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package dns
import (
"crypto/sha256"
"crypto/x509"
"encoding/hex"
)
// Sign creates a SMIMEA record from an SSL certificate.
func (r *SMIMEA) Sign(usage, selector, matchingType int, cert *x509.Certificate) (err error) {
r.Hdr.Rrtype = TypeSMIMEA
r.Usage = uint8(usage)
r.Selector = uint8(selector)
r.MatchingType = uint8(matchingType)
r.Certificate, err = CertificateToDANE(r.Selector, r.MatchingType, cert)
if err != nil {
return err
}
return nil
}
// Verify verifies a SMIMEA record against an SSL certificate. If it is OK
// a nil error is returned.
func (r *SMIMEA) Verify(cert *x509.Certificate) error {
c, err := CertificateToDANE(r.Selector, r.MatchingType, cert)
if err != nil {
return err // Not also ErrSig?
}
if r.Certificate == c {
return nil
}
return ErrSig // ErrSig, really?
}
// SMIMEAName returns the ownername of a SMIMEA resource record as per the
// format specified in RFC 'draft-ietf-dane-smime-12' Section 2 and 3
func SMIMEAName(email, domain string) (string, error) {
hasher := sha256.New()
hasher.Write([]byte(email))
// RFC Section 3: "The local-part is hashed using the SHA2-256
// algorithm with the hash truncated to 28 octets and
// represented in its hexadecimal representation to become the
// left-most label in the prepared domain name"
return hex.EncodeToString(hasher.Sum(nil)[:28]) + "." + "_smimecert." + domain, nil
}
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