110 lines
4.2 KiB
Java
110 lines
4.2 KiB
Java
/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.internal.telephony;
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import android.content.Context;
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import android.content.pm.PackageInfo;
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import android.content.pm.PackageManager;
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import android.content.pm.PackageManager.NameNotFoundException;
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import android.content.pm.Signature;
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import android.util.Base64;
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import android.util.Log;
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import java.nio.charset.Charset;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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import java.util.Arrays;
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import java.util.List;
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/** Utility class for generating token, i.e., hash of package name and certificate. */
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public class PackageBasedTokenUtil {
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private static final String TAG = "PackageBasedTokenUtil";
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private static final Charset CHARSET_UTF_8 = Charset.forName("UTF-8");
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private static final String HASH_TYPE = "SHA-256";
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private static final int NUM_HASHED_BYTES = 9; // 9 bytes = 72 bits = 12 Base64s
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static final int NUM_BASE64_CHARS = 11; // truncate 12 into 11 Base64 chars
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/**
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* Generate token and check collision with other packages.
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*/
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public static String generateToken(Context context, String packageName) {
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PackageManager packageManager = context.getPackageManager();
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String token = generatePackageBasedToken(packageManager, packageName);
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// Check for token confliction
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List<PackageInfo> packages =
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packageManager.getInstalledPackages(PackageManager.GET_META_DATA);
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for (PackageInfo packageInfo : packages) {
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String otherPackageName = packageInfo.packageName;
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if (packageName.equals(otherPackageName)) {
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continue;
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}
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String otherToken = generatePackageBasedToken(packageManager, otherPackageName);
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if (token.equals(otherToken)) {
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Log.e(TAG, "token collides with other installed app.");
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token = null;
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}
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}
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return token;
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}
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private static String generatePackageBasedToken(
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PackageManager packageManager, String packageName) {
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String token = null;
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Signature[] signatures;
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try {
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// It is actually a certificate (public key), not a signature.
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signatures = packageManager.getPackageInfo(
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packageName, PackageManager.GET_SIGNATURES).signatures;
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} catch (NameNotFoundException e) {
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Log.e(TAG, "Failed to find package with package name: " + packageName);
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return token;
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}
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if (signatures == null) {
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Log.e(TAG, "The certificates is missing.");
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} else {
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MessageDigest messageDigest;
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try {
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messageDigest = MessageDigest.getInstance(HASH_TYPE);
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} catch (NoSuchAlgorithmException e) {
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Log.e(TAG, "NoSuchAlgorithmException" + e);
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return null;
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}
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messageDigest.update(packageName.getBytes(CHARSET_UTF_8));
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String space = " ";
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messageDigest.update(space.getBytes(CHARSET_UTF_8));
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for (int i = 0; i < signatures.length; i++) {
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messageDigest.update(signatures[i].toCharsString().getBytes(CHARSET_UTF_8));
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}
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byte[] hashSignatures = messageDigest.digest();
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// truncated into NUM_HASHED_BYTES
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hashSignatures = Arrays.copyOf(hashSignatures, NUM_HASHED_BYTES);
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// encode into Base64
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token = Base64.encodeToString(hashSignatures, Base64.NO_PADDING | Base64.NO_WRAP);
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token = token.substring(0, NUM_BASE64_CHARS);
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}
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return token;
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}
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}
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