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      1 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com)
      2  * All rights reserved.
      3  *
      4  * This package is an SSL implementation written
      5  * by Eric Young (eay (at) cryptsoft.com).
      6  * The implementation was written so as to conform with Netscapes SSL.
      7  *
      8  * This library is free for commercial and non-commercial use as long as
      9  * the following conditions are aheared to.  The following conditions
     10  * apply to all code found in this distribution, be it the RC4, RSA,
     11  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
     12  * included with this distribution is covered by the same copyright terms
     13  * except that the holder is Tim Hudson (tjh (at) cryptsoft.com).
     14  *
     15  * Copyright remains Eric Young's, and as such any Copyright notices in
     16  * the code are not to be removed.
     17  * If this package is used in a product, Eric Young should be given attribution
     18  * as the author of the parts of the library used.
     19  * This can be in the form of a textual message at program startup or
     20  * in documentation (online or textual) provided with the package.
     21  *
     22  * Redistribution and use in source and binary forms, with or without
     23  * modification, are permitted provided that the following conditions
     24  * are met:
     25  * 1. Redistributions of source code must retain the copyright
     26  *    notice, this list of conditions and the following disclaimer.
     27  * 2. Redistributions in binary form must reproduce the above copyright
     28  *    notice, this list of conditions and the following disclaimer in the
     29  *    documentation and/or other materials provided with the distribution.
     30  * 3. All advertising materials mentioning features or use of this software
     31  *    must display the following acknowledgement:
     32  *    "This product includes cryptographic software written by
     33  *     Eric Young (eay (at) cryptsoft.com)"
     34  *    The word 'cryptographic' can be left out if the rouines from the library
     35  *    being used are not cryptographic related :-).
     36  * 4. If you include any Windows specific code (or a derivative thereof) from
     37  *    the apps directory (application code) you must include an acknowledgement:
     38  *    "This product includes software written by Tim Hudson (tjh (at) cryptsoft.com)"
     39  *
     40  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
     41  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     43  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     44  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     45  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     46  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     48  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     49  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     50  * SUCH DAMAGE.
     51  *
     52  * The licence and distribution terms for any publically available version or
     53  * derivative of this code cannot be changed.  i.e. this code cannot simply be
     54  * copied and put under another distribution licence
     55  * [including the GNU Public Licence.] */
     56 
     57 #include <openssl/bn.h>
     58 
     59 #include <openssl/mem.h>
     60 
     61 #include "internal.h"
     62 
     63 
     64 int BN_ucmp(const BIGNUM *a, const BIGNUM *b) {
     65   int i;
     66   BN_ULONG t1, t2, *ap, *bp;
     67 
     68   i = a->top - b->top;
     69   if (i != 0) {
     70     return i;
     71   }
     72 
     73   ap = a->d;
     74   bp = b->d;
     75   for (i = a->top - 1; i >= 0; i--) {
     76     t1 = ap[i];
     77     t2 = bp[i];
     78     if (t1 != t2) {
     79       return (t1 > t2) ? 1 : -1;
     80     }
     81   }
     82 
     83   return 0;
     84 }
     85 
     86 int BN_cmp(const BIGNUM *a, const BIGNUM *b) {
     87   int i;
     88   int gt, lt;
     89   BN_ULONG t1, t2;
     90 
     91   if ((a == NULL) || (b == NULL)) {
     92     if (a != NULL) {
     93       return -1;
     94     } else if (b != NULL) {
     95       return 1;
     96     } else {
     97       return 0;
     98     }
     99   }
    100 
    101   if (a->neg != b->neg) {
    102     if (a->neg) {
    103       return -1;
    104     }
    105     return 1;
    106   }
    107   if (a->neg == 0) {
    108     gt = 1;
    109     lt = -1;
    110   } else {
    111     gt = -1;
    112     lt = 1;
    113   }
    114 
    115   if (a->top > b->top) {
    116     return gt;
    117   }
    118   if (a->top < b->top) {
    119     return lt;
    120   }
    121 
    122   for (i = a->top - 1; i >= 0; i--) {
    123     t1 = a->d[i];
    124     t2 = b->d[i];
    125     if (t1 > t2) {
    126       return gt;
    127     } if (t1 < t2) {
    128       return lt;
    129     }
    130   }
    131 
    132   return 0;
    133 }
    134 
    135 int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n) {
    136   int i;
    137   BN_ULONG aa, bb;
    138 
    139   aa = a[n - 1];
    140   bb = b[n - 1];
    141   if (aa != bb) {
    142     return (aa > bb) ? 1 : -1;
    143   }
    144 
    145   for (i = n - 2; i >= 0; i--) {
    146     aa = a[i];
    147     bb = b[i];
    148     if (aa != bb) {
    149       return (aa > bb) ? 1 : -1;
    150     }
    151   }
    152   return 0;
    153 }
    154 
    155 int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl) {
    156   int n, i;
    157   n = cl - 1;
    158 
    159   if (dl < 0) {
    160     for (i = dl; i < 0; i++) {
    161       if (b[n - i] != 0) {
    162         return -1; /* a < b */
    163       }
    164     }
    165   }
    166   if (dl > 0) {
    167     for (i = dl; i > 0; i--) {
    168       if (a[n + i] != 0) {
    169         return 1; /* a > b */
    170       }
    171     }
    172   }
    173 
    174   return bn_cmp_words(a, b, cl);
    175 }
    176 
    177 int BN_abs_is_word(const BIGNUM *bn, BN_ULONG w) {
    178   switch (bn->top) {
    179     case 1:
    180       return bn->d[0] == w;
    181     case 0:
    182       return w == 0;
    183     default:
    184       return 0;
    185   }
    186 }
    187 
    188 int BN_cmp_word(const BIGNUM *a, BN_ULONG b) {
    189   BIGNUM b_bn;
    190   BN_init(&b_bn);
    191 
    192   b_bn.d = &b;
    193   b_bn.top = b > 0;
    194   b_bn.dmax = 1;
    195   b_bn.flags = BN_FLG_STATIC_DATA;
    196   return BN_cmp(a, &b_bn);
    197 }
    198 
    199 int BN_is_zero(const BIGNUM *bn) {
    200   return bn->top == 0;
    201 }
    202 
    203 int BN_is_one(const BIGNUM *bn) {
    204   return bn->neg == 0 && BN_abs_is_word(bn, 1);
    205 }
    206 
    207 int BN_is_word(const BIGNUM *bn, BN_ULONG w) {
    208   return BN_abs_is_word(bn, w) && (w == 0 || bn->neg == 0);
    209 }
    210 
    211 int BN_is_odd(const BIGNUM *bn) {
    212   return bn->top > 0 && (bn->d[0] & 1) == 1;
    213 }
    214 
    215 int BN_is_pow2(const BIGNUM *bn) {
    216   if (bn->top == 0 || bn->neg) {
    217     return 0;
    218   }
    219 
    220   for (int i = 0; i < bn->top - 1; i++) {
    221     if (bn->d[i] != 0) {
    222       return 0;
    223     }
    224   }
    225 
    226   return 0 == (bn->d[bn->top-1] & (bn->d[bn->top-1] - 1));
    227 }
    228 
    229 int BN_equal_consttime(const BIGNUM *a, const BIGNUM *b) {
    230   if (a->top != b->top) {
    231     return 0;
    232   }
    233 
    234   int limbs_are_equal =
    235     CRYPTO_memcmp(a->d, b->d, (size_t)a->top * sizeof(a->d[0])) == 0;
    236 
    237   return constant_time_select_int(constant_time_eq_int(a->neg, b->neg),
    238                                   limbs_are_equal, 0);
    239 }
    240