107 lines
2.5 KiB
Go
107 lines
2.5 KiB
Go
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package dns
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import (
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"crypto/sha1"
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"hash"
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"strings"
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)
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type saltWireFmt struct {
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Salt string `dns:"size-hex"`
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}
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// HashName hashes a string (label) according to RFC 5155. It returns the hashed string in uppercase.
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func HashName(label string, ha uint8, iter uint16, salt string) string {
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saltwire := new(saltWireFmt)
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saltwire.Salt = salt
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wire := make([]byte, DefaultMsgSize)
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n, err := packSaltWire(saltwire, wire)
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if err != nil {
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return ""
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}
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wire = wire[:n]
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name := make([]byte, 255)
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off, err := PackDomainName(strings.ToLower(label), name, 0, nil, false)
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if err != nil {
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return ""
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}
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name = name[:off]
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var s hash.Hash
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switch ha {
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case SHA1:
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s = sha1.New()
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default:
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return ""
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}
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// k = 0
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s.Write(name)
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s.Write(wire)
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nsec3 := s.Sum(nil)
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// k > 0
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for k := uint16(0); k < iter; k++ {
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s.Reset()
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s.Write(nsec3)
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s.Write(wire)
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nsec3 = s.Sum(nsec3[:0])
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}
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return toBase32(nsec3)
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}
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// Cover returns true if a name is covered by the NSEC3 record
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func (rr *NSEC3) Cover(name string) bool {
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nameHash := HashName(name, rr.Hash, rr.Iterations, rr.Salt)
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owner := strings.ToUpper(rr.Hdr.Name)
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labelIndices := Split(owner)
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if len(labelIndices) < 2 {
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return false
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}
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ownerHash := owner[:labelIndices[1]-1]
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ownerZone := owner[labelIndices[1]:]
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if !IsSubDomain(ownerZone, strings.ToUpper(name)) { // name is outside owner zone
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return false
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}
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nextHash := rr.NextDomain
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if ownerHash == nextHash { // empty interval
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return false
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}
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if ownerHash > nextHash { // end of zone
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if nameHash > ownerHash { // covered since there is nothing after ownerHash
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return true
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}
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return nameHash < nextHash // if nameHash is before beginning of zone it is covered
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}
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if nameHash < ownerHash { // nameHash is before ownerHash, not covered
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return false
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}
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return nameHash < nextHash // if nameHash is before nextHash is it covered (between ownerHash and nextHash)
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}
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// Match returns true if a name matches the NSEC3 record
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func (rr *NSEC3) Match(name string) bool {
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nameHash := HashName(name, rr.Hash, rr.Iterations, rr.Salt)
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owner := strings.ToUpper(rr.Hdr.Name)
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labelIndices := Split(owner)
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if len(labelIndices) < 2 {
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return false
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}
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ownerHash := owner[:labelIndices[1]-1]
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ownerZone := owner[labelIndices[1]:]
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if !IsSubDomain(ownerZone, strings.ToUpper(name)) { // name is outside owner zone
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return false
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}
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if ownerHash == nameHash {
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return true
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}
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return false
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}
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func packSaltWire(sw *saltWireFmt, msg []byte) (int, error) {
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off, err := packStringHex(sw.Salt, msg, 0)
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if err != nil {
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return off, err
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}
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return off, nil
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}
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