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Merge "Improve CryptoHelper" into nyc-dev

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am: 2cde05c

* commit '2cde05c3bb9267ba6be456af43b0b0710a06c6ea':
  Improve CryptoHelper

Change-Id: I55ede151eac4470e67ac64cbc513936783ae609a
This commit is contained in:
Carlos Valdivia
2016-04-14 01:25:11 +00:00
committed by android-build-merger
parent c19ce2808d 2cde05c3bb
commit b6aa48a469
1 changed files with 43 additions and 47 deletions
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90
services/core/java/com/android/server/accounts/CryptoHelper.java
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@@ -10,15 +10,12 @@ import com.android.internal.util.Preconditions;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
/**
* A crypto helper for encrypting and decrypting bundle with in-memory symmetric
@@ -30,15 +27,15 @@ import javax.crypto.spec.SecretKeySpec;
private static final String KEY_CIPHER = "cipher";
private static final String KEY_MAC = "mac";
private static final String KEY_ALGORITHM = "AES";
private static final String KEY_IV = "iv";
private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding";
private static final String MAC_ALGORITHM = "HMACSHA256";
private static final int IV_LENGTH = 16;
private static CryptoHelper sInstance;
// Keys used for encrypting and decrypting data returned in a Bundle.
private final SecretKeySpec mCipherKeySpec;
private final SecretKeySpec mMacKeySpec;
private final IvParameterSpec mIv;
private final SecretKey mEncryptionKey;
private final SecretKey mMacKey;
/* default */ synchronized static CryptoHelper getInstance() throws NoSuchAlgorithmException {
if (sInstance == null) {
@@ -49,18 +46,10 @@ import javax.crypto.spec.SecretKeySpec;
private CryptoHelper() throws NoSuchAlgorithmException {
KeyGenerator kgen = KeyGenerator.getInstance(KEY_ALGORITHM);
SecretKey skey = kgen.generateKey();
mCipherKeySpec = new SecretKeySpec(skey.getEncoded(), KEY_ALGORITHM);
mEncryptionKey = kgen.generateKey();
// Use a different key for mac-ing than encryption/decryption.
kgen = KeyGenerator.getInstance(MAC_ALGORITHM);
skey = kgen.generateKey();
mMacKeySpec = new SecretKeySpec(skey.getEncoded(), MAC_ALGORITHM);
// Create random iv
byte[] iv = new byte[IV_LENGTH];
SecureRandom secureRandom = new SecureRandom();
secureRandom.nextBytes(iv);
mIv = new IvParameterSpec(iv);
mMacKey = kgen.generateKey();
}
@NonNull
@@ -68,16 +57,19 @@ import javax.crypto.spec.SecretKeySpec;
Preconditions.checkNotNull(bundle, "Cannot encrypt null bundle.");
Parcel parcel = Parcel.obtain();
bundle.writeToParcel(parcel, 0);
byte[] bytes = parcel.marshall();
byte[] clearBytes = parcel.marshall();
parcel.recycle();
Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, mEncryptionKey);
byte[] encryptedBytes = cipher.doFinal(clearBytes);
byte[] iv = cipher.getIV();
byte[] mac = createMac(encryptedBytes, iv);
Bundle encryptedBundle = new Bundle();
byte[] cipher = encrypt(bytes);
byte[] mac = createMac(cipher);
encryptedBundle.putByteArray(KEY_CIPHER, cipher);
encryptedBundle.putByteArray(KEY_CIPHER, encryptedBytes);
encryptedBundle.putByteArray(KEY_MAC, mac);
encryptedBundle.putByteArray(KEY_IV, iv);
return encryptedBundle;
}
@@ -85,19 +77,18 @@ import javax.crypto.spec.SecretKeySpec;
@Nullable
/* default */ Bundle decryptBundle(@NonNull Bundle bundle) throws GeneralSecurityException {
Preconditions.checkNotNull(bundle, "Cannot decrypt null bundle.");
byte[] cipherArray = bundle.getByteArray(KEY_CIPHER);
byte[] macArray = bundle.getByteArray(KEY_MAC);
if (!verifyMac(cipherArray, macArray)) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Escrow mac mismatched!");
}
byte[] iv = bundle.getByteArray(KEY_IV);
byte[] encryptedBytes = bundle.getByteArray(KEY_CIPHER);
byte[] mac = bundle.getByteArray(KEY_MAC);
if (!verifyMac(encryptedBytes, iv, mac)) {
Log.w(TAG, "Escrow mac mismatched!");
return null;
}
IvParameterSpec ivSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, mCipherKeySpec, mIv);
byte[] decryptedBytes = cipher.doFinal(cipherArray);
cipher.init(Cipher.DECRYPT_MODE, mEncryptionKey, ivSpec);
byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
Parcel decryptedParcel = Parcel.obtain();
decryptedParcel.unmarshall(decryptedBytes, 0, decryptedBytes.length);
@@ -108,9 +99,8 @@ import javax.crypto.spec.SecretKeySpec;
return decryptedBundle;
}
private boolean verifyMac(@Nullable byte[] cipherArray, @Nullable byte[] macArray)
private boolean verifyMac(@Nullable byte[] cipherArray, @Nullable byte[] iv, @Nullable byte[] macArray)
throws GeneralSecurityException {
if (cipherArray == null || cipherArray.length == 0 || macArray == null
|| macArray.length == 0) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
@@ -118,23 +108,29 @@ import javax.crypto.spec.SecretKeySpec;
}
return false;
}
Mac mac = Mac.getInstance(MAC_ALGORITHM);
mac.init(mMacKeySpec);
mac.update(cipherArray);
return Arrays.equals(macArray, mac.doFinal());
return constantTimeArrayEquals(macArray, createMac(cipherArray, iv));
}
@NonNull
private byte[] encrypt(@NonNull byte[] data) throws GeneralSecurityException {
Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, mCipherKeySpec, mIv);
return cipher.doFinal(data);
private byte[] createMac(@NonNull byte[] cipher, @NonNull byte[] iv) throws GeneralSecurityException {
Mac mac = Mac.getInstance(MAC_ALGORITHM);
mac.init(mMacKey);
mac.update(cipher);
mac.update(iv);
return mac.doFinal();
}
@NonNull
private byte[] createMac(@NonNull byte[] cipher) throws GeneralSecurityException {
Mac mac = Mac.getInstance(MAC_ALGORITHM);
mac.init(mMacKeySpec);
return mac.doFinal(cipher);
private static boolean constantTimeArrayEquals(byte[] a, byte[] b) {
if (a == null || b == null) {
return a == b;
}
if (a.length != b.length) {
return false;
}
boolean isEqual = true;
for (int i = 0; i < b.length; i++) {
isEqual &= (a[i] == b[i]);
}
return isEqual;
}
}