[thirdparty/openssl.git] / crypto / ec / ec2_oct.c

/* crypto/ec/ec2_oct.c */
/* ====================================================================
 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
 *
 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
 * to the OpenSSL project.
 *
 * The ECC Code is licensed pursuant to the OpenSSL open source
 * license provided below.
 *
 * The software is originally written by Sheueling Chang Shantz and
 * Douglas Stebila of Sun Microsystems Laboratories.
 *
 */
/* ====================================================================
 * Copyright (c) 1998-2019 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).
 *
 */

#include <openssl/err.h>

#include "ec_lcl.h"

#ifndef OPENSSL_NO_EC2M

/*-
 * Calculates and sets the affine coordinates of an EC_POINT from the given
 * compressed coordinates.  Uses algorithm 2.3.4 of SEC 1.
 * Note that the simple implementation only uses affine coordinates.
 *
 * The method is from the following publication:
 *
 *     Harper, Menezes, Vanstone:
 *     "Public-Key Cryptosystems with Very Small Key Lengths",
 *     EUROCRYPT '92, Springer-Verlag LNCS 658,
 *     published February 1993
 *
 * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
 * the same method, but claim no priority date earlier than July 29, 1994
 * (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
 */
int ec_GF2m_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 *tmp, *x, *y, *z;
    int ret = 0, z0;

    /* 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) ? 1 : 0;

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

    if (!BN_GF2m_mod_arr(x, x_, group->poly))
        goto err;
    if (BN_is_zero(x)) {
        if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx))
            goto err;
    } else {
        if (!group->meth->field_sqr(group, tmp, x, ctx))
            goto err;
        if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx))
            goto err;
        if (!BN_GF2m_add(tmp, &group->a, tmp))
            goto err;
        if (!BN_GF2m_add(tmp, x, tmp))
            goto err;
        if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
            unsigned long err = ERR_peek_last_error();

            if (ERR_GET_LIB(err) == ERR_LIB_BN
                && ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
                ERR_clear_error();
                ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
                      EC_R_INVALID_COMPRESSED_POINT);
            } else
                ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
                      ERR_R_BN_LIB);
            goto err;
        }
        z0 = (BN_is_odd(z)) ? 1 : 0;
        if (!group->meth->field_mul(group, y, x, z, ctx))
            goto err;
        if (z0 != y_bit) {
            if (!BN_GF2m_add(y, y, x))
                goto err;
        }
    }

    if (!EC_POINT_set_affine_coordinates_GF2m(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;
}

/*
 * Converts an EC_POINT to an octet string. If buf is NULL, the encoded
 * length will be returned. If the length len of buf is smaller than required
 * an error will be returned.
 */
size_t ec_GF2m_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, *yxi;
    size_t field_len, i, skip;

    if ((form != POINT_CONVERSION_COMPRESSED)
        && (form != POINT_CONVERSION_UNCOMPRESSED)
        && (form != POINT_CONVERSION_HYBRID)) {
        ECerr(EC_F_EC_GF2M_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_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
                return 0;
            }
            buf[0] = 0;
        }
        return 1;
    }

    /* ret := required output buffer length */
    field_len = (EC_GROUP_get_degree(group) + 7) / 8;
    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_GF2M_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);
        yxi = BN_CTX_get(ctx);
        if (yxi == NULL)
            goto err;

        if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))
            goto err;

        buf[0] = form;
        if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
            if (!group->meth->field_div(group, yxi, y, x, ctx))
                goto err;
            if (BN_is_odd(yxi))
                buf[0]++;
        }

        i = 1;

        skip = field_len - BN_num_bytes(x);
        if (skip > field_len) {
            ECerr(EC_F_EC_GF2M_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_GF2M_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_GF2M_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_GF2M_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;
}

/*
 * Converts an octet string representation to an EC_POINT. Note that the
 * simple implementation only uses affine coordinates.
 */
int ec_GF2m_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, m;
    BN_CTX *new_ctx = NULL;
    BIGNUM *x, *y, *yxi;
    size_t field_len, enc_len;
    int ret = 0;

    if (len == 0) {
        ECerr(EC_F_EC_GF2M_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_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        return 0;
    }
    if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        return 0;
    }

    if (form == 0) {
        if (len != 1) {
            ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
            return 0;
        }

        return EC_POINT_set_to_infinity(group, point);
    }

    m = EC_GROUP_get_degree(group);
    field_len = (m + 7) / 8;
    enc_len =
        (form ==
         POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;

    if (len != enc_len) {
        ECerr(EC_F_EC_GF2M_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);
    yxi = BN_CTX_get(ctx);
    if (yxi == NULL)
        goto err;

    if (!BN_bin2bn(buf + 1, field_len, x))
        goto err;
    if (BN_num_bits(x) > m) {
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
        goto err;
    }

    if (form == POINT_CONVERSION_COMPRESSED) {
        if (!EC_POINT_set_compressed_coordinates_GF2m
            (group, point, x, y_bit, ctx))
            goto err;
    } else {
        if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
            goto err;
        if (BN_num_bits(y) > m) {
            ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
            goto err;
        }
        if (form == POINT_CONVERSION_HYBRID) {
            if (!group->meth->field_div(group, yxi, y, x, ctx))
                goto err;
            if (y_bit != BN_is_odd(yxi)) {
                ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
                goto err;
            }
        }

        /*
         * EC_POINT_set_affine_coordinates_GF2m is responsible for checking that
         * the point is on the curve.
         */
        if (!EC_POINT_set_affine_coordinates_GF2m(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;
}
#endif
Commit	Line	Data
69e2ec63 DSH	1	/* crypto/ec/ec2_oct.c */
	2	/* ====================================================================
	3	* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
	4	*
	5	* The Elliptic Curve Public-Key Crypto Library (ECC Code) included
	6	* herein is developed by SUN MICROSYSTEMS, INC., and is contributed
	7	* to the OpenSSL project.
	8	*
	9	* The ECC Code is licensed pursuant to the OpenSSL open source
	10	* license provided below.
	11	*
	12	* The software is originally written by Sheueling Chang Shantz and
	13	* Douglas Stebila of Sun Microsystems Laboratories.
	14	*
	15	*/
	16	/* ====================================================================
66c236c4	17	* Copyright (c) 1998-2019 The OpenSSL Project. All rights reserved.
69e2ec63 DSH	18	*
	19	* Redistribution and use in source and binary forms, with or without
	20	* modification, are permitted provided that the following conditions
	21	* are met:
	22	*
	23	* 1. Redistributions of source code must retain the above copyright
ae5c8664	24	* notice, this list of conditions and the following disclaimer.
69e2ec63 DSH	25	*
	26	* 2. Redistributions in binary form must reproduce the above copyright
	27	* notice, this list of conditions and the following disclaimer in
	28	* the documentation and/or other materials provided with the
	29	* distribution.
	30	*
	31	* 3. All advertising materials mentioning features or use of this
	32	* software must display the following acknowledgment:
	33	* "This product includes software developed by the OpenSSL Project
	34	* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
	35	*
	36	* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
	37	* endorse or promote products derived from this software without
	38	* prior written permission. For written permission, please contact
	39	* openssl-core@openssl.org.
	40	*
	41	* 5. Products derived from this software may not be called "OpenSSL"
	42	* nor may "OpenSSL" appear in their names without prior written
	43	* permission of the OpenSSL Project.
	44	*
	45	* 6. Redistributions of any form whatsoever must retain the following
	46	* acknowledgment:
	47	* "This product includes software developed by the OpenSSL Project
	48	* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
	49	*
	50	* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
	51	* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	52	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	53	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
	54	* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	55	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	56	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	57	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	58	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
	59	* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	60	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
	61	* OF THE POSSIBILITY OF SUCH DAMAGE.
	62	* ====================================================================
	63	*
	64	* This product includes cryptographic software written by Eric Young
	65	* (eay@cryptsoft.com). This product includes software written by Tim
	66	* Hudson (tjh@cryptsoft.com).
	67	*
	68	*/
	69
	70	#include <openssl/err.h>
	71
	72	#include "ec_lcl.h"
	73
	74	#ifndef OPENSSL_NO_EC2M
	75
e19d4a99 MC	76	/*-
e19d4a99 MC	77	* Calculates and sets the affine coordinates of an EC_POINT from the given
ae5c8664	78	* compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
69e2ec63 DSH	79	* Note that the simple implementation only uses affine coordinates.
	80	*
	81	* The method is from the following publication:
ae5c8664	82	*
69e2ec63 DSH	83	* Harper, Menezes, Vanstone:
	84	* "Public-Key Cryptosystems with Very Small Key Lengths",
	85	* EUROCRYPT '92, Springer-Verlag LNCS 658,
	86	* published February 1993
	87	*
	88	* US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
	89	* the same method, but claim no priority date earlier than July 29, 1994
	90	* (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
	91	*/
ae5c8664 MC	92	int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group,
	93	EC_POINT *point,
	94	const BIGNUM *x_, int y_bit,
	95	BN_CTX *ctx)
	96	{
	97	BN_CTX *new_ctx = NULL;
	98	BIGNUM tmp, x, y, z;
	99	int ret = 0, z0;
	100
	101	/* clear error queue */
	102	ERR_clear_error();
	103
	104	if (ctx == NULL) {
	105	ctx = new_ctx = BN_CTX_new();
	106	if (ctx == NULL)
	107	return 0;
	108	}
	109
	110	y_bit = (y_bit != 0) ? 1 : 0;
	111
	112	BN_CTX_start(ctx);
	113	tmp = BN_CTX_get(ctx);
	114	x = BN_CTX_get(ctx);
	115	y = BN_CTX_get(ctx);
	116	z = BN_CTX_get(ctx);
	117	if (z == NULL)
	118	goto err;
	119
	120	if (!BN_GF2m_mod_arr(x, x_, group->poly))
	121	goto err;
	122	if (BN_is_zero(x)) {
	123	if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx))
	124	goto err;
	125	} else {
	126	if (!group->meth->field_sqr(group, tmp, x, ctx))
	127	goto err;
	128	if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx))
	129	goto err;
	130	if (!BN_GF2m_add(tmp, &group->a, tmp))
	131	goto err;
	132	if (!BN_GF2m_add(tmp, x, tmp))
	133	goto err;
	134	if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
	135	unsigned long err = ERR_peek_last_error();
	136
	137	if (ERR_GET_LIB(err) == ERR_LIB_BN
	138	&& ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
	139	ERR_clear_error();
	140	ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
	141	EC_R_INVALID_COMPRESSED_POINT);
	142	} else
	143	ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
	144	ERR_R_BN_LIB);
	145	goto err;
	146	}
	147	z0 = (BN_is_odd(z)) ? 1 : 0;
	148	if (!group->meth->field_mul(group, y, x, z, ctx))
	149	goto err;
	150	if (z0 != y_bit) {
	151	if (!BN_GF2m_add(y, y, x))
	152	goto err;
	153	}
	154	}
	155
156	if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
157	goto err;
158
159	ret = 1;
69e2ec63 DSH	160
69e2ec63 DSH	161	err:
ae5c8664 MC	162	BN_CTX_end(ctx);
	163	if (new_ctx != NULL)
	164	BN_CTX_free(new_ctx);
	165	return ret;
	166	}
	167
	168	/*
	169	* Converts an EC_POINT to an octet string. If buf is NULL, the encoded
	170	* length will be returned. If the length len of buf is smaller than required
	171	* an error will be returned.
69e2ec63	172	*/
ae5c8664 MC	173	size_t ec_GF2m_simple_point2oct(const EC_GROUP group, const EC_POINT point,
	174	point_conversion_form_t form,
	175	unsigned char buf, size_t len, BN_CTX ctx)
	176	{
	177	size_t ret;
	178	BN_CTX *new_ctx = NULL;
	179	int used_ctx = 0;
	180	BIGNUM x, y, *yxi;
	181	size_t field_len, i, skip;
	182
	183	if ((form != POINT_CONVERSION_COMPRESSED)
	184	&& (form != POINT_CONVERSION_UNCOMPRESSED)
	185	&& (form != POINT_CONVERSION_HYBRID)) {
	186	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
	187	goto err;
	188	}
	189
	190	if (EC_POINT_is_at_infinity(group, point)) {
	191	/* encodes to a single 0 octet */
	192	if (buf != NULL) {
	193	if (len < 1) {
	194	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
	195	return 0;
	196	}
	197	buf[0] = 0;
	198	}
	199	return 1;
	200	}
	201
	202	/* ret := required output buffer length */
	203	field_len = (EC_GROUP_get_degree(group) + 7) / 8;
	204	ret =
	205	(form ==
	206	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
	207
	208	/* if 'buf' is NULL, just return required length */
	209	if (buf != NULL) {
	210	if (len < ret) {
	211	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
	212	goto err;
	213	}
	214
	215	if (ctx == NULL) {
	216	ctx = new_ctx = BN_CTX_new();
	217	if (ctx == NULL)
	218	return 0;
	219	}
	220
	221	BN_CTX_start(ctx);
	222	used_ctx = 1;
	223	x = BN_CTX_get(ctx);
	224	y = BN_CTX_get(ctx);
	225	yxi = BN_CTX_get(ctx);
	226	if (yxi == NULL)
	227	goto err;
	228
	229	if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))
	230	goto err;
	231
	232	buf[0] = form;
	233	if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
	234	if (!group->meth->field_div(group, yxi, y, x, ctx))
	235	goto err;
	236	if (BN_is_odd(yxi))
237	buf[0]++;
238	}
239
240	i = 1;
241
242	skip = field_len - BN_num_bytes(x);
243	if (skip > field_len) {
244	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
245	goto err;
246	}
247	while (skip > 0) {
248	buf[i++] = 0;
249	skip--;
250	}
251	skip = BN_bn2bin(x, buf + i);
252	i += skip;
253	if (i != 1 + field_len) {
254	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
255	goto err;
256	}
257
258	if (form == POINT_CONVERSION_UNCOMPRESSED
259	\|\| form == POINT_CONVERSION_HYBRID) {
260	skip = field_len - BN_num_bytes(y);
261	if (skip > field_len) {
262	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
263	goto err;
264	}
265	while (skip > 0) {
266	buf[i++] = 0;
267	skip--;
268	}
269	skip = BN_bn2bin(y, buf + i);
270	i += skip;
271	}
272
273	if (i != ret) {
274	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
275	goto err;
276	}
277	}
278
279	if (used_ctx)
280	BN_CTX_end(ctx);
281	if (new_ctx != NULL)
282	BN_CTX_free(new_ctx);
283	return ret;
69e2ec63 DSH	284
69e2ec63 DSH	285	err:
ae5c8664 MC	286	if (used_ctx)
	287	BN_CTX_end(ctx);
	288	if (new_ctx != NULL)
	289	BN_CTX_free(new_ctx);
	290	return 0;
	291	}
	292
	293	/*
	294	* Converts an octet string representation to an EC_POINT. Note that the
	295	* simple implementation only uses affine coordinates.
69e2ec63 DSH	296	*/
69e2ec63 DSH	297	int ec_GF2m_simple_oct2point(const EC_GROUP group, EC_POINT point,
ae5c8664 MC	298	const unsigned char *buf, size_t len,
	299	BN_CTX *ctx)
	300	{
	301	point_conversion_form_t form;
d3299a33	302	int y_bit, m;
ae5c8664 MC	303	BN_CTX *new_ctx = NULL;
	304	BIGNUM x, y, *yxi;
	305	size_t field_len, enc_len;
	306	int ret = 0;
	307
	308	if (len == 0) {
	309	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
	310	return 0;
	311	}
	312	form = buf[0];
	313	y_bit = form & 1;
	314	form = form & ~1U;
	315	if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
	316	&& (form != POINT_CONVERSION_UNCOMPRESSED)
	317	&& (form != POINT_CONVERSION_HYBRID)) {
	318	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	319	return 0;
	320	}
	321	if ((form == 0 \|\| form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
	322	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	323	return 0;
	324	}
	325
	326	if (form == 0) {
	327	if (len != 1) {
	328	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	329	return 0;
	330	}
	331
	332	return EC_POINT_set_to_infinity(group, point);
	333	}
	334
d3299a33 SL	335	m = EC_GROUP_get_degree(group);
d3299a33 SL	336	field_len = (m + 7) / 8;
ae5c8664 MC	337	enc_len =
	338	(form ==
	339	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
	340
	341	if (len != enc_len) {
	342	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	343	return 0;
	344	}
	345
	346	if (ctx == NULL) {
	347	ctx = new_ctx = BN_CTX_new();
	348	if (ctx == NULL)
	349	return 0;
	350	}
	351
	352	BN_CTX_start(ctx);
	353	x = BN_CTX_get(ctx);
	354	y = BN_CTX_get(ctx);
	355	yxi = BN_CTX_get(ctx);
	356	if (yxi == NULL)
	357	goto err;
	358
	359	if (!BN_bin2bn(buf + 1, field_len, x))
	360	goto err;
d3299a33	361	if (BN_num_bits(x) > m) {
ae5c8664 MC	362	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	363	goto err;
	364	}
	365
	366	if (form == POINT_CONVERSION_COMPRESSED) {
	367	if (!EC_POINT_set_compressed_coordinates_GF2m
	368	(group, point, x, y_bit, ctx))
	369	goto err;
	370	} else {
	371	if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
	372	goto err;
d3299a33	373	if (BN_num_bits(y) > m) {
ae5c8664 MC	374	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	375	goto err;
	376	}
	377	if (form == POINT_CONVERSION_HYBRID) {
	378	if (!group->meth->field_div(group, yxi, y, x, ctx))
	379	goto err;
	380	if (y_bit != BN_is_odd(yxi)) {
	381	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	382	goto err;
	383	}
	384	}
	385
cea83f9f EK	386	/*
	387	* EC_POINT_set_affine_coordinates_GF2m is responsible for checking that
	388	* the point is on the curve.
	389	*/
ae5c8664 MC	390	if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
	391	goto err;
	392	}
	393
ae5c8664 MC	394	ret = 1;
ae5c8664 MC	395
69e2ec63	396	err:
ae5c8664 MC	397	BN_CTX_end(ctx);
	398	if (new_ctx != NULL)
	399	BN_CTX_free(new_ctx);
	400	return ret;
	401	}
69e2ec63	402	#endif