Correct recryption for stamping, permissions for -combine-pages

cpdf.ml

@@ -2177,6 +2177,10 @@ let stamp position fast scale_to_fit isover range over pdf =
           ~rotations:[Pdfmerge.DNR; Pdfmerge.DNR]
           false false ["a"; "b"] [pdf; over_firstpage_pdf] [pageseqs; [1]]
       in
+        let merged =
+          {merged with Pdf.saved_encryption = pdf.Pdf.saved_encryption}
+        in
+          let merged = copy_id true pdf merged in
           let renamed_pdf =
             Pdfpage.change_pages true
               merged (Pdfpage.renumber_pages merged (Pdfpage.pages_of_pagetree merged))

cpdfcommand.ml

@@ -556,7 +556,9 @@ let banned banlist = function
   | ListBookmarks | ImageResolution _ | MissingFonts
   | PrintPageLabels | Clean | Compress | Decompress
   | RemoveUnusedResources | ChangeId | CopyId _ -> false (* Always allowed *)
-  | Decrypt | Encrypt -> true (* Never allowed *)
+  (* Combine pages is not allowed because we would not know where to get the
+  -recrypt from -- the first or second file? *)
+  | Decrypt | Encrypt | CombinePages _ -> true (* Never allowed *)
   | ExtractText | ExtractImages | ExtractFontFile -> mem Pdfcrypt.NoExtract banlist
   | AddBookmarks _ | PadBefore | PadAfter | PadEvery _ | PadMultiple _
   | Merge | Split | SplitOnBookmarks _ | RotateContents _ | Rotate _