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293 lines
8.2 KiB
293 lines
8.2 KiB
// Copyright 2020 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Package v4wire implements the Discovery v4 Wire Protocol.
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package v4wire
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import (
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"bytes"
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"crypto/ecdsa"
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"crypto/elliptic"
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"errors"
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"fmt"
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"math/big"
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"net"
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"time"
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"github.com/ethereum/go-ethereum/common/math"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/p2p/enode"
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"github.com/ethereum/go-ethereum/p2p/enr"
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"github.com/ethereum/go-ethereum/rlp"
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)
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// RPC packet types
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const (
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PingPacket = iota + 1 // zero is 'reserved'
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PongPacket
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FindnodePacket
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NeighborsPacket
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ENRRequestPacket
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ENRResponsePacket
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)
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// RPC request structures
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type (
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Ping struct {
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Version uint
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From, To Endpoint
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Expiration uint64
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ENRSeq uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.
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// Ignore additional fields (for forward compatibility).
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Rest []rlp.RawValue `rlp:"tail"`
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}
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// Pong is the reply to ping.
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Pong struct {
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// This field should mirror the UDP envelope address
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// of the ping packet, which provides a way to discover the
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// external address (after NAT).
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To Endpoint
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ReplyTok []byte // This contains the hash of the ping packet.
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Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
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ENRSeq uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.
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// Ignore additional fields (for forward compatibility).
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Rest []rlp.RawValue `rlp:"tail"`
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}
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// Findnode is a query for nodes close to the given target.
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Findnode struct {
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Target Pubkey
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Expiration uint64
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// Ignore additional fields (for forward compatibility).
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Rest []rlp.RawValue `rlp:"tail"`
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}
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// Neighbors is the reply to findnode.
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Neighbors struct {
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Nodes []Node
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Expiration uint64
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// Ignore additional fields (for forward compatibility).
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Rest []rlp.RawValue `rlp:"tail"`
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}
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// ENRRequest queries for the remote node's record.
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ENRRequest struct {
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Expiration uint64
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// Ignore additional fields (for forward compatibility).
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Rest []rlp.RawValue `rlp:"tail"`
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}
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// ENRResponse is the reply to ENRRequest.
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ENRResponse struct {
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ReplyTok []byte // Hash of the ENRRequest packet.
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Record enr.Record
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// Ignore additional fields (for forward compatibility).
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Rest []rlp.RawValue `rlp:"tail"`
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}
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)
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// This number is the maximum number of neighbor nodes in a Neighbors packet.
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const MaxNeighbors = 12
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// This code computes the MaxNeighbors constant value.
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// func init() {
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// var maxNeighbors int
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// p := Neighbors{Expiration: ^uint64(0)}
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// maxSizeNode := Node{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
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// for n := 0; ; n++ {
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// p.Nodes = append(p.Nodes, maxSizeNode)
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// size, _, err := rlp.EncodeToReader(p)
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// if err != nil {
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// // If this ever happens, it will be caught by the unit tests.
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// panic("cannot encode: " + err.Error())
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// }
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// if headSize+size+1 >= 1280 {
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// maxNeighbors = n
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// break
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// }
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// }
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// fmt.Println("maxNeighbors", maxNeighbors)
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// }
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// Pubkey represents an encoded 64-byte secp256k1 public key.
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type Pubkey [64]byte
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// ID returns the node ID corresponding to the public key.
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func (e Pubkey) ID() enode.ID {
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return enode.ID(crypto.Keccak256Hash(e[:]))
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}
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// Node represents information about a node.
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type Node struct {
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IP net.IP // len 4 for IPv4 or 16 for IPv6
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UDP uint16 // for discovery protocol
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TCP uint16 // for RLPx protocol
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ID Pubkey
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}
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// Endpoint represents a network endpoint.
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type Endpoint struct {
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IP net.IP // len 4 for IPv4 or 16 for IPv6
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UDP uint16 // for discovery protocol
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TCP uint16 // for RLPx protocol
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}
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// NewEndpoint creates an endpoint.
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func NewEndpoint(addr *net.UDPAddr, tcpPort uint16) Endpoint {
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ip := net.IP{}
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if ip4 := addr.IP.To4(); ip4 != nil {
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ip = ip4
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} else if ip6 := addr.IP.To16(); ip6 != nil {
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ip = ip6
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}
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return Endpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
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}
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type Packet interface {
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// packet name and type for logging purposes.
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Name() string
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Kind() byte
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}
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func (req *Ping) Name() string { return "PING/v4" }
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func (req *Ping) Kind() byte { return PingPacket }
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func (req *Pong) Name() string { return "PONG/v4" }
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func (req *Pong) Kind() byte { return PongPacket }
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func (req *Findnode) Name() string { return "FINDNODE/v4" }
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func (req *Findnode) Kind() byte { return FindnodePacket }
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func (req *Neighbors) Name() string { return "NEIGHBORS/v4" }
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func (req *Neighbors) Kind() byte { return NeighborsPacket }
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func (req *ENRRequest) Name() string { return "ENRREQUEST/v4" }
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func (req *ENRRequest) Kind() byte { return ENRRequestPacket }
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func (req *ENRResponse) Name() string { return "ENRRESPONSE/v4" }
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func (req *ENRResponse) Kind() byte { return ENRResponsePacket }
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// Expired checks whether the given UNIX time stamp is in the past.
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func Expired(ts uint64) bool {
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return time.Unix(int64(ts), 0).Before(time.Now())
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}
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// Encoder/decoder.
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const (
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macSize = 32
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sigSize = crypto.SignatureLength
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headSize = macSize + sigSize // space of packet frame data
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)
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var (
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ErrPacketTooSmall = errors.New("too small")
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ErrBadHash = errors.New("bad hash")
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ErrBadPoint = errors.New("invalid curve point")
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)
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var headSpace = make([]byte, headSize)
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// Decode reads a discovery v4 packet.
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func Decode(input []byte) (Packet, Pubkey, []byte, error) {
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if len(input) < headSize+1 {
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return nil, Pubkey{}, nil, ErrPacketTooSmall
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}
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hash, sig, sigdata := input[:macSize], input[macSize:headSize], input[headSize:]
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shouldhash := crypto.Keccak256(input[macSize:])
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if !bytes.Equal(hash, shouldhash) {
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return nil, Pubkey{}, nil, ErrBadHash
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}
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fromKey, err := recoverNodeKey(crypto.Keccak256(input[headSize:]), sig)
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if err != nil {
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return nil, fromKey, hash, err
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}
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var req Packet
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switch ptype := sigdata[0]; ptype {
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case PingPacket:
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req = new(Ping)
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case PongPacket:
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req = new(Pong)
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case FindnodePacket:
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req = new(Findnode)
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case NeighborsPacket:
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req = new(Neighbors)
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case ENRRequestPacket:
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req = new(ENRRequest)
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case ENRResponsePacket:
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req = new(ENRResponse)
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default:
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return nil, fromKey, hash, fmt.Errorf("unknown type: %d", ptype)
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}
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s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
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err = s.Decode(req)
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return req, fromKey, hash, err
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}
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// Encode encodes a discovery packet.
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func Encode(priv *ecdsa.PrivateKey, req Packet) (packet, hash []byte, err error) {
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b := new(bytes.Buffer)
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b.Write(headSpace)
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b.WriteByte(req.Kind())
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if err := rlp.Encode(b, req); err != nil {
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return nil, nil, err
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}
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packet = b.Bytes()
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sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
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if err != nil {
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return nil, nil, err
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}
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copy(packet[macSize:], sig)
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// Add the hash to the front. Note: this doesn't protect the packet in any way.
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hash = crypto.Keccak256(packet[macSize:])
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copy(packet, hash)
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return packet, hash, nil
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}
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// recoverNodeKey computes the public key used to sign the given hash from the signature.
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func recoverNodeKey(hash, sig []byte) (key Pubkey, err error) {
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pubkey, err := crypto.Ecrecover(hash, sig)
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if err != nil {
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return key, err
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}
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copy(key[:], pubkey[1:])
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return key, nil
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}
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// EncodePubkey encodes a secp256k1 public key.
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func EncodePubkey(key *ecdsa.PublicKey) Pubkey {
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var e Pubkey
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math.ReadBits(key.X, e[:len(e)/2])
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math.ReadBits(key.Y, e[len(e)/2:])
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return e
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}
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// DecodePubkey reads an encoded secp256k1 public key.
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func DecodePubkey(curve elliptic.Curve, e Pubkey) (*ecdsa.PublicKey, error) {
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p := &ecdsa.PublicKey{Curve: curve, X: new(big.Int), Y: new(big.Int)}
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half := len(e) / 2
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p.X.SetBytes(e[:half])
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p.Y.SetBytes(e[half:])
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if !p.Curve.IsOnCurve(p.X, p.Y) {
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return nil, ErrBadPoint
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}
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return p, nil
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}
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