_t crc;
 145     crc_init_ref(&crc, 8, 0x7, 0x2C, 0, false, false);
 146     for (size_t i = 0; i < size; ++i) {
 147         crc_update2(&crc, buff[i], 8);
 148     }
 149     return crc_finish(&crc);
 150 }
 151
 152 uint32_t CRC8Hitag1(uint8_t *buff, size_t size) {
 153     crc_t crc;
 154     crc_init_ref(&crc, 8, 0x1d, 0xff, 0, false, false);
 155     for (size_t i = 0; i < size; i++) {
 156         crc_update2(&crc, buff[i], 8);
 157     }
 158     return crc_finish(&crc);
 159 }
 160
 161 uint32_t CRC8Hitag1Bits(const uint8_t *buff, size_t bitsize) {
 162     crc_t crc;
 163     uint8_t data = 0;
 164     uint8_t n = 0;
 165     crc_init_ref(&crc, 8, 0x1d, 0xff, 0, false, false);
 166     size_t i;
 167     for (i = 0; i < bitsize; i++) {
 168         data <<= 1;
 169         data += (buff[i / 8] >> (7 - (i % 8))) & 1;
 170         n += 1;
 171         if (n == 8) {
 172             crc_update2(&crc, data, n);
 173             n = 0;
 174             data = 0;
 175         }
 176     }
 177     if (n > 0) {
 178         crc_update2(&crc, data, n);
 179     }
 180     return crc_finish(&crc);
 181 }