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 * NB: These functions have been upgraded - the previous prototypes are in
12 * dh_depr.c as wrappers to these ones. - Geoff
13 */
14
15 /*
16 * DH low level APIs are deprecated for public use, but still ok for
17 * internal use.
18 *
19 * NOTE: When generating keys for key-agreement schemes - FIPS 140-2 IG 9.9
20 * states that no additional pairwise tests are required (apart from the tests
21 * specified in SP800-56A) when generating keys. Hence DH pairwise tests are
22 * omitted here.
23 */
24 #include "internal/deprecated.h"
25
26 #include <stdio.h>
27 #include "internal/cryptlib.h"
28 #include <openssl/bn.h>
29 #include <openssl/sha.h>
30 #include "crypto/dh.h"
31 #include "dh_local.h"
32
33 #ifndef FIPS_MODULE
34 static int dh_builtin_genparams(DH *ret, int prime_len, int generator,
35 BN_GENCB *cb);
36 #endif /* FIPS_MODULE */
37
ossl_dh_generate_ffc_parameters(DH * dh,int type,int pbits,int qbits,BN_GENCB * cb)38 int ossl_dh_generate_ffc_parameters(DH *dh, int type, int pbits, int qbits,
39 BN_GENCB *cb)
40 {
41 int ret, res;
42
43 #ifndef FIPS_MODULE
44 if (type == DH_PARAMGEN_TYPE_FIPS_186_2)
45 ret = ossl_ffc_params_FIPS186_2_generate(dh->libctx, &dh->params,
46 FFC_PARAM_TYPE_DH,
47 pbits, qbits, &res, cb);
48 else
49 #endif
50 ret = ossl_ffc_params_FIPS186_4_generate(dh->libctx, &dh->params,
51 FFC_PARAM_TYPE_DH,
52 pbits, qbits, &res, cb);
53 if (ret > 0)
54 dh->dirty_cnt++;
55 return ret;
56 }
57
ossl_dh_get_named_group_uid_from_size(int pbits)58 int ossl_dh_get_named_group_uid_from_size(int pbits)
59 {
60 /*
61 * Just choose an approved safe prime group.
62 * The alternative to this is to generate FIPS186-4 domain parameters i.e.
63 * return dh_generate_ffc_parameters(ret, prime_len, 0, NULL, cb);
64 * As the FIPS186-4 generated params are for backwards compatibility,
65 * the safe prime group should be used as the default.
66 */
67 int nid;
68
69 switch (pbits) {
70 case 2048:
71 nid = NID_ffdhe2048;
72 break;
73 case 3072:
74 nid = NID_ffdhe3072;
75 break;
76 case 4096:
77 nid = NID_ffdhe4096;
78 break;
79 case 6144:
80 nid = NID_ffdhe6144;
81 break;
82 case 8192:
83 nid = NID_ffdhe8192;
84 break;
85 /* unsupported prime_len */
86 default:
87 return NID_undef;
88 }
89 return nid;
90 }
91
92 #ifdef FIPS_MODULE
93
dh_gen_named_group(OSSL_LIB_CTX * libctx,DH * ret,int prime_len)94 static int dh_gen_named_group(OSSL_LIB_CTX *libctx, DH *ret, int prime_len)
95 {
96 DH *dh;
97 int ok = 0;
98 int nid = ossl_dh_get_named_group_uid_from_size(prime_len);
99
100 if (nid == NID_undef)
101 return 0;
102
103 dh = ossl_dh_new_by_nid_ex(libctx, nid);
104 if (dh != NULL
105 && ossl_ffc_params_copy(&ret->params, &dh->params)) {
106 ok = 1;
107 ret->dirty_cnt++;
108 }
109 DH_free(dh);
110 return ok;
111 }
112 #endif /* FIPS_MODULE */
113
DH_generate_parameters_ex(DH * ret,int prime_len,int generator,BN_GENCB * cb)114 int DH_generate_parameters_ex(DH *ret, int prime_len, int generator,
115 BN_GENCB *cb)
116 {
117 #ifdef FIPS_MODULE
118 if (generator != 2)
119 return 0;
120 return dh_gen_named_group(ret->libctx, ret, prime_len);
121 #else
122 if (ret->meth->generate_params)
123 return ret->meth->generate_params(ret, prime_len, generator, cb);
124 return dh_builtin_genparams(ret, prime_len, generator, cb);
125 #endif /* FIPS_MODULE */
126 }
127
128 #ifndef FIPS_MODULE
129 /*-
130 * We generate DH parameters as follows
131 * find a prime p which is prime_len bits long,
132 * where q=(p-1)/2 is also prime.
133 * In the following we assume that g is not 0, 1 or p-1, since it
134 * would generate only trivial subgroups.
135 * For this case, g is a generator of the order-q subgroup if
136 * g^q mod p == 1.
137 * Or in terms of the Legendre symbol: (g/p) == 1.
138 *
139 * Having said all that,
140 * there is another special case method for the generators 2, 3 and 5.
141 * Using the quadratic reciprocity law it is possible to solve
142 * (g/p) == 1 for the special values 2, 3, 5:
143 * (2/p) == 1 if p mod 8 == 1 or 7.
144 * (3/p) == 1 if p mod 12 == 1 or 11.
145 * (5/p) == 1 if p mod 5 == 1 or 4.
146 * See for instance: https://en.wikipedia.org/wiki/Legendre_symbol
147 *
148 * Since all safe primes > 7 must satisfy p mod 12 == 11
149 * and all safe primes > 11 must satisfy p mod 5 != 1
150 * we can further improve the condition for g = 2, 3 and 5:
151 * for 2, p mod 24 == 23
152 * for 3, p mod 12 == 11
153 * for 5, p mod 60 == 59
154 */
dh_builtin_genparams(DH * ret,int prime_len,int generator,BN_GENCB * cb)155 static int dh_builtin_genparams(DH *ret, int prime_len, int generator,
156 BN_GENCB *cb)
157 {
158 BIGNUM *t1, *t2;
159 int g, ok = -1;
160 BN_CTX *ctx = NULL;
161
162 if (prime_len > OPENSSL_DH_MAX_MODULUS_BITS) {
163 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
164 return 0;
165 }
166
167 if (prime_len < DH_MIN_MODULUS_BITS) {
168 ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
169 return 0;
170 }
171
172 ctx = BN_CTX_new();
173 if (ctx == NULL)
174 goto err;
175 BN_CTX_start(ctx);
176 t1 = BN_CTX_get(ctx);
177 t2 = BN_CTX_get(ctx);
178 if (t2 == NULL)
179 goto err;
180
181 /* Make sure 'ret' has the necessary elements */
182 if (ret->params.p == NULL && ((ret->params.p = BN_new()) == NULL))
183 goto err;
184 if (ret->params.g == NULL && ((ret->params.g = BN_new()) == NULL))
185 goto err;
186
187 if (generator <= 1) {
188 ERR_raise(ERR_LIB_DH, DH_R_BAD_GENERATOR);
189 goto err;
190 }
191 if (generator == DH_GENERATOR_2) {
192 if (!BN_set_word(t1, 24))
193 goto err;
194 if (!BN_set_word(t2, 23))
195 goto err;
196 g = 2;
197 } else if (generator == DH_GENERATOR_5) {
198 if (!BN_set_word(t1, 60))
199 goto err;
200 if (!BN_set_word(t2, 59))
201 goto err;
202 g = 5;
203 } else {
204 /*
205 * in the general case, don't worry if 'generator' is a generator or
206 * not: since we are using safe primes, it will generate either an
207 * order-q or an order-2q group, which both is OK
208 */
209 if (!BN_set_word(t1, 12))
210 goto err;
211 if (!BN_set_word(t2, 11))
212 goto err;
213 g = generator;
214 }
215
216 if (!BN_generate_prime_ex(ret->params.p, prime_len, 1, t1, t2, cb))
217 goto err;
218 if (!BN_GENCB_call(cb, 3, 0))
219 goto err;
220 if (!BN_set_word(ret->params.g, g))
221 goto err;
222 ret->dirty_cnt++;
223 ok = 1;
224 err:
225 if (ok == -1) {
226 ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
227 ok = 0;
228 }
229
230 BN_CTX_end(ctx);
231 BN_CTX_free(ctx);
232 return ok;
233 }
234 #endif /* FIPS_MODULE */
235