87 lines
2.1 KiB
Go
87 lines
2.1 KiB
Go
package dns
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import (
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"crypto/sha256"
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"crypto/sha512"
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"crypto/x509"
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"encoding/hex"
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"errors"
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"io"
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"net"
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"strconv"
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)
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// CertificateToDANE converts a certificate to a hex string as used in the TLSA record.
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func CertificateToDANE(selector, matchingType uint8, cert *x509.Certificate) (string, error) {
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switch matchingType {
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case 0:
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switch selector {
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case 0:
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return hex.EncodeToString(cert.Raw), nil
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case 1:
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return hex.EncodeToString(cert.RawSubjectPublicKeyInfo), nil
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}
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case 1:
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h := sha256.New()
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switch selector {
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case 0:
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io.WriteString(h, string(cert.Raw))
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return hex.EncodeToString(h.Sum(nil)), nil
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case 1:
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io.WriteString(h, string(cert.RawSubjectPublicKeyInfo))
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return hex.EncodeToString(h.Sum(nil)), nil
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}
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case 2:
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h := sha512.New()
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switch selector {
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case 0:
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io.WriteString(h, string(cert.Raw))
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return hex.EncodeToString(h.Sum(nil)), nil
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case 1:
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io.WriteString(h, string(cert.RawSubjectPublicKeyInfo))
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return hex.EncodeToString(h.Sum(nil)), nil
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}
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}
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return "", errors.New("dns: bad TLSA MatchingType or TLSA Selector")
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}
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// Sign creates a TLSA record from an SSL certificate.
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func (r *TLSA) Sign(usage, selector, matchingType int, cert *x509.Certificate) (err error) {
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r.Hdr.Rrtype = TypeTLSA
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r.Usage = uint8(usage)
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r.Selector = uint8(selector)
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r.MatchingType = uint8(matchingType)
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r.Certificate, err = CertificateToDANE(r.Selector, r.MatchingType, cert)
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if err != nil {
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return err
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}
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return nil
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}
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// Verify verifies a TLSA record against an SSL certificate. If it is OK
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// a nil error is returned.
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func (r *TLSA) Verify(cert *x509.Certificate) error {
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c, err := CertificateToDANE(r.Selector, r.MatchingType, cert)
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if err != nil {
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return err // Not also ErrSig?
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}
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if r.Certificate == c {
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return nil
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}
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return ErrSig // ErrSig, really?
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}
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// TLSAName returns the ownername of a TLSA resource record as per the
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// rules specified in RFC 6698, Section 3.
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func TLSAName(name, service, network string) (string, error) {
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if !IsFqdn(name) {
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return "", ErrFqdn
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}
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p, err := net.LookupPort(network, service)
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if err != nil {
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return "", err
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}
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return "_" + strconv.Itoa(p) + "._" + network + "." + name, nil
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}
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