| /* |
| * 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.Signature; |
| import android.util.Slog; |
| |
| 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; // STOPSHIP if true |
| |
| public static boolean signaturesMatch(ArrayList<byte[]> storedSigHashes, PackageInfo target) { |
| if (target == 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; |
| } |
| |
| // Allow unsigned apps, but not signed on one device and unsigned on the other |
| // !!! TODO: is this the right policy? |
| Signature[] deviceSigs = target.signatures; |
| if (DEBUG) Slog.v(TAG, "signaturesMatch(): stored=" + storedSigHashes |
| + " device=" + deviceSigs); |
| if ((storedSigHashes == null || storedSigHashes.size() == 0) |
| && (deviceSigs == null || deviceSigs.length == 0)) { |
| return true; |
| } |
| if (storedSigHashes == null || deviceSigs == null) { |
| return false; |
| } |
| |
| // !!! TODO: this demands that every stored signature match one |
| // that is present on device, and does not demand the converse. |
| // Is this this right policy? |
| final int nStored = storedSigHashes.size(); |
| final int nDevice = deviceSigs.length; |
| |
| // hash each on-device signature |
| ArrayList<byte[]> deviceHashes = new ArrayList<byte[]>(nDevice); |
| for (int i = 0; i < nDevice; i++) { |
| deviceHashes.add(hashSignature(deviceSigs[i])); |
| } |
| |
| // now ensure that each stored sig (hash) matches an on-device sig (hash) |
| for (int n = 0; n < nStored; n++) { |
| boolean match = false; |
| final byte[] storedHash = storedSigHashes.get(n); |
| for (int i = 0; i < nDevice; i++) { |
| if (Arrays.equals(storedHash, deviceHashes.get(i))) { |
| match = true; |
| break; |
| } |
| } |
| // match is false when no on-device sig matched one of the stored ones |
| if (!match) { |
| return false; |
| } |
| } |
| |
| 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; |
| } |
| } |