pass network device fd via unix socket instead of inheritance

Workaround for new shared memory restrictions added in Android 10
preventing file descriptor leakage to sub-processes.

This change set BREAKS ENCRYPTED PRIVATE KEYS SUPPORT.

GitHub: https://github.com/pacien/tincapp/issues/92

4 files changed, 46 insertions, 47 deletions

diff --git a/app/src/main/java/org/pacien/tincapp/commands/Executor.kt b/app/src/main/java/org/pacien/tincapp/commands/Executor.kt
index 29e011f..0a8a774 100644
--- a/app/src/main/java/org/pacien/tincapp/commands/Executor.kt
+++ b/app/src/main/java/org/pacien/tincapp/commands/Executor.kt
@@ -1,6 +1,6 @@
 /*
  * Tinc App, an Android binding and user interface for the tinc mesh VPN daemon
- * Copyright (C) 2017-2018 Pacien TRAN-GIRARD
+ * Copyright (C) 2017-2020 Pacien TRAN-GIRARD
  *
  * 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
@@ -30,42 +30,10 @@ import java.io.InputStreamReader
  * @author pacien
  */
 internal object Executor {
-  private const val FAILED = -1
-  private const val SUCCESS = 0
-
   class CommandExecutionException(msg: String) : Exception(msg)
 
-  init {
-    System.loadLibrary("exec")
-  }
-
-  /**
-   * @return FAILED (-1) on error, forked child PID otherwise
-   */
-  private external fun forkExec(args: Array<String>): Int
-
-  /**
-   * @return FAILED (-1) on error, the exit status of the process otherwise
-   */
-  private external fun wait(pid: Int): Int
-
   private fun read(stream: InputStream) = BufferedReader(InputStreamReader(stream)).readLines()
 
-  fun forkExec(cmd: Command): CompletableFuture<Unit> {
-    val pid = forkExec(cmd.asArray()).also {
-      if (it == FAILED) throw CommandExecutionException("Could not fork child process.")
-    }
-
-    return runAsyncTask {
-      val exitCode = wait(pid)
-      when (exitCode) {
-        SUCCESS -> Unit
-        FAILED -> throw CommandExecutionException("Process terminated abnormally.")
-        else -> throw CommandExecutionException("Non-zero exit status code ($exitCode).")
-      }
-    }
-  }
-
   fun run(cmd: Command): Process = try {
     ProcessBuilder(cmd.asList()).start()
   } catch (e: IOException) {
diff --git a/app/src/main/java/org/pacien/tincapp/commands/Tincd.kt b/app/src/main/java/org/pacien/tincapp/commands/Tincd.kt
index 92be0f5..c0b0048 100644
--- a/app/src/main/java/org/pacien/tincapp/commands/Tincd.kt
+++ b/app/src/main/java/org/pacien/tincapp/commands/Tincd.kt
@@ -1,6 +1,6 @@
 /*
  * Tinc App, an Android binding and user interface for the tinc mesh VPN daemon
- * Copyright (C) 2017-2018 Pacien TRAN-GIRARD
+ * Copyright (C) 2017-2020 Pacien TRAN-GIRARD
  *
  * 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
@@ -18,20 +18,23 @@
 
 package org.pacien.tincapp.commands
 
+import java8.util.concurrent.CompletableFuture
 import org.pacien.tincapp.context.AppPaths
+import java.io.File
 
 /**
  * @author pacien
  */
 object Tincd {
-  fun start(netName: String, deviceFd: Int, ed25519PrivateKeyFd: Int? = null, rsaPrivateKeyFd: Int? = null) =
-    Executor.forkExec(Command(AppPaths.tincd().absolutePath)
+  fun start(netName: String, device: String, ed25519PrivateKey: File? = null, rsaPrivateKey: File? = null): CompletableFuture<Unit> =
+    Executor.call(Command(AppPaths.tincd().absolutePath)
       .withOption("no-detach")
       .withOption("config", AppPaths.confDir(netName).absolutePath)
       .withOption("pidfile", AppPaths.pidFile(netName).absolutePath)
       .withOption("logfile", AppPaths.logFile(netName).absolutePath)
       .withOption("option", "DeviceType=fd")
-      .withOption("option", "Device=$deviceFd")
-      .apply { if (ed25519PrivateKeyFd != null) withOption("option", "Ed25519PrivateKeyFile=/proc/self/fd/$ed25519PrivateKeyFd") }
-      .apply { if (rsaPrivateKeyFd != null) withOption("option", "PrivateKeyFile=/proc/self/fd/$rsaPrivateKeyFd") })
+      .withOption("option", "Device=@$device")
+      .apply { if (ed25519PrivateKey != null) withOption("option", "Ed25519PrivateKeyFile=${ed25519PrivateKey.absolutePath}") }
+      .apply { if (rsaPrivateKey != null) withOption("option", "PrivateKeyFile=${rsaPrivateKey.absolutePath}") }
+    ).thenApply { }
 }
diff --git a/app/src/main/java/org/pacien/tincapp/context/App.kt b/app/src/main/java/org/pacien/tincapp/context/App.kt
index a877929..4d8d5d0 100644
--- a/app/src/main/java/org/pacien/tincapp/context/App.kt
+++ b/app/src/main/java/org/pacien/tincapp/context/App.kt
@@ -1,6 +1,6 @@
 /*
  * Tinc App, an Android binding and user interface for the tinc mesh VPN daemon
- * Copyright (C) 2017-2019 Pacien TRAN-GIRARD
+ * Copyright (C) 2017-2020 Pacien TRAN-GIRARD
  *
  * 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
@@ -21,6 +21,7 @@ package org.pacien.tincapp.context
 import android.app.Application
 import android.content.Context
 import android.content.Intent
+import android.content.pm.ApplicationInfo
 import android.net.Uri
 import android.os.Build
 import android.os.Handler
@@ -47,7 +48,7 @@ class App : Application() {
 
   private fun setupCrashHandler() {
     val logger = LoggerFactory.getLogger(this.javaClass)
-    val systemCrashHandler = Thread.getDefaultUncaughtExceptionHandler()
+    val systemCrashHandler = Thread.getDefaultUncaughtExceptionHandler()!!
     val crashRecorder = CrashRecorder(logger, systemCrashHandler)
     Thread.setDefaultUncaughtExceptionHandler(crashRecorder)
   }
@@ -61,6 +62,11 @@ class App : Application() {
     fun getContext() = appContext!!
     fun getResources() = getContext().resources!!
 
+    fun getApplicationInfo(): ApplicationInfo =
+      getContext()
+        .packageManager
+        .getApplicationInfo(BuildConfig.APPLICATION_ID, 0)
+
     fun alert(@StringRes title: Int, msg: String, manualLink: String? = null) =
       notificationManager.notifyError(appContext!!.getString(title), msg, manualLink)
 
diff --git a/app/src/main/java/org/pacien/tincapp/service/TincVpnService.kt b/app/src/main/java/org/pacien/tincapp/service/TincVpnService.kt
index 40e9004..48cb1df 100644
--- a/app/src/main/java/org/pacien/tincapp/service/TincVpnService.kt
+++ b/app/src/main/java/org/pacien/tincapp/service/TincVpnService.kt
@@ -1,6 +1,6 @@
 /*
  * Tinc App, an Android binding and user interface for the tinc mesh VPN daemon
- * Copyright (C) 2017-2019 Pacien TRAN-GIRARD
+ * Copyright (C) 2017-2020 Pacien TRAN-GIRARD
  *
  * 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
@@ -21,6 +21,7 @@ package org.pacien.tincapp.service
 import android.app.Service
 import android.content.Context
 import android.content.Intent
+import android.net.LocalServerSocket
 import android.net.VpnService
 import android.os.ParcelFileDescriptor
 import androidx.localbroadcastmanager.content.LocalBroadcastManager
@@ -43,6 +44,7 @@ import org.pacien.tincapp.intent.Actions
 import org.pacien.tincapp.utils.TincKeyring
 import org.slf4j.LoggerFactory
 import java.io.FileNotFoundException
+import java.security.AccessControlException
 
 /**
  * @author pacien
@@ -100,6 +102,7 @@ class TincVpnService : VpnService() {
     log.info("Starting tinc daemon for network \"$netName\".")
     if (isConnected() || getCurrentNetName() != null) stopVpn().join()
 
+    // FIXME: pass decrypted private keys via temp file
     val privateKeys = try {
       TincConfiguration.fromTincConfiguration(AppPaths.existing(AppPaths.tincConfFile(netName))).let { tincCfg ->
         Pair(