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.TinkJsonProtoKeysetFormat; 23 import com.google.crypto.tink.mac.MacConfig; 24 import java.nio.file.Files; 25 import java.nio.file.Path; 26 import java.nio.file.Paths; 27 28 /** 29 * A command-line utility for checking file integrity with a Message Authentication Code (MAC). 30 * 31 * <p>It loads cleartext keys from disk - this is not recommended! 32 * 33 * <p>It requires the following arguments: 34 * 35 * <ul> 36 * <li>mode: either 'compute' or 'verify'. 37 * <li>key-file: Read the key material from this file. 38 * <li>input-file: Read the input from this file. 39 * <li>mac-file: name of the file containing a hexadecimal MAC of the input data. 40 */ 41 public final class MacExample { main(String[] args)42 public static void main(String[] args) throws Exception { 43 if (args.length != 4) { 44 System.err.printf("Expected 4 parameters, got %d\n", args.length); 45 System.err.println("Usage: java MacExample compute/verify key-file input-file mac-file"); 46 System.exit(1); 47 } 48 String mode = args[0]; 49 if (!mode.equals("compute") && !mode.equals("verify")) { 50 System.err.println("Incorrect mode. Please select compute or verify."); 51 System.exit(1); 52 } 53 Path keyFile = Paths.get(args[1]); 54 byte[] msg = Files.readAllBytes(Paths.get(args[2])); 55 Path macFile = Paths.get(args[3]); 56 57 // Register all MAC key types with the Tink runtime. 58 MacConfig.register(); 59 60 // Read the keyset into a KeysetHandle. 61 KeysetHandle handle = 62 TinkJsonProtoKeysetFormat.parseKeyset( 63 new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get()); 64 65 // Get the primitive. 66 Mac macPrimitive = handle.getPrimitive(Mac.class); 67 68 if (mode.equals("compute")) { 69 byte[] macTag = macPrimitive.computeMac(msg); 70 Files.write(macFile, macTag); 71 } else { 72 byte[] macTag = Files.readAllBytes(macFile); 73 // This will throw a GeneralSecurityException if verification fails. 74 macPrimitive.verifyMac(macTag, msg); 75 } 76 } 77 MacExample()78 private MacExample() {} 79 } 80 // [END mac-example] 81