| 1 | /* |
| 2 | * random.c: Internal random number generator, guaranteed to work |
| 3 | * the same way on all platforms. Used when generating an initial |
| 4 | * game state from a random game seed; required to ensure that game |
| 5 | * seeds can be exchanged between versions of a puzzle compiled for |
| 6 | * different platforms. |
| 7 | * |
| 8 | * The generator is based on SHA-1. This is almost certainly |
| 9 | * overkill, but I had the SHA-1 code kicking around and it was |
| 10 | * easier to reuse it than to do anything else! |
| 11 | */ |
| 12 | |
| 13 | #include <assert.h> |
| 14 | #include <string.h> |
| 15 | #include <stdio.h> |
| 16 | |
| 17 | #include "puzzles.h" |
| 18 | |
| 19 | /* ---------------------------------------------------------------------- |
| 20 | * Core SHA algorithm: processes 16-word blocks into a message digest. |
| 21 | */ |
| 22 | |
| 23 | #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) ) |
| 24 | |
| 25 | static void SHA_Core_Init(uint32 h[5]) |
| 26 | { |
| 27 | h[0] = 0x67452301; |
| 28 | h[1] = 0xefcdab89; |
| 29 | h[2] = 0x98badcfe; |
| 30 | h[3] = 0x10325476; |
| 31 | h[4] = 0xc3d2e1f0; |
| 32 | } |
| 33 | |
| 34 | static void SHATransform(uint32 * digest, uint32 * block) |
| 35 | { |
| 36 | uint32 w[80]; |
| 37 | uint32 a, b, c, d, e; |
| 38 | int t; |
| 39 | |
| 40 | for (t = 0; t < 16; t++) |
| 41 | w[t] = block[t]; |
| 42 | |
| 43 | for (t = 16; t < 80; t++) { |
| 44 | uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16]; |
| 45 | w[t] = rol(tmp, 1); |
| 46 | } |
| 47 | |
| 48 | a = digest[0]; |
| 49 | b = digest[1]; |
| 50 | c = digest[2]; |
| 51 | d = digest[3]; |
| 52 | e = digest[4]; |
| 53 | |
| 54 | for (t = 0; t < 20; t++) { |
| 55 | uint32 tmp = |
| 56 | rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999; |
| 57 | e = d; |
| 58 | d = c; |
| 59 | c = rol(b, 30); |
| 60 | b = a; |
| 61 | a = tmp; |
| 62 | } |
| 63 | for (t = 20; t < 40; t++) { |
| 64 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1; |
| 65 | e = d; |
| 66 | d = c; |
| 67 | c = rol(b, 30); |
| 68 | b = a; |
| 69 | a = tmp; |
| 70 | } |
| 71 | for (t = 40; t < 60; t++) { |
| 72 | uint32 tmp = rol(a, |
| 73 | 5) + ((b & c) | (b & d) | (c & d)) + e + w[t] + |
| 74 | 0x8f1bbcdc; |
| 75 | e = d; |
| 76 | d = c; |
| 77 | c = rol(b, 30); |
| 78 | b = a; |
| 79 | a = tmp; |
| 80 | } |
| 81 | for (t = 60; t < 80; t++) { |
| 82 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6; |
| 83 | e = d; |
| 84 | d = c; |
| 85 | c = rol(b, 30); |
| 86 | b = a; |
| 87 | a = tmp; |
| 88 | } |
| 89 | |
| 90 | digest[0] += a; |
| 91 | digest[1] += b; |
| 92 | digest[2] += c; |
| 93 | digest[3] += d; |
| 94 | digest[4] += e; |
| 95 | } |
| 96 | |
| 97 | /* ---------------------------------------------------------------------- |
| 98 | * Outer SHA algorithm: take an arbitrary length byte string, |
| 99 | * convert it into 16-word blocks with the prescribed padding at |
| 100 | * the end, and pass those blocks to the core SHA algorithm. |
| 101 | */ |
| 102 | |
| 103 | void SHA_Init(SHA_State * s) |
| 104 | { |
| 105 | SHA_Core_Init(s->h); |
| 106 | s->blkused = 0; |
| 107 | s->lenhi = s->lenlo = 0; |
| 108 | } |
| 109 | |
| 110 | void SHA_Bytes(SHA_State * s, void *p, int len) |
| 111 | { |
| 112 | unsigned char *q = (unsigned char *) p; |
| 113 | uint32 wordblock[16]; |
| 114 | uint32 lenw = len; |
| 115 | int i; |
| 116 | |
| 117 | /* |
| 118 | * Update the length field. |
| 119 | */ |
| 120 | s->lenlo += lenw; |
| 121 | s->lenhi += (s->lenlo < lenw); |
| 122 | |
| 123 | if (s->blkused && s->blkused + len < 64) { |
| 124 | /* |
| 125 | * Trivial case: just add to the block. |
| 126 | */ |
| 127 | memcpy(s->block + s->blkused, q, len); |
| 128 | s->blkused += len; |
| 129 | } else { |
| 130 | /* |
| 131 | * We must complete and process at least one block. |
| 132 | */ |
| 133 | while (s->blkused + len >= 64) { |
| 134 | memcpy(s->block + s->blkused, q, 64 - s->blkused); |
| 135 | q += 64 - s->blkused; |
| 136 | len -= 64 - s->blkused; |
| 137 | /* Now process the block. Gather bytes big-endian into words */ |
| 138 | for (i = 0; i < 16; i++) { |
| 139 | wordblock[i] = |
| 140 | (((uint32) s->block[i * 4 + 0]) << 24) | |
| 141 | (((uint32) s->block[i * 4 + 1]) << 16) | |
| 142 | (((uint32) s->block[i * 4 + 2]) << 8) | |
| 143 | (((uint32) s->block[i * 4 + 3]) << 0); |
| 144 | } |
| 145 | SHATransform(s->h, wordblock); |
| 146 | s->blkused = 0; |
| 147 | } |
| 148 | memcpy(s->block, q, len); |
| 149 | s->blkused = len; |
| 150 | } |
| 151 | } |
| 152 | |
| 153 | void SHA_Final(SHA_State * s, unsigned char *output) |
| 154 | { |
| 155 | int i; |
| 156 | int pad; |
| 157 | unsigned char c[64]; |
| 158 | uint32 lenhi, lenlo; |
| 159 | |
| 160 | if (s->blkused >= 56) |
| 161 | pad = 56 + 64 - s->blkused; |
| 162 | else |
| 163 | pad = 56 - s->blkused; |
| 164 | |
| 165 | lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3)); |
| 166 | lenlo = (s->lenlo << 3); |
| 167 | |
| 168 | memset(c, 0, pad); |
| 169 | c[0] = 0x80; |
| 170 | SHA_Bytes(s, &c, pad); |
| 171 | |
| 172 | c[0] = (unsigned char)((lenhi >> 24) & 0xFF); |
| 173 | c[1] = (unsigned char)((lenhi >> 16) & 0xFF); |
| 174 | c[2] = (unsigned char)((lenhi >> 8) & 0xFF); |
| 175 | c[3] = (unsigned char)((lenhi >> 0) & 0xFF); |
| 176 | c[4] = (unsigned char)((lenlo >> 24) & 0xFF); |
| 177 | c[5] = (unsigned char)((lenlo >> 16) & 0xFF); |
| 178 | c[6] = (unsigned char)((lenlo >> 8) & 0xFF); |
| 179 | c[7] = (unsigned char)((lenlo >> 0) & 0xFF); |
| 180 | |
| 181 | SHA_Bytes(s, &c, 8); |
| 182 | |
| 183 | for (i = 0; i < 5; i++) { |
| 184 | output[i * 4] = (unsigned char)((s->h[i] >> 24) & 0xFF); |
| 185 | output[i * 4 + 1] = (unsigned char)((s->h[i] >> 16) & 0xFF); |
| 186 | output[i * 4 + 2] = (unsigned char)((s->h[i] >> 8) & 0xFF); |
| 187 | output[i * 4 + 3] = (unsigned char)((s->h[i]) & 0xFF); |
| 188 | } |
| 189 | } |
| 190 | |
| 191 | void SHA_Simple(void *p, int len, unsigned char *output) |
| 192 | { |
| 193 | SHA_State s; |
| 194 | |
| 195 | SHA_Init(&s); |
| 196 | SHA_Bytes(&s, p, len); |
| 197 | SHA_Final(&s, output); |
| 198 | } |
| 199 | |
| 200 | /* ---------------------------------------------------------------------- |
| 201 | * The random number generator. |
| 202 | */ |
| 203 | |
| 204 | struct random_state { |
| 205 | unsigned char seedbuf[40]; |
| 206 | unsigned char databuf[20]; |
| 207 | int pos; |
| 208 | }; |
| 209 | |
| 210 | random_state *random_init(char *seed, int len) |
| 211 | { |
| 212 | random_state *state; |
| 213 | |
| 214 | state = snew(random_state); |
| 215 | |
| 216 | SHA_Simple(seed, len, state->seedbuf); |
| 217 | SHA_Simple(state->seedbuf, 20, state->seedbuf + 20); |
| 218 | SHA_Simple(state->seedbuf, 40, state->databuf); |
| 219 | state->pos = 0; |
| 220 | |
| 221 | return state; |
| 222 | } |
| 223 | |
| 224 | random_state *random_copy(random_state *tocopy) |
| 225 | { |
| 226 | random_state *result; |
| 227 | result = snew(random_state); |
| 228 | memcpy(result->seedbuf, tocopy->seedbuf, sizeof(result->seedbuf)); |
| 229 | memcpy(result->databuf, tocopy->databuf, sizeof(result->databuf)); |
| 230 | result->pos = tocopy->pos; |
| 231 | return result; |
| 232 | } |
| 233 | |
| 234 | unsigned long random_bits(random_state *state, int bits) |
| 235 | { |
| 236 | unsigned long ret = 0; |
| 237 | int n; |
| 238 | |
| 239 | for (n = 0; n < bits; n += 8) { |
| 240 | if (state->pos >= 20) { |
| 241 | int i; |
| 242 | |
| 243 | for (i = 0; i < 20; i++) { |
| 244 | if (state->seedbuf[i] != 0xFF) { |
| 245 | state->seedbuf[i]++; |
| 246 | break; |
| 247 | } else |
| 248 | state->seedbuf[i] = 0; |
| 249 | } |
| 250 | SHA_Simple(state->seedbuf, 40, state->databuf); |
| 251 | state->pos = 0; |
| 252 | } |
| 253 | ret = (ret << 8) | state->databuf[state->pos++]; |
| 254 | } |
| 255 | |
| 256 | /* |
| 257 | * `(1 << bits) - 1' is not good enough, since if bits==32 on a |
| 258 | * 32-bit machine, behaviour is undefined and Intel has a nasty |
| 259 | * habit of shifting left by zero instead. We'll shift by |
| 260 | * bits-1 and then separately shift by one. |
| 261 | */ |
| 262 | ret &= (1 << (bits-1)) * 2 - 1; |
| 263 | return ret; |
| 264 | } |
| 265 | |
| 266 | unsigned long random_upto(random_state *state, unsigned long limit) |
| 267 | { |
| 268 | int bits = 0; |
| 269 | unsigned long max, divisor, data; |
| 270 | |
| 271 | while ((limit >> bits) != 0) |
| 272 | bits++; |
| 273 | |
| 274 | bits += 3; |
| 275 | assert(bits < 32); |
| 276 | |
| 277 | max = 1L << bits; |
| 278 | divisor = max / limit; |
| 279 | max = limit * divisor; |
| 280 | |
| 281 | do { |
| 282 | data = random_bits(state, bits); |
| 283 | } while (data >= max); |
| 284 | |
| 285 | return data / divisor; |
| 286 | } |
| 287 | |
| 288 | void random_free(random_state *state) |
| 289 | { |
| 290 | sfree(state); |
| 291 | } |
| 292 | |
| 293 | char *random_state_encode(random_state *state) |
| 294 | { |
| 295 | char retbuf[256]; |
| 296 | int len = 0, i; |
| 297 | |
| 298 | for (i = 0; i < lenof(state->seedbuf); i++) |
| 299 | len += sprintf(retbuf+len, "%02x", state->seedbuf[i]); |
| 300 | for (i = 0; i < lenof(state->databuf); i++) |
| 301 | len += sprintf(retbuf+len, "%02x", state->databuf[i]); |
| 302 | len += sprintf(retbuf+len, "%02x", state->pos); |
| 303 | |
| 304 | return dupstr(retbuf); |
| 305 | } |
| 306 | |
| 307 | random_state *random_state_decode(char *input) |
| 308 | { |
| 309 | random_state *state; |
| 310 | int pos, byte, digits; |
| 311 | |
| 312 | state = snew(random_state); |
| 313 | |
| 314 | memset(state->seedbuf, 0, sizeof(state->seedbuf)); |
| 315 | memset(state->databuf, 0, sizeof(state->databuf)); |
| 316 | state->pos = 0; |
| 317 | |
| 318 | byte = digits = 0; |
| 319 | pos = 0; |
| 320 | while (*input) { |
| 321 | int v = *input++; |
| 322 | |
| 323 | if (v >= '0' && v <= '9') |
| 324 | v = v - '0'; |
| 325 | else if (v >= 'A' && v <= 'F') |
| 326 | v = v - 'A' + 10; |
| 327 | else if (v >= 'a' && v <= 'f') |
| 328 | v = v - 'a' + 10; |
| 329 | else |
| 330 | v = 0; |
| 331 | |
| 332 | byte = (byte << 4) | v; |
| 333 | digits++; |
| 334 | |
| 335 | if (digits == 2) { |
| 336 | /* |
| 337 | * We have a byte. Put it somewhere. |
| 338 | */ |
| 339 | if (pos < lenof(state->seedbuf)) |
| 340 | state->seedbuf[pos++] = byte; |
| 341 | else if (pos < lenof(state->seedbuf) + lenof(state->databuf)) |
| 342 | state->databuf[pos++ - lenof(state->seedbuf)] = byte; |
| 343 | else if (pos == lenof(state->seedbuf) + lenof(state->databuf) && |
| 344 | byte <= lenof(state->databuf)) |
| 345 | state->pos = byte; |
| 346 | byte = digits = 0; |
| 347 | } |
| 348 | } |
| 349 | |
| 350 | return state; |
| 351 | } |