From a76addba5d59637dec40653698e7dc3551534ced Mon Sep 17 00:00:00 2001
From: Andrey Udovenko <andu.nsk@gmail.com>
Date: Tue, 4 Nov 2014 13:38:22 -0500
Subject: [PATCH] Add AES-128 encryption support for HLS #69 and parsing logic
 for CODECS and RESOLUTION attributes.

---
 .../demo/full/player/HlsRendererBuilder.java  |  2 +-
 .../demo/simple/HlsRendererBuilder.java       |  2 +-
 .../android/exoplayer/hls/HlsChunkSource.java | 75 +++++++++++++--
 .../exoplayer/hls/HlsMasterPlaylist.java      |  8 +-
 .../hls/HlsMasterPlaylistParser.java          | 32 ++++++-
 .../exoplayer/hls/HlsMediaPlaylist.java       | 12 ++-
 .../exoplayer/hls/HlsMediaPlaylistParser.java | 37 ++++++-
 .../android/exoplayer/hls/HlsParserUtil.java  |  8 ++
 .../exoplayer/hls/HlsSampleSource.java        | 10 +-
 .../exoplayer/upstream/Aes128DataSource.java  | 96 +++++++++++++++++++
 10 files changed, 267 insertions(+), 15 deletions(-)
 create mode 100644 library/src/main/java/com/google/android/exoplayer/upstream/Aes128DataSource.java

diff --git a/demo/src/main/java/com/google/android/exoplayer/demo/full/player/HlsRendererBuilder.java b/demo/src/main/java/com/google/android/exoplayer/demo/full/player/HlsRendererBuilder.java
index dd85f933c8..5306dedd2c 100644
--- a/demo/src/main/java/com/google/android/exoplayer/demo/full/player/HlsRendererBuilder.java
+++ b/demo/src/main/java/com/google/android/exoplayer/demo/full/player/HlsRendererBuilder.java
@@ -111,7 +111,7 @@ public class HlsRendererBuilder implements RendererBuilder, ManifestCallback<Hls
 
   private HlsMasterPlaylist newSimpleMasterPlaylist(String mediaPlaylistUrl) {
     return new HlsMasterPlaylist(Uri.parse(""),
-        Collections.singletonList(new Variant(mediaPlaylistUrl, 0)));
+        Collections.singletonList(new Variant(mediaPlaylistUrl, 0, null, -1, -1)));
   }
 
 }
diff --git a/demo/src/main/java/com/google/android/exoplayer/demo/simple/HlsRendererBuilder.java b/demo/src/main/java/com/google/android/exoplayer/demo/simple/HlsRendererBuilder.java
index 4de39d93d6..4845444fbb 100644
--- a/demo/src/main/java/com/google/android/exoplayer/demo/simple/HlsRendererBuilder.java
+++ b/demo/src/main/java/com/google/android/exoplayer/demo/simple/HlsRendererBuilder.java
@@ -109,7 +109,7 @@ import java.util.Collections;
 
   private HlsMasterPlaylist newSimpleMasterPlaylist(String mediaPlaylistUrl) {
     return new HlsMasterPlaylist(Uri.parse(""),
-        Collections.singletonList(new Variant(mediaPlaylistUrl, 0)));
+        Collections.singletonList(new Variant(mediaPlaylistUrl, 0, null, -1, -1)));
   }
 
 }
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsChunkSource.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsChunkSource.java
index 14e9961122..8ea6b27e29 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsChunkSource.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsChunkSource.java
@@ -18,6 +18,7 @@ package com.google.android.exoplayer.hls;
 import com.google.android.exoplayer.C;
 import com.google.android.exoplayer.MediaFormat;
 import com.google.android.exoplayer.TrackRenderer;
+import com.google.android.exoplayer.upstream.Aes128DataSource;
 import com.google.android.exoplayer.upstream.DataSource;
 import com.google.android.exoplayer.upstream.DataSpec;
 import com.google.android.exoplayer.upstream.NonBlockingInputStream;
@@ -28,7 +29,9 @@ import android.os.SystemClock;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
+import java.math.BigInteger;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * A temporary test source of HLS chunks.
@@ -38,7 +41,7 @@ import java.util.List;
  */
 public class HlsChunkSource {
 
-  private final DataSource dataSource;
+  private final DataSource upstreamDataSource;
   private final HlsMasterPlaylist masterPlaylist;
   private final HlsMediaPlaylistParser mediaPlaylistParser;
 
@@ -47,9 +50,12 @@ public class HlsChunkSource {
   /* package */ boolean mediaPlaylistWasLive;
   /* package */ long lastMediaPlaylistLoadTimeMs;
 
+  private DataSource encryptedDataSource;
+  private String encryptionKeyUri;
+
   // TODO: Once proper m3u8 parsing is in place, actually use the url!
   public HlsChunkSource(DataSource dataSource, HlsMasterPlaylist masterPlaylist) {
-    this.dataSource = dataSource;
+    this.upstreamDataSource = dataSource;
     this.masterPlaylist = masterPlaylist;
     mediaPlaylistParser = new HlsMediaPlaylistParser();
   }
@@ -144,8 +150,22 @@ public class HlsChunkSource {
     }
 
     HlsMediaPlaylist.Segment segment = mediaPlaylist.segments.get(chunkIndex);
-
     Uri chunkUri = Util.getMergedUri(mediaPlaylist.baseUri, segment.url);
+
+    // Check if encryption is specified.
+    if (HlsMediaPlaylist.ENCRYPTION_METHOD_AES_128.equals(segment.encryptionMethod)) {
+      if (!segment.encryptionKeyUri.equals(encryptionKeyUri)) {
+        // Encryption is specified and the key has changed.
+        Uri keyUri = Util.getMergedUri(mediaPlaylist.baseUri, segment.encryptionKeyUri);
+        out.chunk = newEncryptionKeyChunk(keyUri, segment.encryptionIV);
+        encryptionKeyUri = segment.encryptionKeyUri;
+        return;
+      }
+    } else {
+      encryptedDataSource = null;
+      encryptionKeyUri = null;
+    }
+
     DataSpec dataSpec = new DataSpec(chunkUri, 0, C.LENGTH_UNBOUNDED, null);
 
     long startTimeUs = segment.startTimeUs;
@@ -168,8 +188,15 @@ public class HlsChunkSource {
       }
     }
 
-    out.chunk = new TsChunk(dataSource, dataSpec, 0, startTimeUs, endTimeUs, nextChunkMediaSequence,
-        segment.discontinuity);
+    DataSource dataSource;
+    if (encryptedDataSource != null) {
+      dataSource = encryptedDataSource;
+    } else {
+      dataSource = upstreamDataSource;
+    }
+
+    out.chunk = new TsChunk(dataSource, dataSpec, 0, startTimeUs, endTimeUs,
+        nextChunkMediaSequence, segment.discontinuity);
   }
 
   private boolean shouldRerequestMediaPlaylist() {
@@ -190,7 +217,12 @@ public class HlsChunkSource {
         masterPlaylist.variants.get(0).url);
     DataSpec dataSpec = new DataSpec(mediaPlaylistUri, 0, C.LENGTH_UNBOUNDED, null);
     Uri mediaPlaylistBaseUri = Util.parseBaseUri(mediaPlaylistUri.toString());
-    return new MediaPlaylistChunk(dataSource, dataSpec, 0, mediaPlaylistBaseUri);
+    return new MediaPlaylistChunk(upstreamDataSource, dataSpec, 0, mediaPlaylistBaseUri);
+  }
+
+  private EncryptionKeyChunk newEncryptionKeyChunk(Uri keyUri, String iv) {
+    DataSpec dataSpec = new DataSpec(keyUri, 0, C.LENGTH_UNBOUNDED, null);
+    return new EncryptionKeyChunk(upstreamDataSource, dataSpec, 0, iv);
   }
 
   private class MediaPlaylistChunk extends HlsChunk {
@@ -214,4 +246,35 @@ public class HlsChunkSource {
 
   }
 
+  private class EncryptionKeyChunk extends HlsChunk {
+
+    private final String iv;
+
+    public EncryptionKeyChunk(DataSource dataSource, DataSpec dataSpec, int trigger, String iv) {
+      super(dataSource, dataSpec, trigger);
+      if (iv.toLowerCase(Locale.getDefault()).startsWith("0x")) {
+        this.iv = iv.substring(2);
+      } else {
+        this.iv = iv;
+      }
+    }
+
+    @Override
+    protected void consumeStream(NonBlockingInputStream stream) throws IOException {
+      byte[] keyData = new byte[(int) stream.getAvailableByteCount()];
+      stream.read(keyData, 0, keyData.length);
+
+      int ivParsed = Integer.parseInt(iv, 16);
+      String iv = String.format("%032X", ivParsed);
+
+      byte[] ivData = new BigInteger(iv, 16).toByteArray();
+      byte[] ivDataWithPadding = new byte[iv.length() / 2];
+      System.arraycopy(ivData, 0, ivDataWithPadding, ivDataWithPadding.length - ivData.length,
+          ivData.length);
+
+      encryptedDataSource = new Aes128DataSource(keyData, ivDataWithPadding, upstreamDataSource);
+    }
+
+  }
+
 }
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylist.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylist.java
index f118734def..8d7ff1bc61 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylist.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylist.java
@@ -30,10 +30,16 @@ public final class HlsMasterPlaylist {
   public static final class Variant {
     public final int bandwidth;
     public final String url;
+    public final String[] codecs;
+    public final int width;
+    public final int height;
 
-    public Variant(String url, int bandwidth) {
+    public Variant(String url, int bandwidth, String[] codecs, int width, int height) {
       this.bandwidth = bandwidth;
       this.url = url;
+      this.codecs = codecs;
+      this.width = width;
+      this.height = height;
     }
   }
 
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylistParser.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylistParser.java
index d00eecc28b..191ec06996 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylistParser.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsMasterPlaylistParser.java
@@ -36,9 +36,15 @@ public final class HlsMasterPlaylistParser implements ManifestParser<HlsMasterPl
 
   private static final String STREAM_INF_TAG = "#EXT-X-STREAM-INF";
   private static final String BANDWIDTH_ATTR = "BANDWIDTH";
+  private static final String CODECS_ATTR = "CODECS";
+  private static final String RESOLUTION_ATTR = "RESOLUTION";
 
   private static final Pattern BANDWIDTH_ATTR_REGEX =
       Pattern.compile(BANDWIDTH_ATTR + "=(\\d+)\\b");
+  private static final Pattern CODECS_ATTR_REGEX =
+      Pattern.compile(CODECS_ATTR + "=\"(.+)\"");
+  private static final Pattern RESOLUTION_ATTR_REGEX =
+      Pattern.compile(RESOLUTION_ATTR + "=(\\d+x\\d+)");
 
   @Override
   public HlsMasterPlaylist parse(InputStream inputStream, String inputEncoding,
@@ -52,6 +58,10 @@ public final class HlsMasterPlaylistParser implements ManifestParser<HlsMasterPl
         ? new InputStreamReader(inputStream) : new InputStreamReader(inputStream, inputEncoding));
     List<Variant> variants = new ArrayList<Variant>();
     int bandwidth = 0;
+    String[] codecs = null;
+    int width = -1;
+    int height = -1;
+
     String line;
     while ((line = reader.readLine()) != null) {
       line = line.trim();
@@ -60,9 +70,29 @@ public final class HlsMasterPlaylistParser implements ManifestParser<HlsMasterPl
       }
       if (line.startsWith(STREAM_INF_TAG)) {
         bandwidth = HlsParserUtil.parseIntAttr(line, BANDWIDTH_ATTR_REGEX, BANDWIDTH_ATTR);
+        String codecsString = HlsParserUtil.parseOptionalStringAttr(line, CODECS_ATTR_REGEX,
+            CODECS_ATTR);
+        if (codecsString != null) {
+          codecs = codecsString.split(",");
+        } else {
+          codecs = null;
+        }
+        String resolutionString = HlsParserUtil.parseOptionalStringAttr(line, RESOLUTION_ATTR_REGEX,
+            RESOLUTION_ATTR);
+        if (resolutionString != null) {
+          String[] widthAndHeight = resolutionString.split("x");
+          width = Integer.parseInt(widthAndHeight[0]);
+          height = Integer.parseInt(widthAndHeight[1]);
+        } else {
+          width = -1;
+          height = -1;
+        }
       } else if (!line.startsWith("#")) {
-        variants.add(new Variant(line, bandwidth));
+        variants.add(new Variant(line, bandwidth, codecs, width, height));
         bandwidth = 0;
+        codecs = null;
+        width = -1;
+        height = -1;
       }
     }
     return new HlsMasterPlaylist(baseUri, Collections.unmodifiableList(variants));
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylist.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylist.java
index e4631d42f6..7e8136cab3 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylist.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylist.java
@@ -32,12 +32,19 @@ public final class HlsMediaPlaylist {
     public final double durationSecs;
     public final String url;
     public final long startTimeUs;
+    public final String encryptionMethod;
+    public final String encryptionKeyUri;
+    public final String encryptionIV;
 
-    public Segment(String uri, double durationSecs, boolean discontinuity, long startTimeUs) {
+    public Segment(String uri, double durationSecs, boolean discontinuity, long startTimeUs,
+        String encryptionMethod, String encryptionKeyUri, String encryptionIV) {
       this.url = uri;
       this.durationSecs = durationSecs;
       this.discontinuity = discontinuity;
       this.startTimeUs = startTimeUs;
+      this.encryptionMethod = encryptionMethod;
+      this.encryptionKeyUri = encryptionKeyUri;
+      this.encryptionIV = encryptionIV;
     }
 
     @Override
@@ -46,6 +53,9 @@ public final class HlsMediaPlaylist {
     }
   }
 
+  public static final String ENCRYPTION_METHOD_NONE = "NONE";
+  public static final String ENCRYPTION_METHOD_AES_128 = "AES-128";
+
   public final Uri baseUri;
   public final int mediaSequence;
   public final int targetDurationSecs;
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylistParser.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylistParser.java
index d2d514c01e..a747ab19c9 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylistParser.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsMediaPlaylistParser.java
@@ -40,6 +40,11 @@ public final class HlsMediaPlaylistParser implements ManifestParser<HlsMediaPlay
   private static final String TARGET_DURATION_TAG = "#EXT-X-TARGETDURATION";
   private static final String VERSION_TAG = "#EXT-X-VERSION";
   private static final String ENDLIST_TAG = "#EXT-X-ENDLIST";
+  private static final String KEY_TAG = "#EXT-X-KEY";
+
+  private static final String METHOD_ATTR = "METHOD";
+  private static final String URI_ATTR = "URI";
+  private static final String IV_ATTR = "IV";
 
   private static final Pattern MEDIA_DURATION_REGEX =
       Pattern.compile(MEDIA_DURATION_TAG + ":([\\d.]+),");
@@ -50,6 +55,13 @@ public final class HlsMediaPlaylistParser implements ManifestParser<HlsMediaPlay
   private static final Pattern VERSION_REGEX =
       Pattern.compile(VERSION_TAG + ":(\\d+)\\b");
 
+  private static final Pattern METHOD_ATTR_REGEX =
+      Pattern.compile(METHOD_ATTR + "=([^,.*]+)");
+  private static final Pattern URI_ATTR_REGEX =
+      Pattern.compile(URI_ATTR + "=\"(.+)\"");
+  private static final Pattern IV_ATTR_REGEX =
+      Pattern.compile(IV_ATTR + "=([^,.*]+)");
+
   @Override
   public HlsMediaPlaylist parse(InputStream inputStream, String inputEncoding,
       String contentId, Uri baseUri) throws IOException {
@@ -70,6 +82,11 @@ public final class HlsMediaPlaylistParser implements ManifestParser<HlsMediaPlay
     double segmentDurationSecs = 0.0;
     boolean segmentDiscontinuity = false;
     long segmentStartTimeUs = 0;
+    String segmentEncryptionMethod = null;
+    String segmentEncryptionKeyUri = null;
+    String segmentEncryptionIV = null;
+
+    int segmentMediaSequence = 0;
 
     String line;
     while ((line = reader.readLine()) != null) {
@@ -82,16 +99,34 @@ public final class HlsMediaPlaylistParser implements ManifestParser<HlsMediaPlay
             TARGET_DURATION_TAG);
       } else if (line.startsWith(MEDIA_SEQUENCE_TAG)) {
         mediaSequence = HlsParserUtil.parseIntAttr(line, MEDIA_SEQUENCE_REGEX, MEDIA_SEQUENCE_TAG);
+        segmentMediaSequence = mediaSequence;
       } else if (line.startsWith(VERSION_TAG)) {
         version = HlsParserUtil.parseIntAttr(line, VERSION_REGEX, VERSION_TAG);
       } else if (line.startsWith(MEDIA_DURATION_TAG)) {
         segmentDurationSecs = HlsParserUtil.parseDoubleAttr(line, MEDIA_DURATION_REGEX,
             MEDIA_DURATION_TAG);
+      } else if (line.startsWith(KEY_TAG)) {
+        segmentEncryptionMethod = HlsParserUtil.parseStringAttr(line, METHOD_ATTR_REGEX,
+            METHOD_ATTR);
+        if (segmentEncryptionMethod.equals(HlsMediaPlaylist.ENCRYPTION_METHOD_NONE)) {
+          segmentEncryptionKeyUri = null;
+          segmentEncryptionIV = null;
+        } else {
+          segmentEncryptionKeyUri = HlsParserUtil.parseStringAttr(line, URI_ATTR_REGEX,
+              URI_ATTR);
+          segmentEncryptionIV = HlsParserUtil.parseOptionalStringAttr(line, IV_ATTR_REGEX,
+              IV_ATTR);
+          if (segmentEncryptionIV == null) {
+            segmentEncryptionIV = Integer.toHexString(segmentMediaSequence);
+          }
+        }
       } else if (line.equals(DISCONTINUITY_TAG)) {
         segmentDiscontinuity = true;
       } else if (!line.startsWith("#")) {
+        segmentMediaSequence++;
         segments.add(new Segment(line, segmentDurationSecs, segmentDiscontinuity,
-            segmentStartTimeUs));
+            segmentStartTimeUs, segmentEncryptionMethod, segmentEncryptionKeyUri,
+            segmentEncryptionIV));
         segmentStartTimeUs += (long) (segmentDurationSecs * 1000000);
         segmentDiscontinuity = false;
         segmentDurationSecs = 0.0;
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsParserUtil.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsParserUtil.java
index e61483f42c..2af5424aae 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsParserUtil.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsParserUtil.java
@@ -36,6 +36,14 @@ import java.util.regex.Pattern;
     throw new ParserException(String.format("Couldn't match %s tag in %s", tag, line));
   }
 
+  public static String parseOptionalStringAttr(String line, Pattern pattern, String tag) {
+    Matcher matcher = pattern.matcher(line);
+    if (matcher.find() && matcher.groupCount() == 1) {
+      return matcher.group(1);
+    }
+    return null;
+  }
+
   public static int parseIntAttr(String line, Pattern pattern, String tag)
       throws ParserException {
     return Integer.parseInt(parseStringAttr(line, pattern, tag));
diff --git a/library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java b/library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java
index 9a289f9209..f05d9cb8ec 100644
--- a/library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java
+++ b/library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java
@@ -184,10 +184,14 @@ public class HlsSampleSource implements SampleSource, Loader.Callback {
         haveSufficientSamples = true;
       } else {
         extractor.reset(mediaChunk.startTimeUs);
-        for (int i = 0; i < pendingDiscontinuities.length; i++) {
-          pendingDiscontinuities[i] = true;
-        }
         mediaChunk.clearPendingDiscontinuity();
+        if (pendingDiscontinuities == null) {
+          // We're not prepared yet.
+        } else {
+          for (int i = 0; i < pendingDiscontinuities.length; i++) {
+            pendingDiscontinuities[i] = true;
+          }
+        }
       }
     }
 
diff --git a/library/src/main/java/com/google/android/exoplayer/upstream/Aes128DataSource.java b/library/src/main/java/com/google/android/exoplayer/upstream/Aes128DataSource.java
new file mode 100644
index 0000000000..1e76d898b8
--- /dev/null
+++ b/library/src/main/java/com/google/android/exoplayer/upstream/Aes128DataSource.java
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2014 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.exoplayer.upstream;
+
+import com.google.android.exoplayer.C;
+import com.google.android.exoplayer.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 the data read from an upstream source, encrypted with AES-128
+ * with a 128-bit key and PKCS7 padding.
+ *
+ */
+public class Aes128DataSource implements DataSource {
+
+  private final DataSource upstream;
+  private final byte[] secretKey;
+  private final byte[] iv;
+
+  private Cipher cipher;
+  private CipherInputStream cipherInputStream;
+
+  public Aes128DataSource(byte[] secretKey, byte[] iv, DataSource upstream) {
+    this.upstream = upstream;
+    this.secretKey = secretKey;
+    this.iv = iv;
+  }
+
+  @Override
+  public long open(DataSpec dataSpec) throws IOException {
+    try {
+      cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
+    } catch (NoSuchAlgorithmException e) {
+      throw new RuntimeException(e);
+    } catch (NoSuchPaddingException e) {
+      throw new RuntimeException(e);
+    }
+
+    Key cipherKey = new SecretKeySpec(secretKey, "AES");
+    AlgorithmParameterSpec cipherIV = new IvParameterSpec(iv);
+
+    try {
+      cipher.init(Cipher.DECRYPT_MODE, cipherKey, cipherIV);
+    } catch (InvalidKeyException e) {
+      throw new RuntimeException(e);
+    } catch (InvalidAlgorithmParameterException e) {
+      throw new RuntimeException(e);
+    }
+
+    cipherInputStream = new CipherInputStream(
+        new DataSourceInputStream(upstream, dataSpec), cipher);
+
+    return C.LENGTH_UNBOUNDED;
+  }
+
+  @Override
+  public void close() throws IOException {
+    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 -1;
+    }
+    return bytesRead;
+  }
+
+}