1 /* Originally written by Bodo Moeller for the OpenSSL project.
2 * ====================================================================
3 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in
14 * the documentation and/or other materials provided with the
15 * distribution.
16 *
17 * 3. All advertising materials mentioning features or use of this
18 * software must display the following acknowledgment:
19 * "This product includes software developed by the OpenSSL Project
20 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
21 *
22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
23 * endorse or promote products derived from this software without
24 * prior written permission. For written permission, please contact
25 * openssl-core@openssl.org.
26 *
27 * 5. Products derived from this software may not be called "OpenSSL"
28 * nor may "OpenSSL" appear in their names without prior written
29 * permission of the OpenSSL Project.
30 *
31 * 6. Redistributions of any form whatsoever must retain the following
32 * acknowledgment:
33 * "This product includes software developed by the OpenSSL Project
34 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
35 *
36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
39 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
47 * OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
49 *
50 * This product includes cryptographic software written by Eric Young
51 * (eay@cryptsoft.com). This product includes software written by Tim
52 * Hudson (tjh@cryptsoft.com).
53 *
54 */
55 /* ====================================================================
56 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
57 *
58 * Portions of the attached software ("Contribution") are developed by
59 * SUN MICROSYSTEMS, INC., and are contributed to the OpenSSL project.
60 *
61 * The Contribution is licensed pursuant to the OpenSSL open source
62 * license provided above.
63 *
64 * The elliptic curve binary polynomial software is originally written by
65 * Sheueling Chang Shantz and Douglas Stebila of Sun Microsystems
66 * Laboratories. */
67
68 #include <openssl/ec.h>
69
70 #include <openssl/bn.h>
71 #include <openssl/err.h>
72
73 #include "internal.h"
74
75
ec_GFp_simple_point2oct(const EC_GROUP * group,const EC_POINT * point,point_conversion_form_t form,uint8_t * buf,size_t len,BN_CTX * ctx)76 static size_t ec_GFp_simple_point2oct(const EC_GROUP *group,
77 const EC_POINT *point,
78 point_conversion_form_t form,
79 uint8_t *buf, size_t len, BN_CTX *ctx) {
80 size_t ret;
81 BN_CTX *new_ctx = NULL;
82 int used_ctx = 0;
83 BIGNUM *x, *y;
84 size_t field_len, i;
85
86 if ((form != POINT_CONVERSION_COMPRESSED) &&
87 (form != POINT_CONVERSION_UNCOMPRESSED)) {
88 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_FORM);
89 goto err;
90 }
91
92 if (EC_POINT_is_at_infinity(group, point)) {
93 OPENSSL_PUT_ERROR(EC, EC_R_POINT_AT_INFINITY);
94 goto err;
95 }
96
97 /* ret := required output buffer length */
98 field_len = BN_num_bytes(&group->field);
99 ret =
100 (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
101
102 /* if 'buf' is NULL, just return required length */
103 if (buf != NULL) {
104 if (len < ret) {
105 OPENSSL_PUT_ERROR(EC, EC_R_BUFFER_TOO_SMALL);
106 goto err;
107 }
108
109 if (ctx == NULL) {
110 ctx = new_ctx = BN_CTX_new();
111 if (ctx == NULL) {
112 goto err;
113 }
114 }
115
116 BN_CTX_start(ctx);
117 used_ctx = 1;
118 x = BN_CTX_get(ctx);
119 y = BN_CTX_get(ctx);
120 if (y == NULL) {
121 goto err;
122 }
123
124 if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx)) {
125 goto err;
126 }
127
128 if ((form == POINT_CONVERSION_COMPRESSED) &&
129 BN_is_odd(y)) {
130 buf[0] = form + 1;
131 } else {
132 buf[0] = form;
133 }
134 i = 1;
135
136 if (!BN_bn2bin_padded(buf + i, field_len, x)) {
137 OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
138 goto err;
139 }
140 i += field_len;
141
142 if (form == POINT_CONVERSION_UNCOMPRESSED) {
143 if (!BN_bn2bin_padded(buf + i, field_len, y)) {
144 OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
145 goto err;
146 }
147 i += field_len;
148 }
149
150 if (i != ret) {
151 OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
152 goto err;
153 }
154 }
155
156 if (used_ctx) {
157 BN_CTX_end(ctx);
158 }
159 BN_CTX_free(new_ctx);
160 return ret;
161
162 err:
163 if (used_ctx) {
164 BN_CTX_end(ctx);
165 }
166 BN_CTX_free(new_ctx);
167 return 0;
168 }
169
170
ec_GFp_simple_oct2point(const EC_GROUP * group,EC_POINT * point,const uint8_t * buf,size_t len,BN_CTX * ctx)171 static int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
172 const uint8_t *buf, size_t len,
173 BN_CTX *ctx) {
174 point_conversion_form_t form;
175 int y_bit;
176 BN_CTX *new_ctx = NULL;
177 BIGNUM *x, *y;
178 size_t field_len, enc_len;
179 int ret = 0;
180
181 if (len == 0) {
182 OPENSSL_PUT_ERROR(EC, EC_R_BUFFER_TOO_SMALL);
183 return 0;
184 }
185 form = buf[0];
186 y_bit = form & 1;
187 form = form & ~1U;
188 if ((form != POINT_CONVERSION_COMPRESSED &&
189 form != POINT_CONVERSION_UNCOMPRESSED) ||
190 (form == POINT_CONVERSION_UNCOMPRESSED && y_bit)) {
191 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
192 return 0;
193 }
194
195 field_len = BN_num_bytes(&group->field);
196 enc_len =
197 (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
198
199 if (len != enc_len) {
200 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
201 return 0;
202 }
203
204 if (ctx == NULL) {
205 ctx = new_ctx = BN_CTX_new();
206 if (ctx == NULL) {
207 return 0;
208 }
209 }
210
211 BN_CTX_start(ctx);
212 x = BN_CTX_get(ctx);
213 y = BN_CTX_get(ctx);
214 if (x == NULL || y == NULL) {
215 goto err;
216 }
217
218 if (!BN_bin2bn(buf + 1, field_len, x)) {
219 goto err;
220 }
221 if (BN_ucmp(x, &group->field) >= 0) {
222 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
223 goto err;
224 }
225
226 if (form == POINT_CONVERSION_COMPRESSED) {
227 if (!EC_POINT_set_compressed_coordinates_GFp(group, point, x, y_bit, ctx)) {
228 goto err;
229 }
230 } else {
231 if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) {
232 goto err;
233 }
234 if (BN_ucmp(y, &group->field) >= 0) {
235 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
236 goto err;
237 }
238
239 if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) {
240 goto err;
241 }
242 }
243
244 ret = 1;
245
246 err:
247 BN_CTX_end(ctx);
248 BN_CTX_free(new_ctx);
249 return ret;
250 }
251
EC_POINT_oct2point(const EC_GROUP * group,EC_POINT * point,const uint8_t * buf,size_t len,BN_CTX * ctx)252 int EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *point,
253 const uint8_t *buf, size_t len, BN_CTX *ctx) {
254 if (group->meth != point->meth) {
255 OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);
256 return 0;
257 }
258 return ec_GFp_simple_oct2point(group, point, buf, len, ctx);
259 }
260
EC_POINT_point2oct(const EC_GROUP * group,const EC_POINT * point,point_conversion_form_t form,uint8_t * buf,size_t len,BN_CTX * ctx)261 size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *point,
262 point_conversion_form_t form, uint8_t *buf,
263 size_t len, BN_CTX *ctx) {
264 if (group->meth != point->meth) {
265 OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);
266 return 0;
267 }
268 return ec_GFp_simple_point2oct(group, point, form, buf, len, ctx);
269 }
270
ec_GFp_simple_set_compressed_coordinates(const EC_GROUP * group,EC_POINT * point,const BIGNUM * x,int y_bit,BN_CTX * ctx)271 int ec_GFp_simple_set_compressed_coordinates(const EC_GROUP *group,
272 EC_POINT *point, const BIGNUM *x,
273 int y_bit, BN_CTX *ctx) {
274 if (BN_is_negative(x) || BN_cmp(x, &group->field) >= 0) {
275 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_COMPRESSED_POINT);
276 return 0;
277 }
278
279 BN_CTX *new_ctx = NULL;
280 BIGNUM *tmp1, *tmp2, *y;
281 int ret = 0;
282
283 ERR_clear_error();
284
285 if (ctx == NULL) {
286 ctx = new_ctx = BN_CTX_new();
287 if (ctx == NULL) {
288 return 0;
289 }
290 }
291
292 y_bit = (y_bit != 0);
293
294 BN_CTX_start(ctx);
295 tmp1 = BN_CTX_get(ctx);
296 tmp2 = BN_CTX_get(ctx);
297 y = BN_CTX_get(ctx);
298 if (y == NULL) {
299 goto err;
300 }
301
302 /* Recover y. We have a Weierstrass equation
303 * y^2 = x^3 + a*x + b,
304 * so y is one of the square roots of x^3 + a*x + b. */
305
306 /* tmp1 := x^3 */
307 if (group->meth->field_decode == 0) {
308 /* field_{sqr,mul} work on standard representation */
309 if (!group->meth->field_sqr(group, tmp2, x, ctx) ||
310 !group->meth->field_mul(group, tmp1, tmp2, x, ctx)) {
311 goto err;
312 }
313 } else {
314 if (!BN_mod_sqr(tmp2, x, &group->field, ctx) ||
315 !BN_mod_mul(tmp1, tmp2, x, &group->field, ctx)) {
316 goto err;
317 }
318 }
319
320 /* tmp1 := tmp1 + a*x */
321 if (group->a_is_minus3) {
322 if (!BN_mod_lshift1_quick(tmp2, x, &group->field) ||
323 !BN_mod_add_quick(tmp2, tmp2, x, &group->field) ||
324 !BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field)) {
325 goto err;
326 }
327 } else {
328 if (group->meth->field_decode) {
329 if (!group->meth->field_decode(group, tmp2, &group->a, ctx) ||
330 !BN_mod_mul(tmp2, tmp2, x, &group->field, ctx)) {
331 goto err;
332 }
333 } else {
334 /* field_mul works on standard representation */
335 if (!group->meth->field_mul(group, tmp2, &group->a, x, ctx)) {
336 goto err;
337 }
338 }
339
340 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) {
341 goto err;
342 }
343 }
344
345 /* tmp1 := tmp1 + b */
346 if (group->meth->field_decode) {
347 if (!group->meth->field_decode(group, tmp2, &group->b, ctx) ||
348 !BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) {
349 goto err;
350 }
351 } else {
352 if (!BN_mod_add_quick(tmp1, tmp1, &group->b, &group->field)) {
353 goto err;
354 }
355 }
356
357 if (!BN_mod_sqrt(y, tmp1, &group->field, ctx)) {
358 unsigned long err = ERR_peek_last_error();
359
360 if (ERR_GET_LIB(err) == ERR_LIB_BN &&
361 ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
362 ERR_clear_error();
363 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_COMPRESSED_POINT);
364 } else {
365 OPENSSL_PUT_ERROR(EC, ERR_R_BN_LIB);
366 }
367 goto err;
368 }
369
370 if (y_bit != BN_is_odd(y)) {
371 if (BN_is_zero(y)) {
372 OPENSSL_PUT_ERROR(EC, EC_R_INVALID_COMPRESSION_BIT);
373 goto err;
374 }
375 if (!BN_usub(y, &group->field, y)) {
376 goto err;
377 }
378 }
379 if (y_bit != BN_is_odd(y)) {
380 OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
381 goto err;
382 }
383
384 if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) {
385 goto err;
386 }
387
388 ret = 1;
389
390 err:
391 BN_CTX_end(ctx);
392 BN_CTX_free(new_ctx);
393 return ret;
394 }
395
EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP * group,EC_POINT * point,const BIGNUM * x,int y_bit,BN_CTX * ctx)396 int EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP *group,
397 EC_POINT *point, const BIGNUM *x,
398 int y_bit, BN_CTX *ctx) {
399 if (group->meth != point->meth) {
400 OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);
401 return 0;
402 }
403 return ec_GFp_simple_set_compressed_coordinates(group, point, x, y_bit, ctx);
404 }
405