6785dd8420
Under a pseudo-app for the Package Manager, we store the app signatures for all participating applications installed on the device. At restore time we will restore this first, then ensure that the current on-device signature chain is compatible with the one in the backup set. If there's a mismatch, this may be a spoof attempt and we will refuse to restore that app's data. The restore side of this is not implemented, but the Package Manager agent is here as well as the backup side theoretically pushing the data now.
268 lines
10 KiB
Java
268 lines
10 KiB
Java
/*
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* Copyright (C) 2009 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.server;
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import android.app.BackupAgent;
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import android.backup.BackupDataInput;
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import android.backup.BackupDataOutput;
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import android.content.pm.ApplicationInfo;
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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.os.ParcelFileDescriptor;
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import android.util.Log;
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import java.io.ByteArrayInputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.DataInputStream;
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import java.io.DataOutputStream;
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import java.io.EOFException;
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import java.io.FileInputStream;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.List;
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// !!!TODO: take this out
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import java.util.zip.CRC32;
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/**
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* We back up the signatures of each package so that during a system restore,
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* we can verify that the app whose data we think we have matches the app
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* actually resident on the device.
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*
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* Since the Package Manager isn't a proper "application" we just provide a
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* direct IBackupAgent implementation and hand-construct it at need.
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*/
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public class PackageManagerBackupAgent extends BackupAgent {
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private static final String TAG = "PMBA";
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private static final boolean DEBUG = true;
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private List<ApplicationInfo> mAllApps;
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private PackageManager mPackageManager;
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private HashMap<String, Signature[]> mRestoredSignatures;
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// We're constructed with the set of applications that are participating
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// in backup. This set changes as apps are installed & removed.
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PackageManagerBackupAgent(PackageManager packageMgr, List<ApplicationInfo> apps) {
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mPackageManager = packageMgr;
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mAllApps = apps;
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mRestoredSignatures = null;
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}
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public Signature[] getRestoredSignatures(String packageName) {
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if (mRestoredSignatures == null) {
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return null;
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}
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return mRestoredSignatures.get(packageName);
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}
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// The backed up data is the signature block for each app, keyed by
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// the package name.
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public void onBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
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ParcelFileDescriptor newState) {
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HashSet<String> existing = parseStateFile(oldState);
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// For each app we have on device, see if we've backed it up yet. If not,
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// write its signature block to the output, keyed on the package name.
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for (ApplicationInfo app : mAllApps) {
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String packName = app.packageName;
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if (!existing.contains(packName)) {
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// We haven't stored this app's signatures yet, so we do that now
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try {
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PackageInfo info = mPackageManager.getPackageInfo(packName,
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PackageManager.GET_SIGNATURES);
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// build a byte array out of the signature list
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byte[] sigs = flattenSignatureArray(info.signatures);
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// !!! TODO: take out this debugging
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if (DEBUG) {
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CRC32 crc = new CRC32();
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crc.update(sigs);
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Log.i(TAG, "+ flat sig array for " + packName + " : "
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+ crc.getValue());
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}
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data.writeEntityHeader(packName, sigs.length);
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data.writeEntityData(sigs, sigs.length);
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} catch (NameNotFoundException e) {
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// Weird; we just found it, and now are told it doesn't exist.
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// Treat it as having been removed from the device.
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existing.add(packName);
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} catch (IOException e) {
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// Real error writing data
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Log.e(TAG, "Unable to write package backup data file!");
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return;
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}
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} else {
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// We've already backed up this app. Remove it from the set so
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// we can tell at the end what has disappeared from the device.
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if (!existing.remove(packName)) {
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Log.d(TAG, "*** failed to remove " + packName + " from package set!");
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}
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}
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}
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// At this point, the only entries in 'existing' are apps that were
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// mentioned in the saved state file, but appear to no longer be present
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// on the device. Write a deletion entity for them.
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for (String app : existing) {
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try {
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data.writeEntityHeader(app, -1);
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} catch (IOException e) {
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Log.e(TAG, "Unable to write package deletions!");
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return;
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}
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}
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// Finally, write the new state blob -- just the list of all apps we handled
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writeStateFile(mAllApps, newState);
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}
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// "Restore" here is a misnomer. What we're really doing is reading back the
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// set of app signatures associated with each backed-up app in this restore
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// image. We'll use those later to determine what we can legitimately restore.
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public void onRestore(BackupDataInput data, ParcelFileDescriptor newState)
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throws IOException {
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List<ApplicationInfo> restoredApps = new ArrayList<ApplicationInfo>();
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HashMap<String, Signature[]> sigMap = new HashMap<String, Signature[]>();
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while (data.readNextHeader()) {
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int dataSize = data.getDataSize();
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byte[] buf = new byte[dataSize];
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data.readEntityData(buf, 0, dataSize);
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Signature[] sigs = unflattenSignatureArray(buf);
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String pkg = data.getKey();
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// !!! TODO: take out this debugging
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if (DEBUG) {
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CRC32 crc = new CRC32();
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crc.update(buf);
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Log.i(TAG, "- unflat sig array for " + pkg + " : "
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+ crc.getValue());
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}
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ApplicationInfo app = new ApplicationInfo();
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app.packageName = pkg;
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restoredApps.add(app);
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sigMap.put(pkg, sigs);
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}
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mRestoredSignatures = sigMap;
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}
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// Util: convert an array of Signatures into a flattened byte buffer. The
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// flattened format contains enough info to reconstruct the signature array.
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private byte[] flattenSignatureArray(Signature[] allSigs) {
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ByteArrayOutputStream outBuf = new ByteArrayOutputStream();
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DataOutputStream out = new DataOutputStream(outBuf);
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// build the set of subsidiary buffers
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try {
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// first the # of signatures in the array
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out.writeInt(allSigs.length);
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// then the signatures themselves, length + flattened buffer
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for (Signature sig : allSigs) {
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byte[] flat = sig.toByteArray();
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out.writeInt(flat.length);
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out.write(flat);
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}
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} catch (IOException e) {
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// very strange; we're writing to memory here. abort.
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return null;
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}
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return outBuf.toByteArray();
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}
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private Signature[] unflattenSignatureArray(byte[] buffer) {
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ByteArrayInputStream inBufStream = new ByteArrayInputStream(buffer);
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DataInputStream in = new DataInputStream(inBufStream);
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Signature[] sigs = null;
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try {
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int num = in.readInt();
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sigs = new Signature[num];
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for (int i = 0; i < num; i++) {
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int len = in.readInt();
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byte[] flatSig = new byte[len];
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in.read(flatSig);
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sigs[i] = new Signature(flatSig);
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}
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} catch (EOFException e) {
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// clean termination
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if (sigs == null) {
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Log.w(TAG, "Empty signature block found");
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}
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} catch (IOException e) {
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Log.d(TAG, "Unable to unflatten sigs");
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return null;
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}
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return sigs;
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}
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// Util: parse out an existing state file into a usable structure
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private HashSet<String> parseStateFile(ParcelFileDescriptor stateFile) {
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HashSet<String> set = new HashSet<String>();
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// The state file is just the list of app names we have stored signatures for
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FileInputStream instream = new FileInputStream(stateFile.getFileDescriptor());
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DataInputStream in = new DataInputStream(instream);
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int bufSize = 256;
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byte[] buf = new byte[bufSize];
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try {
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int nameSize = in.readInt();
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if (bufSize < nameSize) {
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bufSize = nameSize + 32;
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buf = new byte[bufSize];
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}
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in.read(buf, 0, nameSize);
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String pkg = new String(buf, 0, nameSize);
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set.add(pkg);
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} catch (EOFException eof) {
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// safe; we're done
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} catch (IOException e) {
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// whoops, bad state file. abort.
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Log.e(TAG, "Unable to read Package Manager state file");
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return null;
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}
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return set;
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}
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// Util: write a set of names into a new state file
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private void writeStateFile(List<ApplicationInfo> apps, ParcelFileDescriptor stateFile) {
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FileOutputStream outstream = new FileOutputStream(stateFile.getFileDescriptor());
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DataOutputStream out = new DataOutputStream(outstream);
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for (ApplicationInfo app : apps) {
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try {
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byte[] pkgNameBuf = app.packageName.getBytes();
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out.writeInt(pkgNameBuf.length);
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out.write(pkgNameBuf);
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} catch (IOException e) {
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Log.e(TAG, "Unable to write package manager state file!");
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return;
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}
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}
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}
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}
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