// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package enr implements Ethereum Node Records as defined in EIP-778. A node record holds
// arbitrary information about a node on the peer-to-peer network.
//
// Records contain named keys. To store and retrieve key/values in a record, use the Entry
// interface.
//
// Records must be signed before transmitting them to another node. Decoding a record verifies
// its signature. When creating a record, set the entries you want, then call Sign to add the
// signature. Modifying a record invalidates the signature.
//
// Package enr supports the "secp256k1-keccak" identity scheme.
package enr
import (
"bytes"
"crypto/ecdsa"
"errors"
"fmt"
"io"
"sort"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/crypto/sha3"
"github.com/ethereum/go-ethereum/rlp"
)
const SizeLimit = 300 // maximum encoded size of a node record in bytes
const ID_SECP256k1_KECCAK = ID("secp256k1-keccak") // the default identity scheme
var (
errNoID = errors.New("unknown or unspecified identity scheme")
errInvalidSigsize = errors.New("invalid signature size")
errInvalidSig = errors.New("invalid signature")
errNotSorted = errors.New("record key/value pairs are not sorted by key")
errDuplicateKey = errors.New("record contains duplicate key")
errIncompletePair = errors.New("record contains incomplete k/v pair")
errTooBig = fmt.Errorf("record bigger than %d bytes", SizeLimit)
errEncodeUnsigned = errors.New("can't encode unsigned record")
errNotFound = errors.New("no such key in record")
)
// Record represents a node record. The zero value is an empty record.
type Record struct {
seq uint64 // sequence number
signature []byte // the signature
raw []byte // RLP encoded record
pairs []pair // sorted list of all key/value pairs
}
// pair is a key/value pair in a record.
type pair struct {
k string
v rlp.RawValue
}
// Signed reports whether the record has a valid signature.
func (r *Record) Signed() bool {
return r.signature != nil
}
// Seq returns the sequence number.
func (r *Record) Seq() uint64 {
return r.seq
}
// SetSeq updates the record sequence number. This invalidates any signature on the record.
// Calling SetSeq is usually not required because signing the redord increments the
// sequence number.
func (r *Record) SetSeq(s uint64) {
r.signature = nil
r.raw = nil
r.seq = s
}
// Load retrieves the value of a key/value pair. The given Entry must be a pointer and will
// be set to the value of the entry in the record.
//
// Errors returned by Load are wrapped in KeyError. You can distinguish decoding errors
// from missing keys using the IsNotFound function.
func (r *Record) Load(e Entry) error {
i := sort.Search(len(r.pairs), func(i int) bool { return r.pairs[i].k >= e.ENRKey() })
if i < len(r.pairs) && r.pairs[i].k == e.ENRKey() {
if err := rlp.DecodeBytes(r.pairs[i].v, e); err != nil {
return &KeyError{Key: e.ENRKey(), Err: err}
}
return nil
}
return &KeyError{Key: e.ENRKey(), Err: errNotFound}
}
// Set adds or updates the given entry in the record.
// It panics if the value can't be encoded.
func (r *Record) Set(e Entry) {
r.signature = nil
r.raw = nil
blob, err := rlp.EncodeToBytes(e)
if err != nil {
panic(fmt.Errorf("enr: can't encode %s: %v", e.ENRKey(), err))
}
i := sort.Search(len(r.pairs), func(i int) bool { return r.pairs[i].k >= e.ENRKey() })
if i < len(r.pairs) && r.pairs[i].k == e.ENRKey() {
// element is present at r.pairs[i]
r.pairs[i].v = blob
return
} else if i < len(r.pairs) {
// insert pair before i-th elem
el := pair{e.ENRKey(), blob}
r.pairs = append(r.pairs, pair{})
copy(r.pairs[i+1:], r.pairs[i:])
r.pairs[i] = el
return
}
// element should be placed at the end of r.pairs
r.pairs = append(r.pairs, pair{e.ENRKey(), blob})
}
// EncodeRLP implements rlp.Encoder. Encoding fails if
// the record is unsigned.
func (r Record) EncodeRLP(w io.Writer) error {
if !r.Signed() {
return errEncodeUnsigned
}
_, err := w.Write(r.raw)
return err
}
// DecodeRLP implements rlp.Decoder. Decoding verifies the signature.
func (r *Record) DecodeRLP(s *rlp.Stream) error {
raw, err := s.Raw()
if err != nil {
return err
}
if len(raw) > SizeLimit {
return errTooBig
}
// Decode the RLP container.
dec := Record{raw: raw}
s = rlp.NewStream(bytes.NewReader(raw), 0)
if _, err := s.List(); err != nil {
return err
}
if err = s.Decode(&dec.signature); err != nil {
return err
}
if err = s.Decode(&dec.seq); err != nil {
return err
}
// The rest of the record contains sorted k/v pairs.
var prevkey string
for i := 0; ; i++ {
var kv pair
if err := s.Decode(&kv.k); err != nil {
if err == rlp.EOL {
break
}
return err
}
if err := s.Decode(&kv.v); err != nil {
if err == rlp.EOL {
return errIncompletePair
}
return err
}
if i > 0 {
if kv.k == prevkey {
return errDuplicateKey
}
if kv.k < prevkey {
return errNotSorted
}
}
dec.pairs = append(dec.pairs, kv)
prevkey = kv.k
}
if err := s.ListEnd(); err != nil {
return err
}
// Verify signature.
if err = dec.verifySignature(); err != nil {
return err
}
*r = dec
return nil
}
type s256raw []byte
func (s256raw) ENRKey() string { return "secp256k1" }
// NodeAddr returns the node address. The return value will be nil if the record is
// unsigned.
func (r *Record) NodeAddr() []byte {
var entry s256raw
if r.Load(&entry) != nil {
return nil
}
return crypto.Keccak256(entry)
}
// Sign signs the record with the given private key. It updates the record's identity
// scheme, public key and increments the sequence number. Sign returns an error if the
// encoded record is larger than the size limit.
func (r *Record) Sign(privkey *ecdsa.PrivateKey) error {
r.seq = r.seq + 1
r.Set(ID_SECP256k1_KECCAK)
r.Set(Secp256k1(privkey.PublicKey))
return r.signAndEncode(privkey)
}
func (r *Record) appendPairs(list []interface{}) []interface{} {
list = append(list, r.seq)
for _, p := range r.pairs {
list = append(list, p.k, p.v)
}
return list
}
func (r *Record) signAndEncode(privkey *ecdsa.PrivateKey) error {
// Put record elements into a flat list. Leave room for the signature.
list := make([]interface{}, 1, len(r.pairs)*2+2)
list = r.appendPairs(list)
// Sign the tail of the list.
h := sha3.NewKeccak256()
rlp.Encode(h, list[1:])
sig, err := crypto.Sign(h.Sum(nil), privkey)
if err != nil {
return err
}
sig = sig[:len(sig)-1] // remove v
// Put signature in front.
r.signature, list[0] = sig, sig
r.raw, err = rlp.EncodeToBytes(list)
if err != nil {
return err
}
if len(r.raw) > SizeLimit {
return errTooBig
}
return nil
}
func (r *Record) verifySignature() error {
// Get identity scheme, public key, signature.
var id ID
var entry s256raw
if err := r.Load(&id); err != nil {
return err
} else if id != ID_SECP256k1_KECCAK {
return errNoID
}
if err := r.Load(&entry); err != nil {
return err
} else if len(entry) != 33 {
return fmt.Errorf("invalid public key")
}
// Verify the signature.
list := make([]interface{}, 0, len(r.pairs)*2+1)
list = r.appendPairs(list)
h := sha3.NewKeccak256()
rlp.Encode(h, list)
if !crypto.VerifySignature(entry, h.Sum(nil), r.signature) {
return errInvalidSig
}
return nil
}
