src/main/java/com/android/apksig/Hints.java

/*
 * Copyright (C) 2018 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.apksig;
import java.io.IOException;
import java.io.DataOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public final class Hints {
    /**
     * Name of hint pattern asset file in APK.
     */
    public static final String PIN_HINT_ASSET_ZIP_ENTRY_NAME = "assets/com.android.hints.pins.txt";

    /**
     * Name of hint byte range data file in APK.  Keep in sync with PinnerService.java.
     */
    public static final String PIN_BYTE_RANGE_ZIP_ENTRY_NAME = "pinlist.meta";

    private static int clampToInt(long value) {
        return (int) Math.max(0, Math.min(value, Integer.MAX_VALUE));
    }

    public static final class ByteRange {
        final long start;
        final long end;

        public ByteRange(long start, long end) {
            this.start = start;
            this.end = end;
        }
    }

    public static final class PatternWithRange {
        final Pattern pattern;
        final long offset;
        final long size;

        public PatternWithRange(String pattern) {
            this.pattern = Pattern.compile(pattern);
            this.offset= 0;
            this.size = Long.MAX_VALUE;
        }

        public PatternWithRange(String pattern, long offset, long size) {
            this.pattern = Pattern.compile(pattern);
            this.offset = offset;
            this.size = size;
        }

        public Matcher matcher(CharSequence input) {
            return this.pattern.matcher(input);
        }

        public ByteRange ClampToAbsoluteByteRange(ByteRange rangeIn) {
            if (rangeIn.end - rangeIn.start < this.offset) {
                return null;
            }
            long rangeOutStart = rangeIn.start + this.offset;
            long rangeOutSize = Math.min(rangeIn.end - rangeOutStart,
                                           this.size);
            return new ByteRange(rangeOutStart,
                                 rangeOutStart + rangeOutSize);
        }
    }

    /**
     * Create a blob of bytes that PinnerService understands as a
     * sequence of byte ranges to pin.
     */
    public static byte[] encodeByteRangeList(List<ByteRange> pinByteRanges) {
        ByteArrayOutputStream bos = new ByteArrayOutputStream(pinByteRanges.size() * 8);
        DataOutputStream out = new DataOutputStream(bos);
        try {
            for (ByteRange pinByteRange : pinByteRanges) {
                out.writeInt(clampToInt(pinByteRange.start));
                out.writeInt(clampToInt(pinByteRange.end - pinByteRange.start));
            }
        } catch (IOException ex) {
            throw new AssertionError("impossible", ex);
        }
        return bos.toByteArray();
    }

    public static ArrayList<PatternWithRange> parsePinPatterns(byte[] patternBlob) {
        ArrayList<PatternWithRange> pinPatterns = new ArrayList<>();
        try {
            for (String rawLine : new String(patternBlob, "UTF-8").split("\n")) {
                String line = rawLine.replaceFirst("#.*", "");  // # starts a comment
                String[] fields = line.split(" ");
                if (fields.length == 1) {
                    pinPatterns.add(new PatternWithRange(fields[0]));
                } else if (fields.length == 3) {
                    long start = Long.parseLong(fields[1]);
                    long end = Long.parseLong(fields[2]);
                    pinPatterns.add(new PatternWithRange(fields[0], start, end - start));
                } else {
                    throw new AssertionError("bad pin pattern line " + line);
                }
            }
        } catch (UnsupportedEncodingException ex) {
            throw new RuntimeException("UTF-8 must be supported", ex);
        }
        return pinPatterns;
    }
}