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
24static BN_CTX *ctx;
25static BIGNUM *b1;
26static BIGNUM *b2;
27static BIGNUM *b3;
28static BIGNUM *b4;
29static BIGNUM *b5;
30
31int 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
46int 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
123void 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