1 /* 2 * Copyright (C) 2021 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.am; 18 19 import static com.android.server.am.ActivityManagerDebugConfig.TAG_AM; 20 21 import android.annotation.Nullable; 22 import android.os.SystemClock; 23 import android.os.UserHandle; 24 import android.util.Pair; 25 import android.util.Slog; 26 import android.util.SparseArray; 27 28 import java.util.function.BiConsumer; 29 30 /** 31 * List of keys that have expiration time. 32 * If the expiration time is less than current elapsedRealtime, the key has expired. 33 * Otherwise it is valid (or allowed). 34 * 35 * <p>This is used for both FGS-BG-start restriction, and FGS-while-in-use permissions check.</p> 36 * 37 * <p>Note: the underlying data structure is an {@link SparseArray}, for performance reason, 38 * it is only suitable to hold up to hundreds of entries.</p> 39 * @param <E> type of the additional optional info. 40 */ 41 public class FgsTempAllowList<E> { 42 private static final int DEFAULT_MAX_SIZE = 100; 43 44 /** 45 * The value is Pair type, Pair.first is the expirationTime(an elapsedRealtime), 46 * Pair.second is the optional information entry about this key. 47 */ 48 private final SparseArray<Pair<Long, E>> mTempAllowList = new SparseArray<>(); 49 private int mMaxSize = DEFAULT_MAX_SIZE; 50 private final Object mLock = new Object(); 51 FgsTempAllowList()52 public FgsTempAllowList() { 53 } 54 55 /** 56 * 57 * @param maxSize The max size of the list. It is only a suggestion. If the list size is 58 * larger than max size, a warning message is printed in logcat, new entry can 59 * still be added to the list. The default max size is {@link #DEFAULT_MAX_SIZE}. 60 */ FgsTempAllowList(int maxSize)61 public FgsTempAllowList(int maxSize) { 62 if (maxSize <= 0) { 63 Slog.e(TAG_AM, "Invalid FgsTempAllowList maxSize:" + maxSize 64 + ", force default maxSize:" + DEFAULT_MAX_SIZE); 65 mMaxSize = DEFAULT_MAX_SIZE; 66 } else { 67 mMaxSize = maxSize; 68 } 69 } 70 71 /** 72 * Add a key and its duration with optional info into the temp allowlist. 73 * @param durationMs temp-allowlisted duration in milliseconds. 74 * @param entry additional optional information of this key, could be null. 75 */ add(int uid, long durationMs, @Nullable E entry)76 public void add(int uid, long durationMs, @Nullable E entry) { 77 synchronized (mLock) { 78 if (durationMs <= 0) { 79 Slog.e(TAG_AM, "FgsTempAllowList bad duration:" + durationMs + " key: " 80 + uid); 81 return; 82 } 83 // The temp allowlist should be a short list with only a few entries in it. 84 // for a very large list, HashMap structure should be used. 85 final long now = SystemClock.elapsedRealtime(); 86 final int size = mTempAllowList.size(); 87 if (size > mMaxSize) { 88 Slog.w(TAG_AM, "FgsTempAllowList length:" + size + " exceeds maxSize" 89 + mMaxSize); 90 for (int index = size - 1; index >= 0; index--) { 91 if (mTempAllowList.valueAt(index).first < now) { 92 mTempAllowList.removeAt(index); 93 } 94 } 95 } 96 final Pair<Long, E> existing = mTempAllowList.get(uid); 97 final long expirationTime = now + durationMs; 98 if (existing == null || existing.first < expirationTime) { 99 mTempAllowList.put(uid, new Pair(expirationTime, entry)); 100 } 101 } 102 } 103 104 /** 105 * If the key has not expired (AKA allowed), return its non-null value. 106 * If the key has expired, return null. 107 * @return 108 */ 109 @Nullable get(int uid)110 public Pair<Long, E> get(int uid) { 111 synchronized (mLock) { 112 final int index = mTempAllowList.indexOfKey(uid); 113 if (index < 0) { 114 return null; 115 } else if (mTempAllowList.valueAt(index).first < SystemClock.elapsedRealtime()) { 116 mTempAllowList.removeAt(index); 117 return null; 118 } else { 119 return mTempAllowList.valueAt(index); 120 } 121 } 122 } 123 124 /** 125 * If the key has not expired (AKA allowed), return true. 126 * If the key has expired, return false. 127 */ isAllowed(int uid)128 public boolean isAllowed(int uid) { 129 Pair<Long, E> entry = get(uid); 130 return entry != null; 131 } 132 133 /** 134 * Remove a given UID. 135 */ removeUid(int uid)136 public void removeUid(int uid) { 137 synchronized (mLock) { 138 mTempAllowList.remove(uid); 139 } 140 } 141 142 /** 143 * Remove by appId. 144 */ removeAppId(int appId)145 public void removeAppId(int appId) { 146 synchronized (mLock) { 147 // Find all UIDs matching the appId. 148 for (int i = mTempAllowList.size() - 1; i >= 0; i--) { 149 final int uid = mTempAllowList.keyAt(i); 150 if (UserHandle.getAppId(uid) == appId) { 151 mTempAllowList.removeAt(i); 152 } 153 } 154 } 155 } 156 157 /** 158 * Iterate over the entries. 159 */ forEach(BiConsumer<Integer, Pair<Long, E>> callback)160 public void forEach(BiConsumer<Integer, Pair<Long, E>> callback) { 161 synchronized (mLock) { 162 for (int i = 0; i < mTempAllowList.size(); i++) { 163 final int uid = mTempAllowList.keyAt(i); 164 final Pair<Long, E> entry = mTempAllowList.valueAt(i); 165 if (entry != null) { 166 callback.accept(uid, entry); 167 } 168 } 169 } 170 } 171 } 172