// FillTemplate is a utility function that tries to load as much of
// the certificate template as possible from the profiles and current
// template. It fills in the key uses, expiration, revocation URLs,
// serial number, and SKI.
func FillTemplate(template *x509.Certificate, defaultProfile, profile *config.SigningProfile, serialSeq string) error {
ski, err := ComputeSKI(template)
var (
eku []x509.ExtKeyUsage
ku x509.KeyUsage
backdate time.Duration
expiry time.Duration
notBefore time.Time
notAfter time.Time
crlURL, ocspURL string
)
// The third value returned from Usages is a list of unknown key usages.
// This should be used when validating the profile at load, and isn't used
// here.
ku, eku, _ = profile.Usages()
if profile.IssuerURL == nil {
profile.IssuerURL = defaultProfile.IssuerURL
}
if ku == 0 && len(eku) == 0 {
return cferr.New(cferr.PolicyError, cferr.NoKeyUsages)
}
if expiry = profile.Expiry; expiry == 0 {
expiry = defaultProfile.Expiry
}
if crlURL = profile.CRL; crlURL == "" {
crlURL = defaultProfile.CRL
}
if ocspURL = profile.OCSP; ocspURL == "" {
ocspURL = defaultProfile.OCSP
}
if backdate = profile.Backdate; backdate == 0 {
backdate = -5 * time.Minute
} else {
backdate = -1 * profile.Backdate
}
if !profile.NotBefore.IsZero() {
notBefore = profile.NotBefore.UTC()
} else {
notBefore = time.Now().Round(time.Minute).Add(backdate).UTC()
}
if !profile.NotAfter.IsZero() {
notAfter = profile.NotAfter.UTC()
} else {
notAfter = notBefore.Add(expiry).UTC()
}
serialNumber, err := rand.Int(rand.Reader, new(big.Int).SetInt64(math.MaxInt64))
if err != nil {
return cferr.Wrap(cferr.CertificateError, cferr.Unknown, err)
}
if serialSeq != "" {
randomPart := fmt.Sprintf("%016X", serialNumber) // 016 ensures we're left-0-padded
_, ok := serialNumber.SetString(serialSeq+randomPart, 16)
if !ok {
return cferr.Wrap(cferr.CertificateError, cferr.SerialSeqParseError, err)
}
}
template.SerialNumber = serialNumber
template.NotBefore = notBefore
template.NotAfter = notAfter
template.KeyUsage = ku
template.ExtKeyUsage = eku
template.BasicConstraintsValid = true
template.IsCA = profile.CA
template.SubjectKeyId = ski
if ocspURL != "" {
template.OCSPServer = []string{ocspURL}
}
if crlURL != "" {
template.CRLDistributionPoints = []string{crlURL}
}
if len(profile.IssuerURL) != 0 {
template.IssuingCertificateURL = profile.IssuerURL
}
if len(profile.Policies) != 0 {
template.PolicyIdentifiers = profile.Policies
}
if profile.OCSPNoCheck {
ocspNoCheckExtension := pkix.Extension{
Id: asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1, 5},
Critical: false,
Value: []byte{0x05, 0x00},
}
template.ExtraExtensions = append(template.ExtraExtensions, ocspNoCheckExtension)
}
return nil
}
