1 /** 2 * Copyright 2021 Google LLC 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. 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 distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 // [START mac-example] 15 package mac; 16 17 import static java.nio.charset.StandardCharsets.UTF_8; 18 19 import com.google.crypto.tink.InsecureSecretKeyAccess; 20 import com.google.crypto.tink.KeysetHandle; 21 import com.google.crypto.tink.Mac; 22 import com.google.crypto.tink.RegistryConfiguration; 23 import com.google.crypto.tink.TinkJsonProtoKeysetFormat; 24 import com.google.crypto.tink.mac.MacConfig; 25 import java.nio.file.Files; 26 import java.nio.file.Path; 27 import java.nio.file.Paths; 28 29 /** 30 * A command-line utility for checking file integrity with a Message Authentication Code (MAC). 31 * 32 * <p>It loads cleartext keys from disk - this is not recommended! 33 * 34 * <p>It requires the following arguments: 35 * 36 * <ul> 37 * <li>mode: either 'compute' or 'verify'. 38 * <li>key-file: Read the key material from this file. 39 * <li>input-file: Read the input from this file. 40 * <li>mac-file: name of the file containing a hexadecimal MAC of the input data. 41 */ 42 public final class MacExample { main(String[] args)43 public static void main(String[] args) throws Exception { 44 if (args.length != 4) { 45 System.err.printf("Expected 4 parameters, got %d\n", args.length); 46 System.err.println("Usage: java MacExample compute/verify key-file input-file mac-file"); 47 System.exit(1); 48 } 49 String mode = args[0]; 50 if (!mode.equals("compute") && !mode.equals("verify")) { 51 System.err.println("Incorrect mode. Please select compute or verify."); 52 System.exit(1); 53 } 54 Path keyFile = Paths.get(args[1]); 55 byte[] msg = Files.readAllBytes(Paths.get(args[2])); 56 Path macFile = Paths.get(args[3]); 57 58 // Register all MAC key types with the Tink runtime. 59 MacConfig.register(); 60 61 // Read the keyset into a KeysetHandle. 62 KeysetHandle handle = 63 TinkJsonProtoKeysetFormat.parseKeyset( 64 new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get()); 65 66 // Get the primitive. 67 Mac macPrimitive = handle.getPrimitive(RegistryConfiguration.get(), Mac.class); 68 69 if (mode.equals("compute")) { 70 byte[] macTag = macPrimitive.computeMac(msg); 71 Files.write(macFile, macTag); 72 } else { 73 byte[] macTag = Files.readAllBytes(macFile); 74 // This will throw a GeneralSecurityException if verification fails. 75 macPrimitive.verifyMac(macTag, msg); 76 } 77 } 78 MacExample()79 private MacExample() {} 80 } 81 // [END mac-example] 82