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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> |
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14 | #include <string.h> |
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15 | #include <stdio.h> |
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16 | |
17 | #include "puzzles.h" |
18 | |
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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 | |
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103 | void SHA_Init(SHA_State * s) |
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104 | { |
105 | SHA_Core_Init(s->h); |
106 | s->blkused = 0; |
107 | s->lenhi = s->lenlo = 0; |
108 | } |
109 | |
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110 | void SHA_Bytes(SHA_State * s, void *p, int len) |
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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 | |
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153 | void SHA_Final(SHA_State * s, unsigned char *output) |
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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 | |
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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); |
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180 | |
181 | SHA_Bytes(s, &c, 8); |
182 | |
183 | for (i = 0; i < 5; i++) { |
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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); |
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188 | } |
189 | } |
190 | |
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191 | void SHA_Simple(void *p, int len, unsigned char *output) |
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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 | unsigned long random_bits(random_state *state, int bits) |
225 | { |
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226 | unsigned long ret = 0; |
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227 | int n; |
228 | |
229 | for (n = 0; n < bits; n += 8) { |
230 | if (state->pos >= 20) { |
231 | int i; |
232 | |
233 | for (i = 0; i < 20; i++) { |
234 | if (state->seedbuf[i] != 0xFF) { |
235 | state->seedbuf[i]++; |
236 | break; |
237 | } else |
238 | state->seedbuf[i] = 0; |
239 | } |
240 | SHA_Simple(state->seedbuf, 40, state->databuf); |
241 | state->pos = 0; |
242 | } |
243 | ret = (ret << 8) | state->databuf[state->pos++]; |
244 | } |
245 | |
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246 | /* |
247 | * `(1 << bits) - 1' is not good enough, since if bits==32 on a |
248 | * 32-bit machine, behaviour is undefined and Intel has a nasty |
249 | * habit of shifting left by zero instead. We'll shift by |
250 | * bits-1 and then separately shift by one. |
251 | */ |
252 | ret &= (1 << (bits-1)) * 2 - 1; |
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253 | return ret; |
254 | } |
255 | |
256 | unsigned long random_upto(random_state *state, unsigned long limit) |
257 | { |
258 | int bits = 0; |
259 | unsigned long max, divisor, data; |
260 | |
261 | while ((limit >> bits) != 0) |
262 | bits++; |
263 | |
264 | bits += 3; |
265 | assert(bits < 32); |
266 | |
267 | max = 1 << bits; |
268 | divisor = max / limit; |
269 | max = limit * divisor; |
270 | |
271 | do { |
272 | data = random_bits(state, bits); |
273 | } while (data >= max); |
274 | |
275 | return data / divisor; |
276 | } |
277 | |
278 | void random_free(random_state *state) |
279 | { |
280 | sfree(state); |
281 | } |
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282 | |
283 | char *random_state_encode(random_state *state) |
284 | { |
285 | char retbuf[256]; |
286 | int len = 0, i; |
287 | |
288 | for (i = 0; i < lenof(state->seedbuf); i++) |
289 | len += sprintf(retbuf+len, "%02x", state->seedbuf[i]); |
290 | for (i = 0; i < lenof(state->databuf); i++) |
291 | len += sprintf(retbuf+len, "%02x", state->databuf[i]); |
292 | len += sprintf(retbuf+len, "%02x", state->pos); |
293 | |
294 | return dupstr(retbuf); |
295 | } |
296 | |
297 | random_state *random_state_decode(char *input) |
298 | { |
299 | random_state *state; |
300 | int pos, byte, digits; |
301 | |
302 | state = snew(random_state); |
303 | |
304 | memset(state->seedbuf, 0, sizeof(state->seedbuf)); |
305 | memset(state->databuf, 0, sizeof(state->databuf)); |
306 | state->pos = 0; |
307 | |
308 | byte = digits = 0; |
309 | pos = 0; |
310 | while (*input) { |
311 | int v = *input++; |
312 | |
313 | if (v >= '0' && v <= '9') |
314 | v = v - '0'; |
315 | else if (v >= 'A' && v <= 'F') |
316 | v = v - 'A' + 10; |
317 | else if (v >= 'a' && v <= 'f') |
318 | v = v - 'a' + 10; |
319 | else |
320 | v = 0; |
321 | |
322 | byte = (byte << 4) | v; |
323 | digits++; |
324 | |
325 | if (digits == 2) { |
326 | /* |
327 | * We have a byte. Put it somewhere. |
328 | */ |
329 | if (pos < lenof(state->seedbuf)) |
330 | state->seedbuf[pos++] = byte; |
331 | else if (pos < lenof(state->seedbuf) + lenof(state->databuf)) |
332 | state->databuf[pos++ - lenof(state->seedbuf)] = byte; |
333 | else if (pos == lenof(state->seedbuf) + lenof(state->databuf) && |
334 | byte <= lenof(state->databuf)) |
335 | state->pos = byte; |
336 | byte = digits = 0; |
337 | } |
338 | } |
339 | |
340 | return state; |
341 | } |