fuzz/bndiv.c

   1 /*
   2  * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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 <openssl/err.h>
  19 #include "fuzzer.h"
  20
  21 /* 256 kB */
  22 #define MAX_LEN (256 * 1000)
  23
  24 static BN_CTX *ctx;
  25 static BIGNUM *b1;
  26 static BIGNUM *b2;
  27 static BIGNUM *b3;
  28 static BIGNUM *b4;
  29 static BIGNUM *b5;
  30
  31 int FuzzerInitialize(int *argc, char ***argv)
  32 {
  33     b1 = BN_new();
  34     b2 = BN_new();
  35     b3 = BN_new();
  36     b4 = BN_new();
  37     b5 = BN_new();
  38     ctx = BN_CTX_new();
  39
  40     OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CRYPTO_STRINGS, NULL);
  41     ERR_get_state();
  42
  43     return 1;
  44 }
  45
  46 int FuzzerTestOneInput(const uint8_t *buf, size_t len)
  47 {
  48     int success = 0;
  49     size_t l1 = 0, l2 = 0;
  50     /* s1 and s2 will be the signs for b1 and b2. */
  51     int s1 = 0, s2 = 0;
  52
  53     /* limit the size of the input to avoid timeout */
  54     if (len > MAX_LEN)
  55         len = MAX_LEN;
  56
  57     /* We are going to split the buffer in two, sizes l1 and l2, giving b1 and
  58      * b2.
  59      */
  60     if (len > 0) {
  61         --len;
  62         /* Use first byte to divide the remaining buffer into 3Fths. I admit
  63          * this disallows some number sizes. If it matters, better ideas are
  64          * welcome (Ben).
  65          */
  66         l1 = ((buf[0] & 0x3f) * len) / 0x3f;
  67         s1 = buf[0] & 0x40;
  68         s2 = buf[0] & 0x80;
  69         ++buf;
  70         l2 = len - l1;
  71     }
  72     OPENSSL_assert(BN_bin2bn(buf, l1, b1) == b1);
  73     BN_set_negative(b1, s1);
  74     OPENSSL_assert(BN_bin2bn(buf + l1, l2, b2) == b2);
  75     BN_set_negative(b2, s2);
  76
  77     /* divide by 0 is an error */
  78     if (BN_is_zero(b2)) {
  79         success = 1;
  80         goto done;
  81     }
  82
  83     OPENSSL_assert(BN_div(b3, b4, b1, b2, ctx));
  84     if (BN_is_zero(b1))
  85         success = BN_is_zero(b3) && BN_is_zero(b4);
  86     else if (BN_is_negative(b1))
  87         success = (BN_is_negative(b3) != BN_is_negative(b2) || BN_is_zero(b3))
  88             && (BN_is_negative(b4) || BN_is_zero(b4));
  89     else
  90         success = (BN_is_negative(b3) == BN_is_negative(b2)  || BN_is_zero(b3))
  91             && (!BN_is_negative(b4) || BN_is_zero(b4));
  92     OPENSSL_assert(BN_mul(b5, b3, b2, ctx));
  93     OPENSSL_assert(BN_add(b5, b5, b4));
  94
  95     success = success && BN_cmp(b5, b1) == 0;
  96     if (!success) {
  97         BN_print_fp(stdout, b1);
  98         putchar('\n');
  99         BN_print_fp(stdout, b2);
 100         putchar('\n');
 101         BN_print_fp(stdout, b3);
 102         putchar('\n');
 103         BN_print_fp(stdout, b4);
 104         putchar('\n');
 105         BN_print_fp(stdout, b5);
 106         putchar('\n');
 107         printf("%d %d %d %d %d %d %d\n", BN_is_negative(b1),
 108                BN_is_negative(b2),
 109                BN_is_negative(b3), BN_is_negative(b4), BN_is_zero(b4),
 110                BN_is_negative(b3) != BN_is_negative(b2)
 111                && (BN_is_negative(b4) || BN_is_zero(b4)),
 112                BN_cmp(b5, b1));
 113         puts("----\n");
 114     }
 115
 116  done:
 117     OPENSSL_assert(success);
 118     ERR_clear_error();
 119
 120     return 0;
 121 }
 122
 123 void FuzzerCleanup(void)
 124 {
 125     BN_free(b1);
 126     BN_free(b2);
 127     BN_free(b3);
 128     BN_free(b4);
 129     BN_free(b5);
 130     BN_CTX_free(ctx);
 131 }