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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.keystore;
import android.security.Credentials;
import android.security.KeyStore;
import android.security.keymaster.KeyCharacteristics;
import android.security.keymaster.KeymasterDefs;
import java.security.InvalidKeyException;
import java.security.ProviderException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactorySpi;
import javax.crypto.spec.SecretKeySpec;
/**
* {@link SecretKeyFactorySpi} backed by Android Keystore.
*
* @hide
*/
public class AndroidKeyStoreSecretKeyFactorySpi extends SecretKeyFactorySpi {
private final KeyStore mKeyStore = KeyStore.getInstance();
@Override
protected KeySpec engineGetKeySpec(SecretKey key,
@SuppressWarnings("rawtypes") Class keySpecClass) throws InvalidKeySpecException {
if (keySpecClass == null) {
throw new InvalidKeySpecException("keySpecClass == null");
}
if (!(key instanceof AndroidKeyStoreSecretKey)) {
throw new InvalidKeySpecException("Only Android KeyStore secret keys supported: " +
((key != null) ? key.getClass().getName() : "null"));
}
if (SecretKeySpec.class.isAssignableFrom(keySpecClass)) {
throw new InvalidKeySpecException(
"Key material export of Android KeyStore keys is not supported");
}
if (!KeyInfo.class.equals(keySpecClass)) {
throw new InvalidKeySpecException("Unsupported key spec: " + keySpecClass.getName());
}
String keyAliasInKeystore = ((AndroidKeyStoreKey) key).getAlias();
String entryAlias;
if (keyAliasInKeystore.startsWith(Credentials.USER_SECRET_KEY)) {
entryAlias = keyAliasInKeystore.substring(Credentials.USER_SECRET_KEY.length());
} else {
throw new InvalidKeySpecException("Invalid key alias: " + keyAliasInKeystore);
}
return getKeyInfo(mKeyStore, entryAlias, keyAliasInKeystore);
}
static KeyInfo getKeyInfo(KeyStore keyStore, String entryAlias, String keyAliasInKeystore) {
KeyCharacteristics keyCharacteristics = new KeyCharacteristics();
int errorCode =
keyStore.getKeyCharacteristics(keyAliasInKeystore, null, null, keyCharacteristics);
if (errorCode != KeyStore.NO_ERROR) {
throw new ProviderException("Failed to obtain information about key."
+ " Keystore error: " + errorCode);
}
boolean insideSecureHardware;
@KeyProperties.OriginEnum int origin;
int keySize;
@KeyProperties.PurposeEnum int purposes;
String[] encryptionPaddings;
String[] signaturePaddings;
@KeyProperties.DigestEnum String[] digests;
@KeyProperties.BlockModeEnum String[] blockModes;
int keymasterSwEnforcedUserAuthenticators;
int keymasterHwEnforcedUserAuthenticators;
try {
if (keyCharacteristics.hwEnforced.containsTag(KeymasterDefs.KM_TAG_ORIGIN)) {
insideSecureHardware = true;
origin = KeyProperties.Origin.fromKeymaster(
keyCharacteristics.hwEnforced.getEnum(KeymasterDefs.KM_TAG_ORIGIN, -1));
} else if (keyCharacteristics.swEnforced.containsTag(KeymasterDefs.KM_TAG_ORIGIN)) {
insideSecureHardware = false;
origin = KeyProperties.Origin.fromKeymaster(
keyCharacteristics.swEnforced.getEnum(KeymasterDefs.KM_TAG_ORIGIN, -1));
} else {
throw new ProviderException("Key origin not available");
}
long keySizeUnsigned =
keyCharacteristics.getUnsignedInt(KeymasterDefs.KM_TAG_KEY_SIZE, -1);
if (keySizeUnsigned == -1) {
throw new ProviderException("Key size not available");
} else if (keySizeUnsigned > Integer.MAX_VALUE) {
throw new ProviderException("Key too large: " + keySizeUnsigned + " bits");
}
keySize = (int) keySizeUnsigned;
purposes = KeyProperties.Purpose.allFromKeymaster(
keyCharacteristics.getEnums(KeymasterDefs.KM_TAG_PURPOSE));
List<String> encryptionPaddingsList = new ArrayList<String>();
List<String> signaturePaddingsList = new ArrayList<String>();
// Keymaster stores both types of paddings in the same array -- we split it into two.
for (int keymasterPadding : keyCharacteristics.getEnums(KeymasterDefs.KM_TAG_PADDING)) {
try {
@KeyProperties.EncryptionPaddingEnum String jcaPadding =
KeyProperties.EncryptionPadding.fromKeymaster(keymasterPadding);
encryptionPaddingsList.add(jcaPadding);
} catch (IllegalArgumentException e) {
try {
@KeyProperties.SignaturePaddingEnum String padding =
KeyProperties.SignaturePadding.fromKeymaster(keymasterPadding);
signaturePaddingsList.add(padding);
} catch (IllegalArgumentException e2) {
throw new ProviderException(
"Unsupported encryption padding: " + keymasterPadding);
}
}
}
encryptionPaddings =
encryptionPaddingsList.toArray(new String[encryptionPaddingsList.size()]);
signaturePaddings =
signaturePaddingsList.toArray(new String[signaturePaddingsList.size()]);
digests = KeyProperties.Digest.allFromKeymaster(
keyCharacteristics.getEnums(KeymasterDefs.KM_TAG_DIGEST));
blockModes = KeyProperties.BlockMode.allFromKeymaster(
keyCharacteristics.getEnums(KeymasterDefs.KM_TAG_BLOCK_MODE));
keymasterSwEnforcedUserAuthenticators =
keyCharacteristics.swEnforced.getEnum(KeymasterDefs.KM_TAG_USER_AUTH_TYPE, 0);
keymasterHwEnforcedUserAuthenticators =
keyCharacteristics.hwEnforced.getEnum(KeymasterDefs.KM_TAG_USER_AUTH_TYPE, 0);
} catch (IllegalArgumentException e) {
throw new ProviderException("Unsupported key characteristic", e);
}
Date keyValidityStart = keyCharacteristics.getDate(KeymasterDefs.KM_TAG_ACTIVE_DATETIME);
Date keyValidityForOriginationEnd =
keyCharacteristics.getDate(KeymasterDefs.KM_TAG_ORIGINATION_EXPIRE_DATETIME);
Date keyValidityForConsumptionEnd =
keyCharacteristics.getDate(KeymasterDefs.KM_TAG_USAGE_EXPIRE_DATETIME);
boolean userAuthenticationRequired =
!keyCharacteristics.getBoolean(KeymasterDefs.KM_TAG_NO_AUTH_REQUIRED);
long userAuthenticationValidityDurationSeconds =
keyCharacteristics.getUnsignedInt(KeymasterDefs.KM_TAG_AUTH_TIMEOUT, -1);
if (userAuthenticationValidityDurationSeconds > Integer.MAX_VALUE) {
throw new ProviderException("User authentication timeout validity too long: "
+ userAuthenticationValidityDurationSeconds + " seconds");
}
boolean userAuthenticationRequirementEnforcedBySecureHardware = (userAuthenticationRequired)
&& (keymasterHwEnforcedUserAuthenticators != 0)
&& (keymasterSwEnforcedUserAuthenticators == 0);
return new KeyInfo(entryAlias,
insideSecureHardware,
origin,
keySize,
keyValidityStart,
keyValidityForOriginationEnd,
keyValidityForConsumptionEnd,
purposes,
encryptionPaddings,
signaturePaddings,
digests,
blockModes,
userAuthenticationRequired,
(int) userAuthenticationValidityDurationSeconds,
userAuthenticationRequirementEnforcedBySecureHardware);
}
@Override
protected SecretKey engineGenerateSecret(KeySpec keySpec) throws InvalidKeySpecException {
throw new UnsupportedOperationException(
"To generate secret key in Android KeyStore, use KeyGenerator initialized with "
+ KeyGenParameterSpec.class.getName());
}
@Override
protected SecretKey engineTranslateKey(SecretKey key) throws InvalidKeyException {
throw new UnsupportedOperationException(
"To import a secret key into Android KeyStore, use KeyStore.setEntry with "
+ KeyProtection.class.getName());
}
}
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