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source: vbox/trunk/src/libs/openssl-3.0.7/crypto/dsa/dsa_ossl.c@ 98929

Last change on this file since 98929 was 94082, checked in by vboxsync, 3 years ago

libs/openssl-3.0.1: started applying and adjusting our OpenSSL changes to 3.0.1. bugref:10128
File size: 12.8 KB
Line 
1/*
2 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (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/*
11 * DSA low level APIs are deprecated for public use, but still ok for
12 * internal use.
13 */
14#include "internal/deprecated.h"
15
16#include <stdio.h>
17#include "internal/cryptlib.h"
18#include "crypto/bn.h"
19#include <openssl/bn.h>
20#include <openssl/sha.h>
21#include "dsa_local.h"
22#include <openssl/asn1.h>
23
24static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
25static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
26 BIGNUM **rp);
27static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
28 BIGNUM **rp, const unsigned char *dgst, int dlen);
29static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
30 DSA_SIG *sig, DSA *dsa);
31static int dsa_init(DSA *dsa);
32static int dsa_finish(DSA *dsa);
33static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
34 BN_CTX *ctx);
35
36static DSA_METHOD openssl_dsa_meth = {
37 "OpenSSL DSA method",
38 dsa_do_sign,
39 dsa_sign_setup_no_digest,
40 dsa_do_verify,
41 NULL, /* dsa_mod_exp, */
42 NULL, /* dsa_bn_mod_exp, */
43 dsa_init,
44 dsa_finish,
45 DSA_FLAG_FIPS_METHOD,
46 NULL,
47 NULL,
48 NULL
49};
50
51static const DSA_METHOD *default_DSA_method = &openssl_dsa_meth;
52
53#ifndef FIPS_MODULE
54void DSA_set_default_method(const DSA_METHOD *meth)
55{
56 default_DSA_method = meth;
57}
58#endif /* FIPS_MODULE */
59
60const DSA_METHOD *DSA_get_default_method(void)
61{
62 return default_DSA_method;
63}
64
65const DSA_METHOD *DSA_OpenSSL(void)
66{
67 return &openssl_dsa_meth;
68}
69
70DSA_SIG *ossl_dsa_do_sign_int(const unsigned char *dgst, int dlen, DSA *dsa)
71{
72 BIGNUM *kinv = NULL;
73 BIGNUM *m, *blind, *blindm, *tmp;
74 BN_CTX *ctx = NULL;
75 int reason = ERR_R_BN_LIB;
76 DSA_SIG *ret = NULL;
77 int rv = 0;
78
79 if (dsa->params.p == NULL
80 || dsa->params.q == NULL
81 || dsa->params.g == NULL) {
82 reason = DSA_R_MISSING_PARAMETERS;
83 goto err;
84 }
85 if (dsa->priv_key == NULL) {
86 reason = DSA_R_MISSING_PRIVATE_KEY;
87 goto err;
88 }
89
90 ret = DSA_SIG_new();
91 if (ret == NULL)
92 goto err;
93 ret->r = BN_new();
94 ret->s = BN_new();
95 if (ret->r == NULL || ret->s == NULL)
96 goto err;
97
98 ctx = BN_CTX_new_ex(dsa->libctx);
99 if (ctx == NULL)
100 goto err;
101 m = BN_CTX_get(ctx);
102 blind = BN_CTX_get(ctx);
103 blindm = BN_CTX_get(ctx);
104 tmp = BN_CTX_get(ctx);
105 if (tmp == NULL)
106 goto err;
107
108 redo:
109 if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen))
110 goto err;
111
112 if (dlen > BN_num_bytes(dsa->params.q))
113 /*
114 * if the digest length is greater than the size of q use the
115 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
116 * 4.2
117 */
118 dlen = BN_num_bytes(dsa->params.q);
119 if (BN_bin2bn(dgst, dlen, m) == NULL)
120 goto err;
121
122 /*
123 * The normal signature calculation is:
124 *
125 * s := k^-1 * (m + r * priv_key) mod q
126 *
127 * We will blind this to protect against side channel attacks
128 *
129 * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q
130 */
131
132 /* Generate a blinding value */
133 do {
134 if (!BN_priv_rand_ex(blind, BN_num_bits(dsa->params.q) - 1,
135 BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, 0, ctx))
136 goto err;
137 } while (BN_is_zero(blind));
138 BN_set_flags(blind, BN_FLG_CONSTTIME);
139 BN_set_flags(blindm, BN_FLG_CONSTTIME);
140 BN_set_flags(tmp, BN_FLG_CONSTTIME);
141
142 /* tmp := blind * priv_key * r mod q */
143 if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->params.q, ctx))
144 goto err;
145 if (!BN_mod_mul(tmp, tmp, ret->r, dsa->params.q, ctx))
146 goto err;
147
148 /* blindm := blind * m mod q */
149 if (!BN_mod_mul(blindm, blind, m, dsa->params.q, ctx))
150 goto err;
151
152 /* s : = (blind * priv_key * r) + (blind * m) mod q */
153 if (!BN_mod_add_quick(ret->s, tmp, blindm, dsa->params.q))
154 goto err;
155
156 /* s := s * k^-1 mod q */
157 if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->params.q, ctx))
158 goto err;
159
160 /* s:= s * blind^-1 mod q */
161 if (BN_mod_inverse(blind, blind, dsa->params.q, ctx) == NULL)
162 goto err;
163 if (!BN_mod_mul(ret->s, ret->s, blind, dsa->params.q, ctx))
164 goto err;
165
166 /*
167 * Redo if r or s is zero as required by FIPS 186-3: this is very
168 * unlikely.
169 */
170 if (BN_is_zero(ret->r) || BN_is_zero(ret->s))
171 goto redo;
172
173 rv = 1;
174
175 err:
176 if (rv == 0) {
177 ERR_raise(ERR_LIB_DSA, reason);
178 DSA_SIG_free(ret);
179 ret = NULL;
180 }
181 BN_CTX_free(ctx);
182 BN_clear_free(kinv);
183 return ret;
184}
185
186static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
187{
188 return ossl_dsa_do_sign_int(dgst, dlen, dsa);
189}
190
191static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
192 BIGNUM **kinvp, BIGNUM **rp)
193{
194 return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
195}
196
197static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
198 BIGNUM **kinvp, BIGNUM **rp,
199 const unsigned char *dgst, int dlen)
200{
201 BN_CTX *ctx = NULL;
202 BIGNUM *k, *kinv = NULL, *r = *rp;
203 BIGNUM *l;
204 int ret = 0;
205 int q_bits, q_words;
206
207 if (!dsa->params.p || !dsa->params.q || !dsa->params.g) {
208 ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PARAMETERS);
209 return 0;
210 }
211
212 /* Reject obviously invalid parameters */
213 if (BN_is_zero(dsa->params.p)
214 || BN_is_zero(dsa->params.q)
215 || BN_is_zero(dsa->params.g)) {
216 ERR_raise(ERR_LIB_DSA, DSA_R_INVALID_PARAMETERS);
217 return 0;
218 }
219 if (dsa->priv_key == NULL) {
220 ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PRIVATE_KEY);
221 return 0;
222 }
223
224 k = BN_new();
225 l = BN_new();
226 if (k == NULL || l == NULL)
227 goto err;
228
229 if (ctx_in == NULL) {
230 /* if you don't pass in ctx_in you get a default libctx */
231 if ((ctx = BN_CTX_new_ex(NULL)) == NULL)
232 goto err;
233 } else
234 ctx = ctx_in;
235
236 /* Preallocate space */
237 q_bits = BN_num_bits(dsa->params.q);
238 q_words = bn_get_top(dsa->params.q);
239 if (!bn_wexpand(k, q_words + 2)
240 || !bn_wexpand(l, q_words + 2))
241 goto err;
242
243 /* Get random k */
244 do {
245 if (dgst != NULL) {
246 /*
247 * We calculate k from SHA512(private_key + H(message) + random).
248 * This protects the private key from a weak PRNG.
249 */
250 if (!BN_generate_dsa_nonce(k, dsa->params.q, dsa->priv_key, dgst,
251 dlen, ctx))
252 goto err;
253 } else if (!BN_priv_rand_range_ex(k, dsa->params.q, 0, ctx))
254 goto err;
255 } while (BN_is_zero(k));
256
257 BN_set_flags(k, BN_FLG_CONSTTIME);
258 BN_set_flags(l, BN_FLG_CONSTTIME);
259
260 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
261 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
262 dsa->lock, dsa->params.p, ctx))
263 goto err;
264 }
265
266 /* Compute r = (g^k mod p) mod q */
267
268 /*
269 * We do not want timing information to leak the length of k, so we
270 * compute G^k using an equivalent scalar of fixed bit-length.
271 *
272 * We unconditionally perform both of these additions to prevent a
273 * small timing information leakage. We then choose the sum that is
274 * one bit longer than the modulus.
275 *
276 * There are some concerns about the efficacy of doing this. More
277 * specifically refer to the discussion starting with:
278 * https://github.com/openssl/openssl/pull/7486#discussion_r228323705
279 * The fix is to rework BN so these gymnastics aren't required.
280 */
281 if (!BN_add(l, k, dsa->params.q)
282 || !BN_add(k, l, dsa->params.q))
283 goto err;
284
285 BN_consttime_swap(BN_is_bit_set(l, q_bits), k, l, q_words + 2);
286
287 if ((dsa)->meth->bn_mod_exp != NULL) {
288 if (!dsa->meth->bn_mod_exp(dsa, r, dsa->params.g, k, dsa->params.p,
289 ctx, dsa->method_mont_p))
290 goto err;
291 } else {
292 if (!BN_mod_exp_mont(r, dsa->params.g, k, dsa->params.p, ctx,
293 dsa->method_mont_p))
294 goto err;
295 }
296
297 if (!BN_mod(r, r, dsa->params.q, ctx))
298 goto err;
299
300 /* Compute part of 's = inv(k) (m + xr) mod q' */
301 if ((kinv = dsa_mod_inverse_fermat(k, dsa->params.q, ctx)) == NULL)
302 goto err;
303
304 BN_clear_free(*kinvp);
305 *kinvp = kinv;
306 kinv = NULL;
307 ret = 1;
308 err:
309 if (!ret)
310 ERR_raise(ERR_LIB_DSA, ERR_R_BN_LIB);
311 if (ctx != ctx_in)
312 BN_CTX_free(ctx);
313 BN_clear_free(k);
314 BN_clear_free(l);
315 return ret;
316}
317
318static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
319 DSA_SIG *sig, DSA *dsa)
320{
321 BN_CTX *ctx;
322 BIGNUM *u1, *u2, *t1;
323 BN_MONT_CTX *mont = NULL;
324 const BIGNUM *r, *s;
325 int ret = -1, i;
326
327 if (dsa->params.p == NULL
328 || dsa->params.q == NULL
329 || dsa->params.g == NULL) {
330 ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PARAMETERS);
331 return -1;
332 }
333
334 i = BN_num_bits(dsa->params.q);
335 /* fips 186-3 allows only different sizes for q */
336 if (i != 160 && i != 224 && i != 256) {
337 ERR_raise(ERR_LIB_DSA, DSA_R_BAD_Q_VALUE);
338 return -1;
339 }
340
341 if (BN_num_bits(dsa->params.p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
342 ERR_raise(ERR_LIB_DSA, DSA_R_MODULUS_TOO_LARGE);
343 return -1;
344 }
345 u1 = BN_new();
346 u2 = BN_new();
347 t1 = BN_new();
348 ctx = BN_CTX_new_ex(NULL); /* verify does not need a libctx */
349 if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
350 goto err;
351
352 DSA_SIG_get0(sig, &r, &s);
353
354 if (BN_is_zero(r) || BN_is_negative(r) ||
355 BN_ucmp(r, dsa->params.q) >= 0) {
356 ret = 0;
357 goto err;
358 }
359 if (BN_is_zero(s) || BN_is_negative(s) ||
360 BN_ucmp(s, dsa->params.q) >= 0) {
361 ret = 0;
362 goto err;
363 }
364
365 /*
366 * Calculate W = inv(S) mod Q save W in u2
367 */
368 if ((BN_mod_inverse(u2, s, dsa->params.q, ctx)) == NULL)
369 goto err;
370
371 /* save M in u1 */
372 if (dgst_len > (i >> 3))
373 /*
374 * if the digest length is greater than the size of q use the
375 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
376 * 4.2
377 */
378 dgst_len = (i >> 3);
379 if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
380 goto err;
381
382 /* u1 = M * w mod q */
383 if (!BN_mod_mul(u1, u1, u2, dsa->params.q, ctx))
384 goto err;
385
386 /* u2 = r * w mod q */
387 if (!BN_mod_mul(u2, r, u2, dsa->params.q, ctx))
388 goto err;
389
390 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
391 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
392 dsa->lock, dsa->params.p, ctx);
393 if (!mont)
394 goto err;
395 }
396
397 if (dsa->meth->dsa_mod_exp != NULL) {
398 if (!dsa->meth->dsa_mod_exp(dsa, t1, dsa->params.g, u1, dsa->pub_key, u2,
399 dsa->params.p, ctx, mont))
400 goto err;
401 } else {
402 if (!BN_mod_exp2_mont(t1, dsa->params.g, u1, dsa->pub_key, u2,
403 dsa->params.p, ctx, mont))
404 goto err;
405 }
406
407 /* let u1 = u1 mod q */
408 if (!BN_mod(u1, t1, dsa->params.q, ctx))
409 goto err;
410
411 /*
412 * V is now in u1. If the signature is correct, it will be equal to R.
413 */
414 ret = (BN_ucmp(u1, r) == 0);
415
416 err:
417 if (ret < 0)
418 ERR_raise(ERR_LIB_DSA, ERR_R_BN_LIB);
419 BN_CTX_free(ctx);
420 BN_free(u1);
421 BN_free(u2);
422 BN_free(t1);
423 return ret;
424}
425
426static int dsa_init(DSA *dsa)
427{
428 dsa->flags |= DSA_FLAG_CACHE_MONT_P;
429 ossl_ffc_params_init(&dsa->params);
430 dsa->dirty_cnt++;
431 return 1;
432}
433
434static int dsa_finish(DSA *dsa)
435{
436 BN_MONT_CTX_free(dsa->method_mont_p);
437 return 1;
438}
439
440/*
441 * Compute the inverse of k modulo q.
442 * Since q is prime, Fermat's Little Theorem applies, which reduces this to
443 * mod-exp operation. Both the exponent and modulus are public information
444 * so a mod-exp that doesn't leak the base is sufficient. A newly allocated
445 * BIGNUM is returned which the caller must free.
446 */
447static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
448 BN_CTX *ctx)
449{
450 BIGNUM *res = NULL;
451 BIGNUM *r, *e;
452
453 if ((r = BN_new()) == NULL)
454 return NULL;
455
456 BN_CTX_start(ctx);
457 if ((e = BN_CTX_get(ctx)) != NULL
458 && BN_set_word(r, 2)
459 && BN_sub(e, q, r)
460 && BN_mod_exp_mont(r, k, e, q, ctx, NULL))
461 res = r;
462 else
463 BN_free(r);
464 BN_CTX_end(ctx);
465 return res;
466}
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