crypto/ec/ecp_oct.c

   1 /*
   2  * Copyright 2011-2021 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
   4  *
   5  * Licensed under the Apache License 2.0 (the "License").  You may not use
   6  * this file except in compliance with the License.  You can obtain a copy
   7  * in the file LICENSE in the source distribution or at
   8  * https://www.openssl.org/source/license.html
   9  */
  10
  11 /*
  12  * ECDSA low level APIs are deprecated for public use, but still ok for
  13  * internal use.
  14  */
  15 #include "internal/deprecated.h"
  16
  17 #include <openssl/err.h>
  18 #include <openssl/symhacks.h>
  19
  20 #include "ec_local.h"
  21
  22 int ossl_ec_GFp_simple_set_compressed_coordinates(const EC_GROUP *group,
  23                                                   EC_POINT *point,
  24                                                   const BIGNUM *x_, int y_bit,
  25                                                   BN_CTX *ctx)
  26 {
  27     BN_CTX *new_ctx = NULL;
  28     BIGNUM *tmp1, *tmp2, *x, *y;
  29     int ret = 0;
  30
  31 #ifndef FIPS_MODULE
  32     /* clear error queue */
  33     ERR_clear_error();
  34 #endif
  35
  36     if (ctx == NULL) {
  37         ctx = new_ctx = BN_CTX_new_ex(group->libctx);
  38         if (ctx == NULL)
  39             return 0;
  40     }
  41
  42     y_bit = (y_bit != 0);
  43
  44     BN_CTX_start(ctx);
  45     tmp1 = BN_CTX_get(ctx);
  46     tmp2 = BN_CTX_get(ctx);
  47     x = BN_CTX_get(ctx);
  48     y = BN_CTX_get(ctx);
  49     if (y == NULL)
  50         goto err;
  51
  52     /*-
  53      * Recover y.  We have a Weierstrass equation
  54      *     y^2 = x^3 + a*x + b,
  55      * so  y  is one of the square roots of  x^3 + a*x + b.
  56      */
  57
  58     /* tmp1 := x^3 */
  59     if (!BN_nnmod(x, x_, group->field, ctx))
  60         goto err;
  61     if (group->meth->field_decode == 0) {
  62         /* field_{sqr,mul} work on standard representation */
  63         if (!group->meth->field_sqr(group, tmp2, x_, ctx))
  64             goto err;
  65         if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx))
  66             goto err;
  67     } else {
  68         if (!BN_mod_sqr(tmp2, x_, group->field, ctx))
  69             goto err;
  70         if (!BN_mod_mul(tmp1, tmp2, x_, group->field, ctx))
  71             goto err;
  72     }
  73
  74     /* tmp1 := tmp1 + a*x */
  75     if (group->a_is_minus3) {
  76         if (!BN_mod_lshift1_quick(tmp2, x, group->field))
  77             goto err;
  78         if (!BN_mod_add_quick(tmp2, tmp2, x, group->field))
  79             goto err;
  80         if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, group->field))
  81             goto err;
  82     } else {
  83         if (group->meth->field_decode) {
  84             if (!group->meth->field_decode(group, tmp2, group->a, ctx))
  85                 goto err;
  86             if (!BN_mod_mul(tmp2, tmp2, x, group->field, ctx))
  87                 goto err;
  88         } else {
  89             /* field_mul works on standard representation */
  90             if (!group->meth->field_mul(group, tmp2, group->a, x, ctx))
  91                 goto err;
  92         }
  93
  94         if (!BN_mod_add_quick(tmp1, tmp1, tmp2, group->field))
  95             goto err;
  96     }
  97
  98     /* tmp1 := tmp1 + b */
  99     if (group->meth->field_decode) {
 100         if (!group->meth->field_decode(group, tmp2, group->b, ctx))
 101             goto err;
 102         if (!BN_mod_add_quick(tmp1, tmp1, tmp2, group->field))
 103             goto err;
 104     } else {
 105         if (!BN_mod_add_quick(tmp1, tmp1, group->b, group->field))
 106             goto err;
 107     }
 108
 109     if (!BN_mod_sqrt(y, tmp1, group->field, ctx)) {
 110 #ifndef FIPS_MODULE
 111         unsigned long err = ERR_peek_last_error();
 112
 113         if (ERR_GET_LIB(err) == ERR_LIB_BN
 114             && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
 115             ERR_clear_error();
 116             ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
 117         } else
 118 #endif
 119         {
 120             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 121         }
 122         goto err;
 123     }
 124
 125     if (y_bit != BN_is_odd(y)) {
 126         if (BN_is_zero(y)) {
 127             int kron;
 128
 129             kron = BN_kronecker(x, group->field, ctx);
 130             if (kron == -2)
 131                 goto err;
 132
 133             if (kron == 1)
 134                 ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSION_BIT);
 135             else
 136                 /*
 137                  * BN_mod_sqrt() should have caught this error (not a square)
 138                  */
 139                 ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
 140             goto err;
 141         }
 142         if (!BN_usub(y, group->field, y))
 143             goto err;
 144     }
 145     if (y_bit != BN_is_odd(y)) {
 146         ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
 147         goto err;
 148     }
 149
 150     if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
 151         goto err;
 152
 153     ret = 1;
 154
 155  err:
 156     BN_CTX_end(ctx);
 157     BN_CTX_free(new_ctx);
 158     return ret;
 159 }
 160
 161 size_t ossl_ec_GFp_simple_point2oct(const EC_GROUP *group, const EC_POINT *point,
 162                                     point_conversion_form_t form,
 163                                     unsigned char *buf, size_t len, BN_CTX *ctx)
 164 {
 165     size_t ret;
 166     BN_CTX *new_ctx = NULL;
 167     int used_ctx = 0;
 168     BIGNUM *x, *y;
 169     size_t field_len, i, skip;
 170
 171     if ((form != POINT_CONVERSION_COMPRESSED)
 172         && (form != POINT_CONVERSION_UNCOMPRESSED)
 173         && (form != POINT_CONVERSION_HYBRID)) {
 174         ERR_raise(ERR_LIB_EC, EC_R_INVALID_FORM);
 175         goto err;
 176     }
 177
 178     if (EC_POINT_is_at_infinity(group, point)) {
 179         /* encodes to a single 0 octet */
 180         if (buf != NULL) {
 181             if (len < 1) {
 182                 ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
 183                 return 0;
 184             }
 185             buf[0] = 0;
 186         }
 187         return 1;
 188     }
 189
 190     /* ret := required output buffer length */
 191     field_len = BN_num_bytes(group->field);
 192     ret =
 193         (form ==
 194          POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
 195
 196     /* if 'buf' is NULL, just return required length */
 197     if (buf != NULL) {
 198         if (len < ret) {
 199             ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
 200             goto err;
 201         }
 202
 203         if (ctx == NULL) {
 204             ctx = new_ctx = BN_CTX_new_ex(group->libctx);
 205             if (ctx == NULL)
 206                 return 0;
 207         }
 208
 209         BN_CTX_start(ctx);
 210         used_ctx = 1;
 211         x = BN_CTX_get(ctx);
 212         y = BN_CTX_get(ctx);
 213         if (y == NULL)
 214             goto err;
 215
 216         if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
 217             goto err;
 218
 219         if ((form == POINT_CONVERSION_COMPRESSED
 220              || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y))
 221             buf[0] = form + 1;
 222         else
 223             buf[0] = form;
 224
 225         i = 1;
 226
 227         skip = field_len - BN_num_bytes(x);
 228         if (skip > field_len) {
 229             ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
 230             goto err;
 231         }
 232         while (skip > 0) {
 233             buf[i++] = 0;
 234             skip--;
 235         }
 236         skip = BN_bn2bin(x, buf + i);
 237         i += skip;
 238         if (i != 1 + field_len) {
 239             ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
 240             goto err;
 241         }
 242
 243         if (form == POINT_CONVERSION_UNCOMPRESSED
 244             || form == POINT_CONVERSION_HYBRID) {
 245             skip = field_len - BN_num_bytes(y);
 246             if (skip > field_len) {
 247                 ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
 248                 goto err;
 249             }
 250             while (skip > 0) {
 251                 buf[i++] = 0;
 252                 skip--;
 253             }
 254             skip = BN_bn2bin(y, buf + i);
 255             i += skip;
 256         }
 257
 258         if (i != ret) {
 259             ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
 260             goto err;
 261         }
 262     }
 263
 264     if (used_ctx)
 265         BN_CTX_end(ctx);
 266     BN_CTX_free(new_ctx);
 267     return ret;
 268
 269  err:
 270     if (used_ctx)
 271         BN_CTX_end(ctx);
 272     BN_CTX_free(new_ctx);
 273     return 0;
 274 }
 275
 276 int ossl_ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
 277                                  const unsigned char *buf, size_t len,
 278                                  BN_CTX *ctx)
 279 {
 280     point_conversion_form_t form;
 281     int y_bit;
 282     BN_CTX *new_ctx = NULL;
 283     BIGNUM *x, *y;
 284     size_t field_len, enc_len;
 285     int ret = 0;
 286
 287     if (len == 0) {
 288         ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
 289         return 0;
 290     }
 291     form = buf[0];
 292     y_bit = form & 1;
 293     form = form & ~1U;
 294     if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
 295         && (form != POINT_CONVERSION_UNCOMPRESSED)
 296         && (form != POINT_CONVERSION_HYBRID)) {
 297         ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 298         return 0;
 299     }
 300     if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
 301         ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 302         return 0;
 303     }
 304
 305     if (form == 0) {
 306         if (len != 1) {
 307             ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 308             return 0;
 309         }
 310
 311         return EC_POINT_set_to_infinity(group, point);
 312     }
 313
 314     field_len = BN_num_bytes(group->field);
 315     enc_len =
 316         (form ==
 317          POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
 318
 319     if (len != enc_len) {
 320         ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 321         return 0;
 322     }
 323
 324     if (ctx == NULL) {
 325         ctx = new_ctx = BN_CTX_new_ex(group->libctx);
 326         if (ctx == NULL)
 327             return 0;
 328     }
 329
 330     BN_CTX_start(ctx);
 331     x = BN_CTX_get(ctx);
 332     y = BN_CTX_get(ctx);
 333     if (y == NULL)
 334         goto err;
 335
 336     if (!BN_bin2bn(buf + 1, field_len, x))
 337         goto err;
 338     if (BN_ucmp(x, group->field) >= 0) {
 339         ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 340         goto err;
 341     }
 342
 343     if (form == POINT_CONVERSION_COMPRESSED) {
 344         if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
 345             goto err;
 346     } else {
 347         if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
 348             goto err;
 349         if (BN_ucmp(y, group->field) >= 0) {
 350             ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 351             goto err;
 352         }
 353         if (form == POINT_CONVERSION_HYBRID) {
 354             if (y_bit != BN_is_odd(y)) {
 355                 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
 356                 goto err;
 357             }
 358         }
 359
 360         /*
 361          * EC_POINT_set_affine_coordinates is responsible for checking that
 362          * the point is on the curve.
 363          */
 364         if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
 365             goto err;
 366     }
 367
 368     ret = 1;
 369
 370  err:
 371     BN_CTX_end(ctx);
 372     BN_CTX_free(new_ctx);
 373     return ret;
 374 }