HOWTO: Using NSS with libreswan

The libreswan IKE daemon uses the Mozilla Network Security Services ("NSS") crypto library for all cryptographic functions during the IKE negotiation.

The NSS crypto library is user space library. It is only used with the libreswan userspace IKE daemon pluto for cryptographic operations. NSS does not perform IPsec crypto operations inside the kernel (KLIPS nor NETKEY)

The NSS library exports a PKCS#11 API for the application to communicate to a cryptographic device. The cryptographic device is usually the "soft token" but can also be a Hardware Security Module (HSM).

The advantage of using NSS is that pluto does need to know in detail how the cryptographic device works. Pluto does not access any private keys or data itself. Instead, it uses the PK11 wrapper API of NSS irrespective of the cryptographic device used. Pluto hands over work using the PK11 interface to NSS and never has direct access to the private key material itself. Both IKEv1 and IKEv2 operations are performed using NSS. Private RSA keys (raw RSA as well as X.509 based private RSA keys) are stored inside NSS. RSA keys are still referenced in /etc/ipsec.secrets. X.509 keys and certificates are referenced using their "nickname" instead of their filename in /etc/ipsec.conf.

While PreShared Key (PSK) calculations are done using NSS, the actual preshared key ("secret") is still stored in /etc/ipsec.secrets.

NSS as shipped by Red Hat is a FIPS certified library. Libreswan is currently being FIPS certified for RHEL7.