Pull cacheinvalidations code directory into chromium repo.

third_party/cacheinvalidation/src/java/com/google/ipc/invalidation/ticl/PersistenceUtils.java

+/*
+ * Copyright 2011 Google Inc.
+ *
+ * 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.ipc.invalidation.ticl;
+
+import com.google.ipc.invalidation.common.DigestFunction;
+import com.google.ipc.invalidation.external.client.SystemResources.Logger;
+import com.google.ipc.invalidation.ticl.proto.Client.PersistentStateBlob;
+import com.google.ipc.invalidation.ticl.proto.Client.PersistentTiclState;
+import com.google.ipc.invalidation.util.Bytes;
+import com.google.ipc.invalidation.util.ProtoWrapper.ValidationException;
+import com.google.ipc.invalidation.util.TypedUtil;
+
+/**
+ * Utility methods for handling the Ticl persistent state.
+ *
+ */
+public class PersistenceUtils {
+
+  /** Serializes a Ticl state blob. */
+  public static byte[] serializeState(
+      PersistentTiclState state, DigestFunction digestFn) {
+    Bytes mac = generateMac(state, digestFn);
+    return PersistentStateBlob.create(state, mac).toByteArray();
+  }
+
+  /**
+   * Deserializes a Ticl state blob. Returns either the parsed state or {@code null}
+   * if it could not be parsed.
+   */
+  public static PersistentTiclState deserializeState(Logger logger, byte[] stateBlobBytes,
+      DigestFunction digestFn) {
+    PersistentStateBlob stateBlob;
+    try {
+      // Try parsing the envelope protocol buffer.
+      stateBlob = PersistentStateBlob.parseFrom(stateBlobBytes);
+    } catch (ValidationException exception) {
+      logger.severe("Failed deserializing Ticl state: %s", exception.getMessage());
+      return null;
+    }
+
+    // Check the mac in the envelope against the recomputed mac from the state.
+    PersistentTiclState ticlState = stateBlob.getTiclState();
+    Bytes mac = generateMac(ticlState, digestFn);
+    if (!TypedUtil.<Bytes>equals(mac, stateBlob.getAuthenticationCode())) {
+      logger.warning("Ticl state failed MAC check: computed %s vs %s", mac,
+          stateBlob.getAuthenticationCode());
+      return null;
+    }
+    return ticlState;
+  }
+
+  /** Returns a message authentication code over {@code state}. */
+  private static Bytes generateMac(PersistentTiclState state, DigestFunction digestFn) {
+    digestFn.reset();
+    digestFn.update(state.toByteArray());
+    return new Bytes(digestFn.getDigest());
+  }
+
+  private PersistenceUtils() {
+    // Prevent instantiation.
+  }
+}