content: /*
   * Copyright (C) 2016 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 com.google.android.exoplayer2.source.hls;
  
  import android.net.Uri;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.upstream.DataSource;
  import com.google.android.exoplayer2.upstream.DataSourceInputStream;
  import com.google.android.exoplayer2.upstream.DataSpec;
  import com.google.android.exoplayer2.util.Assertions;
  import java.io.IOException;
  import java.security.InvalidAlgorithmParameterException;
  import java.security.InvalidKeyException;
  import java.security.Key;
  import java.security.NoSuchAlgorithmException;
  import java.security.spec.AlgorithmParameterSpec;
  import javax.crypto.Cipher;
  import javax.crypto.CipherInputStream;
  import javax.crypto.NoSuchPaddingException;
  import javax.crypto.spec.IvParameterSpec;
  import javax.crypto.spec.SecretKeySpec;
  
  /**
   * A {@link DataSource} that decrypts data read from an upstream source, encrypted with AES-128 with
   * a 128-bit key and PKCS7 padding.
   * <p>
   * Note that this {@link DataSource} does not support being opened from arbitrary offsets. It is
   * designed specifically for reading whole files as defined in an HLS media playlist. For this
   * reason the implementation is private to the HLS package.
   */
  /* package */ final class Aes128DataSource implements DataSource {
  
    private final DataSource upstream;
    private final byte[] encryptionKey;
    private final byte[] encryptionIv;
  
    private CipherInputStream cipherInputStream;
  
    /**
     * @param upstream The upstream {@link DataSource}.
     * @param encryptionKey The encryption key.
     * @param encryptionIv The encryption initialization vector.
     */
    public Aes128DataSource(DataSource upstream, byte[] encryptionKey, byte[] encryptionIv) {
      this.upstream = upstream;
      this.encryptionKey = encryptionKey;
      this.encryptionIv = encryptionIv;
    }
  
    @Override
    public long open(DataSpec dataSpec) throws IOException {
      Cipher cipher;
      try {
        cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
      } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
        throw new RuntimeException(e);
      }
  
      Key cipherKey = new SecretKeySpec(encryptionKey, "AES");
      AlgorithmParameterSpec cipherIV = new IvParameterSpec(encryptionIv);
  
      try {
        cipher.init(Cipher.DECRYPT_MODE, cipherKey, cipherIV);
      } catch (InvalidKeyException | InvalidAlgorithmParameterException e) {
        throw new RuntimeException(e);
      }
  
      cipherInputStream = new CipherInputStream(
          new DataSourceInputStream(upstream, dataSpec), cipher);
  
      return C.LENGTH_UNSET;
    }
  
    @Override
    public void close() throws IOException {
      cipherInputStream = null;
      upstream.close();
    }
  
    @Override
    public int read(byte[] buffer, int offset, int readLength) throws IOException {
      Assertions.checkState(cipherInputStream != null);
      int bytesRead = cipherInputStream.read(buffer, offset, readLength);
      if (bytesRead < 0) {
        return C.RESULT_END_OF_INPUT;
      }
      return bytesRead;
    }
  
    @Override
    public Uri getUri() {
      return upstream.getUri();
    }
  
  }
  