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server.go
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server.go
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package main
import (
"context"
"crypto/ecdsa"
"errors"
"fmt"
"log"
"math/big"
"strings"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/ethclient"
"github.com/ethereum/go-ethereum/params"
recaptcha "github.com/prestonvanloon/go-recaptcha"
faucetpb "github.com/prysmaticlabs/prysm/proto/faucet"
"github.com/prysmaticlabs/prysm/shared/roughtime"
"google.golang.org/grpc/metadata"
)
const ipLimit = 5
var fundingAmount *big.Int
var funded = make(map[string]bool)
var ipCounter = make(map[string]int)
var fundingLock sync.Mutex
var pruneDuration = time.Hour * 4
type faucetServer struct {
r recaptcha.Recaptcha
client *ethclient.Client
funder common.Address
pk *ecdsa.PrivateKey
minScore float64
}
func init() {
var ok bool
fundingAmount, ok = new(big.Int).SetString("32500000000000000000", 10)
if !ok {
log.Fatal("could not set funding amount")
}
}
func newFaucetServer(
r recaptcha.Recaptcha,
rpcPath string,
funderPrivateKey string,
minScore float64,
) *faucetServer {
client, err := ethclient.DialContext(context.Background(), rpcPath)
if err != nil {
panic(err)
}
pk, err := crypto.HexToECDSA(funderPrivateKey)
if err != nil {
panic(err)
}
funder := crypto.PubkeyToAddress(pk.PublicKey)
bal, err := client.BalanceAt(context.Background(), funder, nil)
if err != nil {
panic(err)
}
fmt.Printf("Funder is %s\n", funder.Hex())
fmt.Printf("Funder has %d\n", bal)
return &faucetServer{
r: r,
client: client,
funder: funder,
pk: pk,
minScore: minScore,
}
}
func (s *faucetServer) verifyRecaptcha(peer string, req *faucetpb.FundingRequest) error {
fmt.Printf("Sending captcha request for peer %s\n", peer)
rr, err := s.r.Check(peer, req.RecaptchaResponse)
if err != nil {
return err
}
if !rr.Success {
fmt.Printf("Unsuccessful recaptcha request. Error codes: %+v\n", rr.ErrorCodes)
return errors.New("failed")
}
if rr.Score < s.minScore {
return fmt.Errorf("recaptcha score too low (%f)", rr.Score)
}
if roughtime.Now().After(rr.ChallengeTS.Add(2 * time.Minute)) {
return errors.New("captcha challenge too old")
}
if rr.Action != req.WalletAddress {
return fmt.Errorf("action was %s, wanted %s", rr.Action, req.WalletAddress)
}
if !strings.HasSuffix(rr.Hostname, "prylabs.net") && !strings.HasSuffix(rr.Hostname, "prylabs.network") {
return fmt.Errorf("expected hostname (%s) to end in prylabs.net", rr.Hostname)
}
return nil
}
// RequestFunds from the ethereum 1.x faucet. Requires a valid captcha
// response.
func (s *faucetServer) RequestFunds(ctx context.Context, req *faucetpb.FundingRequest) (*faucetpb.FundingResponse, error) {
peer, err := s.getPeer(ctx)
if err != nil {
fmt.Printf("peer failure %v\n", err)
return &faucetpb.FundingResponse{Error: "peer error"}, nil
}
if err := s.verifyRecaptcha(peer, req); err != nil {
fmt.Printf("Recaptcha failure %v\n", err)
return &faucetpb.FundingResponse{Error: "recaptcha error"}, nil
}
fundingLock.Lock()
exceedPeerLimit := ipCounter[peer] >= ipLimit
if funded[req.WalletAddress] || exceedPeerLimit {
if exceedPeerLimit {
fmt.Printf("peer %s trying to get funded despite being over peer limit\n", peer)
}
fundingLock.Unlock()
return &faucetpb.FundingResponse{Error: "funded too recently"}, nil
}
funded[req.WalletAddress] = true
fundingLock.Unlock()
txHash, err := s.fundAndWait(common.HexToAddress(req.WalletAddress))
if err != nil {
return &faucetpb.FundingResponse{Error: fmt.Sprintf("Failed to send transaction %v", err)}, nil
}
fundingLock.Lock()
ipCounter[peer]++
fundingLock.Unlock()
fmt.Printf("Funded with TX %s\n", txHash)
return &faucetpb.FundingResponse{
Amount: fundingAmount.String(),
TransactionHash: txHash,
}, nil
}
func (s *faucetServer) fundAndWait(to common.Address) (string, error) {
nonce := uint64(0)
nonce, err := s.client.PendingNonceAt(context.Background(), s.funder)
if err != nil {
return "", err
}
tx := types.NewTransaction(nonce, to, fundingAmount, 40000, big.NewInt(1*params.GWei), nil /*data*/)
tx, err = types.SignTx(tx, types.NewEIP155Signer(big.NewInt(5)), s.pk)
if err != nil {
return "", err
}
if err := s.client.SendTransaction(context.Background(), tx); err != nil {
return "", err
}
// Wait for contract to mine
for pending := true; pending; _, pending, err = s.client.TransactionByHash(context.Background(), tx.Hash()) {
if err != nil {
log.Fatal(err)
}
time.Sleep(1 * time.Second)
}
return tx.Hash().Hex(), nil
}
func (s *faucetServer) getPeer(ctx context.Context) (string, error) {
md, ok := metadata.FromIncomingContext(ctx)
if !ok || len(md.Get("x-forwarded-for")) < 1 {
return "", errors.New("metadata not ok")
}
peer := md.Get("x-forwarded-for")[0]
return peer, nil
}
// reduce the counter for each ip every few hours.
func counterWatcher() {
ticker := time.NewTicker(pruneDuration)
for {
<-ticker.C
fundingLock.Lock()
for ip, ctr := range ipCounter {
if ctr == 0 {
continue
}
ipCounter[ip] = ctr - 1
}
fundingLock.Unlock()
}
}