/*

 * Copyright 2002-2024 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

 */

/*

 * ECDSA low level APIs are deprecated for public use, but still ok for

 * internal use.

 */

#include "internal/deprecated.h"

#include <string.h>

#include <openssl/err.h>

#include <openssl/obj_mac.h>

#include <openssl/rand.h>

#include "crypto/bn.h"

#include "ec_local.h"

#define MIN_ECDSA_SIGN_ORDERBITS 64

/*

 * It is highly unlikely that a retry will happen,

 * Multiple retries would indicate that something is wrong

 * with the group parameters (which would normally only happen

 * with a bad custom group).

 */

#define MAX_ECDSA_SIGN_RETRIES 8

int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,

                          BIGNUM **rp)

{

    if (eckey->group->meth->ecdsa_sign_setup == NULL) {

        ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);

        return 0;

    }

    return eckey->group->meth->ecdsa_sign_setup(eckey, ctx_in, kinvp, rp);

}

ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,

                               const BIGNUM *in_kinv, const BIGNUM *in_r,

                               EC_KEY *eckey)

{

    if (eckey->group->meth->ecdsa_sign_sig == NULL) {

        ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);

        return NULL;

    }

    return eckey->group->meth->ecdsa_sign_sig(dgst, dgst_len,

                                              in_kinv, in_r, eckey);

}

int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,

                          const ECDSA_SIG *sig, EC_KEY *eckey)

{

    if (eckey->group->meth->ecdsa_verify_sig == NULL) {

        ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);

        return 0;

    }

    return eckey->group->meth->ecdsa_verify_sig(dgst, dgst_len, sig, eckey);

}

int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,

                    unsigned char *sig, unsigned int *siglen,

                    const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)

{

    ECDSA_SIG *s;

    if (sig == NULL && (kinv == NULL || r == NULL)) {

        *siglen = ECDSA_size(eckey);

        return 1;

    }

    s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);

    if (s == NULL) {

        *siglen = 0;

        return 0;

    }

    *siglen = i2d_ECDSA_SIG(s, sig != NULL ? &sig : NULL);

    ECDSA_SIG_free(s);

    return 1;

}

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

                            BIGNUM **kinvp, BIGNUM **rp,

                            const unsigned char *dgst, int dlen)

{

    BN_CTX *ctx = NULL;

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

    const BIGNUM *order;

    EC_POINT *tmp_point = NULL;

    const EC_GROUP *group;

    int ret = 0;

    int order_bits;

    const BIGNUM *priv_key;

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

        ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);

        return 0;

    }

    if ((priv_key = EC_KEY_get0_private_key(eckey)) == NULL) {

        ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);

        return 0;

    }

    if (!EC_KEY_can_sign(eckey)) {

        ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);

        return 0;

    }

    if ((ctx = ctx_in) == NULL) {

        if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL) {

            ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

            return 0;

        }

    }

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

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

    X = BN_new();

    if (k == NULL || r == NULL || X == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

        goto err;

    }

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

        ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);

        goto err;

    }

    if ((order = EC_GROUP_get0_order(group)) == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);

        goto err;

    }

    /* Preallocate space */

    order_bits = BN_num_bits(order);

    /* Check the number of bits here so that an infinite loop is not possible */

    if (order_bits < MIN_ECDSA_SIGN_ORDERBITS

        || !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 (dgst != NULL) {

                if (!ossl_bn_gen_dsa_nonce_fixed_top(k, order, priv_key,

                                                     dgst, dlen, ctx)) {

                    ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);

                    goto err;

                }

            } else {

                if (!ossl_bn_priv_rand_range_fixed_top(k, order, 0, ctx)) {

                    ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);

                    goto err;

                }

            }

        } while (ossl_bn_is_word_fixed_top(k, 0));

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

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

            ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);

            goto err;

        }

        if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {

            ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);

            goto err;

        }

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

            ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

            goto err;

        }

    } while (BN_is_zero(r));

    /* compute the inverse of k */

    if (!ossl_ec_group_do_inverse_ord(group, k, k, ctx)) {

        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

        goto err;

    }

    /* clear old values if necessary */

    BN_clear_free(*rp);

    BN_clear_free(*kinvp);

    /* save the pre-computed values  */

    *rp = r;

    *kinvp = k;

    ret = 1;

 err:

    if (!ret) {

        BN_clear_free(k);

        BN_clear_free(r);

    }

    if (ctx != ctx_in)

        BN_CTX_free(ctx);

    EC_POINT_free(tmp_point);

    BN_clear_free(X);

    return ret;

}

int ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,

                                 BIGNUM **rp)

{

    return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);

}

ECDSA_SIG *ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len,

                                      const BIGNUM *in_kinv, const BIGNUM *in_r,

                                      EC_KEY *eckey)

{

    int ok = 0, i;

    int retries = 0;

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

    const BIGNUM *order, *ckinv;

    BN_CTX *ctx = NULL;

    const EC_GROUP *group;

    ECDSA_SIG *ret;

    const BIGNUM *priv_key;

    group = EC_KEY_get0_group(eckey);

    priv_key = EC_KEY_get0_private_key(eckey);

    if (group == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);

        return NULL;

    }

    if (priv_key == NULL) {

        ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);

        return NULL;

    }

    if (!EC_KEY_can_sign(eckey)) {

        ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);

        return NULL;

    }

    ret = ECDSA_SIG_new();

    if (ret == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

        return NULL;

    }

    ret->r = BN_new();

    ret->s = BN_new();

    if (ret->r == NULL || ret->s == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    s = ret->s;

    if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL

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

        ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    if ((order = EC_GROUP_get0_order(group)) == NULL) {

        ERR_raise(ERR_LIB_EC, 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)) {

        ERR_raise(ERR_LIB_EC, 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))) {

        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

        goto err;

    }

    do {

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

            if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {

                ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);

                goto err;

            }

            ckinv = kinv;

        } else {

            ckinv = in_kinv;

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

                ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

                goto err;

            }

        }

        /*

         * With only one multiplicant being in Montgomery domain

         * multiplication yields real result without post-conversion.

         * Also note that all operations but last are performed with

         * zero-padded vectors. Last operation, BN_mod_mul_montgomery

         * below, returns user-visible value with removed zero padding.

         */

        if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)

            || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {

            ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

            goto err;

        }

        if (!bn_mod_add_fixed_top(s, s, m, order)) {

            ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

            goto err;

        }

        /*

         * |s| can still be larger than modulus, because |m| can be. In

         * such case we count on Montgomery reduction to tie it up.

         */

        if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)

            || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {

            ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

            goto err;

        }

        if (BN_is_zero(s)) {

            /*

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

             * generate new kinv and r values

             */

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

                ERR_raise(ERR_LIB_EC, EC_R_NEED_NEW_SETUP_VALUES);

                goto err;

            }

            /* Avoid infinite loops cause by invalid group parameters */

            if (retries++ > MAX_ECDSA_SIGN_RETRIES) {

                ERR_raise(ERR_LIB_EC, EC_R_TOO_MANY_RETRIES);

                goto err;

            }

        } else {

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

            break;

        }

    } while (1);

    ok = 1;

 err:

    if (!ok) {

        ECDSA_SIG_free(ret);

        ret = NULL;

    }

    BN_CTX_free(ctx);

    BN_clear_free(m);

    BN_clear_free(kinv);

    return ret;

}

/*-

 * returns

 *      1: correct signature

 *      0: incorrect signature

 *     -1: error

 */

int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,

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

{

    ECDSA_SIG *s;

    const unsigned char *p = sigbuf;

    unsigned char *der = NULL;

    int derlen = -1;

    int ret = -1;

    s = ECDSA_SIG_new();

    if (s == NULL)

        return ret;

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

        goto err;

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

    derlen = i2d_ECDSA_SIG(s, &der);

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

        goto err;

    ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);

 err:

    OPENSSL_free(der);

    ECDSA_SIG_free(s);

    return ret;

}

int ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len,

                                 const ECDSA_SIG *sig, EC_KEY *eckey)

{

    int ret = -1, i;

    BN_CTX *ctx;

    const BIGNUM *order;

    BIGNUM *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) {

        ERR_raise(ERR_LIB_EC, EC_R_MISSING_PARAMETERS);

        return -1;

    }

    if (!EC_KEY_can_sign(eckey)) {

        ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);

        return -1;

    }

    ctx = BN_CTX_new_ex(eckey->libctx);

    if (ctx == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

        return -1;

    }

    BN_CTX_start(ctx);

    u1 = BN_CTX_get(ctx);

    u2 = BN_CTX_get(ctx);

    m = BN_CTX_get(ctx);

    X = BN_CTX_get(ctx);

    if (X == NULL) {

        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

        goto err;

    }

    order = EC_GROUP_get0_order(group);

    if (order == NULL) {

        ERR_raise(ERR_LIB_EC, 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) {

        ERR_raise(ERR_LIB_EC, EC_R_BAD_SIGNATURE);

        ret = 0;                /* signature is invalid */

        goto err;

    }

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

    if (!ossl_ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {

        ERR_raise(ERR_LIB_EC, 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)) {

        ERR_raise(ERR_LIB_EC, 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))) {

        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

        goto err;

    }

    /* u1 = m * tmp mod order */

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

        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

        goto err;

    }

    /* u2 = r * w mod q */

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

        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);

        goto err;

    }

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

        ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);

        goto err;

    }

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

        ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);

        goto err;

    }

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

        ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);

        goto err;

    }

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

        ERR_raise(ERR_LIB_EC, 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);

    EC_POINT_free(point);

    return ret;

}