Implement direct boot awareness

To do direct boot, important files need to be moved to device storage (i.e. not as safe storage). The only thing sensitive is user credentials (server settings in each profile) and the config file passed to libss-*.so. In order to implement direct boot, at least the active profile has to be moved/copied to device storage.

This commit keeps profile information (and temporary data used by ProfileConfigFragment) and Shadowsocks config in credential storage and move everything else to device storage. In order to make direct boot work, active profile is also copied into device storage and Shadowsocks config file is created in device storage during direct boot. Cleanup of those information is also implemented.

Fixes #1457.

NB:

* `android:directBootAware` can't be used on application element. That seems to be used by system apps.
* Works fine with multi-user;
* Old GSM files are not migrated (see App.kt) to device storage.

mobile/src/main/java/com/github/shadowsocks/utils/Constants.kt

@@ -21,7 +21,11 @@
 package com.github.shadowsocks.utils
 
 object Key {
-    const val PROFILE = "profile.db"
+    /**
+     * Public config that doesn't need to be kept secret.
+     */
+    const val DB_PUBLIC = "config.db"
+    const val DB_PROFILE = "profile.db"
 
     const val id = "profileId"
     const val name = "profileName"
@@ -39,6 +43,7 @@ object Key {
     const val route = "route"
 
     const val isAutoConnect = "isAutoConnect"
+    const val directBootAware = "directBootAware"
 
     const val proxyApps = "isProxyApps"
     const val bypass = "isBypassApps"

mobile/src/main/java/com/github/shadowsocks/utils/DeviceContext.kt

@@ -0,0 +1,34 @@
+/*******************************************************************************
+ *                                                                             *
+ *  Copyright (C) 2017 by Max Lv <max.c.lv@gmail.com>                          *
+ *  Copyright (C) 2017 by Mygod Studio <contact-shadowsocks-android@mygod.be>  *
+ *                                                                             *
+ *  This program is free software: you can redistribute it and/or modify       *
+ *  it under the terms of the GNU General Public License as published by       *
+ *  the Free Software Foundation, either version 3 of the License, or          *
+ *  (at your option) any later version.                                        *
+ *                                                                             *
+ *  This program is distributed in the hope that it will be useful,            *
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of             *
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              *
+ *  GNU General Public License for more details.                               *
+ *                                                                             *
+ *  You should have received a copy of the GNU General Public License          *
+ *  along with this program. If not, see <http://www.gnu.org/licenses/>.       *
+ *                                                                             *
+ *******************************************************************************/
+
+package com.github.shadowsocks.utils
+
+import android.annotation.TargetApi
+import android.content.Context
+import android.content.ContextWrapper
+
+@TargetApi(24)
+class DeviceContext(context: Context) : ContextWrapper(context.createDeviceProtectedStorageContext()) {
+    /**
+     * Thou shalt not get the REAL underlying application context which would no longer be operating under device
+     * protected storage.
+     */
+    override fun getApplicationContext(): Context = this
+}

mobile/src/main/java/com/github/shadowsocks/utils/DirectBoot.kt

@@ -0,0 +1,31 @@
+package com.github.shadowsocks.utils
+
+import android.annotation.TargetApi
+import com.github.shadowsocks.App.Companion.app
+import com.github.shadowsocks.bg.BaseService
+import com.github.shadowsocks.database.Profile
+import com.github.shadowsocks.database.ProfileManager
+import com.github.shadowsocks.preference.DataStore
+import java.io.File
+import java.io.FileNotFoundException
+import java.io.ObjectInputStream
+import java.io.ObjectOutputStream
+
+@TargetApi(24)
+object DirectBoot {
+    private val file = File(app.deviceContext.noBackupFilesDir, "directBootProfile")
+
+    fun getDeviceProfile(): Profile? = try {
+        ObjectInputStream(file.inputStream()).use { it.readObject() as Profile }
+    } catch (_: FileNotFoundException) { null }
+
+    fun clean() {
+        file.delete()
+        File(app.deviceContext.noBackupFilesDir, BaseService.CONFIG_FILE).delete()
+    }
+
+    fun update() {
+        val profile = ProfileManager.getProfile(DataStore.profileId)    // app.currentProfile will call this
+        if (profile == null) clean() else ObjectOutputStream(file.outputStream()).use { it.writeObject(profile) }
+    }
+}

mobile/src/main/java/com/github/shadowsocks/utils/TcpFastOpen.kt

@@ -42,6 +42,7 @@ object TcpFastOpen {
 
     val sendEnabled: Boolean get() {
         val file = File("/proc/sys/net/ipv4/tcp_fastopen")
+        // File.readText doesn't work since this special file will return length 0
         return file.canRead() && file.bufferedReader().use { it.readText() }.trim().toInt() and 1 > 0
     }