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_CONNECTIVITY,
85         DeviceConfig.NAMESPACE_INPUT_NATIVE_BOOT,
86         DeviceConfig.NAMESPACE_INTELLIGENCE_CONTENT_SUGGESTIONS,
87         DeviceConfig.NAMESPACE_LMKD_NATIVE,
88         DeviceConfig.NAMESPACE_MEDIA_NATIVE,
89         DeviceConfig.NAMESPACE_NETD_NATIVE,
90         DeviceConfig.NAMESPACE_PROFCOLLECT_NATIVE_BOOT,
91         DeviceConfig.NAMESPACE_RUNTIME_NATIVE,
92         DeviceConfig.NAMESPACE_RUNTIME_NATIVE_BOOT,
93         DeviceConfig.NAMESPACE_STATSD_NATIVE,
94         DeviceConfig.NAMESPACE_STATSD_NATIVE_BOOT,
95         DeviceConfig.NAMESPACE_STORAGE_NATIVE_BOOT,
96         DeviceConfig.NAMESPACE_WINDOW_MANAGER_NATIVE_BOOT,
97     };
98 
99     private final String[] mGlobalSettings;
100 
101     private final String[] mDeviceConfigScopes;
102 
103     private final ContentResolver mContentResolver;
104 
105     @VisibleForTesting
SettingsToPropertiesMapper(ContentResolver contentResolver, String[] globalSettings, String[] deviceConfigScopes)106     protected SettingsToPropertiesMapper(ContentResolver contentResolver,
107             String[] globalSettings,
108             String[] deviceConfigScopes) {
109         mContentResolver = contentResolver;
110         mGlobalSettings = globalSettings;
111         mDeviceConfigScopes = deviceConfigScopes;
112     }
113 
114     @VisibleForTesting
updatePropertiesFromSettings()115     void updatePropertiesFromSettings() {
116         for (String globalSetting : mGlobalSettings) {
117             Uri settingUri = Settings.Global.getUriFor(globalSetting);
118             String propName = makePropertyName(GLOBAL_SETTINGS_CATEGORY, globalSetting);
119             if (settingUri == null) {
120                 log("setting uri is null for globalSetting " + globalSetting);
121                 continue;
122             }
123             if (propName == null) {
124                 log("invalid prop name for globalSetting " + globalSetting);
125                 continue;
126             }
127 
128             ContentObserver co = new ContentObserver(null) {
129                 @Override
130                 public void onChange(boolean selfChange) {
131                     updatePropertyFromSetting(globalSetting, propName);
132                 }
133             };
134 
135             // only updating on starting up when no native flags reset is performed during current
136             // booting.
137             if (!isNativeFlagsResetPerformed()) {
138                 updatePropertyFromSetting(globalSetting, propName);
139             }
140             mContentResolver.registerContentObserver(settingUri, false, co);
141         }
142 
143         for (String deviceConfigScope : mDeviceConfigScopes) {
144             DeviceConfig.addOnPropertiesChangedListener(
145                     deviceConfigScope,
146                     AsyncTask.THREAD_POOL_EXECUTOR,
147                     (DeviceConfig.Properties properties) -> {
148                         String scope = properties.getNamespace();
149                         for (String key : properties.getKeyset()) {
150                             String propertyName = makePropertyName(scope, key);
151                             if (propertyName == null) {
152                                 log("unable to construct system property for " + scope + "/"
153                                         + key);
154                                 return;
155                             }
156                             setProperty(propertyName, properties.getString(key, null));
157                         }
158                     });
159         }
160     }
161 
start(ContentResolver contentResolver)162     public static SettingsToPropertiesMapper start(ContentResolver contentResolver) {
163         SettingsToPropertiesMapper mapper =  new SettingsToPropertiesMapper(
164                 contentResolver, sGlobalSettings, sDeviceConfigScopes);
165         mapper.updatePropertiesFromSettings();
166         return mapper;
167     }
168 
169     /**
170      * If native level flags reset has been performed as an attempt to recover from a crash loop
171      * during current device booting.
172      * @return
173      */
isNativeFlagsResetPerformed()174     public static boolean isNativeFlagsResetPerformed() {
175         String value = SystemProperties.get(RESET_PERFORMED_PROPERTY);
176         return "true".equals(value);
177     }
178 
179     /**
180      * return an array of native flag categories under which flags got reset during current device
181      * booting.
182      * @return
183      */
getResetNativeCategories()184     public static @NonNull String[] getResetNativeCategories() {
185         if (!isNativeFlagsResetPerformed()) {
186             return new String[0];
187         }
188 
189         String content = getResetFlagsFileContent();
190         if (TextUtils.isEmpty(content)) {
191             return new String[0];
192         }
193 
194         String[] property_names = content.split(";");
195         HashSet<String> categories = new HashSet<>();
196         for (String property_name : property_names) {
197             String[] segments = property_name.split("\\.");
198             if (segments.length < 3) {
199                 log("failed to extract category name from property " + property_name);
200                 continue;
201             }
202             categories.add(segments[2]);
203         }
204         return categories.toArray(new String[0]);
205     }
206 
207     /**
208      * system property name constructing rule: "persist.device_config.[category_name].[flag_name]".
209      * If the name contains invalid characters or substrings for system property name,
210      * will return null.
211      * @param categoryName
212      * @param flagName
213      * @return
214      */
215     @VisibleForTesting
makePropertyName(String categoryName, String flagName)216     static String makePropertyName(String categoryName, String flagName) {
217         String propertyName = SYSTEM_PROPERTY_PREFIX + categoryName + "." + flagName;
218 
219         if (!propertyName.matches(SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX)
220                 || propertyName.contains(SYSTEM_PROPERTY_INVALID_SUBSTRING)) {
221             return null;
222         }
223 
224         return propertyName;
225     }
226 
setProperty(String key, String value)227     private void setProperty(String key, String value) {
228         // Check if need to clear the property
229         if (value == null) {
230             // It's impossible to remove system property, therefore we check previous value to
231             // avoid setting an empty string if the property wasn't set.
232             if (TextUtils.isEmpty(SystemProperties.get(key))) {
233                 return;
234             }
235             value = "";
236         } else if (value.length() > SYSTEM_PROPERTY_MAX_LENGTH) {
237             log(value + " exceeds system property max length.");
238             return;
239         }
240 
241         try {
242             SystemProperties.set(key, value);
243         } catch (Exception e) {
244             // Failure to set a property can be caused by SELinux denial. This usually indicates
245             // that the property wasn't allowlisted in sepolicy.
246             // No need to report it on all user devices, only on debug builds.
247             log("Unable to set property " + key + " value '" + value + "'", e);
248         }
249     }
250 
log(String msg, Exception e)251     private static void log(String msg, Exception e) {
252         if (Build.IS_DEBUGGABLE) {
253             Slog.wtf(TAG, msg, e);
254         } else {
255             Slog.e(TAG, msg, e);
256         }
257     }
258 
log(String msg)259     private static void log(String msg) {
260         if (Build.IS_DEBUGGABLE) {
261             Slog.wtf(TAG, msg);
262         } else {
263             Slog.e(TAG, msg);
264         }
265     }
266 
267     @VisibleForTesting
getResetFlagsFileContent()268     static String getResetFlagsFileContent() {
269         String content = null;
270         try {
271             File reset_flag_file = new File(RESET_RECORD_FILE_PATH);
272             BufferedReader br = new BufferedReader(new FileReader(reset_flag_file));
273             content = br.readLine();
274 
275             br.close();
276         } catch (IOException ioe) {
277             log("failed to read file " + RESET_RECORD_FILE_PATH, ioe);
278         }
279         return content;
280     }
281 
282     @VisibleForTesting
updatePropertyFromSetting(String settingName, String propName)283     void updatePropertyFromSetting(String settingName, String propName) {
284         String settingValue = Settings.Global.getString(mContentResolver, settingName);
285         setProperty(propName, settingValue);
286     }
287 }
288