Network: try-with with specific exceptions

Previously, this block had a generic try-with which is
dangerous since it can cause unwanted behaviours and
cause confusion for future developers.

Author: parhamsaremi

NOnion/Exceptions.fs

@@ -26,6 +26,9 @@ type CircuitTruncatedException internal (reason: DestroyReason) =
 type CircuitDestroyedException internal (reason: DestroyReason) =
     inherit NOnionException(sprintf "Circuit got destroyed, reason %A" reason)
 
+type CircuitDecryptionFailedException internal () =
+    inherit NOnionException(sprintf "Circuit Decryption Failed")
+
 type TimeoutErrorException internal () =
     inherit NOnionException("Time limit exceeded for operation")
 

NOnion/Network/TorCircuit.fs

@@ -336,7 +336,8 @@ and TorCircuit
                                  node)
                     | None ->
                         announceDeath()
-                        failwith "Decryption failed!"
+
+                        raise <| CircuitDecryptionFailedException()
 
                 decryptMessage encryptedRelayCell.EncryptedData nodes
             | _ -> failwith "Unexpected state when receiving relay cell"

NOnion/Network/TorGuard.fs

@@ -332,14 +332,15 @@ type TorGuard private (client: TcpClient, sslStream: SslStream) =
                             try
                                 do! circuit.HandleIncomingCell cell
                             with
-                            | ex ->
+                            | :? CircuitDecryptionFailedException as ex ->
                                 sprintf
                                     "TorGuard: exception when trying to handle incoming cell type=%i, ex=%s"
                                     cell.Command
                                     (ex.ToString())
                                 |> TorLogger.Log
 
                                 self.KillChildCircuits()
+                            | ex -> return raise <| FSharpUtil.ReRaise ex
                         | None ->
                             self.KillChildCircuits()
                             failwithf "Unknown circuit, Id = %i" cid