-/* crypto/bn/bn_mod.c */
-/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
- * All rights reserved.
+/*
+ * Copyright 1998-2018 The OpenSSL Project Authors. All Rights Reserved.
*
- * This package is an SSL implementation written
- * by Eric Young (eay@cryptsoft.com).
- * The implementation was written so as to conform with Netscapes SSL.
- *
- * This library is free for commercial and non-commercial use as long as
- * the following conditions are aheared to. The following conditions
- * apply to all code found in this distribution, be it the RC4, RSA,
- * lhash, DES, etc., code; not just the SSL code. The SSL documentation
- * included with this distribution is covered by the same copyright terms
- * except that the holder is Tim Hudson (tjh@cryptsoft.com).
- *
- * Copyright remains Eric Young's, and as such any Copyright notices in
- * the code are not to be removed.
- * If this package is used in a product, Eric Young should be given attribution
- * as the author of the parts of the library used.
- * This can be in the form of a textual message at program startup or
- * in documentation (online or textual) provided with the package.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- * "This product includes cryptographic software written by
- * Eric Young (eay@cryptsoft.com)"
- * The word 'cryptographic' can be left out if the rouines from the library
- * being used are not cryptographic related :-).
- * 4. If you include any Windows specific code (or a derivative thereof) from
- * the apps directory (application code) you must include an acknowledgement:
- * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
- *
- * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- * The licence and distribution terms for any publically available version or
- * derivative of this code cannot be changed. i.e. this code cannot simply be
- * copied and put under another distribution licence
- * [including the GNU Public Licence.]
+ * Licensed under the Apache License 2.0 (the "License"). You may not use
+ * this file except in compliance with the License. You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
*/
-#include <stdio.h>
-#include "cryptlib.h"
+#include "internal/cryptlib.h"
#include "bn_lcl.h"
-/* rem != m */
-int BN_mod(rem, m, d,ctx)
-BIGNUM *rem;
-BIGNUM *m;
-BIGNUM *d;
-BN_CTX *ctx;
- {
-#if 0 /* The old slow way */
- int i,nm,nd;
- BIGNUM *dv;
-
- if (BN_ucmp(m,d) < 0)
- return((BN_copy(rem,m) == NULL)?0:1);
-
- dv=ctx->bn[ctx->tos];
-
- if (!BN_copy(rem,m)) return(0);
-
- nm=BN_num_bits(rem);
- nd=BN_num_bits(d);
- if (!BN_lshift(dv,d,nm-nd)) return(0);
- for (i=nm-nd; i>=0; i--)
- {
- if (BN_cmp(rem,dv) >= 0)
- {
- if (!BN_sub(rem,rem,dv)) return(0);
- }
- if (!BN_rshift1(dv,dv)) return(0);
- }
- return(1);
-#else
- return(BN_div(NULL,rem,m,d,ctx));
-#endif
- }
+int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
+{
+ /*
+ * like BN_mod, but returns non-negative remainder (i.e., 0 <= r < |d|
+ * always holds)
+ */
+ if (!(BN_mod(r, m, d, ctx)))
+ return 0;
+ if (!r->neg)
+ return 1;
+ /* now -|d| < r < 0, so we have to set r := r + |d| */
+ return (d->neg ? BN_sub : BN_add) (r, r, d);
+}
+
+int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
+ BN_CTX *ctx)
+{
+ if (!BN_add(r, a, b))
+ return 0;
+ return BN_nnmod(r, r, m, ctx);
+}
+
+/*
+ * BN_mod_add variant that may be used if both a and b are non-negative and
+ * less than m. The original algorithm was
+ *
+ * if (!BN_uadd(r, a, b))
+ * return 0;
+ * if (BN_ucmp(r, m) >= 0)
+ * return BN_usub(r, r, m);
+ *
+ * which is replaced with addition, subtracting modulus, and conditional
+ * move depending on whether or not subtraction borrowed.
+ */
+int bn_mod_add_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
+ const BIGNUM *m)
+{
+ size_t i, ai, bi, mtop = m->top;
+ BN_ULONG storage[1024 / BN_BITS2];
+ BN_ULONG carry, temp, mask, *rp, *tp = storage;
+ const BN_ULONG *ap, *bp;
+
+ if (bn_wexpand(r, mtop) == NULL)
+ return 0;
+
+ if (mtop > sizeof(storage) / sizeof(storage[0])
+ && (tp = OPENSSL_malloc(mtop * sizeof(BN_ULONG))) == NULL)
+ return 0;
+
+ ap = a->d != NULL ? a->d : tp;
+ bp = b->d != NULL ? b->d : tp;
+
+ for (i = 0, ai = 0, bi = 0, carry = 0; i < mtop;) {
+ mask = (BN_ULONG)0 - ((i - a->top) >> (8 * sizeof(i) - 1));
+ temp = ((ap[ai] & mask) + carry) & BN_MASK2;
+ carry = (temp < carry);
+
+ mask = (BN_ULONG)0 - ((i - b->top) >> (8 * sizeof(i) - 1));
+ tp[i] = ((bp[bi] & mask) + temp) & BN_MASK2;
+ carry += (tp[i] < temp);
+
+ i++;
+ ai += (i - a->dmax) >> (8 * sizeof(i) - 1);
+ bi += (i - b->dmax) >> (8 * sizeof(i) - 1);
+ }
+ rp = r->d;
+ carry -= bn_sub_words(rp, tp, m->d, mtop);
+ for (i = 0; i < mtop; i++) {
+ rp[i] = (carry & tp[i]) | (~carry & rp[i]);
+ ((volatile BN_ULONG *)tp)[i] = 0;
+ }
+ r->top = mtop;
+ r->flags |= BN_FLG_FIXED_TOP;
+ r->neg = 0;
+
+ if (tp != storage)
+ OPENSSL_free(tp);
+
+ return 1;
+}
+
+int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
+ const BIGNUM *m)
+{
+ int ret = bn_mod_add_fixed_top(r, a, b, m);
+
+ if (ret)
+ bn_correct_top(r);
+
+ return ret;
+}
+
+int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
+ BN_CTX *ctx)
+{
+ if (!BN_sub(r, a, b))
+ return 0;
+ return BN_nnmod(r, r, m, ctx);
+}
+
+/*
+ * BN_mod_sub variant that may be used if both a and b are non-negative,
+ * a is less than m, while b is of same bit width as m. It's implemented
+ * as subtraction followed by two conditional additions.
+ *
+ * 0 <= a < m
+ * 0 <= b < 2^w < 2*m
+ *
+ * after subtraction
+ *
+ * -2*m < r = a - b < m
+ *
+ * Thus it takes up to two conditional additions to make |r| positive.
+ */
+int bn_mod_sub_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
+ const BIGNUM *m)
+{
+ size_t i, ai, bi, mtop = m->top;
+ BN_ULONG borrow, carry, ta, tb, mask, *rp;
+ const BN_ULONG *ap, *bp;
+
+ if (bn_wexpand(r, mtop) == NULL)
+ return 0;
+
+ rp = r->d;
+ ap = a->d != NULL ? a->d : rp;
+ bp = b->d != NULL ? b->d : rp;
+
+ for (i = 0, ai = 0, bi = 0, borrow = 0; i < mtop;) {
+ mask = (BN_ULONG)0 - ((i - a->top) >> (8 * sizeof(i) - 1));
+ ta = ap[ai] & mask;
+
+ mask = (BN_ULONG)0 - ((i - b->top) >> (8 * sizeof(i) - 1));
+ tb = bp[bi] & mask;
+ rp[i] = ta - tb - borrow;
+ if (ta != tb)
+ borrow = (ta < tb);
+
+ i++;
+ ai += (i - a->dmax) >> (8 * sizeof(i) - 1);
+ bi += (i - b->dmax) >> (8 * sizeof(i) - 1);
+ }
+ ap = m->d;
+ for (i = 0, mask = 0 - borrow, carry = 0; i < mtop; i++) {
+ ta = ((ap[i] & mask) + carry) & BN_MASK2;
+ carry = (ta < carry);
+ rp[i] = (rp[i] + ta) & BN_MASK2;
+ carry += (rp[i] < ta);
+ }
+ borrow -= carry;
+ for (i = 0, mask = 0 - borrow, carry = 0; i < mtop; i++) {
+ ta = ((ap[i] & mask) + carry) & BN_MASK2;
+ carry = (ta < carry);
+ rp[i] = (rp[i] + ta) & BN_MASK2;
+ carry += (rp[i] < ta);
+ }
+
+ r->top = mtop;
+ r->flags |= BN_FLG_FIXED_TOP;
+ r->neg = 0;
+
+ return 1;
+}
+
+/*
+ * BN_mod_sub variant that may be used if both a and b are non-negative and
+ * less than m
+ */
+int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
+ const BIGNUM *m)
+{
+ if (!BN_sub(r, a, b))
+ return 0;
+ if (r->neg)
+ return BN_add(r, r, m);
+ return 1;
+}
+
+/* slow but works */
+int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
+ BN_CTX *ctx)
+{
+ BIGNUM *t;
+ int ret = 0;
+
+ bn_check_top(a);
+ bn_check_top(b);
+ bn_check_top(m);
+
+ BN_CTX_start(ctx);
+ if ((t = BN_CTX_get(ctx)) == NULL)
+ goto err;
+ if (a == b) {
+ if (!BN_sqr(t, a, ctx))
+ goto err;
+ } else {
+ if (!BN_mul(t, a, b, ctx))
+ goto err;
+ }
+ if (!BN_nnmod(r, t, m, ctx))
+ goto err;
+ bn_check_top(r);
+ ret = 1;
+ err:
+ BN_CTX_end(ctx);
+ return ret;
+}
+
+int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
+{
+ if (!BN_sqr(r, a, ctx))
+ return 0;
+ /* r->neg == 0, thus we don't need BN_nnmod */
+ return BN_mod(r, r, m, ctx);
+}
+
+int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
+{
+ if (!BN_lshift1(r, a))
+ return 0;
+ bn_check_top(r);
+ return BN_nnmod(r, r, m, ctx);
+}
+
+/*
+ * BN_mod_lshift1 variant that may be used if a is non-negative and less than
+ * m
+ */
+int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
+{
+ if (!BN_lshift1(r, a))
+ return 0;
+ bn_check_top(r);
+ if (BN_cmp(r, m) >= 0)
+ return BN_sub(r, r, m);
+ return 1;
+}
+
+int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m,
+ BN_CTX *ctx)
+{
+ BIGNUM *abs_m = NULL;
+ int ret;
+
+ if (!BN_nnmod(r, a, m, ctx))
+ return 0;
+
+ if (m->neg) {
+ abs_m = BN_dup(m);
+ if (abs_m == NULL)
+ return 0;
+ abs_m->neg = 0;
+ }
+
+ ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
+ bn_check_top(r);
+
+ BN_free(abs_m);
+ return ret;
+}
+
+/*
+ * BN_mod_lshift variant that may be used if a is non-negative and less than
+ * m
+ */
+int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
+{
+ if (r != a) {
+ if (BN_copy(r, a) == NULL)
+ return 0;
+ }
+
+ while (n > 0) {
+ int max_shift;
+
+ /* 0 < r < m */
+ max_shift = BN_num_bits(m) - BN_num_bits(r);
+ /* max_shift >= 0 */
+
+ if (max_shift < 0) {
+ BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED);
+ return 0;
+ }
+
+ if (max_shift > n)
+ max_shift = n;
+
+ if (max_shift) {
+ if (!BN_lshift(r, r, max_shift))
+ return 0;
+ n -= max_shift;
+ } else {
+ if (!BN_lshift1(r, r))
+ return 0;
+ --n;
+ }
+
+ /* BN_num_bits(r) <= BN_num_bits(m) */
+
+ if (BN_cmp(r, m) >= 0) {
+ if (!BN_sub(r, r, m))
+ return 0;
+ }
+ }
+ bn_check_top(r);
+
+ return 1;
+}
projects / openssl.git / blobdiff