| /* |
| * Copyright (C) 2016 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.backup; |
| |
| import android.content.pm.ApplicationInfo; |
| import android.content.pm.PackageInfo; |
| import android.content.pm.PackageManagerInternal; |
| import android.content.pm.Signature; |
| import android.content.pm.SigningInfo; |
| import android.util.Slog; |
| |
| import com.android.internal.util.ArrayUtils; |
| |
| import java.security.MessageDigest; |
| import java.security.NoSuchAlgorithmException; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.List; |
| |
| public class BackupUtils { |
| private static final String TAG = "BackupUtils"; |
| |
| private static final boolean DEBUG = false; |
| |
| public static boolean signaturesMatch(ArrayList<byte[]> storedSigHashes, PackageInfo target, |
| PackageManagerInternal pmi) { |
| if (target == null || target.packageName == null) { |
| return false; |
| } |
| // If the target resides on the system partition, we allow it to restore |
| // data from the like-named package in a restore set even if the signatures |
| // do not match. (Unlike general applications, those flashed to the system |
| // partition will be signed with the device's platform certificate, so on |
| // different phones the same system app will have different signatures.) |
| if ((target.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0) { |
| if (DEBUG) Slog.v(TAG, "System app " + target.packageName + " - skipping sig check"); |
| return true; |
| } |
| |
| // Don't allow unsigned apps on either end |
| if (ArrayUtils.isEmpty(storedSigHashes)) { |
| return false; |
| } |
| |
| SigningInfo signingInfo = target.signingInfo; |
| if (signingInfo == null) { |
| Slog.w(TAG, "signingInfo is empty, app was either unsigned or the flag" + |
| " PackageManager#GET_SIGNING_CERTIFICATES was not specified"); |
| return false; |
| } |
| |
| if (DEBUG) { |
| Slog.v(TAG, "signaturesMatch(): stored=" + storedSigHashes |
| + " device=" + signingInfo.getApkContentsSigners()); |
| } |
| |
| final int nStored = storedSigHashes.size(); |
| if (nStored == 1) { |
| // if the app is only signed with one sig, it's possible it has rotated its key |
| // the checks with signing history are delegated to PackageManager |
| // TODO(b/73988180): address the case that app has declared restoreAnyVersion and is |
| // restoring from higher version to lower after having rotated the key (i.e. higher |
| // version has different sig than lower version that we want to restore to) |
| return pmi.isDataRestoreSafe(storedSigHashes.get(0), target.packageName); |
| } else { |
| // the app couldn't have rotated keys, since it was signed with multiple sigs - do |
| // a check to see if we find a match for all stored sigs |
| // since app hasn't rotated key, we only need to check with current signers |
| ArrayList<byte[]> deviceHashes = |
| hashSignatureArray(signingInfo.getApkContentsSigners()); |
| int nDevice = deviceHashes.size(); |
| // ensure that each stored sig matches an on-device sig |
| for (int i = 0; i < nStored; i++) { |
| boolean match = false; |
| for (int j = 0; j < nDevice; j++) { |
| if (Arrays.equals(storedSigHashes.get(i), deviceHashes.get(j))) { |
| match = true; |
| break; |
| } |
| } |
| if (!match) { |
| return false; |
| } |
| } |
| // we have found a match for all stored sigs |
| return true; |
| } |
| } |
| |
| public static byte[] hashSignature(byte[] signature) { |
| try { |
| MessageDigest digest = MessageDigest.getInstance("SHA-256"); |
| digest.update(signature); |
| return digest.digest(); |
| } catch (NoSuchAlgorithmException e) { |
| Slog.w(TAG, "No SHA-256 algorithm found!"); |
| } |
| return null; |
| } |
| |
| public static byte[] hashSignature(Signature signature) { |
| return hashSignature(signature.toByteArray()); |
| } |
| |
| public static ArrayList<byte[]> hashSignatureArray(Signature[] sigs) { |
| if (sigs == null) { |
| return null; |
| } |
| |
| ArrayList<byte[]> hashes = new ArrayList<>(sigs.length); |
| for (Signature s : sigs) { |
| hashes.add(hashSignature(s)); |
| } |
| return hashes; |
| } |
| |
| public static ArrayList<byte[]> hashSignatureArray(List<byte[]> sigs) { |
| if (sigs == null) { |
| return null; |
| } |
| |
| ArrayList<byte[]> hashes = new ArrayList<>(sigs.size()); |
| for (byte[] s : sigs) { |
| hashes.add(hashSignature(s)); |
| } |
| return hashes; |
| } |
| } |