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1 | /* -*-c-*- |
2 | * |
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3 | * Random number generator for DSA |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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9 | * |
10 | * This file is part of Catacomb. |
11 | * |
12 | * Catacomb is free software; you can redistribute it and/or modify |
13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the |
15 | * License, or (at your option) any later version. |
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16 | * |
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17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU Library General Public License for more details. |
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21 | * |
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22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <stdarg.h> |
31 | #include <string.h> |
32 | |
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33 | #include <mLib/alloc.h> |
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34 | #include <mLib/bits.h> |
35 | #include <mLib/sub.h> |
36 | |
37 | #include "dsarand.h" |
38 | #include "grand.h" |
39 | #include "sha.h" |
40 | |
41 | /*----- Main code ---------------------------------------------------------*/ |
42 | |
43 | /* --- @STEP@ --- * |
44 | * |
45 | * Arguments: @dsarand *d@ = pointer to context |
46 | * |
47 | * Use: Increments the buffer by one, interpreting it as a big-endian |
48 | * integer. Carries outside the integer are discarded. |
49 | */ |
50 | |
51 | #define STEP(d) do { \ |
52 | dsarand *_d = (d); \ |
53 | octet *_p = _d->p; \ |
54 | octet *_q = _p + _d->sz; \ |
55 | unsigned _c = 1; \ |
56 | while (_c && _q > _p) { \ |
57 | _c += *--_q; \ |
58 | *_q = U8(_c); \ |
59 | _c >>= 8; \ |
60 | } \ |
61 | } while (0) |
62 | |
63 | /* --- @dsarand_init@ --- * |
64 | * |
65 | * Arguments: @dsarand *d@ = pointer to context |
66 | * @const void *p@ = pointer to seed buffer |
67 | * @size_t sz@ = size of the buffer |
68 | * |
69 | * Returns: --- |
70 | * |
71 | * Use: Initializes a DSA random number generator. |
72 | */ |
73 | |
74 | void dsarand_init(dsarand *d, const void *p, size_t sz) |
75 | { |
76 | d->p = xmalloc(sz); |
77 | d->sz = sz; |
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78 | d->passes = 1; |
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79 | if (p) |
80 | memcpy(d->p, p, sz); |
81 | } |
82 | |
83 | /* --- @dsarand_reseed@ --- * |
84 | * |
85 | * Arguments: @dsarand *d@ = pointer to context |
86 | * @const void *p@ = pointer to seed buffer |
87 | * @size_t sz@ = size of the buffer |
88 | * |
89 | * Returns: --- |
90 | * |
91 | * Use: Initializes a DSA random number generator. |
92 | */ |
93 | |
94 | void dsarand_reseed(dsarand *d, const void *p, size_t sz) |
95 | { |
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96 | xfree(d->p); |
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97 | d->p = xmalloc(sz); |
98 | d->sz = sz; |
99 | d->passes = 1; |
100 | if (p) |
101 | memcpy(d->p, p, sz); |
102 | } |
103 | |
104 | /* --- @dsarand_destroy@ --- * |
105 | * |
106 | * Arguments: @dsarand *d@ = pointer to context |
107 | * |
108 | * Returns: --- |
109 | * |
110 | * Use: Disposes of a DSA random number generation context. |
111 | */ |
112 | |
113 | void dsarand_destroy(dsarand *d) |
114 | { |
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115 | xfree(d->p); |
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116 | } |
117 | |
118 | /* --- @dsarand_fill@ --- * |
119 | * |
120 | * Arguments: @dsarand *d@ = pointer to context |
121 | * @void *p@ = pointer to output buffer |
122 | * @size_t sz@ = size of output buffer |
123 | * |
124 | * Returns: --- |
125 | * |
126 | * Use: Fills an output buffer with pseudorandom data. |
127 | * |
128 | * Let %$p$% be the numerical value of the input buffer, and let |
129 | * %$b$% be the number of bytes required. Let |
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130 | * %$z = \lceil b / 20 \rceil$% be the number of SHA outputs |
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131 | * required. Then the output of pass %$n$% is |
132 | * |
133 | * %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$% |
134 | * %${} \bmod 2^{8b}$% |
135 | * |
136 | * and the actual result in the output buffer is the XOR of all |
137 | * of the output passes. |
138 | * |
139 | * The DSA procedure for choosing @q@ involves two passes with |
140 | * %$z = 1$%; the procedure for choosing @p@ involves one pass |
141 | * with larger %$z$%. This generalization of the DSA generation |
142 | * procedure is my own invention but it seems relatively sound. |
143 | */ |
144 | |
145 | void dsarand_fill(dsarand *d, void *p, size_t sz) |
146 | { |
147 | octet *q = p; |
148 | unsigned n = d->passes; |
149 | |
150 | /* --- Write out the first pass --- * |
151 | * |
152 | * This can write directly to the output buffer, so it's done differently |
153 | * from the latter passes. |
154 | */ |
155 | |
156 | { |
157 | size_t o = sz; |
158 | |
159 | while (o) { |
160 | sha_ctx h; |
161 | |
162 | /* --- Hash the input buffer --- */ |
163 | |
164 | sha_init(&h); |
165 | sha_hash(&h, d->p, d->sz); |
166 | |
167 | /* --- If enough space, extract the hash output directly --- */ |
168 | |
169 | if (o >= SHA_HASHSZ) { |
170 | o -= SHA_HASHSZ; |
171 | sha_done(&h, q + o); |
172 | } |
173 | |
174 | /* --- Otherwise take the hash result out of line and copy it --- */ |
175 | |
176 | else { |
177 | octet hash[SHA_HASHSZ]; |
178 | sha_done(&h, hash); |
179 | memcpy(q, hash + (SHA_HASHSZ - o), o); |
180 | o = 0; |
181 | } |
182 | |
183 | /* --- Step the input buffer --- */ |
184 | |
185 | STEP(d); |
186 | } |
187 | |
188 | /* --- Another pass has been done --- */ |
189 | |
190 | n--; |
191 | } |
192 | |
193 | /* --- Write out subsequent passes --- * |
194 | * |
195 | * The hash output has to be done offline, so this is slightly easier. |
196 | */ |
197 | |
198 | while (n) { |
199 | size_t o = sz; |
200 | |
201 | while (o) { |
202 | sha_ctx h; |
203 | octet hash[SHA_HASHSZ]; |
204 | size_t n; |
205 | octet *pp, *qq; |
206 | |
207 | /* --- Hash the input buffer --- */ |
208 | |
209 | sha_init(&h); |
210 | sha_hash(&h, d->p, d->sz); |
211 | sha_done(&h, hash); |
212 | |
213 | /* --- Work out how much output is wanted --- */ |
214 | |
215 | n = SHA_HASHSZ; |
216 | if (n > o) |
217 | n = o; |
218 | o -= n; |
219 | |
220 | /* --- XOR the data out --- */ |
221 | |
222 | for (pp = hash + (SHA_HASHSZ - n), qq = q + o; |
223 | pp < hash + SHA_HASHSZ; pp++, qq++) |
224 | *qq ^= *pp; |
225 | |
226 | /* --- Step the input buffer --- */ |
227 | |
228 | STEP(d); |
229 | } |
230 | |
231 | /* --- Another pass is done --- */ |
232 | |
233 | n--; |
234 | } |
235 | } |
236 | |
237 | /*----- Generic pseudorandom-number generator interface -------------------*/ |
238 | |
239 | static const grand_ops gops; |
240 | |
241 | typedef struct gctx { |
242 | grand r; |
243 | dsarand d; |
244 | } gctx; |
245 | |
246 | static void gdestroy(grand *r) |
247 | { |
248 | gctx *g = (gctx *)r; |
249 | dsarand_destroy(&g->d); |
250 | DESTROY(g); |
251 | } |
252 | |
253 | static int gmisc(grand *r, unsigned op, ...) |
254 | { |
255 | gctx *g = (gctx *)r; |
256 | va_list ap; |
257 | int rc = 0; |
258 | va_start(ap, op); |
259 | |
260 | switch (op) { |
261 | case GRAND_CHECK: |
262 | switch (va_arg(ap, unsigned)) { |
263 | case GRAND_CHECK: |
264 | case GRAND_SEEDBLOCK: |
265 | case GRAND_SEEDRAND: |
266 | case DSARAND_PASSES: |
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267 | case DSARAND_SEEDSZ: |
268 | case DSARAND_GETSEED: |
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269 | rc = 1; |
270 | break; |
271 | default: |
272 | rc = 0; |
273 | break; |
274 | } |
275 | break; |
276 | case GRAND_SEEDBLOCK: { |
277 | const void *p = va_arg(ap, const void *); |
278 | size_t sz = va_arg(ap, size_t); |
279 | dsarand_reseed(&g->d, p, sz); |
280 | } break; |
281 | case GRAND_SEEDRAND: { |
282 | grand *rr = va_arg(ap, grand *); |
283 | rr->ops->fill(rr, g->d.p, g->d.sz); |
284 | } break; |
285 | case DSARAND_PASSES: |
286 | g->d.passes = va_arg(ap, unsigned); |
287 | break; |
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288 | case DSARAND_SEEDSZ: |
289 | rc = g->d.sz; |
290 | break; |
291 | case DSARAND_GETSEED: |
292 | memcpy(va_arg(ap, void *), g->d.p, g->d.sz); |
293 | break; |
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294 | default: |
295 | GRAND_BADOP; |
296 | break; |
297 | } |
298 | |
299 | va_end(ap); |
300 | return (rc); |
301 | } |
302 | |
303 | static void gfill(grand *r, void *p, size_t sz) |
304 | { |
305 | gctx *g = (gctx *)r; |
306 | dsarand_fill(&g->d, p, sz); |
307 | } |
308 | |
309 | static const grand_ops gops = { |
310 | "dsarand", |
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311 | 0, 0, |
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312 | gmisc, gdestroy, |
313 | grand_word, grand_byte, grand_word, grand_range, gfill |
314 | }; |
315 | |
316 | /* --- @dsarand_create@ --- * |
317 | * |
318 | * Arguments: @const void *p@ = pointer to seed buffer |
319 | * @size_t sz@ = size of seed buffer |
320 | * |
321 | * Returns: Pointer to a generic generator. |
322 | * |
323 | * Use: Constructs a generic generator interface over a Catacomb |
324 | * entropy pool generator. |
325 | */ |
326 | |
327 | grand *dsarand_create(const void *p, size_t sz) |
328 | { |
329 | gctx *g = CREATE(gctx); |
330 | g->r.ops = &gops; |
331 | dsarand_init(&g->d, p, sz); |
332 | return (&g->r); |
333 | } |
334 | |
335 | /*----- That's all, folks -------------------------------------------------*/ |