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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: dsarand.c,v 1.2 2000/06/17 10:54:00 mdw Exp $ |
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4 | * |
5 | * Random number generator for DSA |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: dsarand.c,v $ |
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33 | * Revision 1.2 2000/06/17 10:54:00 mdw |
34 | * Typesetting fixes. Arena support. |
35 | * |
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36 | * Revision 1.1 1999/12/22 15:53:12 mdw |
37 | * Random number generator for finding DSA parameters. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <stdarg.h> |
44 | #include <string.h> |
45 | |
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46 | #include <mLib/alloc.h> |
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47 | #include <mLib/bits.h> |
48 | #include <mLib/sub.h> |
49 | |
50 | #include "dsarand.h" |
51 | #include "grand.h" |
52 | #include "sha.h" |
53 | |
54 | /*----- Main code ---------------------------------------------------------*/ |
55 | |
56 | /* --- @STEP@ --- * |
57 | * |
58 | * Arguments: @dsarand *d@ = pointer to context |
59 | * |
60 | * Use: Increments the buffer by one, interpreting it as a big-endian |
61 | * integer. Carries outside the integer are discarded. |
62 | */ |
63 | |
64 | #define STEP(d) do { \ |
65 | dsarand *_d = (d); \ |
66 | octet *_p = _d->p; \ |
67 | octet *_q = _p + _d->sz; \ |
68 | unsigned _c = 1; \ |
69 | while (_c && _q > _p) { \ |
70 | _c += *--_q; \ |
71 | *_q = U8(_c); \ |
72 | _c >>= 8; \ |
73 | } \ |
74 | } while (0) |
75 | |
76 | /* --- @dsarand_init@ --- * |
77 | * |
78 | * Arguments: @dsarand *d@ = pointer to context |
79 | * @const void *p@ = pointer to seed buffer |
80 | * @size_t sz@ = size of the buffer |
81 | * |
82 | * Returns: --- |
83 | * |
84 | * Use: Initializes a DSA random number generator. |
85 | */ |
86 | |
87 | void dsarand_init(dsarand *d, const void *p, size_t sz) |
88 | { |
89 | d->p = xmalloc(sz); |
90 | d->sz = sz; |
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91 | d->passes = 1; |
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92 | if (p) |
93 | memcpy(d->p, p, sz); |
94 | } |
95 | |
96 | /* --- @dsarand_reseed@ --- * |
97 | * |
98 | * Arguments: @dsarand *d@ = pointer to context |
99 | * @const void *p@ = pointer to seed buffer |
100 | * @size_t sz@ = size of the buffer |
101 | * |
102 | * Returns: --- |
103 | * |
104 | * Use: Initializes a DSA random number generator. |
105 | */ |
106 | |
107 | void dsarand_reseed(dsarand *d, const void *p, size_t sz) |
108 | { |
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109 | xfree(d->p); |
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110 | d->p = xmalloc(sz); |
111 | d->sz = sz; |
112 | d->passes = 1; |
113 | if (p) |
114 | memcpy(d->p, p, sz); |
115 | } |
116 | |
117 | /* --- @dsarand_destroy@ --- * |
118 | * |
119 | * Arguments: @dsarand *d@ = pointer to context |
120 | * |
121 | * Returns: --- |
122 | * |
123 | * Use: Disposes of a DSA random number generation context. |
124 | */ |
125 | |
126 | void dsarand_destroy(dsarand *d) |
127 | { |
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128 | xfree(d->p); |
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129 | } |
130 | |
131 | /* --- @dsarand_fill@ --- * |
132 | * |
133 | * Arguments: @dsarand *d@ = pointer to context |
134 | * @void *p@ = pointer to output buffer |
135 | * @size_t sz@ = size of output buffer |
136 | * |
137 | * Returns: --- |
138 | * |
139 | * Use: Fills an output buffer with pseudorandom data. |
140 | * |
141 | * Let %$p$% be the numerical value of the input buffer, and let |
142 | * %$b$% be the number of bytes required. Let |
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143 | * %$z = \lceil b / 20 \rceil$% be the number of SHA outputs |
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144 | * required. Then the output of pass %$n$% is |
145 | * |
146 | * %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$% |
147 | * %${} \bmod 2^{8b}$% |
148 | * |
149 | * and the actual result in the output buffer is the XOR of all |
150 | * of the output passes. |
151 | * |
152 | * The DSA procedure for choosing @q@ involves two passes with |
153 | * %$z = 1$%; the procedure for choosing @p@ involves one pass |
154 | * with larger %$z$%. This generalization of the DSA generation |
155 | * procedure is my own invention but it seems relatively sound. |
156 | */ |
157 | |
158 | void dsarand_fill(dsarand *d, void *p, size_t sz) |
159 | { |
160 | octet *q = p; |
161 | unsigned n = d->passes; |
162 | |
163 | /* --- Write out the first pass --- * |
164 | * |
165 | * This can write directly to the output buffer, so it's done differently |
166 | * from the latter passes. |
167 | */ |
168 | |
169 | { |
170 | size_t o = sz; |
171 | |
172 | while (o) { |
173 | sha_ctx h; |
174 | |
175 | /* --- Hash the input buffer --- */ |
176 | |
177 | sha_init(&h); |
178 | sha_hash(&h, d->p, d->sz); |
179 | |
180 | /* --- If enough space, extract the hash output directly --- */ |
181 | |
182 | if (o >= SHA_HASHSZ) { |
183 | o -= SHA_HASHSZ; |
184 | sha_done(&h, q + o); |
185 | } |
186 | |
187 | /* --- Otherwise take the hash result out of line and copy it --- */ |
188 | |
189 | else { |
190 | octet hash[SHA_HASHSZ]; |
191 | sha_done(&h, hash); |
192 | memcpy(q, hash + (SHA_HASHSZ - o), o); |
193 | o = 0; |
194 | } |
195 | |
196 | /* --- Step the input buffer --- */ |
197 | |
198 | STEP(d); |
199 | } |
200 | |
201 | /* --- Another pass has been done --- */ |
202 | |
203 | n--; |
204 | } |
205 | |
206 | /* --- Write out subsequent passes --- * |
207 | * |
208 | * The hash output has to be done offline, so this is slightly easier. |
209 | */ |
210 | |
211 | while (n) { |
212 | size_t o = sz; |
213 | |
214 | while (o) { |
215 | sha_ctx h; |
216 | octet hash[SHA_HASHSZ]; |
217 | size_t n; |
218 | octet *pp, *qq; |
219 | |
220 | /* --- Hash the input buffer --- */ |
221 | |
222 | sha_init(&h); |
223 | sha_hash(&h, d->p, d->sz); |
224 | sha_done(&h, hash); |
225 | |
226 | /* --- Work out how much output is wanted --- */ |
227 | |
228 | n = SHA_HASHSZ; |
229 | if (n > o) |
230 | n = o; |
231 | o -= n; |
232 | |
233 | /* --- XOR the data out --- */ |
234 | |
235 | for (pp = hash + (SHA_HASHSZ - n), qq = q + o; |
236 | pp < hash + SHA_HASHSZ; pp++, qq++) |
237 | *qq ^= *pp; |
238 | |
239 | /* --- Step the input buffer --- */ |
240 | |
241 | STEP(d); |
242 | } |
243 | |
244 | /* --- Another pass is done --- */ |
245 | |
246 | n--; |
247 | } |
248 | } |
249 | |
250 | /*----- Generic pseudorandom-number generator interface -------------------*/ |
251 | |
252 | static const grand_ops gops; |
253 | |
254 | typedef struct gctx { |
255 | grand r; |
256 | dsarand d; |
257 | } gctx; |
258 | |
259 | static void gdestroy(grand *r) |
260 | { |
261 | gctx *g = (gctx *)r; |
262 | dsarand_destroy(&g->d); |
263 | DESTROY(g); |
264 | } |
265 | |
266 | static int gmisc(grand *r, unsigned op, ...) |
267 | { |
268 | gctx *g = (gctx *)r; |
269 | va_list ap; |
270 | int rc = 0; |
271 | va_start(ap, op); |
272 | |
273 | switch (op) { |
274 | case GRAND_CHECK: |
275 | switch (va_arg(ap, unsigned)) { |
276 | case GRAND_CHECK: |
277 | case GRAND_SEEDBLOCK: |
278 | case GRAND_SEEDRAND: |
279 | case DSARAND_PASSES: |
280 | rc = 1; |
281 | break; |
282 | default: |
283 | rc = 0; |
284 | break; |
285 | } |
286 | break; |
287 | case GRAND_SEEDBLOCK: { |
288 | const void *p = va_arg(ap, const void *); |
289 | size_t sz = va_arg(ap, size_t); |
290 | dsarand_reseed(&g->d, p, sz); |
291 | } break; |
292 | case GRAND_SEEDRAND: { |
293 | grand *rr = va_arg(ap, grand *); |
294 | rr->ops->fill(rr, g->d.p, g->d.sz); |
295 | } break; |
296 | case DSARAND_PASSES: |
297 | g->d.passes = va_arg(ap, unsigned); |
298 | break; |
299 | default: |
300 | GRAND_BADOP; |
301 | break; |
302 | } |
303 | |
304 | va_end(ap); |
305 | return (rc); |
306 | } |
307 | |
308 | static void gfill(grand *r, void *p, size_t sz) |
309 | { |
310 | gctx *g = (gctx *)r; |
311 | dsarand_fill(&g->d, p, sz); |
312 | } |
313 | |
314 | static const grand_ops gops = { |
315 | "dsarand", |
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316 | 0, 0, |
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317 | gmisc, gdestroy, |
318 | grand_word, grand_byte, grand_word, grand_range, gfill |
319 | }; |
320 | |
321 | /* --- @dsarand_create@ --- * |
322 | * |
323 | * Arguments: @const void *p@ = pointer to seed buffer |
324 | * @size_t sz@ = size of seed buffer |
325 | * |
326 | * Returns: Pointer to a generic generator. |
327 | * |
328 | * Use: Constructs a generic generator interface over a Catacomb |
329 | * entropy pool generator. |
330 | */ |
331 | |
332 | grand *dsarand_create(const void *p, size_t sz) |
333 | { |
334 | gctx *g = CREATE(gctx); |
335 | g->r.ops = &gops; |
336 | dsarand_init(&g->d, p, sz); |
337 | return (&g->r); |
338 | } |
339 | |
340 | /*----- That's all, folks -------------------------------------------------*/ |