/* $OpenBSD: bn_add.c,v 1.13 2018/07/23 18:07:21 tb Exp $ */ /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * 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.] */ #include <stdio.h> #include <openssl/err.h> #include "bn_lcl.h" int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) { int ret, r_neg; bn_check_top(a); bn_check_top(b); if (a->neg == b->neg) { r_neg = a->neg; ret = BN_uadd(r, a, b); } else { int cmp = BN_ucmp(a, b); if (cmp > 0) { r_neg = a->neg; ret = BN_usub(r, a, b); } else if (cmp < 0) { r_neg = b->neg; ret = BN_usub(r, b, a); } else { r_neg = 0; BN_zero(r); ret = 1; } } r->neg = r_neg; bn_check_top(r); return ret; } int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) { int max, min, dif; const BN_ULONG *ap, *bp; BN_ULONG *rp, carry, t1, t2; bn_check_top(a); bn_check_top(b); if (a->top < b->top) { const BIGNUM *tmp; tmp = a; a = b; b = tmp; } max = a->top; min = b->top; dif = max - min; if (bn_wexpand(r, max + 1) == NULL) return 0; r->top = max; ap = a->d; bp = b->d; rp = r->d; carry = bn_add_words(rp, ap, bp, min); rp += min; ap += min; while (dif) { dif--; t1 = *(ap++); t2 = (t1 + carry) & BN_MASK2; *(rp++) = t2; carry &= (t2 == 0); } *rp = carry; r->top += carry; r->neg = 0; bn_check_top(r); return 1; } int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) { int max, min, dif; const BN_ULONG *ap, *bp; BN_ULONG t1, t2, borrow, *rp; bn_check_top(a); bn_check_top(b); max = a->top; min = b->top; dif = max - min; if (dif < 0) { BNerror(BN_R_ARG2_LT_ARG3); return 0; } if (bn_wexpand(r, max) == NULL) return 0; ap = a->d; bp = b->d; rp = r->d; borrow = bn_sub_words(rp, ap, bp, min); ap += min; rp += min; while (dif) { dif--; t1 = *(ap++); t2 = (t1 - borrow) & BN_MASK2; *(rp++) = t2; borrow &= (t1 == 0); } while (max > 0 && *--rp == 0) max--; r->top = max; r->neg = 0; bn_correct_top(r); return 1; } int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) { int ret, r_neg; bn_check_top(a); bn_check_top(b); if (a->neg != b->neg) { r_neg = a->neg; ret = BN_uadd(r, a, b); } else { int cmp = BN_ucmp(a, b); if (cmp > 0) { r_neg = a->neg; ret = BN_usub(r, a, b); } else if (cmp < 0) { r_neg = !b->neg; ret = BN_usub(r, b, a); } else { r_neg = 0; BN_zero(r); ret = 1; } } r->neg = r_neg; bn_check_top(r); return ret; }
