services/core/java/com/android/server/integrity/parser/RuleIndexingController.java

/*
 * Copyright (C) 2020 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.android.server.integrity.parser;

import static com.android.server.integrity.model.IndexingFileConstants.END_INDEXING_KEY;
import static com.android.server.integrity.model.IndexingFileConstants.START_INDEXING_KEY;
import static com.android.server.integrity.parser.BinaryFileOperations.getIntValue;
import static com.android.server.integrity.parser.BinaryFileOperations.getStringValue;

import android.content.integrity.AppInstallMetadata;

import com.android.server.integrity.model.BitInputStream;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;

/** Helper class to identify the necessary indexes that needs to be read. */
public class RuleIndexingController {

    private static LinkedHashMap<String, Integer> sPackageNameBasedIndexes;
    private static LinkedHashMap<String, Integer> sAppCertificateBasedIndexes;
    private static LinkedHashMap<String, Integer> sUnindexedRuleIndexes;

    /**
     * Provide the indexing file to read and the object will be constructed by reading and
     * identifying the indexes.
     */
    public RuleIndexingController(InputStream inputStream) throws IOException {
        BitInputStream bitInputStream = new BitInputStream(inputStream);
        sPackageNameBasedIndexes = getNextIndexGroup(bitInputStream);
        sAppCertificateBasedIndexes = getNextIndexGroup(bitInputStream);
        sUnindexedRuleIndexes = getNextIndexGroup(bitInputStream);
    }

    /**
     * Returns a list of integers with the starting and ending bytes of the rules that needs to be
     * read and evaluated.
     */
    public List<RuleIndexRange> identifyRulesToEvaluate(AppInstallMetadata appInstallMetadata) {
        ArrayList<RuleIndexRange> indexRanges = new ArrayList();

        // Add the range for package name indexes rules.
        indexRanges.add(
                searchIndexingKeysRangeContainingKey(
                        sPackageNameBasedIndexes, appInstallMetadata.getPackageName()));

        // Add the range for app certificate indexes rules.
        indexRanges.add(
                searchIndexingKeysRangeContainingKey(
                        sAppCertificateBasedIndexes, appInstallMetadata.getAppCertificate()));

        // Add the range for unindexed rules.
        indexRanges.add(
                new RuleIndexRange(
                        sUnindexedRuleIndexes.get(START_INDEXING_KEY),
                        sUnindexedRuleIndexes.get(END_INDEXING_KEY)));

        return indexRanges;
    }

    private LinkedHashMap<String, Integer> getNextIndexGroup(BitInputStream bitInputStream)
            throws IOException {
        LinkedHashMap<String, Integer> keyToIndexMap = new LinkedHashMap<>();
        while (bitInputStream.hasNext()) {
            String key = getStringValue(bitInputStream);
            int value = getIntValue(bitInputStream);

            keyToIndexMap.put(key, value);

            if (key.matches(END_INDEXING_KEY)) {
                break;
            }
        }
        return keyToIndexMap;
    }

    private RuleIndexRange searchIndexingKeysRangeContainingKey(
            LinkedHashMap<String, Integer> indexMap, String searchedKey) {
        TreeSet<String> keyTreeSet =
                indexMap.keySet().stream()
                        .filter(key -> !key.matches(START_INDEXING_KEY) && !key.matches(
                                END_INDEXING_KEY))
                        .collect(Collectors.toCollection(TreeSet::new));

        String minIndex = keyTreeSet.floor(searchedKey);
        String maxIndex = keyTreeSet.ceiling(searchedKey);

        return new RuleIndexRange(
                indexMap.get(minIndex == null ? START_INDEXING_KEY : minIndex),
                indexMap.get(maxIndex == null ? END_INDEXING_KEY : maxIndex));
    }
}