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namehash.go
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namehash.go
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// Copyright 2017 - 2023 Weald Technology Trading.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ens
import (
"strings"
"github.com/pkg/errors"
"golang.org/x/net/idna"
"golang.org/x/crypto/sha3"
)
var (
p = idna.New(idna.MapForLookup(), idna.ValidateLabels(false), idna.CheckHyphens(false), idna.StrictDomainName(false), idna.Transitional(false))
pStrict = idna.New(idna.MapForLookup(), idna.ValidateLabels(false), idna.CheckHyphens(false), idna.StrictDomainName(true), idna.Transitional(false))
)
// Normalize normalizes a name according to the ENS rules.
func Normalize(input string) (string, error) {
output, err := p.ToUnicode(input)
if err != nil {
return "", errors.Wrap(err, "failed to convert to standard unicode")
}
// If the name started with a period then ToUnicode() removes it, but we want to keep it.
if strings.HasPrefix(input, ".") && !strings.HasPrefix(output, ".") {
output = "." + output
}
return output, nil
}
// LabelHash generates a simple hash for a piece of a name.
func LabelHash(label string) ([32]byte, error) {
var hash [32]byte
normalizedLabel, err := Normalize(label)
if err != nil {
return [32]byte{}, err
}
sha := sha3.NewLegacyKeccak256()
if _, err = sha.Write([]byte(normalizedLabel)); err != nil {
return [32]byte{}, errors.Wrap(err, "failed to write hash")
}
sha.Sum(hash[:0])
return hash, nil
}
// NameHash generates a hash from a name that can be used to
// look up the name in ENS.
func NameHash(name string) ([32]byte, error) {
var hash [32]byte
if name == "" {
return hash, nil
}
normalizedName, err := Normalize(name)
if err != nil {
return [32]byte{}, err
}
parts := strings.Split(normalizedName, ".")
for i := len(parts) - 1; i >= 0; i-- {
if hash, err = nameHashPart(hash, parts[i]); err != nil {
return [32]byte{}, err
}
}
return hash, nil
}
func nameHashPart(currentHash [32]byte, name string) ([32]byte, error) {
var hash [32]byte
sha := sha3.NewLegacyKeccak256()
if _, err := sha.Write(currentHash[:]); err != nil {
return [32]byte{}, errors.Wrap(err, "failed to write hash")
}
nameSha := sha3.NewLegacyKeccak256()
if _, err := nameSha.Write([]byte(name)); err != nil {
return [32]byte{}, errors.Wrap(err, "failed to write hash")
}
nameHash := nameSha.Sum(nil)
if _, err := sha.Write(nameHash); err != nil {
return [32]byte{}, errors.Wrap(err, "failed to write hash")
}
sha.Sum(hash[:0])
return hash, nil
}