| 1 | /* crapto1.c\r |
| 2 | \r |
| 3 | This program is free software; you can redistribute it and/or\r |
| 4 | modify it under the terms of the GNU General Public License\r |
| 5 | as published by the Free Software Foundation; either version 2\r |
| 6 | of the License, or (at your option) any later version.\r |
| 7 | \r |
| 8 | This program is distributed in the hope that it will be useful,\r |
| 9 | but WITHOUT ANY WARRANTY; without even the implied warranty of\r |
| 10 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the\r |
| 11 | GNU General Public License for more details.\r |
| 12 | \r |
| 13 | You should have received a copy of the GNU General Public License\r |
| 14 | along with this program; if not, write to the Free Software\r |
| 15 | Foundation, Inc., 51 Franklin Street, Fifth Floor,\r |
| 16 | Boston, MA 02110-1301, US$\r |
| 17 | \r |
| 18 | Copyright (C) 2008-2014 bla <blapost@gmail.com>\r |
| 19 | */\r |
| 20 | #include "crapto1.h"\r |
| 21 | #include <stdlib.h>\r |
| 22 | \r |
| 23 | #if !defined LOWMEM && defined __GNUC__\r |
| 24 | static uint8_t filterlut[1 << 20];\r |
| 25 | static void __attribute__((constructor)) fill_lut()\r |
| 26 | {\r |
| 27 | uint32_t i;\r |
| 28 | for(i = 0; i < 1 << 20; ++i)\r |
| 29 | filterlut[i] = filter(i);\r |
| 30 | }\r |
| 31 | #define filter(x) (filterlut[(x) & 0xfffff])\r |
| 32 | #endif\r |
| 33 | \r |
| 34 | \r |
| 35 | \r |
| 36 | typedef struct bucket {\r |
| 37 | uint32_t *head;\r |
| 38 | uint32_t *bp;\r |
| 39 | } bucket_t;\r |
| 40 | \r |
| 41 | typedef bucket_t bucket_array_t[2][0x100];\r |
| 42 | \r |
| 43 | typedef struct bucket_info {\r |
| 44 | struct {\r |
| 45 | uint32_t *head, *tail;\r |
| 46 | } bucket_info[2][0x100];\r |
| 47 | uint32_t numbuckets;\r |
| 48 | } bucket_info_t;\r |
| 49 | \r |
| 50 | \r |
| 51 | static void bucket_sort_intersect(uint32_t* const estart, uint32_t* const estop,\r |
| 52 | uint32_t* const ostart, uint32_t* const ostop,\r |
| 53 | bucket_info_t *bucket_info, bucket_array_t bucket)\r |
| 54 | {\r |
| 55 | uint32_t *p1, *p2;\r |
| 56 | uint32_t *start[2];\r |
| 57 | uint32_t *stop[2];\r |
| 58 | \r |
| 59 | start[0] = estart;\r |
| 60 | stop[0] = estop;\r |
| 61 | start[1] = ostart;\r |
| 62 | stop[1] = ostop;\r |
| 63 | \r |
| 64 | // init buckets to be empty\r |
| 65 | for (uint32_t i = 0; i < 2; i++) {\r |
| 66 | for (uint32_t j = 0x00; j <= 0xff; j++) {\r |
| 67 | bucket[i][j].bp = bucket[i][j].head;\r |
| 68 | }\r |
| 69 | }\r |
| 70 | \r |
| 71 | // sort the lists into the buckets based on the MSB (contribution bits)\r |
| 72 | for (uint32_t i = 0; i < 2; i++) {\r |
| 73 | for (p1 = start[i]; p1 <= stop[i]; p1++) {\r |
| 74 | uint32_t bucket_index = (*p1 & 0xff000000) >> 24;\r |
| 75 | *(bucket[i][bucket_index].bp++) = *p1;\r |
| 76 | }\r |
| 77 | }\r |
| 78 | \r |
| 79 | \r |
| 80 | // write back intersecting buckets as sorted list.\r |
| 81 | // fill in bucket_info with head and tail of the bucket contents in the list and number of non-empty buckets.\r |
| 82 | uint32_t nonempty_bucket;\r |
| 83 | for (uint32_t i = 0; i < 2; i++) {\r |
| 84 | p1 = start[i];\r |
| 85 | nonempty_bucket = 0;\r |
| 86 | for (uint32_t j = 0x00; j <= 0xff; j++) {\r |
| 87 | if (bucket[0][j].bp != bucket[0][j].head && bucket[1][j].bp != bucket[1][j].head) { // non-empty intersecting buckets only\r |
| 88 | bucket_info->bucket_info[i][nonempty_bucket].head = p1;\r |
| 89 | for (p2 = bucket[i][j].head; p2 < bucket[i][j].bp; *p1++ = *p2++);\r |
| 90 | bucket_info->bucket_info[i][nonempty_bucket].tail = p1 - 1;\r |
| 91 | nonempty_bucket++;\r |
| 92 | }\r |
| 93 | }\r |
| 94 | bucket_info->numbuckets = nonempty_bucket;\r |
| 95 | }\r |
| 96 | }\r |
| 97 | \r |
| 98 | /** update_contribution\r |
| 99 | * helper, calculates the partial linear feedback contributions and puts in MSB\r |
| 100 | */\r |
| 101 | static inline void update_contribution(uint32_t *item, const uint32_t mask1, const uint32_t mask2)\r |
| 102 | {\r |
| 103 | uint32_t p = *item >> 25;\r |
| 104 | \r |
| 105 | p = p << 1 | parity(*item & mask1);\r |
| 106 | p = p << 1 | parity(*item & mask2);\r |
| 107 | *item = p << 24 | (*item & 0xffffff);\r |
| 108 | }\r |
| 109 | \r |
| 110 | /** extend_table\r |
| 111 | * using a bit of the keystream extend the table of possible lfsr states\r |
| 112 | */\r |
| 113 | static inline void extend_table(uint32_t *tbl, uint32_t **end, int bit, int m1, int m2, uint32_t in)\r |
| 114 | {\r |
| 115 | in <<= 24;\r |
| 116 | for(*tbl <<= 1; tbl <= *end; *++tbl <<= 1)\r |
| 117 | if(filter(*tbl) ^ filter(*tbl | 1)) {\r |
| 118 | *tbl |= filter(*tbl) ^ bit;\r |
| 119 | update_contribution(tbl, m1, m2);\r |
| 120 | *tbl ^= in;\r |
| 121 | } else if(filter(*tbl) == bit) {\r |
| 122 | *++*end = tbl[1];\r |
| 123 | tbl[1] = tbl[0] | 1;\r |
| 124 | update_contribution(tbl, m1, m2);\r |
| 125 | *tbl++ ^= in;\r |
| 126 | update_contribution(tbl, m1, m2);\r |
| 127 | *tbl ^= in;\r |
| 128 | } else\r |
| 129 | *tbl-- = *(*end)--;\r |
| 130 | }\r |
| 131 | /** extend_table_simple\r |
| 132 | * using a bit of the keystream extend the table of possible lfsr states\r |
| 133 | */\r |
| 134 | static inline void extend_table_simple(uint32_t *tbl, uint32_t **end, int bit)\r |
| 135 | {\r |
| 136 | for(*tbl <<= 1; tbl <= *end; *++tbl <<= 1) {\r |
| 137 | if(filter(*tbl) ^ filter(*tbl | 1)) { // replace\r |
| 138 | *tbl |= filter(*tbl) ^ bit;\r |
| 139 | } else if(filter(*tbl) == bit) { // insert\r |
| 140 | *++*end = *++tbl;\r |
| 141 | *tbl = tbl[-1] | 1;\r |
| 142 | } else { // drop\r |
| 143 | *tbl-- = *(*end)--;\r |
| 144 | }\r |
| 145 | }\r |
| 146 | }\r |
| 147 | /** recover\r |
| 148 | * recursively narrow down the search space, 4 bits of keystream at a time\r |
| 149 | */\r |
| 150 | static struct Crypto1State*\r |
| 151 | recover(uint32_t *o_head, uint32_t *o_tail, uint32_t oks,\r |
| 152 | uint32_t *e_head, uint32_t *e_tail, uint32_t eks, int rem,\r |
| 153 | struct Crypto1State *sl, uint32_t in, bucket_array_t bucket)\r |
| 154 | {\r |
| 155 | uint32_t *o, *e;\r |
| 156 | bucket_info_t bucket_info;\r |
| 157 | \r |
| 158 | if(rem == -1) {\r |
| 159 | for(e = e_head; e <= e_tail; ++e) {\r |
| 160 | *e = *e << 1 ^ parity(*e & LF_POLY_EVEN) ^ !!(in & 4);\r |
| 161 | for(o = o_head; o <= o_tail; ++o, ++sl) {\r |
| 162 | sl->even = *o;\r |
| 163 | sl->odd = *e ^ parity(*o & LF_POLY_ODD);\r |
| 164 | sl[1].odd = sl[1].even = 0;\r |
| 165 | }\r |
| 166 | }\r |
| 167 | return sl;\r |
| 168 | }\r |
| 169 | \r |
| 170 | for(uint32_t i = 0; i < 4 && rem--; i++) {\r |
| 171 | oks >>= 1;\r |
| 172 | eks >>= 1;\r |
| 173 | in >>= 2;\r |
| 174 | extend_table(o_head, &o_tail, oks & 1, LF_POLY_EVEN << 1 | 1, LF_POLY_ODD << 1, 0);\r |
| 175 | if(o_head > o_tail)\r |
| 176 | return sl;\r |
| 177 | \r |
| 178 | extend_table(e_head, &e_tail, eks & 1, LF_POLY_ODD, LF_POLY_EVEN << 1 | 1, in & 3);\r |
| 179 | if(e_head > e_tail)\r |
| 180 | return sl;\r |
| 181 | }\r |
| 182 | \r |
| 183 | bucket_sort_intersect(e_head, e_tail, o_head, o_tail, &bucket_info, bucket);\r |
| 184 | \r |
| 185 | for (int i = bucket_info.numbuckets - 1; i >= 0; i--) {\r |
| 186 | sl = recover(bucket_info.bucket_info[1][i].head, bucket_info.bucket_info[1][i].tail, oks,\r |
| 187 | bucket_info.bucket_info[0][i].head, bucket_info.bucket_info[0][i].tail, eks,\r |
| 188 | rem, sl, in, bucket);\r |
| 189 | }\r |
| 190 | \r |
| 191 | return sl;\r |
| 192 | }\r |
| 193 | /** lfsr_recovery\r |
| 194 | * recover the state of the lfsr given 32 bits of the keystream\r |
| 195 | * additionally you can use the in parameter to specify the value\r |
| 196 | * that was fed into the lfsr at the time the keystream was generated\r |
| 197 | */\r |
| 198 | struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in)\r |
| 199 | {\r |
| 200 | struct Crypto1State *statelist;\r |
| 201 | uint32_t *odd_head = 0, *odd_tail = 0, oks = 0;\r |
| 202 | uint32_t *even_head = 0, *even_tail = 0, eks = 0;\r |
| 203 | int i;\r |
| 204 | \r |
| 205 | // split the keystream into an odd and even part\r |
| 206 | for(i = 31; i >= 0; i -= 2)\r |
| 207 | oks = oks << 1 | BEBIT(ks2, i);\r |
| 208 | for(i = 30; i >= 0; i -= 2)\r |
| 209 | eks = eks << 1 | BEBIT(ks2, i);\r |
| 210 | \r |
| 211 | odd_head = odd_tail = malloc(sizeof(uint32_t) << 21);\r |
| 212 | even_head = even_tail = malloc(sizeof(uint32_t) << 21);\r |
| 213 | statelist = malloc(sizeof(struct Crypto1State) << 18);\r |
| 214 | if(!odd_tail-- || !even_tail-- || !statelist) {\r |
| 215 | free(statelist);\r |
| 216 | statelist = 0;\r |
| 217 | goto out;\r |
| 218 | }\r |
| 219 | \r |
| 220 | statelist->odd = statelist->even = 0;\r |
| 221 | \r |
| 222 | // allocate memory for out of place bucket_sort\r |
| 223 | bucket_array_t bucket;\r |
| 224 | \r |
| 225 | for (uint32_t i = 0; i < 2; i++) {\r |
| 226 | for (uint32_t j = 0; j <= 0xff; j++) {\r |
| 227 | bucket[i][j].head = malloc(sizeof(uint32_t)<<14);\r |
| 228 | if (!bucket[i][j].head) {\r |
| 229 | goto out;\r |
| 230 | }\r |
| 231 | }\r |
| 232 | }\r |
| 233 | \r |
| 234 | // initialize statelists: add all possible states which would result into the rightmost 2 bits of the keystream\r |
| 235 | for(i = 1 << 20; i >= 0; --i) {\r |
| 236 | if(filter(i) == (oks & 1))\r |
| 237 | *++odd_tail = i;\r |
| 238 | if(filter(i) == (eks & 1))\r |
| 239 | *++even_tail = i;\r |
| 240 | }\r |
| 241 | \r |
| 242 | // extend the statelists. Look at the next 8 Bits of the keystream (4 Bit each odd and even):\r |
| 243 | for(i = 0; i < 4; i++) {\r |
| 244 | extend_table_simple(odd_head, &odd_tail, (oks >>= 1) & 1);\r |
| 245 | extend_table_simple(even_head, &even_tail, (eks >>= 1) & 1);\r |
| 246 | }\r |
| 247 | \r |
| 248 | // the statelists now contain all states which could have generated the last 10 Bits of the keystream.\r |
| 249 | // 22 bits to go to recover 32 bits in total. From now on, we need to take the "in"\r |
| 250 | // parameter into account.\r |
| 251 | in = (in >> 16 & 0xff) | (in << 16) | (in & 0xff00); // Byte swapping\r |
| 252 | recover(odd_head, odd_tail, oks, even_head, even_tail, eks, 11, statelist, in << 1, bucket);\r |
| 253 | \r |
| 254 | out:\r |
| 255 | for (uint32_t i = 0; i < 2; i++)\r |
| 256 | for (uint32_t j = 0; j <= 0xff; j++)\r |
| 257 | free(bucket[i][j].head);\r |
| 258 | free(odd_head);\r |
| 259 | free(even_head);\r |
| 260 | return statelist;\r |
| 261 | }\r |
| 262 | \r |
| 263 | static const uint32_t S1[] = { 0x62141, 0x310A0, 0x18850, 0x0C428, 0x06214,\r |
| 264 | 0x0310A, 0x85E30, 0xC69AD, 0x634D6, 0xB5CDE, 0xDE8DA, 0x6F46D, 0xB3C83,\r |
| 265 | 0x59E41, 0xA8995, 0xD027F, 0x6813F, 0x3409F, 0x9E6FA};\r |
| 266 | static const uint32_t S2[] = { 0x3A557B00, 0x5D2ABD80, 0x2E955EC0, 0x174AAF60,\r |
| 267 | 0x0BA557B0, 0x05D2ABD8, 0x0449DE68, 0x048464B0, 0x42423258, 0x278192A8,\r |
| 268 | 0x156042D0, 0x0AB02168, 0x43F89B30, 0x61FC4D98, 0x765EAD48, 0x7D8FDD20,\r |
| 269 | 0x7EC7EE90, 0x7F63F748, 0x79117020};\r |
| 270 | static const uint32_t T1[] = {\r |
| 271 | 0x4F37D, 0x279BE, 0x97A6A, 0x4BD35, 0x25E9A, 0x12F4D, 0x097A6, 0x80D66,\r |
| 272 | 0xC4006, 0x62003, 0xB56B4, 0x5AB5A, 0xA9318, 0xD0F39, 0x6879C, 0xB057B,\r |
| 273 | 0x582BD, 0x2C15E, 0x160AF, 0x8F6E2, 0xC3DC4, 0xE5857, 0x72C2B, 0x39615,\r |
| 274 | 0x98DBF, 0xC806A, 0xE0680, 0x70340, 0x381A0, 0x98665, 0x4C332, 0xA272C};\r |
| 275 | static const uint32_t T2[] = { 0x3C88B810, 0x5E445C08, 0x2982A580, 0x14C152C0,\r |
| 276 | 0x4A60A960, 0x253054B0, 0x52982A58, 0x2FEC9EA8, 0x1156C4D0, 0x08AB6268,\r |
| 277 | 0x42F53AB0, 0x217A9D58, 0x161DC528, 0x0DAE6910, 0x46D73488, 0x25CB11C0,\r |
| 278 | 0x52E588E0, 0x6972C470, 0x34B96238, 0x5CFC3A98, 0x28DE96C8, 0x12CFC0E0,\r |
| 279 | 0x4967E070, 0x64B3F038, 0x74F97398, 0x7CDC3248, 0x38CE92A0, 0x1C674950,\r |
| 280 | 0x0E33A4A8, 0x01B959D0, 0x40DCACE8, 0x26CEDDF0};\r |
| 281 | static const uint32_t C1[] = { 0x846B5, 0x4235A, 0x211AD};\r |
| 282 | static const uint32_t C2[] = { 0x1A822E0, 0x21A822E0, 0x21A822E0};\r |
| 283 | /** Reverse 64 bits of keystream into possible cipher states\r |
| 284 | * Variation mentioned in the paper. Somewhat optimized version\r |
| 285 | */\r |
| 286 | struct Crypto1State* lfsr_recovery64(uint32_t ks2, uint32_t ks3)\r |
| 287 | {\r |
| 288 | struct Crypto1State *statelist, *sl;\r |
| 289 | uint8_t oks[32], eks[32], hi[32];\r |
| 290 | uint32_t low = 0, win = 0;\r |
| 291 | uint32_t *tail, table[1 << 16];\r |
| 292 | int i, j;\r |
| 293 | \r |
| 294 | sl = statelist = malloc(sizeof(struct Crypto1State) << 4);\r |
| 295 | if(!sl)\r |
| 296 | return 0;\r |
| 297 | sl->odd = sl->even = 0;\r |
| 298 | \r |
| 299 | for(i = 30; i >= 0; i -= 2) {\r |
| 300 | oks[i >> 1] = BEBIT(ks2, i);\r |
| 301 | oks[16 + (i >> 1)] = BEBIT(ks3, i);\r |
| 302 | }\r |
| 303 | for(i = 31; i >= 0; i -= 2) {\r |
| 304 | eks[i >> 1] = BEBIT(ks2, i);\r |
| 305 | eks[16 + (i >> 1)] = BEBIT(ks3, i);\r |
| 306 | }\r |
| 307 | \r |
| 308 | for(i = 0xfffff; i >= 0; --i) {\r |
| 309 | if (filter(i) != oks[0])\r |
| 310 | continue;\r |
| 311 | \r |
| 312 | *(tail = table) = i;\r |
| 313 | for(j = 1; tail >= table && j < 29; ++j)\r |
| 314 | extend_table_simple(table, &tail, oks[j]);\r |
| 315 | \r |
| 316 | if(tail < table)\r |
| 317 | continue;\r |
| 318 | \r |
| 319 | for(j = 0; j < 19; ++j)\r |
| 320 | low = low << 1 | parity(i & S1[j]);\r |
| 321 | for(j = 0; j < 32; ++j)\r |
| 322 | hi[j] = parity(i & T1[j]);\r |
| 323 | \r |
| 324 | for(; tail >= table; --tail) {\r |
| 325 | for(j = 0; j < 3; ++j) {\r |
| 326 | *tail = *tail << 1;\r |
| 327 | *tail |= parity((i & C1[j]) ^ (*tail & C2[j]));\r |
| 328 | if(filter(*tail) != oks[29 + j])\r |
| 329 | goto continue2;\r |
| 330 | }\r |
| 331 | \r |
| 332 | for(j = 0; j < 19; ++j)\r |
| 333 | win = win << 1 | parity(*tail & S2[j]);\r |
| 334 | \r |
| 335 | win ^= low;\r |
| 336 | for(j = 0; j < 32; ++j) {\r |
| 337 | win = win << 1 ^ hi[j] ^ parity(*tail & T2[j]);\r |
| 338 | if(filter(win) != eks[j])\r |
| 339 | goto continue2;\r |
| 340 | }\r |
| 341 | \r |
| 342 | *tail = *tail << 1 | parity(LF_POLY_EVEN & *tail);\r |
| 343 | sl->odd = *tail ^ parity(LF_POLY_ODD & win);\r |
| 344 | sl->even = win;\r |
| 345 | ++sl;\r |
| 346 | sl->odd = sl->even = 0;\r |
| 347 | continue2:;\r |
| 348 | }\r |
| 349 | }\r |
| 350 | return statelist;\r |
| 351 | }\r |
| 352 | \r |
| 353 | /** lfsr_rollback_bit\r |
| 354 | * Rollback the shift register in order to get previous states\r |
| 355 | */\r |
| 356 | uint8_t lfsr_rollback_bit(struct Crypto1State *s, uint32_t in, int fb)\r |
| 357 | {\r |
| 358 | int out;\r |
| 359 | uint8_t ret;\r |
| 360 | uint32_t t;\r |
| 361 | \r |
| 362 | s->odd &= 0xffffff;\r |
| 363 | t = s->odd, s->odd = s->even, s->even = t;\r |
| 364 | \r |
| 365 | out = s->even & 1;\r |
| 366 | out ^= LF_POLY_EVEN & (s->even >>= 1);\r |
| 367 | out ^= LF_POLY_ODD & s->odd;\r |
| 368 | out ^= !!in;\r |
| 369 | out ^= (ret = filter(s->odd)) & !!fb;\r |
| 370 | \r |
| 371 | s->even |= parity(out) << 23;\r |
| 372 | return ret;\r |
| 373 | }\r |
| 374 | /** lfsr_rollback_byte\r |
| 375 | * Rollback the shift register in order to get previous states\r |
| 376 | */\r |
| 377 | uint8_t lfsr_rollback_byte(struct Crypto1State *s, uint32_t in, int fb)\r |
| 378 | {\r |
| 379 | /*\r |
| 380 | int i, ret = 0;\r |
| 381 | for (i = 7; i >= 0; --i)\r |
| 382 | ret |= lfsr_rollback_bit(s, BIT(in, i), fb) << i;\r |
| 383 | */\r |
| 384 | // unfold loop 20160112\r |
| 385 | uint8_t ret = 0;\r |
| 386 | ret |= lfsr_rollback_bit(s, BIT(in, 7), fb) << 7;\r |
| 387 | ret |= lfsr_rollback_bit(s, BIT(in, 6), fb) << 6;\r |
| 388 | ret |= lfsr_rollback_bit(s, BIT(in, 5), fb) << 5;\r |
| 389 | ret |= lfsr_rollback_bit(s, BIT(in, 4), fb) << 4;\r |
| 390 | ret |= lfsr_rollback_bit(s, BIT(in, 3), fb) << 3;\r |
| 391 | ret |= lfsr_rollback_bit(s, BIT(in, 2), fb) << 2;\r |
| 392 | ret |= lfsr_rollback_bit(s, BIT(in, 1), fb) << 1;\r |
| 393 | ret |= lfsr_rollback_bit(s, BIT(in, 0), fb) << 0;\r |
| 394 | return ret;\r |
| 395 | }\r |
| 396 | /** lfsr_rollback_word\r |
| 397 | * Rollback the shift register in order to get previous states\r |
| 398 | */\r |
| 399 | uint32_t lfsr_rollback_word(struct Crypto1State *s, uint32_t in, int fb)\r |
| 400 | {\r |
| 401 | /*\r |
| 402 | int i;\r |
| 403 | uint32_t ret = 0;\r |
| 404 | for (i = 31; i >= 0; --i)\r |
| 405 | ret |= lfsr_rollback_bit(s, BEBIT(in, i), fb) << (i ^ 24);\r |
| 406 | */\r |
| 407 | // unfold loop 20160112\r |
| 408 | uint32_t ret = 0;\r |
| 409 | ret |= lfsr_rollback_bit(s, BEBIT(in, 31), fb) << (31 ^ 24);\r |
| 410 | ret |= lfsr_rollback_bit(s, BEBIT(in, 30), fb) << (30 ^ 24);\r |
| 411 | ret |= lfsr_rollback_bit(s, BEBIT(in, 29), fb) << (29 ^ 24);\r |
| 412 | ret |= lfsr_rollback_bit(s, BEBIT(in, 28), fb) << (28 ^ 24);\r |
| 413 | ret |= lfsr_rollback_bit(s, BEBIT(in, 27), fb) << (27 ^ 24);\r |
| 414 | ret |= lfsr_rollback_bit(s, BEBIT(in, 26), fb) << (26 ^ 24);\r |
| 415 | ret |= lfsr_rollback_bit(s, BEBIT(in, 25), fb) << (25 ^ 24);\r |
| 416 | ret |= lfsr_rollback_bit(s, BEBIT(in, 24), fb) << (24 ^ 24);\r |
| 417 | \r |
| 418 | ret |= lfsr_rollback_bit(s, BEBIT(in, 23), fb) << (23 ^ 24);\r |
| 419 | ret |= lfsr_rollback_bit(s, BEBIT(in, 22), fb) << (22 ^ 24);\r |
| 420 | ret |= lfsr_rollback_bit(s, BEBIT(in, 21), fb) << (21 ^ 24);\r |
| 421 | ret |= lfsr_rollback_bit(s, BEBIT(in, 20), fb) << (20 ^ 24);\r |
| 422 | ret |= lfsr_rollback_bit(s, BEBIT(in, 19), fb) << (19 ^ 24);\r |
| 423 | ret |= lfsr_rollback_bit(s, BEBIT(in, 18), fb) << (18 ^ 24);\r |
| 424 | ret |= lfsr_rollback_bit(s, BEBIT(in, 17), fb) << (17 ^ 24);\r |
| 425 | ret |= lfsr_rollback_bit(s, BEBIT(in, 16), fb) << (16 ^ 24);\r |
| 426 | \r |
| 427 | ret |= lfsr_rollback_bit(s, BEBIT(in, 15), fb) << (15 ^ 24);\r |
| 428 | ret |= lfsr_rollback_bit(s, BEBIT(in, 14), fb) << (14 ^ 24);\r |
| 429 | ret |= lfsr_rollback_bit(s, BEBIT(in, 13), fb) << (13 ^ 24);\r |
| 430 | ret |= lfsr_rollback_bit(s, BEBIT(in, 12), fb) << (12 ^ 24);\r |
| 431 | ret |= lfsr_rollback_bit(s, BEBIT(in, 11), fb) << (11 ^ 24);\r |
| 432 | ret |= lfsr_rollback_bit(s, BEBIT(in, 10), fb) << (10 ^ 24);\r |
| 433 | ret |= lfsr_rollback_bit(s, BEBIT(in, 9), fb) << (9 ^ 24);\r |
| 434 | ret |= lfsr_rollback_bit(s, BEBIT(in, 8), fb) << (8 ^ 24);\r |
| 435 | \r |
| 436 | ret |= lfsr_rollback_bit(s, BEBIT(in, 7), fb) << (7 ^ 24);\r |
| 437 | ret |= lfsr_rollback_bit(s, BEBIT(in, 6), fb) << (6 ^ 24);\r |
| 438 | ret |= lfsr_rollback_bit(s, BEBIT(in, 5), fb) << (5 ^ 24);\r |
| 439 | ret |= lfsr_rollback_bit(s, BEBIT(in, 4), fb) << (4 ^ 24);\r |
| 440 | ret |= lfsr_rollback_bit(s, BEBIT(in, 3), fb) << (3 ^ 24);\r |
| 441 | ret |= lfsr_rollback_bit(s, BEBIT(in, 2), fb) << (2 ^ 24);\r |
| 442 | ret |= lfsr_rollback_bit(s, BEBIT(in, 1), fb) << (1 ^ 24);\r |
| 443 | ret |= lfsr_rollback_bit(s, BEBIT(in, 0), fb) << (0 ^ 24);\r |
| 444 | return ret;\r |
| 445 | }\r |
| 446 | \r |
| 447 | /** nonce_distance\r |
| 448 | * x,y valid tag nonces, then prng_successor(x, nonce_distance(x, y)) = y\r |
| 449 | */\r |
| 450 | static uint16_t *dist = 0;\r |
| 451 | int nonce_distance(uint32_t from, uint32_t to)\r |
| 452 | {\r |
| 453 | uint16_t x, i;\r |
| 454 | if(!dist) {\r |
| 455 | dist = malloc(2 << 16);\r |
| 456 | if(!dist)\r |
| 457 | return -1;\r |
| 458 | for (x = i = 1; i; ++i) {\r |
| 459 | dist[(x & 0xff) << 8 | x >> 8] = i;\r |
| 460 | x = x >> 1 | (x ^ x >> 2 ^ x >> 3 ^ x >> 5) << 15;\r |
| 461 | }\r |
| 462 | }\r |
| 463 | return (65535 + dist[to >> 16] - dist[from >> 16]) % 65535;\r |
| 464 | }\r |
| 465 | \r |
| 466 | \r |
| 467 | static uint32_t fastfwd[2][8] = {\r |
| 468 | { 0, 0x4BC53, 0xECB1, 0x450E2, 0x25E29, 0x6E27A, 0x2B298, 0x60ECB},\r |
| 469 | { 0, 0x1D962, 0x4BC53, 0x56531, 0xECB1, 0x135D3, 0x450E2, 0x58980}};\r |
| 470 | \r |
| 471 | \r |
| 472 | /** lfsr_prefix_ks\r |
| 473 | *\r |
| 474 | * Is an exported helper function from the common prefix attack\r |
| 475 | * Described in the "dark side" paper. It returns an -1 terminated array\r |
| 476 | * of possible partial(21 bit) secret state.\r |
| 477 | * The required keystream(ks) needs to contain the keystream that was used to\r |
| 478 | * encrypt the NACK which is observed when varying only the 3 last bits of Nr\r |
| 479 | * only correct iff [NR_3] ^ NR_3 does not depend on Nr_3\r |
| 480 | */\r |
| 481 | uint32_t *lfsr_prefix_ks(uint8_t ks[8], int isodd)\r |
| 482 | {\r |
| 483 | uint32_t *candidates = malloc(4 << 10);\r |
| 484 | if(!candidates) return 0;\r |
| 485 | \r |
| 486 | uint32_t c, entry;\r |
| 487 | int size = 0, i, good;\r |
| 488 | \r |
| 489 | for(i = 0; i < 1 << 21; ++i) {\r |
| 490 | for(c = 0, good = 1; good && c < 8; ++c) {\r |
| 491 | entry = i ^ fastfwd[isodd][c];\r |
| 492 | good &= (BIT(ks[c], isodd) == filter(entry >> 1));\r |
| 493 | good &= (BIT(ks[c], isodd + 2) == filter(entry));\r |
| 494 | }\r |
| 495 | if(good)\r |
| 496 | candidates[size++] = i;\r |
| 497 | }\r |
| 498 | \r |
| 499 | candidates[size] = -1;\r |
| 500 | \r |
| 501 | return candidates;\r |
| 502 | }\r |
| 503 | \r |
| 504 | /** check_pfx_parity\r |
| 505 | * helper function which eliminates possible secret states using parity bits\r |
| 506 | */\r |
| 507 | static struct Crypto1State* check_pfx_parity(uint32_t prefix, uint32_t rresp, uint8_t parities[8][8], uint32_t odd, uint32_t even, struct Crypto1State* sl)\r |
| 508 | {\r |
| 509 | uint32_t ks1, nr, ks2, rr, ks3, c, good = 1;\r |
| 510 | \r |
| 511 | for(c = 0; good && c < 8; ++c) {\r |
| 512 | sl->odd = odd ^ fastfwd[1][c];\r |
| 513 | sl->even = even ^ fastfwd[0][c];\r |
| 514 | \r |
| 515 | lfsr_rollback_bit(sl, 0, 0);\r |
| 516 | lfsr_rollback_bit(sl, 0, 0);\r |
| 517 | \r |
| 518 | ks3 = lfsr_rollback_bit(sl, 0, 0);\r |
| 519 | ks2 = lfsr_rollback_word(sl, 0, 0);\r |
| 520 | ks1 = lfsr_rollback_word(sl, prefix | c << 5, 1);\r |
| 521 | \r |
| 522 | nr = ks1 ^ (prefix | c << 5);\r |
| 523 | rr = ks2 ^ rresp;\r |
| 524 | \r |
| 525 | good &= parity(nr & 0x000000ff) ^ parities[c][3] ^ BIT(ks2, 24);\r |
| 526 | good &= parity(rr & 0xff000000) ^ parities[c][4] ^ BIT(ks2, 16);\r |
| 527 | good &= parity(rr & 0x00ff0000) ^ parities[c][5] ^ BIT(ks2, 8);\r |
| 528 | good &= parity(rr & 0x0000ff00) ^ parities[c][6] ^ BIT(ks2, 0);\r |
| 529 | good &= parity(rr & 0x000000ff) ^ parities[c][7] ^ ks3;\r |
| 530 | }\r |
| 531 | \r |
| 532 | return sl + good;\r |
| 533 | } \r |
| 534 | \r |
| 535 | /** lfsr_common_prefix\r |
| 536 | * Implentation of the common prefix attack.\r |
| 537 | * Requires the 28 bit constant prefix used as reader nonce (pfx)\r |
| 538 | * The reader response used (rr)\r |
| 539 | * The keystream used to encrypt the observed NACK's (ks)\r |
| 540 | * The parity bits (par)\r |
| 541 | * It returns a zero terminated list of possible cipher states after the\r |
| 542 | * tag nonce was fed in\r |
| 543 | */\r |
| 544 | \r |
| 545 | struct Crypto1State* lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8])\r |
| 546 | {\r |
| 547 | struct Crypto1State *statelist, *s;\r |
| 548 | uint32_t *odd, *even, *o, *e, top;\r |
| 549 | \r |
| 550 | odd = lfsr_prefix_ks(ks, 1);\r |
| 551 | even = lfsr_prefix_ks(ks, 0);\r |
| 552 | \r |
| 553 | s = statelist = malloc((sizeof *statelist) << 20);\r |
| 554 | if(!s || !odd || !even) {\r |
| 555 | free(statelist);\r |
| 556 | statelist = 0;\r |
| 557 | goto out;\r |
| 558 | }\r |
| 559 | \r |
| 560 | for(o = odd; *o + 1; ++o)\r |
| 561 | for(e = even; *e + 1; ++e)\r |
| 562 | for(top = 0; top < 64; ++top) {\r |
| 563 | *o += 1 << 21;\r |
| 564 | *e += (!(top & 7) + 1) << 21;\r |
| 565 | s = check_pfx_parity(pfx, rr, par, *o, *e, s);\r |
| 566 | }\r |
| 567 | \r |
| 568 | s->odd = s->even = 0;\r |
| 569 | out:\r |
| 570 | free(odd);\r |
| 571 | free(even);\r |
| 572 | return statelist;\r |
| 573 | }\r |