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87 lines
2.5 KiB
87 lines
2.5 KiB
7 months ago
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// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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// This is a simple example of how to write a fuzzer. The target function is
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// crafted to demonstrates how the fuzzer can analyze conditional branches and
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// incrementally cover more and more code until a defect is found.
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//
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// See build_and_run_toy_fuzzer.sh for examples of how you can build and run
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// this example.
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#include <cstddef>
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#include <cstdint>
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#include <cstring>
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#include "pw_string/util.h"
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namespace {
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// The code to fuzz. This would normally be in separate library.
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void toy_example(const char* word1, const char* word2) {
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bool greeted = false;
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if (word1[0] == 'h') {
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if (word1[1] == 'e') {
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if (word1[2] == 'l') {
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if (word1[3] == 'l') {
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if (word1[4] == 'o') {
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greeted = true;
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}
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}
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}
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}
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}
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if (word2[0] == 'w') {
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if (word2[1] == 'o') {
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if (word2[2] == 'r') {
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if (word2[3] == 'l') {
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if (word2[4] == 'd') {
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if (greeted) {
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// Our "defect", simulating a crash.
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__builtin_trap();
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}
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}
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}
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}
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}
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}
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}
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} // namespace
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// The fuzz target function
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extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
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// We want to split our input into two strings.
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const char* word1 = reinterpret_cast<const char*>(data);
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// If that's not feasible, toss this input. The fuzzer will quickly learn that
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// inputs without null-terminators are uninteresting.
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size_t offset = pw::string::Length(word1, size) + 1;
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if (offset >= size) {
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return 0;
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}
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// Actually, inputs without TWO null terminators are uninteresting.
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const char* word2 = reinterpret_cast<const char*>(&data[offset]);
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size -= offset;
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if (pw::string::Length(word2, size) == size) {
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return 0;
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}
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// Call the code we're targeting!
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toy_example(word1, word2);
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// By convention, the fuzzer always returns zero.
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return 0;
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}
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