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 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 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 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