21a76df55c
The Android KeyStore backed KeyPairGenerator can generate EC key
pairs, but it cannot be instantiated via the standard JCA approach of
KeyPairGenerator.getInstance("EC", "AndroidKeyStore"). Instead, the
user must invoke KeyPairGenerator.getInstance("RSA",
"AndroidKeyStore") and then tell it to generate an EC key pair.
This CL fixes this weirdness.
The fix requires the introduction of late resolution of key algorithm
and default key size. Prior to this CL, these parameters were resolved
prior to KeyPairGenerator initialization, inside KeyPairGeneratorSpec.
In this CL, these parameters are resolved during KeyPairGenerator
initialization. This is fine because KeyPairGeneratorSpec should be as
dumb as possible and all the logic should reside in KeyPairGenerator
and lower layers.
Bug: 19018089
Change-Id: I114502356e6c9691518cf05b6d9eb0920b4fe0b2
312 lines
12 KiB
Java
312 lines
12 KiB
Java
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.security;
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import com.android.org.bouncycastle.x509.X509V3CertificateGenerator;
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import com.android.org.conscrypt.NativeCrypto;
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import com.android.org.conscrypt.OpenSSLEngine;
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import java.security.InvalidAlgorithmParameterException;
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import java.security.InvalidKeyException;
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import java.security.KeyFactory;
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import java.security.KeyPair;
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import java.security.KeyPairGenerator;
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import java.security.KeyPairGeneratorSpi;
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import java.security.NoSuchAlgorithmException;
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import java.security.PrivateKey;
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import java.security.PublicKey;
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import java.security.SecureRandom;
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import java.security.cert.CertificateEncodingException;
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import java.security.cert.X509Certificate;
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import java.security.spec.AlgorithmParameterSpec;
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import java.security.spec.InvalidKeySpecException;
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import java.security.spec.RSAKeyGenParameterSpec;
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import java.security.spec.X509EncodedKeySpec;
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/**
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* Provides a way to create instances of a KeyPair which will be placed in the
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* Android keystore service usable only by the application that called it. This
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* can be used in conjunction with
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* {@link java.security.KeyStore#getInstance(String)} using the
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* {@code "AndroidKeyStore"} type.
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* <p>
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* This class can not be directly instantiated and must instead be used via the
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* {@link KeyPairGenerator#getInstance(String)
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* KeyPairGenerator.getInstance("AndroidKeyPairGenerator")} API.
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*
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* {@hide}
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*/
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public abstract class AndroidKeyPairGenerator extends KeyPairGeneratorSpi {
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public static class RSA extends AndroidKeyPairGenerator {
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public RSA() {
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super("RSA");
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}
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}
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public static class EC extends AndroidKeyPairGenerator {
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public EC() {
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super("EC");
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}
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}
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/*
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* These must be kept in sync with system/security/keystore/defaults.h
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*/
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/* EC */
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private static final int EC_DEFAULT_KEY_SIZE = 256;
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private static final int EC_MIN_KEY_SIZE = 192;
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private static final int EC_MAX_KEY_SIZE = 521;
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/* RSA */
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private static final int RSA_DEFAULT_KEY_SIZE = 2048;
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private static final int RSA_MIN_KEY_SIZE = 512;
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private static final int RSA_MAX_KEY_SIZE = 8192;
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private final String mAlgorithm;
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private android.security.KeyStore mKeyStore;
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private KeyPairGeneratorSpec mSpec;
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private String mKeyAlgorithm;
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private int mKeyType;
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private int mKeySize;
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protected AndroidKeyPairGenerator(String algorithm) {
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mAlgorithm = algorithm;
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}
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public String getAlgorithm() {
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return mAlgorithm;
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}
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/**
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* Generate a KeyPair which is backed by the Android keystore service. You
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* must call {@link KeyPairGenerator#initialize(AlgorithmParameterSpec)}
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* with an {@link KeyPairGeneratorSpec} as the {@code params}
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* argument before calling this otherwise an {@code IllegalStateException}
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* will be thrown.
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* <p>
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* This will create an entry in the Android keystore service with a
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* self-signed certificate using the {@code params} specified in the
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* {@code initialize(params)} call.
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*
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* @throws IllegalStateException when called before calling
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* {@link KeyPairGenerator#initialize(AlgorithmParameterSpec)}
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* @see java.security.KeyPairGeneratorSpi#generateKeyPair()
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*/
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@Override
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public KeyPair generateKeyPair() {
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if (mKeyStore == null || mSpec == null) {
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throw new IllegalStateException(
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"Must call initialize with an android.security.KeyPairGeneratorSpec first");
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}
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if (((mSpec.getFlags() & KeyStore.FLAG_ENCRYPTED) != 0)
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&& (mKeyStore.state() != KeyStore.State.UNLOCKED)) {
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throw new IllegalStateException(
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"Android keystore must be in initialized and unlocked state "
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+ "if encryption is required");
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}
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final String alias = mSpec.getKeystoreAlias();
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Credentials.deleteAllTypesForAlias(mKeyStore, alias);
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byte[][] args = getArgsForKeyType(mKeyType, mSpec.getAlgorithmParameterSpec());
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final String privateKeyAlias = Credentials.USER_PRIVATE_KEY + alias;
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if (!mKeyStore.generate(privateKeyAlias, KeyStore.UID_SELF, mKeyType, mKeySize,
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mSpec.getFlags(), args)) {
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throw new IllegalStateException("could not generate key in keystore");
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}
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final PrivateKey privKey;
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final OpenSSLEngine engine = OpenSSLEngine.getInstance("keystore");
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try {
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privKey = engine.getPrivateKeyById(privateKeyAlias);
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} catch (InvalidKeyException e) {
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throw new RuntimeException("Can't get key", e);
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}
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final byte[] pubKeyBytes = mKeyStore.getPubkey(privateKeyAlias);
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final PublicKey pubKey;
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try {
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final KeyFactory keyFact = KeyFactory.getInstance(mKeyAlgorithm);
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pubKey = keyFact.generatePublic(new X509EncodedKeySpec(pubKeyBytes));
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} catch (NoSuchAlgorithmException e) {
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throw new IllegalStateException("Can't instantiate key generator", e);
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} catch (InvalidKeySpecException e) {
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throw new IllegalStateException("keystore returned invalid key encoding", e);
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}
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final X509Certificate cert;
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try {
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cert = generateCertificate(privKey, pubKey);
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} catch (Exception e) {
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Credentials.deleteAllTypesForAlias(mKeyStore, alias);
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throw new IllegalStateException("Can't generate certificate", e);
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}
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byte[] certBytes;
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try {
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certBytes = cert.getEncoded();
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} catch (CertificateEncodingException e) {
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Credentials.deleteAllTypesForAlias(mKeyStore, alias);
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throw new IllegalStateException("Can't get encoding of certificate", e);
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}
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if (!mKeyStore.put(Credentials.USER_CERTIFICATE + alias, certBytes, KeyStore.UID_SELF,
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mSpec.getFlags())) {
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Credentials.deleteAllTypesForAlias(mKeyStore, alias);
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throw new IllegalStateException("Can't store certificate in AndroidKeyStore");
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}
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return new KeyPair(pubKey, privKey);
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}
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@SuppressWarnings("deprecation")
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private X509Certificate generateCertificate(PrivateKey privateKey, PublicKey publicKey)
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throws Exception {
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final X509V3CertificateGenerator certGen = new X509V3CertificateGenerator();
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certGen.setPublicKey(publicKey);
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certGen.setSerialNumber(mSpec.getSerialNumber());
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certGen.setSubjectDN(mSpec.getSubjectDN());
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certGen.setIssuerDN(mSpec.getSubjectDN());
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certGen.setNotBefore(mSpec.getStartDate());
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certGen.setNotAfter(mSpec.getEndDate());
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certGen.setSignatureAlgorithm(getDefaultSignatureAlgorithmForKeyAlgorithm(mKeyAlgorithm));
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return certGen.generate(privateKey);
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}
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private String getKeyAlgorithm(KeyPairGeneratorSpec spec) {
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String result = spec.getKeyType();
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if (result != null) {
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return result;
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}
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return getAlgorithm();
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}
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private static int getDefaultKeySize(int keyType) {
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if (keyType == NativeCrypto.EVP_PKEY_EC) {
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return EC_DEFAULT_KEY_SIZE;
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} else if (keyType == NativeCrypto.EVP_PKEY_RSA) {
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return RSA_DEFAULT_KEY_SIZE;
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}
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return -1;
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}
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private static void checkValidKeySize(String keyAlgorithm, int keyType, int keySize)
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throws InvalidAlgorithmParameterException {
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if (keyType == NativeCrypto.EVP_PKEY_EC) {
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if (keySize < EC_MIN_KEY_SIZE || keySize > EC_MAX_KEY_SIZE) {
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throw new InvalidAlgorithmParameterException("EC keys must be >= "
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+ EC_MIN_KEY_SIZE + " and <= " + EC_MAX_KEY_SIZE);
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}
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} else if (keyType == NativeCrypto.EVP_PKEY_RSA) {
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if (keySize < RSA_MIN_KEY_SIZE || keySize > RSA_MAX_KEY_SIZE) {
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throw new InvalidAlgorithmParameterException("RSA keys must be >= "
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+ RSA_MIN_KEY_SIZE + " and <= " + RSA_MAX_KEY_SIZE);
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}
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} else {
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throw new InvalidAlgorithmParameterException(
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"Unsupported key algorithm: " + keyAlgorithm);
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}
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}
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private static void checkCorrectParametersSpec(int keyType, int keySize,
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AlgorithmParameterSpec spec) throws InvalidAlgorithmParameterException {
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if (keyType == NativeCrypto.EVP_PKEY_RSA && spec != null) {
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if (spec instanceof RSAKeyGenParameterSpec) {
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RSAKeyGenParameterSpec rsaSpec = (RSAKeyGenParameterSpec) spec;
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if (keySize != -1 && keySize != rsaSpec.getKeysize()) {
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throw new InvalidAlgorithmParameterException("RSA key size must match: "
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+ keySize + " vs " + rsaSpec.getKeysize());
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}
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} else {
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throw new InvalidAlgorithmParameterException(
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"RSA may only use RSAKeyGenParameterSpec");
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}
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}
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}
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private static String getDefaultSignatureAlgorithmForKeyAlgorithm(String algorithm) {
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if ("RSA".equalsIgnoreCase(algorithm)) {
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return "sha256WithRSA";
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} else if ("EC".equalsIgnoreCase(algorithm)) {
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return "sha256WithECDSA";
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} else {
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throw new IllegalArgumentException("Unsupported key type " + algorithm);
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}
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}
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private static byte[][] getArgsForKeyType(int keyType, AlgorithmParameterSpec spec) {
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switch (keyType) {
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case NativeCrypto.EVP_PKEY_RSA:
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if (spec instanceof RSAKeyGenParameterSpec) {
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RSAKeyGenParameterSpec rsaSpec = (RSAKeyGenParameterSpec) spec;
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return new byte[][] { rsaSpec.getPublicExponent().toByteArray() };
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}
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break;
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}
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return null;
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}
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@Override
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public void initialize(int keysize, SecureRandom random) {
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throw new IllegalArgumentException("cannot specify keysize with AndroidKeyPairGenerator");
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}
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@Override
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public void initialize(AlgorithmParameterSpec params, SecureRandom random)
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throws InvalidAlgorithmParameterException {
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if (params == null) {
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throw new InvalidAlgorithmParameterException(
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"must supply params of type android.security.KeyPairGeneratorSpec");
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} else if (!(params instanceof KeyPairGeneratorSpec)) {
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throw new InvalidAlgorithmParameterException(
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"params must be of type android.security.KeyPairGeneratorSpec");
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}
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KeyPairGeneratorSpec spec = (KeyPairGeneratorSpec) params;
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String keyAlgorithm = getKeyAlgorithm(spec);
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int keyType = KeyStore.getKeyTypeForAlgorithm(keyAlgorithm);
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if (keyType == -1) {
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throw new InvalidAlgorithmParameterException(
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"Unsupported key algorithm: " + keyAlgorithm);
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}
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int keySize = spec.getKeySize();
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if (keySize == -1) {
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keySize = getDefaultKeySize(keyType);
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if (keySize == -1) {
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throw new InvalidAlgorithmParameterException(
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"Unsupported key algorithm: " + keyAlgorithm);
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}
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}
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checkCorrectParametersSpec(keyType, keySize, spec.getAlgorithmParameterSpec());
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checkValidKeySize(keyAlgorithm, keyType, keySize);
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mKeyAlgorithm = keyAlgorithm;
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mKeyType = keyType;
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mKeySize = keySize;
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mSpec = spec;
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mKeyStore = android.security.KeyStore.getInstance();
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}
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}
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