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

10 files changed, 55 insertions, 116 deletions

diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
index 073f7d7..6449aeb 100644
--- a/app/CMakeLists.txt
+++ b/app/CMakeLists.txt
@@ -54,9 +54,8 @@ ExternalProject_Add(libressl
 
 ExternalProject_Add(tinc
   DEPENDS           lzo libressl
-  URL               https://github.com/gsliepen/tinc/archive/017a7fb57655d9b1d706ee78f7e3d0000411b883.tar.gz
-  URL_HASH          SHA256=27f361706d09f81fbbef7021f37adf5375f01857b23272a490df066ca290a530
-  PATCH_COMMAND     sed -i -e "s/test(void)/test(void *x)/" <SOURCE_DIR>/m4/attribute.m4
+  URL               https://github.com/gsliepen/tinc/archive/6682a0d29cbb70b216a3fe02f2812963dee607d0.tar.gz
+  URL_HASH          SHA256=ffb0e6c02b0112c095366b3baa89f5ed56cc5f644be40268696ce7741e76452a
   CONFIGURE_COMMAND autoreconf -fsi <SOURCE_DIR> &&
                     <SOURCE_DIR>/configure ${xCONFIG}
                       --with-openssl=${CMAKE_CURRENT_BINARY_DIR}/usr/local
@@ -72,5 +71,5 @@ ExternalProject_Add(tinc
                     rm -r <BINARY_DIR>
 )
 
-add_library(exec SHARED src/main/c/exec.c)
-add_dependencies(exec tinc)
+add_library(main SHARED src/main/c/main.c)
+add_dependencies(main tinc)
diff --git a/app/build.gradle b/app/build.gradle
index 5ef4f4a..25e449e 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -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
@@ -35,7 +35,7 @@ android {
   defaultConfig {
     applicationId 'org.pacien.tincapp'
     minSdkVersion 21
-    targetSdkVersion 28 // FIXME: bad file descriptor in daemon when targeting 29
+    targetSdkVersion 29
     multiDexEnabled true
     versionCode 28
     versionName '0.28'
diff --git a/app/src/main/c/exec.c b/app/src/main/c/exec.c
deleted file mode 100644
index c335b20..0000000
--- a/app/src/main/c/exec.c
+++ /dev/null
@@ -1,60 +0,0 @@
-/*
- * Tinc App, an Android binding and user interface for the tinc mesh VPN daemon
- * Copyright (C) 2017-2018 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
- * 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 <https://www.gnu.org/licenses/>.
- */
-
-#include <jni.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <sys/wait.h>
-
-static inline const char **to_string_array(JNIEnv *env, jobjectArray ja) {
-  const int len = (*env)->GetArrayLength(env, ja);
-  const char **ca = calloc((size_t) len + 1, sizeof(char *));
-
-  for (int i = 0; i < len; ++i) {
-    jstring jstr = (jstring) (*env)->GetObjectArrayElement(env, ja, i);
-    ca[i] = (*env)->GetStringUTFChars(env, jstr, NULL);
-  }
-
-  ca[len] = NULL;
-  return ca;
-}
-
-static inline void exec(const char **argcv) {
-  execv(argcv[0], (char *const *) argcv);
-  exit(1);
-}
-
-JNIEXPORT jint JNICALL
-Java_org_pacien_tincapp_commands_Executor_forkExec(JNIEnv *env, __attribute__((unused)) jclass class, jobjectArray args) {
-  pid_t pid = fork();
-  switch (pid) {
-    case 0:
-      exec(to_string_array(env, args));
-      return 0;
-
-    default:
-      return pid;
-  }
-}
-
-JNIEXPORT jint JNICALL
-Java_org_pacien_tincapp_commands_Executor_wait(__attribute__((unused))JNIEnv *env, __attribute__((unused)) jclass class, jint pid) {
-  int status;
-  waitpid(pid, &status, 0);
-  return WIFEXITED(status) ? WEXITSTATUS(status) : -1;
-}
diff --git a/app/src/main/c/main.c b/app/src/main/c/main.c
new file mode 100644
index 0000000..68007d8
--- /dev/null
+++ b/app/src/main/c/main.c
@@ -0,0 +1 @@
+// This file intentionally left blank.
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") }
+      .withOption("option", "Device=@$device")
+      .apply { if (ed25519PrivateKey != null) withOption("option", "Ed25519PrivateKeyFile=${ed25519PrivateKey.absolutePath}") }