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Article:
  Secure Mail Reading on Mac OS X
Subject:   Tunnel Drop
Date:   2002-11-01 20:18:59
From:   cochella
I have using a very similar setup to that in this article such that there are no fundamental differences.


I establish an SSH local tunnel (port forwarding) to a POP server (port 110).


I can watch the clear text in a tcpflow window for port 110 and watch the concurrent session in another tcpflow window for port 22.


The strangeness occurs when over time the tunnel or the connection is dropped for some reason--network interruption, whatever.


Thus, the tunnel is now gone. But, I still get mail. I simulated this by dropping the tunnel myself and watching the tcpflow windows. Lo and behold there was nothing going on in the port 22 window meaning that my whole session was in the clear. Thus, when the tunnel drops and I am unaware of it the session reverts to being in the clear.


Is there any way around this? Would KeepAlive on the client work?


Is there a way to shutdown this unencrypted access when the tunnel drops?


Thanks,
chris