Fix signature checks in ResolvedPlugin

mobile/src/main/java/com/github/shadowsocks/App.kt

@@ -71,7 +71,10 @@ class App : Application() {
     val deviceContext: Context by lazy { if (Build.VERSION.SDK_INT < 24) this else DeviceContext(this) }
     val remoteConfig: FirebaseRemoteConfig by lazy { FirebaseRemoteConfig.getInstance() }
     private val tracker: Tracker by lazy { GoogleAnalytics.getInstance(deviceContext).newTracker(R.xml.tracker) }
-    val info: PackageInfo by lazy { packageManager.getPackageInfo(packageName, PackageManager.GET_SIGNATURES) }
+    val info: PackageInfo by lazy { getPackageInfo(packageName) }
+
+    fun getPackageInfo(packageName: String) =
+            packageManager.getPackageInfo(packageName, PackageManager.GET_SIGNATURES)!!
 
     fun startService() {
         val intent = Intent(this, BaseService.serviceClass.java)

mobile/src/main/java/com/github/shadowsocks/plugin/ResolvedPlugin.kt

@@ -33,5 +33,7 @@ abstract class ResolvedPlugin(protected val resolveInfo: ResolveInfo) : Plugin()
     override val icon: Drawable by lazy { resolveInfo.loadIcon(app.packageManager) }
     override val defaultConfig: String by lazy { metaData.getString(PluginContract.METADATA_KEY_DEFAULT_CONFIG) }
     override val packageName: String get() = resolveInfo.resolvePackageName
-    override val trusted by lazy { app.info.signatures.any(PluginManager.trustedSignatures::contains) }
+    override val trusted by lazy {
+        app.getPackageInfo(packageName).signatures.any(PluginManager.trustedSignatures::contains)
+    }
 }