| 1 | /*
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| 2 | * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the Apache License 2.0 (the "License");
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| 5 | * you may not use this file except in compliance with the License.
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| 6 | * You may obtain a copy of the License at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | * or in the file LICENSE in the source distribution.
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| 9 | */
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| 10 |
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| 11 | /*
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| 12 | * Confirm that a^b mod c agrees when calculated cleverly vs naively, for
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| 13 | * random a, b and c.
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| 14 | */
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| 15 |
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| 16 | #include <stdio.h>
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| 17 | #include <openssl/bn.h>
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| 18 | #include <openssl/err.h>
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| 19 | #include "fuzzer.h"
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| 20 |
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| 21 |
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| 22 | int FuzzerInitialize(int *argc, char ***argv)
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| 23 | {
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| 24 | OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CRYPTO_STRINGS, NULL);
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| 25 | ERR_clear_error();
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| 26 |
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| 27 | return 1;
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| 28 | }
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| 29 |
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| 30 | int FuzzerTestOneInput(const uint8_t *buf, size_t len)
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| 31 | {
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| 32 | int success = 0;
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| 33 | size_t l1 = 0, l2 = 0, l3 = 0;
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| 34 | int s1 = 0, s3 = 0;
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| 35 | BN_CTX *ctx;
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| 36 | BIGNUM *b1;
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| 37 | BIGNUM *b2;
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| 38 | BIGNUM *b3;
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| 39 | BIGNUM *b4;
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| 40 | BIGNUM *b5;
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| 41 |
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| 42 | b1 = BN_new();
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| 43 | b2 = BN_new();
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| 44 | b3 = BN_new();
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| 45 | b4 = BN_new();
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| 46 | b5 = BN_new();
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| 47 | ctx = BN_CTX_new();
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| 48 |
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| 49 | /* Divide the input into three parts, using the values of the first two
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| 50 | * bytes to choose lengths, which generate b1, b2 and b3. Use three bits
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| 51 | * of the third byte to choose signs for the three numbers.
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| 52 | */
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| 53 | if (len > 2) {
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| 54 | len -= 3;
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| 55 | l1 = (buf[0] * len) / 255;
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| 56 | ++buf;
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| 57 | l2 = (buf[0] * (len - l1)) / 255;
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| 58 | ++buf;
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| 59 | l3 = len - l1 - l2;
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| 60 |
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| 61 | s1 = buf[0] & 1;
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| 62 | s3 = buf[0] & 4;
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| 63 | ++buf;
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| 64 | }
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| 65 | OPENSSL_assert(BN_bin2bn(buf, l1, b1) == b1);
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| 66 | BN_set_negative(b1, s1);
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| 67 | OPENSSL_assert(BN_bin2bn(buf + l1, l2, b2) == b2);
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| 68 | OPENSSL_assert(BN_bin2bn(buf + l1 + l2, l3, b3) == b3);
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| 69 | BN_set_negative(b3, s3);
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| 70 |
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| 71 | /* mod 0 is undefined */
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| 72 | if (BN_is_zero(b3)) {
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| 73 | success = 1;
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| 74 | goto done;
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| 75 | }
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| 76 |
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| 77 | OPENSSL_assert(BN_mod_exp(b4, b1, b2, b3, ctx));
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| 78 | OPENSSL_assert(BN_mod_exp_simple(b5, b1, b2, b3, ctx));
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| 79 |
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| 80 | success = BN_cmp(b4, b5) == 0;
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| 81 | if (!success) {
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| 82 | BN_print_fp(stdout, b1);
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| 83 | putchar('\n');
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| 84 | BN_print_fp(stdout, b2);
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| 85 | putchar('\n');
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| 86 | BN_print_fp(stdout, b3);
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| 87 | putchar('\n');
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| 88 | BN_print_fp(stdout, b4);
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| 89 | putchar('\n');
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| 90 | BN_print_fp(stdout, b5);
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| 91 | putchar('\n');
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| 92 | }
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| 93 |
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| 94 | done:
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| 95 | OPENSSL_assert(success);
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| 96 | BN_free(b1);
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| 97 | BN_free(b2);
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| 98 | BN_free(b3);
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| 99 | BN_free(b4);
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| 100 | BN_free(b5);
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| 101 | BN_CTX_free(ctx);
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| 102 | ERR_clear_error();
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| 103 |
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| 104 | return 0;
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| 105 | }
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| 106 |
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| 107 | void FuzzerCleanup(void)
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| 108 | {
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| 109 | }
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