/*

 * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved

 *

 * Licensed under the OpenSSL license (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

 */

#include <openssl/err.h>

#include "ec_local.h"

const EC_METHOD *EC_GFp_mont_method(void)

{

    static const EC_METHOD ret = {

        EC_FLAGS_DEFAULT_OCT,

        NID_X9_62_prime_field,

        ec_GFp_mont_group_init,

        ec_GFp_mont_group_finish,

        ec_GFp_mont_group_clear_finish,

        ec_GFp_mont_group_copy,

        ec_GFp_mont_group_set_curve,

        ec_GFp_simple_group_get_curve,

        ec_GFp_simple_group_get_degree,

        ec_group_simple_order_bits,

        ec_GFp_simple_group_check_discriminant,

        ec_GFp_simple_point_init,

        ec_GFp_simple_point_finish,

        ec_GFp_simple_point_clear_finish,

        ec_GFp_simple_point_copy,

        ec_GFp_simple_point_set_to_infinity,

        ec_GFp_simple_set_Jprojective_coordinates_GFp,

        ec_GFp_simple_get_Jprojective_coordinates_GFp,

        ec_GFp_simple_point_set_affine_coordinates,

        ec_GFp_simple_point_get_affine_coordinates,

        0, 0, 0,

        ec_GFp_simple_add,

        ec_GFp_simple_dbl,

        ec_GFp_simple_invert,

        ec_GFp_simple_is_at_infinity,

        ec_GFp_simple_is_on_curve,

        ec_GFp_simple_cmp,

        ec_GFp_simple_make_affine,

        ec_GFp_simple_points_make_affine,

        0 /* mul */ ,

        0 /* precompute_mult */ ,

        0 /* have_precompute_mult */ ,

        ec_GFp_mont_field_mul,

        ec_GFp_mont_field_sqr,

        0 /* field_div */ ,

        ec_GFp_mont_field_inv,

        ec_GFp_mont_field_encode,

        ec_GFp_mont_field_decode,

        ec_GFp_mont_field_set_to_one,

        ec_key_simple_priv2oct,

        ec_key_simple_oct2priv,

        0, /* set private */

        ec_key_simple_generate_key,

        ec_key_simple_check_key,

        ec_key_simple_generate_public_key,

        0, /* keycopy */

        0, /* keyfinish */

        ecdh_simple_compute_key,

        0, /* field_inverse_mod_ord */

        ec_GFp_simple_blind_coordinates,

        ec_GFp_simple_ladder_pre,

        ec_GFp_simple_ladder_step,

        ec_GFp_simple_ladder_post

    };

    return &ret;

}

int ec_GFp_mont_group_init(EC_GROUP *group)

{

    int ok;

    ok = ec_GFp_simple_group_init(group);

    group->field_data1 = NULL;

    group->field_data2 = NULL;

    return ok;

}

void ec_GFp_mont_group_finish(EC_GROUP *group)

{

    BN_MONT_CTX_free(group->field_data1);

    group->field_data1 = NULL;

    BN_free(group->field_data2);

    group->field_data2 = NULL;

    ec_GFp_simple_group_finish(group);

}

void ec_GFp_mont_group_clear_finish(EC_GROUP *group)

{

    BN_MONT_CTX_free(group->field_data1);

    group->field_data1 = NULL;

    BN_clear_free(group->field_data2);

    group->field_data2 = NULL;

    ec_GFp_simple_group_clear_finish(group);

}

int ec_GFp_mont_group_copy(EC_GROUP *dest, const EC_GROUP *src)

{

    BN_MONT_CTX_free(dest->field_data1);

    dest->field_data1 = NULL;

    BN_clear_free(dest->field_data2);

    dest->field_data2 = NULL;

    if (!ec_GFp_simple_group_copy(dest, src))

        return 0;

    if (src->field_data1 != NULL) {

        dest->field_data1 = BN_MONT_CTX_new();

        if (dest->field_data1 == NULL)

            return 0;

        if (!BN_MONT_CTX_copy(dest->field_data1, src->field_data1))

            goto err;

    }

    if (src->field_data2 != NULL) {

        dest->field_data2 = BN_dup(src->field_data2);

        if (dest->field_data2 == NULL)

            goto err;

    }

    return 1;

 err:

    BN_MONT_CTX_free(dest->field_data1);

    dest->field_data1 = NULL;

    return 0;

}

int ec_GFp_mont_group_set_curve(EC_GROUP *group, const BIGNUM *p,

                                const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)

{

    BN_CTX *new_ctx = NULL;

    BN_MONT_CTX *mont = NULL;

    BIGNUM *one = NULL;

    int ret = 0;

    BN_MONT_CTX_free(group->field_data1);

    group->field_data1 = NULL;

    BN_free(group->field_data2);

    group->field_data2 = NULL;

    if (ctx == NULL) {

        ctx = new_ctx = BN_CTX_new();

        if (ctx == NULL)

            return 0;

    }

    mont = BN_MONT_CTX_new();

    if (mont == NULL)

        goto err;

    if (!BN_MONT_CTX_set(mont, p, ctx)) {

        ECerr(EC_F_EC_GFP_MONT_GROUP_SET_CURVE, ERR_R_BN_LIB);

        goto err;

    }

    one = BN_new();

    if (one == NULL)

        goto err;

    if (!BN_to_montgomery(one, BN_value_one(), mont, ctx))

        goto err;

    group->field_data1 = mont;

    mont = NULL;

    group->field_data2 = one;

    one = NULL;

    ret = ec_GFp_simple_group_set_curve(group, p, a, b, ctx);

    if (!ret) {

        BN_MONT_CTX_free(group->field_data1);

        group->field_data1 = NULL;

        BN_free(group->field_data2);

        group->field_data2 = NULL;

    }

 err:

    BN_free(one);

    BN_CTX_free(new_ctx);

    BN_MONT_CTX_free(mont);

    return ret;

}

int ec_GFp_mont_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,

                          const BIGNUM *b, BN_CTX *ctx)

{

    if (group->field_data1 == NULL) {

        ECerr(EC_F_EC_GFP_MONT_FIELD_MUL, EC_R_NOT_INITIALIZED);

        return 0;

    }

    return BN_mod_mul_montgomery(r, a, b, group->field_data1, ctx);

}

int ec_GFp_mont_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,

                          BN_CTX *ctx)

{

    if (group->field_data1 == NULL) {

        ECerr(EC_F_EC_GFP_MONT_FIELD_SQR, EC_R_NOT_INITIALIZED);

        return 0;

    }

    return BN_mod_mul_montgomery(r, a, a, group->field_data1, ctx);

}

/*-

 * Computes the multiplicative inverse of a in GF(p), storing the result in r.

 * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error.

 * We have a Mont structure, so SCA hardening is FLT inversion.

 */

int ec_GFp_mont_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,

                            BN_CTX *ctx)

{

    BIGNUM *e = NULL;

    BN_CTX *new_ctx = NULL;

    int ret = 0;

    if (group->field_data1 == NULL)

        return 0;

    if (ctx == NULL && (ctx = new_ctx = BN_CTX_secure_new()) == NULL)

        return 0;

    BN_CTX_start(ctx);

    if ((e = BN_CTX_get(ctx)) == NULL)

        goto err;

    /* Inverse in constant time with Fermats Little Theorem */

    if (!BN_set_word(e, 2))

        goto err;

    if (!BN_sub(e, group->field, e))

        goto err;

    /*-

     * Exponent e is public.

     * No need for scatter-gather or BN_FLG_CONSTTIME.

     */

    if (!BN_mod_exp_mont(r, a, e, group->field, ctx, group->field_data1))

        goto err;

    /* throw an error on zero */

    if (BN_is_zero(r)) {

        ECerr(EC_F_EC_GFP_MONT_FIELD_INV, EC_R_CANNOT_INVERT);

        goto err;

    }

    ret = 1;

  err:

    BN_CTX_end(ctx);

    BN_CTX_free(new_ctx);

    return ret;

}

int ec_GFp_mont_field_encode(const EC_GROUP *group, BIGNUM *r,

                             const BIGNUM *a, BN_CTX *ctx)

{

    if (group->field_data1 == NULL) {

        ECerr(EC_F_EC_GFP_MONT_FIELD_ENCODE, EC_R_NOT_INITIALIZED);

        return 0;

    }

    return BN_to_montgomery(r, a, (BN_MONT_CTX *)group->field_data1, ctx);

}

int ec_GFp_mont_field_decode(const EC_GROUP *group, BIGNUM *r,

                             const BIGNUM *a, BN_CTX *ctx)

{

    if (group->field_data1 == NULL) {

        ECerr(EC_F_EC_GFP_MONT_FIELD_DECODE, EC_R_NOT_INITIALIZED);

        return 0;

    }

    return BN_from_montgomery(r, a, group->field_data1, ctx);

}

int ec_GFp_mont_field_set_to_one(const EC_GROUP *group, BIGNUM *r,

                                 BN_CTX *ctx)

{

    if (group->field_data2 == NULL) {

        ECerr(EC_F_EC_GFP_MONT_FIELD_SET_TO_ONE, EC_R_NOT_INITIALIZED);

        return 0;

    }

    if (!BN_copy(r, group->field_data2))

        return 0;

    return 1;

}