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VPN using SSH

Implementing a secure Unix to Unix Virtual Private Network Gary Stainburn Ringways Garages Ltd. VPN using SSH. Andrew’s Talk. Excellent talk covering theory and history Implemented pptp - most common use of VPN However, my way is better. Ssh is better, why?.

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VPN using SSH

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  1. Implementing a secure Unix to Unix Virtual Private Network Gary Stainburn Ringways Garages Ltd. VPN using SSH

  2. Andrew’s Talk • Excellent talk covering theory and history • Implemented pptp - most common use of VPN • However, my way is better.

  3. Ssh is better, why? • Always secure - no need to patch kernel • true Unix to Unix connection. • Better for Lan to Lan. • Modular • ssh (zlib, ssl, ssh) • port redirector • pppd

  4. Why VPN • Look at an APN.

  5. Why VPN • Look at an APN. • Existing Ringways APN (a.k.a. WAN)

  6. Proposed Internet Link • Ringways were looking for an internet link

  7. Suggested VPN • Suggested replacing existing lines with:

  8. Actually Went With

  9. What if we grow?

  10. What if we grow?

  11. Definitely VPN

  12. Points to Consider • APN • Cost of line vs Benefits received • Who meets costs? • VPN • No cost if link already available • Split cost if not already available

  13. Implications • Lower costs = more uses • more uses = more connections • more connections = more access points

  14. Security • Firewall - One point of access • Multiple access points • Weakness in remote end - Win95? • Other people administrating • Treat VPN users as Notebook Users

  15. Security - Server • When planning to set up a VPN server • Needs public access • Can be behind firewall - Ssh works over NAT • preferably no other access • Can be on firewall

  16. So, how’s it work? • Uses an existing unsecured network • runs a Ssh session over that connection • redirects a pppd session over it.

  17. Ssh - So, what do I need? • For RedHat 6 systems: • zlib-1.1.3-6.i386.rpm - already installed • openssl-0.9.5a.i386.rpm • openssh-2.1.1p2-1.i386.rpm • openssh-clients-2.1.1p2-1.i386.rpm • openssh-server-2.1.1p2-1.i386.rpm • Pppd.

  18. Ssh - So, what do I need? • For everything else: • zlib-1.1.3.tar.gz - ftp://ftp.cdrom.com/pub/infozip/zlib • openssl-0.9.5a.tar.gz - http://www.openssl.org • openssh-2.1.1p2.tar.gz - http://www.openssh.com • Pppd

  19. Ssh - So what do I do? • For RedHat 6 systems: • rpm -i openssl-0.9.5a.i386.rpm • rpm -i openssh-2.1.1p2-1.i386.rpm • rpm -i openssh-clients-2.1.1p2-1.i386.rpm • rpm -i openssh-server-2.1.1p2-1.i386.rpm

  20. Ssh - So what do I do? • For everything else: • untar zlib-1.1.3.tar.gz • ./configure • make • make test • make install

  21. Ssh - So what do I do? • For everything else: • untar openssl-0.9.5a.tar.gz • ./config • make • make test • make install

  22. Ssh - So what do I do? • For everything else: • untar openssh-2.1.1p2.tar.gz • ./configure • make • make install

  23. Ssh - So what do I do? • As root run: • ssh-keygen • This creates .ssh directory. • This contains the private and public keys. • Create authorized_keys from public key

  24. Ssh - So what do I do? • Copy the identity.pub from the client machine to the server machine • Client = makes call • Server = receives call • Append this file to /root/.ssh/authorized_keys • Make sure sshd is running on the server

  25. Ssh - How do I test it • On the client • ssh <servername> • If you have done everything correctly you should now have a Ssh session open and the command prompt of the server machine on-screen.

  26. So what’s next - Server • edit /etc/ppp/options to include: • ipcp-accept-local • ipcp-accept-remote • proxyarp • noauth

  27. So what’s next - Server • Create a vpn-users group and user • add group vpnusers to /etc/groups • vpnusers:*:504: • add user vpn-users to /etc/passwd • vpnuses:*:504:405:VPN User:/home/vpnusers:/usr/sbin/pppd • mkdir /home/vpn-users • chown vpnusers:vpnusers /home/vpnusers

  28. So what’s next - Server • Create the /home/vpnusers/.ssh directory • Create the file .ssh/authorized_keys • Add the public keys of everyone who needs access.

  29. So what’s next - Client • as root run: • mkdir /root/.ssh • ssh-keygen -f /root/.ssh/identity.vpn -P ”” • add the new file identity.vpn.pub to the authorized_keys on the server.

  30. So what’s next - client • Get http://www.shinythings.com/vpnd/vpnd.tar.gz • Unzip it into /usr/local/vpn • copy pty-redir to /usr/sbin

  31. So what’s next - client • as root run: • pty-redir ssh -t -e none -o ‘Batchmode yes’ -c blowfish -i /root/.ssh/identity.vpn -l vpnuser curly >/tmp/vpn-device • sleep 10 • /usr/sbin/pppd `cat /tmp/vpn-device`

  32. And Finally • On the client and the server • Edit /etc/ppp/ip-up to add routes across the VPN • Edit/etc/ppp/ip-down to remove them afterwards. • What’s left • Modify the vpnd script match your configuration to make admin easier.

  33. That’s it. • We’re done, so what have we done • We’ve got ssh working • We’ve configured a server to receive calls • We’ve configured a client to make a call • We’ve routed traffic across the VPN

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