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
FuzzerInitialize(int * argc,char *** argv)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
FuzzerTestOneInput(const uint8_t * buf,size_t len)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
FuzzerCleanup(void)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