Work around incorrect ClearKey encoding prior to O-MR1

Issue: #3138

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=175006223

library/core/src/main/java/com/google/android/exoplayer2/drm/ClearKeyUtil.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2017 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.drm;
+
+import android.util.Log;
+import com.google.android.exoplayer2.util.Util;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/**
+ * Utility methods for ClearKey.
+ */
+/* package */ final class ClearKeyUtil {
+
+  private static final String TAG = "ClearKeyUtil";
+  private static final Pattern REQUEST_KIDS_PATTERN = Pattern.compile("\"kids\":\\[\"(.*?)\"]");
+
+  private ClearKeyUtil() {}
+
+  /**
+   * Adjusts ClearKey request data obtained from the Android ClearKey CDM to be spec compliant.
+   *
+   * @param request The request data.
+   * @return The adjusted request data.
+   */
+  public static byte[] adjustRequestData(byte[] request) {
+    if (Util.SDK_INT >= 27) {
+      return request;
+    }
+    // Prior to O-MR1 the ClearKey CDM encoded the values in the "kids" array using Base64 rather
+    // than Base64Url. See [Internal: b/64388098]. Any "/" characters that ended up in the request
+    // as a result were not escaped as "\/". We know the exact request format from the platform's
+    // InitDataParser.cpp, so we can use a regexp rather than parsing the JSON.
+    String requestString = Util.fromUtf8Bytes(request);
+    Matcher requestKidsMatcher = REQUEST_KIDS_PATTERN.matcher(requestString);
+    if (!requestKidsMatcher.find()) {
+      Log.e(TAG, "Failed to adjust request data: " + requestString);
+      return request;
+    }
+    int kidsStartIndex = requestKidsMatcher.start(1);
+    int kidsEndIndex = requestKidsMatcher.end(1);
+    StringBuilder adjustedRequestBuilder = new StringBuilder(requestString);
+    base64ToBase64Url(adjustedRequestBuilder, kidsStartIndex, kidsEndIndex);
+    return Util.getUtf8Bytes(adjustedRequestBuilder.toString());
+  }
+
+  /**
+   * Adjusts ClearKey response data to be suitable for providing to the Android ClearKey CDM.
+   *
+   * @param response The response data.
+   * @return The adjusted response data.
+   */
+  public static byte[] adjustResponseData(byte[] response) {
+    if (Util.SDK_INT >= 27) {
+      return response;
+    }
+    // Prior to O-MR1 the ClearKey CDM expected Base64 encoding rather than Base64Url encoding for
+    // the "k" and "kid" strings. See [Internal: b/64388098].
+    try {
+      JSONObject responseJson = new JSONObject(Util.fromUtf8Bytes(response));
+      JSONArray keysArray = responseJson.getJSONArray("keys");
+      for (int i = 0; i < keysArray.length(); i++) {
+        JSONObject key = keysArray.getJSONObject(i);
+        key.put("k", base64UrlToBase64(key.getString("k")));
+        key.put("kid", base64UrlToBase64(key.getString("kid")));
+      }
+      return Util.getUtf8Bytes(responseJson.toString());
+    } catch (JSONException e) {
+      Log.e(TAG, "Failed to adjust response data: " + Util.fromUtf8Bytes(response), e);
+      return response;
+    }
+  }
+
+  private static void base64ToBase64Url(StringBuilder base64, int startIndex, int endIndex) {
+    for (int i = startIndex; i < endIndex; i++) {
+      switch (base64.charAt(i)) {
+        case '+':
+          base64.setCharAt(i, '-');
+          break;
+        case '/':
+          base64.setCharAt(i, '_');
+          break;
+        default:
+          break;
+      }
+    }
+  }
+
+  private static String base64UrlToBase64(String base64) {
+    return base64.replace('-', '+').replace('_', '/');
+  }
+
+}

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSession.java

@@ -362,6 +362,20 @@ import java.util.UUID;
     try {
       KeyRequest request = mediaDrm.getKeyRequest(scope, initData, mimeType, type,
           optionalKeyRequestParameters);
+      if (C.CLEARKEY_UUID.equals(uuid)) {
+        final byte[] data = ClearKeyUtil.adjustRequestData(request.getData());
+        final String defaultUrl = request.getDefaultUrl();
+        request = new KeyRequest() {
+          @Override
+          public byte[] getData() {
+            return data;
+          }
+          @Override
+          public String getDefaultUrl() {
+            return defaultUrl;
+          }
+        };
+      }
       postRequestHandler.obtainMessage(MSG_KEYS, request, allowRetry).sendToTarget();
     } catch (Exception e) {
       onKeysError(e);
@@ -380,8 +394,12 @@ import java.util.UUID;
     }
 
     try {
+      byte[] responseData = (byte[]) response;
+      if (C.CLEARKEY_UUID.equals(uuid)) {
+        responseData = ClearKeyUtil.adjustResponseData(responseData);
+      }
       if (mode == DefaultDrmSessionManager.MODE_RELEASE) {
-        mediaDrm.provideKeyResponse(offlineLicenseKeySetId, (byte[]) response);
+        mediaDrm.provideKeyResponse(offlineLicenseKeySetId, responseData);
         if (eventHandler != null && eventListener != null) {
           eventHandler.post(new Runnable() {
             @Override
@@ -391,7 +409,7 @@ import java.util.UUID;
           });
         }
       } else {
-        byte[] keySetId = mediaDrm.provideKeyResponse(sessionId, (byte[]) response);
+        byte[] keySetId = mediaDrm.provideKeyResponse(sessionId, responseData);
         if ((mode == DefaultDrmSessionManager.MODE_DOWNLOAD
             || (mode == DefaultDrmSessionManager.MODE_PLAYBACK && offlineLicenseKeySetId != null))
             && keySetId != null && keySetId.length != 0) {

library/core/src/main/java/com/google/android/exoplayer2/drm/FrameworkMediaDrm.java

@@ -25,6 +25,7 @@ import android.media.MediaDrmException;
 import android.media.NotProvisionedException;
 import android.media.UnsupportedSchemeException;
 import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
@@ -74,7 +75,7 @@ public final class FrameworkMediaDrm implements ExoMediaDrm<FrameworkMediaCrypto
       final ExoMediaDrm.OnEventListener<? super FrameworkMediaCrypto> listener) {
     mediaDrm.setOnEventListener(listener == null ? null : new MediaDrm.OnEventListener() {
       @Override
-      public void onEvent(@NonNull MediaDrm md, @NonNull byte[] sessionId, int event, int extra,
+      public void onEvent(@NonNull MediaDrm md, @Nullable byte[] sessionId, int event, int extra,
           byte[] data) {
         listener.onEvent(FrameworkMediaDrm.this, sessionId, event, extra, data);
       }

library/core/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -246,6 +246,16 @@ public final class Util {
     return language == null ? null : new Locale(language).getLanguage();
   }
 
+  /**
+   * Returns a new {@link String} constructed by decoding UTF-8 encoded bytes.
+   *
+   * @param bytes The UTF-8 encoded bytes to decode.
+   * @return The string.
+   */
+  public static String fromUtf8Bytes(byte[] bytes) {
+    return new String(bytes, Charset.forName(C.UTF8_NAME));
+  }
+
   /**
    * Returns a new byte array containing the code points of a {@link String} encoded using UTF-8.
    *

library/core/src/test/java/com/google/android/exoplayer2/drm/ClearKeyUtilTest.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2017 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.drm;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.android.exoplayer2.C;
+import java.nio.charset.Charset;
+import java.util.Arrays;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+/**
+ * Unit test for {@link ClearKeyUtil}.
+ */
+// TODO: When API level 27 is supported, add tests that check the adjust methods are no-ops.
+@RunWith(RobolectricTestRunner.class)
+public final class ClearKeyUtilTest {
+
+  @Config(sdk = 26, manifest = Config.NONE)
+  @Test
+  public void testAdjustResponseDataV26() {
+    byte[] data = ("{\"keys\":[{"
+        + "\"k\":\"abc_def-\","
+        + "\"kid\":\"ab_cde-f\"}],"
+        + "\"type\":\"abc_def-"
+        + "\"}").getBytes(Charset.forName(C.UTF8_NAME));
+    // We expect "-" and "_" to be replaced with "+" and "\/" (forward slashes need to be escaped in
+    // JSON respectively, for "k" and "kid" only.
+    byte[] expected = ("{\"keys\":[{"
+        + "\"k\":\"abc\\/def+\","
+        + "\"kid\":\"ab\\/cde+f\"}],"
+        + "\"type\":\"abc_def-"
+        + "\"}").getBytes(Charset.forName(C.UTF8_NAME));
+    assertThat(Arrays.equals(expected, ClearKeyUtil.adjustResponseData(data))).isTrue();
+  }
+
+  @Config(sdk = 26, manifest = Config.NONE)
+  @Test
+  public void testAdjustRequestDataV26() {
+    byte[] data = "{\"kids\":[\"abc+def/\",\"ab+cde/f\"],\"type\":\"abc+def/\"}"
+        .getBytes(Charset.forName(C.UTF8_NAME));
+    // We expect "+" and "/" to be replaced with "-" and "_" respectively, for "kids".
+    byte[] expected = "{\"kids\":[\"abc-def_\",\"ab-cde_f\"],\"type\":\"abc+def/\"}"
+        .getBytes(Charset.forName(C.UTF8_NAME));
+    assertThat(Arrays.equals(expected, ClearKeyUtil.adjustRequestData(data))).isTrue();
+  }
+
+}