crypto/bn/bn_blind.c

   1 /*
   2  * Copyright 1998-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <openssl/opensslconf.h>
  11 #include "internal/cryptlib.h"
  12 #include "bn_lcl.h"
  13
  14 #define BN_BLINDING_COUNTER     32
  15
  16 struct bn_blinding_st {
  17     BIGNUM *A;
  18     BIGNUM *Ai;
  19     BIGNUM *e;
  20     BIGNUM *mod;                /* just a reference */
  21     CRYPTO_THREAD_ID tid;
  22     int counter;
  23     unsigned long flags;
  24     BN_MONT_CTX *m_ctx;
  25     int (*bn_mod_exp) (BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
  26                        const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
  27     CRYPTO_RWLOCK *lock;
  28 };
  29
  30 BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai, BIGNUM *mod)
  31 {
  32     BN_BLINDING *ret = NULL;
  33
  34     bn_check_top(mod);
  35
  36     if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
  37         BNerr(BN_F_BN_BLINDING_NEW, ERR_R_MALLOC_FAILURE);
  38         return NULL;
  39     }
  40
  41     ret->lock = CRYPTO_THREAD_lock_new();
  42     if (ret->lock == NULL) {
  43         BNerr(BN_F_BN_BLINDING_NEW, ERR_R_MALLOC_FAILURE);
  44         OPENSSL_free(ret);
  45         return NULL;
  46     }
  47
  48     BN_BLINDING_set_current_thread(ret);
  49
  50     if (A != NULL) {
  51         if ((ret->A = BN_dup(A)) == NULL)
  52             goto err;
  53     }
  54
  55     if (Ai != NULL) {
  56         if ((ret->Ai = BN_dup(Ai)) == NULL)
  57             goto err;
  58     }
  59
  60     /* save a copy of mod in the BN_BLINDING structure */
  61     if ((ret->mod = BN_dup(mod)) == NULL)
  62         goto err;
  63
  64     if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
  65         BN_set_flags(ret->mod, BN_FLG_CONSTTIME);
  66
  67     /*
  68      * Set the counter to the special value -1 to indicate that this is
  69      * never-used fresh blinding that does not need updating before first
  70      * use.
  71      */
  72     ret->counter = -1;
  73
  74     return ret;
  75
  76  err:
  77     BN_BLINDING_free(ret);
  78     return NULL;
  79 }
  80
  81 void BN_BLINDING_free(BN_BLINDING *r)
  82 {
  83     if (r == NULL)
  84         return;
  85     BN_free(r->A);
  86     BN_free(r->Ai);
  87     BN_free(r->e);
  88     BN_free(r->mod);
  89     CRYPTO_THREAD_lock_free(r->lock);
  90     OPENSSL_free(r);
  91 }
  92
  93 int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
  94 {
  95     int ret = 0;
  96
  97     if ((b->A == NULL) || (b->Ai == NULL)) {
  98         BNerr(BN_F_BN_BLINDING_UPDATE, BN_R_NOT_INITIALIZED);
  99         goto err;
 100     }
 101
 102     if (b->counter == -1)
 103         b->counter = 0;
 104
 105     if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL &&
 106         !(b->flags & BN_BLINDING_NO_RECREATE)) {
 107         /* re-create blinding parameters */
 108         if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
 109             goto err;
 110     } else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
 111         if (!BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
 112             goto err;
 113         if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx))
 114             goto err;
 115     }
 116
 117     ret = 1;
 118  err:
 119     if (b->counter == BN_BLINDING_COUNTER)
 120         b->counter = 0;
 121     return ret;
 122 }
 123
 124 int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
 125 {
 126     return BN_BLINDING_convert_ex(n, NULL, b, ctx);
 127 }
 128
 129 int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
 130 {
 131     int ret = 1;
 132
 133     bn_check_top(n);
 134
 135     if ((b->A == NULL) || (b->Ai == NULL)) {
 136         BNerr(BN_F_BN_BLINDING_CONVERT_EX, BN_R_NOT_INITIALIZED);
 137         return 0;
 138     }
 139
 140     if (b->counter == -1)
 141         /* Fresh blinding, doesn't need updating. */
 142         b->counter = 0;
 143     else if (!BN_BLINDING_update(b, ctx))
 144         return 0;
 145
 146     if (r != NULL) {
 147         if (!BN_copy(r, b->Ai))
 148             ret = 0;
 149     }
 150
 151     if (!BN_mod_mul(n, n, b->A, b->mod, ctx))
 152         ret = 0;
 153
 154     return ret;
 155 }
 156
 157 int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
 158 {
 159     return BN_BLINDING_invert_ex(n, NULL, b, ctx);
 160 }
 161
 162 int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
 163                           BN_CTX *ctx)
 164 {
 165     int ret;
 166
 167     bn_check_top(n);
 168
 169     if (r != NULL)
 170         ret = BN_mod_mul(n, n, r, b->mod, ctx);
 171     else {
 172         if (b->Ai == NULL) {
 173             BNerr(BN_F_BN_BLINDING_INVERT_EX, BN_R_NOT_INITIALIZED);
 174             return 0;
 175         }
 176         ret = BN_mod_mul(n, n, b->Ai, b->mod, ctx);
 177     }
 178
 179     bn_check_top(n);
 180     return ret;
 181 }
 182
 183 int BN_BLINDING_is_current_thread(BN_BLINDING *b)
 184 {
 185     return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
 186 }
 187
 188 void BN_BLINDING_set_current_thread(BN_BLINDING *b)
 189 {
 190     b->tid = CRYPTO_THREAD_get_current_id();
 191 }
 192
 193 int BN_BLINDING_lock(BN_BLINDING *b)
 194 {
 195     return CRYPTO_THREAD_write_lock(b->lock);
 196 }
 197
 198 int BN_BLINDING_unlock(BN_BLINDING *b)
 199 {
 200     return CRYPTO_THREAD_unlock(b->lock);
 201 }
 202
 203 unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
 204 {
 205     return b->flags;
 206 }
 207
 208 void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
 209 {
 210     b->flags = flags;
 211 }
 212
 213 BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
 214                                       const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
 215                                       int (*bn_mod_exp) (BIGNUM *r,
 216                                                          const BIGNUM *a,
 217                                                          const BIGNUM *p,
 218                                                          const BIGNUM *m,
 219                                                          BN_CTX *ctx,
 220                                                          BN_MONT_CTX *m_ctx),
 221                                       BN_MONT_CTX *m_ctx)
 222 {
 223     int retry_counter = 32;
 224     BN_BLINDING *ret = NULL;
 225
 226     if (b == NULL)
 227         ret = BN_BLINDING_new(NULL, NULL, m);
 228     else
 229         ret = b;
 230
 231     if (ret == NULL)
 232         goto err;
 233
 234     if (ret->A == NULL && (ret->A = BN_new()) == NULL)
 235         goto err;
 236     if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
 237         goto err;
 238
 239     if (e != NULL) {
 240         BN_free(ret->e);
 241         ret->e = BN_dup(e);
 242     }
 243     if (ret->e == NULL)
 244         goto err;
 245
 246     if (bn_mod_exp != NULL)
 247         ret->bn_mod_exp = bn_mod_exp;
 248     if (m_ctx != NULL)
 249         ret->m_ctx = m_ctx;
 250
 251     do {
 252         int rv;
 253         if (!BN_rand_range(ret->A, ret->mod))
 254             goto err;
 255         if (!int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv)) {
 256             /*
 257              * this should almost never happen for good RSA keys
 258              */
 259             if (rv) {
 260                 if (retry_counter-- == 0) {
 261                     BNerr(BN_F_BN_BLINDING_CREATE_PARAM,
 262                           BN_R_TOO_MANY_ITERATIONS);
 263                     goto err;
 264                 }
 265             } else
 266                 goto err;
 267         } else
 268             break;
 269     } while (1);
 270
 271     if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
 272         if (!ret->bn_mod_exp
 273             (ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
 274             goto err;
 275     } else {
 276         if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
 277             goto err;
 278     }
 279
 280     return ret;
 281  err:
 282     if (b == NULL) {
 283         BN_BLINDING_free(ret);
 284         ret = NULL;
 285     }
 286
 287     return ret;
 288 }