crypto/bn/bn_blind.c

   1 /*
   2  * Copyright 1998-2023 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_local.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         return NULL;
  38
  39     ret->lock = CRYPTO_THREAD_lock_new();
  40     if (ret->lock == NULL) {
  41         ERR_raise(ERR_LIB_BN, ERR_R_CRYPTO_LIB);
  42         OPENSSL_free(ret);
  43         return NULL;
  44     }
  45
  46     BN_BLINDING_set_current_thread(ret);
  47
  48     if (A != NULL) {
  49         if ((ret->A = BN_dup(A)) == NULL)
  50             goto err;
  51     }
  52
  53     if (Ai != NULL) {
  54         if ((ret->Ai = BN_dup(Ai)) == NULL)
  55             goto err;
  56     }
  57
  58     /* save a copy of mod in the BN_BLINDING structure */
  59     if ((ret->mod = BN_dup(mod)) == NULL)
  60         goto err;
  61
  62     if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
  63         BN_set_flags(ret->mod, BN_FLG_CONSTTIME);
  64
  65     /*
  66      * Set the counter to the special value -1 to indicate that this is
  67      * never-used fresh blinding that does not need updating before first
  68      * use.
  69      */
  70     ret->counter = -1;
  71
  72     return ret;
  73
  74  err:
  75     BN_BLINDING_free(ret);
  76     return NULL;
  77 }
  78
  79 void BN_BLINDING_free(BN_BLINDING *r)
  80 {
  81     if (r == NULL)
  82         return;
  83     BN_free(r->A);
  84     BN_free(r->Ai);
  85     BN_free(r->e);
  86     BN_free(r->mod);
  87     CRYPTO_THREAD_lock_free(r->lock);
  88     OPENSSL_free(r);
  89 }
  90
  91 int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
  92 {
  93     int ret = 0;
  94
  95     if ((b->A == NULL) || (b->Ai == NULL)) {
  96         ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
  97         goto err;
  98     }
  99
 100     if (b->counter == -1)
 101         b->counter = 0;
 102
 103     if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL &&
 104         !(b->flags & BN_BLINDING_NO_RECREATE)) {
 105         /* re-create blinding parameters */
 106         if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
 107             goto err;
 108     } else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
 109         if (b->m_ctx != NULL) {
 110             if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
 111                 || !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
 112                 goto err;
 113         } else {
 114             if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
 115                 || !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
 116                 goto err;
 117         }
 118     }
 119
 120     ret = 1;
 121  err:
 122     if (b->counter == BN_BLINDING_COUNTER)
 123         b->counter = 0;
 124     return ret;
 125 }
 126
 127 int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
 128 {
 129     return BN_BLINDING_convert_ex(n, NULL, b, ctx);
 130 }
 131
 132 int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
 133 {
 134     int ret = 1;
 135
 136     bn_check_top(n);
 137
 138     if ((b->A == NULL) || (b->Ai == NULL)) {
 139         ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
 140         return 0;
 141     }
 142
 143     if (b->counter == -1)
 144         /* Fresh blinding, doesn't need updating. */
 145         b->counter = 0;
 146     else if (!BN_BLINDING_update(b, ctx))
 147         return 0;
 148
 149     if (r != NULL && (BN_copy(r, b->Ai) == NULL))
 150         return 0;
 151
 152     if (b->m_ctx != NULL)
 153         ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
 154     else
 155         ret = BN_mod_mul(n, n, b->A, b->mod, ctx);
 156
 157     return ret;
 158 }
 159
 160 int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
 161 {
 162     return BN_BLINDING_invert_ex(n, NULL, b, ctx);
 163 }
 164
 165 int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
 166                           BN_CTX *ctx)
 167 {
 168     int ret;
 169
 170     bn_check_top(n);
 171
 172     if (r == NULL && (r = b->Ai) == NULL) {
 173         ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
 174         return 0;
 175     }
 176
 177     if (b->m_ctx != NULL) {
 178         /* ensure that BN_mod_mul_montgomery takes pre-defined path */
 179         if (n->dmax >= r->top) {
 180             size_t i, rtop = r->top, ntop = n->top;
 181             BN_ULONG mask;
 182
 183             for (i = 0; i < rtop; i++) {
 184                 mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
 185                 n->d[i] &= mask;
 186             }
 187             mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
 188             /* always true, if (rtop >= ntop) n->top = r->top; */
 189             n->top = (int)(rtop & ~mask) | (ntop & mask);
 190             n->flags |= (BN_FLG_FIXED_TOP & ~mask);
 191         }
 192         ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx);
 193         bn_correct_top_consttime(n);
 194     } else {
 195         ret = BN_mod_mul(n, n, r, b->mod, ctx);
 196     }
 197
 198     bn_check_top(n);
 199     return ret;
 200 }
 201
 202 int BN_BLINDING_is_current_thread(BN_BLINDING *b)
 203 {
 204     return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
 205 }
 206
 207 void BN_BLINDING_set_current_thread(BN_BLINDING *b)
 208 {
 209     b->tid = CRYPTO_THREAD_get_current_id();
 210 }
 211
 212 int BN_BLINDING_lock(BN_BLINDING *b)
 213 {
 214     return CRYPTO_THREAD_write_lock(b->lock);
 215 }
 216
 217 int BN_BLINDING_unlock(BN_BLINDING *b)
 218 {
 219     return CRYPTO_THREAD_unlock(b->lock);
 220 }
 221
 222 unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
 223 {
 224     return b->flags;
 225 }
 226
 227 void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
 228 {
 229     b->flags = flags;
 230 }
 231
 232 BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
 233                                       const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
 234                                       int (*bn_mod_exp) (BIGNUM *r,
 235                                                          const BIGNUM *a,
 236                                                          const BIGNUM *p,
 237                                                          const BIGNUM *m,
 238                                                          BN_CTX *ctx,
 239                                                          BN_MONT_CTX *m_ctx),
 240                                       BN_MONT_CTX *m_ctx)
 241 {
 242     int retry_counter = 32;
 243     BN_BLINDING *ret = NULL;
 244
 245     if (b == NULL)
 246         ret = BN_BLINDING_new(NULL, NULL, m);
 247     else
 248         ret = b;
 249
 250     if (ret == NULL)
 251         goto err;
 252
 253     if (ret->A == NULL && (ret->A = BN_new()) == NULL)
 254         goto err;
 255     if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
 256         goto err;
 257
 258     if (e != NULL) {
 259         BN_free(ret->e);
 260         ret->e = BN_dup(e);
 261     }
 262     if (ret->e == NULL)
 263         goto err;
 264
 265     if (bn_mod_exp != NULL)
 266         ret->bn_mod_exp = bn_mod_exp;
 267     if (m_ctx != NULL)
 268         ret->m_ctx = m_ctx;
 269
 270     do {
 271         int rv;
 272         if (!BN_priv_rand_range_ex(ret->A, ret->mod, 0, ctx))
 273             goto err;
 274         if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
 275             break;
 276
 277         /*
 278          * this should almost never happen for good RSA keys
 279          */
 280         if (!rv)
 281             goto err;
 282
 283         if (retry_counter-- == 0) {
 284             ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
 285             goto err;
 286         }
 287     } while (1);
 288
 289     if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
 290         if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
 291             goto err;
 292     } else {
 293         if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
 294             goto err;
 295     }
 296
 297     if (ret->m_ctx != NULL) {
 298         if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
 299             || !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
 300             goto err;
 301     }
 302
 303     return ret;
 304  err:
 305     if (b == NULL) {
 306         BN_BLINDING_free(ret);
 307         ret = NULL;
 308     }
 309
 310     return ret;
 311 }