armsrc/optimized_cipherutils.c

   1 //-----------------------------------------------------------------------------
   2 // Borrowed initially from https://github.com/holiman/loclass
   3 // Copyright (C) 2014 Martin Holst Swende
   4 // Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
   5 //
   6 // This program is free software: you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation, either version 3 of the License, or
   9 // (at your option) any later version.
  10 //
  11 // This program is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15 //
  16 // See LICENSE.txt for the text of the license.
  17 //-----------------------------------------------------------------------------
  18 // WARNING
  19 //
  20 // THIS CODE IS CREATED FOR EXPERIMENTATION AND EDUCATIONAL USE ONLY.
  21 //
  22 // USAGE OF THIS CODE IN OTHER WAYS MAY INFRINGE UPON THE INTELLECTUAL
  23 // PROPERTY OF OTHER PARTIES, SUCH AS INSIDE SECURE AND HID GLOBAL,
  24 // AND MAY EXPOSE YOU TO AN INFRINGEMENT ACTION FROM THOSE PARTIES.
  25 //
  26 // THIS CODE SHOULD NEVER BE USED TO INFRINGE PATENTS OR INTELLECTUAL PROPERTY RIGHTS.
  27 //-----------------------------------------------------------------------------
  28 // It is a reconstruction of the cipher engine used in iClass, and RFID techology.
  29 //
  30 // The implementation is based on the work performed by
  31 // Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
  32 // Milosch Meriac in the paper "Dismantling IClass".
  33 //-----------------------------------------------------------------------------
  34 #include "optimized_cipherutils.h"
  35 #include <stdint.h>
  36
  37 /**
  38  *
  39  * @brief Return and remove the first bit (x0) in the stream : <x0 x1 x2 x3 ... xn >
  40  * @param stream
  41  * @return
  42  */
  43 bool headBit(BitstreamIn_t *stream) {
  44     int bytepos = stream->position >> 3; // divide by 8
  45     int bitpos = (stream->position++) & 7; // mask out 00000111
  46     return (*(stream->buffer + bytepos) >> (7 - bitpos)) & 1;
  47 }
  48 /**
  49  * @brief Return and remove the last bit (xn) in the stream: <x0 x1 x2 ... xn>
  50  * @param stream
  51  * @return
  52  */
  53 bool tailBit(BitstreamIn_t *stream) {
  54     int bitpos = stream->numbits - 1 - (stream->position++);
  55
  56     int bytepos = bitpos >> 3;
  57     bitpos &= 7;
  58     return (*(stream->buffer + bytepos) >> (7 - bitpos)) & 1;
  59 }
  60 /**
  61  * @brief Pushes bit onto the stream
  62  * @param stream
  63  * @param bit
  64  */
  65 void pushBit(BitstreamOut_t *stream, bool bit) {
  66     int bytepos = stream->position >> 3; // divide by 8
  67     int bitpos = stream->position & 7;
  68     *(stream->buffer + bytepos) |= (bit) << (7 - bitpos);
  69     stream->position++;
  70     stream->numbits++;
  71 }
  72
  73 /**
  74  * @brief Pushes the lower six bits onto the stream
  75  * as b0 b1 b2 b3 b4 b5 b6
  76  * @param stream
  77  * @param bits
  78  */
  79 void push6bits(BitstreamOut_t *stream, uint8_t bits) {
  80     pushBit(stream, bits & 0x20);
  81     pushBit(stream, bits & 0x10);
  82     pushBit(stream, bits & 0x08);
  83     pushBit(stream, bits & 0x04);
  84     pushBit(stream, bits & 0x02);
  85     pushBit(stream, bits & 0x01);
  86 }
  87
  88 /**
  89  * @brief bitsLeft
  90  * @param stream
  91  * @return number of bits left in stream
  92  */
  93 int bitsLeft(BitstreamIn_t *stream) {
  94     return stream->numbits - stream->position;
  95 }
  96 /**
  97  * @brief numBits
  98  * @param stream
  99  * @return Number of bits stored in stream
 100  */
 101 void x_num_to_bytes(uint64_t n, size_t len, uint8_t *dest) {
 102     while (len--) {
 103         dest[len] = (uint8_t) n;
 104         n >>= 8;
 105     }
 106 }
 107
 108 uint64_t x_bytes_to_num(uint8_t *src, size_t len) {
 109     uint64_t num = 0;
 110     while (len--) {
 111         num = (num << 8) | (*src);
 112         src++;
 113     }
 114     return num;
 115 }
 116