Add server public key check before purchases

app/src/main/java/io/timelimit/android/sync/network/CanDoPurchaseStatus.kt

@@ -1,5 +1,5 @@
 /*
- * TimeLimit Copyright <C> 2019 Jonas Lochmann
+ * TimeLimit Copyright <C> 2019 - 2020 Jonas Lochmann
  *
  * 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
@@ -15,17 +15,41 @@
  */
 package io.timelimit.android.sync.network
 
-enum class CanDoPurchaseStatus {
+import android.util.Base64
-    Yes, NotDueToOldPurchase, NoForUnknownReason
+import android.util.JsonReader
+
+sealed class CanDoPurchaseStatus {
+    class Yes(val publicKey: ByteArray?): CanDoPurchaseStatus()
+    object NoForUnknownReason: CanDoPurchaseStatus()
+    object NotDueToOldPurchase: CanDoPurchaseStatus()
 }
 
 object CanDoPurchaseParser {
+    private const val CAN_DO_PURCHASE = "canDoPurchase"
+    private const val GPLAY_PUBLIC_KEY = "googlePlayPublicKey"
     private const val YES = "yes"
     private const val NO_DUE_TO_OLD_PURCHASE = "no due to old purchase"
 
-    fun parse(value: String) = when(value) {
+    fun parse(reader: JsonReader): CanDoPurchaseStatus {
-        YES -> CanDoPurchaseStatus.Yes
+        reader.beginObject()
-        NO_DUE_TO_OLD_PURCHASE -> CanDoPurchaseStatus.NotDueToOldPurchase
+
-        else -> CanDoPurchaseStatus.NoForUnknownReason
+        var canDoPurchaseStatus: String? = null
+        var publicKey: ByteArray? = null
+
+        while (reader.hasNext()) {
+            when (reader.nextName()) {
+                CAN_DO_PURCHASE -> canDoPurchaseStatus = reader.nextString()
+                GPLAY_PUBLIC_KEY -> publicKey = Base64.decode(reader.nextString(), 0)
+                else -> reader.skipValue()
+            }
+        }
+
+        reader.endObject()
+
+        return when (canDoPurchaseStatus!!) {
+            YES -> CanDoPurchaseStatus.Yes(publicKey)
+            NO_DUE_TO_OLD_PURCHASE -> CanDoPurchaseStatus.NotDueToOldPurchase
+            else -> CanDoPurchaseStatus.NoForUnknownReason
+        }
     }
 }

app/src/main/java/io/timelimit/android/sync/network/api/HttpServerApi.kt

@@ -476,18 +476,8 @@ class HttpServerApi(private val endpointWithoutSlashAtEnd: String): ServerApi {
 
             return Threads.network.executeAndWait {
                 val reader = JsonReader(response.body()!!.charStream())
-                var status: CanDoPurchaseStatus? = null
 
-                reader.beginObject()
+                CanDoPurchaseParser.parse(reader)
-                while (reader.hasNext()) {
-                    when (reader.nextName()) {
-                        "canDoPurchase" -> status = CanDoPurchaseParser.parse(reader.nextString())
-                        else -> reader.skipValue()
-                    }
-                }
-                reader.endObject()
-
-                status!!
             }
         }
     }

app/src/main/java/io/timelimit/android/ui/payment/ActivityPurchaseModel.kt

@@ -1,5 +1,5 @@
 /*
- * TimeLimit Copyright <C> 2019 Jonas Lochmann
+ * TimeLimit Copyright <C> 2019 - 2020 Jonas Lochmann
  *
  * 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
@@ -194,7 +194,7 @@ class ActivityPurchaseModel(application: Application): AndroidViewModel(applicat
                                 return@runAsync
                             }
 
-                            if (server.api.canDoPurchase(server.deviceAuthToken) != CanDoPurchaseStatus.Yes) {
+                            if (!(server.api.canDoPurchase(server.deviceAuthToken) is CanDoPurchaseStatus.Yes)) {
                                 throw IOException("can not do purchase right now")
                             }
                         }

app/src/main/java/io/timelimit/android/ui/payment/PurchaseFragment.kt

@@ -90,6 +90,7 @@ class PurchaseFragment : Fragment(), FragmentWithCustomTitle {
                             PurchaseFragmentNetworkError -> getString(R.string.error_network)
                             PurchaseFragmentExistingPaymentError -> getString(R.string.purchase_error_existing_payment)
                             PurchaseFragmentServerRejectedError -> getString(R.string.purchase_error_server_rejected)
+                            PurchaseFragmentServerHasDifferentPublicKey -> getString(R.string.purchase_error_server_different_key)
                         }
 
                         binding.showRetryButton = when (fragmentStatus) {

app/src/main/java/io/timelimit/android/ui/payment/PurchaseModel.kt

@@ -16,6 +16,7 @@
 package io.timelimit.android.ui.payment
 
 import android.app.Application
+import android.util.Base64
 import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.MutableLiveData
 import io.timelimit.android.BuildConfig
@@ -65,22 +66,26 @@ class PurchaseModel(application: Application): AndroidViewModel(application) {
                         else
                             CanDoPurchaseStatus.NoForUnknownReason
 
-                        if (canDoPurchase == CanDoPurchaseStatus.Yes) {
+                        if (canDoPurchase is CanDoPurchaseStatus.Yes) {
-                            val checkout = Checkout.forApplication(application.billing)
+                            if (canDoPurchase.publicKey?.equals(Base64.decode(BuildConfig.googlePlayKey, 0)) == false) {
+                                statusInternal.value = PurchaseFragmentServerHasDifferentPublicKey
+                            } else {
+                                val checkout = Checkout.forApplication(application.billing)
 
-                            checkout.startAsync().use {
+                                checkout.startAsync().use {
-                                if (!it.billingSupported) {
+                                    if (!it.billingSupported) {
-                                    statusInternal.value = PurchaseFragmentErrorBillingNotSupportedByDevice
+                                        statusInternal.value = PurchaseFragmentErrorBillingNotSupportedByDevice
-                                } else {
+                                    } else {
-                                    val skus = it.requests.getSkusAsync(
+                                        val skus = it.requests.getSkusAsync(
-                                            ProductTypes.IN_APP,
+                                                ProductTypes.IN_APP,
-                                            PurchaseIds.BUY_SKUS
+                                                PurchaseIds.BUY_SKUS
-                                    )
+                                        )
 
-                                    statusInternal.value = PurchaseFragmentReady(
+                                        statusInternal.value = PurchaseFragmentReady(
-                                            monthPrice = skus.getSku(PurchaseIds.SKU_MONTH)?.price.toString(),
+                                                monthPrice = skus.getSku(PurchaseIds.SKU_MONTH)?.price.toString(),
-                                            yearPrice = skus.getSku(PurchaseIds.SKU_YEAR)?.price.toString()
+                                                yearPrice = skus.getSku(PurchaseIds.SKU_YEAR)?.price.toString()
-                                    )
+                                        )
+                                    }
                                 }
                             }
                         } else if (canDoPurchase == CanDoPurchaseStatus.NotDueToOldPurchase) {
@@ -110,3 +115,4 @@ object PurchaseFragmentErrorBillingNotSupportedByAppVariant: PurchaseFragmentUnr
 object PurchaseFragmentNetworkError: PurchaseFragmentRecoverableError()
 object PurchaseFragmentExistingPaymentError: PurchaseFragmentUnrecoverableError()
 object PurchaseFragmentServerRejectedError: PurchaseFragmentUnrecoverableError()
+object PurchaseFragmentServerHasDifferentPublicKey: PurchaseFragmentUnrecoverableError()

app/src/main/res/values-de/strings-purchase.xml

@@ -41,6 +41,7 @@
         Sie haben bereits bezahlt. Sie können die Vollversion erst kurz vor dem Ablaufen (oder danach) verlängern
     </string>
     <string name="purchase_error_server_rejected">Der Server akzeptiert momentan keine Bezahlungen</string>
+    <string name="purchase_error_server_different_key">Der Server unterstützt Bezahlungen, aber nicht über diesen App-Build</string>
 
     <string name="purchase_done_title">Bezahlung abgeschlossen</string>
     <string name="purchase_done_text">Betätigen Sie die Zurück-Taste, um zur App zurückzukehren</string>

app/src/main/res/values/strings-purchase.xml

@@ -41,6 +41,7 @@
         You can only extend the premium version if it expired or shortly before that.
     </string>
     <string name="purchase_error_server_rejected">The server does not accept payments currently</string>
+    <string name="purchase_error_server_different_key">The server does support payments, but not using this app build</string>
 
     <string name="purchase_done_title">Purchase succeeded</string>
     <string name="purchase_done_text">Press back to go back to the App</string>