Check if backup folder is writable on backup

(cherry picked from commit 8aad79fd3e14eb885724a5e5790803c289be2f25)

src/NzbDrone.Common/ArchiveService.cs

@@ -42,8 +42,10 @@ namespace NzbDrone.Common
 
         public void CreateZip(string path, IEnumerable<string> files)
         {
-            using (var zipFile = ZipFile.Create(path))
+            _logger.Debug("Creating archive {0}", path);
-            {
+
+            using var zipFile = ZipFile.Create(path);
+
             zipFile.BeginUpdate();
 
             foreach (var file in files)
@@ -53,7 +55,6 @@ namespace NzbDrone.Common
 
             zipFile.CommitUpdate();
         }
-        }
 
         private void ExtractZip(string compressedFile, string destination)
         {

src/NzbDrone.Core/Backup/BackupService.cs

@@ -66,12 +66,19 @@ namespace NzbDrone.Core.Backup
         {
             _logger.ProgressInfo("Starting Backup");
 
+            var backupFolder = GetBackupFolder(backupType);
+
             _diskProvider.EnsureFolder(_backupTempFolder);
-            _diskProvider.EnsureFolder(GetBackupFolder(backupType));
+            _diskProvider.EnsureFolder(backupFolder);
+
+            if (!_diskProvider.FolderWritable(backupFolder))
+            {
+                throw new UnauthorizedAccessException($"Backup folder {backupFolder} is not writable");
+            }
 
             var dateNow = DateTime.Now;
             var backupFilename = $"prowlarr_backup_v{BuildInfo.Version}_{dateNow:yyyy.MM.dd_HH.mm.ss}.zip";
-            var backupPath = Path.Combine(GetBackupFolder(backupType), backupFilename);
+            var backupPath = Path.Combine(backupFolder, backupFilename);
 
             Cleanup();