1/* crypto/ec/ecp_oct.c */ 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#include <openssl/symhacks.h> 67 68#include "ec_lcl.h" 69 70int ec_GFp_simple_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point, 71 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 { 82 ctx = new_ctx = BN_CTX_new(); 83 if (ctx == NULL) 84 return 0; 85 } 86 87 y_bit = (y_bit != 0); 88 89 BN_CTX_start(ctx); 90 tmp1 = BN_CTX_get(ctx); 91 tmp2 = BN_CTX_get(ctx); 92 x = BN_CTX_get(ctx); 93 y = BN_CTX_get(ctx); 94 if (y == NULL) goto err; 95 96 /* Recover y. We have a Weierstrass equation 97 * y^2 = x^3 + a*x + b, 98 * so y is one of the square roots of x^3 + a*x + b. 99 */ 100 101 /* tmp1 := x^3 */ 102 if (!BN_nnmod(x, x_, &group->field,ctx)) goto err; 103 if (group->meth->field_decode == 0) 104 { 105 /* field_{sqr,mul} work on standard representation */ 106 if (!group->meth->field_sqr(group, tmp2, x_, ctx)) goto err; 107 if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx)) goto err; 108 } 109 else 110 { 111 if (!BN_mod_sqr(tmp2, x_, &group->field, ctx)) goto err; 112 if (!BN_mod_mul(tmp1, tmp2, x_, &group->field, ctx)) goto err; 113 } 114 115 /* tmp1 := tmp1 + a*x */ 116 if (group->a_is_minus3) 117 { 118 if (!BN_mod_lshift1_quick(tmp2, x, &group->field)) goto err; 119 if (!BN_mod_add_quick(tmp2, tmp2, x, &group->field)) goto err; 120 if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field)) goto err; 121 } 122 else 123 { 124 if (group->meth->field_decode) 125 { 126 if (!group->meth->field_decode(group, tmp2, &group->a, ctx)) goto err; 127 if (!BN_mod_mul(tmp2, tmp2, x, &group->field, ctx)) goto err; 128 } 129 else 130 { 131 /* field_mul works on standard representation */ 132 if (!group->meth->field_mul(group, tmp2, &group->a, x, ctx)) goto err; 133 } 134 135 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) goto err; 136 } 137 138 /* tmp1 := tmp1 + b */ 139 if (group->meth->field_decode) 140 { 141 if (!group->meth->field_decode(group, tmp2, &group->b, ctx)) goto err; 142 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) goto err; 143 } 144 else 145 { 146 if (!BN_mod_add_quick(tmp1, tmp1, &group->b, &group->field)) goto err; 147 } 148 149 if (!BN_mod_sqrt(y, tmp1, &group->field, ctx)) 150 { 151 unsigned long err = ERR_peek_last_error(); 152 153 if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) 154 { 155 ERR_clear_error(); 156 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT); 157 } 158 else 159 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_BN_LIB); 160 goto err; 161 } 162 163 if (y_bit != BN_is_odd(y)) 164 { 165 if (BN_is_zero(y)) 166 { 167 int kron; 168 169 kron = BN_kronecker(x, &group->field, ctx); 170 if (kron == -2) goto err; 171 172 if (kron == 1) 173 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSION_BIT); 174 else 175 /* BN_mod_sqrt() should have cought this error (not a square) */ 176 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT); 177 goto err; 178 } 179 if (!BN_usub(y, &group->field, y)) goto err; 180 } 181 if (y_bit != BN_is_odd(y)) 182 { 183 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_INTERNAL_ERROR); 184 goto err; 185 } 186 187 if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err; 188 189 ret = 1; 190 191 err: 192 BN_CTX_end(ctx); 193 if (new_ctx != NULL) 194 BN_CTX_free(new_ctx); 195 return ret; 196 } 197 198 199size_t ec_GFp_simple_point2oct(const EC_GROUP *group, const EC_POINT *point, point_conversion_form_t form, 200 unsigned char *buf, size_t len, BN_CTX *ctx) 201 { 202 size_t ret; 203 BN_CTX *new_ctx = NULL; 204 int used_ctx = 0; 205 BIGNUM *x, *y; 206 size_t field_len, i, skip; 207 208 if ((form != POINT_CONVERSION_COMPRESSED) 209 && (form != POINT_CONVERSION_UNCOMPRESSED) 210 && (form != POINT_CONVERSION_HYBRID)) 211 { 212 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_INVALID_FORM); 213 goto err; 214 } 215 216 if (EC_POINT_is_at_infinity(group, point)) 217 { 218 /* encodes to a single 0 octet */ 219 if (buf != NULL) 220 { 221 if (len < 1) 222 { 223 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL); 224 return 0; 225 } 226 buf[0] = 0; 227 } 228 return 1; 229 } 230 231 232 /* ret := required output buffer length */ 233 field_len = BN_num_bytes(&group->field); 234 ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len; 235 236 /* if 'buf' is NULL, just return required length */ 237 if (buf != NULL) 238 { 239 if (len < ret) 240 { 241 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL); 242 goto err; 243 } 244 245 if (ctx == NULL) 246 { 247 ctx = new_ctx = BN_CTX_new(); 248 if (ctx == NULL) 249 return 0; 250 } 251 252 BN_CTX_start(ctx); 253 used_ctx = 1; 254 x = BN_CTX_get(ctx); 255 y = BN_CTX_get(ctx); 256 if (y == NULL) goto err; 257 258 if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx)) goto err; 259 260 if ((form == POINT_CONVERSION_COMPRESSED || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y)) 261 buf[0] = form + 1; 262 else 263 buf[0] = form; 264 265 i = 1; 266 267 skip = field_len - BN_num_bytes(x); 268 if (skip > field_len) 269 { 270 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 271 goto err; 272 } 273 while (skip > 0) 274 { 275 buf[i++] = 0; 276 skip--; 277 } 278 skip = BN_bn2bin(x, buf + i); 279 i += skip; 280 if (i != 1 + field_len) 281 { 282 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 283 goto err; 284 } 285 286 if (form == POINT_CONVERSION_UNCOMPRESSED || form == POINT_CONVERSION_HYBRID) 287 { 288 skip = field_len - BN_num_bytes(y); 289 if (skip > field_len) 290 { 291 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 292 goto err; 293 } 294 while (skip > 0) 295 { 296 buf[i++] = 0; 297 skip--; 298 } 299 skip = BN_bn2bin(y, buf + i); 300 i += skip; 301 } 302 303 if (i != ret) 304 { 305 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 306 goto err; 307 } 308 } 309 310 if (used_ctx) 311 BN_CTX_end(ctx); 312 if (new_ctx != NULL) 313 BN_CTX_free(new_ctx); 314 return ret; 315 316 err: 317 if (used_ctx) 318 BN_CTX_end(ctx); 319 if (new_ctx != NULL) 320 BN_CTX_free(new_ctx); 321 return 0; 322 } 323 324 325int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point, 326 const unsigned char *buf, size_t len, BN_CTX *ctx) 327 { 328 point_conversion_form_t form; 329 int y_bit; 330 BN_CTX *new_ctx = NULL; 331 BIGNUM *x, *y; 332 size_t field_len, enc_len; 333 int ret = 0; 334 335 if (len == 0) 336 { 337 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL); 338 return 0; 339 } 340 form = buf[0]; 341 y_bit = form & 1; 342 form = form & ~1U; 343 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED) 344 && (form != POINT_CONVERSION_UNCOMPRESSED) 345 && (form != POINT_CONVERSION_HYBRID)) 346 { 347 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 348 return 0; 349 } 350 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) 351 { 352 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 353 return 0; 354 } 355 356 if (form == 0) 357 { 358 if (len != 1) 359 { 360 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 361 return 0; 362 } 363 364 return EC_POINT_set_to_infinity(group, point); 365 } 366 367 field_len = BN_num_bytes(&group->field); 368 enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len; 369 370 if (len != enc_len) 371 { 372 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 373 return 0; 374 } 375 376 if (ctx == NULL) 377 { 378 ctx = new_ctx = BN_CTX_new(); 379 if (ctx == NULL) 380 return 0; 381 } 382 383 BN_CTX_start(ctx); 384 x = BN_CTX_get(ctx); 385 y = BN_CTX_get(ctx); 386 if (y == NULL) goto err; 387 388 if (!BN_bin2bn(buf + 1, field_len, x)) goto err; 389 if (BN_ucmp(x, &group->field) >= 0) 390 { 391 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 392 goto err; 393 } 394 395 if (form == POINT_CONVERSION_COMPRESSED) 396 { 397 if (!EC_POINT_set_compressed_coordinates_GFp(group, point, x, y_bit, ctx)) goto err; 398 } 399 else 400 { 401 if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) goto err; 402 if (BN_ucmp(y, &group->field) >= 0) 403 { 404 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 405 goto err; 406 } 407 if (form == POINT_CONVERSION_HYBRID) 408 { 409 if (y_bit != BN_is_odd(y)) 410 { 411 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 412 goto err; 413 } 414 } 415 416 if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err; 417 } 418 419 if (!EC_POINT_is_on_curve(group, point, ctx)) /* test required by X9.62 */ 420 { 421 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE); 422 goto err; 423 } 424 425 ret = 1; 426 427 err: 428 BN_CTX_end(ctx); 429 if (new_ctx != NULL) 430 BN_CTX_free(new_ctx); 431 return ret; 432 } 433 434