Official Go implementation of the Ethereum protocol
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go-ethereum/p2p/discover/v4wire/v4wire.go

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// Copyright 2020 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 v4wire implements the Discovery v4 Wire Protocol.
package v4wire
import (
"bytes"
"crypto/ecdsa"
"crypto/elliptic"
"errors"
"fmt"
"math/big"
"net"
"time"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/p2p/enr"
"github.com/ethereum/go-ethereum/rlp"
)
// RPC packet types
const (
PingPacket = iota + 1 // zero is 'reserved'
PongPacket
FindnodePacket
NeighborsPacket
ENRRequestPacket
ENRResponsePacket
)
// RPC request structures
type (
Ping struct {
Version uint
From, To Endpoint
Expiration uint64
ENRSeq uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// Pong is the reply to ping.
Pong struct {
// This field should mirror the UDP envelope address
// of the ping packet, which provides a way to discover the
// the external address (after NAT).
To Endpoint
ReplyTok []byte // This contains the hash of the ping packet.
Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
ENRSeq uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// Findnode is a query for nodes close to the given target.
Findnode struct {
Target Pubkey
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// Neighbors is the reply to findnode.
Neighbors struct {
Nodes []Node
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// enrRequest queries for the remote node's record.
ENRRequest struct {
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// enrResponse is the reply to enrRequest.
ENRResponse struct {
ReplyTok []byte // Hash of the enrRequest packet.
Record enr.Record
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
)
// This number is the maximum number of neighbor nodes in a Neighbors packet.
const MaxNeighbors = 12
// This code computes the MaxNeighbors constant value.
// func init() {
// var maxNeighbors int
// p := Neighbors{Expiration: ^uint64(0)}
// maxSizeNode := Node{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
// for n := 0; ; n++ {
// p.Nodes = append(p.Nodes, maxSizeNode)
// size, _, err := rlp.EncodeToReader(p)
// if err != nil {
// // If this ever happens, it will be caught by the unit tests.
// panic("cannot encode: " + err.Error())
// }
// if headSize+size+1 >= 1280 {
// maxNeighbors = n
// break
// }
// }
// fmt.Println("maxNeighbors", maxNeighbors)
// }
// Pubkey represents an encoded 64-byte secp256k1 public key.
type Pubkey [64]byte
// ID returns the node ID corresponding to the public key.
func (e Pubkey) ID() enode.ID {
return enode.ID(crypto.Keccak256Hash(e[:]))
}
// Node represents information about a node.
type Node struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
ID Pubkey
}
// Endpoint represents a network endpoint.
type Endpoint struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
}
// NewEndpoint creates an endpoint.
func NewEndpoint(addr *net.UDPAddr, tcpPort uint16) Endpoint {
ip := net.IP{}
if ip4 := addr.IP.To4(); ip4 != nil {
ip = ip4
} else if ip6 := addr.IP.To16(); ip6 != nil {
ip = ip6
}
return Endpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
}
type Packet interface {
// packet name and type for logging purposes.
Name() string
Kind() byte
}
func (req *Ping) Name() string { return "PING/v4" }
func (req *Ping) Kind() byte { return PingPacket }
func (req *Pong) Name() string { return "PONG/v4" }
func (req *Pong) Kind() byte { return PongPacket }
func (req *Findnode) Name() string { return "FINDNODE/v4" }
func (req *Findnode) Kind() byte { return FindnodePacket }
func (req *Neighbors) Name() string { return "NEIGHBORS/v4" }
func (req *Neighbors) Kind() byte { return NeighborsPacket }
func (req *ENRRequest) Name() string { return "ENRREQUEST/v4" }
func (req *ENRRequest) Kind() byte { return ENRRequestPacket }
func (req *ENRResponse) Name() string { return "ENRRESPONSE/v4" }
func (req *ENRResponse) Kind() byte { return ENRResponsePacket }
// Expired checks whether the given UNIX time stamp is in the past.
func Expired(ts uint64) bool {
return time.Unix(int64(ts), 0).Before(time.Now())
}
// Encoder/decoder.
const (
macSize = 32
sigSize = crypto.SignatureLength
headSize = macSize + sigSize // space of packet frame data
)
var (
ErrPacketTooSmall = errors.New("too small")
ErrBadHash = errors.New("bad hash")
ErrBadPoint = errors.New("invalid curve point")
)
var headSpace = make([]byte, headSize)
// Decode reads a discovery v4 packet.
func Decode(input []byte) (Packet, Pubkey, []byte, error) {
if len(input) < headSize+1 {
return nil, Pubkey{}, nil, ErrPacketTooSmall
}
hash, sig, sigdata := input[:macSize], input[macSize:headSize], input[headSize:]
shouldhash := crypto.Keccak256(input[macSize:])
if !bytes.Equal(hash, shouldhash) {
return nil, Pubkey{}, nil, ErrBadHash
}
fromKey, err := recoverNodeKey(crypto.Keccak256(input[headSize:]), sig)
if err != nil {
return nil, fromKey, hash, err
}
var req Packet
switch ptype := sigdata[0]; ptype {
case PingPacket:
req = new(Ping)
case PongPacket:
req = new(Pong)
case FindnodePacket:
req = new(Findnode)
case NeighborsPacket:
req = new(Neighbors)
case ENRRequestPacket:
req = new(ENRRequest)
case ENRResponsePacket:
req = new(ENRResponse)
default:
return nil, fromKey, hash, fmt.Errorf("unknown type: %d", ptype)
}
s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
err = s.Decode(req)
return req, fromKey, hash, err
}
// Encode encodes a discovery packet.
func Encode(priv *ecdsa.PrivateKey, req Packet) (packet, hash []byte, err error) {
b := new(bytes.Buffer)
b.Write(headSpace)
b.WriteByte(req.Kind())
if err := rlp.Encode(b, req); err != nil {
return nil, nil, err
}
packet = b.Bytes()
sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
if err != nil {
return nil, nil, err
}
copy(packet[macSize:], sig)
// Add the hash to the front. Note: this doesn't protect the packet in any way.
hash = crypto.Keccak256(packet[macSize:])
copy(packet, hash)
return packet, hash, nil
}
// recoverNodeKey computes the public key used to sign the given hash from the signature.
func recoverNodeKey(hash, sig []byte) (key Pubkey, err error) {
pubkey, err := crypto.Ecrecover(hash, sig)
if err != nil {
return key, err
}
copy(key[:], pubkey[1:])
return key, nil
}
// EncodePubkey encodes a secp256k1 public key.
func EncodePubkey(key *ecdsa.PublicKey) Pubkey {
var e Pubkey
math.ReadBits(key.X, e[:len(e)/2])
math.ReadBits(key.Y, e[len(e)/2:])
return e
}
// DecodePubkey reads an encoded secp256k1 public key.
func DecodePubkey(curve elliptic.Curve, e Pubkey) (*ecdsa.PublicKey, error) {
p := &ecdsa.PublicKey{Curve: curve, X: new(big.Int), Y: new(big.Int)}
half := len(e) / 2
p.X.SetBytes(e[:half])
p.Y.SetBytes(e[half:])
if !p.Curve.IsOnCurve(p.X, p.Y) {
return nil, ErrBadPoint
}
return p, nil
}