/* $OpenBSD: ecp_oct.c,v 1.14 2021/04/20 17:32:57 tb Exp $ */
/* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
 * for the OpenSSL project.
 * Includes code written by Bodo Moeller for the OpenSSL project.
*/
/* ====================================================================
 * Copyright (c) 1998-2002 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).
 *
 */
/* ====================================================================
 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
 * Portions of this software developed by SUN MICROSYSTEMS, INC.,
 * and contributed to the OpenSSL project.
 */

#include <openssl/err.h>

#include "ec_lcl.h"

int 
ec_GFp_simple_set_compressed_coordinates(const EC_GROUP * group,
    EC_POINT * point, const BIGNUM * x_, int y_bit, BN_CTX * ctx)
{
        BN_CTX *new_ctx = NULL;
        BIGNUM *tmp1, *tmp2, *x, *y;
        int ret = 0;

        /* clear error queue */
        ERR_clear_error();

        if (ctx == NULL) {
                ctx = new_ctx = BN_CTX_new();
                if (ctx == NULL)
                        return 0;
        }
        y_bit = (y_bit != 0);

        BN_CTX_start(ctx);
        if ((tmp1 = BN_CTX_get(ctx)) == NULL)
                goto err;
        if ((tmp2 = BN_CTX_get(ctx)) == NULL)
                goto err;
        if ((x = BN_CTX_get(ctx)) == NULL)
                goto err;
        if ((y = BN_CTX_get(ctx)) == NULL)
                goto err;

        /*
         * Recover y.  We have a Weierstrass equation y^2 = x^3 + a*x + b, so
         * y  is one of the square roots of  x^3 + a*x + b.
         */

        /* tmp1 := x^3 */
        if (!BN_nnmod(x, x_, &group->field, ctx))
                goto err;
        if (group->meth->field_decode == 0) {
                /* field_{sqr,mul} work on standard representation */
                if (!group->meth->field_sqr(group, tmp2, x_, ctx))
                        goto err;
                if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx))
                        goto err;
        } else {
                if (!BN_mod_sqr(tmp2, x_, &group->field, ctx))
                        goto err;
                if (!BN_mod_mul(tmp1, tmp2, x_, &group->field, ctx))
                        goto err;
        }

        /* tmp1 := tmp1 + a*x */
        if (group->a_is_minus3) {
                if (!BN_mod_lshift1_quick(tmp2, x, &group->field))
                        goto err;
                if (!BN_mod_add_quick(tmp2, tmp2, x, &group->field))
                        goto err;
                if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field))
                        goto err;
        } else {
                if (group->meth->field_decode) {
                        if (!group->meth->field_decode(group, tmp2, &group->a, ctx))
                                goto err;
                        if (!BN_mod_mul(tmp2, tmp2, x, &group->field, ctx))
                                goto err;
                } else {
                        /* field_mul works on standard representation */
                        if (!group->meth->field_mul(group, tmp2, &group->a, x, ctx))
                                goto err;
                }

                if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field))
                        goto err;
        }

        /* tmp1 := tmp1 + b */
        if (group->meth->field_decode) {
                if (!group->meth->field_decode(group, tmp2, &group->b, ctx))
                        goto err;
                if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field))
                        goto err;
        } else {
                if (!BN_mod_add_quick(tmp1, tmp1, &group->b, &group->field))
                        goto err;
        }

        if (!BN_mod_sqrt(y, tmp1, &group->field, ctx)) {
                unsigned long err = ERR_peek_last_error();

                if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
                        ERR_clear_error();
                        ECerror(EC_R_INVALID_COMPRESSED_POINT);
                } else
                        ECerror(ERR_R_BN_LIB);
                goto err;
        }
        if (y_bit != BN_is_odd(y)) {
                if (BN_is_zero(y)) {
                        int kron;

                        kron = BN_kronecker(x, &group->field, ctx);
                        if (kron == -2)
                                goto err;

                        if (kron == 1)
                                ECerror(EC_R_INVALID_COMPRESSION_BIT);
                        else
                                /*
                                 * BN_mod_sqrt() should have cought this
                                 * error (not a square)
                                 */
                                ECerror(EC_R_INVALID_COMPRESSED_POINT);
                        goto err;
                }
                if (!BN_usub(y, &group->field, y))
                        goto err;
        }
        if (y_bit != BN_is_odd(y)) {
                ECerror(ERR_R_INTERNAL_ERROR);
                goto err;
        }
        if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
                goto err;

        ret = 1;

 err:
        BN_CTX_end(ctx);
        BN_CTX_free(new_ctx);
        return ret;
}


size_t 
ec_GFp_simple_point2oct(const EC_GROUP * group, const EC_POINT * point, point_conversion_form_t form,
    unsigned char *buf, size_t len, BN_CTX * ctx)
{
        size_t ret;
        BN_CTX *new_ctx = NULL;
        int used_ctx = 0;
        BIGNUM *x, *y;
        size_t field_len, i, skip;

        if ((form != POINT_CONVERSION_COMPRESSED)
            && (form != POINT_CONVERSION_UNCOMPRESSED)
            && (form != POINT_CONVERSION_HYBRID)) {
                ECerror(EC_R_INVALID_FORM);
                goto err;
        }
        if (EC_POINT_is_at_infinity(group, point) > 0) {
                /* encodes to a single 0 octet */
                if (buf != NULL) {
                        if (len < 1) {
                                ECerror(EC_R_BUFFER_TOO_SMALL);
                                return 0;
                        }
                        buf[0] = 0;
                }
                return 1;
        }
        /* ret := required output buffer length */
        field_len = BN_num_bytes(&group->field);
        ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;

        /* if 'buf' is NULL, just return required length */
        if (buf != NULL) {
                if (len < ret) {
                        ECerror(EC_R_BUFFER_TOO_SMALL);
                        goto err;
                }
                if (ctx == NULL) {
                        ctx = new_ctx = BN_CTX_new();
                        if (ctx == NULL)
                                return 0;
                }
                BN_CTX_start(ctx);
                used_ctx = 1;
                if ((x = BN_CTX_get(ctx)) == NULL)
                        goto err;
                if ((y = BN_CTX_get(ctx)) == NULL)
                        goto err;

                if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
                        goto err;

                if ((form == POINT_CONVERSION_COMPRESSED || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y))
                        buf[0] = form + 1;
                else
                        buf[0] = form;

                i = 1;

                skip = field_len - BN_num_bytes(x);
                if (skip > field_len) {
                        ECerror(ERR_R_INTERNAL_ERROR);
                        goto err;
                }
                while (skip > 0) {
                        buf[i++] = 0;
                        skip--;
                }
                skip = BN_bn2bin(x, buf + i);
                i += skip;
                if (i != 1 + field_len) {
                        ECerror(ERR_R_INTERNAL_ERROR);
                        goto err;
                }
                if (form == POINT_CONVERSION_UNCOMPRESSED || form == POINT_CONVERSION_HYBRID) {
                        skip = field_len - BN_num_bytes(y);
                        if (skip > field_len) {
                                ECerror(ERR_R_INTERNAL_ERROR);
                                goto err;
                        }
                        while (skip > 0) {
                                buf[i++] = 0;
                                skip--;
                        }
                        skip = BN_bn2bin(y, buf + i);
                        i += skip;
                }
                if (i != ret) {
                        ECerror(ERR_R_INTERNAL_ERROR);
                        goto err;
                }
        }
        if (used_ctx)
                BN_CTX_end(ctx);
        BN_CTX_free(new_ctx);
        return ret;

 err:
        if (used_ctx)
                BN_CTX_end(ctx);
        BN_CTX_free(new_ctx);
        return 0;
}


int 
ec_GFp_simple_oct2point(const EC_GROUP * group, EC_POINT * point,
    const unsigned char *buf, size_t len, BN_CTX * ctx)
{
        point_conversion_form_t form;
        int y_bit;
        BN_CTX *new_ctx = NULL;
        BIGNUM *x, *y;
        size_t field_len, enc_len;
        int ret = 0;

        if (len == 0) {
                ECerror(EC_R_BUFFER_TOO_SMALL);
                return 0;
        }
        form = buf[0];
        y_bit = form & 1;
        form = form & ~1U;
        if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
            && (form != POINT_CONVERSION_UNCOMPRESSED)
            && (form != POINT_CONVERSION_HYBRID)) {
                ECerror(EC_R_INVALID_ENCODING);
                return 0;
        }
        if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
                ECerror(EC_R_INVALID_ENCODING);
                return 0;
        }
        if (form == 0) {
                if (len != 1) {
                        ECerror(EC_R_INVALID_ENCODING);
                        return 0;
                }
                return EC_POINT_set_to_infinity(group, point);
        }
        field_len = BN_num_bytes(&group->field);
        enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;

        if (len != enc_len) {
                ECerror(EC_R_INVALID_ENCODING);
                return 0;
        }
        if (ctx == NULL) {
                ctx = new_ctx = BN_CTX_new();
                if (ctx == NULL)
                        return 0;
        }
        BN_CTX_start(ctx);
        if ((x = BN_CTX_get(ctx)) == NULL)
                goto err;
        if ((y = BN_CTX_get(ctx)) == NULL)
                goto err;

        if (!BN_bin2bn(buf + 1, field_len, x))
                goto err;
        if (BN_ucmp(x, &group->field) >= 0) {
                ECerror(EC_R_INVALID_ENCODING);
                goto err;
        }
        if (form == POINT_CONVERSION_COMPRESSED) {
                /*
                 * EC_POINT_set_compressed_coordinates checks that the point
                 * is on the curve as required by X9.62.
                 */
                if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
                        goto err;
        } else {
                if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
                        goto err;
                if (BN_ucmp(y, &group->field) >= 0) {
                        ECerror(EC_R_INVALID_ENCODING);
                        goto err;
                }
                if (form == POINT_CONVERSION_HYBRID) {
                        if (y_bit != BN_is_odd(y)) {
                                ECerror(EC_R_INVALID_ENCODING);
                                goto err;
                        }
                }
                /*
                 * EC_POINT_set_affine_coordinates checks that the point is
                 * on the curve as required by X9.62.
                 */
                if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
                        goto err;
        }

        ret = 1;

 err:
        BN_CTX_end(ctx);
        BN_CTX_free(new_ctx);
        return ret;
}