crypto/ec/ecp_mont.c

   1 /*
   2  * Copyright 2001-2018 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 #include <openssl/err.h>
  12
  13 #include "ec_lcl.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         ecdsa_simple_sign_setup,
  67         ecdsa_simple_sign_sig,
  68         ecdsa_simple_verify_sig,
  69         0, /* field_inverse_mod_ord */
  70         ec_GFp_simple_blind_coordinates,
  71         ec_GFp_simple_ladder_pre,
  72         ec_GFp_simple_ladder_step,
  73         ec_GFp_simple_ladder_post
  74     };
  75
  76     return &ret;
  77 }
  78
  79 int ec_GFp_mont_group_init(EC_GROUP *group)
  80 {
  81     int ok;
  82
  83     ok = ec_GFp_simple_group_init(group);
  84     group->field_data1 = NULL;
  85     group->field_data2 = NULL;
  86     return ok;
  87 }
  88
  89 void ec_GFp_mont_group_finish(EC_GROUP *group)
  90 {
  91     BN_MONT_CTX_free(group->field_data1);
  92     group->field_data1 = NULL;
  93     BN_free(group->field_data2);
  94     group->field_data2 = NULL;
  95     ec_GFp_simple_group_finish(group);
  96 }
  97
  98 void ec_GFp_mont_group_clear_finish(EC_GROUP *group)
  99 {
 100     BN_MONT_CTX_free(group->field_data1);
 101     group->field_data1 = NULL;
 102     BN_clear_free(group->field_data2);
 103     group->field_data2 = NULL;
 104     ec_GFp_simple_group_clear_finish(group);
 105 }
 106
 107 int ec_GFp_mont_group_copy(EC_GROUP *dest, const EC_GROUP *src)
 108 {
 109     BN_MONT_CTX_free(dest->field_data1);
 110     dest->field_data1 = NULL;
 111     BN_clear_free(dest->field_data2);
 112     dest->field_data2 = NULL;
 113
 114     if (!ec_GFp_simple_group_copy(dest, src))
 115         return 0;
 116
 117     if (src->field_data1 != NULL) {
 118         dest->field_data1 = BN_MONT_CTX_new();
 119         if (dest->field_data1 == NULL)
 120             return 0;
 121         if (!BN_MONT_CTX_copy(dest->field_data1, src->field_data1))
 122             goto err;
 123     }
 124     if (src->field_data2 != NULL) {
 125         dest->field_data2 = BN_dup(src->field_data2);
 126         if (dest->field_data2 == NULL)
 127             goto err;
 128     }
 129
 130     return 1;
 131
 132  err:
 133     BN_MONT_CTX_free(dest->field_data1);
 134     dest->field_data1 = NULL;
 135     return 0;
 136 }
 137
 138 int ec_GFp_mont_group_set_curve(EC_GROUP *group, const BIGNUM *p,
 139                                 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
 140 {
 141     BN_CTX *new_ctx = NULL;
 142     BN_MONT_CTX *mont = NULL;
 143     BIGNUM *one = NULL;
 144     int ret = 0;
 145
 146     BN_MONT_CTX_free(group->field_data1);
 147     group->field_data1 = NULL;
 148     BN_free(group->field_data2);
 149     group->field_data2 = NULL;
 150
 151     if (ctx == NULL) {
 152         ctx = new_ctx = BN_CTX_new_ex(group->libctx);
 153         if (ctx == NULL)
 154             return 0;
 155     }
 156
 157     mont = BN_MONT_CTX_new();
 158     if (mont == NULL)
 159         goto err;
 160     if (!BN_MONT_CTX_set(mont, p, ctx)) {
 161         ECerr(EC_F_EC_GFP_MONT_GROUP_SET_CURVE, ERR_R_BN_LIB);
 162         goto err;
 163     }
 164     one = BN_new();
 165     if (one == NULL)
 166         goto err;
 167     if (!BN_to_montgomery(one, BN_value_one(), mont, ctx))
 168         goto err;
 169
 170     group->field_data1 = mont;
 171     mont = NULL;
 172     group->field_data2 = one;
 173     one = NULL;
 174
 175     ret = ec_GFp_simple_group_set_curve(group, p, a, b, ctx);
 176
 177     if (!ret) {
 178         BN_MONT_CTX_free(group->field_data1);
 179         group->field_data1 = NULL;
 180         BN_free(group->field_data2);
 181         group->field_data2 = NULL;
 182     }
 183
 184  err:
 185     BN_free(one);
 186     BN_CTX_free(new_ctx);
 187     BN_MONT_CTX_free(mont);
 188     return ret;
 189 }
 190
 191 int ec_GFp_mont_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
 192                           const BIGNUM *b, BN_CTX *ctx)
 193 {
 194     if (group->field_data1 == NULL) {
 195         ECerr(EC_F_EC_GFP_MONT_FIELD_MUL, EC_R_NOT_INITIALIZED);
 196         return 0;
 197     }
 198
 199     return BN_mod_mul_montgomery(r, a, b, group->field_data1, ctx);
 200 }
 201
 202 int ec_GFp_mont_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
 203                           BN_CTX *ctx)
 204 {
 205     if (group->field_data1 == NULL) {
 206         ECerr(EC_F_EC_GFP_MONT_FIELD_SQR, EC_R_NOT_INITIALIZED);
 207         return 0;
 208     }
 209
 210     return BN_mod_mul_montgomery(r, a, a, group->field_data1, ctx);
 211 }
 212
 213 /*-
 214  * Computes the multiplicative inverse of a in GF(p), storing the result in r.
 215  * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error.
 216  * We have a Mont structure, so SCA hardening is FLT inversion.
 217  */
 218 int ec_GFp_mont_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
 219                             BN_CTX *ctx)
 220 {
 221     BIGNUM *e = NULL;
 222     BN_CTX *new_ctx = NULL;
 223     int ret = 0;
 224
 225     if (group->field_data1 == NULL)
 226         return 0;
 227
 228     if (ctx == NULL
 229             && (ctx = new_ctx = BN_CTX_secure_new_ex(group->libctx)) == NULL)
 230         return 0;
 231
 232     BN_CTX_start(ctx);
 233     if ((e = BN_CTX_get(ctx)) == NULL)
 234         goto err;
 235
 236     /* Inverse in constant time with Fermats Little Theorem */
 237     if (!BN_set_word(e, 2))
 238         goto err;
 239     if (!BN_sub(e, group->field, e))
 240         goto err;
 241     /*-
 242      * Exponent e is public.
 243      * No need for scatter-gather or BN_FLG_CONSTTIME.
 244      */
 245     if (!BN_mod_exp_mont(r, a, e, group->field, ctx, group->field_data1))
 246         goto err;
 247
 248     /* throw an error on zero */
 249     if (BN_is_zero(r)) {
 250         ECerr(EC_F_EC_GFP_MONT_FIELD_INV, EC_R_CANNOT_INVERT);
 251         goto err;
 252     }
 253
 254     ret = 1;
 255
 256   err:
 257     BN_CTX_end(ctx);
 258     BN_CTX_free(new_ctx);
 259     return ret;
 260 }
 261
 262 int ec_GFp_mont_field_encode(const EC_GROUP *group, BIGNUM *r,
 263                              const BIGNUM *a, BN_CTX *ctx)
 264 {
 265     if (group->field_data1 == NULL) {
 266         ECerr(EC_F_EC_GFP_MONT_FIELD_ENCODE, EC_R_NOT_INITIALIZED);
 267         return 0;
 268     }
 269
 270     return BN_to_montgomery(r, a, (BN_MONT_CTX *)group->field_data1, ctx);
 271 }
 272
 273 int ec_GFp_mont_field_decode(const EC_GROUP *group, BIGNUM *r,
 274                              const BIGNUM *a, BN_CTX *ctx)
 275 {
 276     if (group->field_data1 == NULL) {
 277         ECerr(EC_F_EC_GFP_MONT_FIELD_DECODE, EC_R_NOT_INITIALIZED);
 278         return 0;
 279     }
 280
 281     return BN_from_montgomery(r, a, group->field_data1, ctx);
 282 }
 283
 284 int ec_GFp_mont_field_set_to_one(const EC_GROUP *group, BIGNUM *r,
 285                                  BN_CTX *ctx)
 286 {
 287     if (group->field_data2 == NULL) {
 288         ECerr(EC_F_EC_GFP_MONT_FIELD_SET_TO_ONE, EC_R_NOT_INITIALIZED);
 289         return 0;
 290     }
 291
 292     if (!BN_copy(r, group->field_data2))
 293         return 0;
 294     return 1;
 295 }