1. SSH Operation and Techniques - © 2001-2006 William Stearns 1 SSH Operation and Techniques The Swiss Army Knife of encryption tools…

2. SSH Operation and Techniques - © 2001-2006 William Stearns 2 Overview SSH Introduction and Basic Use Copying files Port and X Windows forwarding SSH Keys and installation Ssh-agent Fanout and Fanterm

3. SSH Operation and Techniques - © 2001-2006 William Stearns 3 SSH Features Command line terminal connection tool Replacement for rsh, rcp, telnet, and others All traffic encrypted Both ends authenticate themselves to the other end Ability to carry and encrypt non-terminal traffic

4. SSH Operation and Techniques - © 2001-2006 William Stearns 4 Brief History SSH.com's SSH1, originally completely free with source code, then license changed with version 1.2.13 SSH.com's SSH2, originally only commercial, but now free for some uses. OpenSSH team took the last free SSH1 release, refixed bugs, added features, and added support for the SSH2 protocol.

5. SSH Operation and Techniques - © 2001-2006 William Stearns 5 Installation OpenSSH is included with a number of Linux distributions, and available for a large number of Unices On RPM-based Linuxes: rpm -Uvh openssh*.rpm

6. SSH Operation and Techniques - © 2001-2006 William Stearns 6 Basic use ssh SshServerName ssh -l UserName SshServerName ssh SshServerName CommandToRun ssh -v SshServerName Server Host Key checks Uses same login password And if we need to encrypt other traffic?

7. SSH Operation and Techniques - © 2001-2006 William Stearns 7 Securely copying files scp scp -p localfile remotemachine:/remotepath/file Prompts for authentication if needed All traffic encrypted Replaces ftp, rcp, file sharing

8. SSH Operation and Techniques - © 2001-2006 William Stearns 8 File synchronization - Rsync Rsync copies a tree of files from a master out to a copy on another machine. Can use ssh as its transport. rsync -azv -e ssh /home/wstearns/webtree/ mirror.stearns.org/home/web/

9. SSH Operation and Techniques - © 2001-2006 William Stearns 9 Port Forwarding - real server on remote machine I want to listen on port 5110 on this machine; all packets arriving here get sent to mailserver, port 110: ssh -L 5110:mailserver:110 mailserver

10. SSH Operation and Techniques - © 2001-2006 William Stearns 10 Port Forwarding - real server on this machine All web traffic to my firewall should be redirected to the web server running on port 8000 on my machine instead: ssh -R 80:MyMachine:8000 firewall

11. SSH Operation and Techniques - © 2001-2006 William Stearns 11 X Windows forwarding No setup - already done! Run the X Windows application in the terminal window: xclock & The screen display shows up on your computer, and any keystrokes and mouse movements are sent back, all encrypted.

12. SSH Operation and Techniques - © 2001-2006 William Stearns 12 Packet forwarding – VPNs Tunnel packets over the SSH connection Connects to a virtual network device on both ends Openssh 4.3 and higher

13. SSH Operation and Techniques - © 2001-2006 William Stearns 13 SSH key background Old way: password stored on server, user supplied password compared to stored version New way: private key kept on client, public key stored on server.

14. SSH Operation and Techniques - © 2001-2006 William Stearns 14 SSH key creation General command: ssh-keygen -b 1024 -c 'Comment' -f ~/.ssh/identity_file Different forms for each of the SSH flavors Assign a hard-to-guess passphrase to the private key during creation. Key can be used for multiple servers

15. SSH Operation and Techniques - © 2001-2006 William Stearns 15 SSH key installation 3 versions of ssh: interoperability is good, but poorly documented ssh-keyinstall utility automates the creation and installation 'ssh-keyinstall -s SshServerName' creates keys, if needed, and installs them on the remote server Need password during key install only

16. SSH Operation and Techniques - © 2001-2006 William Stearns 16 Using SSH keys ssh SshServerName Ssh -l UserName SshServerName ssh SshServerName CommandToRun Ssh -v SshServerName

17. SSH Operation and Techniques - © 2001-2006 William Stearns 17 ssh-agent Remembers your private key(s) Other applications can ask ssh-agent to authenticate you automatically. Unattended remote sessions. Should already be running in the background ssh-add [KeyName]

18. SSH Operation and Techniques - © 2001-2006 William Stearns 18 Fanout Runs command on multiple machines by opening separate ssh session to each fanout 'machine1 machine2 user@machine3' 'command params' Gives organized output from each machine

19. SSH Operation and Techniques - © 2001-2006 William Stearns 19 Fanterm – live control of multiple machines Fanterm provides interactive control of multiple remote systems. Initial window receives keystrokes. Keystrokes sent to each remote system. Output from each system shows up in a seperate terminal.

20. SSH Operation and Techniques - © 2001-2006 William Stearns 20

21. SSH Operation and Techniques - © 2001-2006 William Stearns 21 Fanqueue – the next generation Queue commands to be run on a group of machines Handles case where a machine is unavailable Allows new machines to be added later

22. SSH Operation and Techniques - © 2001-2006 William Stearns 22 Rsync-backup Rsync-backup automates the process of backing up machines with rsync and ssh. Features: Only changed data shipped All permissions preserved All communication encrypted Unlimited snapshots Use <= 2X-4X combined client capacity

23. SSH Operation and Techniques - © 2001-2006 William Stearns 23 Rsync-backup client install Install ssh, rsync, and rsync-backup-client rpms (see http://www.stearns.org ) Install ssh-keyinstall on client to create a backup key with ssh-keyinstall -s backupserver -u root -c /usr/sbin/rsync-backup-server

24. SSH Operation and Techniques - © 2001-2006 William Stearns 24 Rsync-backup server install Install ssh, freedups, rsync-static, and rsync- backup-server rpms Turn off password authentication in /etc/ssh/sshd_config

25. SSH Operation and Techniques - © 2001-2006 William Stearns 25 Rsync-backup examples Examples of backup commands: rsync-backup-client / root@backupserver:/ rsync-backup-client /usr /home/gbk root@backupserver:/

26. SSH Operation and Techniques - © 2001-2006 William Stearns 26 Links and references http://www.vandyke.com http://www.ssh.com http://www.openssh.org SSH, The Secure Shell, The Definitive Guide ssh-keyinstall, fanout, rsync-backup, freedups and other apps at http://www.stearns.org

27. SSH Operation and Techniques - © 2001-2006 William Stearns 27 More links Docs at http://www.stearns.org/doc/ http://www.employees.org/~satch/ssh/faq/ssh- faq.html http://htp://rsync.samba.org William Stearns wstearns@pobox.com