1 /*
2 * Copyright 1995-2024 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 <openssl/bn.h>
19 #include "dh_local.h"
20 #include "crypto/dh.h"
21
22 /*-
23 * Check that p and g are suitable enough
24 *
25 * p is odd
26 * 1 < g < p - 1
27 */
DH_check_params_ex(const DH * dh)28 int DH_check_params_ex(const DH *dh)
29 {
30 int errflags = 0;
31
32 if (!DH_check_params(dh, &errflags))
33 return 0;
34
35 if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
36 ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);
37 if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
38 ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
39 if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
40 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
41 if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
42 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
43
44 return errflags == 0;
45 }
46
47 #ifdef FIPS_MODULE
DH_check_params(const DH * dh,int * ret)48 int DH_check_params(const DH *dh, int *ret)
49 {
50 int nid;
51
52 *ret = 0;
53 /*
54 * SP800-56A R3 Section 5.5.2 Assurances of Domain Parameter Validity
55 * (1a) The domain parameters correspond to any approved safe prime group.
56 */
57 nid = DH_get_nid((DH *)dh);
58 if (nid != NID_undef)
59 return 1;
60 /*
61 * OR
62 * (2b) FFC domain params conform to FIPS-186-4 explicit domain param
63 * validity tests.
64 */
65 return ossl_ffc_params_FIPS186_4_validate(dh->libctx, &dh->params,
66 FFC_PARAM_TYPE_DH, ret, NULL);
67 }
68 #else
DH_check_params(const DH * dh,int * ret)69 int DH_check_params(const DH *dh, int *ret)
70 {
71 int ok = 0;
72 BIGNUM *tmp = NULL;
73 BN_CTX *ctx = NULL;
74
75 *ret = 0;
76 ctx = BN_CTX_new_ex(dh->libctx);
77 if (ctx == NULL)
78 goto err;
79 BN_CTX_start(ctx);
80 tmp = BN_CTX_get(ctx);
81 if (tmp == NULL)
82 goto err;
83
84 if (!BN_is_odd(dh->params.p))
85 *ret |= DH_CHECK_P_NOT_PRIME;
86 if (BN_is_negative(dh->params.g)
87 || BN_is_zero(dh->params.g)
88 || BN_is_one(dh->params.g))
89 *ret |= DH_NOT_SUITABLE_GENERATOR;
90 if (BN_copy(tmp, dh->params.p) == NULL || !BN_sub_word(tmp, 1))
91 goto err;
92 if (BN_cmp(dh->params.g, tmp) >= 0)
93 *ret |= DH_NOT_SUITABLE_GENERATOR;
94 if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS)
95 *ret |= DH_MODULUS_TOO_SMALL;
96 if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS)
97 *ret |= DH_MODULUS_TOO_LARGE;
98
99 ok = 1;
100 err:
101 BN_CTX_end(ctx);
102 BN_CTX_free(ctx);
103 return ok;
104 }
105 #endif /* FIPS_MODULE */
106
107 /*-
108 * Check that p is a safe prime and
109 * g is a suitable generator.
110 */
DH_check_ex(const DH * dh)111 int DH_check_ex(const DH *dh)
112 {
113 int errflags = 0;
114
115 if (!DH_check(dh, &errflags))
116 return 0;
117
118 if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
119 ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
120 if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
121 ERR_raise(ERR_LIB_DH, DH_R_CHECK_Q_NOT_PRIME);
122 if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
123 ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_Q_VALUE);
124 if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
125 ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_J_VALUE);
126 if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
127 ERR_raise(ERR_LIB_DH, DH_R_UNABLE_TO_CHECK_GENERATOR);
128 if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
129 ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);
130 if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
131 ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_SAFE_PRIME);
132 if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
133 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
134 if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
135 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
136
137 return errflags == 0;
138 }
139
140 /* Note: according to documentation - this only checks the params */
DH_check(const DH * dh,int * ret)141 int DH_check(const DH *dh, int *ret)
142 {
143 #ifdef FIPS_MODULE
144 return DH_check_params(dh, ret);
145 #else
146 int ok = 0, r, q_good = 0;
147 BN_CTX *ctx = NULL;
148 BIGNUM *t1 = NULL, *t2 = NULL;
149 int nid = DH_get_nid((DH *)dh);
150
151 *ret = 0;
152 if (nid != NID_undef)
153 return 1;
154
155 /* Don't do any checks at all with an excessively large modulus */
156 if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
157 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
158 *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_P_NOT_PRIME;
159 return 0;
160 }
161
162 if (!DH_check_params(dh, ret))
163 return 0;
164
165 ctx = BN_CTX_new_ex(dh->libctx);
166 if (ctx == NULL)
167 goto err;
168 BN_CTX_start(ctx);
169 t1 = BN_CTX_get(ctx);
170 t2 = BN_CTX_get(ctx);
171 if (t2 == NULL)
172 goto err;
173
174 if (dh->params.q != NULL) {
175 if (BN_ucmp(dh->params.p, dh->params.q) > 0)
176 q_good = 1;
177 else
178 *ret |= DH_CHECK_INVALID_Q_VALUE;
179 }
180
181 if (q_good) {
182 if (BN_cmp(dh->params.g, BN_value_one()) <= 0)
183 *ret |= DH_NOT_SUITABLE_GENERATOR;
184 else if (BN_cmp(dh->params.g, dh->params.p) >= 0)
185 *ret |= DH_NOT_SUITABLE_GENERATOR;
186 else {
187 /* Check g^q == 1 mod p */
188 if (!BN_mod_exp(t1, dh->params.g, dh->params.q, dh->params.p, ctx))
189 goto err;
190 if (!BN_is_one(t1))
191 *ret |= DH_NOT_SUITABLE_GENERATOR;
192 }
193 r = BN_check_prime(dh->params.q, ctx, NULL);
194 if (r < 0)
195 goto err;
196 if (!r)
197 *ret |= DH_CHECK_Q_NOT_PRIME;
198 /* Check p == 1 mod q i.e. q divides p - 1 */
199 if (!BN_div(t1, t2, dh->params.p, dh->params.q, ctx))
200 goto err;
201 if (!BN_is_one(t2))
202 *ret |= DH_CHECK_INVALID_Q_VALUE;
203 if (dh->params.j != NULL
204 && BN_cmp(dh->params.j, t1))
205 *ret |= DH_CHECK_INVALID_J_VALUE;
206 }
207
208 r = BN_check_prime(dh->params.p, ctx, NULL);
209 if (r < 0)
210 goto err;
211 if (!r)
212 *ret |= DH_CHECK_P_NOT_PRIME;
213 else if (dh->params.q == NULL) {
214 if (!BN_rshift1(t1, dh->params.p))
215 goto err;
216 r = BN_check_prime(t1, ctx, NULL);
217 if (r < 0)
218 goto err;
219 if (!r)
220 *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
221 }
222 ok = 1;
223 err:
224 BN_CTX_end(ctx);
225 BN_CTX_free(ctx);
226 return ok;
227 #endif /* FIPS_MODULE */
228 }
229
DH_check_pub_key_ex(const DH * dh,const BIGNUM * pub_key)230 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
231 {
232 int errflags = 0;
233
234 if (!DH_check_pub_key(dh, pub_key, &errflags))
235 return 0;
236
237 if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
238 ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_SMALL);
239 if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
240 ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_LARGE);
241 if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
242 ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_INVALID);
243
244 return errflags == 0;
245 }
246
247 /*
248 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
249 */
DH_check_pub_key(const DH * dh,const BIGNUM * pub_key,int * ret)250 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
251 {
252 /* Don't do any checks at all with an excessively large modulus */
253 if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
254 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
255 *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID;
256 return 0;
257 }
258
259 if (dh->params.q != NULL && BN_ucmp(dh->params.p, dh->params.q) < 0) {
260 *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID;
261 return 1;
262 }
263
264 return ossl_ffc_validate_public_key(&dh->params, pub_key, ret);
265 }
266
267 /*
268 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
269 * To only be used with ephemeral FFC public keys generated using the approved
270 * safe-prime groups.
271 */
ossl_dh_check_pub_key_partial(const DH * dh,const BIGNUM * pub_key,int * ret)272 int ossl_dh_check_pub_key_partial(const DH *dh, const BIGNUM *pub_key, int *ret)
273 {
274 return ossl_ffc_validate_public_key_partial(&dh->params, pub_key, ret)
275 && *ret == 0;
276 }
277
ossl_dh_check_priv_key(const DH * dh,const BIGNUM * priv_key,int * ret)278 int ossl_dh_check_priv_key(const DH *dh, const BIGNUM *priv_key, int *ret)
279 {
280 int ok = 0;
281 BIGNUM *two_powN = NULL, *upper;
282
283 *ret = 0;
284 two_powN = BN_new();
285 if (two_powN == NULL)
286 return 0;
287
288 if (dh->params.q != NULL) {
289 upper = dh->params.q;
290 #ifndef FIPS_MODULE
291 } else if (dh->params.p != NULL) {
292 /*
293 * We do not have q so we just check the key is within some
294 * reasonable range, or the number of bits is equal to dh->length.
295 */
296 int length = dh->length;
297
298 if (length == 0) {
299 length = BN_num_bits(dh->params.p) - 1;
300 if (BN_num_bits(priv_key) <= length
301 && BN_num_bits(priv_key) > 1)
302 ok = 1;
303 } else if (BN_num_bits(priv_key) == length) {
304 ok = 1;
305 }
306 goto end;
307 #endif
308 } else {
309 goto end;
310 }
311
312 /* Is it from an approved Safe prime group ?*/
313 if (DH_get_nid((DH *)dh) != NID_undef && dh->length != 0) {
314 if (!BN_lshift(two_powN, BN_value_one(), dh->length))
315 goto end;
316 if (BN_cmp(two_powN, dh->params.q) < 0)
317 upper = two_powN;
318 }
319 if (!ossl_ffc_validate_private_key(upper, priv_key, ret))
320 goto end;
321
322 ok = 1;
323 end:
324 BN_free(two_powN);
325 return ok;
326 }
327
328 /*
329 * FFC pairwise check from SP800-56A R3.
330 * Section 5.6.2.1.4 Owner Assurance of Pair-wise Consistency
331 */
ossl_dh_check_pairwise(const DH * dh)332 int ossl_dh_check_pairwise(const DH *dh)
333 {
334 int ret = 0;
335 BN_CTX *ctx = NULL;
336 BIGNUM *pub_key = NULL;
337
338 if (dh->params.p == NULL
339 || dh->params.g == NULL
340 || dh->priv_key == NULL
341 || dh->pub_key == NULL)
342 return 0;
343
344 ctx = BN_CTX_new_ex(dh->libctx);
345 if (ctx == NULL)
346 goto err;
347 pub_key = BN_new();
348 if (pub_key == NULL)
349 goto err;
350
351 /* recalculate the public key = (g ^ priv) mod p */
352 if (!ossl_dh_generate_public_key(ctx, dh, dh->priv_key, pub_key))
353 goto err;
354 /* check it matches the existing public_key */
355 ret = BN_cmp(pub_key, dh->pub_key) == 0;
356 err:
357 BN_free(pub_key);
358 BN_CTX_free(ctx);
359 return ret;
360 }
361
