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/*
* 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.apksig.internal.apk.v4;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
public class V4Signature {
public static final int CURRENT_VERSION = 2;
public static final int HASHING_ALGORITHM_SHA256 = 1;
public static final byte LOG2_BLOCK_SIZE_4096_BYTES = 12;
public static class HashingInfo {
public final int hashAlgorithm; // only 1 == SHA256 supported
public final byte log2BlockSize; // only 12 (block size 4096) supported now
public final byte[] salt; // used exactly as in fs-verity, 32 bytes max
public final byte[] rawRootHash; // salted digest of the first Merkle tree page
HashingInfo(int hashAlgorithm, byte log2BlockSize, byte[] salt, byte[] rawRootHash) {
this.hashAlgorithm = hashAlgorithm;
this.log2BlockSize = log2BlockSize;
this.salt = salt;
this.rawRootHash = rawRootHash;
}
static HashingInfo fromByteArray(byte[] bytes) throws IOException {
ByteBuffer buffer = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN);
final int hashAlgorithm = buffer.getInt();
final byte log2BlockSize = buffer.get();
byte[] salt = readBytes(buffer);
byte[] rawRootHash = readBytes(buffer);
return new HashingInfo(hashAlgorithm, log2BlockSize, salt, rawRootHash);
}
byte[] toByteArray() {
final int size = 4/*hashAlgorithm*/ + 1/*log2BlockSize*/ + bytesSize(this.salt)
+ bytesSize(this.rawRootHash);
ByteBuffer buffer = ByteBuffer.allocate(size).order(ByteOrder.LITTLE_ENDIAN);
buffer.putInt(this.hashAlgorithm);
buffer.put(this.log2BlockSize);
writeBytes(buffer, this.salt);
writeBytes(buffer, this.rawRootHash);
return buffer.array();
}
}
public static class SigningInfo {
public final byte[] apkDigest; // used to match with the corresponding APK
public final byte[] certificate; // ASN.1 DER form
public final byte[] additionalData; // a free-form binary data blob
public final byte[] publicKey; // ASN.1 DER, must match the certificate
public final int signatureAlgorithmId; // see the APK v2 doc for the list
public final byte[] signature;
SigningInfo(byte[] apkDigest, byte[] certificate, byte[] additionalData,
byte[] publicKey, int signatureAlgorithmId, byte[] signature) {
this.apkDigest = apkDigest;
this.certificate = certificate;
this.additionalData = additionalData;
this.publicKey = publicKey;
this.signatureAlgorithmId = signatureAlgorithmId;
this.signature = signature;
}
static SigningInfo fromByteArray(byte[] bytes) throws IOException {
ByteBuffer buffer = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN);
byte[] apkDigest = readBytes(buffer);
byte[] certificate = readBytes(buffer);
byte[] additionalData = readBytes(buffer);
byte[] publicKey = readBytes(buffer);
int signatureAlgorithmId = buffer.getInt();
byte[] signature = readBytes(buffer);
return new SigningInfo(apkDigest, certificate, additionalData, publicKey,
signatureAlgorithmId, signature);
}
byte[] toByteArray() {
final int size = bytesSize(this.apkDigest) + bytesSize(this.certificate) + bytesSize(
this.additionalData) + bytesSize(this.publicKey) + 4/*signatureAlgorithmId*/
+ bytesSize(this.signature);
ByteBuffer buffer = ByteBuffer.allocate(size).order(ByteOrder.LITTLE_ENDIAN);
writeBytes(buffer, this.apkDigest);
writeBytes(buffer, this.certificate);
writeBytes(buffer, this.additionalData);
writeBytes(buffer, this.publicKey);
buffer.putInt(this.signatureAlgorithmId);
writeBytes(buffer, this.signature);
return buffer.array();
}
}
public final int version; // Always 2 for now.
public final byte[] hashingInfo;
public final byte[] signingInfo; // Passed as-is to the kernel. Can be retrieved later.
V4Signature(int version, byte[] hashingInfo, byte[] signingInfo) {
this.version = version;
this.hashingInfo = hashingInfo;
this.signingInfo = signingInfo;
}
static V4Signature readFrom(InputStream stream) throws IOException {
final int version = readIntLE(stream);
if (version != CURRENT_VERSION) {
throw new IOException("Invalid signature version.");
}
final byte[] hashingInfo = readBytes(stream);
final byte[] signingInfo = readBytes(stream);
return new V4Signature(version, hashingInfo, signingInfo);
}
public void writeTo(OutputStream stream) throws IOException {
writeIntLE(stream, this.version);
writeBytes(stream, this.hashingInfo);
writeBytes(stream, this.signingInfo);
}
static byte[] getSignedData(long fileSize, HashingInfo hashingInfo, SigningInfo signingInfo) {
final int size =
4/*size*/ + 8/*fileSize*/ + 4/*hash_algorithm*/ + 1/*log2_blocksize*/ + bytesSize(
hashingInfo.salt) + bytesSize(hashingInfo.rawRootHash) + bytesSize(
signingInfo.apkDigest) + bytesSize(signingInfo.certificate) + bytesSize(
signingInfo.additionalData);
ByteBuffer buffer = ByteBuffer.allocate(size).order(ByteOrder.LITTLE_ENDIAN);
buffer.putInt(size);
buffer.putLong(fileSize);
buffer.putInt(hashingInfo.hashAlgorithm);
buffer.put(hashingInfo.log2BlockSize);
writeBytes(buffer, hashingInfo.salt);
writeBytes(buffer, hashingInfo.rawRootHash);
writeBytes(buffer, signingInfo.apkDigest);
writeBytes(buffer, signingInfo.certificate);
writeBytes(buffer, signingInfo.additionalData);
return buffer.array();
}
// Utility methods.
static int bytesSize(byte[] bytes) {
return 4/*length*/ + (bytes == null ? 0 : bytes.length);
}
static void readFully(InputStream stream, byte[] buffer) throws IOException {
int len = buffer.length;
int n = 0;
while (n < len) {
int count = stream.read(buffer, n, len - n);
if (count < 0) {
throw new EOFException();
}
n += count;
}
}
static int readIntLE(InputStream stream) throws IOException {
final byte[] buffer = new byte[4];
readFully(stream, buffer);
return ByteBuffer.wrap(buffer).order(ByteOrder.LITTLE_ENDIAN).getInt();
}
static void writeIntLE(OutputStream stream, int v) throws IOException {
final byte[] buffer = ByteBuffer.wrap(new byte[4]).order(ByteOrder.LITTLE_ENDIAN).putInt(v).array();
stream.write(buffer);
}
static byte[] readBytes(InputStream stream) throws IOException {
try {
final int size = readIntLE(stream);
final byte[] bytes = new byte[size];
readFully(stream, bytes);
return bytes;
} catch (EOFException ignored) {
return null;
}
}
static byte[] readBytes(ByteBuffer buffer) throws IOException {
if (buffer.remaining() < 4) {
throw new EOFException();
}
final int size = buffer.getInt();
if (buffer.remaining() < size) {
throw new EOFException();
}
final byte[] bytes = new byte[size];
buffer.get(bytes);
return bytes;
}
static void writeBytes(OutputStream stream, byte[] bytes) throws IOException {
if (bytes == null) {
writeIntLE(stream, 0);
return;
}
writeIntLE(stream, bytes.length);
stream.write(bytes);
}
static void writeBytes(ByteBuffer buffer, byte[] bytes) {
if (bytes == null) {
buffer.putInt(0);
return;
}
buffer.putInt(bytes.length);
buffer.put(bytes);
}
}
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