/*

 * 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 "internal/ec_int.h" /* ec_group_do_inverse_ord() */

#include <openssl/err.h>

#include <openssl/evp.h>

#include <openssl/err.h>

#include <openssl/bn.h>

#include <string.h>

static BIGNUM *sm2_compute_msg_hash(const EVP_MD *digest,

                                    const EC_KEY *key,

                                    const char *user_id,

                                    const uint8_t *msg, size_t msg_len)

{

    EVP_MD_CTX *hash = EVP_MD_CTX_new();

    const int md_size = EVP_MD_size(digest);

    uint8_t *za = NULL;

    BIGNUM *e = NULL;

    if (md_size < 0) {

        SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, SM2_R_INVALID_DIGEST);

        goto done;

    }

    za = OPENSSL_zalloc(md_size);

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

        SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    if (!sm2_compute_userid_digest(za, digest, user_id, key)) {

        /* SM2err already called */

        goto done;

    }

    if (!EVP_DigestInit(hash, digest)

            || !EVP_DigestUpdate(hash, za, md_size)

            || !EVP_DigestUpdate(hash, msg, msg_len)

               /* reuse za buffer to hold H(ZA || M) */

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

        SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_EVP_LIB);

        goto done;

    }

    e = BN_bin2bn(za, md_size, NULL);

    if (e == NULL)

        SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_INTERNAL_ERROR);

 done:

    OPENSSL_free(za);

    EVP_MD_CTX_free(hash);

    return e;

}

static ECDSA_SIG *sm2_sig_gen(const EC_KEY *key, const BIGNUM *e)

{

    const BIGNUM *dA = EC_KEY_get0_private_key(key);

    const EC_GROUP *group = EC_KEY_get0_group(key);

    const BIGNUM *order = EC_GROUP_get0_order(group);

    ECDSA_SIG *sig = NULL;

    EC_POINT *kG = NULL;

    BN_CTX *ctx = NULL;

    BIGNUM *k = NULL;

    BIGNUM *rk = NULL;

    BIGNUM *r = NULL;

    BIGNUM *s = NULL;

    BIGNUM *x1 = NULL;

    BIGNUM *tmp = NULL;

    kG = EC_POINT_new(group);

    ctx = BN_CTX_new();

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

        SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    BN_CTX_start(ctx);

    k = BN_CTX_get(ctx);

    rk = BN_CTX_get(ctx);

    x1 = BN_CTX_get(ctx);

    tmp = BN_CTX_get(ctx);

    if (tmp == NULL) {

        SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    /*

     * These values are returned and so should not be allocated out of the

     * context

     */

    r = BN_new();

    s = BN_new();

    if (r == NULL || s == NULL) {

        SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    for (;;) {

        if (!BN_priv_rand_range(k, order)) {

            SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);

            goto done;

        }

        if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)

                || !EC_POINT_get_affine_coordinates(group, kG, x1, NULL,

                                                        ctx)

                || !BN_mod_add(r, e, x1, order, ctx)) {

            SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);

            goto done;

        }

        /* try again if r == 0 or r+k == n */

        if (BN_is_zero(r))

            continue;

        if (!BN_add(rk, r, k)) {

            SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);

            goto done;

        }

        if (BN_cmp(rk, order) == 0)

            continue;

        if (!BN_add(s, dA, BN_value_one())

                || !ec_group_do_inverse_ord(group, s, s, ctx)

                || !BN_mod_mul(tmp, dA, r, order, ctx)

                || !BN_sub(tmp, k, tmp)

                || !BN_mod_mul(s, s, tmp, order, ctx)) {

            SM2err(SM2_F_SM2_SIG_GEN, ERR_R_BN_LIB);

            goto done;

        }

        sig = ECDSA_SIG_new();

        if (sig == NULL) {

            SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);

            goto done;

        }

         /* takes ownership of r and s */

        ECDSA_SIG_set0(sig, r, s);

        break;

    }

 done:

    if (sig == NULL) {

        BN_free(r);

        BN_free(s);

    }

    BN_CTX_free(ctx);

    EC_POINT_free(kG);

    return sig;

}

static int sm2_sig_verify(const EC_KEY *key, const ECDSA_SIG *sig,

                          const BIGNUM *e)

{

    int ret = 0;

    const EC_GROUP *group = EC_KEY_get0_group(key);

    const BIGNUM *order = EC_GROUP_get0_order(group);

    BN_CTX *ctx = NULL;

    EC_POINT *pt = NULL;

    BIGNUM *t = NULL;

    BIGNUM *x1 = NULL;

    const BIGNUM *r = NULL;

    const BIGNUM *s = NULL;

    ctx = BN_CTX_new();

    pt = EC_POINT_new(group);

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

        SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    BN_CTX_start(ctx);

    t = BN_CTX_get(ctx);

    x1 = BN_CTX_get(ctx);

    if (x1 == NULL) {

        SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    /*

     * B1: verify whether r' in [1,n-1], verification failed if not

     * B2: vefify whether s' in [1,n-1], verification failed if not

     * B3: set M'~=ZA || M'

     * B4: calculate e'=Hv(M'~)

     * B5: calculate t = (r' + s') modn, verification failed if t=0

     * B6: calculate the point (x1', y1')=[s']G + [t]PA

     * B7: calculate R=(e'+x1') modn, verfication pass if yes, otherwise failed

     */

    ECDSA_SIG_get0(sig, &r, &s);

    if (BN_cmp(r, BN_value_one()) < 0

            || BN_cmp(s, BN_value_one()) < 0

            || BN_cmp(order, r) <= 0

            || BN_cmp(order, s) <= 0) {

        SM2err(SM2_F_SM2_SIG_VERIFY, SM2_R_BAD_SIGNATURE);

        goto done;

    }

    if (!BN_mod_add(t, r, s, order, ctx)) {

        SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_BN_LIB);

        goto done;

    }

    if (BN_is_zero(t)) {

        SM2err(SM2_F_SM2_SIG_VERIFY, SM2_R_BAD_SIGNATURE);

        goto done;

    }

    if (!EC_POINT_mul(group, pt, s, EC_KEY_get0_public_key(key), t, ctx)

            || !EC_POINT_get_affine_coordinates(group, pt, x1, NULL, ctx)) {

        SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_EC_LIB);

        goto done;

    }

    if (!BN_mod_add(t, e, x1, order, ctx)) {

        SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_BN_LIB);

        goto done;

    }

    if (BN_cmp(r, t) == 0)

        ret = 1;

 done:

    EC_POINT_free(pt);

    BN_CTX_free(ctx);

    return ret;

}

ECDSA_SIG *sm2_do_sign(const EC_KEY *key,

                       const EVP_MD *digest,

                       const char *user_id, const uint8_t *msg, size_t msg_len)

{

    BIGNUM *e = NULL;

    ECDSA_SIG *sig = NULL;

    e = sm2_compute_msg_hash(digest, key, user_id, msg, msg_len);

    if (e == NULL) {

        /* SM2err already called */

        goto done;

    }

    sig = sm2_sig_gen(key, e);

 done:

    BN_free(e);

    return sig;

}

int sm2_do_verify(const EC_KEY *key,

                  const EVP_MD *digest,

                  const ECDSA_SIG *sig,

                  const char *user_id, const uint8_t *msg, size_t msg_len)

{

    BIGNUM *e = NULL;

    int ret = 0;

    e = sm2_compute_msg_hash(digest, key, user_id, msg, msg_len);

    if (e == NULL) {

        /* SM2err already called */

        goto done;

    }

    ret = sm2_sig_verify(key, sig, e);

 done:

    BN_free(e);

    return ret;

}

int sm2_sign(const unsigned char *dgst, int dgstlen,

             unsigned char *sig, unsigned int *siglen, EC_KEY *eckey)

{

    BIGNUM *e = NULL;

    ECDSA_SIG *s = NULL;

    int sigleni;

    int ret = -1;

    e = BN_bin2bn(dgst, dgstlen, NULL);

    if (e == NULL) {

       SM2err(SM2_F_SM2_SIGN, ERR_R_BN_LIB);

       goto done;

    }

    s = sm2_sig_gen(eckey, e);

    sigleni = i2d_ECDSA_SIG(s, &sig);

    if (sigleni < 0) {

       SM2err(SM2_F_SM2_SIGN, ERR_R_INTERNAL_ERROR);

       goto done;

    }

    *siglen = (unsigned int)sigleni;

    ret = 1;

 done:

    ECDSA_SIG_free(s);

    BN_free(e);

    return ret;

}

int sm2_verify(const unsigned char *dgst, int dgstlen,

               const unsigned char *sig, int sig_len, EC_KEY *eckey)

{

    ECDSA_SIG *s = NULL;

    BIGNUM *e = NULL;

    const unsigned char *p = sig;

    unsigned char *der = NULL;

    int derlen = -1;

    int ret = -1;

    s = ECDSA_SIG_new();

    if (s == NULL) {

        SM2err(SM2_F_SM2_VERIFY, ERR_R_MALLOC_FAILURE);

        goto done;

    }

    if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL) {

        SM2err(SM2_F_SM2_VERIFY, SM2_R_INVALID_ENCODING);

        goto done;

    }

    /* Ensure signature uses DER and doesn't have trailing garbage */

    derlen = i2d_ECDSA_SIG(s, &der);

    if (derlen != sig_len || memcmp(sig, der, derlen) != 0) {

        SM2err(SM2_F_SM2_VERIFY, SM2_R_INVALID_ENCODING);

        goto done;

    }

    e = BN_bin2bn(dgst, dgstlen, NULL);

    if (e == NULL) {

        SM2err(SM2_F_SM2_VERIFY, ERR_R_BN_LIB);

        goto done;

    }

    ret = sm2_sig_verify(eckey, s, e);

 done:

    OPENSSL_free(der);

    BN_free(e);

    ECDSA_SIG_free(s);

    return ret;

}