/* $OpenBSD: dh_key.c,v 1.43 2025/05/10 05:54:38 tb Exp $ */ /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */ #include <stdio.h> #include <openssl/bn.h> #include <openssl/dh.h> #include "bn_local.h" #include "dh_local.h" #include "err_local.h" static int generate_key(DH *dh) { int ok = 0; unsigned l; BN_CTX *ctx; BN_MONT_CTX *mont = NULL; BIGNUM *pub_key = NULL, *priv_key = NULL; if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { DHerror(DH_R_MODULUS_TOO_LARGE); return 0; } ctx = BN_CTX_new(); if (ctx == NULL) goto err; if ((priv_key = dh->priv_key) == NULL) { if ((priv_key = BN_new()) == NULL) goto err; } if ((pub_key = dh->pub_key) == NULL) { if ((pub_key = BN_new()) == NULL) goto err; } if (dh->flags & DH_FLAG_CACHE_MONT_P) { mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, CRYPTO_LOCK_DH, dh->p, ctx); if (!mont) goto err; } if (dh->priv_key == NULL) { if (dh->q) { if (!bn_rand_interval(priv_key, 2, dh->q)) goto err; } else { /* secret exponent length */ l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; if (!BN_rand(priv_key, l, 0, 0)) goto err; } } if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key, dh->p, ctx, mont)) goto err; dh->pub_key = pub_key; dh->priv_key = priv_key; ok = 1; err: if (ok != 1) DHerror(ERR_R_BN_LIB); if (dh->pub_key == NULL) BN_free(pub_key); if (dh->priv_key == NULL) BN_free(priv_key); BN_CTX_free(ctx); return ok; } static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) { BN_CTX *ctx = NULL; BN_MONT_CTX *mont = NULL; BIGNUM *tmp; int ret = -1; int check_result; if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { DHerror(DH_R_MODULUS_TOO_LARGE); goto err; } ctx = BN_CTX_new(); if (ctx == NULL) goto err; BN_CTX_start(ctx); if ((tmp = BN_CTX_get(ctx)) == NULL) goto err; if (dh->priv_key == NULL) { DHerror(DH_R_NO_PRIVATE_VALUE); goto err; } if (dh->flags & DH_FLAG_CACHE_MONT_P) { mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, CRYPTO_LOCK_DH, dh->p, ctx); BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); if (!mont) goto err; } if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { DHerror(DH_R_INVALID_PUBKEY); goto err; } if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) { DHerror(ERR_R_BN_LIB); goto err; } ret = BN_bn2bin(tmp, key); err: if (ctx != NULL) { BN_CTX_end(ctx); BN_CTX_free(ctx); } return ret; } static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) { return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx); } static int dh_init(DH *dh) { dh->flags |= DH_FLAG_CACHE_MONT_P; return 1; } static int dh_finish(DH *dh) { BN_MONT_CTX_free(dh->method_mont_p); return 1; } int DH_generate_key(DH *dh) { return dh->meth->generate_key(dh); } LCRYPTO_ALIAS(DH_generate_key); int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) { return dh->meth->compute_key(key, pub_key, dh); } LCRYPTO_ALIAS(DH_compute_key); static const DH_METHOD dh_ossl = { .name = "OpenSSL DH Method", .generate_key = generate_key, .compute_key = compute_key, .bn_mod_exp = dh_bn_mod_exp, .init = dh_init, .finish = dh_finish, }; const DH_METHOD * DH_OpenSSL(void) { return &dh_ossl; } LCRYPTO_ALIAS(DH_OpenSSL);
