services/core/java/com/android/server/am/SettingsToPropertiesMapper.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.server.am;

 import android.content.ContentResolver;
 import android.database.ContentObserver;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.os.Build;
 import android.os.SystemProperties;
 import android.provider.DeviceConfig;
 import android.provider.Settings;
 import android.text.TextUtils;
 import android.util.Slog;

 import com.android.internal.annotations.VisibleForTesting;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.IOException;
 import java.util.HashSet;

 /**
  * Maps system settings to system properties.
  * <p>The properties are dynamically updated when settings change.
  */
 class SettingsToPropertiesMapper {

     private static final String TAG = "SettingsToPropertiesMapper";

     private static final String SYSTEM_PROPERTY_PREFIX = "persist.device_config.";

     private static final String RESET_PERFORMED_PROPERTY = "device_config.reset_performed";

     private static final String RESET_RECORD_FILE_PATH =
             "/data/server_configurable_flags/reset_flags";

     private static final String SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX = "^[\\w\\.\\-@:]*$";

     private static final String SYSTEM_PROPERTY_INVALID_SUBSTRING = "..";

     private static final int SYSTEM_PROPERTY_MAX_LENGTH = 92;

     // experiment flags added to Global.Settings(before new "Config" provider table is available)
     // will be added under this category.
     private static final String GLOBAL_SETTINGS_CATEGORY = "global_settings";

     // Add the global setting you want to push to native level as experiment flag into this list.
     //
     // NOTE: please grant write permission system property prefix
     // with format persist.device_config.global_settings.[flag_name] in system_server.te and grant
     // read permission in the corresponding .te file your feature belongs to.
     @VisibleForTesting
     static final String[] sGlobalSettings = new String[] {
             Settings.Global.NATIVE_FLAGS_HEALTH_CHECK_ENABLED,
     };

     // All the flags under the listed DeviceConfig scopes will be synced to native level.
     //
     // NOTE: please grant write permission system property prefix
     // with format persist.device_config.[device_config_scope]. in system_server.te and grant read
     // permission in the corresponding .te file your feature belongs to.
     @VisibleForTesting
     static final String[] sDeviceConfigScopes = new String[] {
         DeviceConfig.ActivityManagerNativeBoot.NAMESPACE,
         DeviceConfig.NAMESPACE_INPUT_NATIVE_BOOT,
         DeviceConfig.NAMESPACE_NETD_NATIVE,
         DeviceConfig.RuntimeNativeBoot.NAMESPACE,
         DeviceConfig.RuntimeNative.NAMESPACE,
     };

     private final String[] mGlobalSettings;

     private final String[] mDeviceConfigScopes;

     private final ContentResolver mContentResolver;

     @VisibleForTesting
     protected SettingsToPropertiesMapper(ContentResolver contentResolver,
             String[] globalSettings,
             String[] deviceConfigScopes) {
         mContentResolver = contentResolver;
         mGlobalSettings = globalSettings;
         mDeviceConfigScopes = deviceConfigScopes;
     }

     @VisibleForTesting
     void updatePropertiesFromSettings() {
         for (String globalSetting : mGlobalSettings) {
             Uri settingUri = Settings.Global.getUriFor(globalSetting);
             String propName = makePropertyName(GLOBAL_SETTINGS_CATEGORY, globalSetting);
             if (settingUri == null) {
                 log("setting uri is null for globalSetting " + globalSetting);
                 continue;
             }
             if (propName == null) {
                 log("invalid prop name for globalSetting " + globalSetting);
                 continue;
             }

             ContentObserver co = new ContentObserver(null) {
                 @Override
                 public void onChange(boolean selfChange) {
                     updatePropertyFromSetting(globalSetting, propName);
                 }
             };

             // only updating on starting up when no native flags reset is performed during current
             // booting.
             if (!isNativeFlagsResetPerformed()) {
                 updatePropertyFromSetting(globalSetting, propName);
             }
             mContentResolver.registerContentObserver(settingUri, false, co);
         }

         for (String deviceConfigScope : mDeviceConfigScopes) {
             DeviceConfig.addOnPropertyChangedListener(
                     deviceConfigScope,
                     AsyncTask.THREAD_POOL_EXECUTOR,
                     (String scope, String name, String value) -> {
                         String propertyName = makePropertyName(scope, name);
                         if (propertyName == null) {
                             log("unable to construct system property for " + scope + "/" + name);
                             return;
                         }
                         setProperty(propertyName, value);
                     });
         }
     }

     public static SettingsToPropertiesMapper start(ContentResolver contentResolver) {
         SettingsToPropertiesMapper mapper =  new SettingsToPropertiesMapper(
                 contentResolver, sGlobalSettings, sDeviceConfigScopes);
         mapper.updatePropertiesFromSettings();
         return mapper;
     }

     /**
      * If native level flags reset has been performed as an attempt to recover from a crash loop
      * during current device booting.
      * @return
      */
     public boolean isNativeFlagsResetPerformed() {
         String value = systemPropertiesGet(RESET_PERFORMED_PROPERTY);
         return "true".equals(value);
     }

     /**
      * return an array of native flag categories under which flags got reset during current device
      * booting.
      * @return
      */
     public String[] getResetNativeCategories() {
         if (!isNativeFlagsResetPerformed()) {
             return new String[0];
         }

         String content = getResetFlagsFileContent();
         if (TextUtils.isEmpty(content)) {
             return new String[0];
         }

         String[] property_names = content.split(";");
         HashSet<String> categories = new HashSet<>();
         for (String property_name : property_names) {
             String[] segments = property_name.split("\\.");
             if (segments.length < 3) {
                 log("failed to extract category name from property " + property_name);
                 continue;
             }
             categories.add(segments[2]);
         }
         return categories.toArray(new String[0]);
     }

     /**
      * system property name constructing rule: "persist.device_config.[category_name].[flag_name]".
      * If the name contains invalid characters or substrings for system property name,
      * will return null.
      * @param categoryName
      * @param flagName
      * @return
      */
     @VisibleForTesting
     static String makePropertyName(String categoryName, String flagName) {
         String propertyName = SYSTEM_PROPERTY_PREFIX + categoryName + "." + flagName;

         if (!propertyName.matches(SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX)
                 || propertyName.contains(SYSTEM_PROPERTY_INVALID_SUBSTRING)) {
             return null;
         }

         return propertyName;
     }

     private void setProperty(String key, String value) {
         // Check if need to clear the property
         if (value == null) {
             // It's impossible to remove system property, therefore we check previous value to
             // avoid setting an empty string if the property wasn't set.
             if (TextUtils.isEmpty(systemPropertiesGet(key))) {
                 return;
             }
             value = "";
         } else if (value.length() > SYSTEM_PROPERTY_MAX_LENGTH) {
             log(value + " exceeds system property max length.");
             return;
         }

         try {
             systemPropertiesSet(key, value);
         } catch (Exception e) {
             // Failure to set a property can be caused by SELinux denial. This usually indicates
             // that the property wasn't whitelisted in sepolicy.
             // No need to report it on all user devices, only on debug builds.
             log("Unable to set property " + key + " value '" + value + "'", e);
         }
     }

     private static void log(String msg, Exception e) {
         if (Build.IS_DEBUGGABLE) {
             Slog.wtf(TAG, msg, e);
         } else {
             Slog.e(TAG, msg, e);
         }
     }

     private static void log(String msg) {
         if (Build.IS_DEBUGGABLE) {
             Slog.wtf(TAG, msg);
         } else {
             Slog.e(TAG, msg);
         }
     }

     @VisibleForTesting
     protected String systemPropertiesGet(String key) {
         return SystemProperties.get(key);
     }

     @VisibleForTesting
     protected void systemPropertiesSet(String key, String value) {
         SystemProperties.set(key, value);
     }

     @VisibleForTesting
     protected String getResetFlagsFileContent() {
         String content = null;
         try {
             File reset_flag_file = new File(RESET_RECORD_FILE_PATH);
             BufferedReader br = new BufferedReader(new FileReader(reset_flag_file));
             content = br.readLine();

             br.close();
         } catch (IOException ioe) {
             log("failed to read file " + RESET_RECORD_FILE_PATH, ioe);
         }
         return content;
     }

     @VisibleForTesting
     void updatePropertyFromSetting(String settingName, String propName) {
         String settingValue = Settings.Global.getString(mContentResolver, settingName);
         setProperty(propName, settingValue);
     }
 }
	/*
	* Copyright (C) 2018 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.server.am;

	import android.content.ContentResolver;
	import android.database.ContentObserver;
	import android.net.Uri;
	import android.os.AsyncTask;
	import android.os.Build;
	import android.os.SystemProperties;
	import android.provider.DeviceConfig;
	import android.provider.Settings;
	import android.text.TextUtils;
	import android.util.Slog;

	import com.android.internal.annotations.VisibleForTesting;

	import java.io.BufferedReader;
	import java.io.File;
	import java.io.FileReader;
	import java.io.IOException;
	import java.util.HashSet;

	/**
	* Maps system settings to system properties.
	* <p>The properties are dynamically updated when settings change.
	*/
	class SettingsToPropertiesMapper {

	private static final String TAG = "SettingsToPropertiesMapper";

	private static final String SYSTEM_PROPERTY_PREFIX = "persist.device_config.";

	private static final String RESET_PERFORMED_PROPERTY = "device_config.reset_performed";

	private static final String RESET_RECORD_FILE_PATH =
	"/data/server_configurable_flags/reset_flags";

	private static final String SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX = "^[\\w\\.\\-@:]*$";

	private static final String SYSTEM_PROPERTY_INVALID_SUBSTRING = "..";

	private static final int SYSTEM_PROPERTY_MAX_LENGTH = 92;

	// experiment flags added to Global.Settings(before new "Config" provider table is available)
	// will be added under this category.
	private static final String GLOBAL_SETTINGS_CATEGORY = "global_settings";

	// Add the global setting you want to push to native level as experiment flag into this list.
	//
	// NOTE: please grant write permission system property prefix
	// with format persist.device_config.global_settings.[flag_name] in system_server.te and grant
	// read permission in the corresponding .te file your feature belongs to.
	@VisibleForTesting
	static final String[] sGlobalSettings = new String[] {
	Settings.Global.NATIVE_FLAGS_HEALTH_CHECK_ENABLED,
	};

	// All the flags under the listed DeviceConfig scopes will be synced to native level.
	//
	// NOTE: please grant write permission system property prefix
	// with format persist.device_config.[device_config_scope]. in system_server.te and grant read
	// permission in the corresponding .te file your feature belongs to.
	@VisibleForTesting
	static final String[] sDeviceConfigScopes = new String[] {
	DeviceConfig.ActivityManagerNativeBoot.NAMESPACE,
	DeviceConfig.NAMESPACE_INPUT_NATIVE_BOOT,
	DeviceConfig.NAMESPACE_NETD_NATIVE,
	DeviceConfig.RuntimeNativeBoot.NAMESPACE,
	DeviceConfig.RuntimeNative.NAMESPACE,
	};

	private final String[] mGlobalSettings;

	private final String[] mDeviceConfigScopes;

	private final ContentResolver mContentResolver;

	@VisibleForTesting
	protected SettingsToPropertiesMapper(ContentResolver contentResolver,
	String[] globalSettings,
	String[] deviceConfigScopes) {
	mContentResolver = contentResolver;
	mGlobalSettings = globalSettings;
	mDeviceConfigScopes = deviceConfigScopes;
	}

	@VisibleForTesting
	void updatePropertiesFromSettings() {
	for (String globalSetting : mGlobalSettings) {
	Uri settingUri = Settings.Global.getUriFor(globalSetting);
	String propName = makePropertyName(GLOBAL_SETTINGS_CATEGORY, globalSetting);
	if (settingUri == null) {
	log("setting uri is null for globalSetting " + globalSetting);
	continue;
	}
	if (propName == null) {
	log("invalid prop name for globalSetting " + globalSetting);
	continue;
	}

	ContentObserver co = new ContentObserver(null) {
	@Override
	public void onChange(boolean selfChange) {
	updatePropertyFromSetting(globalSetting, propName);
	}
	};

	// only updating on starting up when no native flags reset is performed during current
	// booting.
	if (!isNativeFlagsResetPerformed()) {
	updatePropertyFromSetting(globalSetting, propName);
	}
	mContentResolver.registerContentObserver(settingUri, false, co);
	}

	for (String deviceConfigScope : mDeviceConfigScopes) {
	DeviceConfig.addOnPropertyChangedListener(
	deviceConfigScope,
	AsyncTask.THREAD_POOL_EXECUTOR,
	(String scope, String name, String value) -> {
	String propertyName = makePropertyName(scope, name);
	if (propertyName == null) {
	log("unable to construct system property for " + scope + "/" + name);
	return;
	}
	setProperty(propertyName, value);
	});
	}
	}

	public static SettingsToPropertiesMapper start(ContentResolver contentResolver) {
	SettingsToPropertiesMapper mapper = new SettingsToPropertiesMapper(
	contentResolver, sGlobalSettings, sDeviceConfigScopes);
	mapper.updatePropertiesFromSettings();
	return mapper;
	}

	/**
	* If native level flags reset has been performed as an attempt to recover from a crash loop
	* during current device booting.
	* @return
	*/
	public boolean isNativeFlagsResetPerformed() {
	String value = systemPropertiesGet(RESET_PERFORMED_PROPERTY);
	return "true".equals(value);
	}

	/**
	* return an array of native flag categories under which flags got reset during current device
	* booting.
	* @return
	*/
	public String[] getResetNativeCategories() {
	if (!isNativeFlagsResetPerformed()) {
	return new String[0];
	}

	String content = getResetFlagsFileContent();
	if (TextUtils.isEmpty(content)) {
	return new String[0];
	}

	String[] property_names = content.split(";");
	HashSet<String> categories = new HashSet<>();
	for (String property_name : property_names) {
	String[] segments = property_name.split("\\.");
	if (segments.length < 3) {
	log("failed to extract category name from property " + property_name);
	continue;
	}
	categories.add(segments[2]);
	}
	return categories.toArray(new String[0]);
	}

	/**
	* system property name constructing rule: "persist.device_config.[category_name].[flag_name]".
	* If the name contains invalid characters or substrings for system property name,
	* will return null.
	* @param categoryName
	* @param flagName
	* @return
	*/
	@VisibleForTesting
	static String makePropertyName(String categoryName, String flagName) {
	String propertyName = SYSTEM_PROPERTY_PREFIX + categoryName + "." + flagName;

	if (!propertyName.matches(SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX)
	\|\| propertyName.contains(SYSTEM_PROPERTY_INVALID_SUBSTRING)) {
	return null;
	}

	return propertyName;
	}

	private void setProperty(String key, String value) {
	// Check if need to clear the property
	if (value == null) {
	// It's impossible to remove system property, therefore we check previous value to
	// avoid setting an empty string if the property wasn't set.
	if (TextUtils.isEmpty(systemPropertiesGet(key))) {
	return;
	}
	value = "";
	} else if (value.length() > SYSTEM_PROPERTY_MAX_LENGTH) {
	log(value + " exceeds system property max length.");
	return;
	}

	try {
	systemPropertiesSet(key, value);
	} catch (Exception e) {
	// Failure to set a property can be caused by SELinux denial. This usually indicates
	// that the property wasn't whitelisted in sepolicy.
	// No need to report it on all user devices, only on debug builds.
	log("Unable to set property " + key + " value '" + value + "'", e);
	}
	}

	private static void log(String msg, Exception e) {
	if (Build.IS_DEBUGGABLE) {
	Slog.wtf(TAG, msg, e);
	} else {
	Slog.e(TAG, msg, e);
	}
	}

	private static void log(String msg) {
	if (Build.IS_DEBUGGABLE) {
	Slog.wtf(TAG, msg);
	} else {
	Slog.e(TAG, msg);
	}
	}

	@VisibleForTesting
	protected String systemPropertiesGet(String key) {
	return SystemProperties.get(key);
	}

	@VisibleForTesting
	protected void systemPropertiesSet(String key, String value) {
	SystemProperties.set(key, value);
	}

	@VisibleForTesting
	protected String getResetFlagsFileContent() {
	String content = null;
	try {
	File reset_flag_file = new File(RESET_RECORD_FILE_PATH);
	BufferedReader br = new BufferedReader(new FileReader(reset_flag_file));
	content = br.readLine();

	br.close();
	} catch (IOException ioe) {
	log("failed to read file " + RESET_RECORD_FILE_PATH, ioe);
	}
	return content;
	}

	@VisibleForTesting
	void updatePropertyFromSetting(String settingName, String propName) {
	String settingValue = Settings.Global.getString(mContentResolver, settingName);
	setProperty(propName, settingValue);
	}
	}