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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.security.keystore2;
import android.app.ActivityThread;
import android.hardware.biometrics.BiometricManager;
import android.hardware.security.keymint.ErrorCode;
import android.security.GateKeeper;
import android.security.KeyStoreException;
import android.security.KeyStoreOperation;
import android.security.keymaster.KeymasterDefs;
import android.security.keystore.KeyExpiredException;
import android.security.keystore.KeyNotYetValidException;
import android.security.keystore.KeyPermanentlyInvalidatedException;
import android.security.keystore.UserNotAuthenticatedException;
import android.system.keystore2.Authorization;
import android.system.keystore2.ResponseCode;
import android.util.Log;
import libcore.util.EmptyArray;
import java.security.GeneralSecurityException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.List;
/**
* Assorted utility methods for implementing crypto operations on top of KeyStore.
*
* @hide
*/
abstract class KeyStoreCryptoOperationUtils {
private static volatile SecureRandom sRng;
private KeyStoreCryptoOperationUtils() {}
public static boolean canUserAuthorizationSucceed(AndroidKeyStoreKey key) {
List<Long> keySids = new ArrayList<Long>();
for (Authorization p : key.getAuthorizations()) {
switch(p.keyParameter.tag) {
case KeymasterDefs.KM_TAG_USER_SECURE_ID:
keySids.add(p.keyParameter.value.getLongInteger());
break;
default:
break;
}
}
if (keySids.isEmpty()) {
// Key is not bound to any SIDs -- no amount of authentication will help here.
return false;
}
long rootSid = GateKeeper.getSecureUserId();
if ((rootSid != 0) && (keySids.contains(rootSid))) {
// One of the key's SIDs is the current root SID -- user can be authenticated
// against that SID.
return true;
}
long[] biometricSids = ActivityThread
.currentApplication()
.getSystemService(BiometricManager.class)
.getAuthenticatorIds();
// The key must contain every biometric SID. This is because the current API surface
// treats all biometrics (capable of keystore integration) equally. e.g. if the
// device has multiple keystore-capable sensors, and one of the sensor's SIDs
// changed, 1) there is no way for a developer to specify authentication with a
// specific sensor (the one that hasn't changed), and 2) currently the only
// signal to developers is the UserNotAuthenticatedException, which doesn't
// indicate a specific sensor.
boolean canUnlockViaBiometrics = biometricSids.length > 0;
for (long sid : biometricSids) {
if (!keySids.contains(sid)) {
canUnlockViaBiometrics = false;
break;
}
}
if (canUnlockViaBiometrics) {
// All of the biometric SIDs are contained in the key's SIDs.
return true;
}
// None of the key's SIDs can ever be authenticated
return false;
}
/**
* Returns an {@link InvalidKeyException} corresponding to the provided
* {@link KeyStoreException}.
*/
public static InvalidKeyException getInvalidKeyException(
AndroidKeyStoreKey key, KeyStoreException e) {
switch (e.getErrorCode()) {
case KeymasterDefs.KM_ERROR_KEY_EXPIRED:
return new KeyExpiredException();
case KeymasterDefs.KM_ERROR_KEY_NOT_YET_VALID:
return new KeyNotYetValidException();
case ResponseCode.KEY_NOT_FOUND:
// TODO is this the right exception in this case?
case ResponseCode.KEY_PERMANENTLY_INVALIDATED:
return new KeyPermanentlyInvalidatedException();
case ResponseCode.LOCKED:
case ResponseCode.UNINITIALIZED:
case KeymasterDefs.KM_ERROR_KEY_USER_NOT_AUTHENTICATED:
// TODO b/173111727 remove response codes LOCKED and UNINITIALIZED
return new UserNotAuthenticatedException();
default:
return new InvalidKeyException("Keystore operation failed", e);
}
}
/**
* Returns the exception to be thrown by the {@code Cipher.init} method of the crypto operation
* in response to a failed {code IKeystoreSecurityLevel#createOperation()}.
*/
public static GeneralSecurityException getExceptionForCipherInit(
AndroidKeyStoreKey key, KeyStoreException e) {
// Cipher-specific cases
switch (e.getErrorCode()) {
case KeymasterDefs.KM_ERROR_INVALID_NONCE:
return new InvalidAlgorithmParameterException("Invalid IV");
case KeymasterDefs.KM_ERROR_CALLER_NONCE_PROHIBITED:
return new InvalidAlgorithmParameterException("Caller-provided IV not permitted");
}
// General cases
return getInvalidKeyException(key, e);
}
/**
* Returns the requested number of random bytes to mix into keystore/keymaster RNG.
*
* @param rng RNG from which to obtain the random bytes or {@code null} for the platform-default
* RNG.
*/
static byte[] getRandomBytesToMixIntoKeystoreRng(SecureRandom rng, int sizeBytes) {
if (sizeBytes <= 0) {
return EmptyArray.BYTE;
}
if (rng == null) {
rng = getRng();
}
byte[] result = new byte[sizeBytes];
rng.nextBytes(result);
return result;
}
private static SecureRandom getRng() {
// IMPLEMENTATION NOTE: It's OK to share a SecureRandom instance because SecureRandom is
// required to be thread-safe.
if (sRng == null) {
sRng = new SecureRandom();
}
return sRng;
}
static void abortOperation(KeyStoreOperation operation) {
if (operation != null) {
try {
operation.abort();
} catch (KeyStoreException e) {
// Invalid operation handle is very common at this point. It occurs every time
// an already finalized operation gets aborted.
if (e.getErrorCode() != ErrorCode.INVALID_OPERATION_HANDLE) {
// This error gets logged but ignored. Dropping the reference
// to the KeyStoreOperation is enough to clean up all related resources even
// in the Keystore daemon. It gets logged anyway, because it may indicate some
// underlying problem that is worth debugging.
Log.w(
"KeyStoreCryptoOperationUtils",
"Encountered error trying to abort a keystore operation.",
e
);
}
}
}
}
static long getOrMakeOperationChallenge(KeyStoreOperation operation, AndroidKeyStoreKey key)
throws KeyPermanentlyInvalidatedException {
if (operation.getChallenge() != null) {
if (!KeyStoreCryptoOperationUtils.canUserAuthorizationSucceed(key)) {
throw new KeyPermanentlyInvalidatedException();
}
return operation.getChallenge();
} else {
// Keystore won't give us an operation challenge if the operation doesn't
// need user authorization. So we make our own.
return getRng().nextLong();
}
}
}
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