Network Security Hacks

Set Up IPsec in OpenBSD

Use IPsec the OpenBSD way.

Setting up IPsec in OpenBSD is fairly easy since it’s compiled into the kernel that ships with each release and is enabled by default. All that is left to do is to create the appropriate /etc/isakmpd/isakmpd.conf and /etc/isakmpd/isakmpd.policy files and start isakmpd (the IPsec key-management daemon). This may sound daunting, but OpenBSD’s outstanding documentation and example configuration files make it easier.

First of all, you’ll need to put something similar to this in your /etc/isakmpd/isakmpd.policy:

KeyNote-Version: 2
Authorizer: "POLICY"
Licensees: "passphrase:mypassword"
Conditions: app_domain == "IPsec policy" &&
            esp_present == "yes" &&
            esp_enc_alg == "aes" &&
            esp_auth_alg == "hmac-sha" -> "true";

This sets a password to use for the IPsec connection.

Now you’ll need to edit your /etc/isakmpd/isakmpd.conf to contain the following:

[General] Listen-on= 192.168.1.1 Shared-SADB= Defined [Phase 1] Default= ISAKMP-peer-remote #Default= ISAKMP-peer-remote-aggressive [Phase 2] Passive-Connections=IPsec-local-remote [ISAKMP-peer-remote] Phase= 1 Transport= udp Local-address= 192.168.1.1 Configuration= Default-main-mode Authentication= mypassword [ISAKMP-peer-remote-aggressive] Phase= 1 Transport= udp Local-address= 192.168.1.1 Configuration= Default-aggressive-mode Authentication= mypassword [IPsec-local-remote] Phase= 2 ISAKMP-peer= ISAKMP-peer-remote Configuration= Default-quick-mode Local-ID= Net-local Remote-ID= Net-remote [Net-remote] ...