Commit 55442b8a authored by Davide Galassi's avatar Davide Galassi Committed by Rich Salz
Browse files

BIGNUM signed add/sub routines refactory 



Old code replaced in favor of a clearer implementation.
Performances are not penalized.

Updated the copyright end date to 2018.

Reviewed-by: default avatarDavid Benjamin <davidben@google.com>
Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5963)
parent 9f2a3bb1

crypto/bn/bn_add.c

+47 −85
Original line number Diff line number Diff line 
/*

 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the OpenSSL license (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy
@@ -10,51 +10,69 @@ 
#include "internal/cryptlib.h"

#include "bn_lcl.h"



/* r can == a or b */

/* signed add of b to a. */

int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    int a_neg = a->neg, ret;

    int ret, r_neg, cmp_res;



    bn_check_top(a);

    bn_check_top(b);



    /*-

     *  a +  b      a+b

     *  a + -b      a-b

     * -a +  b      b-a

     * -a + -b      -(a+b)

     */

    if (a_neg ^ b->neg) {

        /* only one is negative */

        if (a_neg) {

            const BIGNUM *tmp;

    if (a->neg == b->neg) {

        r_neg = a->neg;

        ret = BN_uadd(r, a, b);

    } else {

        cmp_res = BN_ucmp(a, b);

        if (cmp_res > 0) {

            r_neg = a->neg;

            ret = BN_usub(r, a, b);

        } else if (cmp_res < 0) {

            r_neg = b->neg;

            ret = BN_usub(r, b, a);

        } else {

            r_neg = 0;

            BN_zero(r);

            ret = 1;

        }

    }



            tmp = a;

            a = b;

            b = tmp;

    r->neg = r_neg;

    bn_check_top(r);

    return ret;

}



        /* we are now a - b */

/* signed sub of b from a. */

int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    int ret, r_neg, cmp_res;



        if (BN_ucmp(a, b) < 0) {

            if (!BN_usub(r, b, a))

                return 0;

            r->neg = 1;

    bn_check_top(a);

    bn_check_top(b);



    if (a->neg != b->neg) {

        r_neg = a->neg;

        ret = BN_uadd(r, a, b);

    } else {

            if (!BN_usub(r, a, b))

                return 0;

            r->neg = 0;

        cmp_res = BN_ucmp(a, b);

        if (cmp_res > 0) {

            r_neg = a->neg;

            ret = BN_usub(r, a, b);

        } else if (cmp_res < 0) {

            r_neg = !b->neg;

            ret = BN_usub(r, b, a);

        } else {

            r_neg = 0;

            BN_zero(r);

            ret = 1;

        }

        return 1;

    }



    ret = BN_uadd(r, a, b);

    r->neg = a_neg;

    r->neg = r_neg;

    bn_check_top(r);

    return ret;

}



/* unsigned add of b to a */

/* unsigned add of b to a, r can be equal to a or b. */

int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    int max, min, dif;
@@ -151,59 +169,3 @@ int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 
    return 1;

}

int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    int max;

    int add = 0, neg = 0;



    bn_check_top(a);

    bn_check_top(b);



    /*-

     *  a -  b      a-b

     *  a - -b      a+b

     * -a -  b      -(a+b)

     * -a - -b      b-a

     */

    if (a->neg) {

        if (b->neg) {

            const BIGNUM *tmp;



            tmp = a;

            a = b;

            b = tmp;

        } else {

            add = 1;

            neg = 1;

        }

    } else {

        if (b->neg) {

            add = 1;

            neg = 0;

        }

    }



    if (add) {

        if (!BN_uadd(r, a, b))

            return 0;

        r->neg = neg;

        return 1;

    }



    /* We are actually doing a - b :-) */



    max = (a->top > b->top) ? a->top : b->top;

    if (bn_wexpand(r, max) == NULL)

        return 0;

    if (BN_ucmp(a, b) < 0) {

        if (!BN_usub(r, b, a))

            return 0;

        r->neg = 1;

    } else {

        if (!BN_usub(r, a, b))

            return 0;

        r->neg = 0;

    }

    bn_check_top(r);

    return 1;

}