1 /* $OpenBSD: ecp_oct.c,v 1.14 2021/04/20 17:32:57 tb Exp $ */
2 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
3 * for the OpenSSL project.
4 * Includes code written by Bodo Moeller for the OpenSSL project.
5 */
6 /* ====================================================================
7 * Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 *
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in
18 * the documentation and/or other materials provided with the
19 * distribution.
20 *
21 * 3. All advertising materials mentioning features or use of this
22 * software must display the following acknowledgment:
23 * "This product includes software developed by the OpenSSL Project
24 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
25 *
26 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
27 * endorse or promote products derived from this software without
28 * prior written permission. For written permission, please contact
29 * openssl-core@openssl.org.
30 *
31 * 5. Products derived from this software may not be called "OpenSSL"
32 * nor may "OpenSSL" appear in their names without prior written
33 * permission of the OpenSSL Project.
34 *
35 * 6. Redistributions of any form whatsoever must retain the following
36 * acknowledgment:
37 * "This product includes software developed by the OpenSSL Project
38 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
41 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
43 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
44 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
45 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
46 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
47 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
49 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
50 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
51 * OF THE POSSIBILITY OF SUCH DAMAGE.
52 * ====================================================================
53 *
54 * This product includes cryptographic software written by Eric Young
55 * (eay@cryptsoft.com). This product includes software written by Tim
56 * Hudson (tjh@cryptsoft.com).
57 *
58 */
59 /* ====================================================================
60 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
61 * Portions of this software developed by SUN MICROSYSTEMS, INC.,
62 * and contributed to the OpenSSL project.
63 */
64
65 #include <openssl/err.h>
66
67 #include "ec_lcl.h"
68
69 int
ec_GFp_simple_set_compressed_coordinates(const EC_GROUP * group,EC_POINT * point,const BIGNUM * x_,int y_bit,BN_CTX * ctx)70 ec_GFp_simple_set_compressed_coordinates(const EC_GROUP * group,
71 EC_POINT * point, const BIGNUM * x_, int y_bit, BN_CTX * ctx)
72 {
73 BN_CTX *new_ctx = NULL;
74 BIGNUM *tmp1, *tmp2, *x, *y;
75 int ret = 0;
76
77 /* clear error queue */
78 ERR_clear_error();
79
80 if (ctx == NULL) {
81 ctx = new_ctx = BN_CTX_new();
82 if (ctx == NULL)
83 return 0;
84 }
85 y_bit = (y_bit != 0);
86
87 BN_CTX_start(ctx);
88 if ((tmp1 = BN_CTX_get(ctx)) == NULL)
89 goto err;
90 if ((tmp2 = BN_CTX_get(ctx)) == NULL)
91 goto err;
92 if ((x = BN_CTX_get(ctx)) == NULL)
93 goto err;
94 if ((y = BN_CTX_get(ctx)) == NULL)
95 goto err;
96
97 /*
98 * Recover y. We have a Weierstrass equation y^2 = x^3 + a*x + b, so
99 * y is one of the square roots of x^3 + a*x + b.
100 */
101
102 /* tmp1 := x^3 */
103 if (!BN_nnmod(x, x_, &group->field, ctx))
104 goto err;
105 if (group->meth->field_decode == 0) {
106 /* field_{sqr,mul} work on standard representation */
107 if (!group->meth->field_sqr(group, tmp2, x_, ctx))
108 goto err;
109 if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx))
110 goto err;
111 } else {
112 if (!BN_mod_sqr(tmp2, x_, &group->field, ctx))
113 goto err;
114 if (!BN_mod_mul(tmp1, tmp2, x_, &group->field, ctx))
115 goto err;
116 }
117
118 /* tmp1 := tmp1 + a*x */
119 if (group->a_is_minus3) {
120 if (!BN_mod_lshift1_quick(tmp2, x, &group->field))
121 goto err;
122 if (!BN_mod_add_quick(tmp2, tmp2, x, &group->field))
123 goto err;
124 if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field))
125 goto err;
126 } else {
127 if (group->meth->field_decode) {
128 if (!group->meth->field_decode(group, tmp2, &group->a, ctx))
129 goto err;
130 if (!BN_mod_mul(tmp2, tmp2, x, &group->field, ctx))
131 goto err;
132 } else {
133 /* field_mul works on standard representation */
134 if (!group->meth->field_mul(group, tmp2, &group->a, x, ctx))
135 goto err;
136 }
137
138 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field))
139 goto err;
140 }
141
142 /* tmp1 := tmp1 + b */
143 if (group->meth->field_decode) {
144 if (!group->meth->field_decode(group, tmp2, &group->b, ctx))
145 goto err;
146 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field))
147 goto err;
148 } else {
149 if (!BN_mod_add_quick(tmp1, tmp1, &group->b, &group->field))
150 goto err;
151 }
152
153 if (!BN_mod_sqrt(y, tmp1, &group->field, ctx)) {
154 unsigned long err = ERR_peek_last_error();
155
156 if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
157 ERR_clear_error();
158 ECerror(EC_R_INVALID_COMPRESSED_POINT);
159 } else
160 ECerror(ERR_R_BN_LIB);
161 goto err;
162 }
163 if (y_bit != BN_is_odd(y)) {
164 if (BN_is_zero(y)) {
165 int kron;
166
167 kron = BN_kronecker(x, &group->field, ctx);
168 if (kron == -2)
169 goto err;
170
171 if (kron == 1)
172 ECerror(EC_R_INVALID_COMPRESSION_BIT);
173 else
174 /*
175 * BN_mod_sqrt() should have cought this
176 * error (not a square)
177 */
178 ECerror(EC_R_INVALID_COMPRESSED_POINT);
179 goto err;
180 }
181 if (!BN_usub(y, &group->field, y))
182 goto err;
183 }
184 if (y_bit != BN_is_odd(y)) {
185 ECerror(ERR_R_INTERNAL_ERROR);
186 goto err;
187 }
188 if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
189 goto err;
190
191 ret = 1;
192
193 err:
194 BN_CTX_end(ctx);
195 BN_CTX_free(new_ctx);
196 return ret;
197 }
198
199
200 size_t
ec_GFp_simple_point2oct(const EC_GROUP * group,const EC_POINT * point,point_conversion_form_t form,unsigned char * buf,size_t len,BN_CTX * ctx)201 ec_GFp_simple_point2oct(const EC_GROUP * group, const EC_POINT * point, point_conversion_form_t form,
202 unsigned char *buf, size_t len, BN_CTX * ctx)
203 {
204 size_t ret;
205 BN_CTX *new_ctx = NULL;
206 int used_ctx = 0;
207 BIGNUM *x, *y;
208 size_t field_len, i, skip;
209
210 if ((form != POINT_CONVERSION_COMPRESSED)
211 && (form != POINT_CONVERSION_UNCOMPRESSED)
212 && (form != POINT_CONVERSION_HYBRID)) {
213 ECerror(EC_R_INVALID_FORM);
214 goto err;
215 }
216 if (EC_POINT_is_at_infinity(group, point) > 0) {
217 /* encodes to a single 0 octet */
218 if (buf != NULL) {
219 if (len < 1) {
220 ECerror(EC_R_BUFFER_TOO_SMALL);
221 return 0;
222 }
223 buf[0] = 0;
224 }
225 return 1;
226 }
227 /* ret := required output buffer length */
228 field_len = BN_num_bytes(&group->field);
229 ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
230
231 /* if 'buf' is NULL, just return required length */
232 if (buf != NULL) {
233 if (len < ret) {
234 ECerror(EC_R_BUFFER_TOO_SMALL);
235 goto err;
236 }
237 if (ctx == NULL) {
238 ctx = new_ctx = BN_CTX_new();
239 if (ctx == NULL)
240 return 0;
241 }
242 BN_CTX_start(ctx);
243 used_ctx = 1;
244 if ((x = BN_CTX_get(ctx)) == NULL)
245 goto err;
246 if ((y = BN_CTX_get(ctx)) == NULL)
247 goto err;
248
249 if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
250 goto err;
251
252 if ((form == POINT_CONVERSION_COMPRESSED || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y))
253 buf[0] = form + 1;
254 else
255 buf[0] = form;
256
257 i = 1;
258
259 skip = field_len - BN_num_bytes(x);
260 if (skip > field_len) {
261 ECerror(ERR_R_INTERNAL_ERROR);
262 goto err;
263 }
264 while (skip > 0) {
265 buf[i++] = 0;
266 skip--;
267 }
268 skip = BN_bn2bin(x, buf + i);
269 i += skip;
270 if (i != 1 + field_len) {
271 ECerror(ERR_R_INTERNAL_ERROR);
272 goto err;
273 }
274 if (form == POINT_CONVERSION_UNCOMPRESSED || form == POINT_CONVERSION_HYBRID) {
275 skip = field_len - BN_num_bytes(y);
276 if (skip > field_len) {
277 ECerror(ERR_R_INTERNAL_ERROR);
278 goto err;
279 }
280 while (skip > 0) {
281 buf[i++] = 0;
282 skip--;
283 }
284 skip = BN_bn2bin(y, buf + i);
285 i += skip;
286 }
287 if (i != ret) {
288 ECerror(ERR_R_INTERNAL_ERROR);
289 goto err;
290 }
291 }
292 if (used_ctx)
293 BN_CTX_end(ctx);
294 BN_CTX_free(new_ctx);
295 return ret;
296
297 err:
298 if (used_ctx)
299 BN_CTX_end(ctx);
300 BN_CTX_free(new_ctx);
301 return 0;
302 }
303
304
305 int
ec_GFp_simple_oct2point(const EC_GROUP * group,EC_POINT * point,const unsigned char * buf,size_t len,BN_CTX * ctx)306 ec_GFp_simple_oct2point(const EC_GROUP * group, EC_POINT * point,
307 const unsigned char *buf, size_t len, BN_CTX * ctx)
308 {
309 point_conversion_form_t form;
310 int y_bit;
311 BN_CTX *new_ctx = NULL;
312 BIGNUM *x, *y;
313 size_t field_len, enc_len;
314 int ret = 0;
315
316 if (len == 0) {
317 ECerror(EC_R_BUFFER_TOO_SMALL);
318 return 0;
319 }
320 form = buf[0];
321 y_bit = form & 1;
322 form = form & ~1U;
323 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
324 && (form != POINT_CONVERSION_UNCOMPRESSED)
325 && (form != POINT_CONVERSION_HYBRID)) {
326 ECerror(EC_R_INVALID_ENCODING);
327 return 0;
328 }
329 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
330 ECerror(EC_R_INVALID_ENCODING);
331 return 0;
332 }
333 if (form == 0) {
334 if (len != 1) {
335 ECerror(EC_R_INVALID_ENCODING);
336 return 0;
337 }
338 return EC_POINT_set_to_infinity(group, point);
339 }
340 field_len = BN_num_bytes(&group->field);
341 enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
342
343 if (len != enc_len) {
344 ECerror(EC_R_INVALID_ENCODING);
345 return 0;
346 }
347 if (ctx == NULL) {
348 ctx = new_ctx = BN_CTX_new();
349 if (ctx == NULL)
350 return 0;
351 }
352 BN_CTX_start(ctx);
353 if ((x = BN_CTX_get(ctx)) == NULL)
354 goto err;
355 if ((y = BN_CTX_get(ctx)) == NULL)
356 goto err;
357
358 if (!BN_bin2bn(buf + 1, field_len, x))
359 goto err;
360 if (BN_ucmp(x, &group->field) >= 0) {
361 ECerror(EC_R_INVALID_ENCODING);
362 goto err;
363 }
364 if (form == POINT_CONVERSION_COMPRESSED) {
365 /*
366 * EC_POINT_set_compressed_coordinates checks that the point
367 * is on the curve as required by X9.62.
368 */
369 if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
370 goto err;
371 } else {
372 if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
373 goto err;
374 if (BN_ucmp(y, &group->field) >= 0) {
375 ECerror(EC_R_INVALID_ENCODING);
376 goto err;
377 }
378 if (form == POINT_CONVERSION_HYBRID) {
379 if (y_bit != BN_is_odd(y)) {
380 ECerror(EC_R_INVALID_ENCODING);
381 goto err;
382 }
383 }
384 /*
385 * EC_POINT_set_affine_coordinates checks that the point is
386 * on the curve as required by X9.62.
387 */
388 if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
389 goto err;
390 }
391
392 ret = 1;
393
394 err:
395 BN_CTX_end(ctx);
396 BN_CTX_free(new_ctx);
397 return ret;
398 }
399