/*

 * Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright 2017 Ribose Inc. All Rights Reserved.

 * Ported from Ribose contributions from Botan.

 *

 * 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 "internal/sm2.h"

#include "internal/sm2err.h"

#include <openssl/err.h>

#include <openssl/evp.h>

#include <openssl/bn.h>

#include <string.h>

#include "internal/numbers.h"

int sm2_compute_userid_digest(uint8_t *out,

                              const EVP_MD *digest,

                              const char *user_id,

                              const EC_KEY *key)

{

    int rc = 0;

    const EC_GROUP *group = EC_KEY_get0_group(key);

    BN_CTX *ctx = NULL;

    EVP_MD_CTX *hash = NULL;

    BIGNUM *p = NULL;

    BIGNUM *a = NULL;

    BIGNUM *b = NULL;

    BIGNUM *xG = NULL;

    BIGNUM *yG = NULL;

    BIGNUM *xA = NULL;

    BIGNUM *yA = NULL;

    int p_bytes = 0;

    uint8_t *buf = NULL;

    size_t uid_len = 0;

    uint16_t entla = 0;

    uint8_t e_byte = 0;

    hash = EVP_MD_CTX_new();

    ctx = BN_CTX_new();

    if (hash == NULL || ctx == NULL) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    p = BN_CTX_get(ctx);

    a = BN_CTX_get(ctx);

    b = BN_CTX_get(ctx);

    xG = BN_CTX_get(ctx);

    yG = BN_CTX_get(ctx);

    xA = BN_CTX_get(ctx);

    yA = BN_CTX_get(ctx);

    if (yA == NULL) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    if (!EVP_DigestInit(hash, digest)) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_EVP_LIB);

        goto done;

    }

    /* ZA = H256(ENTLA || IDA || a || b || xG || yG || xA || yA) */

    uid_len = strlen(user_id);

    if (uid_len >= (UINT16_MAX / 8)) {

        /* too large */

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, SM2_R_USER_ID_TOO_LARGE);

        goto done;

    }

    entla = (uint16_t)(8 * uid_len);

    e_byte = entla >> 8;

    if (!EVP_DigestUpdate(hash, &e_byte, 1)) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_EVP_LIB);

        goto done;

    }

    e_byte = entla & 0xFF;

    if (!EVP_DigestUpdate(hash, &e_byte, 1)

            || !EVP_DigestUpdate(hash, user_id, uid_len)) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_EVP_LIB);

        goto done;

    }

    if (!EC_GROUP_get_curve(group, p, a, b, ctx)) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_EC_LIB);

        goto done;

    }

    p_bytes = BN_num_bytes(p);

    buf = OPENSSL_zalloc(p_bytes);

    if (buf == NULL) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    if (BN_bn2binpad(a, buf, p_bytes) < 0

            || !EVP_DigestUpdate(hash, buf, p_bytes)

            || BN_bn2binpad(b, buf, p_bytes) < 0

            || !EVP_DigestUpdate(hash, buf, p_bytes)

            || !EC_POINT_get_affine_coordinates(group,

                                                EC_GROUP_get0_generator(group),

                                                xG, yG, ctx)

            || BN_bn2binpad(xG, buf, p_bytes) < 0

            || !EVP_DigestUpdate(hash, buf, p_bytes)

            || BN_bn2binpad(yG, buf, p_bytes) < 0

            || !EVP_DigestUpdate(hash, buf, p_bytes)

            || !EC_POINT_get_affine_coordinates(group,

                                                EC_KEY_get0_public_key(key),

                                                xA, yA, ctx)

            || BN_bn2binpad(xA, buf, p_bytes) < 0

            || !EVP_DigestUpdate(hash, buf, p_bytes)

            || BN_bn2binpad(yA, buf, p_bytes) < 0

            || !EVP_DigestUpdate(hash, buf, p_bytes)

            || !EVP_DigestFinal(hash, out, NULL)) {

        SM2err(SM2_F_SM2_COMPUTE_USERID_DIGEST, ERR_R_INTERNAL_ERROR);

        goto done;

    }

    rc = 1;

 done:

    OPENSSL_free(buf);

    BN_CTX_free(ctx);

    EVP_MD_CTX_free(hash);

    return rc;

}