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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)
}
// Cover returns true if a name is covered by the NSEC3 record
func (rr *NSEC3) Cover(name string) bool {
nameHash := HashName(name, rr.Hash, rr.Iterations, rr.Salt)
owner := strings.ToUpper(rr.Hdr.Name)
labelIndices := Split(owner)
if len(labelIndices) < 2 {
return false
}
ownerHash := owner[:labelIndices[1]-1]
ownerZone := owner[labelIndices[1]:]
if !IsSubDomain(ownerZone, strings.ToUpper(name)) { // name is outside owner zone
return false
}
nextHash := rr.NextDomain
if ownerHash == nextHash { // empty interval
return false
}
if ownerHash > nextHash { // end of zone
if nameHash > ownerHash { // covered since there is nothing after ownerHash
return true
}
return nameHash < nextHash // if nameHash is before beginning of zone it is covered
}
if nameHash < ownerHash { // nameHash is before ownerHash, not covered
return false
}
return nameHash < nextHash // if nameHash is before nextHash is it covered (between ownerHash and nextHash)
}
// Match returns true if a name matches the NSEC3 record
func (rr *NSEC3) Match(name string) bool {
nameHash := HashName(name, rr.Hash, rr.Iterations, rr.Salt)
owner := strings.ToUpper(rr.Hdr.Name)
labelIndices := Split(owner)
if len(labelIndices) < 2 {
return false
}
ownerHash := owner[:labelIndices[1]-1]
ownerZone := owner[labelIndices[1]:]
if !IsSubDomain(ownerZone, strings.ToUpper(name)) { // name is outside owner zone
return false
}
if ownerHash == nameHash {
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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