+#define BN_BLINDING_COUNTER 32
+
+struct bn_blinding_st {
+ BIGNUM *A;
+ BIGNUM *Ai;
+ BIGNUM *e;
+ BIGNUM *mod; /* just a reference */
+ CRYPTO_THREAD_ID tid;
+ int counter;
+ unsigned long flags;
+ BN_MONT_CTX *m_ctx;
+ int (*bn_mod_exp) (BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+ const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
+ CRYPTO_RWLOCK *lock;
+};
+
+BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai, BIGNUM *mod)
+{
+ BN_BLINDING *ret = NULL;
+
+ bn_check_top(mod);
+
+ if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL)
+ return NULL;
+
+ ret->lock = CRYPTO_THREAD_lock_new();
+ if (ret->lock == NULL) {
+ ERR_raise(ERR_LIB_BN, ERR_R_CRYPTO_LIB);
+ OPENSSL_free(ret);
+ return NULL;
+ }
+
+ BN_BLINDING_set_current_thread(ret);
+
+ if (A != NULL) {
+ if ((ret->A = BN_dup(A)) == NULL)
+ goto err;
+ }
+
+ if (Ai != NULL) {
+ if ((ret->Ai = BN_dup(Ai)) == NULL)
+ goto err;
+ }
+
+ /* save a copy of mod in the BN_BLINDING structure */
+ if ((ret->mod = BN_dup(mod)) == NULL)
+ goto err;
+
+ if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
+ BN_set_flags(ret->mod, BN_FLG_CONSTTIME);
+
+ /*
+ * Set the counter to the special value -1 to indicate that this is
+ * never-used fresh blinding that does not need updating before first
+ * use.
+ */
+ ret->counter = -1;
+
+ return ret;
+
+ err:
+ BN_BLINDING_free(ret);
+ return NULL;
+}
+
+void BN_BLINDING_free(BN_BLINDING *r)
+{
+ if (r == NULL)
+ return;
+ BN_free(r->A);
+ BN_free(r->Ai);
+ BN_free(r->e);
+ BN_free(r->mod);
+ CRYPTO_THREAD_lock_free(r->lock);
+ OPENSSL_free(r);
+}
+
+int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
+{
+ int ret = 0;
+
+ if ((b->A == NULL) || (b->Ai == NULL)) {
+ ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
+ goto err;
+ }
+
+ if (b->counter == -1)
+ b->counter = 0;
+
+ if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL &&
+ !(b->flags & BN_BLINDING_NO_RECREATE)) {
+ /* re-create blinding parameters */
+ if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
+ goto err;
+ } else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
+ if (b->m_ctx != NULL) {
+ if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
+ || !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
+ goto err;
+ } else {
+ if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
+ || !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
+ goto err;
+ }
+ }
+
+ ret = 1;
+ err:
+ if (b->counter == BN_BLINDING_COUNTER)
+ b->counter = 0;
+ return ret;
+}
+
+int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
+{
+ return BN_BLINDING_convert_ex(n, NULL, b, ctx);
+}
+
+int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
+{
+ int ret = 1;
+
+ bn_check_top(n);
+
+ if ((b->A == NULL) || (b->Ai == NULL)) {
+ ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
+ return 0;
+ }
+
+ if (b->counter == -1)
+ /* Fresh blinding, doesn't need updating. */
+ b->counter = 0;
+ else if (!BN_BLINDING_update(b, ctx))
+ return 0;
+
+ if (r != NULL && (BN_copy(r, b->Ai) == NULL))
+ return 0;
+
+ if (b->m_ctx != NULL)
+ ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
+ else
+ ret = BN_mod_mul(n, n, b->A, b->mod, ctx);
+
+ return ret;
+}
+
+int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
+{
+ return BN_BLINDING_invert_ex(n, NULL, b, ctx);
+}
+
+int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
+ BN_CTX *ctx)
+{
+ int ret;
+
+ bn_check_top(n);
+
+ if (r == NULL && (r = b->Ai) == NULL) {
+ ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
+ return 0;
+ }
+
+ if (b->m_ctx != NULL) {
+ /* ensure that BN_mod_mul_montgomery takes pre-defined path */
+ if (n->dmax >= r->top) {
+ size_t i, rtop = r->top, ntop = n->top;
+ BN_ULONG mask;
+
+ for (i = 0; i < rtop; i++) {
+ mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
+ n->d[i] &= mask;
+ }
+ mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
+ /* always true, if (rtop >= ntop) n->top = r->top; */
+ n->top = (int)(rtop & ~mask) | (ntop & mask);
+ n->flags |= (BN_FLG_FIXED_TOP & ~mask);
+ }
+ ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx);
+ bn_correct_top_consttime(n);
+ } else {
+ ret = BN_mod_mul(n, n, r, b->mod, ctx);
+ }
+
+ bn_check_top(n);
+ return ret;
+}
+
+int BN_BLINDING_is_current_thread(BN_BLINDING *b)
+{
+ return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
+}
+
+void BN_BLINDING_set_current_thread(BN_BLINDING *b)
+{
+ b->tid = CRYPTO_THREAD_get_current_id();
+}
+
+int BN_BLINDING_lock(BN_BLINDING *b)
+{
+ return CRYPTO_THREAD_write_lock(b->lock);
+}
+
+int BN_BLINDING_unlock(BN_BLINDING *b)
+{
+ return CRYPTO_THREAD_unlock(b->lock);
+}
+
+unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
+{
+ return b->flags;
+}
+
+void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
+{
+ b->flags = flags;
+}
+
+BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
+ const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
+ int (*bn_mod_exp) (BIGNUM *r,
+ const BIGNUM *a,
+ const BIGNUM *p,
+ const BIGNUM *m,
+ BN_CTX *ctx,
+ BN_MONT_CTX *m_ctx),
+ BN_MONT_CTX *m_ctx)
+{
+ int retry_counter = 32;
+ BN_BLINDING *ret = NULL;
+
+ if (b == NULL)
+ ret = BN_BLINDING_new(NULL, NULL, m);
+ else
+ ret = b;
+
+ if (ret == NULL)
+ goto err;
+
+ if (ret->A == NULL && (ret->A = BN_new()) == NULL)
+ goto err;
+ if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
+ goto err;
+
+ if (e != NULL) {
+ BN_free(ret->e);
+ ret->e = BN_dup(e);
+ }
+ if (ret->e == NULL)
+ goto err;
+
+ if (bn_mod_exp != NULL)
+ ret->bn_mod_exp = bn_mod_exp;
+ if (m_ctx != NULL)
+ ret->m_ctx = m_ctx;
+
+ do {
+ int rv;
+ if (!BN_priv_rand_range_ex(ret->A, ret->mod, 0, ctx))
+ goto err;
+ if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
+ break;
+
+ /*
+ * this should almost never happen for good RSA keys
+ */
+ if (!rv)
+ goto err;
+
+ if (retry_counter-- == 0) {
+ ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
+ goto err;
+ }
+ } while (1);
+
+ if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
+ if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
+ goto err;
+ } else {
+ if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
+ goto err;
+ }
+
+ if (ret->m_ctx != NULL) {
+ if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
+ || !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
+ goto err;
+ }
+
+ return ret;
+ err:
+ if (b == NULL) {
+ BN_BLINDING_free(ret);
+ ret = NULL;
+ }
+
+ return ret;
+}