piotr | faacc72 | 2014-07-20 23:48:32 +0200 | [diff] [blame] | 1 | /* |
ptrkrysik | 8038b2e | 2014-12-15 23:10:48 +0100 | [diff] [blame] | 2 | The Hacker's Choice - http://www.thc.org |
| 3 | Part of THC's GSM SCANNER PROJECT |
| 4 | */ |
| 5 | |
piotr | faacc72 | 2014-07-20 23:48:32 +0200 | [diff] [blame] | 6 | |
| 7 | #include "fire_crc.h" |
| 8 | #include <stdio.h> |
| 9 | #include <string.h> |
| 10 | |
| 11 | #define REM(x, y) (x) % (y) |
| 12 | |
| 13 | static int FC_syndrome_shift(FC_CTX *ctx, unsigned int bit); |
| 14 | |
| 15 | static int |
| 16 | outit(int *data, int len) |
| 17 | { |
| 18 | int i; |
| 19 | |
| 20 | for (i = 0; i < len; i++) |
| 21 | printf("%d ", data[i]); |
| 22 | printf("\n"); |
ptrkrysik | 5ad7d63 | 2014-12-13 11:39:53 +0100 | [diff] [blame] | 23 | return 0; |
piotr | faacc72 | 2014-07-20 23:48:32 +0200 | [diff] [blame] | 24 | } |
| 25 | |
| 26 | int |
| 27 | FC_init(FC_CTX *ctx, unsigned int crc_size, unsigned int data_size) |
| 28 | { |
| 29 | ctx->crc_size = crc_size; |
| 30 | ctx->data_size = data_size; |
| 31 | ctx->syn_start = 0; |
| 32 | |
| 33 | return 0; |
| 34 | } |
| 35 | |
| 36 | int |
| 37 | FC_check_crc(FC_CTX *ctx, unsigned char *input_bits, unsigned char *control_data) |
| 38 | { |
| 39 | int j,error_count = 0, error_index = 0, success_flag = 0, syn_index = 0; |
| 40 | unsigned int i; |
| 41 | |
| 42 | ctx->syn_start = 0; |
| 43 | // reset the syndrome register |
| 44 | memset(ctx->syndrome_reg, 0, sizeof ctx->syndrome_reg); |
| 45 | |
| 46 | // shift in the data bits |
| 47 | for (i=0; i < ctx->data_size; i++) { |
| 48 | error_count = FC_syndrome_shift(ctx, input_bits[i]); |
| 49 | control_data[i] = input_bits[i]; |
| 50 | } |
| 51 | |
| 52 | // shift in the crc bits |
| 53 | for (i=0; i < ctx->crc_size; i++) { |
| 54 | error_count = FC_syndrome_shift(ctx, 1-input_bits[i+ctx->data_size]); |
| 55 | } |
| 56 | |
| 57 | // Find position of error burst |
| 58 | if (error_count == 0) { |
| 59 | error_index = 0; |
| 60 | } |
| 61 | else { |
| 62 | error_index = 1; |
| 63 | error_count = FC_syndrome_shift(ctx, 0); |
| 64 | error_index += 1; |
| 65 | while (error_index < (ctx->data_size + ctx->crc_size) ) { |
| 66 | error_count = FC_syndrome_shift(ctx, 0); |
| 67 | error_index += 1; |
| 68 | if ( error_count == 0 ) break; |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | // Test for correctable errors |
| 73 | //printf("error_index %d\n",error_index); |
| 74 | if (error_index == 224) success_flag = 0; |
| 75 | else { |
| 76 | |
| 77 | // correct index depending on the position of the error |
| 78 | if (error_index == 0) syn_index = error_index; |
| 79 | else syn_index = error_index - 1; |
| 80 | |
| 81 | // error burst lies within data bits |
| 82 | if (error_index < 184) { |
| 83 | //printf("error < bit 184,%d\n",error_index); |
| 84 | j = error_index; |
| 85 | while ( j < (error_index+12) ) { |
| 86 | if (j < 184) { |
| 87 | control_data[j] = control_data[j] ^ |
| 88 | ctx->syndrome_reg[REM(ctx->syn_start+39-j+syn_index,40)]; |
| 89 | } |
| 90 | else break; |
| 91 | j = j + 1; |
| 92 | } |
| 93 | } |
| 94 | else if ( error_index > 212 ) { |
| 95 | //printf("error > bit 212,%d\n",error_index); |
| 96 | j = 0; |
| 97 | while ( j < (error_index - 212) ) { |
| 98 | control_data[j] = control_data[j] ^ |
| 99 | ctx->syndrome_reg[REM(ctx->syn_start+39-j-224+syn_index,40)]; |
| 100 | j = j + 1; |
| 101 | } |
| 102 | } |
| 103 | // for 183 < error_index < 213 error in parity alone so ignore |
| 104 | success_flag = 1; |
| 105 | } |
| 106 | return success_flag; |
| 107 | } |
| 108 | |
| 109 | static int |
| 110 | FC_syndrome_shift(FC_CTX *ctx, unsigned int bit) |
| 111 | { |
| 112 | int error_count = 0; |
| 113 | unsigned int i; |
| 114 | |
| 115 | if (ctx->syn_start == 0) |
| 116 | ctx->syn_start = 39; |
| 117 | else ctx->syn_start -= 1; |
| 118 | |
| 119 | int temp_syndrome_reg[sizeof ctx->syndrome_reg]; |
| 120 | |
| 121 | memcpy(temp_syndrome_reg, ctx->syndrome_reg, sizeof temp_syndrome_reg); |
| 122 | |
| 123 | temp_syndrome_reg[REM(ctx->syn_start+3,40)] = |
| 124 | ctx->syndrome_reg[REM(ctx->syn_start+3,40)] ^ |
| 125 | ctx->syndrome_reg[ctx->syn_start]; |
| 126 | temp_syndrome_reg[REM(ctx->syn_start+17,40)] = |
| 127 | ctx->syndrome_reg[REM(ctx->syn_start+17,40)] ^ |
| 128 | ctx->syndrome_reg[ctx->syn_start]; |
| 129 | temp_syndrome_reg[REM(ctx->syn_start+23,40)] = |
| 130 | ctx->syndrome_reg[REM(ctx->syn_start+23,40)] ^ |
| 131 | ctx->syndrome_reg[ctx->syn_start]; |
| 132 | temp_syndrome_reg[REM(ctx->syn_start+26,40)] = |
| 133 | ctx->syndrome_reg[REM(ctx->syn_start+26,40)] ^ |
| 134 | ctx->syndrome_reg[ctx->syn_start]; |
| 135 | |
| 136 | temp_syndrome_reg[REM(ctx->syn_start+4,40)] = |
| 137 | ctx->syndrome_reg[REM(ctx->syn_start+4,40)] ^ bit; |
| 138 | temp_syndrome_reg[REM(ctx->syn_start+6,40)] = |
| 139 | ctx->syndrome_reg[REM(ctx->syn_start+6,40)] ^ bit; |
| 140 | temp_syndrome_reg[REM(ctx->syn_start+10,40)] = |
| 141 | ctx->syndrome_reg[REM(ctx->syn_start+10,40)] ^ bit; |
| 142 | temp_syndrome_reg[REM(ctx->syn_start+16,40)] = |
| 143 | ctx->syndrome_reg[REM(ctx->syn_start+16,40)] ^ bit; |
| 144 | temp_syndrome_reg[REM(ctx->syn_start+27,40)] = |
| 145 | ctx->syndrome_reg[REM(ctx->syn_start+27,40)] ^ bit; |
| 146 | temp_syndrome_reg[REM(ctx->syn_start+29,40)] = |
| 147 | ctx->syndrome_reg[REM(ctx->syn_start+29,40)] ^ bit; |
| 148 | temp_syndrome_reg[REM(ctx->syn_start+33,40)] = |
| 149 | ctx->syndrome_reg[REM(ctx->syn_start+33,40)] ^ bit; |
| 150 | temp_syndrome_reg[REM(ctx->syn_start+39,40)] = |
| 151 | ctx->syndrome_reg[REM(ctx->syn_start+39,40)] ^ bit; |
| 152 | |
| 153 | temp_syndrome_reg[ctx->syn_start] = ctx->syndrome_reg[ctx->syn_start] ^ bit; |
| 154 | |
| 155 | memcpy(ctx->syndrome_reg, temp_syndrome_reg, sizeof ctx->syndrome_reg); |
| 156 | |
| 157 | for (i = 0; i < 28; i++) { |
| 158 | error_count = error_count + ctx->syndrome_reg[REM(ctx->syn_start+i,40)]; |
| 159 | } |
| 160 | return error_count; |
| 161 | } |
| 162 | |
| 163 | |