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

/*
 * Copyright 2011-2022 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 ossl_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_MODULE
    BN_CTX *new_ctx = NULL;

    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;
        ERR_set_mark();
        if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
#ifndef FIPS_MODULE
            unsigned long err = ERR_peek_last_error();

            if (ERR_GET_LIB(err) == ERR_LIB_BN
                && ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
                ERR_pop_to_mark();
                ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
            } else
#endif
            {
                ERR_clear_last_mark();
                ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
            }
            goto err;
        }
        ERR_clear_last_mark();
        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_MODULE
    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 ossl_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_MODULE
    BN_CTX *new_ctx = NULL;
#endif

    if ((form != POINT_CONVERSION_COMPRESSED)
        && (form != POINT_CONVERSION_UNCOMPRESSED)
        && (form != POINT_CONVERSION_HYBRID)) {
        ERR_raise(ERR_LIB_EC, 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) {
                ERR_raise(ERR_LIB_EC, 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) {
            ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
            goto err;
        }

#ifndef FIPS_MODULE
        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) {
            ERR_raise(ERR_LIB_EC, 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) {
            ERR_raise(ERR_LIB_EC, 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) {
                ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
                goto err;
            }
            while (skip > 0) {
                buf[i++] = 0;
                skip--;
            }
            skip = BN_bn2bin(y, buf + i);
            i += skip;
        }

        if (i != ret) {
            ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
            goto err;
        }
    }

    if (used_ctx)
        BN_CTX_end(ctx);
#ifndef FIPS_MODULE
    BN_CTX_free(new_ctx);
#endif
    return ret;

 err:
    if (used_ctx)
        BN_CTX_end(ctx);
#ifndef FIPS_MODULE
    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 ossl_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_MODULE
    BN_CTX *new_ctx = NULL;
#endif

    if (len == 0) {
        ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
        return 0;
    }

    /*
     * The first octet is the point conversion octet PC, see X9.62, page 4
     * and section 4.4.2.  It must be:
     *     0x00          for the point at infinity
     *     0x02 or 0x03  for compressed form
     *     0x04          for uncompressed form
     *     0x06 or 0x07  for hybrid form.
     * For compressed or hybrid forms, we store the last bit of buf[0] as
     * y_bit and clear it from buf[0] so as to obtain a POINT_CONVERSION_*.
     * We error if buf[0] contains any but the above values.
     */
    y_bit = buf[0] & 1;
    form = buf[0] & ~1U;

    if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
        && (form != POINT_CONVERSION_UNCOMPRESSED)
        && (form != POINT_CONVERSION_HYBRID)) {
        ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
        return 0;
    }
    if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
        ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
        return 0;
    }

    /* The point at infinity is represented by a single zero octet. */
    if (form == 0) {
        if (len != 1) {
            ERR_raise(ERR_LIB_EC, 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) {
        ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
        return 0;
    }

#ifndef FIPS_MODULE
    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) {
        ERR_raise(ERR_LIB_EC, 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) {
            ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
            goto err;
        }
        if (form == POINT_CONVERSION_HYBRID) {
            /*
             * Check that the form in the encoding was set correctly
             * according to X9.62 4.4.2.a, 4(c), see also first paragraph
             * of X9.62, 4.4.1.b.
             */
            if (BN_is_zero(x)) {
                if (y_bit != 0) {
                    ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
                    goto err;
                }
            } else {
                if (!group->meth->field_div(group, yxi, y, x, ctx))
                    goto err;
                if (y_bit != BN_is_odd(yxi)) {
                    ERR_raise(ERR_LIB_EC, 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_MODULE
    BN_CTX_free(new_ctx);
#endif
    return ret;
}
#endif
Commit	Line	Data
aa6bb135	1	/*
fecb3aae	2	* Copyright 2011-2022 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	*/
32ab57cb SL	39	int ossl_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)
0f113f3e	43	{
0f113f3e MC	44	BIGNUM tmp, x, y, z;
0f113f3e MC	45	int ret = 0, z0;
f844f9eb	46	#ifndef FIPS_MODULE
a9612d6c	47	BN_CTX *new_ctx = NULL;
0f113f3e	48
0f113f3e MC	49	if (ctx == NULL) {
	50	ctx = new_ctx = BN_CTX_new();
	51	if (ctx == NULL)
	52	return 0;
	53	}
a9612d6c	54	#endif
0f113f3e MC	55
	56	y_bit = (y_bit != 0) ? 1 : 0;
	57
	58	BN_CTX_start(ctx);
	59	tmp = BN_CTX_get(ctx);
	60	x = BN_CTX_get(ctx);
	61	y = BN_CTX_get(ctx);
	62	z = BN_CTX_get(ctx);
	63	if (z == NULL)
	64	goto err;
	65
	66	if (!BN_GF2m_mod_arr(x, x_, group->poly))
	67	goto err;
	68	if (BN_is_zero(x)) {
	69	if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx))
	70	goto err;
	71	} else {
	72	if (!group->meth->field_sqr(group, tmp, x, ctx))
	73	goto err;
	74	if (!group->meth->field_div(group, tmp, group->b, tmp, ctx))
	75	goto err;
	76	if (!BN_GF2m_add(tmp, group->a, tmp))
	77	goto err;
	78	if (!BN_GF2m_add(tmp, x, tmp))
	79	goto err;
afecd85d	80	ERR_set_mark();
0f113f3e	81	if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
f844f9eb	82	#ifndef FIPS_MODULE
0f113f3e MC	83	unsigned long err = ERR_peek_last_error();
	84
	85	if (ERR_GET_LIB(err) == ERR_LIB_BN
	86	&& ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
afecd85d	87	ERR_pop_to_mark();
9311d0c4	88	ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
0f113f3e	89	} else
a9612d6c MC	90	#endif
a9612d6c MC	91	{
afecd85d	92	ERR_clear_last_mark();
9311d0c4	93	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
a9612d6c	94	}
0f113f3e MC	95	goto err;
0f113f3e MC	96	}
afecd85d	97	ERR_clear_last_mark();
0f113f3e MC	98	z0 = (BN_is_odd(z)) ? 1 : 0;
	99	if (!group->meth->field_mul(group, y, x, z, ctx))
	100	goto err;
	101	if (z0 != y_bit) {
	102	if (!BN_GF2m_add(y, y, x))
	103	goto err;
	104	}
	105	}
	106
9cc570d4	107	if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
0f113f3e MC	108	goto err;
	109
	110	ret = 1;
84b08eee DSH	111
84b08eee DSH	112	err:
0f113f3e	113	BN_CTX_end(ctx);
f844f9eb	114	#ifndef FIPS_MODULE
23a1d5e9	115	BN_CTX_free(new_ctx);
a9612d6c	116	#endif
0f113f3e MC	117	return ret;
	118	}
	119
	120	/*
	121	* Converts an EC_POINT to an octet string. If buf is NULL, the encoded
	122	* length will be returned. If the length len of buf is smaller than required
	123	* an error will be returned.
84b08eee	124	*/
32ab57cb SL	125	size_t ossl_ec_GF2m_simple_point2oct(const EC_GROUP *group,
	126	const EC_POINT *point,
	127	point_conversion_form_t form,
	128	unsigned char buf, size_t len, BN_CTX ctx)
0f113f3e MC	129	{
0f113f3e MC	130	size_t ret;
0f113f3e MC	131	int used_ctx = 0;
	132	BIGNUM x, y, *yxi;
	133	size_t field_len, i, skip;
f844f9eb	134	#ifndef FIPS_MODULE
a9612d6c MC	135	BN_CTX *new_ctx = NULL;
a9612d6c MC	136	#endif
0f113f3e MC	137
	138	if ((form != POINT_CONVERSION_COMPRESSED)
	139	&& (form != POINT_CONVERSION_UNCOMPRESSED)
	140	&& (form != POINT_CONVERSION_HYBRID)) {
9311d0c4	141	ERR_raise(ERR_LIB_EC, EC_R_INVALID_FORM);
0f113f3e MC	142	goto err;
	143	}
	144
	145	if (EC_POINT_is_at_infinity(group, point)) {
	146	/* encodes to a single 0 octet */
	147	if (buf != NULL) {
	148	if (len < 1) {
9311d0c4	149	ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
0f113f3e MC	150	return 0;
	151	}
	152	buf[0] = 0;
	153	}
	154	return 1;
	155	}
	156
	157	/* ret := required output buffer length */
	158	field_len = (EC_GROUP_get_degree(group) + 7) / 8;
	159	ret =
	160	(form ==
	161	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
	162
	163	/* if 'buf' is NULL, just return required length */
	164	if (buf != NULL) {
	165	if (len < ret) {
9311d0c4	166	ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
0f113f3e MC	167	goto err;
	168	}
	169
f844f9eb	170	#ifndef FIPS_MODULE
0f113f3e MC	171	if (ctx == NULL) {
	172	ctx = new_ctx = BN_CTX_new();
	173	if (ctx == NULL)
	174	return 0;
	175	}
a9612d6c	176	#endif
0f113f3e MC	177
	178	BN_CTX_start(ctx);
	179	used_ctx = 1;
	180	x = BN_CTX_get(ctx);
	181	y = BN_CTX_get(ctx);
	182	yxi = BN_CTX_get(ctx);
	183	if (yxi == NULL)
	184	goto err;
	185
9cc570d4	186	if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
0f113f3e MC	187	goto err;
	188
	189	buf[0] = form;
	190	if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
	191	if (!group->meth->field_div(group, yxi, y, x, ctx))
	192	goto err;
	193	if (BN_is_odd(yxi))
	194	buf[0]++;
	195	}
	196
	197	i = 1;
	198
	199	skip = field_len - BN_num_bytes(x);
	200	if (skip > field_len) {
9311d0c4	201	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
0f113f3e MC	202	goto err;
	203	}
	204	while (skip > 0) {
	205	buf[i++] = 0;
	206	skip--;
	207	}
	208	skip = BN_bn2bin(x, buf + i);
	209	i += skip;
	210	if (i != 1 + field_len) {
9311d0c4	211	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
0f113f3e MC	212	goto err;
	213	}
	214
	215	if (form == POINT_CONVERSION_UNCOMPRESSED
	216	\|\| form == POINT_CONVERSION_HYBRID) {
	217	skip = field_len - BN_num_bytes(y);
	218	if (skip > field_len) {
9311d0c4	219	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
0f113f3e MC	220	goto err;
	221	}
	222	while (skip > 0) {
	223	buf[i++] = 0;
	224	skip--;
	225	}
	226	skip = BN_bn2bin(y, buf + i);
	227	i += skip;
	228	}
	229
	230	if (i != ret) {
9311d0c4	231	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
0f113f3e MC	232	goto err;
	233	}
	234	}
	235
	236	if (used_ctx)
	237	BN_CTX_end(ctx);
f844f9eb	238	#ifndef FIPS_MODULE
23a1d5e9	239	BN_CTX_free(new_ctx);
a9612d6c	240	#endif
0f113f3e	241	return ret;
84b08eee DSH	242
84b08eee DSH	243	err:
0f113f3e MC	244	if (used_ctx)
0f113f3e MC	245	BN_CTX_end(ctx);
f844f9eb	246	#ifndef FIPS_MODULE
23a1d5e9	247	BN_CTX_free(new_ctx);
a9612d6c	248	#endif
0f113f3e MC	249	return 0;
	250	}
	251
	252	/*
	253	* Converts an octet string representation to an EC_POINT. Note that the
	254	* simple implementation only uses affine coordinates.
84b08eee	255	*/
32ab57cb SL	256	int ossl_ec_GF2m_simple_oct2point(const EC_GROUP group, EC_POINT point,
	257	const unsigned char *buf, size_t len,
	258	BN_CTX *ctx)
0f113f3e MC	259	{
0f113f3e MC	260	point_conversion_form_t form;
cad8347b	261	int y_bit, m;
0f113f3e MC	262	BIGNUM x, y, *yxi;
	263	size_t field_len, enc_len;
	264	int ret = 0;
f844f9eb	265	#ifndef FIPS_MODULE
a9612d6c MC	266	BN_CTX *new_ctx = NULL;
a9612d6c MC	267	#endif
0f113f3e MC	268
0f113f3e MC	269	if (len == 0) {
9311d0c4	270	ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
0f113f3e MC	271	return 0;
0f113f3e MC	272	}
56f02379 TB	273
56f02379 TB	274	/*
e304aa87	275	* The first octet is the point conversion octet PC, see X9.62, page 4
56f02379 TB	276	* and section 4.4.2. It must be:
	277	* 0x00 for the point at infinity
	278	* 0x02 or 0x03 for compressed form
	279	* 0x04 for uncompressed form
	280	* 0x06 or 0x07 for hybrid form.
	281	* For compressed or hybrid forms, we store the last bit of buf[0] as
	282	* y_bit and clear it from buf[0] so as to obtain a POINT_CONVERSION_*.
	283	* We error if buf[0] contains any but the above values.
	284	*/
	285	y_bit = buf[0] & 1;
	286	form = buf[0] & ~1U;
	287
0f113f3e MC	288	if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
	289	&& (form != POINT_CONVERSION_UNCOMPRESSED)
	290	&& (form != POINT_CONVERSION_HYBRID)) {
9311d0c4	291	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
0f113f3e MC	292	return 0;
	293	}
	294	if ((form == 0 \|\| form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
9311d0c4	295	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
0f113f3e MC	296	return 0;
	297	}
	298
56f02379	299	/* The point at infinity is represented by a single zero octet. */
0f113f3e MC	300	if (form == 0) {
0f113f3e MC	301	if (len != 1) {
9311d0c4	302	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
0f113f3e MC	303	return 0;
	304	}
	305
	306	return EC_POINT_set_to_infinity(group, point);
	307	}
	308
cad8347b SL	309	m = EC_GROUP_get_degree(group);
cad8347b SL	310	field_len = (m + 7) / 8;
0f113f3e MC	311	enc_len =
	312	(form ==
	313	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
	314
	315	if (len != enc_len) {
9311d0c4	316	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
0f113f3e MC	317	return 0;
	318	}
	319
f844f9eb	320	#ifndef FIPS_MODULE
0f113f3e MC	321	if (ctx == NULL) {
	322	ctx = new_ctx = BN_CTX_new();
	323	if (ctx == NULL)
	324	return 0;
	325	}
a9612d6c	326	#endif
0f113f3e MC	327
	328	BN_CTX_start(ctx);
	329	x = BN_CTX_get(ctx);
	330	y = BN_CTX_get(ctx);
	331	yxi = BN_CTX_get(ctx);
	332	if (yxi == NULL)
	333	goto err;
	334
	335	if (!BN_bin2bn(buf + 1, field_len, x))
	336	goto err;
cad8347b	337	if (BN_num_bits(x) > m) {
9311d0c4	338	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
0f113f3e MC	339	goto err;
	340	}
	341
	342	if (form == POINT_CONVERSION_COMPRESSED) {
9cc570d4	343	if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
0f113f3e MC	344	goto err;
	345	} else {
	346	if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
	347	goto err;
cad8347b	348	if (BN_num_bits(y) > m) {
9311d0c4	349	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
0f113f3e MC	350	goto err;
	351	}
	352	if (form == POINT_CONVERSION_HYBRID) {
56f02379 TB	353	/*
	354	* Check that the form in the encoding was set correctly
	355	* according to X9.62 4.4.2.a, 4(c), see also first paragraph
	356	* of X9.62, 4.4.1.b.
	357	*/
	358	if (BN_is_zero(x)) {
	359	if (y_bit != 0) {
	360	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
	361	goto err;
	362	}
	363	} else {
	364	if (!group->meth->field_div(group, yxi, y, x, ctx))
	365	goto err;
	366	if (y_bit != BN_is_odd(yxi)) {
	367	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
	368	goto err;
	369	}
0f113f3e MC	370	}
	371	}
	372
1e2012b7	373	/*
9cc570d4	374	* EC_POINT_set_affine_coordinates is responsible for checking that
1e2012b7 EK	375	* the point is on the curve.
1e2012b7 EK	376	*/
9cc570d4	377	if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
0f113f3e MC	378	goto err;
	379	}
	380
0f113f3e MC	381	ret = 1;
0f113f3e MC	382
84b08eee	383	err:
0f113f3e	384	BN_CTX_end(ctx);
f844f9eb	385	#ifndef FIPS_MODULE
23a1d5e9	386	BN_CTX_free(new_ctx);
a9612d6c	387	#endif
0f113f3e MC	388	return ret;
0f113f3e MC	389	}
84b08eee	390	#endif