Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2016 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.server.backup; |
| 18 | |
| 19 | import android.content.pm.ApplicationInfo; |
| 20 | import android.content.pm.PackageInfo; |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 21 | import android.content.pm.PackageManagerInternal; |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 22 | import android.content.pm.Signature; |
Dan Cashman | 5c9f527e | 2018-04-03 16:42:23 -0700 | [diff] [blame] | 23 | import android.content.pm.SigningInfo; |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 24 | import android.util.Slog; |
| 25 | |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 26 | import com.android.internal.util.ArrayUtils; |
| 27 | |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 28 | import java.security.MessageDigest; |
| 29 | import java.security.NoSuchAlgorithmException; |
| 30 | import java.util.ArrayList; |
| 31 | import java.util.Arrays; |
| 32 | import java.util.List; |
| 33 | |
| 34 | public class BackupUtils { |
| 35 | private static final String TAG = "BackupUtils"; |
| 36 | |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 37 | private static final boolean DEBUG = false; |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 38 | |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 39 | public static boolean signaturesMatch(ArrayList<byte[]> storedSigHashes, PackageInfo target, |
| 40 | PackageManagerInternal pmi) { |
| 41 | if (target == null || target.packageName == null) { |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 42 | return false; |
| 43 | } |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 44 | // If the target resides on the system partition, we allow it to restore |
| 45 | // data from the like-named package in a restore set even if the signatures |
| 46 | // do not match. (Unlike general applications, those flashed to the system |
| 47 | // partition will be signed with the device's platform certificate, so on |
| 48 | // different phones the same system app will have different signatures.) |
| 49 | if ((target.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0) { |
| 50 | if (DEBUG) Slog.v(TAG, "System app " + target.packageName + " - skipping sig check"); |
| 51 | return true; |
| 52 | } |
| 53 | |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 54 | // Don't allow unsigned apps on either end |
| 55 | if (ArrayUtils.isEmpty(storedSigHashes)) { |
Amith Yamasani | 14c716c | 2018-03-05 20:39:04 +0000 | [diff] [blame] | 56 | return false; |
| 57 | } |
| 58 | |
Dan Cashman | 5c9f527e | 2018-04-03 16:42:23 -0700 | [diff] [blame] | 59 | SigningInfo signingInfo = target.signingInfo; |
| 60 | if (signingInfo == null) { |
| 61 | Slog.w(TAG, "signingInfo is empty, app was either unsigned or the flag" + |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 62 | " PackageManager#GET_SIGNING_CERTIFICATES was not specified"); |
| 63 | return false; |
Amith Yamasani | 14c716c | 2018-03-05 20:39:04 +0000 | [diff] [blame] | 64 | } |
| 65 | |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 66 | if (DEBUG) { |
| 67 | Slog.v(TAG, "signaturesMatch(): stored=" + storedSigHashes |
Dan Cashman | 5c9f527e | 2018-04-03 16:42:23 -0700 | [diff] [blame] | 68 | + " device=" + signingInfo.getApkContentsSigners()); |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 69 | } |
| 70 | |
| 71 | final int nStored = storedSigHashes.size(); |
| 72 | if (nStored == 1) { |
| 73 | // if the app is only signed with one sig, it's possible it has rotated its key |
| 74 | // the checks with signing history are delegated to PackageManager |
| 75 | // TODO(b/73988180): address the case that app has declared restoreAnyVersion and is |
| 76 | // restoring from higher version to lower after having rotated the key (i.e. higher |
| 77 | // version has different sig than lower version that we want to restore to) |
| 78 | return pmi.isDataRestoreSafe(storedSigHashes.get(0), target.packageName); |
| 79 | } else { |
| 80 | // the app couldn't have rotated keys, since it was signed with multiple sigs - do |
| 81 | // a check to see if we find a match for all stored sigs |
Dan Cashman | 5c9f527e | 2018-04-03 16:42:23 -0700 | [diff] [blame] | 82 | // since app hasn't rotated key, we only need to check with current signers |
| 83 | ArrayList<byte[]> deviceHashes = |
| 84 | hashSignatureArray(signingInfo.getApkContentsSigners()); |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 85 | int nDevice = deviceHashes.size(); |
| 86 | // ensure that each stored sig matches an on-device sig |
| 87 | for (int i = 0; i < nStored; i++) { |
| 88 | boolean match = false; |
| 89 | for (int j = 0; j < nDevice; j++) { |
| 90 | if (Arrays.equals(storedSigHashes.get(i), deviceHashes.get(j))) { |
| 91 | match = true; |
| 92 | break; |
| 93 | } |
| 94 | } |
| 95 | if (!match) { |
| 96 | return false; |
Amith Yamasani | 14c716c | 2018-03-05 20:39:04 +0000 | [diff] [blame] | 97 | } |
| 98 | } |
Michal Karpinski | 528c3e5 | 2018-02-07 17:47:10 +0000 | [diff] [blame] | 99 | // we have found a match for all stored sigs |
| 100 | return true; |
Amith Yamasani | 14c716c | 2018-03-05 20:39:04 +0000 | [diff] [blame] | 101 | } |
Makoto Onuki | 590096a | 2016-03-25 17:15:30 -0700 | [diff] [blame] | 102 | } |
| 103 | |
| 104 | public static byte[] hashSignature(byte[] signature) { |
| 105 | try { |
| 106 | MessageDigest digest = MessageDigest.getInstance("SHA-256"); |
| 107 | digest.update(signature); |
| 108 | return digest.digest(); |
| 109 | } catch (NoSuchAlgorithmException e) { |
| 110 | Slog.w(TAG, "No SHA-256 algorithm found!"); |
| 111 | } |
| 112 | return null; |
| 113 | } |
| 114 | |
| 115 | public static byte[] hashSignature(Signature signature) { |
| 116 | return hashSignature(signature.toByteArray()); |
| 117 | } |
| 118 | |
| 119 | public static ArrayList<byte[]> hashSignatureArray(Signature[] sigs) { |
| 120 | if (sigs == null) { |
| 121 | return null; |
| 122 | } |
| 123 | |
| 124 | ArrayList<byte[]> hashes = new ArrayList<>(sigs.length); |
| 125 | for (Signature s : sigs) { |
| 126 | hashes.add(hashSignature(s)); |
| 127 | } |
| 128 | return hashes; |
| 129 | } |
| 130 | |
| 131 | public static ArrayList<byte[]> hashSignatureArray(List<byte[]> sigs) { |
| 132 | if (sigs == null) { |
| 133 | return null; |
| 134 | } |
| 135 | |
| 136 | ArrayList<byte[]> hashes = new ArrayList<>(sigs.size()); |
| 137 | for (byte[] s : sigs) { |
| 138 | hashes.add(hashSignature(s)); |
| 139 | } |
| 140 | return hashes; |
| 141 | } |
| 142 | } |