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      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_clear_error();
     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 }
    132