In message <200002280301.UAA09309at_private>, Theo de Raadt writes: > > > All children of the SSH connection are able to tunnel X11 sessions > > > through the X tunnel to the client X11 session. This is > > > accomplished by running xauth upon logging in. > > > > I'm really suprised this is still the default. I've heard mention of > > this at least 4 years ago, and have seen trojaned SSH servers around > > _since then_ that do logging of client X11 keystrokes - probably the > > best place to accomplish this. The problem seems to be that the > > authors have not figured out that this isn't a good default, perhaps > > for convenience's sake. This suprises me, since people DO know about > > this. I think the argument is really convenience vs. security (well, > > thats always the argument isn't it?). > > > > alias ssh="ssh -x" > > Earlier, bugtraq was told that all ssh versions including openssh > automatically tunnel X. > > This is not correct. openssh has that turned off by default. > Theo, I held the same opinion as you until it was pointed out to me offline that it's not the server that needs the default specification, as it already has, and because an untrusted server could have its specification changed. Instead the ssh_config (client) needs to have its default changed to deny X tunnelling as well in case an untrusted server, e.g. a server one does not trust, has its specification X tunnelling changed to allow it. To disable X forwarding, ssh_config also needs, Host * ForwardX11 no Ultimately turning on X forwarding would require changing of sshd_config, to enable the server X forwarding, and the users ~/.ssh/config file to enable the client's accepting of forwarded X packets. The second half of this would put the onus on the user for their own security, as the user would have to specifically enable X forwarding, even though the server already has it enabled. Regards, Phone: (250)387-8437 Cy Schubert Fax: (250)387-5766 Team Leader, Sun/DEC Team Internet: Cy.Schubertat_private UNIX Group, ITSD, ISTA Province of BC "COBOL IS A WASTE OF CARDS."
This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 15:38:03 PDT