lib/libcrypto/ec/ec2_oct.c

   1 /* $OpenBSD: ec2_oct.c,v 1.8 2017/01/29 17:49:23 beck 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