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source: vbox/trunk/src/libs/openssl-1.1.1g/crypto/dsa/dsa_ossl.c@ 85201

最後變更 在這個檔案從85201是 83916,由 vboxsync 提交於 5 年 前

openssl-1.1.1g: Applied and adjusted our OpenSSL changes to 1.1.1g. bugref:9719
檔案大小: 11.9 KB
行 
1/*
2 * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <stdio.h>
11#include "internal/cryptlib.h"
12#include "crypto/bn.h"
13#include <openssl/bn.h>
14#include <openssl/sha.h>
15#include "dsa_local.h"
16#include <openssl/asn1.h>
17
18static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
19static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
20 BIGNUM **rp);
21static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
22 BIGNUM **rp, const unsigned char *dgst, int dlen);
23static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
24 DSA_SIG *sig, DSA *dsa);
25static int dsa_init(DSA *dsa);
26static int dsa_finish(DSA *dsa);
27static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
28 BN_CTX *ctx);
29
30static DSA_METHOD openssl_dsa_meth = {
31 "OpenSSL DSA method",
32 dsa_do_sign,
33 dsa_sign_setup_no_digest,
34 dsa_do_verify,
35 NULL, /* dsa_mod_exp, */
36 NULL, /* dsa_bn_mod_exp, */
37 dsa_init,
38 dsa_finish,
39 DSA_FLAG_FIPS_METHOD,
40 NULL,
41 NULL,
42 NULL
43};
44
45static const DSA_METHOD *default_DSA_method = &openssl_dsa_meth;
46
47void DSA_set_default_method(const DSA_METHOD *meth)
48{
49 default_DSA_method = meth;
50}
51
52const DSA_METHOD *DSA_get_default_method(void)
53{
54 return default_DSA_method;
55}
56
57const DSA_METHOD *DSA_OpenSSL(void)
58{
59 return &openssl_dsa_meth;
60}
61
62static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
63{
64 BIGNUM *kinv = NULL;
65 BIGNUM *m, *blind, *blindm, *tmp;
66 BN_CTX *ctx = NULL;
67 int reason = ERR_R_BN_LIB;
68 DSA_SIG *ret = NULL;
69 int rv = 0;
70
71 if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) {
72 reason = DSA_R_MISSING_PARAMETERS;
73 goto err;
74 }
75 if (dsa->priv_key == NULL) {
76 reason = DSA_R_MISSING_PRIVATE_KEY;
77 goto err;
78 }
79
80 ret = DSA_SIG_new();
81 if (ret == NULL)
82 goto err;
83 ret->r = BN_new();
84 ret->s = BN_new();
85 if (ret->r == NULL || ret->s == NULL)
86 goto err;
87
88 ctx = BN_CTX_new();
89 if (ctx == NULL)
90 goto err;
91 m = BN_CTX_get(ctx);
92 blind = BN_CTX_get(ctx);
93 blindm = BN_CTX_get(ctx);
94 tmp = BN_CTX_get(ctx);
95 if (tmp == NULL)
96 goto err;
97
98 redo:
99 if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen))
100 goto err;
101
102 if (dlen > BN_num_bytes(dsa->q))
103 /*
104 * if the digest length is greater than the size of q use the
105 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
106 * 4.2
107 */
108 dlen = BN_num_bytes(dsa->q);
109 if (BN_bin2bn(dgst, dlen, m) == NULL)
110 goto err;
111
112 /*
113 * The normal signature calculation is:
114 *
115 * s := k^-1 * (m + r * priv_key) mod q
116 *
117 * We will blind this to protect against side channel attacks
118 *
119 * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q
120 */
121
122 /* Generate a blinding value */
123 do {
124 if (!BN_priv_rand(blind, BN_num_bits(dsa->q) - 1,
125 BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
126 goto err;
127 } while (BN_is_zero(blind));
128 BN_set_flags(blind, BN_FLG_CONSTTIME);
129 BN_set_flags(blindm, BN_FLG_CONSTTIME);
130 BN_set_flags(tmp, BN_FLG_CONSTTIME);
131
132 /* tmp := blind * priv_key * r mod q */
133 if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->q, ctx))
134 goto err;
135 if (!BN_mod_mul(tmp, tmp, ret->r, dsa->q, ctx))
136 goto err;
137
138 /* blindm := blind * m mod q */
139 if (!BN_mod_mul(blindm, blind, m, dsa->q, ctx))
140 goto err;
141
142 /* s : = (blind * priv_key * r) + (blind * m) mod q */
143 if (!BN_mod_add_quick(ret->s, tmp, blindm, dsa->q))
144 goto err;
145
146 /* s := s * k^-1 mod q */
147 if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->q, ctx))
148 goto err;
149
150 /* s:= s * blind^-1 mod q */
151 if (BN_mod_inverse(blind, blind, dsa->q, ctx) == NULL)
152 goto err;
153 if (!BN_mod_mul(ret->s, ret->s, blind, dsa->q, ctx))
154 goto err;
155
156 /*
157 * Redo if r or s is zero as required by FIPS 186-3: this is very
158 * unlikely.
159 */
160 if (BN_is_zero(ret->r) || BN_is_zero(ret->s))
161 goto redo;
162
163 rv = 1;
164
165 err:
166 if (rv == 0) {
167 DSAerr(DSA_F_DSA_DO_SIGN, reason);
168 DSA_SIG_free(ret);
169 ret = NULL;
170 }
171 BN_CTX_free(ctx);
172 BN_clear_free(kinv);
173 return ret;
174}
175
176static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
177 BIGNUM **kinvp, BIGNUM **rp)
178{
179 return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
180}
181
182static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
183 BIGNUM **kinvp, BIGNUM **rp,
184 const unsigned char *dgst, int dlen)
185{
186 BN_CTX *ctx = NULL;
187 BIGNUM *k, *kinv = NULL, *r = *rp;
188 BIGNUM *l;
189 int ret = 0;
190 int q_bits, q_words;
191
192 if (!dsa->p || !dsa->q || !dsa->g) {
193 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
194 return 0;
195 }
196
197 /* Reject obviously invalid parameters */
198 if (BN_is_zero(dsa->p) || BN_is_zero(dsa->q) || BN_is_zero(dsa->g)) {
199 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_INVALID_PARAMETERS);
200 return 0;
201 }
202 if (dsa->priv_key == NULL) {
203 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PRIVATE_KEY);
204 return 0;
205 }
206
207 k = BN_new();
208 l = BN_new();
209 if (k == NULL || l == NULL)
210 goto err;
211
212 if (ctx_in == NULL) {
213 if ((ctx = BN_CTX_new()) == NULL)
214 goto err;
215 } else
216 ctx = ctx_in;
217
218 /* Preallocate space */
219 q_bits = BN_num_bits(dsa->q);
220 q_words = bn_get_top(dsa->q);
221 if (!bn_wexpand(k, q_words + 2)
222 || !bn_wexpand(l, q_words + 2))
223 goto err;
224
225 /* Get random k */
226 do {
227 if (dgst != NULL) {
228 /*
229 * We calculate k from SHA512(private_key + H(message) + random).
230 * This protects the private key from a weak PRNG.
231 */
232 if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
233 dlen, ctx))
234 goto err;
235 } else if (!BN_priv_rand_range(k, dsa->q))
236 goto err;
237 } while (BN_is_zero(k));
238
239 BN_set_flags(k, BN_FLG_CONSTTIME);
240 BN_set_flags(l, BN_FLG_CONSTTIME);
241
242 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
243 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
244 dsa->lock, dsa->p, ctx))
245 goto err;
246 }
247
248 /* Compute r = (g^k mod p) mod q */
249
250 /*
251 * We do not want timing information to leak the length of k, so we
252 * compute G^k using an equivalent scalar of fixed bit-length.
253 *
254 * We unconditionally perform both of these additions to prevent a
255 * small timing information leakage. We then choose the sum that is
256 * one bit longer than the modulus.
257 *
258 * There are some concerns about the efficacy of doing this. More
259 * specifically refer to the discussion starting with:
260 * https://github.com/openssl/openssl/pull/7486#discussion_r228323705
261 * The fix is to rework BN so these gymnastics aren't required.
262 */
263 if (!BN_add(l, k, dsa->q)
264 || !BN_add(k, l, dsa->q))
265 goto err;
266
267 BN_consttime_swap(BN_is_bit_set(l, q_bits), k, l, q_words + 2);
268
269 if ((dsa)->meth->bn_mod_exp != NULL) {
270 if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, k, dsa->p, ctx,
271 dsa->method_mont_p))
272 goto err;
273 } else {
274 if (!BN_mod_exp_mont(r, dsa->g, k, dsa->p, ctx, dsa->method_mont_p))
275 goto err;
276 }
277
278 if (!BN_mod(r, r, dsa->q, ctx))
279 goto err;
280
281 /* Compute part of 's = inv(k) (m + xr) mod q' */
282 if ((kinv = dsa_mod_inverse_fermat(k, dsa->q, ctx)) == NULL)
283 goto err;
284
285 BN_clear_free(*kinvp);
286 *kinvp = kinv;
287 kinv = NULL;
288 ret = 1;
289 err:
290 if (!ret)
291 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
292 if (ctx != ctx_in)
293 BN_CTX_free(ctx);
294 BN_clear_free(k);
295 BN_clear_free(l);
296 return ret;
297}
298
299static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
300 DSA_SIG *sig, DSA *dsa)
301{
302 BN_CTX *ctx;
303 BIGNUM *u1, *u2, *t1;
304 BN_MONT_CTX *mont = NULL;
305 const BIGNUM *r, *s;
306 int ret = -1, i;
307 if (!dsa->p || !dsa->q || !dsa->g) {
308 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
309 return -1;
310 }
311
312 i = BN_num_bits(dsa->q);
313 /* fips 186-3 allows only different sizes for q */
314 if (i != 160 && i != 224 && i != 256) {
315 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
316 return -1;
317 }
318
319 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
320 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
321 return -1;
322 }
323 u1 = BN_new();
324 u2 = BN_new();
325 t1 = BN_new();
326 ctx = BN_CTX_new();
327 if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
328 goto err;
329
330 DSA_SIG_get0(sig, &r, &s);
331
332 if (BN_is_zero(r) || BN_is_negative(r) ||
333 BN_ucmp(r, dsa->q) >= 0) {
334 ret = 0;
335 goto err;
336 }
337 if (BN_is_zero(s) || BN_is_negative(s) ||
338 BN_ucmp(s, dsa->q) >= 0) {
339 ret = 0;
340 goto err;
341 }
342
343 /*
344 * Calculate W = inv(S) mod Q save W in u2
345 */
346 if ((BN_mod_inverse(u2, s, dsa->q, ctx)) == NULL)
347 goto err;
348
349 /* save M in u1 */
350 if (dgst_len > (i >> 3))
351 /*
352 * if the digest length is greater than the size of q use the
353 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
354 * 4.2
355 */
356 dgst_len = (i >> 3);
357 if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
358 goto err;
359
360 /* u1 = M * w mod q */
361 if (!BN_mod_mul(u1, u1, u2, dsa->q, ctx))
362 goto err;
363
364 /* u2 = r * w mod q */
365 if (!BN_mod_mul(u2, r, u2, dsa->q, ctx))
366 goto err;
367
368 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
369 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
370 dsa->lock, dsa->p, ctx);
371 if (!mont)
372 goto err;
373 }
374
375 if (dsa->meth->dsa_mod_exp != NULL) {
376 if (!dsa->meth->dsa_mod_exp(dsa, t1, dsa->g, u1, dsa->pub_key, u2,
377 dsa->p, ctx, mont))
378 goto err;
379 } else {
380 if (!BN_mod_exp2_mont(t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
381 mont))
382 goto err;
383 }
384
385 /* let u1 = u1 mod q */
386 if (!BN_mod(u1, t1, dsa->q, ctx))
387 goto err;
388
389 /*
390 * V is now in u1. If the signature is correct, it will be equal to R.
391 */
392 ret = (BN_ucmp(u1, r) == 0);
393
394 err:
395 if (ret < 0)
396 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
397 BN_CTX_free(ctx);
398 BN_free(u1);
399 BN_free(u2);
400 BN_free(t1);
401 return ret;
402}
403
404static int dsa_init(DSA *dsa)
405{
406 dsa->flags |= DSA_FLAG_CACHE_MONT_P;
407 return 1;
408}
409
410static int dsa_finish(DSA *dsa)
411{
412 BN_MONT_CTX_free(dsa->method_mont_p);
413 return 1;
414}
415
416/*
417 * Compute the inverse of k modulo q.
418 * Since q is prime, Fermat's Little Theorem applies, which reduces this to
419 * mod-exp operation. Both the exponent and modulus are public information
420 * so a mod-exp that doesn't leak the base is sufficient. A newly allocated
421 * BIGNUM is returned which the caller must free.
422 */
423static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
424 BN_CTX *ctx)
425{
426 BIGNUM *res = NULL;
427 BIGNUM *r, *e;
428
429 if ((r = BN_new()) == NULL)
430 return NULL;
431
432 BN_CTX_start(ctx);
433 if ((e = BN_CTX_get(ctx)) != NULL
434 && BN_set_word(r, 2)
435 && BN_sub(e, q, r)
436 && BN_mod_exp_mont(r, k, e, q, ctx, NULL))
437 res = r;
438 else
439 BN_free(r);
440 BN_CTX_end(ctx);
441 return res;
442}
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