| /* |
| * 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.signflinger; |
| |
| import static java.nio.ByteOrder.LITTLE_ENDIAN; |
| |
| import com.android.apksig.apk.ApkSigningBlockNotFoundException; |
| import com.android.apksig.apk.ApkUtils; |
| import com.android.apksig.apk.ApkUtils.ApkSigningBlock; |
| import com.android.apksig.internal.apk.ApkSigningBlockUtils; |
| import com.android.apksig.internal.util.Pair; |
| import com.android.apksig.util.DataSource; |
| import com.android.apksig.util.DataSources; |
| import com.android.apksig.zip.ZipFormatException; |
| import java.io.File; |
| import java.io.IOException; |
| import java.io.RandomAccessFile; |
| import java.nio.ByteBuffer; |
| import java.nio.ByteOrder; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.List; |
| |
| /** Generates and appends a new block to APK v2 Signature block. */ |
| public final class SigningBlockUtils { |
| |
| private static final int MAGIC_NUM_BYTES = 16; |
| private static final int BLOCK_LENGTH_NUM_BYTES = 8; |
| static final int SIZE_OF_BLOCK_NUM_BYTES = 8; |
| static final int BLOCK_ID_NUM_BYTES = 4; |
| |
| static final int VERITY_PADDING_BLOCK_ID = 0x42726577; |
| |
| /** |
| * Generates a new block with the given block value and block id, and appends it to the signing |
| * block. |
| * |
| * @param signingBlock Block containing v2 signature and (optionally) padding block or null. |
| * @param blockValue byte array containing block value of the new block or null. |
| * @param blockId block id of the new block. |
| * @return APK v2 block with signatures and the new block. If {@code blockValue} is null the |
| * {@code signingBlock} is returned without any modification. If {@code signingBlock} is |
| * null, a new signature block is created containing the new block and, optionally, padding |
| * block. |
| */ |
| public static byte[] addToSigningBlock(byte[] signingBlock, byte[] blockValue, int blockId) |
| throws IOException { |
| if (blockValue == null || blockValue.length == 0) { |
| return signingBlock; |
| } |
| if (signingBlock == null || signingBlock.length == 0) { |
| return createSigningBlock(blockValue, blockId); |
| } |
| return appendToSigningBlock(signingBlock, blockValue, blockId); |
| } |
| |
| /** |
| * Adds a new block to the signature block and a padding block, if required. |
| * |
| * @param signingBlock APK v2 signing block containing : length prefix, signers (can include |
| * padding block), length postfix and APK sig v2 block magic. |
| * @param blockValue byte array containing block value of the new block. |
| * @param blockId block id of the new block. |
| * @return APK v2 signing block containing : length prefix, signers including the new block (may |
| * include padding block as well), length postfix and APK sig v2 block magic. |
| */ |
| private static byte[] appendToSigningBlock(byte[] signingBlock, byte[] blockValue, int blockId) |
| throws IOException { |
| List<Pair<byte[], Integer>> entries = |
| new ArrayList<>( |
| extractAllSigners(DataSources.asDataSource(ByteBuffer.wrap(signingBlock)))); |
| entries.add(Pair.of(blockValue, blockId)); |
| return ApkSigningBlockUtils.generateApkSigningBlock(entries); |
| } |
| |
| /** |
| * Generate APK sig v2 block containing a block composed of the provided block value and id, and |
| * (optionally) padding block. |
| */ |
| private static byte[] createSigningBlock(byte[] blockValue, int blockId) { |
| return ApkSigningBlockUtils.generateApkSigningBlock( |
| Arrays.asList(Pair.of(blockValue, blockId))); |
| } |
| |
| /** |
| * Extracts all signing block entries except padding block. |
| * |
| * @param signingBlock APK v2 signing block containing: length prefix, signers (can include |
| * padding block), length postfix and APK sig v2 block magic. |
| * @return list of block entry value and block entry id pairs. |
| */ |
| private static List<Pair<byte[], Integer>> extractAllSigners(DataSource signingBlock) |
| throws IOException { |
| long wholeBlockSize = signingBlock.size(); |
| // Take the segment of the existing signing block without the length prefix (8 bytes) |
| // at the beginning and the length and magic (24 bytes) at the end, so it is just the |
| // sequence |
| // of length prefix id value pairs. |
| DataSource lengthPrefixedIdValuePairsSource = |
| signingBlock.slice( |
| SIZE_OF_BLOCK_NUM_BYTES, |
| wholeBlockSize - 2 * SIZE_OF_BLOCK_NUM_BYTES - MAGIC_NUM_BYTES); |
| final int lengthAndIdByteCount = BLOCK_LENGTH_NUM_BYTES + BLOCK_ID_NUM_BYTES; |
| ByteBuffer lengthAndId = ByteBuffer.allocate(lengthAndIdByteCount).order(LITTLE_ENDIAN); |
| List<Pair<byte[], Integer>> idValuePairs = new ArrayList<>(); |
| |
| for (int index = 0; |
| index <= lengthPrefixedIdValuePairsSource.size() - lengthAndIdByteCount; ) { |
| lengthPrefixedIdValuePairsSource.copyTo(index, lengthAndIdByteCount, lengthAndId); |
| lengthAndId.flip(); |
| int blockLength = Math.toIntExact(lengthAndId.getLong()); |
| int id = lengthAndId.getInt(); |
| lengthAndId.clear(); |
| |
| if (id != VERITY_PADDING_BLOCK_ID) { |
| int blockValueSize = blockLength - BLOCK_ID_NUM_BYTES; |
| ByteBuffer blockValue = ByteBuffer.allocate(blockValueSize); |
| lengthPrefixedIdValuePairsSource.copyTo( |
| index + BLOCK_LENGTH_NUM_BYTES + BLOCK_ID_NUM_BYTES, |
| blockValueSize, |
| blockValue); |
| idValuePairs.add(Pair.of(blockValue.array(), id)); |
| } |
| |
| index += blockLength + BLOCK_LENGTH_NUM_BYTES; |
| } |
| return idValuePairs; |
| } |
| |
| /** |
| * Extract a block with the given id from the APK. If there is more than one block with the same |
| * ID, the first block will be returned. If there are no block with the give id, {@code null} |
| * will be returned. |
| * |
| * @param apk APK file |
| * @param blockId id of the block to be extracted. |
| */ |
| public static ByteBuffer extractBlock(File apk, int blockId) |
| throws IOException, ZipFormatException, ApkSigningBlockNotFoundException { |
| try (RandomAccessFile file = new RandomAccessFile(apk, "r")) { |
| DataSource apkDataSource = DataSources.asDataSource(file); |
| ApkSigningBlock signingBlockInfo = |
| ApkUtils.findApkSigningBlock( |
| apkDataSource, ApkUtils.findZipSections(apkDataSource)); |
| |
| DataSource wholeV2Block = signingBlockInfo.getContents(); |
| final int lengthAndIdByteCount = BLOCK_LENGTH_NUM_BYTES + BLOCK_ID_NUM_BYTES; |
| DataSource signingBlock = |
| wholeV2Block.slice( |
| SIZE_OF_BLOCK_NUM_BYTES, |
| wholeV2Block.size() - SIZE_OF_BLOCK_NUM_BYTES - MAGIC_NUM_BYTES); |
| ByteBuffer lengthAndId = |
| ByteBuffer.allocate(lengthAndIdByteCount).order(ByteOrder.LITTLE_ENDIAN); |
| for (int index = 0; index <= signingBlock.size() - lengthAndIdByteCount; ) { |
| signingBlock.copyTo(index, lengthAndIdByteCount, lengthAndId); |
| lengthAndId.flip(); |
| int blockLength = (int) lengthAndId.getLong(); |
| int id = lengthAndId.getInt(); |
| lengthAndId.flip(); |
| if (id == blockId) { |
| ByteBuffer block = ByteBuffer.allocate(blockLength - BLOCK_ID_NUM_BYTES); |
| signingBlock.copyTo( |
| index + lengthAndIdByteCount, blockLength - BLOCK_ID_NUM_BYTES, block); |
| block.flip(); |
| return block; |
| } |
| index += blockLength + BLOCK_LENGTH_NUM_BYTES; |
| } |
| return null; |
| } |
| } |
| |
| private SigningBlockUtils() {} |
| } |