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.os.IBinder;
  import android.security.KeyStore;
  import android.security.KeyStoreException;
  import android.security.keymaster.KeymasterArguments;
  import android.security.keymaster.KeymasterDefs;
  import android.security.keymaster.OperationResult;
  
  import java.security.InvalidAlgorithmParameterException;
  import java.security.InvalidKeyException;
  import java.security.Key;
  import java.security.ProviderException;
  import java.security.spec.AlgorithmParameterSpec;
  
  import javax.crypto.MacSpi;
  
  /**
   * {@link MacSpi} which provides HMAC implementations backed by Android KeyStore.
   *
   * @hide
   */
  public abstract class AndroidKeyStoreHmacSpi extends MacSpi implements KeyStoreCryptoOperation {
  
      public static class HmacSHA1 extends AndroidKeyStoreHmacSpi {
          public HmacSHA1() {
              super(KeymasterDefs.KM_DIGEST_SHA1);
          }
      }
  
      public static class HmacSHA224 extends AndroidKeyStoreHmacSpi {
          public HmacSHA224() {
              super(KeymasterDefs.KM_DIGEST_SHA_2_224);
          }
      }
  
      public static class HmacSHA256 extends AndroidKeyStoreHmacSpi {
          public HmacSHA256() {
              super(KeymasterDefs.KM_DIGEST_SHA_2_256);
          }
      }
  
      public static class HmacSHA384 extends AndroidKeyStoreHmacSpi {
          public HmacSHA384() {
              super(KeymasterDefs.KM_DIGEST_SHA_2_384);
          }
      }
  
      public static class HmacSHA512 extends AndroidKeyStoreHmacSpi {
          public HmacSHA512() {
              super(KeymasterDefs.KM_DIGEST_SHA_2_512);
          }
      }
  
      private final KeyStore mKeyStore = KeyStore.getInstance();
      private final int mKeymasterDigest;
      private final int mMacSizeBits;
  
      // Fields below are populated by engineInit and should be preserved after engineDoFinal.
      private AndroidKeyStoreSecretKey mKey;
  
      // Fields below are reset when engineDoFinal succeeds.
      private KeyStoreCryptoOperationChunkedStreamer mChunkedStreamer;
      private IBinder mOperationToken;
      private long mOperationHandle;
  
      protected AndroidKeyStoreHmacSpi(int keymasterDigest) {
          mKeymasterDigest = keymasterDigest;
          mMacSizeBits = KeymasterUtils.getDigestOutputSizeBits(keymasterDigest);
      }
  
      @Override
      protected int engineGetMacLength() {
          return (mMacSizeBits + 7) / 8;
      }
  
      @Override
      protected void engineInit(Key key, AlgorithmParameterSpec params) throws InvalidKeyException,
              InvalidAlgorithmParameterException {
          resetAll();
  
          boolean success = false;
          try {
              init(key, params);
              ensureKeystoreOperationInitialized();
              success = true;
          } finally {
              if (!success) {
                  resetAll();
              }
          }
      }
  
      private void init(Key key, AlgorithmParameterSpec params) throws InvalidKeyException,
          InvalidAlgorithmParameterException {
          if (key == null) {
              throw new InvalidKeyException("key == null");
          } else if (!(key instanceof AndroidKeyStoreSecretKey)) {
              throw new InvalidKeyException(
                      "Only Android KeyStore secret keys supported. Key: " + key);
          }
          mKey = (AndroidKeyStoreSecretKey) key;
  
          if (params != null) {
              throw new InvalidAlgorithmParameterException(
                      "Unsupported algorithm parameters: " + params);
          }
  
      }
  
      private void resetAll() {
          mKey = null;
          IBinder operationToken = mOperationToken;
          if (operationToken != null) {
              mKeyStore.abort(operationToken);
          }
          mOperationToken = null;
          mOperationHandle = 0;
          mChunkedStreamer = null;
      }
  
      private void resetWhilePreservingInitState() {
          IBinder operationToken = mOperationToken;
          if (operationToken != null) {
              mKeyStore.abort(operationToken);
          }
          mOperationToken = null;
          mOperationHandle = 0;
          mChunkedStreamer = null;
      }
  
      @Override
      protected void engineReset() {
          resetWhilePreservingInitState();
      }
  
      private void ensureKeystoreOperationInitialized() throws InvalidKeyException {
          if (mChunkedStreamer != null) {
              return;
          }
          if (mKey == null) {
              throw new IllegalStateException("Not initialized");
          }
  
          KeymasterArguments keymasterArgs = new KeymasterArguments();
          keymasterArgs.addEnum(KeymasterDefs.KM_TAG_ALGORITHM, KeymasterDefs.KM_ALGORITHM_HMAC);
          keymasterArgs.addEnum(KeymasterDefs.KM_TAG_DIGEST, mKeymasterDigest);
          keymasterArgs.addUnsignedInt(KeymasterDefs.KM_TAG_MAC_LENGTH, mMacSizeBits);
  
          OperationResult opResult = mKeyStore.begin(
                  mKey.getAlias(),
                  KeymasterDefs.KM_PURPOSE_SIGN,
                  true,
                  keymasterArgs,
                  null, // no additional entropy needed for HMAC because it's deterministic
                  mKey.getUid());
  
          if (opResult == null) {
              throw new KeyStoreConnectException();
          }
  
          // Store operation token and handle regardless of the error code returned by KeyStore to
          // ensure that the operation gets aborted immediately if the code below throws an exception.
          mOperationToken = opResult.token;
          mOperationHandle = opResult.operationHandle;
  
          // If necessary, throw an exception due to KeyStore operation having failed.
          InvalidKeyException e = KeyStoreCryptoOperationUtils.getInvalidKeyExceptionForInit(
                  mKeyStore, mKey, opResult.resultCode);
          if (e != null) {
              throw e;
          }
  
          if (mOperationToken == null) {
              throw new ProviderException("Keystore returned null operation token");
          }
          if (mOperationHandle == 0) {
              throw new ProviderException("Keystore returned invalid operation handle");
          }
  
          mChunkedStreamer = new KeyStoreCryptoOperationChunkedStreamer(
                  new KeyStoreCryptoOperationChunkedStreamer.MainDataStream(
                          mKeyStore, mOperationToken));
      }
  
      @Override
      protected void engineUpdate(byte input) {
          engineUpdate(new byte[] {input}, 0, 1);
      }
  
      @Override
      protected void engineUpdate(byte[] input, int offset, int len) {
          try {
              ensureKeystoreOperationInitialized();
          } catch (InvalidKeyException e) {
              throw new ProviderException("Failed to reinitialize MAC", e);
          }
  
          byte[] output;
          try {
              output = mChunkedStreamer.update(input, offset, len);
          } catch (KeyStoreException e) {
              throw new ProviderException("Keystore operation failed", e);
          }
          if ((output != null) && (output.length != 0)) {
              throw new ProviderException("Update operation unexpectedly produced output");
          }
      }
  
      @Override
      protected byte[] engineDoFinal() {
          try {
              ensureKeystoreOperationInitialized();
          } catch (InvalidKeyException e) {
              throw new ProviderException("Failed to reinitialize MAC", e);
          }
  
          byte[] result;
          try {
              result = mChunkedStreamer.doFinal(
                      null, 0, 0,
                      null, // no signature provided -- this invocation will generate one
                      null // no additional entropy needed -- HMAC is deterministic
                      );
          } catch (KeyStoreException e) {
              throw new ProviderException("Keystore operation failed", e);
          }
  
          resetWhilePreservingInitState();
          return result;
      }
  
      @Override
      public void finalize() throws Throwable {
          try {
              IBinder operationToken = mOperationToken;
              if (operationToken != null) {
                  mKeyStore.abort(operationToken);
              }
          } finally {
              super.finalize();
          }
      }
  
      @Override
      public long getOperationHandle() {
          return mOperationHandle;
      }
  }
  