neo-go/pkg/network/message.go

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package network
import (
"bytes"
"crypto/sha256"
"encoding/binary"
"errors"
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"fmt"
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"io"
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"github.com/CityOfZion/neo-go/config"
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"github.com/CityOfZion/neo-go/pkg/core"
"github.com/CityOfZion/neo-go/pkg/core/transaction"
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"github.com/CityOfZion/neo-go/pkg/network/payload"
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)
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const (
// The minimum size of a valid message.
minMessageSize = 24
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cmdSize = 12
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)
var (
errChecksumMismatch = errors.New("checksum mismatch")
)
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// Message is the complete message send between nodes.
type Message struct {
// NetMode of the node that sends this message.
Magic config.NetMode
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// Command is utf8 code, of which the length is 12 bytes,
// the extra part is filled with 0.
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Command [cmdSize]byte
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// Length of the payload
Length uint32
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// Checksum is the first 4 bytes of the value that two times SHA256
// hash of the payload
Checksum uint32
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// Payload send with the message.
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Payload payload.Payload
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}
// CommandType represents the type of a message command.
type CommandType string
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// Valid protocol commands used to send between nodes.
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const (
CMDVersion CommandType = "version"
CMDVerack CommandType = "verack"
CMDGetAddr CommandType = "getaddr"
CMDAddr CommandType = "addr"
CMDGetHeaders CommandType = "getheaders"
CMDHeaders CommandType = "headers"
CMDGetBlocks CommandType = "getblocks"
CMDInv CommandType = "inv"
CMDGetData CommandType = "getdata"
CMDBlock CommandType = "block"
CMDTX CommandType = "tx"
CMDConsensus CommandType = "consensus"
CMDUnknown CommandType = "unknown"
CMDFilterAdd CommandType = "filteradd"
CMDFilterClear CommandType = "filterclear"
CMDFilterLoad CommandType = "filterload"
CMDMerkleBlock CommandType = "merkleblock"
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)
// NewMessage returns a new message with the given payload.
func NewMessage(magic config.NetMode, cmd CommandType, p payload.Payload) *Message {
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var (
size uint32
checksum []byte
)
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if p != nil {
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buf := new(bytes.Buffer)
if err := p.EncodeBinary(buf); err != nil {
panic(err)
}
size = uint32(buf.Len())
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checksum = sumSHA256(sumSHA256(buf.Bytes()))
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} else {
checksum = sumSHA256(sumSHA256([]byte{}))
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}
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return &Message{
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Magic: magic,
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Command: cmdToByteArray(cmd),
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Length: size,
Payload: p,
Checksum: binary.LittleEndian.Uint32(checksum[:4]),
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}
}
// CommandType converts the 12 byte command slice to a CommandType.
func (m *Message) CommandType() CommandType {
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cmd := cmdByteArrayToString(m.Command)
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switch cmd {
case "version":
return CMDVersion
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case "verack":
return CMDVerack
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case "getaddr":
return CMDGetAddr
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case "addr":
return CMDAddr
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case "getheaders":
return CMDGetHeaders
case "headers":
return CMDHeaders
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case "getblocks":
return CMDGetBlocks
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case "inv":
return CMDInv
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case "getdata":
return CMDGetData
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case "block":
return CMDBlock
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case "tx":
return CMDTX
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case "consensus":
return CMDConsensus
case "merkleblock":
return CMDMerkleBlock
case "filterload":
return CMDFilterLoad
case "filteradd":
return CMDFilterAdd
case "filterclear":
return CMDFilterClear
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default:
return CMDUnknown
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}
}
// Decode a Message from the given reader.
func (m *Message) Decode(r io.Reader) error {
if err := binary.Read(r, binary.LittleEndian, &m.Magic); err != nil {
return err
}
if err := binary.Read(r, binary.LittleEndian, &m.Command); err != nil {
return err
}
if err := binary.Read(r, binary.LittleEndian, &m.Length); err != nil {
return err
}
if err := binary.Read(r, binary.LittleEndian, &m.Checksum); err != nil {
return err
}
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// return if their is no payload.
if m.Length == 0 {
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return nil
}
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return m.decodePayload(r)
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}
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func (m *Message) decodePayload(r io.Reader) error {
buf := new(bytes.Buffer)
n, err := io.CopyN(buf, r, int64(m.Length))
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if err != nil {
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return err
}
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if uint32(n) != m.Length {
return fmt.Errorf("expected to have read exactly %d bytes got %d", m.Length, n)
}
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// Compare the checksum of the payload.
if !compareChecksum(m.Checksum, buf.Bytes()) {
return errChecksumMismatch
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}
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var p payload.Payload
switch m.CommandType() {
case CMDVersion:
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p = &payload.Version{}
if err := p.DecodeBinary(buf); err != nil {
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return err
}
case CMDInv:
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p = &payload.Inventory{}
if err := p.DecodeBinary(buf); err != nil {
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return err
}
case CMDAddr:
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p = &payload.AddressList{}
if err := p.DecodeBinary(buf); err != nil {
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return err
}
case CMDBlock:
p = &core.Block{}
if err := p.DecodeBinary(buf); err != nil {
return err
}
case CMDGetHeaders:
p = &payload.GetBlocks{}
if err := p.DecodeBinary(buf); err != nil {
return err
}
case CMDHeaders:
p = &payload.Headers{}
if err := p.DecodeBinary(buf); err != nil {
return err
}
case CMDTX:
p = &transaction.Transaction{}
if err := p.DecodeBinary(buf); err != nil {
return err
}
case CMDMerkleBlock:
p = &payload.MerkleBlock{}
if err := p.DecodeBinary(buf); err != nil {
return err
}
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}
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m.Payload = p
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return nil
}
// Encode a Message to any given io.Writer.
func (m *Message) Encode(w io.Writer) error {
if err := binary.Write(w, binary.LittleEndian, m.Magic); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, m.Command); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, m.Length); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, m.Checksum); err != nil {
return err
}
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if m.Payload != nil {
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return m.Payload.EncodeBinary(w)
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}
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return nil
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}
// convert a command (string) to a byte slice filled with 0 bytes till
// size 12.
func cmdToByteArray(cmd CommandType) [cmdSize]byte {
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cmdLen := len(cmd)
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if cmdLen > cmdSize {
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panic("exceeded command max length of size 12")
}
// The command can have max 12 bytes, rest is filled with 0.
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b := [cmdSize]byte{}
for i := 0; i < cmdLen; i++ {
b[i] = cmd[i]
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}
return b
}
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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)
}
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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
}