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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;
import android.security.keymaster.KeyCharacteristics;
import android.security.keymaster.KeymasterArguments;
import android.security.keymaster.KeymasterDefs;
import java.security.InvalidAlgorithmParameterException;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;
import java.util.Date;
import javax.crypto.KeyGeneratorSpi;
import javax.crypto.SecretKey;
/**
* {@link KeyGeneratorSpi} backed by Android KeyStore.
*
* @hide
*/
public abstract class KeyStoreKeyGeneratorSpi extends KeyGeneratorSpi {
public static class AES extends KeyStoreKeyGeneratorSpi {
public AES() {
super(KeymasterDefs.KM_ALGORITHM_AES, 128);
}
}
protected static abstract class HmacBase extends KeyStoreKeyGeneratorSpi {
protected HmacBase(int keymasterDigest) {
super(KeymasterDefs.KM_ALGORITHM_HMAC,
keymasterDigest,
KeymasterUtils.getDigestOutputSizeBytes(keymasterDigest) * 8);
}
}
public static class HmacSHA1 extends HmacBase {
public HmacSHA1() {
super(KeymasterDefs.KM_DIGEST_SHA1);
}
}
public static class HmacSHA224 extends HmacBase {
public HmacSHA224() {
super(KeymasterDefs.KM_DIGEST_SHA_2_224);
}
}
public static class HmacSHA256 extends HmacBase {
public HmacSHA256() {
super(KeymasterDefs.KM_DIGEST_SHA_2_256);
}
}
public static class HmacSHA384 extends HmacBase {
public HmacSHA384() {
super(KeymasterDefs.KM_DIGEST_SHA_2_384);
}
}
public static class HmacSHA512 extends HmacBase {
public HmacSHA512() {
super(KeymasterDefs.KM_DIGEST_SHA_2_512);
}
}
private final KeyStore mKeyStore = KeyStore.getInstance();
private final int mKeymasterAlgorithm;
private final int mKeymasterDigest;
private final int mDefaultKeySizeBits;
private KeyGeneratorSpec mSpec;
private SecureRandom mRng;
protected KeyStoreKeyGeneratorSpi(
int keymasterAlgorithm,
int defaultKeySizeBits) {
this(keymasterAlgorithm, -1, defaultKeySizeBits);
}
protected KeyStoreKeyGeneratorSpi(
int keymasterAlgorithm,
int keymasterDigest,
int defaultKeySizeBits) {
mKeymasterAlgorithm = keymasterAlgorithm;
mKeymasterDigest = keymasterDigest;
mDefaultKeySizeBits = defaultKeySizeBits;
}
@Override
protected SecretKey engineGenerateKey() {
KeyGeneratorSpec spec = mSpec;
if (spec == null) {
throw new IllegalStateException("Not initialized");
}
if ((spec.isEncryptionRequired())
&& (mKeyStore.state() != KeyStore.State.UNLOCKED)) {
throw new IllegalStateException(
"Android KeyStore must be in initialized and unlocked state if encryption is"
+ " required");
}
KeymasterArguments args = new KeymasterArguments();
args.addInt(KeymasterDefs.KM_TAG_ALGORITHM, mKeymasterAlgorithm);
if (mKeymasterDigest != -1) {
args.addInt(KeymasterDefs.KM_TAG_DIGEST, mKeymasterDigest);
int digestOutputSizeBytes =
KeymasterUtils.getDigestOutputSizeBytes(mKeymasterDigest);
if (digestOutputSizeBytes != -1) {
// TODO: Remove MAC length constraint once Keymaster API no longer requires it.
// TODO: Switch to bits instead of bytes, once this is fixed in Keymaster
args.addInt(KeymasterDefs.KM_TAG_MAC_LENGTH, digestOutputSizeBytes);
}
}
if (mKeymasterAlgorithm == KeymasterDefs.KM_ALGORITHM_HMAC) {
if (mKeymasterDigest == -1) {
throw new IllegalStateException("Digest algorithm must be specified for HMAC key");
}
}
int keySizeBits = (spec.getKeySize() != null) ? spec.getKeySize() : mDefaultKeySizeBits;
args.addInt(KeymasterDefs.KM_TAG_KEY_SIZE, keySizeBits);
@KeyStoreKeyProperties.PurposeEnum int purposes = spec.getPurposes();
int[] keymasterBlockModes = KeymasterUtils.getKeymasterBlockModesFromJcaBlockModes(
spec.getBlockModes());
if (((purposes & KeyStoreKeyProperties.Purpose.ENCRYPT) != 0)
&& (spec.isRandomizedEncryptionRequired())) {
for (int keymasterBlockMode : keymasterBlockModes) {
if (!KeymasterUtils.isKeymasterBlockModeIndCpaCompatible(keymasterBlockMode)) {
throw new IllegalStateException(
"Randomized encryption (IND-CPA) required but may be violated by block"
+ " mode: "
+ KeymasterUtils.getJcaBlockModeFromKeymasterBlockMode(
keymasterBlockMode)
+ ". See KeyGeneratorSpec documentation.");
}
}
}
for (int keymasterPurpose :
KeyStoreKeyProperties.Purpose.allToKeymaster(purposes)) {
args.addInt(KeymasterDefs.KM_TAG_PURPOSE, keymasterPurpose);
}
args.addInts(KeymasterDefs.KM_TAG_BLOCK_MODE, keymasterBlockModes);
args.addInts(
KeymasterDefs.KM_TAG_PADDING,
KeymasterUtils.getKeymasterPaddingsFromJcaEncryptionPaddings(
spec.getEncryptionPaddings()));
if (spec.getUserAuthenticators() == 0) {
args.addBoolean(KeymasterDefs.KM_TAG_NO_AUTH_REQUIRED);
} else {
args.addInt(KeymasterDefs.KM_TAG_USER_AUTH_TYPE,
KeyStoreKeyProperties.UserAuthenticator.allToKeymaster(
spec.getUserAuthenticators()));
}
if (spec.getUserAuthenticationValidityDurationSeconds() != -1) {
args.addInt(KeymasterDefs.KM_TAG_AUTH_TIMEOUT,
spec.getUserAuthenticationValidityDurationSeconds());
}
args.addDate(KeymasterDefs.KM_TAG_ACTIVE_DATETIME,
(spec.getKeyValidityStart() != null)
? spec.getKeyValidityStart() : new Date(0));
args.addDate(KeymasterDefs.KM_TAG_ORIGINATION_EXPIRE_DATETIME,
(spec.getKeyValidityForOriginationEnd() != null)
? spec.getKeyValidityForOriginationEnd() : new Date(Long.MAX_VALUE));
args.addDate(KeymasterDefs.KM_TAG_USAGE_EXPIRE_DATETIME,
(spec.getKeyValidityForConsumptionEnd() != null)
? spec.getKeyValidityForConsumptionEnd() : new Date(Long.MAX_VALUE));
if (((purposes & KeyStoreKeyProperties.Purpose.ENCRYPT) != 0)
&& (!spec.isRandomizedEncryptionRequired())) {
// Permit caller-provided IV when encrypting with this key
args.addBoolean(KeymasterDefs.KM_TAG_CALLER_NONCE);
}
byte[] additionalEntropy = null;
SecureRandom rng = mRng;
if (rng != null) {
additionalEntropy = new byte[(keySizeBits + 7) / 8];
rng.nextBytes(additionalEntropy);
}
int flags = spec.getFlags();
String keyAliasInKeystore = Credentials.USER_SECRET_KEY + spec.getKeystoreAlias();
int errorCode = mKeyStore.generateKey(
keyAliasInKeystore, args, additionalEntropy, flags, new KeyCharacteristics());
if (errorCode != KeyStore.NO_ERROR) {
throw new IllegalStateException(
"Keystore operation failed", KeyStore.getKeyStoreException(errorCode));
}
String keyAlgorithmJCA =
KeymasterUtils.getJcaSecretKeyAlgorithm(mKeymasterAlgorithm, mKeymasterDigest);
return new KeyStoreSecretKey(keyAliasInKeystore, keyAlgorithmJCA);
}
@Override
protected void engineInit(SecureRandom random) {
throw new UnsupportedOperationException("Cannot initialize without an "
+ KeyGeneratorSpec.class.getName() + " parameter");
}
@Override
protected void engineInit(AlgorithmParameterSpec params, SecureRandom random)
throws InvalidAlgorithmParameterException {
if ((params == null) || (!(params instanceof KeyGeneratorSpec))) {
throw new InvalidAlgorithmParameterException("Cannot initialize without an "
+ KeyGeneratorSpec.class.getName() + " parameter");
}
KeyGeneratorSpec spec = (KeyGeneratorSpec) params;
if (spec.getKeystoreAlias() == null) {
throw new InvalidAlgorithmParameterException("KeyStore entry alias not provided");
}
mSpec = spec;
mRng = random;
}
@Override
protected void engineInit(int keySize, SecureRandom random) {
throw new UnsupportedOperationException("Cannot initialize without a "
+ KeyGeneratorSpec.class.getName() + " parameter");
}
}
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