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SyntheticPasswordCrypto: clean up AES-GCM constants

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SyntheticPasswordCrypto.PROFILE_KEY_IV_SIZE was apparently copied from
LockSettingsService.PROFILE_KEY_IV_SIZE, which is the IV size used when
encrypting profile passwords.  But in SyntheticPasswordCrypto it has
nothing to do with profiles.  Rename it to AES_GCM_IV_SIZE.

For consistency, also rename AES_KEY_LENGTH to AES_GCM_KEY_SIZE and
DEFAULT_TAG_LENGTH_BITS to AES_GCM_TAG_SIZE, and change the latter from
bits to bytes.

No change in behavior; this is just a cleanup.

Test: atest com.android.server.locksettings (on Cuttlefish)
Change-Id: I3358826a7299b62e5be46682291bfc02733c8b1f
This commit is contained in:
Eric Biggers
2022-07-28 20:05:19 +00:00
parent 2c06b9e0b9
commit f2f861c0a8
1 changed files with 13 additions and 13 deletions
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26
services/core/java/com/android/server/locksettings/SyntheticPasswordCrypto.java
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@@ -50,9 +50,9 @@ import javax.crypto.spec.SecretKeySpec;
public class SyntheticPasswordCrypto {
private static final String TAG = "SyntheticPasswordCrypto";
private static final int PROFILE_KEY_IV_SIZE = 12;
private static final int DEFAULT_TAG_LENGTH_BITS = 128;
private static final int AES_KEY_LENGTH = 32; // 256-bit AES key
private static final int AES_GCM_KEY_SIZE = 32; // AES-256-GCM
private static final int AES_GCM_IV_SIZE = 12;
private static final int AES_GCM_TAG_SIZE = 16;
private static final byte[] PROTECTOR_SECRET_PERSONALIZATION = "application-id".getBytes();
// Time between the user credential is verified with GK and the decryption of synthetic password
// under the auth-bound key. This should always happen one after the other, but give it 15
@@ -65,11 +65,11 @@ public class SyntheticPasswordCrypto {
if (blob == null) {
return null;
}
byte[] iv = Arrays.copyOfRange(blob, 0, PROFILE_KEY_IV_SIZE);
byte[] ciphertext = Arrays.copyOfRange(blob, PROFILE_KEY_IV_SIZE, blob.length);
byte[] iv = Arrays.copyOfRange(blob, 0, AES_GCM_IV_SIZE);
byte[] ciphertext = Arrays.copyOfRange(blob, AES_GCM_IV_SIZE, blob.length);
Cipher cipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES + "/"
+ KeyProperties.BLOCK_MODE_GCM + "/" + KeyProperties.ENCRYPTION_PADDING_NONE);
cipher.init(Cipher.DECRYPT_MODE, key, new GCMParameterSpec(DEFAULT_TAG_LENGTH_BITS, iv));
cipher.init(Cipher.DECRYPT_MODE, key, new GCMParameterSpec(AES_GCM_TAG_SIZE * 8, iv));
return cipher.doFinal(ciphertext);
}
@@ -86,13 +86,13 @@ public class SyntheticPasswordCrypto {
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] ciphertext = cipher.doFinal(blob);
byte[] iv = cipher.getIV();
if (iv.length != PROFILE_KEY_IV_SIZE) {
throw new IllegalArgumentException("Invalid iv length: " + iv.length);
if (iv.length != AES_GCM_IV_SIZE) {
throw new IllegalArgumentException("Invalid iv length: " + iv.length + " bytes");
}
final GCMParameterSpec spec = cipher.getParameters().getParameterSpec(
GCMParameterSpec.class);
if (spec.getTLen() != DEFAULT_TAG_LENGTH_BITS) {
throw new IllegalArgumentException("Invalid tag length: " + spec.getTLen());
if (spec.getTLen() != AES_GCM_TAG_SIZE * 8) {
throw new IllegalArgumentException("Invalid tag length: " + spec.getTLen() + " bits");
}
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
outputStream.write(iv);
@@ -102,7 +102,7 @@ public class SyntheticPasswordCrypto {
public static byte[] encrypt(byte[] keyBytes, byte[] personalization, byte[] message) {
byte[] keyHash = personalizedHash(personalization, keyBytes);
SecretKeySpec key = new SecretKeySpec(Arrays.copyOf(keyHash, AES_KEY_LENGTH),
SecretKeySpec key = new SecretKeySpec(Arrays.copyOf(keyHash, AES_GCM_KEY_SIZE),
KeyProperties.KEY_ALGORITHM_AES);
try {
return encrypt(key, message);
@@ -116,7 +116,7 @@ public class SyntheticPasswordCrypto {
public static byte[] decrypt(byte[] keyBytes, byte[] personalization, byte[] ciphertext) {
byte[] keyHash = personalizedHash(personalization, keyBytes);
SecretKeySpec key = new SecretKeySpec(Arrays.copyOf(keyHash, AES_KEY_LENGTH),
SecretKeySpec key = new SecretKeySpec(Arrays.copyOf(keyHash, AES_GCM_KEY_SIZE),
KeyProperties.KEY_ALGORITHM_AES);
try {
return decrypt(key, ciphertext);
@@ -199,7 +199,7 @@ public class SyntheticPasswordCrypto {
long sid) {
try {
KeyGenerator keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES);
keyGenerator.init(AES_KEY_LENGTH * 8, new SecureRandom());
keyGenerator.init(AES_GCM_KEY_SIZE * 8, new SecureRandom());
SecretKey keyStoreKey = keyGenerator.generateKey();
final KeyStore keyStore = getKeyStore();
KeyProtection.Builder builder = new KeyProtection.Builder(KeyProperties.PURPOSE_DECRYPT)