1 /*
2  * Copyright (C) 2018 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 android.annotation.NonNull;
20 import android.content.ContentResolver;
21 import android.database.ContentObserver;
22 import android.net.Uri;
23 import android.os.AsyncTask;
24 import android.os.Build;
25 import android.os.SystemProperties;
26 import android.provider.DeviceConfig;
27 import android.provider.Settings;
28 import android.text.TextUtils;
29 import android.util.Slog;
30 
31 import com.android.internal.annotations.VisibleForTesting;
32 
33 import java.io.BufferedReader;
34 import java.io.File;
35 import java.io.FileReader;
36 import java.io.IOException;
37 import java.util.HashSet;
38 
39 /**
40  * Maps system settings to system properties.
41  * <p>The properties are dynamically updated when settings change.
42  * @hide
43  */
44 public class SettingsToPropertiesMapper {
45 
46     private static final String TAG = "SettingsToPropertiesMapper";
47 
48     private static final String SYSTEM_PROPERTY_PREFIX = "persist.device_config.";
49 
50     private static final String RESET_PERFORMED_PROPERTY = "device_config.reset_performed";
51 
52     private static final String RESET_RECORD_FILE_PATH =
53             "/data/server_configurable_flags/reset_flags";
54 
55     private static final String SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX = "^[\\w\\.\\-@:]*$";
56 
57     private static final String SYSTEM_PROPERTY_INVALID_SUBSTRING = "..";
58 
59     private static final int SYSTEM_PROPERTY_MAX_LENGTH = 92;
60 
61     // experiment flags added to Global.Settings(before new "Config" provider table is available)
62     // will be added under this category.
63     private static final String GLOBAL_SETTINGS_CATEGORY = "global_settings";
64 
65     // Add the global setting you want to push to native level as experiment flag into this list.
66     //
67     // NOTE: please grant write permission system property prefix
68     // with format persist.device_config.global_settings.[flag_name] in system_server.te and grant
69     // read permission in the corresponding .te file your feature belongs to.
70     @VisibleForTesting
71     static final String[] sGlobalSettings = new String[] {
72             Settings.Global.NATIVE_FLAGS_HEALTH_CHECK_ENABLED,
73     };
74 
75     // All the flags under the listed DeviceConfig scopes will be synced to native level.
76     //
77     // NOTE: please grant write permission system property prefix
78     // with format persist.device_config.[device_config_scope]. in system_server.te and grant read
79     // permission in the corresponding .te file your feature belongs to.
80     @VisibleForTesting
81     static final String[] sDeviceConfigScopes = new String[] {
82         DeviceConfig.NAMESPACE_ACTIVITY_MANAGER_NATIVE_BOOT,
83         DeviceConfig.NAMESPACE_CONFIGURATION,
84         DeviceConfig.NAMESPACE_INPUT_NATIVE_BOOT,
85         DeviceConfig.NAMESPACE_INTELLIGENCE_CONTENT_SUGGESTIONS,
86         DeviceConfig.NAMESPACE_MEDIA_NATIVE,
87         DeviceConfig.NAMESPACE_NETD_NATIVE,
88         DeviceConfig.NAMESPACE_RUNTIME_NATIVE,
89         DeviceConfig.NAMESPACE_RUNTIME_NATIVE_BOOT,
90         DeviceConfig.NAMESPACE_STORAGE_NATIVE_BOOT,
91         DeviceConfig.NAMESPACE_WINDOW_MANAGER_NATIVE_BOOT,
92     };
93 
94     private final String[] mGlobalSettings;
95 
96     private final String[] mDeviceConfigScopes;
97 
98     private final ContentResolver mContentResolver;
99 
100     @VisibleForTesting
SettingsToPropertiesMapper(ContentResolver contentResolver, String[] globalSettings, String[] deviceConfigScopes)101     protected SettingsToPropertiesMapper(ContentResolver contentResolver,
102             String[] globalSettings,
103             String[] deviceConfigScopes) {
104         mContentResolver = contentResolver;
105         mGlobalSettings = globalSettings;
106         mDeviceConfigScopes = deviceConfigScopes;
107     }
108 
109     @VisibleForTesting
updatePropertiesFromSettings()110     void updatePropertiesFromSettings() {
111         for (String globalSetting : mGlobalSettings) {
112             Uri settingUri = Settings.Global.getUriFor(globalSetting);
113             String propName = makePropertyName(GLOBAL_SETTINGS_CATEGORY, globalSetting);
114             if (settingUri == null) {
115                 log("setting uri is null for globalSetting " + globalSetting);
116                 continue;
117             }
118             if (propName == null) {
119                 log("invalid prop name for globalSetting " + globalSetting);
120                 continue;
121             }
122 
123             ContentObserver co = new ContentObserver(null) {
124                 @Override
125                 public void onChange(boolean selfChange) {
126                     updatePropertyFromSetting(globalSetting, propName);
127                 }
128             };
129 
130             // only updating on starting up when no native flags reset is performed during current
131             // booting.
132             if (!isNativeFlagsResetPerformed()) {
133                 updatePropertyFromSetting(globalSetting, propName);
134             }
135             mContentResolver.registerContentObserver(settingUri, false, co);
136         }
137 
138         for (String deviceConfigScope : mDeviceConfigScopes) {
139             DeviceConfig.addOnPropertiesChangedListener(
140                     deviceConfigScope,
141                     AsyncTask.THREAD_POOL_EXECUTOR,
142                     (DeviceConfig.Properties properties) -> {
143                         String scope = properties.getNamespace();
144                         for (String key : properties.getKeyset()) {
145                             String propertyName = makePropertyName(scope, key);
146                             if (propertyName == null) {
147                                 log("unable to construct system property for " + scope + "/"
148                                         + key);
149                                 return;
150                             }
151                             setProperty(propertyName, properties.getString(key, null));
152                         }
153                     });
154         }
155     }
156 
start(ContentResolver contentResolver)157     public static SettingsToPropertiesMapper start(ContentResolver contentResolver) {
158         SettingsToPropertiesMapper mapper =  new SettingsToPropertiesMapper(
159                 contentResolver, sGlobalSettings, sDeviceConfigScopes);
160         mapper.updatePropertiesFromSettings();
161         return mapper;
162     }
163 
164     /**
165      * If native level flags reset has been performed as an attempt to recover from a crash loop
166      * during current device booting.
167      * @return
168      */
isNativeFlagsResetPerformed()169     public static boolean isNativeFlagsResetPerformed() {
170         String value = SystemProperties.get(RESET_PERFORMED_PROPERTY);
171         return "true".equals(value);
172     }
173 
174     /**
175      * return an array of native flag categories under which flags got reset during current device
176      * booting.
177      * @return
178      */
getResetNativeCategories()179     public static @NonNull String[] getResetNativeCategories() {
180         if (!isNativeFlagsResetPerformed()) {
181             return new String[0];
182         }
183 
184         String content = getResetFlagsFileContent();
185         if (TextUtils.isEmpty(content)) {
186             return new String[0];
187         }
188 
189         String[] property_names = content.split(";");
190         HashSet<String> categories = new HashSet<>();
191         for (String property_name : property_names) {
192             String[] segments = property_name.split("\\.");
193             if (segments.length < 3) {
194                 log("failed to extract category name from property " + property_name);
195                 continue;
196             }
197             categories.add(segments[2]);
198         }
199         return categories.toArray(new String[0]);
200     }
201 
202     /**
203      * system property name constructing rule: "persist.device_config.[category_name].[flag_name]".
204      * If the name contains invalid characters or substrings for system property name,
205      * will return null.
206      * @param categoryName
207      * @param flagName
208      * @return
209      */
210     @VisibleForTesting
makePropertyName(String categoryName, String flagName)211     static String makePropertyName(String categoryName, String flagName) {
212         String propertyName = SYSTEM_PROPERTY_PREFIX + categoryName + "." + flagName;
213 
214         if (!propertyName.matches(SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX)
215                 || propertyName.contains(SYSTEM_PROPERTY_INVALID_SUBSTRING)) {
216             return null;
217         }
218 
219         return propertyName;
220     }
221 
setProperty(String key, String value)222     private void setProperty(String key, String value) {
223         // Check if need to clear the property
224         if (value == null) {
225             // It's impossible to remove system property, therefore we check previous value to
226             // avoid setting an empty string if the property wasn't set.
227             if (TextUtils.isEmpty(SystemProperties.get(key))) {
228                 return;
229             }
230             value = "";
231         } else if (value.length() > SYSTEM_PROPERTY_MAX_LENGTH) {
232             log(value + " exceeds system property max length.");
233             return;
234         }
235 
236         try {
237             SystemProperties.set(key, value);
238         } catch (Exception e) {
239             // Failure to set a property can be caused by SELinux denial. This usually indicates
240             // that the property wasn't whitelisted in sepolicy.
241             // No need to report it on all user devices, only on debug builds.
242             log("Unable to set property " + key + " value '" + value + "'", e);
243         }
244     }
245 
log(String msg, Exception e)246     private static void log(String msg, Exception e) {
247         if (Build.IS_DEBUGGABLE) {
248             Slog.wtf(TAG, msg, e);
249         } else {
250             Slog.e(TAG, msg, e);
251         }
252     }
253 
log(String msg)254     private static void log(String msg) {
255         if (Build.IS_DEBUGGABLE) {
256             Slog.wtf(TAG, msg);
257         } else {
258             Slog.e(TAG, msg);
259         }
260     }
261 
262     @VisibleForTesting
getResetFlagsFileContent()263     static String getResetFlagsFileContent() {
264         String content = null;
265         try {
266             File reset_flag_file = new File(RESET_RECORD_FILE_PATH);
267             BufferedReader br = new BufferedReader(new FileReader(reset_flag_file));
268             content = br.readLine();
269 
270             br.close();
271         } catch (IOException ioe) {
272             log("failed to read file " + RESET_RECORD_FILE_PATH, ioe);
273         }
274         return content;
275     }
276 
277     @VisibleForTesting
updatePropertyFromSetting(String settingName, String propName)278     void updatePropertyFromSetting(String settingName, String propName) {
279         String settingValue = Settings.Global.getString(mContentResolver, settingName);
280         setProperty(propName, settingValue);
281     }
282 }
283