_ Git - shamirs/blob - main.c

   1 #define _GNU_SOURCE
   2
   3 #include <stdio.h>
   4 #include <stdbool.h>
   5 #include <assert.h>
   6 #include <string.h>
   7 #include <sys/mman.h>
   8 #include <unistd.h>
   9 #include <stdlib.h>
  10
  11 #include "shamirssecret.h"
  12
  13 #define MAX_LENGTH 1024
  14 #define ERROREXIT(str...) {fprintf(stderr, str); exit(1);}
  15
  16 #ifndef TEST
  17 static void derive_missing_part(uint8_t total_shares, uint8_t shares_required, bool parts_have[], uint8_t* split_version, uint8_t split_index, uint8_t split_size) {
  18         uint8_t (*D)[split_size] = (uint8_t (*)[split_size])split_version;
  19         uint8_t x[shares_required], q[shares_required];
  20
  21         // Fill in x/q with the selected shares
  22         uint16_t x_pos = 0;
  23         for (uint8_t i = 0; i < P-1; i++) {
  24                 if (parts_have[i]) {
  25                         x[x_pos] = i+1;
  26                         q[x_pos++] = D[i][split_index];
  27                 }
  28         }
  29         assert(x_pos == shares_required - 1);
  30
  31         // Now loop through ALL x we didn't already set (despite not having that many
  32         // shares, because more shares could be added arbitrarily, any x should not be
  33         // able to rule out any possible secrets) and try each possible q, making sure
  34         // that each q gives us a new possibility for the secret.
  35         bool impossible_secrets[P];
  36         memset(impossible_secrets, 0, sizeof(impossible_secrets));
  37         for (uint16_t final_x = 1; final_x < P; final_x++) {
  38                 bool x_already_used = false;
  39                 for (uint8_t j = 0; j < shares_required; j++) {
  40                         if (x[j] == final_x)
  41                                 x_already_used = true;
  42                 }
  43                 if (x_already_used)
  44                         continue;
  45
  46                 x[shares_required-1] = final_x;
  47                 bool possible_secrets[P];
  48                 memset(possible_secrets, 0, sizeof(possible_secrets));
  49                 for (uint16_t new_q = 0; new_q < P; new_q++) {
  50                         q[shares_required-1] = new_q;
  51                         possible_secrets[calculateSecret(x, q, shares_required)] = 1;
  52                 }
  53
  54                 for (uint16_t i = 0; i < P; i++)
  55                         assert(possible_secrets[i]);
  56         }
  57
  58         //TODO: Check that gcc isn't optimizing this one away
  59         memset(q, 0, sizeof(q));
  60 }
  61
  62 static void check_possible_missing_part_derivations_intern(uint8_t total_shares, uint8_t shares_required, bool parts_have[], uint8_t parts_included, uint16_t progress, uint8_t* split_version, uint8_t split_index, uint8_t split_size) {
  63         if (parts_included == shares_required-1)
  64                 return derive_missing_part(total_shares, shares_required, parts_have, split_version, split_index, split_size);
  65
  66         if (total_shares - progress < shares_required)
  67                 return;
  68
  69         check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, parts_included, progress+1, split_version, split_index, split_size);
  70         parts_have[progress] = 1;
  71         check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, parts_included+1, progress+1, split_version, split_index, split_size);
  72         parts_have[progress] = 0;
  73 }
  74
  75 static void check_possible_missing_part_derivations(uint8_t total_shares, uint8_t shares_required, uint8_t* split_version, uint8_t split_index, uint8_t split_size) {
  76         bool parts_have[P];
  77         memset(parts_have, 0, sizeof(parts_have));
  78         check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, 0, 0, split_version, split_index, split_size);
  79 }
  80
  81
  82 int main(int argc, char* argv[]) {
  83         assert(mlockall(MCL_CURRENT | MCL_FUTURE) == 0);
  84
  85         char split = 0;
  86         uint8_t total_shares = 0, shares_required = 0;
  87         char* files[P]; uint8_t files_count = 0;
  88         char *in_file = (void*)0, *out_file_param = (void*)0;
  89
  90         int i;
  91         while((i = getopt(argc, argv, "scn:k:f:o:i:h?")) != -1)
  92                 switch(i) {
  93                 case 's':
  94                         if ((split & 0x2) && !(split & 0x1))
  95                                 ERROREXIT("-s (split) and -c (combine) are mutually exclusive\n")
  96                         else
  97                                 split = (0x2 | 0x1);
  98                         break;
  99                 case 'c':
 100                         if ((split & 0x2) && (split & 0x1))
 101                                 ERROREXIT("-s (split) and -c (combine) are mutually exclusive\n")
 102                         else
 103                                 split = 0x2;
 104                         break;
 105                 case 'n': {
 106                         int t = atoi(optarg);
 107                         if (t <= 0 || t >= P)
 108                                 ERROREXIT("n must be > 0 and < %u\n", P)
 109                         else
 110                                 total_shares = t;
 111                         break;
 112                 }
 113                 case 'k': {
 114                         int t = atoi(optarg);
 115                         if (t <= 0 || t >= P)
 116                                 ERROREXIT("n must be > 0 and < %u\n", P)
 117                         else
 118                                 shares_required = t;
 119                         break;
 120                 }
 121                 case 'i':
 122                         in_file = optarg;
 123                         break;
 124                 case 'o':
 125                         out_file_param = optarg;
 126                         break;
 127                 case 'f':
 128                         if (files_count >= P-1)
 129                                 ERROREXIT("May only specify up to %u files\n", P-1)
 130                         files[files_count++] = optarg;
 131                         break;
 132                 case 'h':
 133                 case '?':
 134                         printf("Split usage: -s -n <total shares> -k <shares required> -i <input file> -o <output file path base>\n");
 135                         printf("Combine usage: -c -k <shares provided == shares required> <-f <share>>*k -o <output file>\n");
 136                         exit(0);
 137                         break;
 138                 default:
 139                         ERROREXIT("getopt failed?\n")
 140                 }
 141         if (!(split & 0x2))
 142                 ERROREXIT("Must specify one of -c, -s or -?\n")
 143         split &= 0x1;
 144
 145         if (argc != optind)
 146                 ERROREXIT("Invalid argument\n")
 147
 148         if (split) {
 149                 if (!total_shares || !shares_required)
 150                         ERROREXIT("n and k must be set.\n")
 151
 152                 if (shares_required > total_shares)
 153                         ERROREXIT("k must be <= n\n")
 154
 155                 if (files_count != 0 || !in_file || !out_file_param)
 156                         ERROREXIT("Must specify -i <input file> and -o <output file path base> but not -f in split mode.\n")
 157
 158                 FILE* random = fopen("/dev/random", "r");
 159                 assert(random);
 160                 FILE* secret_file = fopen(in_file, "r");
 161                 if (!secret_file)
 162                         ERROREXIT("Could not open %s for reading.\n", in_file)
 163
 164                 uint8_t secret[MAX_LENGTH];
 165
 166                 size_t secret_length = fread(secret, 1, MAX_LENGTH*sizeof(uint8_t), secret_file);
 167                 if (secret_length == 0)
 168                         ERROREXIT("Error reading secret\n")
 169                 if (fread(secret, 1, 1, secret_file) > 0)
 170                         ERROREXIT("Secret may not be longer than %u\n", MAX_LENGTH)
 171                 fclose(secret_file);
 172                 printf("Using secret of length %lu\n", secret_length);
 173
 174                 uint8_t a[shares_required], D[total_shares][secret_length];
 175
 176                 for (uint32_t i = 0; i < secret_length; i++) {
 177                         a[0] = secret[i];
 178
 179                         for (uint8_t j = 1; j < shares_required; j++)
 180                                 assert(fread(&a[j], sizeof(uint8_t), 1, random) == 1);
 181                         for (uint8_t j = 0; j < total_shares; j++)
 182                                 D[j][i] = calculateQ(a, shares_required, j+1);
 183
 184                         // Now, for paranoia's sake, we ensure that no matter which piece we are missing, we can derive no information about the secret
 185                         check_possible_missing_part_derivations(total_shares, shares_required, &(D[0][0]), i, secret_length);
 186
 187                         if (i % 32 == 0 && i != 0)
 188                                 printf("Finished processing %u bytes.\n", i);
 189                 }
 190
 191                 char out_file_name_buf[strlen(out_file_param) + 4];
 192                 strcpy(out_file_name_buf, out_file_param);
 193                 for (uint8_t i = 0; i < total_shares; i++) {
 194                         /*printf("%u-", i);
 195                         for (uint8_t j = 0; j < secret_length; j++)
 196                                 printf("%02x", D[i][j]);
 197                         printf("\n");*/
 198
 199                         sprintf(((char*)out_file_name_buf) + strlen(out_file_param), "%u", i);
 200                         FILE* out_file = fopen(out_file_name_buf, "w+");
 201                         if (!out_file)
 202                                 ERROREXIT("Could not open output file %s\n", out_file_name_buf)
 203
 204                         uint8_t x = i+1;
 205                         if (fwrite(&x, sizeof(uint8_t), 1, out_file) != 1)
 206                                 ERROREXIT("Could not write 1 byte to %s\n", out_file_name_buf)
 207
 208                         if (fwrite(D[i], 1, secret_length, out_file) != secret_length)
 209                                 ERROREXIT("Could not write %lu bytes to %s\n", secret_length, out_file_name_buf)
 210
 211                         fclose(out_file);
 212                 }
 213                 /*printf("secret = ");
 214                 for (uint8_t i = 0; i < secret_length; i++)
 215                         printf("%02x", secret[i]);
 216                 printf("\n");*/
 217
 218                 // Clear sensitive data (No, GCC 4.7.2 is currently not optimizing this out)
 219                 memset(secret, 0, sizeof(uint8_t)*secret_length);
 220                 memset(a, 0, sizeof(uint8_t)*shares_required);
 221                 memset(in_file, 0, strlen(in_file));
 222
 223                 fclose(random);
 224         } else {
 225                 if (!shares_required)
 226                         ERROREXIT("k must be set.\n")
 227
 228                 if (files_count != shares_required || in_file || !out_file_param)
 229                         ERROREXIT("Must not specify -i and must specify -o and exactly k -f <input file>s in combine mode.\n")
 230
 231                 uint8_t x[shares_required], q[shares_required];
 232                 FILE* files_fps[shares_required];
 233
 234                 for (uint8_t i = 0; i < shares_required; i++) {
 235                         files_fps[i] = fopen(files[i], "r");
 236                         if (!files_fps[i])
 237                                 ERROREXIT("Couldn't open file %s for reading.\n", files[i])
 238                         if (fread(&x[i], sizeof(uint8_t), 1, files_fps[i]) != 1)
 239                                 ERROREXIT("Couldn't read the x byte of %s\n", files[i])
 240                 }
 241
 242                 uint8_t secret[MAX_LENGTH];
 243
 244                 uint32_t i = 0;
 245                 while (fread(&q[0], sizeof(uint8_t), 1, files_fps[0]) == 1) {
 246                         for (uint8_t j = 1; j < shares_required; j++) {
 247                                 if (fread(&q[j], sizeof(uint8_t), 1, files_fps[j]) != 1)
 248                                         ERROREXIT("Couldn't read next byte from %s\n", files[j])
 249                         }
 250                         secret[i++] = calculateSecret(x, q, shares_required);
 251                 }
 252                 printf("Got secret of length %u\n", i);
 253
 254                 FILE* out_file = fopen(out_file_param, "w+");
 255                 fwrite(secret, sizeof(uint8_t), i, out_file);
 256                 fclose(out_file);
 257
 258                 for (uint8_t i = 0; i < shares_required; i++)
 259                         fclose(files_fps[i]);
 260
 261                 // Clear sensitive data (No, GCC 4.7.2 is currently not optimizing this out)
 262                 memset(secret, 0, sizeof(uint8_t)*i);
 263                 memset(q, 0, sizeof(uint8_t)*shares_required);
 264                 memset(out_file_param, 0, strlen(out_file_param));
 265                 for (uint8_t i = 0; i < shares_required; i++)
 266                         memset(files[i], 0, strlen(files[i]));
 267                 memset(x, 0, sizeof(uint8_t)*shares_required);
 268         }
 269
 270         return 0;
 271 }
 272 #endif // !defined(TEST)