ecp_oct.c

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/* crypto/ec/ecp_oct.c */
/* Includes code written by Lenka Fibikova <[email protected]>
 * 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
 *    [email protected].
 *
 * 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
 * ([email protected]).  This product includes software written by Tim
 * Hudson ([email protected]).
 *
 */
/* ====================================================================
 * 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 <openssl/symhacks.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);
    tmp1 = BN_CTX_get(ctx);
    tmp2 = BN_CTX_get(ctx);
    x = BN_CTX_get(ctx);
    y = BN_CTX_get(ctx);
    if (y == 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();
            ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT);
            }
        else
            ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, 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)
                ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSION_BIT);
            else
                /* BN_mod_sqrt() should have cought this error (not a square) */
                ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT);
            goto err;
            }
        if (!BN_usub(y, &group->field, y)) goto err;
        }
    if (y_bit != BN_is_odd(y))
        {
        ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_INTERNAL_ERROR);
        goto err;
        }

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

    ret = 1;

 err:
    BN_CTX_end(ctx);
    if (new_ctx != NULL)
        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))
        {
        ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
        goto err;
        }

    if (EC_POINT_is_at_infinity(group, point))
        {
        /* encodes to a single 0 octet */
        if (buf != NULL)
            {
            if (len < 1)
                {
                ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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)
            {
            ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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;
        x = BN_CTX_get(ctx);
        y = BN_CTX_get(ctx);
        if (y == NULL) goto err;

        if (!EC_POINT_get_affine_coordinates_GFp(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)
            {
            ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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)
            {
            ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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)
                {
                ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
                goto err;
                }
            while (skip > 0)
                {
                buf[i++] = 0;
                skip--;
                }
            skip = BN_bn2bin(y, buf + i);
            i += skip;
            }

        if (i != ret)
            {
            ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
            goto err;
            }
        }
    
    if (used_ctx)
        BN_CTX_end(ctx);
    if (new_ctx != NULL)
        BN_CTX_free(new_ctx);
    return ret;

 err:
    if (used_ctx)
        BN_CTX_end(ctx);
    if (new_ctx != NULL)
        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)
        {
        ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, 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))
        {
        ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        return 0;
        }
    if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit)
        {
        ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        return 0;
        }

    if (form == 0)
        {
        if (len != 1)
            {
            ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, 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)
        {
        ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        return 0;
        }

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

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

    if (!BN_bin2bn(buf + 1, field_len, x)) goto err;
    if (BN_ucmp(x, &group->field) >= 0)
        {
        ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        goto err;
        }

    if (form == POINT_CONVERSION_COMPRESSED)
        {
        if (!EC_POINT_set_compressed_coordinates_GFp(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)
            {
            ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
            goto err;
            }
        if (form == POINT_CONVERSION_HYBRID)
            {
            if (y_bit != BN_is_odd(y))
                {
                ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
                goto err;
                }
            }

        if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err;
        }
    
    if (!EC_POINT_is_on_curve(group, point, ctx)) /* test required by X9.62 */
        {
        ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
        goto err;
        }

    ret = 1;
    
 err:
    BN_CTX_end(ctx);
    if (new_ctx != NULL)
        BN_CTX_free(new_ctx);
    return ret;
    }