426 lines
11 KiB
C
426 lines
11 KiB
C
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/* $OpenBSD: dsa_ossl.c,v 1.42 2019/06/04 18:12:26 tb Exp $ */
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
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#include <stdio.h>
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#include <openssl/asn1.h>
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#include <openssl/bn.h>
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#include <openssl/dsa.h>
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#include <openssl/err.h>
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#include <openssl/sha.h>
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#include "bn_lcl.h"
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static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
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static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
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BIGNUM **rp);
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static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
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DSA *dsa);
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static int dsa_init(DSA *dsa);
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static int dsa_finish(DSA *dsa);
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static DSA_METHOD openssl_dsa_meth = {
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.name = "OpenSSL DSA method",
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.dsa_do_sign = dsa_do_sign,
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.dsa_sign_setup = dsa_sign_setup,
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.dsa_do_verify = dsa_do_verify,
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.init = dsa_init,
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.finish = dsa_finish,
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};
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const DSA_METHOD *
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DSA_OpenSSL(void)
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{
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return &openssl_dsa_meth;
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}
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static DSA_SIG *
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dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
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{
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BIGNUM b, bm, bxr, binv, m, *kinv = NULL, *r = NULL, *s = NULL;
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BN_CTX *ctx = NULL;
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int reason = ERR_R_BN_LIB;
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DSA_SIG *ret = NULL;
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int noredo = 0;
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BN_init(&b);
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BN_init(&binv);
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BN_init(&bm);
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BN_init(&bxr);
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BN_init(&m);
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if (!dsa->p || !dsa->q || !dsa->g) {
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reason = DSA_R_MISSING_PARAMETERS;
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goto err;
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}
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s = BN_new();
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if (s == NULL)
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goto err;
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ctx = BN_CTX_new();
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if (ctx == NULL)
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goto err;
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/*
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* If the digest length is greater than N (the bit length of q), the
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* leftmost N bits of the digest shall be used, see FIPS 186-3, 4.2.
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* In this case the digest length is given in bytes.
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*/
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if (dlen > BN_num_bytes(dsa->q))
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dlen = BN_num_bytes(dsa->q);
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if (BN_bin2bn(dgst, dlen, &m) == NULL)
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goto err;
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redo:
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if (dsa->kinv == NULL || dsa->r == NULL) {
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if (!DSA_sign_setup(dsa, ctx, &kinv, &r))
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goto err;
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} else {
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kinv = dsa->kinv;
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dsa->kinv = NULL;
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r = dsa->r;
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dsa->r = NULL;
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noredo = 1;
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}
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/*
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* Compute:
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*
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* s = inv(k)(m + xr) mod q
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*
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* In order to reduce the possibility of a side-channel attack, the
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* following is calculated using a blinding value:
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*
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* s = inv(b)(bm + bxr)inv(k) mod q
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*
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* Where b is a random value in the range [1, q).
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*/
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if (!bn_rand_interval(&b, BN_value_one(), dsa->q))
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goto err;
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if (BN_mod_inverse_ct(&binv, &b, dsa->q, ctx) == NULL)
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goto err;
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if (!BN_mod_mul(&bxr, &b, dsa->priv_key, dsa->q, ctx)) /* bx */
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goto err;
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if (!BN_mod_mul(&bxr, &bxr, r, dsa->q, ctx)) /* bxr */
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goto err;
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if (!BN_mod_mul(&bm, &b, &m, dsa->q, ctx)) /* bm */
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goto err;
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if (!BN_mod_add(s, &bxr, &bm, dsa->q, ctx)) /* s = bm + bxr */
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goto err;
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if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) /* s = b(m + xr)k^-1 */
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goto err;
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if (!BN_mod_mul(s, s, &binv, dsa->q, ctx)) /* s = (m + xr)k^-1 */
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goto err;
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/*
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* Redo if r or s is zero as required by FIPS 186-3: this is very
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* unlikely.
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*/
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if (BN_is_zero(r) || BN_is_zero(s)) {
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if (noredo) {
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reason = DSA_R_NEED_NEW_SETUP_VALUES;
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goto err;
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}
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goto redo;
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}
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if ((ret = DSA_SIG_new()) == NULL) {
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reason = ERR_R_MALLOC_FAILURE;
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goto err;
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}
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ret->r = r;
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ret->s = s;
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err:
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if (!ret) {
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DSAerror(reason);
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BN_free(r);
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BN_free(s);
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}
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BN_CTX_free(ctx);
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BN_clear_free(&b);
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BN_clear_free(&bm);
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BN_clear_free(&bxr);
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BN_clear_free(&binv);
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BN_clear_free(&m);
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BN_clear_free(kinv);
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return ret;
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}
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static int
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dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
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{
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BN_CTX *ctx;
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BIGNUM k, l, m, *kinv = NULL, *r = NULL;
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int q_bits, ret = 0;
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if (!dsa->p || !dsa->q || !dsa->g) {
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DSAerror(DSA_R_MISSING_PARAMETERS);
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return 0;
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}
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BN_init(&k);
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BN_init(&l);
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BN_init(&m);
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if (ctx_in == NULL) {
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if ((ctx = BN_CTX_new()) == NULL)
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goto err;
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} else
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ctx = ctx_in;
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if ((r = BN_new()) == NULL)
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goto err;
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/* Preallocate space */
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q_bits = BN_num_bits(dsa->q);
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if (!BN_set_bit(&k, q_bits) ||
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!BN_set_bit(&l, q_bits) ||
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!BN_set_bit(&m, q_bits))
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goto err;
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if (!bn_rand_interval(&k, BN_value_one(), dsa->q))
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goto err;
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BN_set_flags(&k, BN_FLG_CONSTTIME);
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if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
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if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
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CRYPTO_LOCK_DSA, dsa->p, ctx))
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goto err;
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}
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/* Compute r = (g^k mod p) mod q */
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/*
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* We do not want timing information to leak the length of k,
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* so we compute G^k using an equivalent exponent of fixed
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* bit-length.
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*
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* We unconditionally perform both of these additions to prevent a
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* small timing information leakage. We then choose the sum that is
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* one bit longer than the modulus.
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*
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* TODO: revisit the BN_copy aiming for a memory access agnostic
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* conditional copy.
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*/
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if (!BN_add(&l, &k, dsa->q) ||
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!BN_add(&m, &l, dsa->q) ||
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!BN_copy(&k, BN_num_bits(&l) > q_bits ? &l : &m))
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goto err;
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if (dsa->meth->bn_mod_exp != NULL) {
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if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, &k, dsa->p, ctx,
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dsa->method_mont_p))
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goto err;
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} else {
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if (!BN_mod_exp_mont_ct(r, dsa->g, &k, dsa->p, ctx,
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dsa->method_mont_p))
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goto err;
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}
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if (!BN_mod_ct(r, r, dsa->q, ctx))
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goto err;
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/* Compute part of 's = inv(k) (m + xr) mod q' */
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if ((kinv = BN_mod_inverse_ct(NULL, &k, dsa->q, ctx)) == NULL)
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goto err;
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BN_clear_free(*kinvp);
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*kinvp = kinv;
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kinv = NULL;
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BN_clear_free(*rp);
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*rp = r;
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ret = 1;
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err:
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if (!ret) {
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DSAerror(ERR_R_BN_LIB);
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BN_clear_free(r);
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}
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if (ctx_in == NULL)
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BN_CTX_free(ctx);
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BN_clear_free(&k);
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BN_clear_free(&l);
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BN_clear_free(&m);
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return ret;
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}
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static int
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dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, DSA *dsa)
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{
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BN_CTX *ctx;
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BIGNUM u1, u2, t1;
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BN_MONT_CTX *mont = NULL;
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int ret = -1, i;
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if (!dsa->p || !dsa->q || !dsa->g) {
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DSAerror(DSA_R_MISSING_PARAMETERS);
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return -1;
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}
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i = BN_num_bits(dsa->q);
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/* FIPS 186-3 allows only three different sizes for q. */
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if (i != 160 && i != 224 && i != 256) {
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DSAerror(DSA_R_BAD_Q_VALUE);
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return -1;
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}
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if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
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DSAerror(DSA_R_MODULUS_TOO_LARGE);
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return -1;
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}
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BN_init(&u1);
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BN_init(&u2);
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BN_init(&t1);
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if ((ctx = BN_CTX_new()) == NULL)
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goto err;
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if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
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BN_ucmp(sig->r, dsa->q) >= 0) {
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ret = 0;
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goto err;
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}
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if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
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BN_ucmp(sig->s, dsa->q) >= 0) {
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ret = 0;
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goto err;
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}
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/* Calculate w = inv(s) mod q, saving w in u2. */
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if ((BN_mod_inverse_ct(&u2, sig->s, dsa->q, ctx)) == NULL)
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goto err;
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/*
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* If the digest length is greater than the size of q use the
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* BN_num_bits(dsa->q) leftmost bits of the digest, see FIPS 186-3, 4.2.
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||
|
|
*/
|
||
|
|
if (dgst_len > (i >> 3))
|
||
|
|
dgst_len = (i >> 3);
|
||
|
|
|
||
|
|
/* Save m in u1. */
|
||
|
|
if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
|
||
|
|
goto err;
|
||
|
|
|
||
|
|
/* u1 = m * w mod q */
|
||
|
|
if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
|
||
|
|
goto err;
|
||
|
|
|
||
|
|
/* u2 = r * w mod q */
|
||
|
|
if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
|
||
|
|
goto err;
|
||
|
|
|
||
|
|
if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
|
||
|
|
mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
|
||
|
|
CRYPTO_LOCK_DSA, dsa->p, ctx);
|
||
|
|
if (!mont)
|
||
|
|
goto err;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (dsa->meth->dsa_mod_exp != NULL) {
|
||
|
|
if (!dsa->meth->dsa_mod_exp(dsa, &t1, dsa->g, &u1, dsa->pub_key,
|
||
|
|
&u2, dsa->p, ctx, mont))
|
||
|
|
goto err;
|
||
|
|
} else {
|
||
|
|
if (!BN_mod_exp2_mont(&t1, dsa->g, &u1, dsa->pub_key, &u2,
|
||
|
|
dsa->p, ctx, mont))
|
||
|
|
goto err;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* BN_copy(&u1,&t1); */
|
||
|
|
/* let u1 = u1 mod q */
|
||
|
|
if (!BN_mod_ct(&u1, &t1, dsa->q, ctx))
|
||
|
|
goto err;
|
||
|
|
|
||
|
|
/* v is in u1 - if the signature is correct, it will be equal to r. */
|
||
|
|
ret = BN_ucmp(&u1, sig->r) == 0;
|
||
|
|
|
||
|
|
err:
|
||
|
|
if (ret < 0)
|
||
|
|
DSAerror(ERR_R_BN_LIB);
|
||
|
|
BN_CTX_free(ctx);
|
||
|
|
BN_free(&u1);
|
||
|
|
BN_free(&u2);
|
||
|
|
BN_free(&t1);
|
||
|
|
|
||
|
|
return ret;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int
|
||
|
|
dsa_init(DSA *dsa)
|
||
|
|
{
|
||
|
|
dsa->flags |= DSA_FLAG_CACHE_MONT_P;
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int
|
||
|
|
dsa_finish(DSA *dsa)
|
||
|
|
{
|
||
|
|
BN_MONT_CTX_free(dsa->method_mont_p);
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
|