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package dns
import (
"crypto/sha1"
"hash"
"strings"
)
type saltWireFmt struct {
Salt string `dns:"size-hex"`
}
// HashName hashes a string (label) according to RFC 5155. It returns the hashed string in uppercase.
func HashName(label string, ha uint8, iter uint16, salt string) string {
saltwire := new(saltWireFmt)
saltwire.Salt = salt
wire := make([]byte, DefaultMsgSize)
n, err := packSaltWire(saltwire, wire)
if err != nil {
return ""
}
wire = wire[:n]
name := make([]byte, 255)
off, err := PackDomainName(strings.ToLower(label), name, 0, nil, false)
if err != nil {
return ""
}
name = name[:off]
var s hash.Hash
switch ha {
case SHA1:
s = sha1.New()
default:
return ""
}
// k = 0
s.Write(name)
s.Write(wire)
nsec3 := s.Sum(nil)
// k > 0
for k := uint16(0); k < iter; k++ {
s.Reset()
s.Write(nsec3)
s.Write(wire)
nsec3 = s.Sum(nsec3[:0])
}
return toBase32(nsec3)
}
// Denialer is an interface that should be implemented by types that are used to denial
// answers in DNSSEC.
type Denialer interface {
// Cover will check if the (unhashed) name is being covered by this NSEC or NSEC3.
Cover(name string) bool
// Match will check if the ownername matches the (unhashed) name for this NSEC3 or NSEC3.
Match(name string) bool
}
// Cover implements the Denialer interface.
func (rr *NSEC) Cover(name string) bool {
return true
}
// Match implements the Denialer interface.
func (rr *NSEC) Match(name string) bool {
return true
}
// Cover implements the Denialer interface.
func (rr *NSEC3) Cover(name string) bool {
// FIXME(miek): check if the zones match
// FIXME(miek): check if we're not dealing with parent nsec3
hname := HashName(name, rr.Hash, rr.Iterations, rr.Salt)
labels := Split(rr.Hdr.Name)
if len(labels) < 2 {
return false
}
hash := strings.ToUpper(rr.Hdr.Name[labels[0] : labels[1]-1]) // -1 to remove the dot
if hash == rr.NextDomain {
return false // empty interval
}
if hash > rr.NextDomain { // last name, points to apex
// hname > hash
// hname > rr.NextDomain
// TODO(miek)
}
if hname <= hash {
return false
}
if hname >= rr.NextDomain {
return false
}
return true
}
// Match implements the Denialer interface.
func (rr *NSEC3) Match(name string) bool {
// FIXME(miek): Check if we are in the same zone
hname := HashName(name, rr.Hash, rr.Iterations, rr.Salt)
labels := Split(rr.Hdr.Name)
if len(labels) < 2 {
return false
}
hash := strings.ToUpper(rr.Hdr.Name[labels[0] : labels[1]-1]) // -1 to remove the .
if hash == hname {
return true
}
return false
}
func packSaltWire(sw *saltWireFmt, msg []byte) (int, error) {
off, err := packStringHex(sw.Salt, msg, 0)
if err != nil {
return off, err
}
return off, nil
}
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