1 // Copyright 2021 Google LLC 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 //////////////////////////////////////////////////////////////////////////////// 16 17 import com.code_intelligence.jazzer.api.FuzzedDataProvider; 18 import java.util.Base64; 19 20 public class ExampleValueProfileFuzzer { base64(byte[] input)21 private static String base64(byte[] input) { 22 return Base64.getEncoder().encodeToString(input); 23 } 24 insecureEncrypt(long input)25 private static long insecureEncrypt(long input) { 26 long key = 0xefe4eb93215cb6b0L; 27 return input ^ key; 28 } 29 fuzzerTestOneInput(FuzzedDataProvider data)30 public static void fuzzerTestOneInput(FuzzedDataProvider data) { 31 // Without -use_value_profile=1, the fuzzer gets stuck here as there is no direct correspondence 32 // between the input bytes and the compared string. With value profile, the fuzzer can guess the 33 // expected input byte by byte, which takes linear rather than exponential time. 34 if (base64(data.consumeBytes(6)).equals("SmF6emVy")) { 35 long[] plaintextBlocks = data.consumeLongs(2); 36 if (plaintextBlocks.length != 2) 37 return; 38 if (insecureEncrypt(plaintextBlocks[0]) == 0x9fc48ee64d3dc090L) { 39 // Without --fake_pcs (enabled by default with -use_value_profile=1), the fuzzer would get 40 // stuck here as the value profile information for long comparisons would not be able to 41 // distinguish between this comparison and the one above. 42 if (insecureEncrypt(plaintextBlocks[1]) == 0x888a82ff483ad9c2L) { 43 mustNeverBeCalled(); 44 } 45 } 46 } 47 } 48 mustNeverBeCalled()49 private static void mustNeverBeCalled() { 50 throw new IllegalStateException("mustNeverBeCalled has been called"); 51 } 52 } 53