/src/openssl/crypto/ec/ec2_oct.c

Source
/*
 * Copyright 2011-2025 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;
    int 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 != (size_t)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

Coverage Report

Created: 2025-10-28 06:56

Line	Count	Source
1		/*
2		* Copyright 2011-2025 The OpenSSL Project Authors. All Rights Reserved.
3		* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
4		*
5		* Licensed under the Apache License 2.0 (the "License"). You may not use
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
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
17		#include <openssl/err.h>
18
19		#include "ec_local.h"
20
21		#ifndef OPENSSL_NO_EC2M
22
23		/*-
24		* Calculates and sets the affine coordinates of an EC_POINT from the given
25		* compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
26		* Note that the simple implementation only uses affine coordinates.
27		*
28		* The method is from the following publication:
29		*
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		*/
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)
43	0	{
44	0	BIGNUM tmp, x, y, z;
45	0	int ret = 0, z0;
46	0	#ifndef FIPS_MODULE
47	0	BN_CTX *new_ctx = NULL;
48
49	0	if (ctx == NULL) {
50	0	ctx = new_ctx = BN_CTX_new();
51	0	if (ctx == NULL)
52	0	return 0;
53	0	}
54	0	#endif
55
56	0	y_bit = (y_bit != 0) ? 1 : 0;
57
58	0	BN_CTX_start(ctx);
59	0	tmp = BN_CTX_get(ctx);
60	0	x = BN_CTX_get(ctx);
61	0	y = BN_CTX_get(ctx);
62	0	z = BN_CTX_get(ctx);
63	0	if (z == NULL)
64	0	goto err;
65
66	0	if (!BN_GF2m_mod_arr(x, x_, group->poly))
67	0	goto err;
68	0	if (BN_is_zero(x)) {
69	0	if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx))
70	0	goto err;
71	0	} else {
72	0	if (!group->meth->field_sqr(group, tmp, x, ctx))
73	0	goto err;
74	0	if (!group->meth->field_div(group, tmp, group->b, tmp, ctx))
75	0	goto err;
76	0	if (!BN_GF2m_add(tmp, group->a, tmp))
77	0	goto err;
78	0	if (!BN_GF2m_add(tmp, x, tmp))
79	0	goto err;
80	0	ERR_set_mark();
81	0	if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
82	0	#ifndef FIPS_MODULE
83	0	unsigned long err = ERR_peek_last_error();
84
85	0	if (ERR_GET_LIB(err) == ERR_LIB_BN
86	0	&& ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
87	0	ERR_pop_to_mark();
88	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
89	0	} else
90	0	#endif
91	0	{
92	0	ERR_clear_last_mark();
93	0	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
94	0	}
95	0	goto err;
96	0	}
97	0	ERR_clear_last_mark();
98	0	z0 = (BN_is_odd(z)) ? 1 : 0;
99	0	if (!group->meth->field_mul(group, y, x, z, ctx))
100	0	goto err;
101	0	if (z0 != y_bit) {
102	0	if (!BN_GF2m_add(y, y, x))
103	0	goto err;
104	0	}
105	0	}
106
107	0	if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
108	0	goto err;
109
110	0	ret = 1;
111
112	0	err:
113	0	BN_CTX_end(ctx);
114	0	#ifndef FIPS_MODULE
115	0	BN_CTX_free(new_ctx);
116	0	#endif
117	0	return ret;
118	0	}
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.
124		*/
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)
129	0	{
130	0	size_t ret;
131	0	int used_ctx = 0;
132	0	BIGNUM x, y, *yxi;
133	0	size_t field_len, i, skip;
134	0	#ifndef FIPS_MODULE
135	0	BN_CTX *new_ctx = NULL;
136	0	#endif
137
138	0	if ((form != POINT_CONVERSION_COMPRESSED)
139	0	&& (form != POINT_CONVERSION_UNCOMPRESSED)
140	0	&& (form != POINT_CONVERSION_HYBRID)) {
141	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_FORM);
142	0	goto err;
143	0	}
144
145	0	if (EC_POINT_is_at_infinity(group, point)) {
146		/* encodes to a single 0 octet */
147	0	if (buf != NULL) {
148	0	if (len < 1) {
149	0	ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
150	0	return 0;
151	0	}
152	0	buf[0] = 0;
153	0	}
154	0	return 1;
155	0	}
156
157		/* ret := required output buffer length */
158	0	field_len = (EC_GROUP_get_degree(group) + 7) / 8;
159	0	ret =
160	0	(form ==
161	0	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
162
163		/* if 'buf' is NULL, just return required length */
164	0	if (buf != NULL) {
165	0	if (len < ret) {
166	0	ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
167	0	goto err;
168	0	}
169
170	0	#ifndef FIPS_MODULE
171	0	if (ctx == NULL) {
172	0	ctx = new_ctx = BN_CTX_new();
173	0	if (ctx == NULL)
174	0	return 0;
175	0	}
176	0	#endif
177
178	0	BN_CTX_start(ctx);
179	0	used_ctx = 1;
180	0	x = BN_CTX_get(ctx);
181	0	y = BN_CTX_get(ctx);
182	0	yxi = BN_CTX_get(ctx);
183	0	if (yxi == NULL)
184	0	goto err;
185
186	0	if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
187	0	goto err;
188
189	0	buf[0] = form;
190	0	if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
191	0	if (!group->meth->field_div(group, yxi, y, x, ctx))
192	0	goto err;
193	0	if (BN_is_odd(yxi))
194	0	buf[0]++;
195	0	}
196
197	0	i = 1;
198
199	0	skip = field_len - BN_num_bytes(x);
200	0	if (skip > field_len) {
201	0	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
202	0	goto err;
203	0	}
204	0	while (skip > 0) {
205	0	buf[i++] = 0;
206	0	skip--;
207	0	}
208	0	skip = BN_bn2bin(x, buf + i);
209	0	i += skip;
210	0	if (i != 1 + field_len) {
211	0	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
212	0	goto err;
213	0	}
214
215	0	if (form == POINT_CONVERSION_UNCOMPRESSED
216	0	\|\| form == POINT_CONVERSION_HYBRID) {
217	0	skip = field_len - BN_num_bytes(y);
218	0	if (skip > field_len) {
219	0	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
220	0	goto err;
221	0	}
222	0	while (skip > 0) {
223	0	buf[i++] = 0;
224	0	skip--;
225	0	}
226	0	skip = BN_bn2bin(y, buf + i);
227	0	i += skip;
228	0	}
229
230	0	if (i != ret) {
231	0	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
232	0	goto err;
233	0	}
234	0	}
235
236	0	if (used_ctx)
237	0	BN_CTX_end(ctx);
238	0	#ifndef FIPS_MODULE
239	0	BN_CTX_free(new_ctx);
240	0	#endif
241	0	return ret;
242
243	0	err:
244	0	if (used_ctx)
245	0	BN_CTX_end(ctx);
246	0	#ifndef FIPS_MODULE
247	0	BN_CTX_free(new_ctx);
248	0	#endif
249	0	return 0;
250	0	}
251
252		/*
253		* Converts an octet string representation to an EC_POINT. Note that the
254		* simple implementation only uses affine coordinates.
255		*/
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)
259	0	{
260	0	point_conversion_form_t form;
261	0	int y_bit, m;
262	0	BIGNUM x, y, *yxi;
263	0	int field_len, enc_len;
264	0	int ret = 0;
265	0	#ifndef FIPS_MODULE
266	0	BN_CTX *new_ctx = NULL;
267	0	#endif
268
269	0	if (len == 0) {
270	0	ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
271	0	return 0;
272	0	}
273
274		/*
275		* The first octet is the point conversion octet PC, see X9.62, page 4
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	0	y_bit = buf[0] & 1;
286	0	form = buf[0] & ~1U;
287
288	0	if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
289	0	&& (form != POINT_CONVERSION_UNCOMPRESSED)
290	0	&& (form != POINT_CONVERSION_HYBRID)) {
291	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
292	0	return 0;
293	0	}
294	0	if ((form == 0 \|\| form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
295	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
296	0	return 0;
297	0	}
298
299		/* The point at infinity is represented by a single zero octet. */
300	0	if (form == 0) {
301	0	if (len != 1) {
302	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
303	0	return 0;
304	0	}
305
306	0	return EC_POINT_set_to_infinity(group, point);
307	0	}
308
309	0	m = EC_GROUP_get_degree(group);
310	0	field_len = (m + 7) / 8;
311	0	enc_len =
312	0	(form ==
313	0	POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
314
315	0	if (len != (size_t)enc_len) {
316	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
317	0	return 0;
318	0	}
319
320	0	#ifndef FIPS_MODULE
321	0	if (ctx == NULL) {
322	0	ctx = new_ctx = BN_CTX_new();
323	0	if (ctx == NULL)
324	0	return 0;
325	0	}
326	0	#endif
327
328	0	BN_CTX_start(ctx);
329	0	x = BN_CTX_get(ctx);
330	0	y = BN_CTX_get(ctx);
331	0	yxi = BN_CTX_get(ctx);
332	0	if (yxi == NULL)
333	0	goto err;
334
335	0	if (!BN_bin2bn(buf + 1, field_len, x))
336	0	goto err;
337	0	if (BN_num_bits(x) > m) {
338	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
339	0	goto err;
340	0	}
341
342	0	if (form == POINT_CONVERSION_COMPRESSED) {
343	0	if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
344	0	goto err;
345	0	} else {
346	0	if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
347	0	goto err;
348	0	if (BN_num_bits(y) > m) {
349	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
350	0	goto err;
351	0	}
352	0	if (form == POINT_CONVERSION_HYBRID) {
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	0	if (BN_is_zero(x)) {
359	0	if (y_bit != 0) {
360	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
361	0	goto err;
362	0	}
363	0	} else {
364	0	if (!group->meth->field_div(group, yxi, y, x, ctx))
365	0	goto err;
366	0	if (y_bit != BN_is_odd(yxi)) {
367	0	ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
368	0	goto err;
369	0	}
370	0	}
371	0	}
372
373		/*
374		* EC_POINT_set_affine_coordinates is responsible for checking that
375		* the point is on the curve.
376		*/
377	0	if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
378	0	goto err;
379	0	}
380
381	0	ret = 1;
382
383	0	err:
384	0	BN_CTX_end(ctx);
385	0	#ifndef FIPS_MODULE
386	0	BN_CTX_free(new_ctx);
387	0	#endif
388	0	return ret;
389	0	}
390		#endif