1 //===-- strstr_fuzz.cpp ---------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// Fuzzing test for llvm-libc strstr implementation.
10 ///
11 //===----------------------------------------------------------------------===//
12
13 #include "src/string/strlen.h"
14 #include "src/string/strstr.h"
15 #include <stddef.h>
16 #include <stdint.h>
17
18 // Simple loop to compare two strings up to a size n.
simple_memcmp(const char * left,const char * right,size_t n)19 static int simple_memcmp(const char *left, const char *right, size_t n) {
20 for (; n && *left == *right; ++left, ++right, --n)
21 ;
22 return n ? *left - *right : 0;
23 }
24
25 // The general structure is to take the value of the first byte, set size1 to
26 // that value, and add the null terminator. size2 will then contain the rest of
27 // the bytes in data.
28 // For example, with inputs (data={2, 6, 4, 8, 0}, size=5):
29 // size1: data[0] = 2
30 // data1: {2, 6} + '\0' = {2, 6, '\0'}
31 // size2: size - size1 = 3
32 // data2: {4, 8, '\0'}
LLVMFuzzerTestOneInput(const uint8_t * data,size_t size)33 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
34 // Verify the size is at least 1 and the data is null terminated.
35 if (!size || data[size - 1] != '\0')
36 return 0;
37 const size_t size1 = (data[0] <= size ? data[0] : size);
38 // The first size will always be at least 1 since
39 // we need to append the null terminator. The second size
40 // needs to be checked since it must also contain the null
41 // terminator.
42 if (size - size1 == 0)
43 return 0;
44
45 // Copy the data into a new container.
46 uint8_t *container = new uint8_t[size1 + 1];
47 if (!container)
48 __builtin_trap();
49
50 size_t i;
51 for (i = 0; i < size1; ++i)
52 container[i] = data[i];
53 container[size1] = '\0'; // Add null terminator to container.
54
55 const char *needle = reinterpret_cast<const char *>(container);
56 const char *haystack = reinterpret_cast<const char *>(data + i);
57 const char *result = __llvm_libc::strstr(haystack, needle);
58
59 // A null terminator may exist earlier in each, so this needs to be recorded.
60 const size_t haystack_size = __llvm_libc::strlen(haystack);
61 const size_t needle_size = __llvm_libc::strlen(needle);
62
63 if (result) {
64 // The needle is in the haystack.
65 // 1. Verify that the result matches the needle.
66 if (simple_memcmp(needle, result, needle_size) != 0)
67 __builtin_trap();
68
69 const char *haystack_ptr = haystack;
70 // 2. Verify that the result is the first occurrence of the needle.
71 for (; haystack_ptr != result; ++haystack_ptr) {
72 if (simple_memcmp(needle, haystack_ptr, needle_size) == 0)
73 __builtin_trap(); // There was an earlier occurrence of the needle.
74 }
75 } else {
76 // No result was found. Verify that the needle doesn't exist within the
77 // haystack.
78 for (size_t i = 0; i + needle_size < haystack_size; ++i) {
79 if (simple_memcmp(needle, haystack + i, needle_size) == 0)
80 __builtin_trap(); // There was an earlier occurrence of the needle.
81 }
82 }
83 delete[] container;
84 return 0;
85 }
86