CRL Support

People have been requesting the ability for CFSSL to be able to create a CRL file given a set of IDs (https://github.com/cloudflare/cfssl/issues/43).

This feature would be analogous to the OCSP signer, taking as input the parameters to fill the "to-be-signed" certificate revocation list and outputing a CRL signed by the signer's private key.

Here are the structures from https://golang.org/pkg/crypto/x509/pkix:
type RevokedCertificate struct {
        SerialNumber   *big.Int
        RevocationTime time.Time
        Extensions     []Extension `asn1:"optional"`
}

type TBSCertificateList struct {
        Raw                 asn1.RawContent
        Version             int `asn1:"optional,default:1"`
        Signature           AlgorithmIdentifier
        Issuer              RDNSequence
        ThisUpdate          time.Time
        NextUpdate          time.Time            `asn1:"optional"`
        RevokedCertificates []RevokedCertificate `asn1:"optional"`
        Extensions          []Extension          `asn1:"tag:0,optional,explicit"`
}

This feature should have support for:

• CLI and API
• Both PKCS11 and file-backed keys