/*
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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.server.locksettings;
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import android.os.SystemProperties;
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import android.util.Slog;
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import com.android.internal.annotations.VisibleForTesting;
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import java.io.File;
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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.io.InputStream;
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import java.io.OutputStream;
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import java.nio.file.Paths;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.Map;
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import java.util.Properties;
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import java.util.Set;
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/**
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* A class that maintains a mapping of which password slots are used by alternate OS images when
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* dual-booting a device. Currently, slots can either be owned by the host OS or a live GSI.
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* This mapping is stored in /metadata/password_slots/slot_map using Java Properties.
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*
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* If a /metadata partition does not exist, GSIs are not supported, and PasswordSlotManager will
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* simply not persist the slot mapping.
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*/
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public class PasswordSlotManager {
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private static final String TAG = "PasswordSlotManager";
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private static final String GSI_RUNNING_PROP = "ro.gsid.image_running";
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private static final String SLOT_MAP_DIR = "/metadata/password_slots";
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// This maps each used password slot to the OS image that created it. Password slots are
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// integer keys/indices into secure storage. The OS image is recorded as a string. The factory
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// image is "host" and GSIs are "gsi<N>" where N >= 1.
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private Map<Integer, String> mSlotMap;
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// Cache the active slots until loadSlotMap() is called.
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private Set<Integer> mActiveSlots;
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public PasswordSlotManager() {
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}
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@VisibleForTesting
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protected String getSlotMapDir() {
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return SLOT_MAP_DIR;
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}
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@VisibleForTesting
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protected int getGsiImageNumber() {
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return SystemProperties.getInt(GSI_RUNNING_PROP, 0);
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}
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/**
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* Notify the manager of which slots are definitively in use by the current OS image.
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*
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* @throws RuntimeException
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*/
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public void refreshActiveSlots(Set<Integer> activeSlots) throws RuntimeException {
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if (mSlotMap == null) {
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mActiveSlots = new HashSet<Integer>(activeSlots);
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return;
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}
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// Update which slots are owned by the current image.
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final HashSet<Integer> slotsToDelete = new HashSet<Integer>();
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for (Map.Entry<Integer, String> entry : mSlotMap.entrySet()) {
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// Delete possibly stale entries for the current image.
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if (entry.getValue().equals(getMode())) {
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slotsToDelete.add(entry.getKey());
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}
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}
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for (Integer slot : slotsToDelete) {
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mSlotMap.remove(slot);
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}
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// Add slots for the current image.
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for (Integer slot : activeSlots) {
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mSlotMap.put(slot, getMode());
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}
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saveSlotMap();
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}
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/**
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* Mark the given slot as in use by the current OS image.
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*
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* @throws RuntimeException
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*/
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public void markSlotInUse(int slot) throws RuntimeException {
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ensureSlotMapLoaded();
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if (mSlotMap.containsKey(slot) && !mSlotMap.get(slot).equals(getMode())) {
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throw new RuntimeException("password slot " + slot + " is not available");
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}
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mSlotMap.put(slot, getMode());
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saveSlotMap();
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}
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/**
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* Mark the given slot as no longer in use by the current OS image.
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*
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* @throws RuntimeException
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*/
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public void markSlotDeleted(int slot) throws RuntimeException {
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ensureSlotMapLoaded();
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if (mSlotMap.containsKey(slot) && !mSlotMap.get(slot).equals(getMode())) {
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throw new RuntimeException("password slot " + slot + " cannot be deleted");
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}
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mSlotMap.remove(slot);
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saveSlotMap();
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}
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/**
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* Return the set of slots used across all OS images.
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*
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* @return Integer set of all used slots.
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*/
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public Set<Integer> getUsedSlots() {
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ensureSlotMapLoaded();
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return Collections.unmodifiableSet(mSlotMap.keySet());
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}
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private File getSlotMapFile() {
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return Paths.get(getSlotMapDir(), "slot_map").toFile();
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}
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private String getMode() {
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int gsiIndex = getGsiImageNumber();
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if (gsiIndex > 0) {
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return "gsi" + gsiIndex;
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}
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return "host";
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}
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@VisibleForTesting
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protected Map<Integer, String> loadSlotMap(InputStream stream) throws IOException {
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final HashMap<Integer, String> map = new HashMap<Integer, String>();
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final Properties props = new Properties();
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props.load(stream);
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for (String slotString : props.stringPropertyNames()) {
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final int slot = Integer.parseInt(slotString);
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final String owner = props.getProperty(slotString);
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map.put(slot, owner);
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}
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return map;
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}
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private Map<Integer, String> loadSlotMap() {
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// It's okay if the file doesn't exist.
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final File file = getSlotMapFile();
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if (file.exists()) {
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try (FileInputStream stream = new FileInputStream(file)) {
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return loadSlotMap(stream);
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} catch (Exception e) {
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Slog.e(TAG, "Could not load slot map file", e);
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}
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}
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return new HashMap<Integer, String>();
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}
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private void ensureSlotMapLoaded() {
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if (mSlotMap == null) {
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mSlotMap = loadSlotMap();
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if (mActiveSlots != null) {
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refreshActiveSlots(mActiveSlots);
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mActiveSlots = null;
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}
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}
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}
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@VisibleForTesting
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protected void saveSlotMap(OutputStream stream) throws IOException {
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if (mSlotMap == null) {
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return;
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}
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final Properties props = new Properties();
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for (Map.Entry<Integer, String> entry : mSlotMap.entrySet()) {
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props.setProperty(entry.getKey().toString(), entry.getValue());
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}
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props.store(stream, "");
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}
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private void saveSlotMap() {
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if (mSlotMap == null) {
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return;
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}
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if (!getSlotMapFile().getParentFile().exists()) {
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Slog.w(TAG, "Not saving slot map, " + getSlotMapDir() + " does not exist");
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return;
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}
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try (FileOutputStream fos = new FileOutputStream(getSlotMapFile())) {
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saveSlotMap(fos);
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} catch (IOException e) {
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Slog.e(TAG, "failed to save password slot map", e);
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}
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}
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}
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