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main.go
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main.go
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package main
import (
"bytes"
"crypto/sha256"
"encoding/binary"
"encoding/gob"
"encoding/hex"
"encoding/json"
"fmt"
"html/template"
"io"
"io/ioutil"
"log"
"math"
"math/big"
"net"
"net/http"
"os"
"strconv"
"strings"
"sync"
"time"
"github.com/davecgh/go-spew/spew"
"github.com/gorilla/mux"
"github.com/spf13/pflag"
)
/***********
* Structs *
***********/
type Block struct {
Index int
Timestamp string
Data string
Hash string
PrevHash string
Nonce int
}
type ProofOfWork struct {
block *Block
target *big.Int
}
type Message struct {
Data string
}
type Hello struct {
AddrFrom string
Purpose string
}
type Addr struct {
AddrFrom string
AddrList []string
}
type GetChain struct {
AddrFrom string
}
type Chain struct {
AddrFrom string
BlockChain []Block
}
type CheckBlock struct {
AddrFrom string
Block Block
}
/*************
* Variables *
*************/
var (
nodeAddress string
httpPort int
KnownNodes []string
Blockchain []Block
mutex = &sync.Mutex{}
maxNonce = math.MaxInt64
ValidChan = make(chan bool)
jsonflag = false
broadcastflag = true
tmpls = template.Must(template.ParseFiles("web/index.html"))
hostFlag = pflag.StringP("host", "h", GetOutboundIP(), "binding host")
portFlag = pflag.IntP("port", "p", 4444, "binding port")
httpPortFlag = pflag.IntP("webport", "w", 8000, "web server port")
)
const (
targetBits = 18 // difficulty setting
printedLength = 8 // printedLength is the total prefix length of a public key associated to a chat users ID.
commandLength = 12
protocol = "tcp"
layout = "2006-01-02 15:04:05"
)
/*************
* Functions *
*************/
func main() {
go StartServer()
log.Fatal(run())
}
/*****************
* P2P Functions *
*****************/
func StartServer() {
pflag.Parse()
nodeAddress = fmt.Sprintf("%s:%d", *hostFlag, *portFlag)
fmt.Printf("You are %s\n", nodeAddress)
// add self to KnownNodes
KnownNodes = append(KnownNodes, nodeAddress)
// Node Discovery begins
if len(pflag.Args()) == 1 {
peer := pflag.Args()[0]
// send hello request to connecting peer, asking for peer's address list
fmt.Printf("Connecting to %s.\n", peer)
SendHello(peer, "neighbour")
} else if len(pflag.Args()) == 0 {
fmt.Println("No peers to connect to, generating blockchain")
StartBlockchain()
} else {
fmt.Println("Too many arguments! Select a peer.")
os.Exit(1)
}
ln, err := net.Listen(protocol, nodeAddress)
if err != nil {
log.Panic(err)
}
defer ln.Close()
for {
conn, err := ln.Accept()
if err != nil {
log.Panic(err)
}
go HandleConnection(conn)
}
}
/* GetOutboundIP is to find ip of host for p2p discovery */
func GetOutboundIP() string {
conn, err := net.Dial("udp", "8.8.8.8:80")
if err != nil {
log.Fatal(err)
}
defer conn.Close()
localAddr := conn.LocalAddr().(*net.UDPAddr)
return localAddr.IP.String()
}
/* HandleConnection is the main handler for any connection to the host */
func HandleConnection(conn net.Conn) {
req, err := ioutil.ReadAll(conn)
defer conn.Close()
if err != nil {
log.Panic(err)
}
command := BytesToCmd(req[:commandLength])
fmt.Printf("Received %s command\n", command)
switch command {
case "hello":
HandleHello(req)
case "addr":
HandleAddr(req)
case "getchain":
HandleGetChain(req)
case "chain":
HandleChain(req)
case "checkblock":
HandleCheckBlock(req)
default:
fmt.Println("Unknown command")
}
}
/* HandleHello handles hello requests which does node discovery.
* Neighbour is used when a new node does its first communication with a known node to request for their address list.
* Ping is used to communicate to a node in peer's address list and waits for a pong.
* Pong is used to confirm a ping to start getting a peer's chain. */
func HandleHello(request []byte) {
var buff bytes.Buffer
var payload Hello
buff.Write(request[commandLength:])
dec := gob.NewDecoder(&buff)
err := dec.Decode(&payload)
if err != nil {
log.Panic(err)
}
switch payload.Purpose {
case "neighbour":
KnownNodes = append(KnownNodes, payload.AddrFrom)
fmt.Println(KnownNodes)
SendAddr(payload.AddrFrom)
case "ping":
if !NodeIsKnown(payload.AddrFrom) {
KnownNodes = append(KnownNodes, payload.AddrFrom)
}
fmt.Println(KnownNodes)
SendHello(payload.AddrFrom, "pong")
case "pong":
if broadcastflag {
broadcastflag = false
RequestChain()
}
default:
fmt.Println("Unknown Hello Purpose")
}
}
/* HandleAddr handles Addr request which is a slice of known nodes from a peer.
* These nodes will be appended to known nodes.
* Hello ping requests will be sent to newly discovered nodes */
func HandleAddr(request []byte) {
var buff bytes.Buffer
var payload Addr
buff.Write(request[commandLength:])
dec := gob.NewDecoder(&buff)
err := dec.Decode(&payload)
if err != nil {
log.Panic(err)
}
// append nodes to KnownNodes
for _, ip := range payload.AddrList {
if !NodeIsKnown(ip) {
KnownNodes = append(KnownNodes, ip)
}
}
// send hello ping requests to newly discovered nodes
for _, node := range KnownNodes {
if node != nodeAddress {
SendHello(node, "ping")
}
}
}
/* HandleGetChain handles GetChain requests which is a request for the host's blockchain.
* host will call SendChain.*/
func HandleGetChain(request []byte) {
var buff bytes.Buffer
var payload GetChain
buff.Write(request[commandLength:])
dec := gob.NewDecoder(&buff)
err := dec.Decode(&payload)
if err != nil {
log.Panic(err)
}
SendChain(payload.AddrFrom)
}
/* HandleChain handles chain requests which compares payload blockchain and its own blockchain.
* The longer chain will be the current blockchain.
* jsonflag used to signal isValid in HandleWriteBlock to update web server. */
func HandleChain(request []byte) {
var buff bytes.Buffer
var payload Chain
buff.Write(request[commandLength:])
dec := gob.NewDecoder(&buff)
err := dec.Decode(&payload)
if err != nil {
log.Panic(err)
}
// replace BlockChain if payload chain is longer
if len(payload.BlockChain) > len(Blockchain) {
fmt.Println("Longer chain detected, replacing current chain")
Blockchain = payload.BlockChain
spew.Dump(Blockchain)
if jsonflag {
ValidChan <- true
}
} else {
fmt.Println("Discarded new chain")
if jsonflag {
ValidChan <- false
}
}
}
/* HandleCheckBlock handles CheckBlock requests which validates the sent block.
* Valid blocks will be appended to host's blockchain.
* host's chain will then be sent back to the sender. */
func HandleCheckBlock(request []byte) {
var buff bytes.Buffer
var payload CheckBlock
buff.Write(request[commandLength:])
dec := gob.NewDecoder(&buff)
err := dec.Decode(&payload)
if err != nil {
log.Panic(err)
}
mutex.Lock()
pow := NewProofOfWork(&payload.Block)
if pow.Validate() {
fmt.Println("Block is valid")
Blockchain = append(Blockchain, payload.Block)
spew.Dump(Blockchain)
} else {
fmt.Println("Block not valid")
}
mutex.Unlock()
// Send Chain to sender
SendChain(payload.AddrFrom)
}
/* SendHello sends hello requests for node discovery.
* Neighbour is used when a new node does its first communication with a known node to request for their address list.
* Ping is used to communicate to a node in peer's address list and waits for a pong.
* Pong is used to confirm a ping to start getting a peer's chain. */
func SendHello(address, purpose string) {
fmt.Printf("Sending hello %s to %s.\n", purpose, address)
data := Hello{nodeAddress, purpose}
payload := GobEncode(data)
request := append(CmdToBytes("hello"), payload...)
SendData(address, request)
}
/* SendAddr sends addr requests, sending the host's KnownNodes. */
func SendAddr(address string) {
fmt.Printf("Sending addr to %s.\n", address)
data := Addr{nodeAddress, KnownNodes}
payload := GobEncode(data)
request := append(CmdToBytes("addr"), payload...)
SendData(address, request)
}
/* SendGetChain sends getchain requests, asking the address for their blockchain. */
func SendGetChain(address string) {
fmt.Printf("Sending getchain to %s.\n", address)
data := GetChain{nodeAddress}
payload := GobEncode(data)
request := append(CmdToBytes("getchain"), payload...)
SendData(address, request)
}
/* SendChain sends chain requests consisting of host's blockchain to address. */
func SendChain(address string) {
fmt.Printf("Sending chain to %s.\n", address)
data := Chain{nodeAddress, Blockchain}
payload := GobEncode(data)
request := append(CmdToBytes("chain"), payload...)
SendData(address, request)
}
/* SendCheckBlock sends checkblock requests containing a newblock which is to be validated by address peer. */
func SendCheckBlock(address string, newBlock Block) {
fmt.Printf("Sending checkblock to %s.\n", address)
data := CheckBlock{nodeAddress, newBlock}
payload := GobEncode(data)
request := append(CmdToBytes("checkblock"), payload...)
SendData(address, request)
}
/* SendData sends data to the address.
* A connection to address is initiated. If an error occurs, address will be removed from KnownNodes. */
func SendData(address string, data []byte) {
conn, err := net.Dial(protocol, address)
if err != nil {
fmt.Printf("%s is not available\n", address)
var updatedNodes []string
for _, node := range KnownNodes {
if node != address {
updatedNodes = append(updatedNodes, node)
}
}
KnownNodes = updatedNodes
return
}
defer conn.Close()
_, err = io.Copy(conn, bytes.NewReader(data))
if err != nil {
log.Panic(err)
}
}
/* RequestChain broadcasts GetChain request to peers. */
func RequestChain() {
for _, node := range KnownNodes {
if node != nodeAddress {
SendGetChain(node)
}
}
}
func RequestCheck(newBlock Block) {
for _, address := range KnownNodes {
if address != nodeAddress{
SendCheckBlock(address, newBlock)
}
}
}
/* CmdToBytes converts a command string into a byte array of commandLength */
func CmdToBytes(cmd string) []byte {
var bytes [commandLength]byte
for i, c := range cmd {
bytes[i] = byte(c)
}
return bytes[:]
}
/* BytesToCmd converts a byte array into a command string. */
func BytesToCmd(bytes []byte) string {
var cmd []byte
for _, b := range bytes {
if b == 0x0 {
break
}
cmd = append(cmd, b)
}
return fmt.Sprintf("%s", cmd)
}
/* GobEncode converts data into a byte array */
func GobEncode(data interface{}) []byte {
var buff bytes.Buffer
enc := gob.NewEncoder(&buff)
err := enc.Encode(data)
if err != nil {
log.Panic(err)
}
return buff.Bytes()
}
/* NodeIsKnown checks the ip if it is in KnownNodes. */
func NodeIsKnown(ip string) bool {
for _, node := range KnownNodes {
if node == ip {
return true
}
}
return false
}
/************************
* Blockchain Functions *
************************/
/* NewBlock generates and returns a Block */
func NewBlock(oldBlock Block, Data string) Block {
var block Block
t := time.Now()
block.Index = oldBlock.Index + 1
block.Timestamp = t.Format(layout)
block.Data = Data
block.PrevHash = oldBlock.Hash
pow := NewProofOfWork(&block)
nonce, hash := pow.RunPOW()
block.Hash = hex.EncodeToString(hash[:])
block.Nonce = nonce
return block
}
/* StartBlockchain begins the Blockchain, appending a genesis Block */
func StartBlockchain() {
t := time.Now()
genesisBlock := Block{}
genesisBlock = Block{0, t.Format(layout), "Genesis Block", "", "", 0}
pow := NewProofOfWork(&genesisBlock)
nonce, hash := pow.RunPOW()
genesisBlock.Hash = hex.EncodeToString(hash[:])
genesisBlock.Nonce = nonce
spew.Dump(genesisBlock)
mutex.Lock()
Blockchain = append(Blockchain, genesisBlock)
mutex.Unlock()
}
/* NewProofOfWork builds and returns a ProofOfWork */
func NewProofOfWork(b *Block) *ProofOfWork {
target := big.NewInt(1)
target.Lsh(target, uint(256-targetBits))
pow := &ProofOfWork{b, target}
return pow
}
/* prepareData formats the data into a byte array */
func (pow *ProofOfWork) prepareData(nonce int) []byte {
data := bytes.Join(
[][]byte{
[]byte(pow.block.PrevHash),
[]byte(pow.block.Data),
[]byte(pow.block.Timestamp),
IntToHex(int64(pow.block.Index)),
IntToHex(int64(targetBits)),
IntToHex(int64(nonce)),
},
[]byte{},
)
return data
}
/* RunPOW performs a proof-of-work */
func (pow *ProofOfWork) RunPOW() (int, []byte) {
var hashInt big.Int
var hash [32]byte
nonce := 0
fmt.Printf("Mining the block containing \"%s\"\n", pow.block.Data)
for nonce < maxNonce {
data := pow.prepareData(nonce)
hash = sha256.Sum256(data)
fmt.Printf("\r%x", hash)
hashInt.SetBytes(hash[:])
if hashInt.Cmp(pow.target) == -1 {
break
} else {
nonce++
}
}
fmt.Print("\n\n")
return nonce, hash[:]
}
/* Validate validates block's Proof of Work
*
* Checks index, hash, prev hash.
*/
func (pow *ProofOfWork) Validate() bool {
var hashInt big.Int
data := pow.prepareData(pow.block.Nonce)
hash := sha256.Sum256(data)
hashInt.SetBytes(hash[:])
prevBlock := Blockchain[len(Blockchain)-1]
if pow.block.Index != (prevBlock.Index + 1) {
return false
}
if pow.block.PrevHash != prevBlock.Hash {
return false
}
if hashInt.Cmp(pow.target) != -1 {
return false
}
return true
}
/* IntToHex converts an int64 to a byte array */
func IntToHex(num int64) []byte {
buff := new(bytes.Buffer)
err := binary.Write(buff, binary.BigEndian, num)
if err != nil {
log.Panic(err)
}
return buff.Bytes()
}
/************************
* Web Server Functions *
************************/
/* run will set up a http server */
func run() error {
pflag.Parse()
httpPort, _ = strconv.Atoi(fmt.Sprintf("%d", *httpPortFlag))
mux := makeMuxRouter()
log.Println(fmt.Sprintf("HTTP Server Listening on port :%d", httpPort))
s := &http.Server{
Addr: fmt.Sprintf(":%d", httpPort),
Handler: mux,
ReadTimeout: 10 * time.Second,
WriteTimeout: 10 * time.Second,
MaxHeaderBytes: 1 << 20,
}
if err := s.ListenAndServe(); err != nil {
return err
}
return nil
}
/* Index sets up the index html page */
func Index(w http.ResponseWriter, r *http.Request) {
bytes, _ := json.MarshalIndent(Blockchain, "", " ")
data := struct {
Title string
Data string
Port string
}{
Title: "Blockchain Visualisation",
Data: strings.ReplaceAll(string(bytes), "\n", ""),
Port: strconv.Itoa(httpPort),
}
if err := tmpls.ExecuteTemplate(w, "index.html", data); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
}
/* makeMuxRouter creates and return a router handler*/
func makeMuxRouter() http.Handler {
muxRouter := mux.NewRouter()
muxRouter.HandleFunc("/", handleWriteBlock).Methods("POST")
muxRouter.HandleFunc("/web/", Index)
muxRouter.PathPrefix("/web/").Handler(http.StripPrefix("/web/", http.FileServer(http.Dir("web/"))))
return muxRouter
}
/* handleWriteBlock takes the JSON payload as data input and inserts a new block */
func handleWriteBlock(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
var msg Message
var isValid bool
decoder := json.NewDecoder(r.Body)
if err := decoder.Decode(&msg); err != nil {
respondWithJSON(w, r, http.StatusBadRequest, r.Body)
return
}
defer r.Body.Close()
prevBlock := Blockchain[len(Blockchain)-1]
if msg.Data == "" {
respondWithJSON(w, r, http.StatusBadRequest, r.Body)
return
}
newBlock := NewBlock(prevBlock, msg.Data)
// check if there are connected peers
if len(KnownNodes) > 1 {
go RequestCheck(newBlock)
// set true to allow handleReceiveChain to send boolean to ValidChan
jsonflag = true
isValid = <-ValidChan
} else {
fmt.Println("No peers to send to, self-validating block.")
mutex.Lock()
pow := NewProofOfWork(&newBlock)
if pow.Validate() {
fmt.Println("Block is valid")
Blockchain = append(Blockchain, newBlock)
spew.Dump(Blockchain)
isValid = true
} else {
fmt.Println("Block not valid")
isValid = false
}
mutex.Unlock()
}
if isValid {
respondWithJSON(w, r, http.StatusCreated, newBlock)
}
// set to false to prevent data sent to channel
jsonflag = false
}
/* respondWithJSON writes a JSON text back to the web server */
func respondWithJSON(w http.ResponseWriter, r *http.Request, code int, payload interface{}) {
response, err := json.MarshalIndent(payload, "", " ")
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
w.Write([]byte("HTTP 500: Internal Server Error"))
return
}
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(code)
w.Write(response)
}