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 {
  22     return 1;
  23 }
  24
  25 int FuzzerTestOneInput(const uint8_t *buf, size_t len)
  26 {
  27     static BN_CTX *ctx;
  28     static BIGNUM *b1;
  29     static BIGNUM *b2;
  30     static BIGNUM *b3;
  31     static BIGNUM *b4;
  32     static BIGNUM *b5;
  33     int success = 0;
  34     size_t l1 = 0, l2 = 0;
  35     /* s1 and s2 will be the signs for b1 and b2. */
  36     int s1 = 0, s2 = 0;
  37
  38     if (ctx == NULL) {
  39         b1 = BN_new();
  40         b2 = BN_new();
  41         b3 = BN_new();
  42         b4 = BN_new();
  43         b5 = BN_new();
  44         ctx = BN_CTX_new();
  45     }
  46     /* We are going to split the buffer in two, sizes l1 and l2, giving b1 and
  47      * b2.
  48      */
  49     if (len > 0) {
  50         --len;
  51         /* Use first byte to divide the remaining buffer into 3Fths. I admit
  52          * this disallows some number sizes. If it matters, better ideas are
  53          * welcome (Ben).
  54          */
  55         l1 = ((buf[0] & 0x3f) * len) / 0x3f;
  56         s1 = buf[0] & 0x40;
  57         s2 = buf[0] & 0x80;
  58         ++buf;
  59         l2 = len - l1;
  60     }
  61     OPENSSL_assert(BN_bin2bn(buf, l1, b1) == b1);
  62     BN_set_negative(b1, s1);
  63     OPENSSL_assert(BN_bin2bn(buf + l1, l2, b2) == b2);
  64     BN_set_negative(b2, s2);
  65
  66     /* divide by 0 is an error */
  67     if (BN_is_zero(b2)) {
  68         success = 1;
  69         goto done;
  70     }
  71
  72     OPENSSL_assert(BN_div(b3, b4, b1, b2, ctx));
  73     if (BN_is_zero(b1))
  74         success = BN_is_zero(b3) && BN_is_zero(b4);
  75     else if (BN_is_negative(b1))
  76         success = (BN_is_negative(b3) != BN_is_negative(b2) || BN_is_zero(b3))
  77             && (BN_is_negative(b4) || BN_is_zero(b4));
  78     else
  79         success = (BN_is_negative(b3) == BN_is_negative(b2)  || BN_is_zero(b3))
  80             && (!BN_is_negative(b4) || BN_is_zero(b4));
  81     OPENSSL_assert(BN_mul(b5, b3, b2, ctx));
  82     OPENSSL_assert(BN_add(b5, b5, b4));
  83
  84     success = success && BN_cmp(b5, b1) == 0;
  85     if (!success) {
  86         BN_print_fp(stdout, b1);
  87         putchar('\n');
  88         BN_print_fp(stdout, b2);
  89         putchar('\n');
  90         BN_print_fp(stdout, b3);
  91         putchar('\n');
  92         BN_print_fp(stdout, b4);
  93         putchar('\n');
  94         BN_print_fp(stdout, b5);
  95         putchar('\n');
  96         printf("%d %d %d %d %d %d %d\n", BN_is_negative(b1),
  97                BN_is_negative(b2),
  98                BN_is_negative(b3), BN_is_negative(b4), BN_is_zero(b4),
  99                BN_is_negative(b3) != BN_is_negative(b2)
 100                && (BN_is_negative(b4) || BN_is_zero(b4)),
 101                BN_cmp(b5, b1));
 102         puts("----\n");
 103     }
 104
 105  done:
 106     OPENSSL_assert(success);
 107
 108     return 0;
 109 }
 110
 111 void FuzzerCleanup(void)
 112 {
 113 }