1 /* $OpenBSD: ec2_oct.c,v 1.11 2018/07/15 16:27:39 tb Exp $ */ 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/opensslconf.h> 71 72 #include <openssl/err.h> 73 74 #include "ec_lcl.h" 75 76 #ifndef OPENSSL_NO_EC2M 77 78 /* Calculates and sets the affine coordinates of an EC_POINT from the given 79 * compressed coordinates. Uses algorithm 2.3.4 of SEC 1. 80 * Note that the simple implementation only uses affine coordinates. 81 * 82 * The method is from the following publication: 83 * 84 * Harper, Menezes, Vanstone: 85 * "Public-Key Cryptosystems with Very Small Key Lengths", 86 * EUROCRYPT '92, Springer-Verlag LNCS 658, 87 * published February 1993 88 * 89 * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe 90 * the same method, but claim no priority date earlier than July 29, 1994 91 * (and additionally fail to cite the EUROCRYPT '92 publication as prior art). 92 */ 93 int 94 ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point, 95 const BIGNUM *x_, int y_bit, 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 ERR_clear_error(); 103 104 if (ctx == NULL) { 105 ctx = new_ctx = BN_CTX_new(); 106 if (ctx == NULL) 107 return 0; 108 } 109 y_bit = (y_bit != 0) ? 1 : 0; 110 111 BN_CTX_start(ctx); 112 if ((tmp = BN_CTX_get(ctx)) == NULL) 113 goto err; 114 if ((x = BN_CTX_get(ctx)) == NULL) 115 goto err; 116 if ((y = BN_CTX_get(ctx)) == NULL) 117 goto err; 118 if ((z = BN_CTX_get(ctx)) == NULL) 119 goto err; 120 121 if (!BN_GF2m_mod_arr(x, x_, group->poly)) 122 goto err; 123 if (BN_is_zero(x)) { 124 if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx)) 125 goto err; 126 } else { 127 if (!group->meth->field_sqr(group, tmp, x, ctx)) 128 goto err; 129 if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx)) 130 goto err; 131 if (!BN_GF2m_add(tmp, &group->a, tmp)) 132 goto err; 133 if (!BN_GF2m_add(tmp, x, tmp)) 134 goto err; 135 if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) { 136 unsigned long err = ERR_peek_last_error(); 137 138 if (ERR_GET_LIB(err) == ERR_LIB_BN && 139 ERR_GET_REASON(err) == BN_R_NO_SOLUTION) { 140 ERR_clear_error(); 141 ECerror(EC_R_INVALID_COMPRESSED_POINT); 142 } else 143 ECerror(ERR_R_BN_LIB); 144 goto err; 145 } 146 z0 = (BN_is_odd(z)) ? 1 : 0; 147 if (!group->meth->field_mul(group, y, x, z, ctx)) 148 goto err; 149 if (z0 != y_bit) { 150 if (!BN_GF2m_add(y, y, x)) 151 goto err; 152 } 153 } 154 155 if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx)) 156 goto err; 157 158 ret = 1; 159 160 err: 161 BN_CTX_end(ctx); 162 BN_CTX_free(new_ctx); 163 return ret; 164 } 165 166 167 /* Converts an EC_POINT to an octet string. 168 * If buf is NULL, the encoded length will be returned. 169 * If the length len of buf is smaller than required an error will be returned. 170 */ 171 size_t 172 ec_GF2m_simple_point2oct(const EC_GROUP *group, const EC_POINT *point, 173 point_conversion_form_t form, 174 unsigned char *buf, size_t len, BN_CTX * ctx) 175 { 176 size_t ret; 177 BN_CTX *new_ctx = NULL; 178 int used_ctx = 0; 179 BIGNUM *x, *y, *yxi; 180 size_t field_len, i, skip; 181 182 if ((form != POINT_CONVERSION_COMPRESSED) 183 && (form != POINT_CONVERSION_UNCOMPRESSED) 184 && (form != POINT_CONVERSION_HYBRID)) { 185 ECerror(EC_R_INVALID_FORM); 186 goto err; 187 } 188 if (EC_POINT_is_at_infinity(group, point) > 0) { 189 /* encodes to a single 0 octet */ 190 if (buf != NULL) { 191 if (len < 1) { 192 ECerror(EC_R_BUFFER_TOO_SMALL); 193 return 0; 194 } 195 buf[0] = 0; 196 } 197 return 1; 198 } 199 /* ret := required output buffer length */ 200 field_len = (EC_GROUP_get_degree(group) + 7) / 8; 201 ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 202 1 + 2 * field_len; 203 204 /* if 'buf' is NULL, just return required length */ 205 if (buf != NULL) { 206 if (len < ret) { 207 ECerror(EC_R_BUFFER_TOO_SMALL); 208 goto err; 209 } 210 if (ctx == NULL) { 211 ctx = new_ctx = BN_CTX_new(); 212 if (ctx == NULL) 213 return 0; 214 } 215 BN_CTX_start(ctx); 216 used_ctx = 1; 217 if ((x = BN_CTX_get(ctx)) == NULL) 218 goto err; 219 if ((y = BN_CTX_get(ctx)) == NULL) 220 goto err; 221 if ((yxi = BN_CTX_get(ctx)) == NULL) 222 goto err; 223 224 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx)) 225 goto err; 226 227 buf[0] = form; 228 if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) { 229 if (!group->meth->field_div(group, yxi, y, x, ctx)) 230 goto err; 231 if (BN_is_odd(yxi)) 232 buf[0]++; 233 } 234 i = 1; 235 236 skip = field_len - BN_num_bytes(x); 237 if (skip > field_len) { 238 ECerror(ERR_R_INTERNAL_ERROR); 239 goto err; 240 } 241 while (skip > 0) { 242 buf[i++] = 0; 243 skip--; 244 } 245 skip = BN_bn2bin(x, buf + i); 246 i += skip; 247 if (i != 1 + field_len) { 248 ECerror(ERR_R_INTERNAL_ERROR); 249 goto err; 250 } 251 if (form == POINT_CONVERSION_UNCOMPRESSED || 252 form == POINT_CONVERSION_HYBRID) { 253 skip = field_len - BN_num_bytes(y); 254 if (skip > field_len) { 255 ECerror(ERR_R_INTERNAL_ERROR); 256 goto err; 257 } 258 while (skip > 0) { 259 buf[i++] = 0; 260 skip--; 261 } 262 skip = BN_bn2bin(y, buf + i); 263 i += skip; 264 } 265 if (i != ret) { 266 ECerror(ERR_R_INTERNAL_ERROR); 267 goto err; 268 } 269 } 270 if (used_ctx) 271 BN_CTX_end(ctx); 272 BN_CTX_free(new_ctx); 273 return ret; 274 275 err: 276 if (used_ctx) 277 BN_CTX_end(ctx); 278 BN_CTX_free(new_ctx); 279 return 0; 280 } 281 282 283 /* Converts an octet string representation to an EC_POINT. 284 * Note that the simple implementation only uses affine coordinates. 285 */ 286 int 287 ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point, 288 const unsigned char *buf, size_t len, BN_CTX *ctx) 289 { 290 point_conversion_form_t form; 291 int y_bit; 292 BN_CTX *new_ctx = NULL; 293 BIGNUM *x, *y, *yxi; 294 size_t field_len, enc_len; 295 int ret = 0; 296 297 if (len == 0) { 298 ECerror(EC_R_BUFFER_TOO_SMALL); 299 return 0; 300 } 301 form = buf[0]; 302 y_bit = form & 1; 303 form = form & ~1U; 304 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED) && 305 (form != POINT_CONVERSION_UNCOMPRESSED) && 306 (form != POINT_CONVERSION_HYBRID)) { 307 ECerror(EC_R_INVALID_ENCODING); 308 return 0; 309 } 310 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) { 311 ECerror(EC_R_INVALID_ENCODING); 312 return 0; 313 } 314 if (form == 0) { 315 if (len != 1) { 316 ECerror(EC_R_INVALID_ENCODING); 317 return 0; 318 } 319 return EC_POINT_set_to_infinity(group, point); 320 } 321 field_len = (EC_GROUP_get_degree(group) + 7) / 8; 322 enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 323 1 + 2 * field_len; 324 325 if (len != enc_len) { 326 ECerror(EC_R_INVALID_ENCODING); 327 return 0; 328 } 329 if (ctx == NULL) { 330 ctx = new_ctx = BN_CTX_new(); 331 if (ctx == NULL) 332 return 0; 333 } 334 BN_CTX_start(ctx); 335 if ((x = BN_CTX_get(ctx)) == NULL) 336 goto err; 337 if ((y = BN_CTX_get(ctx)) == NULL) 338 goto err; 339 if ((yxi = BN_CTX_get(ctx)) == NULL) 340 goto err; 341 342 if (!BN_bin2bn(buf + 1, field_len, x)) 343 goto err; 344 if (BN_ucmp(x, &group->field) >= 0) { 345 ECerror(EC_R_INVALID_ENCODING); 346 goto err; 347 } 348 if (form == POINT_CONVERSION_COMPRESSED) { 349 if (!EC_POINT_set_compressed_coordinates_GF2m(group, point, x, y_bit, ctx)) 350 goto err; 351 } else { 352 if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) 353 goto err; 354 if (BN_ucmp(y, &group->field) >= 0) { 355 ECerror(EC_R_INVALID_ENCODING); 356 goto err; 357 } 358 if (form == POINT_CONVERSION_HYBRID) { 359 if (!group->meth->field_div(group, yxi, y, x, ctx)) 360 goto err; 361 if (y_bit != BN_is_odd(yxi)) { 362 ECerror(EC_R_INVALID_ENCODING); 363 goto err; 364 } 365 } 366 if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx)) 367 goto err; 368 } 369 370 /* test required by X9.62 */ 371 if (EC_POINT_is_on_curve(group, point, ctx) <= 0) { 372 ECerror(EC_R_POINT_IS_NOT_ON_CURVE); 373 goto err; 374 } 375 ret = 1; 376 377 err: 378 BN_CTX_end(ctx); 379 BN_CTX_free(new_ctx); 380 return ret; 381 } 382 #endif 383