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/*
* Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* DSA low level APIs are deprecated for public use, but still ok for
* internal use.
*/
#include "internal/deprecated.h"
#include <stdio.h>
#include "internal/cryptlib.h"
#include "crypto/bn.h"
#include <openssl/bn.h>
#include <openssl/sha.h>
#include "dsa_local.h"
#include <openssl/asn1.h>
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
BIGNUM **rp);
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
BIGNUM **rp, const unsigned char *dgst, int dlen);
static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
DSA_SIG *sig, DSA *dsa);
static int dsa_init(DSA *dsa);
static int dsa_finish(DSA *dsa);
static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
BN_CTX *ctx);
static DSA_METHOD openssl_dsa_meth = {
"OpenSSL DSA method",
dsa_do_sign,
dsa_sign_setup_no_digest,
dsa_do_verify,
NULL, /* dsa_mod_exp, */
NULL, /* dsa_bn_mod_exp, */
dsa_init,
dsa_finish,
DSA_FLAG_FIPS_METHOD,
NULL,
NULL,
NULL
};
static const DSA_METHOD *default_DSA_method = &openssl_dsa_meth;
#ifndef FIPS_MODULE
void DSA_set_default_method(const DSA_METHOD *meth)
{
default_DSA_method = meth;
}
#endif /* FIPS_MODULE */
const DSA_METHOD *DSA_get_default_method(void)
{
return default_DSA_method;
}
const DSA_METHOD *DSA_OpenSSL(void)
{
return &openssl_dsa_meth;
}
DSA_SIG *dsa_do_sign_int(const unsigned char *dgst, int dlen, DSA *dsa)
{
BIGNUM *kinv = NULL;
BIGNUM *m, *blind, *blindm, *tmp;
BN_CTX *ctx = NULL;
int reason = ERR_R_BN_LIB;
DSA_SIG *ret = NULL;
int rv = 0;
if (dsa->params.p == NULL
|| dsa->params.q == NULL
|| dsa->params.g == NULL) {
reason = DSA_R_MISSING_PARAMETERS;
goto err;
}
if (dsa->priv_key == NULL) {
reason = DSA_R_MISSING_PRIVATE_KEY;
goto err;
}
ret = DSA_SIG_new();
if (ret == NULL)
goto err;
ret->r = BN_new();
ret->s = BN_new();
if (ret->r == NULL || ret->s == NULL)
goto err;
ctx = BN_CTX_new_ex(dsa->libctx);
if (ctx == NULL)
goto err;
m = BN_CTX_get(ctx);
blind = BN_CTX_get(ctx);
blindm = BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
if (tmp == NULL)
goto err;
redo:
if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen))
goto err;
if (dlen > BN_num_bytes(dsa->params.q))
/*
* if the digest length is greater than the size of q use the
* BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
* 4.2
*/
dlen = BN_num_bytes(dsa->params.q);
if (BN_bin2bn(dgst, dlen, m) == NULL)
goto err;
/*
* The normal signature calculation is:
*
* s := k^-1 * (m + r * priv_key) mod q
*
* We will blind this to protect against side channel attacks
*
* s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q
*/
/* Generate a blinding value */
do {
if (!BN_priv_rand_ex(blind, BN_num_bits(dsa->params.q) - 1,
BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, ctx))
goto err;
} while (BN_is_zero(blind));
BN_set_flags(blind, BN_FLG_CONSTTIME);
BN_set_flags(blindm, BN_FLG_CONSTTIME);
BN_set_flags(tmp, BN_FLG_CONSTTIME);
/* tmp := blind * priv_key * r mod q */
if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->params.q, ctx))
goto err;
if (!BN_mod_mul(tmp, tmp, ret->r, dsa->params.q, ctx))
goto err;
/* blindm := blind * m mod q */
if (!BN_mod_mul(blindm, blind, m, dsa->params.q, ctx))
goto err;
/* s : = (blind * priv_key * r) + (blind * m) mod q */
if (!BN_mod_add_quick(ret->s, tmp, blindm, dsa->params.q))
goto err;
/* s := s * k^-1 mod q */
if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->params.q, ctx))
goto err;
/* s:= s * blind^-1 mod q */
if (BN_mod_inverse(blind, blind, dsa->params.q, ctx) == NULL)
goto err;
if (!BN_mod_mul(ret->s, ret->s, blind, dsa->params.q, ctx))
goto err;
/*
* Redo if r or s is zero as required by FIPS 186-3: this is very
* unlikely.
*/
if (BN_is_zero(ret->r) || BN_is_zero(ret->s))
goto redo;
rv = 1;
err:
if (rv == 0) {
ERR_raise(ERR_LIB_DSA, reason);
DSA_SIG_free(ret);
ret = NULL;
}
BN_CTX_free(ctx);
BN_clear_free(kinv);
return ret;
}
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
{
return dsa_do_sign_int(dgst, dlen, dsa);
}
static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
BIGNUM **kinvp, BIGNUM **rp)
{
return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
}
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
BIGNUM **kinvp, BIGNUM **rp,
const unsigned char *dgst, int dlen)
{
BN_CTX *ctx = NULL;
BIGNUM *k, *kinv = NULL, *r = *rp;
BIGNUM *l;
int ret = 0;
int q_bits, q_words;
if (!dsa->params.p || !dsa->params.q || !dsa->params.g) {
ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PARAMETERS);
return 0;
}
/* Reject obviously invalid parameters */
if (BN_is_zero(dsa->params.p)
|| BN_is_zero(dsa->params.q)
|| BN_is_zero(
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