pYv5wQ18

1import javax.crypto.*;
2import javax.crypto.spec.GCMParameterSpec;
3import java.nio.ByteBuffer;
4import java.security.SecureRandom;
5import java.util.Arrays;
6
7public class AESGCMUpdateAAD2 {
8
9    // AES-GCM parameters
10    public static final int AES_KEY_SIZE = 128; // in bits
11    public static final int GCM_NONCE_LENGTH = 12; // in bytes
12    public static final int GCM_TAG_LENGTH = 16; // in bytes
13
14    public static void main(String[] args) throws Exception {
15        int testNum = 0; // pass
16
17        if (args.length > 0) {
18            testNum = Integer.parseInt(args[0]);
19            if (testNum <0 || testNum > 3) {
20                System.out.println("Usage: java AESGCMUpdateAAD2 [X]");
21                System.out.println("X can be 0, 1, 2, 3");
22                System.exit(1);
23            }
24        }
25        byte[] input = "Hello AES-GCM World!".getBytes();
26
27        // Initialise random and generate key
28        SecureRandom random = SecureRandom.getInstanceStrong();
29        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
30        keyGen.init(AES_KEY_SIZE, random);
31        SecretKey key = keyGen.generateKey();
32
33        // Encrypt
34        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "SunJCE");
35        final byte[] nonce = new byte[GCM_NONCE_LENGTH];
36        random.nextBytes(nonce);
37        GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, nonce);
38        cipher.init(Cipher.ENCRYPT_MODE, key, spec);
39
40        byte[] aad = "Whatever I like".getBytes();;
41        cipher.updateAAD(aad);
42
43        byte[] cipherText = cipher.doFinal(input);
44
45        // Decrypt; nonce is shared implicitly
46        cipher.init(Cipher.DECRYPT_MODE, key, spec);
47
48        // EXPECTED: Uncommenting this will cause an AEADBadTagException when decrypting
49        // because AAD value is altered
50        if (testNum == 1) aad[1]++;
51
52        cipher.updateAAD(aad);
53
54        // EXPECTED: Uncommenting this will cause an AEADBadTagException when decrypting
55        // because the encrypted data has been altered
56        if (testNum == 2) cipherText[10]++;
57
58        // EXPECTED: Uncommenting this will cause an AEADBadTagException when decrypting
59        // because the tag has been altered
60        if (testNum == 3) cipherText[cipherText.length - 2]++;
61
62        try {
63            byte[] plainText = cipher.doFinal(cipherText);
64            if (testNum != 0) {
65                System.out.println("Test Failed: expected AEADBadTagException not thrown");
66            } else {
67                // check if the decryption result matches
68                if (Arrays.equals(input, plainText)) {
69                    System.out.println("Test Passed: match!");
70                } else {
71                    System.out.println("Test Failed: result mismatch!");
72                    System.out.println(new String(plainText));
73                }
74            }
75        } catch(AEADBadTagException ex) {
76            if (testNum == 0) {
77                System.out.println("Test Failed: unexpected ex " + ex);
78                ex.printStackTrace();
79            } else {
80                System.out.println("Test Passed: expected ex " + ex);
81            }
82        }
83    }
84}