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 34static int dh_builtin_genparams(DH *ret, int prime_len, int generator, 35 BN_GENCB *cb); 36#endif /* FIPS_MODULE */ 37 38int 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 58int 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 94static 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 114int 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 */ 155static 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_ex(ret->libctx); 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_ex2(ret->params.p, prime_len, 1, t1, t2, cb, ctx)) 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