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

/*
 * Copyright 2011-2020 The OpenSSL Project Authors. All Rights Reserved.
 * Copyright (c) 2002, Oracle and/or its affiliates. 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 <openssl/err.h>

#include "ec_local.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)
{
    BIGNUM *tmp, *x, *y, *z;
    int ret = 0, z0;
#ifndef FIPS_MODE
    BN_CTX *new_ctx = NULL;

    /* clear error queue */
    ERR_clear_error();

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

    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)) {
#ifndef FIPS_MODE
            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
#endif
            {
                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(group, point, x, y, ctx))
        goto err;

    ret = 1;

 err:
    BN_CTX_end(ctx);
#ifndef FIPS_MODE
    BN_CTX_free(new_ctx);
#endif
    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;
    int used_ctx = 0;
    BIGNUM *x, *y, *yxi;
    size_t field_len, i, skip;
#ifndef FIPS_MODE
    BN_CTX *new_ctx = NULL;
#endif

    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;
        }

#ifndef FIPS_MODE
        if (ctx == NULL) {
            ctx = new_ctx = BN_CTX_new();
            if (ctx == NULL)
                return 0;
        }
#endif

        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(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);
#ifndef FIPS_MODE
    BN_CTX_free(new_ctx);
#endif
    return ret;

 err:
    if (used_ctx)
        BN_CTX_end(ctx);
#ifndef FIPS_MODE
    BN_CTX_free(new_ctx);
#endif
    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;
    BIGNUM *x, *y, *yxi;
    size_t field_len, enc_len;
    int ret = 0;
#ifndef FIPS_MODE
    BN_CTX *new_ctx = NULL;
#endif

    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;
    }

#ifndef FIPS_MODE
    if (ctx == NULL) {
        ctx = new_ctx = BN_CTX_new();
        if (ctx == NULL)
            return 0;
    }
#endif

    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(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 is responsible for checking that
         * the point is on the curve.
         */
        if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
            goto err;
    }

    ret = 1;

 err:
    BN_CTX_end(ctx);
#ifndef FIPS_MODE
    BN_CTX_free(new_ctx);
#endif
    return ret;
}
#endif
Commit	Line	Data
aa6bb135	1	/*
33388b44	2	* Copyright 2011-2020 The OpenSSL Project Authors. All Rights Reserved.
aa8f3d76	3	* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
aa6bb135	4	*
a7f182b7	5	* Licensed under the Apache License 2.0 (the "License"). You may not use
aa6bb135 RS	6	* this file except in compliance with the License. You can obtain a copy
	7	* in the file LICENSE in the source distribution or at
	8	* https://www.openssl.org/source/license.html
	9	*/
	10
579422c8 P	11	/*
	12	* ECDSA low level APIs are deprecated for public use, but still ok for
	13	* internal use.
	14	*/
	15	#include "internal/deprecated.h"
	16
84b08eee DSH	17	#include <openssl/err.h>
84b08eee DSH	18
706457b7	19	#include "ec_local.h"
84b08eee DSH	20
	21	#ifndef OPENSSL_NO_EC2M
	22
3a83462d MC	23	/*-
3a83462d MC	24	* Calculates and sets the affine coordinates of an EC_POINT from the given
0f113f3e	25	* compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
84b08eee DSH	26	* Note that the simple implementation only uses affine coordinates.
	27	*
	28	* The method is from the following publication:
0f113f3e	29	*
84b08eee DSH	30	* Harper, Menezes, Vanstone:
	31	* "Public-Key Cryptosystems with Very Small Key Lengths",
	32	* EUROCRYPT '92, Springer-Verlag LNCS 658,
	33	* published February 1993
	34	*
	35	* US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
	36	* the same method, but claim no priority date earlier than July 29, 1994
	37	* (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
	38	*/
0f113f3e MC	39	int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group,
	40	EC_POINT *point,
	41	const BIGNUM *x_, int y_bit,
	42	BN_CTX *ctx)
	43	{
0f113f3e MC	44	BIGNUM tmp, x, y, z;
0f113f3e MC	45	int ret = 0, z0;
a9612d6c MC	46	#ifndef FIPS_MODE
a9612d6c MC	47	BN_CTX *new_ctx = NULL;
0f113f3e MC	48
	49	/* clear error queue */
	50	ERR_clear_error();
	51
	52	if (ctx == NULL) {
	53	ctx = new_ctx = BN_CTX_new();
	54	if (ctx == NULL)
	55	return 0;
	56	}
a9612d6c	57	#endif
0f113f3e MC	58
	59	y_bit = (y_bit != 0) ? 1 : 0;
	60
	61	BN_CTX_start(ctx);
	62	tmp = BN_CTX_get(ctx);
	63	x = BN_CTX_get(ctx);
	64	y = BN_CTX_get(ctx);
	65	z = BN_CTX_get(ctx);
	66	if (z == NULL)
	67	goto err;
	68
	69	if (!BN_GF2m_mod_arr(x, x_, group->poly))
	70	goto err;
	71	if (BN_is_zero(x)) {
	72	if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx))
	73	goto err;
	74	} else {
	75	if (!group->meth->field_sqr(group, tmp, x, ctx))
	76	goto err;
	77	if (!group->meth->field_div(group, tmp, group->b, tmp, ctx))
	78	goto err;
	79	if (!BN_GF2m_add(tmp, group->a, tmp))
	80	goto err;
	81	if (!BN_GF2m_add(tmp, x, tmp))
	82	goto err;
	83	if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
a9612d6c	84	#ifndef FIPS_MODE
0f113f3e MC	85	unsigned long err = ERR_peek_last_error();
	86
	87	if (ERR_GET_LIB(err) == ERR_LIB_BN
	88	&& ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
	89	ERR_clear_error();
	90	ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
	91	EC_R_INVALID_COMPRESSED_POINT);
	92	} else
a9612d6c MC	93	#endif
a9612d6c MC	94	{
0f113f3e MC	95	ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
0f113f3e MC	96	ERR_R_BN_LIB);
a9612d6c	97	}
0f113f3e MC	98	goto err;
	99	}
	100	z0 = (BN_is_odd(z)) ? 1 : 0;
	101	if (!group->meth->field_mul(group, y, x, z, ctx))
	102	goto err;
	103	if (z0 != y_bit) {
	104	if (!BN_GF2m_add(y, y, x))
	105	goto err;
	106	}
	107	}
	108
9cc570d4	109	if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
0f113f3e MC	110	goto err;
	111
	112	ret = 1;
84b08eee DSH	113
84b08eee DSH	114	err:
0f113f3e	115	BN_CTX_end(ctx);
a9612d6c	116	#ifndef FIPS_MODE
23a1d5e9	117	BN_CTX_free(new_ctx);
a9612d6c	118	#endif
0f113f3e MC	119	return ret;
	120	}
	121
	122	/*
	123	* Converts an EC_POINT to an octet string. If buf is NULL, the encoded
	124	* length will be returned. If the length len of buf is smaller than required
	125	* an error will be returned.
84b08eee	126	*/
0f113f3e MC	127	size_t ec_GF2m_simple_point2oct(const EC_GROUP group, const EC_POINT point,
	128	point_conversion_form_t form,
	129	unsigned char buf, size_t len, BN_CTX ctx)
	130	{
	131	size_t ret;
0f113f3e MC	132	int used_ctx = 0;
	133	BIGNUM x, y, *yxi;
	134	size_t field_len, i, skip;
a9612d6c MC	135	#ifndef FIPS_MODE
	136	BN_CTX *new_ctx = NULL;
	137	#endif
0f113f3e MC	138
	139	if ((form != POINT_CONVERSION_COMPRESSED)
	140	&& (form != POINT_CONVERSION_UNCOMPRESSED)
	141	&& (form != POINT_CONVERSION_HYBRID)) {
	142	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
	143	goto err;
	144	}
	145
	146	if (EC_POINT_is_at_infinity(group, point)) {
	147	/* encodes to a single 0 octet */
	148	if (buf != NULL) {
	149	if (len < 1) {
	150	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
	151	return 0;
	152	}
	153	buf[0] = 0;
	154	}
	155	return 1;
	156	}
	157
	158	/* ret := required output buffer length */
	159	field_len = (EC_GROUP_get_degree(group) + 7) / 8;
	160	ret =
	161	(form ==
	162	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
	163
	164	/* if 'buf' is NULL, just return required length */
	165	if (buf != NULL) {
	166	if (len < ret) {
	167	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
	168	goto err;
	169	}
	170
a9612d6c	171	#ifndef FIPS_MODE
0f113f3e MC	172	if (ctx == NULL) {
	173	ctx = new_ctx = BN_CTX_new();
	174	if (ctx == NULL)
	175	return 0;
	176	}
a9612d6c	177	#endif
0f113f3e MC	178
	179	BN_CTX_start(ctx);
	180	used_ctx = 1;
	181	x = BN_CTX_get(ctx);
	182	y = BN_CTX_get(ctx);
	183	yxi = BN_CTX_get(ctx);
	184	if (yxi == NULL)
	185	goto err;
	186
9cc570d4	187	if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
0f113f3e MC	188	goto err;
	189
	190	buf[0] = form;
	191	if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
	192	if (!group->meth->field_div(group, yxi, y, x, ctx))
	193	goto err;
	194	if (BN_is_odd(yxi))
	195	buf[0]++;
	196	}
	197
	198	i = 1;
	199
	200	skip = field_len - BN_num_bytes(x);
	201	if (skip > field_len) {
	202	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
	203	goto err;
	204	}
	205	while (skip > 0) {
	206	buf[i++] = 0;
	207	skip--;
	208	}
	209	skip = BN_bn2bin(x, buf + i);
	210	i += skip;
	211	if (i != 1 + field_len) {
	212	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
	213	goto err;
	214	}
	215
	216	if (form == POINT_CONVERSION_UNCOMPRESSED
	217	\|\| form == POINT_CONVERSION_HYBRID) {
	218	skip = field_len - BN_num_bytes(y);
	219	if (skip > field_len) {
	220	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
	221	goto err;
	222	}
	223	while (skip > 0) {
	224	buf[i++] = 0;
	225	skip--;
	226	}
	227	skip = BN_bn2bin(y, buf + i);
	228	i += skip;
	229	}
	230
	231	if (i != ret) {
	232	ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
	233	goto err;
	234	}
	235	}
	236
	237	if (used_ctx)
	238	BN_CTX_end(ctx);
a9612d6c	239	#ifndef FIPS_MODE
23a1d5e9	240	BN_CTX_free(new_ctx);
a9612d6c	241	#endif
0f113f3e	242	return ret;
84b08eee DSH	243
84b08eee DSH	244	err:
0f113f3e MC	245	if (used_ctx)
0f113f3e MC	246	BN_CTX_end(ctx);
a9612d6c	247	#ifndef FIPS_MODE
23a1d5e9	248	BN_CTX_free(new_ctx);
a9612d6c	249	#endif
0f113f3e MC	250	return 0;
	251	}
	252
	253	/*
	254	* Converts an octet string representation to an EC_POINT. Note that the
	255	* simple implementation only uses affine coordinates.
84b08eee DSH	256	*/
84b08eee DSH	257	int ec_GF2m_simple_oct2point(const EC_GROUP group, EC_POINT point,
0f113f3e MC	258	const unsigned char *buf, size_t len,
	259	BN_CTX *ctx)
	260	{
	261	point_conversion_form_t form;
cad8347b	262	int y_bit, m;
0f113f3e MC	263	BIGNUM x, y, *yxi;
	264	size_t field_len, enc_len;
	265	int ret = 0;
a9612d6c MC	266	#ifndef FIPS_MODE
	267	BN_CTX *new_ctx = NULL;
	268	#endif
0f113f3e MC	269
	270	if (len == 0) {
	271	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
	272	return 0;
	273	}
	274	form = buf[0];
	275	y_bit = form & 1;
	276	form = form & ~1U;
	277	if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
	278	&& (form != POINT_CONVERSION_UNCOMPRESSED)
	279	&& (form != POINT_CONVERSION_HYBRID)) {
	280	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	281	return 0;
	282	}
	283	if ((form == 0 \|\| form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
	284	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	285	return 0;
	286	}
	287
	288	if (form == 0) {
	289	if (len != 1) {
	290	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	291	return 0;
	292	}
	293
	294	return EC_POINT_set_to_infinity(group, point);
	295	}
	296
cad8347b SL	297	m = EC_GROUP_get_degree(group);
cad8347b SL	298	field_len = (m + 7) / 8;
0f113f3e MC	299	enc_len =
	300	(form ==
	301	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
	302
	303	if (len != enc_len) {
	304	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	305	return 0;
	306	}
	307
a9612d6c	308	#ifndef FIPS_MODE
0f113f3e MC	309	if (ctx == NULL) {
	310	ctx = new_ctx = BN_CTX_new();
	311	if (ctx == NULL)
	312	return 0;
	313	}
a9612d6c	314	#endif
0f113f3e MC	315
	316	BN_CTX_start(ctx);
	317	x = BN_CTX_get(ctx);
	318	y = BN_CTX_get(ctx);
	319	yxi = BN_CTX_get(ctx);
	320	if (yxi == NULL)
	321	goto err;
	322
	323	if (!BN_bin2bn(buf + 1, field_len, x))
	324	goto err;
cad8347b	325	if (BN_num_bits(x) > m) {
0f113f3e MC	326	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	327	goto err;
	328	}
	329
	330	if (form == POINT_CONVERSION_COMPRESSED) {
9cc570d4	331	if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
0f113f3e MC	332	goto err;
	333	} else {
	334	if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
	335	goto err;
cad8347b	336	if (BN_num_bits(y) > m) {
0f113f3e MC	337	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	338	goto err;
	339	}
	340	if (form == POINT_CONVERSION_HYBRID) {
	341	if (!group->meth->field_div(group, yxi, y, x, ctx))
	342	goto err;
	343	if (y_bit != BN_is_odd(yxi)) {
	344	ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
	345	goto err;
	346	}
	347	}
	348
1e2012b7	349	/*
9cc570d4	350	* EC_POINT_set_affine_coordinates is responsible for checking that
1e2012b7 EK	351	* the point is on the curve.
1e2012b7 EK	352	*/
9cc570d4	353	if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
0f113f3e MC	354	goto err;
	355	}
	356
0f113f3e MC	357	ret = 1;
0f113f3e MC	358
84b08eee	359	err:
0f113f3e	360	BN_CTX_end(ctx);
a9612d6c	361	#ifndef FIPS_MODE
23a1d5e9	362	BN_CTX_free(new_ctx);
a9612d6c	363	#endif
0f113f3e MC	364	return ret;
0f113f3e MC	365	}
84b08eee	366	#endif