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source: vbox/trunk/src/libs/openssl-3.1.2/crypto/dh/dh_key.c@ 101021

Last change on this file since 101021 was 101021, checked in by vboxsync, 15 months ago

openssl-3.1.2: Applied and adjusted our OpenSSL changes to 3.1.0. bugref:10519
File size: 12.0 KB
Line 
1/*
2 * Copyright 1995-2022 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 * DH 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 "dh_local.h"
19#include "crypto/bn.h"
20#include "crypto/dh.h"
21#include "crypto/security_bits.h"
22
23#ifdef FIPS_MODULE
24# define MIN_STRENGTH 112
25#else
26# define MIN_STRENGTH 80
27#endif
28
29static int generate_key(DH *dh);
30static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
31 const BIGNUM *a, const BIGNUM *p,
32 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
33static int dh_init(DH *dh);
34static int dh_finish(DH *dh);
35
36/*
37 * See SP800-56Ar3 Section 5.7.1.1
38 * Finite Field Cryptography Diffie-Hellman (FFC DH) Primitive
39 */
40int ossl_dh_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
41{
42 BN_CTX *ctx = NULL;
43 BN_MONT_CTX *mont = NULL;
44 BIGNUM *z = NULL, *pminus1;
45 int ret = -1;
46
47 if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
48 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
49 goto err;
50 }
51
52 if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
53 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
54 return 0;
55 }
56
57 ctx = BN_CTX_new_ex(dh->libctx);
58 if (ctx == NULL)
59 goto err;
60 BN_CTX_start(ctx);
61 pminus1 = BN_CTX_get(ctx);
62 z = BN_CTX_get(ctx);
63 if (z == NULL)
64 goto err;
65
66 if (dh->priv_key == NULL) {
67 ERR_raise(ERR_LIB_DH, DH_R_NO_PRIVATE_VALUE);
68 goto err;
69 }
70
71 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
72 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
73 dh->lock, dh->params.p, ctx);
74 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
75 if (!mont)
76 goto err;
77 }
78
79 /* (Step 1) Z = pub_key^priv_key mod p */
80 if (!dh->meth->bn_mod_exp(dh, z, pub_key, dh->priv_key, dh->params.p, ctx,
81 mont)) {
82 ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
83 goto err;
84 }
85
86 /* (Step 2) Error if z <= 1 or z = p - 1 */
87 if (BN_copy(pminus1, dh->params.p) == NULL
88 || !BN_sub_word(pminus1, 1)
89 || BN_cmp(z, BN_value_one()) <= 0
90 || BN_cmp(z, pminus1) == 0) {
91 ERR_raise(ERR_LIB_DH, DH_R_INVALID_SECRET);
92 goto err;
93 }
94
95 /* return the padded key, i.e. same number of bytes as the modulus */
96 ret = BN_bn2binpad(z, key, BN_num_bytes(dh->params.p));
97 err:
98 BN_clear(z); /* (Step 2) destroy intermediate values */
99 BN_CTX_end(ctx);
100 BN_CTX_free(ctx);
101 return ret;
102}
103
104/*-
105 * NB: This function is inherently not constant time due to the
106 * RFC 5246 (8.1.2) padding style that strips leading zero bytes.
107 */
108int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
109{
110 int ret = 0, i;
111 volatile size_t npad = 0, mask = 1;
112
113 /* compute the key; ret is constant unless compute_key is external */
114#ifdef FIPS_MODULE
115 ret = ossl_dh_compute_key(key, pub_key, dh);
116#else
117 ret = dh->meth->compute_key(key, pub_key, dh);
118#endif
119 if (ret <= 0)
120 return ret;
121
122 /* count leading zero bytes, yet still touch all bytes */
123 for (i = 0; i < ret; i++) {
124 mask &= !key[i];
125 npad += mask;
126 }
127
128 /* unpad key */
129 ret -= npad;
130 /* key-dependent memory access, potentially leaking npad / ret */
131 memmove(key, key + npad, ret);
132 /* key-dependent memory access, potentially leaking npad / ret */
133 memset(key + ret, 0, npad);
134
135 return ret;
136}
137
138int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
139{
140 int rv, pad;
141
142 /* rv is constant unless compute_key is external */
143#ifdef FIPS_MODULE
144 rv = ossl_dh_compute_key(key, pub_key, dh);
145#else
146 rv = dh->meth->compute_key(key, pub_key, dh);
147#endif
148 if (rv <= 0)
149 return rv;
150 pad = BN_num_bytes(dh->params.p) - rv;
151 /* pad is constant (zero) unless compute_key is external */
152 if (pad > 0) {
153 memmove(key + pad, key, rv);
154 memset(key, 0, pad);
155 }
156 return rv + pad;
157}
158
159static DH_METHOD dh_ossl = {
160 "OpenSSL DH Method",
161 generate_key,
162 ossl_dh_compute_key,
163 dh_bn_mod_exp,
164 dh_init,
165 dh_finish,
166 DH_FLAG_FIPS_METHOD,
167 NULL,
168 NULL
169};
170
171static const DH_METHOD *default_DH_method = &dh_ossl;
172
173const DH_METHOD *DH_OpenSSL(void)
174{
175 return &dh_ossl;
176}
177
178const DH_METHOD *DH_get_default_method(void)
179{
180 return default_DH_method;
181}
182
183static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
184 const BIGNUM *a, const BIGNUM *p,
185 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
186{
187 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
188}
189
190static int dh_init(DH *dh)
191{
192 dh->flags |= DH_FLAG_CACHE_MONT_P;
193 ossl_ffc_params_init(&dh->params);
194 dh->dirty_cnt++;
195 return 1;
196}
197
198static int dh_finish(DH *dh)
199{
200 BN_MONT_CTX_free(dh->method_mont_p);
201 return 1;
202}
203
204#ifndef FIPS_MODULE
205void DH_set_default_method(const DH_METHOD *meth)
206{
207 default_DH_method = meth;
208}
209#endif /* FIPS_MODULE */
210
211int DH_generate_key(DH *dh)
212{
213#ifdef FIPS_MODULE
214 return generate_key(dh);
215#else
216 return dh->meth->generate_key(dh);
217#endif
218}
219
220int ossl_dh_generate_public_key(BN_CTX *ctx, const DH *dh,
221 const BIGNUM *priv_key, BIGNUM *pub_key)
222{
223 int ret = 0;
224 BIGNUM *prk = BN_new();
225 BN_MONT_CTX *mont = NULL;
226
227 if (prk == NULL)
228 return 0;
229
230 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
231 /*
232 * We take the input DH as const, but we lie, because in some cases we
233 * want to get a hold of its Montgomery context.
234 *
235 * We cast to remove the const qualifier in this case, it should be
236 * fine...
237 */
238 BN_MONT_CTX **pmont = (BN_MONT_CTX **)&dh->method_mont_p;
239
240 mont = BN_MONT_CTX_set_locked(pmont, dh->lock, dh->params.p, ctx);
241 if (mont == NULL)
242 goto err;
243 }
244 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
245
246 /* pub_key = g^priv_key mod p */
247 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->params.g, prk, dh->params.p,
248 ctx, mont))
249 goto err;
250 ret = 1;
251err:
252 BN_clear_free(prk);
253 return ret;
254}
255
256static int generate_key(DH *dh)
257{
258 int ok = 0;
259 int generate_new_key = 0;
260#ifndef FIPS_MODULE
261 unsigned l;
262#endif
263 BN_CTX *ctx = NULL;
264 BIGNUM *pub_key = NULL, *priv_key = NULL;
265
266 if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
267 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
268 return 0;
269 }
270
271 if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
272 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
273 return 0;
274 }
275
276 ctx = BN_CTX_new_ex(dh->libctx);
277 if (ctx == NULL)
278 goto err;
279
280 if (dh->priv_key == NULL) {
281 priv_key = BN_secure_new();
282 if (priv_key == NULL)
283 goto err;
284 generate_new_key = 1;
285 } else {
286 priv_key = dh->priv_key;
287 }
288
289 if (dh->pub_key == NULL) {
290 pub_key = BN_new();
291 if (pub_key == NULL)
292 goto err;
293 } else {
294 pub_key = dh->pub_key;
295 }
296 if (generate_new_key) {
297 /* Is it an approved safe prime ?*/
298 if (DH_get_nid(dh) != NID_undef) {
299 int max_strength =
300 ossl_ifc_ffc_compute_security_bits(BN_num_bits(dh->params.p));
301
302 if (dh->params.q == NULL
303 || dh->length > BN_num_bits(dh->params.q))
304 goto err;
305 /* dh->length = maximum bit length of generated private key */
306 if (!ossl_ffc_generate_private_key(ctx, &dh->params, dh->length,
307 max_strength, priv_key))
308 goto err;
309 } else {
310#ifdef FIPS_MODULE
311 if (dh->params.q == NULL)
312 goto err;
313#else
314 if (dh->params.q == NULL) {
315 /* secret exponent length, must satisfy 2^(l-1) <= p */
316 if (dh->length != 0
317 && dh->length >= BN_num_bits(dh->params.p))
318 goto err;
319 l = dh->length ? dh->length : BN_num_bits(dh->params.p) - 1;
320 if (!BN_priv_rand_ex(priv_key, l, BN_RAND_TOP_ONE,
321 BN_RAND_BOTTOM_ANY, 0, ctx))
322 goto err;
323 /*
324 * We handle just one known case where g is a quadratic non-residue:
325 * for g = 2: p % 8 == 3
326 */
327 if (BN_is_word(dh->params.g, DH_GENERATOR_2)
328 && !BN_is_bit_set(dh->params.p, 2)) {
329 /* clear bit 0, since it won't be a secret anyway */
330 if (!BN_clear_bit(priv_key, 0))
331 goto err;
332 }
333 } else
334#endif
335 {
336 /* Do a partial check for invalid p, q, g */
337 if (!ossl_ffc_params_simple_validate(dh->libctx, &dh->params,
338 FFC_PARAM_TYPE_DH, NULL))
339 goto err;
340 /*
341 * For FFC FIPS 186-4 keygen
342 * security strength s = 112,
343 * Max Private key size N = len(q)
344 */
345 if (!ossl_ffc_generate_private_key(ctx, &dh->params,
346 BN_num_bits(dh->params.q),
347 MIN_STRENGTH,
348 priv_key))
349 goto err;
350 }
351 }
352 }
353
354 if (!ossl_dh_generate_public_key(ctx, dh, priv_key, pub_key))
355 goto err;
356
357 dh->pub_key = pub_key;
358 dh->priv_key = priv_key;
359 dh->dirty_cnt++;
360 ok = 1;
361 err:
362 if (ok != 1)
363 ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
364
365 if (pub_key != dh->pub_key)
366 BN_free(pub_key);
367 if (priv_key != dh->priv_key)
368 BN_free(priv_key);
369 BN_CTX_free(ctx);
370 return ok;
371}
372
373int ossl_dh_buf2key(DH *dh, const unsigned char *buf, size_t len)
374{
375 int err_reason = DH_R_BN_ERROR;
376 BIGNUM *pubkey = NULL;
377 const BIGNUM *p;
378 int ret;
379
380 if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL)
381 goto err;
382 DH_get0_pqg(dh, &p, NULL, NULL);
383 if (p == NULL || BN_num_bytes(p) == 0) {
384 err_reason = DH_R_NO_PARAMETERS_SET;
385 goto err;
386 }
387 /* Prevent small subgroup attacks per RFC 8446 Section 4.2.8.1 */
388 if (!ossl_dh_check_pub_key_partial(dh, pubkey, &ret)) {
389 err_reason = DH_R_INVALID_PUBKEY;
390 goto err;
391 }
392 if (DH_set0_key(dh, pubkey, NULL) != 1)
393 goto err;
394 return 1;
395err:
396 ERR_raise(ERR_LIB_DH, err_reason);
397 BN_free(pubkey);
398 return 0;
399}
400
401size_t ossl_dh_key2buf(const DH *dh, unsigned char **pbuf_out, size_t size,
402 int alloc)
403{
404 const BIGNUM *pubkey;
405 unsigned char *pbuf = NULL;
406 const BIGNUM *p;
407 int p_size;
408
409 DH_get0_pqg(dh, &p, NULL, NULL);
410 DH_get0_key(dh, &pubkey, NULL);
411 if (p == NULL || pubkey == NULL
412 || (p_size = BN_num_bytes(p)) == 0
413 || BN_num_bytes(pubkey) == 0) {
414 ERR_raise(ERR_LIB_DH, DH_R_INVALID_PUBKEY);
415 return 0;
416 }
417 if (pbuf_out != NULL && (alloc || *pbuf_out != NULL)) {
418 if (!alloc) {
419 if (size >= (size_t)p_size)
420 pbuf = *pbuf_out;
421 } else {
422 pbuf = OPENSSL_malloc(p_size);
423 }
424
425 if (pbuf == NULL) {
426 ERR_raise(ERR_LIB_DH, ERR_R_MALLOC_FAILURE);
427 return 0;
428 }
429 /*
430 * As per Section 4.2.8.1 of RFC 8446 left pad public
431 * key with zeros to the size of p
432 */
433 if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) {
434 if (alloc)
435 OPENSSL_free(pbuf);
436 ERR_raise(ERR_LIB_DH, DH_R_BN_ERROR);
437 return 0;
438 }
439 *pbuf_out = pbuf;
440 }
441 return p_size;
442}
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