501 lines
15 KiB
C
501 lines
15 KiB
C
/* crypto/dsa/dsa_ossl.c */
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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 "cryptlib.h"
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#include <openssl/bn.h>
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#include <openssl/sha.h>
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#include <openssl/dsa.h>
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#include <openssl/rand.h>
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#include <openssl/asn1.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,
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DSA_SIG *sig, 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 BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
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BN_CTX *ctx);
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static DSA_METHOD openssl_dsa_meth = {
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"OpenSSL DSA method",
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dsa_do_sign,
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dsa_sign_setup,
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dsa_do_verify,
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NULL, /* dsa_mod_exp, */
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NULL, /* dsa_bn_mod_exp, */
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dsa_init,
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dsa_finish,
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0,
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NULL,
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NULL,
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NULL
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};
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/*-
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* These macro wrappers replace attempts to use the dsa_mod_exp() and
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* bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
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* having a the macro work as an expression by bundling an "err_instr". So;
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*
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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)) goto err;
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*
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* can be replaced by;
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*
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* DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
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* dsa->method_mont_p);
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*/
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#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
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do { \
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int _tmp_res53; \
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if ((dsa)->meth->dsa_mod_exp) \
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_tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
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(a2), (p2), (m), (ctx), (in_mont)); \
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else \
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_tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
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(m), (ctx), (in_mont)); \
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if (!_tmp_res53) err_instr; \
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} while(0)
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#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
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do { \
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int _tmp_res53; \
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if ((dsa)->meth->bn_mod_exp) \
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_tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
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(m), (ctx), (m_ctx)); \
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else \
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_tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
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if (!_tmp_res53) err_instr; \
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} while(0)
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const DSA_METHOD *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 *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
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{
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BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
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BIGNUM *m, *blind, *blindm, *tmp;
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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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if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) {
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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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m = BN_CTX_get(ctx);
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blind = BN_CTX_get(ctx);
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blindm = BN_CTX_get(ctx);
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tmp = BN_CTX_get(ctx);
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if (tmp == 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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if (dlen > BN_num_bytes(dsa->q))
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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,
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* 4.2
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*/
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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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/*
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* The normal signature calculation is:
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*
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* s := k^-1 * (m + r * priv_key) mod q
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*
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* We will blind this to protect against side channel attacks
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*
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* s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q
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*/
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/* Generate a blinding value */
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do {
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if (!BN_rand(blind, BN_num_bits(dsa->q) - 1, -1, 0))
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goto err;
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} while (BN_is_zero(blind));
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BN_set_flags(blind, BN_FLG_CONSTTIME);
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BN_set_flags(blindm, BN_FLG_CONSTTIME);
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BN_set_flags(tmp, BN_FLG_CONSTTIME);
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/* tmp := blind * priv_key * r mod q */
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if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->q, ctx))
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goto err;
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if (!BN_mod_mul(tmp, tmp, r, dsa->q, ctx))
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goto err;
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/* blindm := blind * m mod q */
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if (!BN_mod_mul(blindm, blind, m, dsa->q, ctx))
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goto err;
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/* s : = (blind * priv_key * r) + (blind * m) mod q */
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if (!BN_mod_add_quick(s, tmp, blindm, dsa->q))
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goto err;
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/* s := s * k^-1 mod q */
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if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
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goto err;
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/* s:= s * blind^-1 mod q */
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if (BN_mod_inverse(blind, blind, dsa->q, ctx) == NULL)
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goto err;
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if (!BN_mod_mul(s, s, blind, dsa->q, ctx))
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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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ret = DSA_SIG_new();
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if (ret == NULL)
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goto err;
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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 == NULL) {
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DSAerr(DSA_F_DSA_DO_SIGN, 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(kinv);
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return ret;
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}
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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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{
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BN_CTX *ctx;
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BIGNUM k, kq, *K, *kinv = NULL, *r = NULL;
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BIGNUM l, m;
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int ret = 0;
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int q_bits;
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if (!dsa->p || !dsa->q || !dsa->g) {
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DSAerr(DSA_F_DSA_SIGN_SETUP, 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(&kq);
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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) + sizeof(dsa->q->d[0]) * 16;
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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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/* Get random k */
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do
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if (!BN_rand_range(&k, dsa->q))
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goto err;
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while (BN_is_zero(&k));
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if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
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BN_set_flags(&k, BN_FLG_CONSTTIME);
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BN_set_flags(&l, BN_FLG_CONSTTIME);
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}
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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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if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
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/*
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* We do not want timing information to leak the length of k, so we
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* compute G^k using an equivalent scalar of fixed 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(&kq, BN_num_bits(&l) > q_bits ? &l : &m))
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goto err;
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BN_set_flags(&kq, BN_FLG_CONSTTIME);
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K = &kq;
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} else {
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K = &k;
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}
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DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
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dsa->method_mont_p);
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if (!BN_mod(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 = dsa_mod_inverse_fermat(&k, dsa->q, ctx)) == NULL)
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goto err;
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if (*kinvp != NULL)
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BN_clear_free(*kinvp);
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*kinvp = kinv;
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kinv = NULL;
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if (*rp != 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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DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
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if (r != NULL)
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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(&kq);
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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 dsa_do_verify(const unsigned char *dgst, int dgst_len,
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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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DSAerr(DSA_F_DSA_DO_VERIFY, 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 different sizes for q */
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if (i != 160 && i != 224 && i != 256) {
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DSAerr(DSA_F_DSA_DO_VERIFY, 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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DSAerr(DSA_F_DSA_DO_VERIFY, 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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/*
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* Calculate W = inv(S) mod Q save W in u2
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*/
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if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
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goto err;
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/* save M in u1 */
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if (dgst_len > (i >> 3))
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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,
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* 4.2
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*/
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dgst_len = (i >> 3);
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if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
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goto err;
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/* u1 = M * w mod q */
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if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
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goto err;
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/* u2 = r * w mod q */
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if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
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goto err;
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if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
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mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
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CRYPTO_LOCK_DSA, dsa->p, ctx);
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if (!mont)
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goto err;
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}
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DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p,
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ctx, mont);
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/* BN_copy(&u1,&t1); */
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/* let u1 = u1 mod q */
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if (!BN_mod(&u1, &t1, dsa->q, ctx))
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goto err;
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/*
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* V is now in u1. If the signature is correct, it will be equal to R.
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*/
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ret = (BN_ucmp(&u1, sig->r) == 0);
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err:
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if (ret < 0)
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DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
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if (ctx != NULL)
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BN_CTX_free(ctx);
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BN_free(&u1);
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BN_free(&u2);
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BN_free(&t1);
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return (ret);
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}
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static int dsa_init(DSA *dsa)
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{
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dsa->flags |= DSA_FLAG_CACHE_MONT_P;
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return (1);
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}
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static int dsa_finish(DSA *dsa)
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{
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if (dsa->method_mont_p)
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BN_MONT_CTX_free(dsa->method_mont_p);
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return (1);
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}
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/*
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* Compute the inverse of k modulo q.
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* Since q is prime, Fermat's Little Theorem applies, which reduces this to
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* mod-exp operation. Both the exponent and modulus are public information
|
|
* so a mod-exp that doesn't leak the base is sufficient. A newly allocated
|
|
* BIGNUM is returned which the caller must free.
|
|
*/
|
|
static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
|
|
BN_CTX *ctx)
|
|
{
|
|
BIGNUM *res = NULL;
|
|
BIGNUM *r, e;
|
|
|
|
if ((r = BN_new()) == NULL)
|
|
return NULL;
|
|
|
|
BN_init(&e);
|
|
|
|
if (BN_set_word(r, 2)
|
|
&& BN_sub(&e, q, r)
|
|
&& BN_mod_exp_mont(r, k, &e, q, ctx, NULL))
|
|
res = r;
|
|
else
|
|
BN_free(r);
|
|
BN_free(&e);
|
|
return res;
|
|
}
|