SSH

Pointers

• http://www.openssh.com/manual.html - man pages
• fsh - reuse ssh tunnels for better performance
• FileSystems - see SSH section for info on mounting filesystems using only ssh
• SambA - see 'tunneling over ssh'

• UnixGeekTools - other great tools for unix geeks

ssh forwarding

• example: ssh -v -2 -L2003:remotehost:22 jet
• SshX11Forwarding - forwarding x11 over ssh
• SSHKeychain - OSX application
• quiet warnings with keys when forwarding ssh thru ssh

    ssh -o NoHostAuthenticationForLocalhost=yes -p 8889 -q localhost

proxy

• http://www.nocrew.org/software/httptunnel.html

Debugging

• permissions on home directory
• permissions on .ssh directory
• permissions on private key
• Permsssions on authorized_keys2

running server in debug mode

• info for debugging an issue with the sshd daemon where you don't have root or don't have local access and don't want to risk shutting down your running sshd daemon
• simply start an sshd daemon on an alternate port in debug mode:
  • generate a key to use as a host key (ssh-keygen -t dsa -f test_host)
  • run sshd in debug mode on a separate port (/usr/local/sbin/sshd -p 5138 -Dd -h test_host)
  • connect to the new instance (ssh -p 5138 user@server)

Forced commands

• provide access to a key to run a single command
• add to authorized_keys2

  command="ssh -l skipper S" ...key..

Weird stuff

• ssh encryption protocol can be set to 'none'.

X11 forwarding insecurity Overview

If xauth is replaced on the server by a malicious program that does both of the following:

• runs xauth, adding in the "correct" information allowing the children of the session to tunnel X11 programs through the SSH session
• runs xauth, adding in the "malicious" information, allowing a malicious source to tunnel X11 programs through the SSH session.

With the added data in .Xauthority, a malicious source can fully control the client X session. The malicious source can then do most anything to the X session, from logging keystrokes of the X session, to taking screen captures, to typing in commands to open terminals.

the client is the one accepting risk by forwarding X11, not the server.