crypto/bn/bn_blind.c

   1 /*
   2  * Copyright 1998-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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 (b->m_ctx != NULL) {
 112             if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
 113                 || !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
 114                 goto err;
 115         } else {
 116             if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
 117                 || !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
 118                 goto err;
 119         }
 120     }
 121
 122     ret = 1;
 123  err:
 124     if (b->counter == BN_BLINDING_COUNTER)
 125         b->counter = 0;
 126     return ret;
 127 }
 128
 129 int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
 130 {
 131     return BN_BLINDING_convert_ex(n, NULL, b, ctx);
 132 }
 133
 134 int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
 135 {
 136     int ret = 1;
 137
 138     bn_check_top(n);
 139
 140     if ((b->A == NULL) || (b->Ai == NULL)) {
 141         BNerr(BN_F_BN_BLINDING_CONVERT_EX, BN_R_NOT_INITIALIZED);
 142         return 0;
 143     }
 144
 145     if (b->counter == -1)
 146         /* Fresh blinding, doesn't need updating. */
 147         b->counter = 0;
 148     else if (!BN_BLINDING_update(b, ctx))
 149         return 0;
 150
 151     if (r != NULL && (BN_copy(r, b->Ai) == NULL))
 152         return 0;
 153
 154     if (b->m_ctx != NULL)
 155         ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
 156     else
 157         ret = BN_mod_mul(n, n, b->A, b->mod, ctx);
 158
 159     return ret;
 160 }
 161
 162 int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
 163 {
 164     return BN_BLINDING_invert_ex(n, NULL, b, ctx);
 165 }
 166
 167 int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
 168                           BN_CTX *ctx)
 169 {
 170     int ret;
 171
 172     bn_check_top(n);
 173
 174     if (r == NULL && (r = b->Ai) == NULL) {
 175         BNerr(BN_F_BN_BLINDING_INVERT_EX, BN_R_NOT_INITIALIZED);
 176         return 0;
 177     }
 178
 179     if (b->m_ctx != NULL) {
 180         /* ensure that BN_mod_mul_montgomery takes pre-defined path */
 181         if (n->dmax >= r->top) {
 182             size_t i, rtop = r->top, ntop = n->top;
 183             BN_ULONG mask;
 184
 185             for (i = 0; i < rtop; i++) {
 186                 mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
 187                 n->d[i] &= mask;
 188             }
 189             mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
 190             /* always true, if (rtop >= ntop) n->top = r->top; */
 191             n->top = (int)(rtop & ~mask) | (ntop & mask);
 192             n->flags |= (BN_FLG_FIXED_TOP & ~mask);
 193         }
 194         ret = BN_mod_mul_montgomery(n, n, r, b->m_ctx, ctx);
 195     } else {
 196         ret = BN_mod_mul(n, n, r, b->mod, ctx);
 197     }
 198
 199     bn_check_top(n);
 200     return ret;
 201 }
 202
 203 int BN_BLINDING_is_current_thread(BN_BLINDING *b)
 204 {
 205     return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
 206 }
 207
 208 void BN_BLINDING_set_current_thread(BN_BLINDING *b)
 209 {
 210     b->tid = CRYPTO_THREAD_get_current_id();
 211 }
 212
 213 int BN_BLINDING_lock(BN_BLINDING *b)
 214 {
 215     return CRYPTO_THREAD_write_lock(b->lock);
 216 }
 217
 218 int BN_BLINDING_unlock(BN_BLINDING *b)
 219 {
 220     return CRYPTO_THREAD_unlock(b->lock);
 221 }
 222
 223 unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
 224 {
 225     return b->flags;
 226 }
 227
 228 void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
 229 {
 230     b->flags = flags;
 231 }
 232
 233 BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
 234                                       const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
 235                                       int (*bn_mod_exp) (BIGNUM *r,
 236                                                          const BIGNUM *a,
 237                                                          const BIGNUM *p,
 238                                                          const BIGNUM *m,
 239                                                          BN_CTX *ctx,
 240                                                          BN_MONT_CTX *m_ctx),
 241                                       BN_MONT_CTX *m_ctx)
 242 {
 243     int retry_counter = 32;
 244     BN_BLINDING *ret = NULL;
 245
 246     if (b == NULL)
 247         ret = BN_BLINDING_new(NULL, NULL, m);
 248     else
 249         ret = b;
 250
 251     if (ret == NULL)
 252         goto err;
 253
 254     if (ret->A == NULL && (ret->A = BN_new()) == NULL)
 255         goto err;
 256     if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
 257         goto err;
 258
 259     if (e != NULL) {
 260         BN_free(ret->e);
 261         ret->e = BN_dup(e);
 262     }
 263     if (ret->e == NULL)
 264         goto err;
 265
 266     if (bn_mod_exp != NULL)
 267         ret->bn_mod_exp = bn_mod_exp;
 268     if (m_ctx != NULL)
 269         ret->m_ctx = m_ctx;
 270
 271     do {
 272         int rv;
 273         if (!BN_priv_rand_range_ex(ret->A, ret->mod, ctx))
 274             goto err;
 275         if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
 276             break;
 277
 278         /*
 279          * this should almost never happen for good RSA keys
 280          */
 281         if (!rv)
 282             goto err;
 283
 284         if (retry_counter-- == 0) {
 285             BNerr(BN_F_BN_BLINDING_CREATE_PARAM, BN_R_TOO_MANY_ITERATIONS);
 286             goto err;
 287         }
 288     } while (1);
 289
 290     if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
 291         if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
 292             goto err;
 293     } else {
 294         if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
 295             goto err;
 296     }
 297
 298     if (ret->m_ctx != NULL) {
 299         if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
 300             || !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
 301             goto err;
 302     }
 303
 304     return ret;
 305  err:
 306     if (b == NULL) {
 307         BN_BLINDING_free(ret);
 308         ret = NULL;
 309     }
 310
 311     return ret;
 312 }