Add signature checking to plugin platform

mobile/src/main/res/values/strings.xml

@@ -142,5 +142,6 @@
   <string name="plugin_configure">Configure…</string>
   <string name="plugin_disabled">Disabled</string>
   <string name="plugin_unknown">Unknown plugin %s</string>
+  <string name="plugin_untrusted">Warning: This plugin does not seem to come from a known trusted source.</string>
   <string name="profile_plugin">Plugin: %s</string>
 </resources>

mobile/src/main/scala/com/github/shadowsocks/ProfileConfigFragment.scala

@@ -81,6 +81,8 @@ class ProfileConfigFragment extends PreferenceFragment with OnMenuItemClickListe
       app.editor.putString(Key.plugin, pluginConfiguration.toString).putBoolean(Key.dirty, true).apply()
       pluginConfigure.setEnabled(!TextUtils.isEmpty(selected))
       pluginConfigure.setText(pluginConfiguration.selectedOptions.toString)
+      if (!PluginManager.fetchPlugins()(selected).trusted)
+        Snackbar.make(getView, R.string.plugin_untrusted, Snackbar.LENGTH_LONG).show()
       true
     })
     pluginConfigure.setOnPreferenceChangeListener(onPluginConfigureChanged)

mobile/src/main/scala/com/github/shadowsocks/plugin/Plugin.scala

@@ -11,4 +11,5 @@ abstract class Plugin {
   def icon: Drawable = null
   def defaultConfig: String = null
   def packageName: String = null
+  def trusted: Boolean = true
 }

mobile/src/main/scala/com/github/shadowsocks/plugin/PluginManager.scala

@@ -2,11 +2,11 @@ package com.github.shadowsocks.plugin
 
 import java.io.{File, FileNotFoundException, FileOutputStream, IOException}
 
-import android.content.pm.PackageManager
+import android.content.pm.{PackageManager, Signature}
 import android.content.{BroadcastReceiver, ContentResolver, Intent}
 import android.net.Uri
 import android.os.Bundle
-import android.util.Log
+import android.util.{Base64, Log}
 import com.github.shadowsocks.ShadowsocksApplication.app
 import com.github.shadowsocks.utils.CloseUtils.autoClose
 import com.github.shadowsocks.utils.{Commandline, IOUtils}
@@ -19,6 +19,39 @@ import scala.collection.mutable.ListBuffer
   * @author Mygod
   */
 object PluginManager {
+  /**
+    * Trusted signatures by the app. Third-party fork should add their public key to their fork if the developer wishes
+    * to publish or has published plugins for this app. You can obtain your public key by executing:
+    *
+    * $ keytool -export -alias key-alias -keystore /path/to/keystore.jks -rfc
+    *
+    * If you don't plan to publish any plugin but is developing/has developed some, it's not necessary to add your
+    * public key yet since it will also automatically trust packages signed by the same signatures, e.g. debug keys.
+    */
+  lazy val trustedSignatures: Set[Signature] =
+    app.getPackageManager.getPackageInfo(app.getPackageName, PackageManager.GET_SIGNATURES).signatures.toSet +
+    new Signature(Base64.decode(  // @Mygod
+      """
+        |MIIDWzCCAkOgAwIBAgIEUzfv8DANBgkqhkiG9w0BAQsFADBdMQswCQYDVQQGEwJD
+        |TjEOMAwGA1UECBMFTXlnb2QxDjAMBgNVBAcTBU15Z29kMQ4wDAYDVQQKEwVNeWdv
+        |ZDEOMAwGA1UECxMFTXlnb2QxDjAMBgNVBAMTBU15Z29kMCAXDTE0MDUwMjA5MjQx
+        |OVoYDzMwMTMwOTAyMDkyNDE5WjBdMQswCQYDVQQGEwJDTjEOMAwGA1UECBMFTXln
+        |b2QxDjAMBgNVBAcTBU15Z29kMQ4wDAYDVQQKEwVNeWdvZDEOMAwGA1UECxMFTXln
+        |b2QxDjAMBgNVBAMTBU15Z29kMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKC
+        |AQEAjm5ikHoP3w6zavvZU5bRo6Birz41JL/nZidpdww21q/G9APA+IiJMUeeocy0
+        |L7/QY8MQZABVwNq79LXYWJBcmmFXM9xBPgDqQP4uh9JsvazCI9bvDiMn92mz9HiS
+        |Sg9V4KGg0AcY0r230KIFo7hz+2QBp1gwAAE97myBfA3pi3IzJM2kWsh4LWkKQMfL
+        |M6KDhpb4mdDQnHlgi4JWe3SYbLtpB6whnTqjHaOzvyiLspx1tmrb0KVxssry9KoX
+        |YQzl56scfE/QJX0jJ5qYmNAYRCb4PibMuNSGB2NObDabSOMAdT4JLueOcHZ/x9tw
+        |agGQ9UdymVZYzf8uqc+29ppKdQIDAQABoyEwHzAdBgNVHQ4EFgQUBK4uJ0cqmnho
+        |6I72VmOVQMvVCXowDQYJKoZIhvcNAQELBQADggEBABZQ3yNESQdgNJg+NRIcpF9l
+        |YSKZvrBZ51gyrC7/2ZKMpRIyXruUOIrjuTR5eaONs1E4HI/uA3xG1eeW2pjPxDnO
+        |zgM4t7EPH6QbzibihoHw1MAB/mzECzY8r11PBhDQlst0a2hp+zUNR8CLbpmPPqTY
+        |RSo6EooQ7+NBejOXysqIF1q0BJs8Y5s/CaTOmgbL7uPCkzArB6SS/hzXgDk5gw6v
+        |wkGeOtzcj1DlbUTvt1s5GlnwBTGUmkbLx+YUje+n+IBgMbohLUDYBtUHylRVgMsc
+        |1WS67kDqeJiiQZvrxvyW6CZZ/MIGI+uAkkj3DqJpaZirkwPgvpcOIrjZy0uFvQM=
+      """, Base64.DEFAULT))
+
   private var receiver: BroadcastReceiver = _
   private var cachedPlugins: Map[String, Plugin] = _
   def fetchPlugins(): Map[String, Plugin] = {

mobile/src/main/scala/com/github/shadowsocks/plugin/ResolvedPlugin.scala

@@ -19,4 +19,6 @@ abstract class ResolvedPlugin(resolveInfo: ResolveInfo, packageManager: PackageM
   override final lazy val icon: Drawable = resolveInfo.loadIcon(packageManager)
   override final lazy val defaultConfig: String = metaData.getString(PluginContract.METADATA_KEY_DEFAULT_CONFIG)
   override def packageName: String = resolveInfo.resolvePackageName
+  override final lazy val trusted: Boolean = packageManager.getPackageInfo(packageName, PackageManager.GET_SIGNATURES)
+    .signatures.exists(PluginManager.trustedSignatures.contains)
 }