content: /*
   * 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 java.security.InvalidKeyException;
  import java.security.Key;
  import java.security.KeyFactorySpi;
  import java.security.PrivateKey;
  import java.security.PublicKey;
  import java.security.spec.ECPublicKeySpec;
  import java.security.spec.InvalidKeySpecException;
  import java.security.spec.KeySpec;
  import java.security.spec.PKCS8EncodedKeySpec;
  import java.security.spec.RSAPublicKeySpec;
  import java.security.spec.X509EncodedKeySpec;
  
  /**
   * {@link KeyFactorySpi} backed by Android KeyStore.
   *
   * @hide
   */
  public class AndroidKeyStoreKeyFactorySpi extends KeyFactorySpi {
  
      private final KeyStore mKeyStore = KeyStore.getInstance();
  
      @Override
      protected <T extends KeySpec> T engineGetKeySpec(Key key, Class<T> keySpecClass)
              throws InvalidKeySpecException {
          if (key == null) {
              throw new InvalidKeySpecException("key == null");
          } else if ((!(key instanceof AndroidKeyStorePrivateKey))
              && (!(key instanceof AndroidKeyStorePublicKey))) {
              throw new InvalidKeySpecException(
                      "Unsupported key type: " + key.getClass().getName()
                      + ". This KeyFactory supports only Android Keystore asymmetric keys");
          }
  
          // key is an Android Keystore private or public key
  
          if (keySpecClass == null) {
              throw new InvalidKeySpecException("keySpecClass == null");
          } else if (KeyInfo.class.equals(keySpecClass)) {
              if (!(key instanceof AndroidKeyStorePrivateKey)) {
                  throw new InvalidKeySpecException(
                          "Unsupported key type: " + key.getClass().getName()
                          + ". KeyInfo can be obtained only for Android Keystore private keys");
              }
              AndroidKeyStorePrivateKey keystorePrivateKey = (AndroidKeyStorePrivateKey) key;
              String keyAliasInKeystore = keystorePrivateKey.getAlias();
              String entryAlias;
              if (keyAliasInKeystore.startsWith(Credentials.USER_PRIVATE_KEY)) {
                  entryAlias = keyAliasInKeystore.substring(Credentials.USER_PRIVATE_KEY.length());
              } else {
                  throw new InvalidKeySpecException("Invalid key alias: " + keyAliasInKeystore);
              }
              @SuppressWarnings("unchecked")
              T result = (T) AndroidKeyStoreSecretKeyFactorySpi.getKeyInfo(
                      mKeyStore, entryAlias, keyAliasInKeystore, keystorePrivateKey.getUid());
              return result;
          } else if (X509EncodedKeySpec.class.equals(keySpecClass)) {
              if (!(key instanceof AndroidKeyStorePublicKey)) {
                  throw new InvalidKeySpecException(
                          "Unsupported key type: " + key.getClass().getName()
                          + ". X509EncodedKeySpec can be obtained only for Android Keystore public"
                          + " keys");
              }
              @SuppressWarnings("unchecked")
              T result = (T) new X509EncodedKeySpec(((AndroidKeyStorePublicKey) key).getEncoded());
              return result;
          } else if (PKCS8EncodedKeySpec.class.equals(keySpecClass)) {
              if (key instanceof AndroidKeyStorePrivateKey) {
                  throw new InvalidKeySpecException(
                          "Key material export of Android Keystore private keys is not supported");
              } else {
                  throw new InvalidKeySpecException(
                          "Cannot export key material of public key in PKCS#8 format."
                          + " Only X.509 format (X509EncodedKeySpec) supported for public keys.");
              }
          } else if (RSAPublicKeySpec.class.equals(keySpecClass)) {
              if (key instanceof AndroidKeyStoreRSAPublicKey) {
                  AndroidKeyStoreRSAPublicKey rsaKey = (AndroidKeyStoreRSAPublicKey) key;
                  @SuppressWarnings("unchecked")
                  T result =
                          (T) new RSAPublicKeySpec(rsaKey.getModulus(), rsaKey.getPublicExponent());
                  return result;
              } else {
                  throw new InvalidKeySpecException(
                          "Obtaining RSAPublicKeySpec not supported for " + key.getAlgorithm() + " "
                          + ((key instanceof AndroidKeyStorePrivateKey) ? "private" : "public")
                          + " key");
              }
          } else if (ECPublicKeySpec.class.equals(keySpecClass)) {
              if (key instanceof AndroidKeyStoreECPublicKey) {
                  AndroidKeyStoreECPublicKey ecKey = (AndroidKeyStoreECPublicKey) key;
                  @SuppressWarnings("unchecked")
                  T result = (T) new ECPublicKeySpec(ecKey.getW(), ecKey.getParams());
                  return result;
              } else {
                  throw new InvalidKeySpecException(
                          "Obtaining ECPublicKeySpec not supported for " + key.getAlgorithm() + " "
                          + ((key instanceof AndroidKeyStorePrivateKey) ? "private" : "public")
                          + " key");
              }
          } else {
              throw new InvalidKeySpecException("Unsupported key spec: " + keySpecClass.getName());
          }
      }
  
      @Override
      protected PrivateKey engineGeneratePrivate(KeySpec spec) throws InvalidKeySpecException {
          throw new InvalidKeySpecException(
                  "To generate a key pair in Android Keystore, use KeyPairGenerator initialized with"
                  + " " + KeyGenParameterSpec.class.getName());
      }
  
      @Override
      protected PublicKey engineGeneratePublic(KeySpec spec) throws InvalidKeySpecException {
          throw new InvalidKeySpecException(
                  "To generate a key pair in Android Keystore, use KeyPairGenerator initialized with"
                  + " " + KeyGenParameterSpec.class.getName());
      }
  
      @Override
      protected Key engineTranslateKey(Key key) throws InvalidKeyException {
          if (key == null) {
              throw new InvalidKeyException("key == null");
          } else if ((!(key instanceof AndroidKeyStorePrivateKey))
                  && (!(key instanceof AndroidKeyStorePublicKey))) {
              throw new InvalidKeyException(
                      "To import a key into Android Keystore, use KeyStore.setEntry");
          }
          return key;
      }
  }
  