459 lines
12 KiB
C
459 lines
12 KiB
C
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/*
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* Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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/*
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* DH low level APIs are deprecated for public use, but still ok for
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* internal use.
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*/
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#include "internal/deprecated.h"
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#include <stdio.h>
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#include "internal/cryptlib.h"
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#include "dh_local.h"
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#include "crypto/bn.h"
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#include "crypto/dh.h"
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#include "crypto/security_bits.h"
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#ifdef FIPS_MODULE
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# define MIN_STRENGTH 112
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#else
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# define MIN_STRENGTH 80
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#endif
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static int generate_key(DH *dh);
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static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
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const BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
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static int dh_init(DH *dh);
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static int dh_finish(DH *dh);
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/*
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* See SP800-56Ar3 Section 5.7.1.1
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* Finite Field Cryptography Diffie-Hellman (FFC DH) Primitive
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*/
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int ossl_dh_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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{
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BN_CTX *ctx = NULL;
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BN_MONT_CTX *mont = NULL;
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BIGNUM *z = NULL, *pminus1;
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int ret = -1;
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if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
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ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
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goto err;
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}
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if (dh->params.q != NULL
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&& BN_num_bits(dh->params.q) > OPENSSL_DH_MAX_MODULUS_BITS) {
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ERR_raise(ERR_LIB_DH, DH_R_Q_TOO_LARGE);
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goto err;
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}
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if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
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ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
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return 0;
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}
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ctx = BN_CTX_new_ex(dh->libctx);
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if (ctx == NULL)
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goto err;
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BN_CTX_start(ctx);
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pminus1 = BN_CTX_get(ctx);
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z = BN_CTX_get(ctx);
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if (z == NULL)
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goto err;
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if (dh->priv_key == NULL) {
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ERR_raise(ERR_LIB_DH, DH_R_NO_PRIVATE_VALUE);
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goto err;
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}
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if (dh->flags & DH_FLAG_CACHE_MONT_P) {
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mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
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dh->lock, dh->params.p, ctx);
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BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
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if (!mont)
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goto err;
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}
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/* (Step 1) Z = pub_key^priv_key mod p */
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if (!dh->meth->bn_mod_exp(dh, z, pub_key, dh->priv_key, dh->params.p, ctx,
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mont)) {
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ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
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goto err;
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}
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/* (Step 2) Error if z <= 1 or z = p - 1 */
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if (BN_copy(pminus1, dh->params.p) == NULL
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|| !BN_sub_word(pminus1, 1)
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|| BN_cmp(z, BN_value_one()) <= 0
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|| BN_cmp(z, pminus1) == 0) {
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ERR_raise(ERR_LIB_DH, DH_R_INVALID_SECRET);
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goto err;
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}
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/* return the padded key, i.e. same number of bytes as the modulus */
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ret = BN_bn2binpad(z, key, BN_num_bytes(dh->params.p));
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err:
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BN_clear(z); /* (Step 2) destroy intermediate values */
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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return ret;
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}
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/*-
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* NB: This function is inherently not constant time due to the
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* RFC 5246 (8.1.2) padding style that strips leading zero bytes.
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*/
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int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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{
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int ret = 0, i;
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volatile size_t npad = 0, mask = 1;
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/* compute the key; ret is constant unless compute_key is external */
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#ifdef FIPS_MODULE
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ret = ossl_dh_compute_key(key, pub_key, dh);
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#else
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ret = dh->meth->compute_key(key, pub_key, dh);
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#endif
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if (ret <= 0)
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return ret;
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/* count leading zero bytes, yet still touch all bytes */
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for (i = 0; i < ret; i++) {
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mask &= !key[i];
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npad += mask;
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}
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/* unpad key */
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ret -= npad;
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/* key-dependent memory access, potentially leaking npad / ret */
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memmove(key, key + npad, ret);
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/* key-dependent memory access, potentially leaking npad / ret */
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memset(key + ret, 0, npad);
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return ret;
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}
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int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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{
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int rv, pad;
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/* rv is constant unless compute_key is external */
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#ifdef FIPS_MODULE
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rv = ossl_dh_compute_key(key, pub_key, dh);
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#else
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rv = dh->meth->compute_key(key, pub_key, dh);
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#endif
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if (rv <= 0)
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return rv;
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pad = BN_num_bytes(dh->params.p) - rv;
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/* pad is constant (zero) unless compute_key is external */
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if (pad > 0) {
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memmove(key + pad, key, rv);
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memset(key, 0, pad);
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}
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return rv + pad;
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}
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static DH_METHOD dh_ossl = {
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"OpenSSL DH Method",
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generate_key,
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ossl_dh_compute_key,
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dh_bn_mod_exp,
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dh_init,
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dh_finish,
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DH_FLAG_FIPS_METHOD,
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NULL,
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NULL
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};
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static const DH_METHOD *default_DH_method = &dh_ossl;
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const DH_METHOD *DH_OpenSSL(void)
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{
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return &dh_ossl;
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}
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const DH_METHOD *DH_get_default_method(void)
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{
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return default_DH_method;
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}
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static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
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const BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
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{
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#ifdef S390X_MOD_EXP
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return s390x_mod_exp(r, a, p, m, ctx, m_ctx);
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#else
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return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
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#endif
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}
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static int dh_init(DH *dh)
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{
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dh->flags |= DH_FLAG_CACHE_MONT_P;
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dh->dirty_cnt++;
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return 1;
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}
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static int dh_finish(DH *dh)
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{
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BN_MONT_CTX_free(dh->method_mont_p);
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return 1;
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}
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#ifndef FIPS_MODULE
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void DH_set_default_method(const DH_METHOD *meth)
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{
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default_DH_method = meth;
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}
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#endif /* FIPS_MODULE */
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int DH_generate_key(DH *dh)
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{
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#ifdef FIPS_MODULE
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return generate_key(dh);
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#else
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return dh->meth->generate_key(dh);
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#endif
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}
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int ossl_dh_generate_public_key(BN_CTX *ctx, const DH *dh,
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const BIGNUM *priv_key, BIGNUM *pub_key)
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{
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int ret = 0;
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BIGNUM *prk = BN_new();
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BN_MONT_CTX *mont = NULL;
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if (prk == NULL)
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return 0;
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if (dh->flags & DH_FLAG_CACHE_MONT_P) {
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/*
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* We take the input DH as const, but we lie, because in some cases we
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* want to get a hold of its Montgomery context.
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*
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* We cast to remove the const qualifier in this case, it should be
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* fine...
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*/
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BN_MONT_CTX **pmont = (BN_MONT_CTX **)&dh->method_mont_p;
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mont = BN_MONT_CTX_set_locked(pmont, dh->lock, dh->params.p, ctx);
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if (mont == NULL)
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goto err;
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}
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BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
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/* pub_key = g^priv_key mod p */
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if (!dh->meth->bn_mod_exp(dh, pub_key, dh->params.g, prk, dh->params.p,
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ctx, mont))
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goto err;
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ret = 1;
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err:
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BN_clear_free(prk);
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return ret;
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}
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static int generate_key(DH *dh)
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{
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int ok = 0;
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int generate_new_key = 0;
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#ifndef FIPS_MODULE
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unsigned l;
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#endif
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BN_CTX *ctx = NULL;
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BIGNUM *pub_key = NULL, *priv_key = NULL;
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if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
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ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
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return 0;
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}
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if (dh->params.q != NULL
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&& BN_num_bits(dh->params.q) > OPENSSL_DH_MAX_MODULUS_BITS) {
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ERR_raise(ERR_LIB_DH, DH_R_Q_TOO_LARGE);
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return 0;
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}
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if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
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ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
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return 0;
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}
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ctx = BN_CTX_new_ex(dh->libctx);
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if (ctx == NULL)
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goto err;
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if (dh->priv_key == NULL) {
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priv_key = BN_secure_new();
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if (priv_key == NULL)
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goto err;
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generate_new_key = 1;
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} else {
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priv_key = dh->priv_key;
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}
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if (dh->pub_key == NULL) {
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pub_key = BN_new();
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if (pub_key == NULL)
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goto err;
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} else {
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pub_key = dh->pub_key;
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}
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if (generate_new_key) {
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/* Is it an approved safe prime ?*/
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if (DH_get_nid(dh) != NID_undef) {
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int max_strength =
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ossl_ifc_ffc_compute_security_bits(BN_num_bits(dh->params.p));
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if (dh->params.q == NULL
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|| dh->length > BN_num_bits(dh->params.q))
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goto err;
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/* dh->length = maximum bit length of generated private key */
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if (!ossl_ffc_generate_private_key(ctx, &dh->params, dh->length,
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max_strength, priv_key))
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goto err;
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} else {
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#ifdef FIPS_MODULE
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if (dh->params.q == NULL)
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goto err;
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#else
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if (dh->params.q == NULL) {
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/* secret exponent length, must satisfy 2^(l-1) <= p */
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if (dh->length != 0
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&& dh->length >= BN_num_bits(dh->params.p))
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goto err;
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l = dh->length ? dh->length : BN_num_bits(dh->params.p) - 1;
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if (!BN_priv_rand_ex(priv_key, l, BN_RAND_TOP_ONE,
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BN_RAND_BOTTOM_ANY, 0, ctx))
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goto err;
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/*
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* We handle just one known case where g is a quadratic non-residue:
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* for g = 2: p % 8 == 3
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*/
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if (BN_is_word(dh->params.g, DH_GENERATOR_2)
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&& !BN_is_bit_set(dh->params.p, 2)) {
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/* clear bit 0, since it won't be a secret anyway */
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if (!BN_clear_bit(priv_key, 0))
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goto err;
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}
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} else
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#endif
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{
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/* Do a partial check for invalid p, q, g */
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if (!ossl_ffc_params_simple_validate(dh->libctx, &dh->params,
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FFC_PARAM_TYPE_DH, NULL))
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goto err;
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/*
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* For FFC FIPS 186-4 keygen
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* security strength s = 112,
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* Max Private key size N = len(q)
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*/
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if (!ossl_ffc_generate_private_key(ctx, &dh->params,
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BN_num_bits(dh->params.q),
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MIN_STRENGTH,
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priv_key))
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goto err;
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}
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}
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}
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if (!ossl_dh_generate_public_key(ctx, dh, priv_key, pub_key))
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goto err;
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dh->pub_key = pub_key;
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|
|
dh->priv_key = priv_key;
|
||
|
|
dh->dirty_cnt++;
|
||
|
|
ok = 1;
|
||
|
|
err:
|
||
|
|
if (ok != 1)
|
||
|
|
ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
|
||
|
|
|
||
|
|
if (pub_key != dh->pub_key)
|
||
|
|
BN_free(pub_key);
|
||
|
|
if (priv_key != dh->priv_key)
|
||
|
|
BN_free(priv_key);
|
||
|
|
BN_CTX_free(ctx);
|
||
|
|
return ok;
|
||
|
|
}
|
||
|
|
|
||
|
|
int ossl_dh_buf2key(DH *dh, const unsigned char *buf, size_t len)
|
||
|
|
{
|
||
|
|
int err_reason = DH_R_BN_ERROR;
|
||
|
|
BIGNUM *pubkey = NULL;
|
||
|
|
const BIGNUM *p;
|
||
|
|
int ret;
|
||
|
|
|
||
|
|
if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL)
|
||
|
|
goto err;
|
||
|
|
DH_get0_pqg(dh, &p, NULL, NULL);
|
||
|
|
if (p == NULL || BN_num_bytes(p) == 0) {
|
||
|
|
err_reason = DH_R_NO_PARAMETERS_SET;
|
||
|
|
goto err;
|
||
|
|
}
|
||
|
|
/* Prevent small subgroup attacks per RFC 8446 Section 4.2.8.1 */
|
||
|
|
if (!ossl_dh_check_pub_key_partial(dh, pubkey, &ret)) {
|
||
|
|
err_reason = DH_R_INVALID_PUBKEY;
|
||
|
|
goto err;
|
||
|
|
}
|
||
|
|
if (DH_set0_key(dh, pubkey, NULL) != 1)
|
||
|
|
goto err;
|
||
|
|
return 1;
|
||
|
|
err:
|
||
|
|
ERR_raise(ERR_LIB_DH, err_reason);
|
||
|
|
BN_free(pubkey);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
size_t ossl_dh_key2buf(const DH *dh, unsigned char **pbuf_out, size_t size,
|
||
|
|
int alloc)
|
||
|
|
{
|
||
|
|
const BIGNUM *pubkey;
|
||
|
|
unsigned char *pbuf = NULL;
|
||
|
|
const BIGNUM *p;
|
||
|
|
int p_size;
|
||
|
|
|
||
|
|
DH_get0_pqg(dh, &p, NULL, NULL);
|
||
|
|
DH_get0_key(dh, &pubkey, NULL);
|
||
|
|
if (p == NULL || pubkey == NULL
|
||
|
|
|| (p_size = BN_num_bytes(p)) == 0
|
||
|
|
|| BN_num_bytes(pubkey) == 0) {
|
||
|
|
ERR_raise(ERR_LIB_DH, DH_R_INVALID_PUBKEY);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
if (pbuf_out != NULL && (alloc || *pbuf_out != NULL)) {
|
||
|
|
if (!alloc) {
|
||
|
|
if (size >= (size_t)p_size)
|
||
|
|
pbuf = *pbuf_out;
|
||
|
|
if (pbuf == NULL)
|
||
|
|
ERR_raise(ERR_LIB_DH, DH_R_INVALID_SIZE);
|
||
|
|
} else {
|
||
|
|
pbuf = OPENSSL_malloc(p_size);
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Errors raised above */
|
||
|
|
if (pbuf == NULL)
|
||
|
|
return 0;
|
||
|
|
/*
|
||
|
|
* As per Section 4.2.8.1 of RFC 8446 left pad public
|
||
|
|
* key with zeros to the size of p
|
||
|
|
*/
|
||
|
|
if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) {
|
||
|
|
if (alloc)
|
||
|
|
OPENSSL_free(pbuf);
|
||
|
|
ERR_raise(ERR_LIB_DH, DH_R_BN_ERROR);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
*pbuf_out = pbuf;
|
||
|
|
}
|
||
|
|
return p_size;
|
||
|
|
}
|