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/*
* Copyright (C) 2012 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 com.android.org.bouncycastle.x509.X509V3CertificateGenerator;
import com.android.org.conscrypt.NativeCrypto;
import com.android.org.conscrypt.OpenSSLEngine;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.KeyPairGeneratorSpi;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.DSAParameterSpec;
import java.security.spec.ECParameterSpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAKeyGenParameterSpec;
import java.security.spec.X509EncodedKeySpec;
/**
* Provides a way to create instances of a KeyPair which will be placed in the
* Android keystore service usable only by the application that called it. This
* can be used in conjunction with
* {@link java.security.KeyStore#getInstance(String)} using the
* {@code "AndroidKeyStore"} type.
* <p>
* This class can not be directly instantiated and must instead be used via the
* {@link KeyPairGenerator#getInstance(String)
* KeyPairGenerator.getInstance("AndroidKeyPairGenerator")} API.
*
* {@hide}
*/
public class AndroidKeyPairGenerator extends KeyPairGeneratorSpi {
private android.security.KeyStore mKeyStore;
private KeyPairGeneratorSpec mSpec;
/**
* Generate a KeyPair which is backed by the Android keystore service. You
* must call {@link KeyPairGenerator#initialize(AlgorithmParameterSpec)}
* with an {@link KeyPairGeneratorSpec} as the {@code params}
* argument before calling this otherwise an {@code IllegalStateException}
* will be thrown.
* <p>
* This will create an entry in the Android keystore service with a
* self-signed certificate using the {@code params} specified in the
* {@code initialize(params)} call.
*
* @throws IllegalStateException when called before calling
* {@link KeyPairGenerator#initialize(AlgorithmParameterSpec)}
* @see java.security.KeyPairGeneratorSpi#generateKeyPair()
*/
@Override
public KeyPair generateKeyPair() {
if (mKeyStore == null || mSpec == null) {
throw new IllegalStateException(
"Must call initialize with an android.security.KeyPairGeneratorSpec first");
}
if (((mSpec.getFlags() & KeyStore.FLAG_ENCRYPTED) != 0)
&& (mKeyStore.state() != KeyStore.State.UNLOCKED)) {
throw new IllegalStateException(
"Android keystore must be in initialized and unlocked state "
+ "if encryption is required");
}
final String alias = mSpec.getKeystoreAlias();
Credentials.deleteAllTypesForAlias(mKeyStore, alias);
final int keyType = KeyStore.getKeyTypeForAlgorithm(mSpec.getKeyType());
byte[][] args = getArgsForKeyType(keyType, mSpec.getAlgorithmParameterSpec());
final String privateKeyAlias = Credentials.USER_PRIVATE_KEY + alias;
if (!mKeyStore.generate(privateKeyAlias, KeyStore.UID_SELF, keyType,
mSpec.getKeySize(), mSpec.getFlags(), args)) {
throw new IllegalStateException("could not generate key in keystore");
}
final PrivateKey privKey;
final OpenSSLEngine engine = OpenSSLEngine.getInstance("keystore");
try {
privKey = engine.getPrivateKeyById(privateKeyAlias);
} catch (InvalidKeyException e) {
throw new RuntimeException("Can't get key", e);
}
final byte[] pubKeyBytes = mKeyStore.getPubkey(privateKeyAlias);
final PublicKey pubKey;
try {
final KeyFactory keyFact = KeyFactory.getInstance(mSpec.getKeyType());
pubKey = keyFact.generatePublic(new X509EncodedKeySpec(pubKeyBytes));
} catch (NoSuchAlgorithmException e) {
throw new IllegalStateException("Can't instantiate key generator", e);
} catch (InvalidKeySpecException e) {
throw new IllegalStateException("keystore returned invalid key encoding", e);
}
final X509V3CertificateGenerator certGen = new X509V3CertificateGenerator();
certGen.setPublicKey(pubKey);
certGen.setSerialNumber(mSpec.getSerialNumber());
certGen.setSubjectDN(mSpec.getSubjectDN());
certGen.setIssuerDN(mSpec.getSubjectDN());
certGen.setNotBefore(mSpec.getStartDate());
certGen.setNotAfter(mSpec.getEndDate());
certGen.setSignatureAlgorithm(getDefaultSignatureAlgorithmForKeyType(mSpec.getKeyType()));
final X509Certificate cert;
try {
cert = certGen.generate(privKey);
} catch (Exception e) {
Credentials.deleteAllTypesForAlias(mKeyStore, alias);
throw new IllegalStateException("Can't generate certificate", e);
}
byte[] certBytes;
try {
certBytes = cert.getEncoded();
} catch (CertificateEncodingException e) {
Credentials.deleteAllTypesForAlias(mKeyStore, alias);
throw new IllegalStateException("Can't get encoding of certificate", e);
}
if (!mKeyStore.put(Credentials.USER_CERTIFICATE + alias, certBytes, KeyStore.UID_SELF,
mSpec.getFlags())) {
Credentials.deleteAllTypesForAlias(mKeyStore, alias);
throw new IllegalStateException("Can't store certificate in AndroidKeyStore");
}
return new KeyPair(pubKey, privKey);
}
private static String getDefaultSignatureAlgorithmForKeyType(String keyType) {
if ("RSA".equalsIgnoreCase(keyType)) {
return "sha256WithRSA";
} else if ("DSA".equalsIgnoreCase(keyType)) {
return "sha1WithDSA";
} else if ("EC".equalsIgnoreCase(keyType)) {
return "sha256WithECDSA";
} else {
throw new IllegalArgumentException("Unsupported key type " + keyType);
}
}
private static byte[][] getArgsForKeyType(int keyType, AlgorithmParameterSpec spec) {
switch (keyType) {
case NativeCrypto.EVP_PKEY_RSA:
if (spec instanceof RSAKeyGenParameterSpec) {
RSAKeyGenParameterSpec rsaSpec = (RSAKeyGenParameterSpec) spec;
return new byte[][] { rsaSpec.getPublicExponent().toByteArray() };
}
break;
case NativeCrypto.EVP_PKEY_DSA:
if (spec instanceof DSAParameterSpec) {
DSAParameterSpec dsaSpec = (DSAParameterSpec) spec;
return new byte[][] { dsaSpec.getG().toByteArray(),
dsaSpec.getP().toByteArray(), dsaSpec.getQ().toByteArray() };
}
break;
}
return null;
}
@Override
public void initialize(int keysize, SecureRandom random) {
throw new IllegalArgumentException("cannot specify keysize with AndroidKeyPairGenerator");
}
@Override
public void initialize(AlgorithmParameterSpec params, SecureRandom random)
throws InvalidAlgorithmParameterException {
if (params == null) {
throw new InvalidAlgorithmParameterException(
"must supply params of type android.security.KeyPairGeneratorSpec");
} else if (!(params instanceof KeyPairGeneratorSpec)) {
throw new InvalidAlgorithmParameterException(
"params must be of type android.security.KeyPairGeneratorSpec");
}
KeyPairGeneratorSpec spec = (KeyPairGeneratorSpec) params;
mSpec = spec;
mKeyStore = android.security.KeyStore.getInstance();
}
}
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