/* crypto/ecdsa/ecs_ossl.c */

/*

 * Written by Nils Larsch for the OpenSSL project

 */

/* ====================================================================

 * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in

 *    the documentation and/or other materials provided with the

 *    distribution.

 *

 * 3. All advertising materials mentioning features or use of this

 *    software must display the following acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@OpenSSL.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR

 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 * ====================================================================

 *

 * This product includes cryptographic software written by Eric Young

 * (eay@cryptsoft.com).  This product includes software written by Tim

 * Hudson (tjh@cryptsoft.com).

 *

 */

#include "ecs_locl.h"

#include <openssl/err.h>

#include <openssl/obj_mac.h>

#include <openssl/bn.h>

static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen,

                                const BIGNUM *, const BIGNUM *,

                                EC_KEY *eckey);

static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,

                            BIGNUM **rp);

static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,

                           const ECDSA_SIG *sig, EC_KEY *eckey);

static ECDSA_METHOD openssl_ecdsa_meth = {

    "OpenSSL ECDSA method",

    ecdsa_do_sign,

    ecdsa_sign_setup,

    ecdsa_do_verify,

#if 0

    NULL,                       /* init */

    NULL,                       /* finish */

#endif

    0,                          /* flags */

    NULL                        /* app_data */

};

const ECDSA_METHOD *ECDSA_OpenSSL(void)

{

    return &openssl_ecdsa_meth;

}

static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,

                            BIGNUM **rp)

{

    BN_CTX *ctx = NULL;

    BIGNUM *k = NULL, *r = NULL, *order = NULL, *X = NULL;

    EC_POINT *tmp_point = NULL;

    const EC_GROUP *group;

    int ret = 0;

    int order_bits;

    if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {

        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);

        return 0;

    }

    if (ctx_in == NULL) {

        if ((ctx = BN_CTX_new()) == NULL) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);

            return 0;

        }

    } else

        ctx = ctx_in;

    k = BN_new();               /* this value is later returned in *kinvp */

    r = BN_new();               /* this value is later returned in *rp */

    order = BN_new();

    X = BN_new();

    if (!k || !r || !order || !X) {

        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    if ((tmp_point = EC_POINT_new(group)) == NULL) {

        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);

        goto err;

    }

    if (!EC_GROUP_get_order(group, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);

        goto err;

    }

    /* Preallocate space */

    order_bits = BN_num_bits(order);

    if (!BN_set_bit(k, order_bits)

        || !BN_set_bit(r, order_bits)

        || !BN_set_bit(X, order_bits))

        goto err;

    do {

        /* get random k */

        do

            if (!BN_rand_range(k, order)) {

                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,

                         ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);

                goto err;

            }

        while (BN_is_zero(k)) ;

        /*

         * We do not want timing information to leak the length of k, so we

         * compute G*k using an equivalent scalar of fixed bit-length.

         *

         * We unconditionally perform both of these additions to prevent a

         * small timing information leakage.  We then choose the sum that is

         * one bit longer than the order.  This guarantees the code

         * path used in the constant time implementations elsewhere.

         *

         * TODO: revisit the BN_copy aiming for a memory access agnostic

         * conditional copy.

         */

        if (!BN_add(r, k, order)

            || !BN_add(X, r, order)

            || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))

            goto err;

        /* compute r the x-coordinate of generator * k */

        if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);

            goto err;

        }

        if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==

            NID_X9_62_prime_field) {

            if (!EC_POINT_get_affine_coordinates_GFp

                (group, tmp_point, X, NULL, ctx)) {

                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);

                goto err;

            }

        }

#ifndef OPENSSL_NO_EC2M

        else {                  /* NID_X9_62_characteristic_two_field */

            if (!EC_POINT_get_affine_coordinates_GF2m(group,

                                                      tmp_point, X, NULL,

                                                      ctx)) {

                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);

                goto err;

            }

        }

#endif

        if (!BN_nnmod(r, X, order, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);

            goto err;

        }

    }

    while (BN_is_zero(r));

    /* compute the inverse of k */

    if (EC_GROUP_get_mont_data(group) != NULL) {

        /*

         * We want inverse in constant time, therefore we utilize the fact

         * order must be prime and use Fermats Little Theorem instead.

         */

        if (!BN_set_word(X, 2)) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);

            goto err;

        }

        if (!BN_mod_sub(X, order, X, order, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);

            goto err;

        }

        BN_set_flags(X, BN_FLG_CONSTTIME);

        if (!BN_mod_exp_mont_consttime

            (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);

            goto err;

        }

    } else {

        if (!BN_mod_inverse(k, k, order, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);

            goto err;

        }

    }

    /* clear old values if necessary */

    if (*rp != NULL)

        BN_clear_free(*rp);

    if (*kinvp != NULL)

        BN_clear_free(*kinvp);

    /* save the pre-computed values  */

    *rp = r;

    *kinvp = k;

    ret = 1;

 err:

    if (!ret) {

        if (k != NULL)

            BN_clear_free(k);

        if (r != NULL)

            BN_clear_free(r);

    }

    if (ctx_in == NULL)

        BN_CTX_free(ctx);

    if (order != NULL)

        BN_free(order);

    if (tmp_point != NULL)

        EC_POINT_free(tmp_point);

    if (X)

        BN_clear_free(X);

    return (ret);

}

static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,

                                const BIGNUM *in_kinv, const BIGNUM *in_r,

                                EC_KEY *eckey)

{

    int ok = 0, i;

    BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;

    const BIGNUM *ckinv;

    BN_CTX *ctx = NULL;

    const EC_GROUP *group;

    ECDSA_SIG *ret;

    ECDSA_DATA *ecdsa;

    const BIGNUM *priv_key;

    ecdsa = ecdsa_check(eckey);

    group = EC_KEY_get0_group(eckey);

    priv_key = EC_KEY_get0_private_key(eckey);

    if (group == NULL || priv_key == NULL || ecdsa == NULL) {

        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);

        return NULL;

    }

    ret = ECDSA_SIG_new();

    if (!ret) {

        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);

        return NULL;

    }

    s = ret->s;

    if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||

        (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {

        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    if (!EC_GROUP_get_order(group, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);

        goto err;

    }

    i = BN_num_bits(order);

    /*

     * Need to truncate digest if it is too long: first truncate whole bytes.

     */

    if (8 * dgst_len > i)

        dgst_len = (i + 7) / 8;

    if (!BN_bin2bn(dgst, dgst_len, m)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);

        goto err;

    }

    /* If still too long truncate remaining bits with a shift */

    if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {

        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);

        goto err;

    }

    do {

        if (in_kinv == NULL || in_r == NULL) {

            if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {

                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB);

                goto err;

            }

            ckinv = kinv;

        } else {

            ckinv = in_kinv;

            if (BN_copy(ret->r, in_r) == NULL) {

                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);

                goto err;

            }

        }

        if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);

            goto err;

        }

        if (!BN_mod_add_quick(s, tmp, m, order)) {

            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);

            goto err;

        }

        if (!BN_mod_mul(s, s, ckinv, order, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);

            goto err;

        }

        if (BN_is_zero(s)) {

            /*

             * if kinv and r have been supplied by the caller don't to

             * generate new kinv and r values

             */

            if (in_kinv != NULL && in_r != NULL) {

                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,

                         ECDSA_R_NEED_NEW_SETUP_VALUES);

                goto err;

            }

        } else

            /* s != 0 => we have a valid signature */

            break;

    }

    while (1);

    ok = 1;

 err:

    if (!ok) {

        ECDSA_SIG_free(ret);

        ret = NULL;

    }

    if (ctx)

        BN_CTX_free(ctx);

    if (m)

        BN_clear_free(m);

    if (tmp)

        BN_clear_free(tmp);

    if (order)

        BN_free(order);

    if (kinv)

        BN_clear_free(kinv);

    return ret;

}

static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,

                           const ECDSA_SIG *sig, EC_KEY *eckey)

{

    int ret = -1, i;

    BN_CTX *ctx;

    BIGNUM *order, *u1, *u2, *m, *X;

    EC_POINT *point = NULL;

    const EC_GROUP *group;

    const EC_POINT *pub_key;

    /* check input values */

    if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||

        (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);

        return -1;

    }

    ctx = BN_CTX_new();

    if (!ctx) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);

        return -1;

    }

    BN_CTX_start(ctx);

    order = BN_CTX_get(ctx);

    u1 = BN_CTX_get(ctx);

    u2 = BN_CTX_get(ctx);

    m = BN_CTX_get(ctx);

    X = BN_CTX_get(ctx);

    if (!X) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    if (!EC_GROUP_get_order(group, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);

        goto err;

    }

    if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||

        BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||

        BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);

        ret = 0;                /* signature is invalid */

        goto err;

    }

    /* calculate tmp1 = inv(S) mod order */

    if (!BN_mod_inverse(u2, sig->s, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    /* digest -> m */

    i = BN_num_bits(order);

    /*

     * Need to truncate digest if it is too long: first truncate whole bytes.

     */

    if (8 * dgst_len > i)

        dgst_len = (i + 7) / 8;

    if (!BN_bin2bn(dgst, dgst_len, m)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    /* If still too long truncate remaining bits with a shift */

    if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    /* u1 = m * tmp mod order */

    if (!BN_mod_mul(u1, m, u2, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    /* u2 = r * w mod q */

    if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    if ((point = EC_POINT_new(group)) == NULL) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);

        goto err;

    }

    if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==

        NID_X9_62_prime_field) {

        if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);

            goto err;

        }

    }

#ifndef OPENSSL_NO_EC2M

    else {                      /* NID_X9_62_characteristic_two_field */

        if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {

            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);

            goto err;

        }

    }

#endif

    if (!BN_nnmod(u1, X, order, ctx)) {

        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);

        goto err;

    }

    /*  if the signature is correct u1 is equal to sig->r */

    ret = (BN_ucmp(u1, sig->r) == 0);

 err:

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

    if (point)

        EC_POINT_free(point);

    return ret;

}