Add a configurable white-list for backup storage

app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageRootFetcher.kt

@@ -49,10 +49,11 @@ internal interface RemovableStorageListener {
     fun onStorageChanged()
 }
 
-internal class StorageRootFetcher(private val context: Context) {
+internal class StorageRootFetcher(private val context: Context, private val isRestore: Boolean) {
 
     private val packageManager = context.packageManager
     private val contentResolver = context.contentResolver
+    private val whitelistedAuthorities = context.resources.getStringArray(R.array.storage_authority_whitelist)
 
     private var listener: RemovableStorageListener? = null
     private val observer = object : ContentObserver(Handler()) {
@@ -85,7 +86,7 @@ internal class StorageRootFetcher(private val context: Context) {
                 roots.addAll(getRoots(providerInfo))
             }
         }
-        checkOrAddUsbRoot(roots)
+        if (isAuthoritySupported(AUTHORITY_STORAGE)) checkOrAddUsbRoot(roots)
         return roots
     }
 
@@ -165,9 +166,17 @@ internal class StorageRootFetcher(private val context: Context) {
         } else if (authority == AUTHORITY_DOWNLOADS) {
             Log.w(TAG, "Not supporting $AUTHORITY_DOWNLOADS")
             false
+        } else if (!isAuthoritySupported(authority)) {
+            Log.w(TAG, "Authority $authority is not white-listed, ignoring...")
+            false
         } else true
     }
 
+    private fun isAuthoritySupported(authority: String): Boolean {
+        // just restrict where to store backups, restoring can be more free for forward compatibility
+        return isRestore || whitelistedAuthorities.contains(authority)
+    }
+
     private fun Cursor.getString(columnName: String): String? {
         val index = getColumnIndex(columnName)
         return if (index != -1) getString(index) else null

app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageViewModel.kt

@@ -37,7 +37,7 @@ internal abstract class StorageViewModel(private val app: Application) : Android
     protected val mLocationChecked = MutableLiveEvent<LocationResult>()
     internal val locationChecked: LiveEvent<LocationResult> get() = mLocationChecked
 
-    private val storageRootFetcher by lazy { StorageRootFetcher(app) }
+    private val storageRootFetcher by lazy { StorageRootFetcher(app, isRestoreOperation) }
     private var storageRoot: StorageRoot? = null
 
     internal var isSetupWizard: Boolean = false

app/src/main/res/values/config.xml

@@ -1,4 +1,11 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <bool name="show_restore_in_settings">true</bool>
+
+    <string-array name="storage_authority_whitelist">
+        <item>com.android.externalstorage.documents</item>
+        <item>org.nextcloud.documents</item>
+        <item>org.nextcloud.beta.documents</item>
+    </string-array>
+
 </resources>