/* * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy * in the file LICENSE in the source distribution or at * https://www.openssl.org/source/license.html */ /* * NB: These functions have been upgraded - the previous prototypes are in * dh_depr.c as wrappers to these ones. - Geoff */ /* * DH low level APIs are deprecated for public use, but still ok for * internal use. * * NOTE: When generating keys for key-agreement schemes - FIPS 140-2 IG 9.9 * states that no additional pairwise tests are required (apart from the tests * specified in SP800-56A) when generating keys. Hence DH pairwise tests are * omitted here. */ #include "internal/deprecated.h" #include #include "internal/cryptlib.h" #include #include #include "crypto/dh.h" #include "crypto/security_bits.h" #include "dh_local.h" #ifndef FIPS_MODULE static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb); #endif /* FIPS_MODULE */ int ossl_dh_generate_ffc_parameters(DH *dh, int type, int pbits, int qbits, BN_GENCB *cb) { int ret, res; #ifndef FIPS_MODULE if (type == DH_PARAMGEN_TYPE_FIPS_186_2) ret = ossl_ffc_params_FIPS186_2_generate(dh->libctx, &dh->params, FFC_PARAM_TYPE_DH, pbits, qbits, &res, cb); else #endif ret = ossl_ffc_params_FIPS186_4_generate(dh->libctx, &dh->params, FFC_PARAM_TYPE_DH, pbits, qbits, &res, cb); if (ret > 0) dh->dirty_cnt++; return ret; } int ossl_dh_get_named_group_uid_from_size(int pbits) { /* * Just choose an approved safe prime group. * The alternative to this is to generate FIPS186-4 domain parameters i.e. * return dh_generate_ffc_parameters(ret, prime_len, 0, NULL, cb); * As the FIPS186-4 generated params are for backwards compatibility, * the safe prime group should be used as the default. */ int nid; switch (pbits) { case 2048: nid = NID_ffdhe2048; break; case 3072: nid = NID_ffdhe3072; break; case 4096: nid = NID_ffdhe4096; break; case 6144: nid = NID_ffdhe6144; break; case 8192: nid = NID_ffdhe8192; break; /* unsupported prime_len */ default: return NID_undef; } return nid; } #ifdef FIPS_MODULE static int dh_gen_named_group(OSSL_LIB_CTX *libctx, DH *ret, int prime_len) { DH *dh; int ok = 0; int nid = ossl_dh_get_named_group_uid_from_size(prime_len); if (nid == NID_undef) return 0; dh = ossl_dh_new_by_nid_ex(libctx, nid); if (dh != NULL && ossl_ffc_params_copy(&ret->params, &dh->params)) { ok = 1; ret->dirty_cnt++; } DH_free(dh); return ok; } #endif /* FIPS_MODULE */ int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, BN_GENCB *cb) { #ifdef FIPS_MODULE if (generator != 2) return 0; return dh_gen_named_group(ret->libctx, ret, prime_len); #else if (ret->meth->generate_params) return ret->meth->generate_params(ret, prime_len, generator, cb); return dh_builtin_genparams(ret, prime_len, generator, cb); #endif /* FIPS_MODULE */ } #ifndef FIPS_MODULE /*- * We generate DH parameters as follows * find a prime p which is prime_len bits long, * where q=(p-1)/2 is also prime. * In the following we assume that g is not 0, 1 or p-1, since it * would generate only trivial subgroups. * For this case, g is a generator of the order-q subgroup if * g^q mod p == 1. * Or in terms of the Legendre symbol: (g/p) == 1. * * Having said all that, * there is another special case method for the generators 2, 3 and 5. * Using the quadratic reciprocity law it is possible to solve * (g/p) == 1 for the special values 2, 3, 5: * (2/p) == 1 if p mod 8 == 1 or 7. * (3/p) == 1 if p mod 12 == 1 or 11. * (5/p) == 1 if p mod 5 == 1 or 4. * See for instance: https://en.wikipedia.org/wiki/Legendre_symbol * * Since all safe primes > 7 must satisfy p mod 12 == 11 * and all safe primes > 11 must satisfy p mod 5 != 1 * we can further improve the condition for g = 2, 3 and 5: * for 2, p mod 24 == 23 * for 3, p mod 12 == 11 * for 5, p mod 60 == 59 */ static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb) { BIGNUM *t1, *t2; int g, ok = -1; BN_CTX *ctx = NULL; if (prime_len > OPENSSL_DH_MAX_MODULUS_BITS) { ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE); return 0; } if (prime_len < DH_MIN_MODULUS_BITS) { ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL); return 0; } ctx = BN_CTX_new(); if (ctx == NULL) goto err; BN_CTX_start(ctx); t1 = BN_CTX_get(ctx); t2 = BN_CTX_get(ctx); if (t2 == NULL) goto err; /* Make sure 'ret' has the necessary elements */ if (ret->params.p == NULL && ((ret->params.p = BN_new()) == NULL)) goto err; if (ret->params.g == NULL && ((ret->params.g = BN_new()) == NULL)) goto err; if (generator <= 1) { ERR_raise(ERR_LIB_DH, DH_R_BAD_GENERATOR); goto err; } if (generator == DH_GENERATOR_2) { if (!BN_set_word(t1, 24)) goto err; if (!BN_set_word(t2, 23)) goto err; g = 2; } else if (generator == DH_GENERATOR_5) { if (!BN_set_word(t1, 60)) goto err; if (!BN_set_word(t2, 59)) goto err; g = 5; } else { /* * in the general case, don't worry if 'generator' is a generator or * not: since we are using safe primes, it will generate either an * order-q or an order-2q group, which both is OK */ if (!BN_set_word(t1, 12)) goto err; if (!BN_set_word(t2, 11)) goto err; g = generator; } if (!BN_generate_prime_ex(ret->params.p, prime_len, 1, t1, t2, cb)) goto err; if (!BN_GENCB_call(cb, 3, 0)) goto err; if (!BN_set_word(ret->params.g, g)) goto err; /* We are using safe prime p, set key length equivalent to RFC 7919 */ ret->length = (2 * ossl_ifc_ffc_compute_security_bits(prime_len) + 24) / 25 * 25; ret->dirty_cnt++; ok = 1; err: if (ok == -1) { ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB); ok = 0; } BN_CTX_end(ctx); BN_CTX_free(ctx); return ok; } #endif /* FIPS_MODULE */