IPsec with public key authentication on VyOS/EdgeOS

Setup

Generate an RSA keypair

ubnt@ubnt:~$ generate vpn rsa-key bits 4096 random /dev/urandom
Generating rsa-key to /config/ipsec.d/rsa-keys/localhost.key

Your new local RSA key has been generated
The public portion of the key is:

0sAQPNdF370ZEbN+kZUJQ10qnBlZujrg39ujfk20ILTjELksOIdJw/4jiU1MfpqFDKuB/XxERwJQp2POsFyV/n76jAgxIYBfFYfuaBcIH1rdNQtDhCnkmWzlueRXGEsz0Af79n8TKyQ9otzNhJ2cPE1CWCJbKqbIUN3piviLgGlItWNeya+Tl3Oj3ZfEVwr1QOvUAw32+m4L8T9jf1vqSlOTHpRpxxPWBrLEzstk0FOcZISji2JBpDOCU8Kpyyf74JM+LxsOIHwmS15b6iFZR3U9KZLqbbd0dSy/cM8P4XjrwM5UMyRDjrLqvuA/K/33BgtnxdQR3e9DJoYH3Qr8eRgSkR+jHyq06LvgHkHbMvrEjUnc3n8bg+YfR4oyJpIWsKjfIXmN1Q51KzxAPIAww+YSYUYtamSsQsspVAtMIQqR4e0r1In1qyoSn8VCPlksNMWpqYHbSjDo5HJYoSwxf2epzMtCvhenn0OuiH0xlgzziA+wBi6txksTMvJYcPJYnBVR2NIBjkWftOfmkY+rKMozViGjyd6kB7C8lqd8W7Ha5Ds2WxIY22DM3HcYH/zTp9z2xbuMOsbIgib/Y12Kh0wHyCz0lzFvs+d6CZwinyIXNKB/Vo4iiwT5luL5mGqf3pZx4zB+30GYSs/6MaELRF9BxD7tfqYCkOLXUtxyZ4Pdl2sw==

Exchange public keys with your peer

Display the public key. Send the key data portion to your peer.

 ubnt@ubnt:~$ show vpn ike rsa-keys
    
 Local public key (/config/ipsec.d/rsa-keys/localhost.key):
    
 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

Convert your peer's public key to the Base64 RFC 3110 format using the pubkey-converter script, if necessary.

Configuration

Configure the phase 1 IKE parameters

In this example, we'll use the following settings:

Key	Value
Encryption	AES-128
Hash	HMAC-SHA1
DH Group	5 (modp1536)
Lifetime	28800 seconds
Peer address	192.0.2.2
Local address	192.0.2.1

Add your peer's public key

 vyos@vyos:~$ configure
 [edit]
 vyos@vyos# set vpn rsa-keys rsa-key-name my-peer rsa-key 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

Configure an ISAKMP policy

 [edit]
 vyos@vyos# edit vpn ipsec ike-group FOO
 [edit vpn ipsec ike-group FOO]
 vyos@vyos# set lifetime 28800
 [edit vpn ipsec ike-group FOO]
 vyos@vyos# set proposal 1 encryption aes128
 [edit vpn ipsec ike-group FOO]
 vyos@vyos# set proposal 1 hash sha1
 [edit vpn ipsec ike-group FOO]
 vyos@vyos# set proposal 1 dh-group 5
 	[edit vpn ipsec ike-group FOO]
 	vyos@vyos# commit

Set your peer definition to use the public key

 [edit vpn ipsec ike-group FOO]
 vyos@vyos# up
 [edit vpn ipsec]
 vyos@vyos# edit site-to-site peer 192.0.2.2
 [edit vpn ipsec site-to-site peer 192.0.2.2]
 vyos@vyos# set authentication mode rsa
 [edit vpn ipsec site-to-site peer 192.0.2.2]
 vyos@vyos# set authentication rsa-key-name my-peer

All done! Configure the phase 2 parameters as you otherwise would.

Full GRE/IPsec example

interfaces {
    ethernet eth0 {
        address 192.0.2.1/30
        description WAN
        duplex auto
        speed auto
    }
    tunnel tun0 {
        address 10.1.2.0/31
        encapsulation gre
        local-ip 192.0.2.1
        mtu 1400
        multicast disable
        remote-ip 192.0.2.2
        ttl 255
    }
}
vpn {
    ipsec {
        esp-group BAR {
            compression disable
            lifetime 3600
            mode transport
            pfs dh-group5
            proposal 1 {
                encryption aes128
                hash sha1
            }
        }
        ike-group FOO {
            lifetime 28800
            proposal 1 {
                dh-group 5
                encryption aes128
                hash sha1
            }
        }
        ipsec-interfaces {
            interface eth0
        }
        site-to-site {
            peer 192.0.2.2 {
                authentication {
                    mode rsa
                    rsa-key-name my-peer
                }
                connection-type initiate
                default-esp-group BAR
                ike-group FOO
                local-ip 192.0.2.1
                tunnel 0 {
                    protocol gre
                }
            }
        }
    }
    rsa-keys {
        rsa-key-name my-peer {
            rsa-key 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
        }
    }
}

VyOSExample