CreateCertificate creates a new certificate based on a template. The following members of template are used: SerialNumber, Subject, NotBefore, NotAfter, KeyUsage, ExtKeyUsage, UnknownExtKeyUsage, BasicConstraintsValid, IsCA, MaxPathLen, SubjectKeyId, DNSNames, PermittedDNSDomainsCritical, PermittedDNSDomains, SignatureAlgorithm.

The certificate is signed by parent. If parent is equal to template then the certificate is self-signed. The parameter pub is the public key of the signee and priv is the private key of the signer.

The returned slice is the certificate in DER encoding.

All keys types that are implemented via crypto.Signer are supported (This includes *rsa.PublicKey and *ecdsa.PublicKey.)