Line data Source code
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 : /* ====================================================================
17 : * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
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
24 : * notice, this list of conditions and the following disclaimer.
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 :
76 : /*-
77 : * Calculates and sets the affine coordinates of an EC_POINT from the given
78 : * compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
79 : * Note that the simple implementation only uses affine coordinates.
80 : *
81 : * The method is from the following publication:
82 : *
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 : */
92 0 : 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 0 : ERR_clear_error();
103 :
104 0 : if (ctx == NULL) {
105 0 : ctx = new_ctx = BN_CTX_new();
106 0 : if (ctx == NULL)
107 : return 0;
108 : }
109 :
110 0 : y_bit = (y_bit != 0) ? 1 : 0;
111 :
112 0 : BN_CTX_start(ctx);
113 0 : tmp = BN_CTX_get(ctx);
114 0 : x = BN_CTX_get(ctx);
115 0 : y = BN_CTX_get(ctx);
116 0 : z = BN_CTX_get(ctx);
117 0 : if (z == NULL)
118 : goto err;
119 :
120 0 : if (!BN_GF2m_mod_arr(x, x_, group->poly))
121 : goto err;
122 0 : if (BN_is_zero(x)) {
123 0 : if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx))
124 : goto err;
125 : } else {
126 0 : if (!group->meth->field_sqr(group, tmp, x, ctx))
127 : goto err;
128 0 : if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx))
129 : goto err;
130 0 : if (!BN_GF2m_add(tmp, &group->a, tmp))
131 : goto err;
132 0 : if (!BN_GF2m_add(tmp, x, tmp))
133 : goto err;
134 0 : if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
135 0 : unsigned long err = ERR_peek_last_error();
136 :
137 0 : if (ERR_GET_LIB(err) == ERR_LIB_BN
138 0 : && ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
139 0 : ERR_clear_error();
140 0 : ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
141 : EC_R_INVALID_COMPRESSED_POINT);
142 : } else
143 0 : ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
144 : ERR_R_BN_LIB);
145 : goto err;
146 : }
147 0 : z0 = (BN_is_odd(z)) ? 1 : 0;
148 0 : if (!group->meth->field_mul(group, y, x, z, ctx))
149 : goto err;
150 0 : if (z0 != y_bit) {
151 0 : if (!BN_GF2m_add(y, y, x))
152 : goto err;
153 : }
154 : }
155 :
156 0 : if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
157 : goto err;
158 :
159 : ret = 1;
160 :
161 : err:
162 0 : BN_CTX_end(ctx);
163 0 : if (new_ctx != NULL)
164 0 : BN_CTX_free(new_ctx);
165 0 : 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.
172 : */
173 0 : 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 0 : if ((form != POINT_CONVERSION_COMPRESSED)
184 0 : && (form != POINT_CONVERSION_UNCOMPRESSED)
185 0 : && (form != POINT_CONVERSION_HYBRID)) {
186 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
187 0 : goto err;
188 : }
189 :
190 0 : if (EC_POINT_is_at_infinity(group, point)) {
191 : /* encodes to a single 0 octet */
192 0 : if (buf != NULL) {
193 0 : if (len < 1) {
194 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
195 0 : return 0;
196 : }
197 0 : buf[0] = 0;
198 : }
199 : return 1;
200 : }
201 :
202 : /* ret := required output buffer length */
203 0 : field_len = (EC_GROUP_get_degree(group) + 7) / 8;
204 : ret =
205 : (form ==
206 0 : POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
207 :
208 : /* if 'buf' is NULL, just return required length */
209 0 : if (buf != NULL) {
210 0 : if (len < ret) {
211 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
212 0 : goto err;
213 : }
214 :
215 0 : if (ctx == NULL) {
216 0 : ctx = new_ctx = BN_CTX_new();
217 0 : if (ctx == NULL)
218 : return 0;
219 : }
220 :
221 0 : BN_CTX_start(ctx);
222 : used_ctx = 1;
223 0 : x = BN_CTX_get(ctx);
224 0 : y = BN_CTX_get(ctx);
225 0 : yxi = BN_CTX_get(ctx);
226 0 : if (yxi == NULL)
227 : goto err;
228 :
229 0 : if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))
230 : goto err;
231 :
232 0 : buf[0] = form;
233 0 : if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
234 0 : if (!group->meth->field_div(group, yxi, y, x, ctx))
235 : goto err;
236 0 : if (BN_is_odd(yxi))
237 0 : buf[0]++;
238 : }
239 :
240 : i = 1;
241 :
242 0 : skip = field_len - BN_num_bytes(x);
243 0 : if (skip > field_len) {
244 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
245 0 : goto err;
246 : }
247 0 : while (skip > 0) {
248 0 : buf[i++] = 0;
249 0 : skip--;
250 : }
251 0 : skip = BN_bn2bin(x, buf + i);
252 0 : i += skip;
253 0 : if (i != 1 + field_len) {
254 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
255 0 : goto err;
256 : }
257 :
258 0 : if (form == POINT_CONVERSION_UNCOMPRESSED
259 0 : || form == POINT_CONVERSION_HYBRID) {
260 0 : skip = field_len - BN_num_bytes(y);
261 0 : if (skip > field_len) {
262 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
263 0 : goto err;
264 : }
265 0 : while (skip > 0) {
266 0 : buf[i++] = 0;
267 0 : skip--;
268 : }
269 0 : skip = BN_bn2bin(y, buf + i);
270 0 : i += skip;
271 : }
272 :
273 0 : if (i != ret) {
274 0 : ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
275 0 : goto err;
276 : }
277 : }
278 :
279 0 : if (used_ctx)
280 0 : BN_CTX_end(ctx);
281 0 : if (new_ctx != NULL)
282 0 : BN_CTX_free(new_ctx);
283 0 : return ret;
284 :
285 : err:
286 0 : if (used_ctx)
287 0 : BN_CTX_end(ctx);
288 0 : if (new_ctx != NULL)
289 0 : 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.
296 : */
297 0 : int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
298 : const unsigned char *buf, size_t len,
299 : BN_CTX *ctx)
300 : {
301 : point_conversion_form_t form;
302 : int y_bit;
303 : BN_CTX *new_ctx = NULL;
304 : BIGNUM *x, *y, *yxi;
305 : size_t field_len, enc_len;
306 : int ret = 0;
307 :
308 0 : if (len == 0) {
309 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
310 0 : return 0;
311 : }
312 0 : form = buf[0];
313 0 : y_bit = form & 1;
314 0 : form = form & ~1U;
315 0 : if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
316 0 : && (form != POINT_CONVERSION_UNCOMPRESSED)
317 0 : && (form != POINT_CONVERSION_HYBRID)) {
318 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
319 0 : return 0;
320 : }
321 0 : if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
322 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
323 0 : return 0;
324 : }
325 :
326 0 : if (form == 0) {
327 0 : if (len != 1) {
328 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
329 0 : return 0;
330 : }
331 :
332 0 : return EC_POINT_set_to_infinity(group, point);
333 : }
334 :
335 0 : field_len = (EC_GROUP_get_degree(group) + 7) / 8;
336 : enc_len =
337 : (form ==
338 0 : POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
339 :
340 0 : if (len != enc_len) {
341 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
342 0 : return 0;
343 : }
344 :
345 0 : if (ctx == NULL) {
346 0 : ctx = new_ctx = BN_CTX_new();
347 0 : if (ctx == NULL)
348 : return 0;
349 : }
350 :
351 0 : BN_CTX_start(ctx);
352 0 : x = BN_CTX_get(ctx);
353 0 : y = BN_CTX_get(ctx);
354 0 : yxi = BN_CTX_get(ctx);
355 0 : if (yxi == NULL)
356 : goto err;
357 :
358 0 : if (!BN_bin2bn(buf + 1, field_len, x))
359 : goto err;
360 0 : if (BN_ucmp(x, &group->field) >= 0) {
361 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
362 0 : goto err;
363 : }
364 :
365 0 : if (form == POINT_CONVERSION_COMPRESSED) {
366 0 : if (!EC_POINT_set_compressed_coordinates_GF2m
367 0 : (group, point, x, y_bit, ctx))
368 : goto err;
369 : } else {
370 0 : if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
371 : goto err;
372 0 : if (BN_ucmp(y, &group->field) >= 0) {
373 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
374 0 : goto err;
375 : }
376 0 : if (form == POINT_CONVERSION_HYBRID) {
377 0 : if (!group->meth->field_div(group, yxi, y, x, ctx))
378 : goto err;
379 0 : if (y_bit != BN_is_odd(yxi)) {
380 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
381 0 : goto err;
382 : }
383 : }
384 :
385 0 : if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
386 : goto err;
387 : }
388 :
389 : /* test required by X9.62 */
390 0 : if (EC_POINT_is_on_curve(group, point, ctx) <= 0) {
391 0 : ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
392 0 : goto err;
393 : }
394 :
395 : ret = 1;
396 :
397 : err:
398 0 : BN_CTX_end(ctx);
399 0 : if (new_ctx != NULL)
400 0 : BN_CTX_free(new_ctx);
401 0 : return ret;
402 : }
403 : #endif
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