REDHAT-BUG-2501764: Medium severity libreswan Libreswan vulnerability

Libreswan contains a reachable assertion in the X.509 certificate processing path when operating in FIPS mode. After calling CERTExtractPublicKey(), the returned public key is asserted to be non-NULL, although the function may legitimately return NULL if public key extraction fails (for example, when processing a certificate with an RSA exponent of zero). An unauthenticated remote attacker can send a specially crafted CERT payload during an IKEv1 or IKEv2 exchange to trigger the assertion and terminate the daemon, resulting in a denial of service. The issue is only reachable when Libreswan is running in FIPS mode and certificate-based authentication is in use with at least one CA certificate loaded in the Libreswan NSS database; deployments using only Pre-Shared Key (PSK) authentication without loaded CA certificates are not affected.