neo-go/pkg/network/message.go

253 lines
5.3 KiB
Go

package network
import (
"bytes"
"crypto/sha256"
"encoding/binary"
"errors"
"fmt"
"io"
"github.com/anthdm/neo-go/pkg/core"
"github.com/anthdm/neo-go/pkg/network/payload"
)
const (
// The minimum size of a valid message.
minMessageSize = 24
cmdSize = 12
)
var (
errChecksumMismatch = errors.New("checksum mismatch")
)
// NetMode type that is compatible with netModes below.
type NetMode uint32
// String implements the stringer interface.
func (n NetMode) String() string {
switch n {
case ModeDevNet:
return "devnet"
case ModeTestNet:
return "testnet"
case ModeMainNet:
return "mainnet"
default:
return ""
}
}
// Values used for the magic field, according to the docs.
const (
ModeMainNet NetMode = 0x00746e41 // 7630401
ModeTestNet = 0x74746e41 // 1953787457
ModeDevNet = 56753 // docker privnet
)
// Message is the complete message send between nodes.
type Message struct {
Magic NetMode
// Command is utf8 code, of which the length is 12 bytes,
// the extra part is filled with 0.
Command [cmdSize]byte
// Length of the payload
Length uint32
// Checksum is the first 4 bytes of the value that two times SHA256
// hash of the payload
Checksum uint32
// Payload send with the message.
Payload payload.Payload
}
type commandType string
// valid commands used to send between nodes.
const (
cmdVersion commandType = "version"
cmdVerack = "verack"
cmdGetAddr = "getaddr"
cmdAddr = "addr"
cmdGetHeaders = "getheaders"
cmdHeaders = "headers"
cmdGetBlocks = "getblocks"
cmdInv = "inv"
cmdGetData = "getdata"
cmdBlock = "block"
cmdTX = "tx"
cmdConsensus = "consensus"
)
func newMessage(magic NetMode, cmd commandType, p payload.Payload) *Message {
var (
size uint32
checksum []byte
)
if p != nil {
buf := new(bytes.Buffer)
if err := p.EncodeBinary(buf); err != nil {
panic(err)
}
size = uint32(buf.Len())
checksum = sumSHA256(sumSHA256(buf.Bytes()))
} else {
checksum = sumSHA256(sumSHA256([]byte{}))
}
return &Message{
Magic: magic,
Command: cmdToByteArray(cmd),
Length: size,
Payload: p,
Checksum: binary.LittleEndian.Uint32(checksum[:4]),
}
}
// Converts the 12 byte command slice to a commandType.
func (m *Message) commandType() commandType {
cmd := cmdByteArrayToString(m.Command)
switch cmd {
case "version":
return cmdVersion
case "verack":
return cmdVerack
case "getaddr":
return cmdGetAddr
case "addr":
return cmdAddr
case "getheaders":
return cmdGetHeaders
case "header":
return cmdHeaders
case "getblocks":
return cmdGetBlocks
case "inv":
return cmdInv
case "getdata":
return cmdGetData
case "block":
return cmdBlock
case "tx":
return cmdTX
case "consensus":
return cmdConsensus
default:
return ""
}
}
// decode a Message from the given reader.
func (m *Message) decode(r io.Reader) error {
binary.Read(r, binary.LittleEndian, &m.Magic)
binary.Read(r, binary.LittleEndian, &m.Command)
binary.Read(r, binary.LittleEndian, &m.Length)
binary.Read(r, binary.LittleEndian, &m.Checksum)
// return if their is no payload.
if m.Length == 0 {
return nil
}
return m.decodePayload(r)
}
func (m *Message) decodePayload(r io.Reader) error {
buf := make([]byte, m.Length)
n, err := r.Read(buf)
if err != nil {
return err
}
if uint32(n) != m.Length {
return fmt.Errorf("expected to have read exactly %d bytes got %d", m.Length, n)
}
// Compare the checksum of the payload.
if !compareChecksum(m.Checksum, buf) {
return errChecksumMismatch
}
r = bytes.NewReader(buf)
var p payload.Payload
switch m.commandType() {
case cmdVersion:
p = &payload.Version{}
if err := p.DecodeBinary(r); err != nil {
return err
}
case cmdInv:
p = &payload.Inventory{}
if err := p.DecodeBinary(r); err != nil {
return err
}
case cmdAddr:
p = &payload.AddressList{}
if err := p.DecodeBinary(r); err != nil {
return err
}
case cmdBlock:
p = &core.Block{}
if err := p.DecodeBinary(r); err != nil {
return err
}
}
m.Payload = p
return nil
}
// encode a Message to any given io.Writer.
func (m *Message) encode(w io.Writer) error {
binary.Write(w, binary.LittleEndian, m.Magic)
binary.Write(w, binary.LittleEndian, m.Command)
binary.Write(w, binary.LittleEndian, m.Length)
binary.Write(w, binary.LittleEndian, m.Checksum)
if m.Payload != nil {
return m.Payload.EncodeBinary(w)
}
return nil
}
// convert a command (string) to a byte slice filled with 0 bytes till
// size 12.
func cmdToByteArray(cmd commandType) [cmdSize]byte {
cmdLen := len(cmd)
if cmdLen > cmdSize {
panic("exceeded command max length of size 12")
}
// The command can have max 12 bytes, rest is filled with 0.
b := [cmdSize]byte{}
for i := 0; i < cmdLen; i++ {
b[i] = cmd[i]
}
return b
}
func cmdByteArrayToString(cmd [cmdSize]byte) string {
buf := []byte{}
for i := 0; i < cmdSize; i++ {
if cmd[i] != 0 {
buf = append(buf, cmd[i])
}
}
return string(buf)
}
func sumSHA256(b []byte) []byte {
h := sha256.New()
h.Write(b)
return h.Sum(nil)
}
func compareChecksum(have uint32, b []byte) bool {
sum := sumSHA256(sumSHA256(b))[:4]
want := binary.LittleEndian.Uint32(sum)
return have == want
}