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package dnssec
import (
"github.com/coredns/coredns/plugin/pkg/response"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
)
// nsec returns an NSEC useful for NXDOMAIN responses.
// See https://tools.ietf.org/html/draft-valsorda-dnsop-black-lies-00
// For example, a request for the non-existing name a.example.com would
// cause the following NSEC record to be generated:
// a.example.com. 3600 IN NSEC \000.a.example.com. ( RRSIG NSEC ... )
// This inturn makes every NXDOMAIN answer a NODATA one, don't forget to flip
// the header rcode to NOERROR.
func (d Dnssec) nsec(state request.Request, mt response.Type, ttl, incep, expir uint32, server string) ([]dns.RR, error) {
nsec := &dns.NSEC{}
nsec.Hdr = dns.RR_Header{Name: state.QName(), Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeNSEC}
nsec.NextDomain = "\\000." + state.QName()
if state.Name() == state.Zone {
nsec.TypeBitMap = filter18(state.QType(), apexBitmap, mt)
} else {
nsec.TypeBitMap = filter14(state.QType(), zoneBitmap, mt)
}
sigs, err := d.sign([]dns.RR{nsec}, state.Zone, ttl, incep, expir, server)
if err != nil {
return nil, err
}
return append(sigs, nsec), nil
}
// The NSEC bit maps we return.
var (
zoneBitmap = [...]uint16{dns.TypeA, dns.TypeHINFO, dns.TypeTXT, dns.TypeAAAA, dns.TypeLOC, dns.TypeSRV, dns.TypeCERT, dns.TypeSSHFP, dns.TypeRRSIG, dns.TypeNSEC, dns.TypeTLSA, dns.TypeHIP, dns.TypeOPENPGPKEY, dns.TypeSPF}
apexBitmap = [...]uint16{dns.TypeA, dns.TypeNS, dns.TypeSOA, dns.TypeHINFO, dns.TypeMX, dns.TypeTXT, dns.TypeAAAA, dns.TypeLOC, dns.TypeSRV, dns.TypeCERT, dns.TypeSSHFP, dns.TypeRRSIG, dns.TypeNSEC, dns.TypeDNSKEY, dns.TypeTLSA, dns.TypeHIP, dns.TypeOPENPGPKEY, dns.TypeSPF}
)
// filter14 filters out t from bitmap (if it exists). If mt is not an NODATA response, just return the entire bitmap.
func filter14(t uint16, bitmap [14]uint16, mt response.Type) []uint16 {
if mt != response.NoData && mt != response.NameError {
return zoneBitmap[:]
}
for i := range bitmap {
if bitmap[i] == t {
return append(bitmap[:i], bitmap[i+1:]...)
}
}
return zoneBitmap[:] // make a slice
}
func filter18(t uint16, bitmap [18]uint16, mt response.Type) []uint16 {
if mt != response.NoData && mt != response.NameError {
return apexBitmap[:]
}
for i := range bitmap {
if bitmap[i] == t {
return append(bitmap[:i], bitmap[i+1:]...)
}
}
return apexBitmap[:] // make a slice
}
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