/usr/share/strongswan/templates/config/plugins/ is in libstrongswan 5.1.2-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/strongswan/templates/config/plugins/addrblock.conf
/usr/share/strongswan/templates/config/plugins/aes.conf
/usr/share/strongswan/templates/config/plugins/attr.conf
/usr/share/strongswan/templates/config/plugins/ccm.conf
/usr/share/strongswan/templates/config/plugins/cmac.conf
/usr/share/strongswan/templates/config/plugins/constraints.conf
/usr/share/strongswan/templates/config/plugins/ctr.conf
/usr/share/strongswan/templates/config/plugins/eap-identity.conf
/usr/share/strongswan/templates/config/plugins/gcm.conf
/usr/share/strongswan/templates/config/plugins/hmac.conf
/usr/share/strongswan/templates/config/plugins/kernel-netlink.conf
/usr/share/strongswan/templates/config/plugins/md4.conf
/usr/share/strongswan/templates/config/plugins/md5.conf
/usr/share/strongswan/templates/config/plugins/nonce.conf
/usr/share/strongswan/templates/config/plugins/pem.conf
/usr/share/strongswan/templates/config/plugins/pkcs1.conf
/usr/share/strongswan/templates/config/plugins/pkcs12.conf
/usr/share/strongswan/templates/config/plugins/pkcs7.conf
/usr/share/strongswan/templates/config/plugins/pkcs8.conf
/usr/share/strongswan/templates/config/plugins/random.conf
/usr/share/strongswan/templates/config/plugins/rc2.conf
/usr/share/strongswan/templates/config/plugins/rdrand.conf
/usr/share/strongswan/templates/config/plugins/resolve.conf
/usr/share/strongswan/templates/config/plugins/revocation.conf
/usr/share/strongswan/templates/config/plugins/sha1.conf
/usr/share/strongswan/templates/config/plugins/sha2.conf
/usr/share/strongswan/templates/config/plugins/test-vectors.conf
/usr/share/strongswan/templates/config/plugins/x509.conf
/usr/share/strongswan/templates/config/plugins/xcbc.conf