fuzz/bndiv.c

   1 /*
   2  * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL licenses, (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  * https://www.openssl.org/source/license.html
   8  * or in the file LICENSE in the source distribution.
   9  */
  10
  11 /*
  12  * Confirm that if (d, r) = a / b, then b * d + r == a, and that sign(d) ==
  13  * sign(a), and 0 <= r <= b
  14  */
  15
  16 #include <stdio.h>
  17 #include <openssl/bn.h>
  18 #include "fuzzer.h"
  19
  20 int FuzzerInitialize(int *argc, char ***argv) {
  21     return 1;
  22 }
  23
  24 int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
  25     static BN_CTX *ctx;
  26     static BIGNUM *b1;
  27     static BIGNUM *b2;
  28     static BIGNUM *b3;
  29     static BIGNUM *b4;
  30     static BIGNUM *b5;
  31     int success = 0;
  32     size_t l1 = 0, l2 = 0;
  33     /* s1 and s2 will be the signs for b1 and b2. */
  34     int s1 = 0, s2 = 0;
  35
  36     if (ctx == NULL) {
  37         b1 = BN_new();
  38         b2 = BN_new();
  39         b3 = BN_new();
  40         b4 = BN_new();
  41         b5 = BN_new();
  42         ctx = BN_CTX_new();
  43     }
  44     /* We are going to split the buffer in two, sizes l1 and l2, giving b1 and
  45      * b2.
  46      */
  47     if (len > 0) {
  48         --len;
  49         /* Use first byte to divide the remaining buffer into 3Fths. I admit
  50          * this disallows some number sizes. If it matters, better ideas are
  51          * welcome (Ben).
  52          */
  53         l1 = ((buf[0] & 0x3f) * len) / 0x3f;
  54         s1 = buf[0] & 0x40;
  55         s2 = buf[0] & 0x80;
  56         ++buf;
  57         l2 = len - l1;
  58     }
  59     OPENSSL_assert(BN_bin2bn(buf, l1, b1) == b1);
  60     BN_set_negative(b1, s1);
  61     OPENSSL_assert(BN_bin2bn(buf + l1, l2, b2) == b2);
  62     BN_set_negative(b2, s2);
  63
  64     /* divide by 0 is an error */
  65     if (BN_is_zero(b2)) {
  66         success = 1;
  67         goto done;
  68     }
  69
  70     OPENSSL_assert(BN_div(b3, b4, b1, b2, ctx));
  71     if (BN_is_zero(b1))
  72         success = BN_is_zero(b3) && BN_is_zero(b4);
  73     else if (BN_is_negative(b1))
  74         success = (BN_is_negative(b3) != BN_is_negative(b2) || BN_is_zero(b3))
  75             && (BN_is_negative(b4) || BN_is_zero(b4));
  76     else
  77         success = (BN_is_negative(b3) == BN_is_negative(b2)  || BN_is_zero(b3))
  78             && (!BN_is_negative(b4) || BN_is_zero(b4));
  79     OPENSSL_assert(BN_mul(b5, b3, b2, ctx));
  80     OPENSSL_assert(BN_add(b5, b5, b4));
  81
  82     success = success && BN_cmp(b5, b1) == 0;
  83     if (!success) {
  84         BN_print_fp(stdout, b1);
  85         putchar('\n');
  86         BN_print_fp(stdout, b2);
  87         putchar('\n');
  88         BN_print_fp(stdout, b3);
  89         putchar('\n');
  90         BN_print_fp(stdout, b4);
  91         putchar('\n');
  92         BN_print_fp(stdout, b5);
  93         putchar('\n');
  94         printf("%d %d %d %d %d %d %d\n", BN_is_negative(b1),
  95                BN_is_negative(b2),
  96                BN_is_negative(b3), BN_is_negative(b4), BN_is_zero(b4),
  97                BN_is_negative(b3) != BN_is_negative(b2)
  98                && (BN_is_negative(b4) || BN_is_zero(b4)),
  99                BN_cmp(b5, b1));
 100         puts("----\n");
 101     }
 102
 103  done:
 104     OPENSSL_assert(success);
 105
 106     return 0;
 107 }