1/*
2 * Copyright 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17
18package com.android.server.net.watchlist;
19
20import android.annotation.Nullable;
21import android.util.Log;
22import android.util.proto.ProtoOutputStream;
23
24import com.android.internal.annotations.VisibleForTesting;
25import com.android.internal.util.HexDump;
26import com.android.service.NetworkWatchlistReportProto;
27import com.android.service.NetworkWatchlistAppResultProto;
28
29import java.io.ByteArrayOutputStream;
30import java.util.ArrayList;
31import java.util.Collections;
32import java.util.List;
33import java.util.Map;
34
35/**
36 * Helper class to encode and generate serialized DP encoded watchlist proto report.
37 */
38class ReportEncoder {
39
40    private static final String TAG = "ReportEncoder";
41
42    // Report version number, as file format / parameters can be changed in later version, we need
43    // to have versioning on watchlist report format
44    private static final int REPORT_VERSION = 1;
45
46    private static final int WATCHLIST_HASH_SIZE = 32;
47
48    /**
49     * Apply DP on watchlist results, and generate a serialized watchlist report ready to store
50     * in DropBox.
51     */
52    @Nullable
53    static byte[] encodeWatchlistReport(WatchlistConfig config, byte[] userSecret,
54            List<String> appDigestList, WatchlistReportDbHelper.AggregatedResult aggregatedResult) {
55        Map<String, Boolean> resultMap = PrivacyUtils.createDpEncodedReportMap(
56                config.isConfigSecure(), userSecret, appDigestList, aggregatedResult);
57        return serializeReport(config, resultMap);
58    }
59
60    /**
61     * Convert DP encoded watchlist report into proto format.
62     *
63     * @param encodedReportMap DP encoded watchlist report.
64     * @return Watchlist report in proto format, which will be shared in Dropbox. Null if
65     * watchlist report cannot be generated.
66     */
67    @Nullable
68    @VisibleForTesting
69    static byte[] serializeReport(WatchlistConfig config,
70            Map<String, Boolean> encodedReportMap) {
71        // TODO: Handle watchlist config changed case
72        final byte[] watchlistHash = config.getWatchlistConfigHash();
73        if (watchlistHash == null) {
74            Log.e(TAG, "No watchlist hash");
75            return null;
76        }
77        if (watchlistHash.length != WATCHLIST_HASH_SIZE) {
78            Log.e(TAG, "Unexpected hash length");
79            return null;
80        }
81        final ByteArrayOutputStream reportOutputStream = new ByteArrayOutputStream();
82        final ProtoOutputStream proto = new ProtoOutputStream(reportOutputStream);
83
84        // Set report version to report
85        proto.write(NetworkWatchlistReportProto.REPORT_VERSION, REPORT_VERSION);
86        proto.write(NetworkWatchlistReportProto.WATCHLIST_CONFIG_HASH,
87                HexDump.toHexString(watchlistHash));
88
89        // Set app digest, encoded_isPha pair to report
90        for (Map.Entry<String, Boolean> entry : encodedReportMap.entrySet()) {
91            String key = entry.getKey();
92            byte[] digest = HexDump.hexStringToByteArray(key);
93            boolean encodedResult = entry.getValue();
94            long token = proto.start(NetworkWatchlistReportProto.APP_RESULT);
95            proto.write(NetworkWatchlistAppResultProto.APP_DIGEST, key);
96            proto.write(NetworkWatchlistAppResultProto.ENCODED_RESULT, encodedResult);
97            proto.end(token);
98        }
99        proto.flush();
100        return reportOutputStream.toByteArray();
101    }
102}
103