FYI, in follow up to my previous email:
-----Forwarded Message----- > Apparently this is "known" behaviour: the openssh faq lists it as such > at http://www.openssh.org/faq.html#3.10. > > Damian, I recommend using the workaround mentioned in the faq. > > On Thu, Jul 25, 2002 at 03:13:42PM +1000, Garth Mollett wrote: > > fyi: > > > > After causing several bruises to my head (and gaining a much better > > understanding of the ssh/sshd internals), I've finnally figured whats going > > on, the "bug" isn't really in ssh/sshd as such but more in the way linux and > > solaris (bash?, although it happens with tcsh and pdksh, need to test futher, > > but I couldn't reproduce it on openbsd box (that only had bourne,korn and csh)) > > handle things: > > > > when the shell forks() a background proccess, it inherits the file > > descriptors from it's parrent attached to (the tty/pty) stdin/out/err > > and they are never closed, so if the parent (the shell) exits, the backgrounded > > child still has the tty/pty open, so the sshd proccess won't get an eof from > > the fd and select() won't get woken up as the other end of the pipe is still > > open (in the child). > > > > Demo: > > > > $ ssh nestor > > [nestor:~]$ sleep 7249823 & > > [1] 9838 > > [nestor:~]$ exit > > logout > > > > <connection "hangs" untill sleep exits> > > > > -- > > > > $ ssh nestor > > [nestor:~]$ cat test2.c > > #include <sys/types.h> > > #include <unistd.h> > > > > void > > main() > > { > > close(0); > > close(1); > > close(2); > > close(3); > > > > for (;;) > > sleep(22344); > > } > > > > [nestor:~]$ ./test2 & > > [1] 9852 > > [nestor:~]$ exit > > logout > > Connection to nestor closed. > > > > <connection closes straight away> > > > > Not sure if this is really a bug or a feature (as you can just explicitly > > kill the connection with the client), I'll reaserch it a little futher > > before I propose any possable solutions, at first I though if the child > > exits the connection should be dropped, but ssh isn't just used for running > > interactive shells and this could lead to unexpected results. > > > > I also though that this might be a way to snoop on other users, ie. > > you login start a background proccess and kill the connection, and the > > background process can still still read/write to the tty, however linux > > at least won't give the tty to another user untill nothing has any connections > > to it anymore. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
