use private temp files to pass decrypted private keys

Android 10 (API 29) doesn't allow us to pass them by sharing file
descriptors anymore, making the use of temp files mandatory.

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

1 files changed, 23 insertions, 9 deletions

diff --git a/app/src/main/java/org/pacien/tincapp/utils/TincKeyring.kt b/app/src/main/java/org/pacien/tincapp/utils/TincKeyring.kt
index bae38ac..89bb246 100644
--- a/app/src/main/java/org/pacien/tincapp/utils/TincKeyring.kt
+++ b/app/src/main/java/org/pacien/tincapp/utils/TincKeyring.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
@@ -18,10 +18,11 @@
 
 package org.pacien.tincapp.utils
 
-import android.os.ParcelFileDescriptor
 import org.pacien.tincapp.commands.TincApp
+import org.pacien.tincapp.context.AppPaths
 import java.io.File
 import java.io.FileNotFoundException
+import java.io.FileWriter
 
 /**
  * @author pacien
@@ -33,12 +34,25 @@ object TincKeyring {
     false
   }
 
-  fun openPrivateKey(f: File?, passphrase: String?): ParcelFileDescriptor? {
-    if (f == null || !f.exists() || passphrase == null) return null
-    val pipe = ParcelFileDescriptor.createPipe()
-    val decryptedKey = PemUtils.decrypt(PemUtils.read(f), passphrase)
-    val outputStream = ParcelFileDescriptor.AutoCloseOutputStream(pipe[1])
-    PemUtils.write(decryptedKey, outputStream.writer())
-    return pipe[0]
+  fun unlockKey(target: String, input: File?, passphrase: String?): File? {
+    if (input == null || !input.exists() || passphrase == null) return null
+    val decryptedKey = PemUtils.decrypt(PemUtils.read(input), passphrase)
+    val decryptedFile = tempKey(target)
+    PemUtils.write(decryptedKey, FileWriter(decryptedFile, false))
+    return decryptedFile
+  }
+
+  private fun tempKey(name: String): File {
+    val file = File(AppPaths.internalCacheDir(), name)
+    file.createNewFile()
+    file.deleteOnExit()
+    file.makePrivate()
+    return file
+  }
+
+  private fun File.makePrivate() {
+    this.setExecutable(false, false)
+    this.setReadable(true, true)
+    this.setWritable(true, true)
   }
 }