crypto/ec/ecp_mont.c

   1 /*
   2  * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
   4  *
   5  * Licensed under the OpenSSL license (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 #include <openssl/err.h>
  12
  13 #include "ec_local.h"
  14
  15 const EC_METHOD *EC_GFp_mont_method(void)
  16 {
  17     static const EC_METHOD ret = {
  18         EC_FLAGS_DEFAULT_OCT,
  19         NID_X9_62_prime_field,
  20         ec_GFp_mont_group_init,
  21         ec_GFp_mont_group_finish,
  22         ec_GFp_mont_group_clear_finish,
  23         ec_GFp_mont_group_copy,
  24         ec_GFp_mont_group_set_curve,
  25         ec_GFp_simple_group_get_curve,
  26         ec_GFp_simple_group_get_degree,
  27         ec_group_simple_order_bits,
  28         ec_GFp_simple_group_check_discriminant,
  29         ec_GFp_simple_point_init,
  30         ec_GFp_simple_point_finish,
  31         ec_GFp_simple_point_clear_finish,
  32         ec_GFp_simple_point_copy,
  33         ec_GFp_simple_point_set_to_infinity,
  34         ec_GFp_simple_set_Jprojective_coordinates_GFp,
  35         ec_GFp_simple_get_Jprojective_coordinates_GFp,
  36         ec_GFp_simple_point_set_affine_coordinates,
  37         ec_GFp_simple_point_get_affine_coordinates,
  38         0, 0, 0,
  39         ec_GFp_simple_add,
  40         ec_GFp_simple_dbl,
  41         ec_GFp_simple_invert,
  42         ec_GFp_simple_is_at_infinity,
  43         ec_GFp_simple_is_on_curve,
  44         ec_GFp_simple_cmp,
  45         ec_GFp_simple_make_affine,
  46         ec_GFp_simple_points_make_affine,
  47         0 /* mul */ ,
  48         0 /* precompute_mult */ ,
  49         0 /* have_precompute_mult */ ,
  50         ec_GFp_mont_field_mul,
  51         ec_GFp_mont_field_sqr,
  52         0 /* field_div */ ,
  53         ec_GFp_mont_field_inv,
  54         ec_GFp_mont_field_encode,
  55         ec_GFp_mont_field_decode,
  56         ec_GFp_mont_field_set_to_one,
  57         ec_key_simple_priv2oct,
  58         ec_key_simple_oct2priv,
  59         0, /* set private */
  60         ec_key_simple_generate_key,
  61         ec_key_simple_check_key,
  62         ec_key_simple_generate_public_key,
  63         0, /* keycopy */
  64         0, /* keyfinish */
  65         ecdh_simple_compute_key,
  66         0, /* field_inverse_mod_ord */
  67         ec_GFp_simple_blind_coordinates,
  68         ec_GFp_simple_ladder_pre,
  69         ec_GFp_simple_ladder_step,
  70         ec_GFp_simple_ladder_post
  71     };
  72
  73     return &ret;
  74 }
  75
  76 int ec_GFp_mont_group_init(EC_GROUP *group)
  77 {
  78     int ok;
  79
  80     ok = ec_GFp_simple_group_init(group);
  81     group->field_data1 = NULL;
  82     group->field_data2 = NULL;
  83     return ok;
  84 }
  85
  86 void ec_GFp_mont_group_finish(EC_GROUP *group)
  87 {
  88     BN_MONT_CTX_free(group->field_data1);
  89     group->field_data1 = NULL;
  90     BN_free(group->field_data2);
  91     group->field_data2 = NULL;
  92     ec_GFp_simple_group_finish(group);
  93 }
  94
  95 void ec_GFp_mont_group_clear_finish(EC_GROUP *group)
  96 {
  97     BN_MONT_CTX_free(group->field_data1);
  98     group->field_data1 = NULL;
  99     BN_clear_free(group->field_data2);
 100     group->field_data2 = NULL;
 101     ec_GFp_simple_group_clear_finish(group);
 102 }
 103
 104 int ec_GFp_mont_group_copy(EC_GROUP *dest, const EC_GROUP *src)
 105 {
 106     BN_MONT_CTX_free(dest->field_data1);
 107     dest->field_data1 = NULL;
 108     BN_clear_free(dest->field_data2);
 109     dest->field_data2 = NULL;
 110
 111     if (!ec_GFp_simple_group_copy(dest, src))
 112         return 0;
 113
 114     if (src->field_data1 != NULL) {
 115         dest->field_data1 = BN_MONT_CTX_new();
 116         if (dest->field_data1 == NULL)
 117             return 0;
 118         if (!BN_MONT_CTX_copy(dest->field_data1, src->field_data1))
 119             goto err;
 120     }
 121     if (src->field_data2 != NULL) {
 122         dest->field_data2 = BN_dup(src->field_data2);
 123         if (dest->field_data2 == NULL)
 124             goto err;
 125     }
 126
 127     return 1;
 128
 129  err:
 130     BN_MONT_CTX_free(dest->field_data1);
 131     dest->field_data1 = NULL;
 132     return 0;
 133 }
 134
 135 int ec_GFp_mont_group_set_curve(EC_GROUP *group, const BIGNUM *p,
 136                                 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
 137 {
 138     BN_CTX *new_ctx = NULL;
 139     BN_MONT_CTX *mont = NULL;
 140     BIGNUM *one = NULL;
 141     int ret = 0;
 142
 143     BN_MONT_CTX_free(group->field_data1);
 144     group->field_data1 = NULL;
 145     BN_free(group->field_data2);
 146     group->field_data2 = NULL;
 147
 148     if (ctx == NULL) {
 149         ctx = new_ctx = BN_CTX_new();
 150         if (ctx == NULL)
 151             return 0;
 152     }
 153
 154     mont = BN_MONT_CTX_new();
 155     if (mont == NULL)
 156         goto err;
 157     if (!BN_MONT_CTX_set(mont, p, ctx)) {
 158         ECerr(EC_F_EC_GFP_MONT_GROUP_SET_CURVE, ERR_R_BN_LIB);
 159         goto err;
 160     }
 161     one = BN_new();
 162     if (one == NULL)
 163         goto err;
 164     if (!BN_to_montgomery(one, BN_value_one(), mont, ctx))
 165         goto err;
 166
 167     group->field_data1 = mont;
 168     mont = NULL;
 169     group->field_data2 = one;
 170     one = NULL;
 171
 172     ret = ec_GFp_simple_group_set_curve(group, p, a, b, ctx);
 173
 174     if (!ret) {
 175         BN_MONT_CTX_free(group->field_data1);
 176         group->field_data1 = NULL;
 177         BN_free(group->field_data2);
 178         group->field_data2 = NULL;
 179     }
 180
 181  err:
 182     BN_free(one);
 183     BN_CTX_free(new_ctx);
 184     BN_MONT_CTX_free(mont);
 185     return ret;
 186 }
 187
 188 int ec_GFp_mont_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
 189                           const BIGNUM *b, BN_CTX *ctx)
 190 {
 191     if (group->field_data1 == NULL) {
 192         ECerr(EC_F_EC_GFP_MONT_FIELD_MUL, EC_R_NOT_INITIALIZED);
 193         return 0;
 194     }
 195
 196     return BN_mod_mul_montgomery(r, a, b, group->field_data1, ctx);
 197 }
 198
 199 int ec_GFp_mont_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
 200                           BN_CTX *ctx)
 201 {
 202     if (group->field_data1 == NULL) {
 203         ECerr(EC_F_EC_GFP_MONT_FIELD_SQR, EC_R_NOT_INITIALIZED);
 204         return 0;
 205     }
 206
 207     return BN_mod_mul_montgomery(r, a, a, group->field_data1, ctx);
 208 }
 209
 210 /*-
 211  * Computes the multiplicative inverse of a in GF(p), storing the result in r.
 212  * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error.
 213  * We have a Mont structure, so SCA hardening is FLT inversion.
 214  */
 215 int ec_GFp_mont_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
 216                             BN_CTX *ctx)
 217 {
 218     BIGNUM *e = NULL;
 219     BN_CTX *new_ctx = NULL;
 220     int ret = 0;
 221
 222     if (group->field_data1 == NULL)
 223         return 0;
 224
 225     if (ctx == NULL && (ctx = new_ctx = BN_CTX_secure_new()) == NULL)
 226         return 0;
 227
 228     BN_CTX_start(ctx);
 229     if ((e = BN_CTX_get(ctx)) == NULL)
 230         goto err;
 231
 232     /* Inverse in constant time with Fermats Little Theorem */
 233     if (!BN_set_word(e, 2))
 234         goto err;
 235     if (!BN_sub(e, group->field, e))
 236         goto err;
 237     /*-
 238      * Exponent e is public.
 239      * No need for scatter-gather or BN_FLG_CONSTTIME.
 240      */
 241     if (!BN_mod_exp_mont(r, a, e, group->field, ctx, group->field_data1))
 242         goto err;
 243
 244     /* throw an error on zero */
 245     if (BN_is_zero(r)) {
 246         ECerr(EC_F_EC_GFP_MONT_FIELD_INV, EC_R_CANNOT_INVERT);
 247         goto err;
 248     }
 249
 250     ret = 1;
 251
 252   err:
 253     BN_CTX_end(ctx);
 254     BN_CTX_free(new_ctx);
 255     return ret;
 256 }
 257
 258 int ec_GFp_mont_field_encode(const EC_GROUP *group, BIGNUM *r,
 259                              const BIGNUM *a, BN_CTX *ctx)
 260 {
 261     if (group->field_data1 == NULL) {
 262         ECerr(EC_F_EC_GFP_MONT_FIELD_ENCODE, EC_R_NOT_INITIALIZED);
 263         return 0;
 264     }
 265
 266     return BN_to_montgomery(r, a, (BN_MONT_CTX *)group->field_data1, ctx);
 267 }
 268
 269 int ec_GFp_mont_field_decode(const EC_GROUP *group, BIGNUM *r,
 270                              const BIGNUM *a, BN_CTX *ctx)
 271 {
 272     if (group->field_data1 == NULL) {
 273         ECerr(EC_F_EC_GFP_MONT_FIELD_DECODE, EC_R_NOT_INITIALIZED);
 274         return 0;
 275     }
 276
 277     return BN_from_montgomery(r, a, group->field_data1, ctx);
 278 }
 279
 280 int ec_GFp_mont_field_set_to_one(const EC_GROUP *group, BIGNUM *r,
 281                                  BN_CTX *ctx)
 282 {
 283     if (group->field_data2 == NULL) {
 284         ECerr(EC_F_EC_GFP_MONT_FIELD_SET_TO_ONE, EC_R_NOT_INITIALIZED);
 285         return 0;
 286     }
 287
 288     if (!BN_copy(r, group->field_data2))
 289         return 0;
 290     return 1;
 291 }