Dropbear channel request race condition?

[Laurent Bercot]

> I'm not sure whether it's possible to use EOF like that for a
> session with a PTY terminal.

  It's not, and it's a well-known problem with read/write file
descriptors - they cannot transfer one-way EOFs. shutdown()
was actually added to the BSD socket interface to address
this problem, but it's an ad-hoc and half-working solution,
and it doesn't work on anything else than sockets.

  Terminals are complex here because they weren't designed for
separate input and output; the terminal model is a single point
of management for communication, whether inbound or outbound,
and sending half-duplex EOFs isn't supported AFAIK.

  Dropbear could still catch the write-EOF from the client and
not close the pty until the read-EOF also arrives. Or only
close it after a configurable timeout; closing as soon as the
write-EOF is received is definitely a suboptimal behaviour.

-- 
  Laurent