path: root/cmd/faucet/faucet.go

// Copyright 2017 The go-ethereum Authors
// This file is part of go-ethereum.
//
// go-ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// go-ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.

// faucet is a Ether faucet backed by a light client.
package main

//go:generate go-bindata -nometadata -o website.go faucet.html

import (
    "bytes"
    "context"
    "encoding/json"
    "flag"
    "fmt"
    "html/template"
    "io/ioutil"
    "math"
    "math/big"
    "net/http"
    "net/url"
    "os"
    "path/filepath"
    "strconv"
    "strings"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/accounts"
    "github.com/ethereum/go-ethereum/accounts/keystore"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/eth"
    "github.com/ethereum/go-ethereum/eth/downloader"
    "github.com/ethereum/go-ethereum/ethclient"
    "github.com/ethereum/go-ethereum/ethstats"
    "github.com/ethereum/go-ethereum/les"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/node"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/p2p/discover"
    "github.com/ethereum/go-ethereum/p2p/discv5"
    "github.com/ethereum/go-ethereum/p2p/nat"
    "github.com/ethereum/go-ethereum/params"
    "golang.org/x/net/websocket"
)

var (
    genesisFlag = flag.String("genesis", "", "Genesis json file to seed the chain with")
    apiPortFlag = flag.Int("apiport", 8080, "Listener port for the HTTP API connection")
    ethPortFlag = flag.Int("ethport", 30303, "Listener port for the devp2p connection")
    bootFlag    = flag.String("bootnodes", "", "Comma separated bootnode enode URLs to seed with")
    netFlag     = flag.Uint64("network", 0, "Network ID to use for the Ethereum protocol")
    statsFlag   = flag.String("ethstats", "", "Ethstats network monitoring auth string")

    netnameFlag = flag.String("faucet.name", "", "Network name to assign to the faucet")
    payoutFlag  = flag.Int("faucet.amount", 1, "Number of Ethers to pay out per user request")
    minutesFlag = flag.Int("faucet.minutes", 1440, "Number of minutes to wait between funding rounds")
    tiersFlag   = flag.Int("faucet.tiers", 3, "Number of funding tiers to enable (x3 time, x2.5 funds)")

    accJSONFlag = flag.String("account.json", "", "Key json file to fund user requests with")
    accPassFlag = flag.String("account.pass", "", "Decryption password to access faucet funds")

    githubUser  = flag.String("github.user", "", "GitHub user to authenticate with for Gist access")
    githubToken = flag.String("github.token", "", "GitHub personal token to access Gists with")

    captchaToken  = flag.String("captcha.token", "", "Recaptcha site key to authenticate client side")
    captchaSecret = flag.String("captcha.secret", "", "Recaptcha secret key to authenticate server side")

    logFlag = flag.Int("loglevel", 3, "Log level to use for Ethereum and the faucet")
)

var (
    ether = new(big.Int).Exp(big.NewInt(10), big.NewInt(18), nil)
)

func main() {
    // Parse the flags and set up the logger to print everything requested
    flag.Parse()
    log.Root().SetHandler(log.LvlFilterHandler(log.Lvl(*logFlag), log.StreamHandler(os.Stderr, log.TerminalFormat(true))))

    // Construct the payout tiers
    amounts := make([]string, *tiersFlag)
    periods := make([]string, *tiersFlag)
    for i := 0; i < *tiersFlag; i++ {
        // Calculate the amount for the next tier and format it
        amount := float64(*payoutFlag) * math.Pow(2.5, float64(i))
        amounts[i] = fmt.Sprintf("%s Ethers", strconv.FormatFloat(amount, 'f', -1, 64))
        if amount == 1 {
            amounts[i] = strings.TrimSuffix(amounts[i], "s")
        }
        // Calculate the period for the next tier and format it
        period := *minutesFlag * int(math.Pow(3, float64(i)))
        periods[i] = fmt.Sprintf("%d mins", period)
        if period%60 == 0 {
            period /= 60
            periods[i] = fmt.Sprintf("%d hours", period)

            if period%24 == 0 {
                period /= 24
                periods[i] = fmt.Sprintf("%d days", period)
            }
        }
        if period == 1 {
            periods[i] = strings.TrimSuffix(periods[i], "s")
        }
    }
    // Load up and render the faucet website
    tmpl, err := Asset("faucet.html")
    if err != nil {
        log.Crit("Failed to load the faucet template", "err", err)
    }
    website := new(bytes.Buffer)
    err = template.Must(template.New("").Parse(string(tmpl))).Execute(website, map[string]interface{}{
        "Network":   *netnameFlag,
        "Amounts":   amounts,
        "Periods":   periods,
        "Recaptcha": *captchaToken,
    })
    if err != nil {
        log.Crit("Failed to render the faucet template", "err", err)
    }
    // Load and parse the genesis block requested by the user
    blob, err := ioutil.ReadFile(*genesisFlag)
    if err != nil {
        log.Crit("Failed to read genesis block contents", "genesis", *genesisFlag, "err", err)
    }
    genesis := new(core.Genesis)
    if err = json.Unmarshal(blob, genesis); err != nil {
        log.Crit("Failed to parse genesis block json", "err", err)
    }
    // Convert the bootnodes to internal enode representations
    var enodes []*discv5.Node
    for _, boot := range strings.Split(*bootFlag, ",") {
        if url, err := discv5.ParseNode(boot); err == nil {
            enodes = append(enodes, url)
        } else {
            log.Error("Failed to parse bootnode URL", "url", boot, "err", err)
        }
    }
    // Load up the account key and decrypt its password
    if blob, err = ioutil.ReadFile(*accPassFlag); err != nil {
        log.Crit("Failed to read account password contents", "file", *accPassFlag, "err", err)
    }
    pass := string(blob)

    ks := keystore.NewKeyStore(filepath.Join(os.Getenv("HOME"), ".faucet", "keys"), keystore.StandardScryptN, keystore.StandardScryptP)
    if blob, err = ioutil.ReadFile(*accJSONFlag); err != nil {
        log.Crit("Failed to read account key contents", "file", *accJSONFlag, "err", err)
    }
    acc, err := ks.Import(blob, pass, pass)
    if err != nil {
        log.Crit("Failed to import faucet signer account", "err", err)
    }
    ks.Unlock(acc, pass)

    // Assemble and start the faucet light service
    faucet, err := newFaucet(genesis, *ethPortFlag, enodes, *netFlag, *statsFlag, ks, website.Bytes())
    if err != nil {
        log.Crit("Failed to start faucet", "err", err)
    }
    defer faucet.close()

    if err := faucet.listenAndServe(*apiPortFlag); err != nil {
        log.Crit("Failed to launch faucet API", "err", err)
    }
}

// request represents an accepted funding request.
type request struct {
    Username string             `json:"username"` // GitHub user for displaying an avatar
    Account  common.Address     `json:"account"`  // Ethereum address being funded
    Time     time.Time          `json:"time"`     // Timestamp when te request was accepted
    Tx       *types.Transaction `json:"tx"`       // Transaction funding the account
}

// faucet represents a crypto faucet backed by an Ethereum light client.
type faucet struct {
    config *params.ChainConfig // Chain configurations for signing
    stack  *node.Node          // Ethereum protocol stack
    client *ethclient.Client   // Client connection to the Ethereum chain
    index  []byte              // Index page to serve up on the web

    keystore *keystore.KeyStore // Keystore containing the single signer
    account  accounts.Account   // Account funding user faucet requests
    nonce    uint64             // Current pending nonce of the faucet
    price    *big.Int           // Current gas price to issue funds with

    conns    []*websocket.Conn    // Currently live websocket connections
    timeouts map[string]time.Time // History of users and their funding timeouts
    reqs     []*request           // Currently pending funding requests
    update   chan struct{}        // Channel to signal request updates

    lock sync.RWMutex // Lock protecting the faucet's internals
}

func newFaucet(genesis *core.Genesis, port int, enodes []*discv5.Node, network uint64, stats string, ks *keystore.KeyStore, index []byte) (*faucet, error) {
    // Assemble the raw devp2p protocol stack
    stack, err := node.New(&node.Config{
        Name:    "geth",
        Version: params.Version,
        DataDir: filepath.Join(os.Getenv("HOME"), ".faucet"),
        P2P: p2p.Config{
            NAT:              nat.Any(),
            NoDiscovery:      true,
            DiscoveryV5:      true,
            ListenAddr:       fmt.Sprintf(":%d", port),
            DiscoveryV5Addr:  fmt.Sprintf(":%d", port+1),
            MaxPeers:         25,
            BootstrapNodesV5: enodes,
        },
    })
    if err != nil {
        return nil, err
    }
    // Assemble the Ethereum light client protocol
    if err := stack.Register(func(ctx *node.ServiceContext) (node.Service, error) {
        cfg := eth.DefaultConfig
        cfg.SyncMode = downloader.LightSync
        cfg.NetworkId = network
        cfg.Genesis = genesis
        return les.New(ctx, &cfg)
    }); err != nil {
        return nil, err
    }
    // Assemble the ethstats monitoring and reporting service'
    if stats != "" {
        if err := stack.Register(func(ctx *node.ServiceContext) (node.Service, error) {
            var serv *les.LightEthereum
            ctx.Service(&serv)
            return ethstats.New(stats, nil, serv)
        }); err != nil {
            return nil, err
        }
    }
    // Boot up the client and ensure it connects to bootnodes
    if err := stack.Start(); err != nil {
        return nil, err
    }
    for _, boot := range enodes {
        old, _ := discover.ParseNode(boot.String())
        stack.Server().AddPeer(old)
    }
    // Attach to the client and retrieve and interesting metadatas
    api, err := stack.Attach()
    if err != nil {
        stack.Stop()
        return nil, err
    }
    client := ethclient.NewClient(api)

    return &faucet{
        config:   genesis.Config,
        stack:    stack,
        client:   client,
        index:    index,
        keystore: ks,
        account:  ks.Accounts()[0],
        timeouts: make(map[string]time.Time),
        update:   make(chan struct{}, 1),
    }, nil
}

// close terminates the Ethereum connection and tears down the faucet.
func (f *faucet) close() error {
    return f.stack.Stop()
}

// listenAndServe registers the HTTP handlers for the faucet and boots it up
// for service user funding requests.
func (f *faucet) listenAndServe(port int) error {
    go f.loop()

    http.HandleFunc("/", f.webHandler)
    http.Handle("/api", websocket.Handler(f.apiHandler))

    return http.ListenAndServe(fmt.Sprintf(":%d", port), nil)
}

// webHandler handles all non-api requests, simply flattening and returning the
// faucet website.
func (f *faucet) webHandler(w http.ResponseWriter, r *http.Request) {
    w.Write(f.index)
}

// apiHandler handles requests for Ether grants and transaction statuses.
func (f *faucet) apiHandler(conn *websocket.Conn) {
    // Start tracking the connection and drop at the end
    f.lock.Lock()
    f.conns = append(f.conns, conn)
    f.lock.Unlock()

    defer func() {
        f.lock.Lock()
        for i, c := range f.conns {
            if c == conn {
                f.conns = append(f.conns[:i], f.conns[i+1:]...)
                break
            }
        }
        f.lock.Unlock()
    }()
    // Send a few initial stats to the client
    balance, _ := f.client.BalanceAt(context.Background(), f.account.Address, nil)
    nonce, _ := f.client.NonceAt(context.Background(), f.account.Address, nil)

    websocket.JSON.Send(conn, map[string]interface{}{
        "funds":    balance.Div(balance, ether),
        "funded":   nonce,
        "peers":    f.stack.Server().PeerCount(),
        "requests": f.reqs,
    })
    // Send the initial block to the client
    ctx, cancel := context.WithTimeout(context.Background(), time.Second)
    header, err := f.client.HeaderByNumber(ctx, nil)
    cancel()

    if err != nil {
        log.Error("Failed to retrieve latest header", "err", err)
    } else {
        websocket.JSON.Send(conn, header)
    }
    // Keep reading requests from the websocket until the connection breaks
    for {
        // Fetch the next funding request and validate against github
        var msg struct {
            URL     string `json:"url"`
            Tier    uint   `json:"tier"`
            Captcha string `json:"captcha"`
        }
        if err := websocket.JSON.Receive(conn, &msg); err != nil {
            return
        }
        if !strings.HasPrefix(msg.URL, "https://gist.github.com/") {
            websocket.JSON.Send(conn, map[string]string{"error": "URL doesn't link to GitHub Gists"})
            continue
        }
        if msg.Tier >= uint(*tiersFlag) {
            websocket.JSON.Send(conn, map[string]string{"error": "Invalid funding tier requested"})
            continue
        }
        log.Info("Faucet funds requested", "gist", msg.URL, "tier", msg.Tier)

        // If captcha verifications are enabled, make sure we're not dealing with a robot
        if *captchaToken != "" {
            form := url.Values{}
            form.Add("secret", *captchaSecret)
            form.Add("response", msg.Captcha)

            res, err := http.PostForm("https://www.google.com/recaptcha/api/siteverify", form)
            if err != nil {
                websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
                continue
            }
            var result struct {
                Success bool            `json:"success"`
                Errors  json.RawMessage `json:"error-codes"`
            }
            err = json.NewDecoder(res.Body).Decode(&result)
            res.Body.Close()
            if err != nil {
                websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
                continue
            }
            if !result.Success {
                log.Warn("Captcha verification failed", "err", string(result.Errors))
                websocket.JSON.Send(conn, map[string]string{"error": "Beep-bop, you're a robot!"})
                continue
            }
        }
        // Retrieve the gist from the GitHub Gist APIs
        parts := strings.Split(msg.URL, "/")
        req, _ := http.NewRequest("GET", "https://api.github.com/gists/"+parts[len(parts)-1], nil)
        if *githubUser != "" {
            req.SetBasicAuth(*githubUser, *githubToken)
        }
        res, err := http.DefaultClient.Do(req)
        if err != nil {
            websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
            continue
        }
        var gist struct {
            Owner struct {
                Login string `json:"login"`
            } `json:"owner"`
            Files map[string]struct {
                Content string `json:"content"`
            } `json:"files"`
        }
        err = json.NewDecoder(res.Body).Decode(&gist)
        res.Body.Close()
        if err != nil {
            websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
            continue
        }
        if gist.Owner.Login == "" {
            websocket.JSON.Send(conn, map[string]string{"error": "Anonymous Gists not allowed"})
            continue
        }
        // Iterate over all the files and look for Ethereum addresses
        var address common.Address
        for _, file := range gist.Files {
            content := strings.TrimSpace(file.Content)
            if len(content) == 2+common.AddressLength*2 {
                address = common.HexToAddress(content)
            }
        }
        if address == (common.Address{}) {
            websocket.JSON.Send(conn, map[string]string{"error": "No Ethereum address found to fund"})
            continue
        }
        // Validate the user's existence since the API is unhelpful here
        if res, err = http.Head("https://github.com/" + gist.Owner.Login); err != nil {
            websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
            continue
        }
        res.Body.Close()

        if res.StatusCode != 200 {
            websocket.JSON.Send(conn, map[string]string{"error": "Invalid user... boom!"})
            continue
        }
        // Ensure the user didn't request funds too recently
        f.lock.Lock()
        var (
            fund    bool
            timeout time.Time
        )
        if timeout = f.timeouts[gist.Owner.Login]; time.Now().After(timeout) {
            // User wasn't funded recently, create the funding transaction
            amount := new(big.Int).Mul(big.NewInt(int64(*payoutFlag)), ether)
            amount = new(big.Int).Mul(amount, new(big.Int).Exp(big.NewInt(5), big.NewInt(int64(msg.Tier)), nil))
            amount = new(big.Int).Div(amount, new(big.Int).Exp(big.NewInt(2), big.NewInt(int64(msg.Tier)), nil))

            tx := types.NewTransaction(f.nonce+uint64(len(f.reqs)), address, amount, big.NewInt(21000), f.price, nil)
            signed, err := f.keystore.SignTx(f.account, tx, f.config.ChainId)
            if err != nil {
                websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
                f.lock.Unlock()
                continue
            }
            // Submit the transaction and mark as funded if successful
            if err := f.client.SendTransaction(context.Background(), signed); err != nil {
                websocket.JSON.Send(conn, map[string]string{"error": err.Error()})
                f.lock.Unlock()
                continue
            }
            f.reqs = append(f.reqs, &request{
                Username: gist.Owner.Login,
                Account:  address,
                Time:     time.Now(),
                Tx:       signed,
            })
            f.timeouts[gist.Owner.Login] = time.Now().Add(time.Duration(*minutesFlag*int(math.Pow(3, float64(msg.Tier)))) * time.Minute)
            fund = true
        }
        f.lock.Unlock()

        // Send an error if too frequent funding, othewise a success
        if !fund {
            websocket.JSON.Send(conn, map[string]string{"error": fmt.Sprintf("%s left until next allowance", common.PrettyDuration(timeout.Sub(time.Now())))})
            continue
        }
        websocket.JSON.Send(conn, map[string]string{"success": fmt.Sprintf("Funding request accepted for %s into %s", gist.Owner.Login, address.Hex())})
        select {
        case f.update <- struct{}{}:
        default:
        }
    }
}

// loop keeps waiting for interesting events and pushes them out to connected
// websockets.
func (f *faucet) loop() {
    // Wait for chain events and push them to clients
    heads := make(chan *types.Header, 16)
    sub, err := f.client.SubscribeNewHead(context.Background(), heads)
    if err != nil {
        log.Crit("Failed to subscribe to head events", "err", err)
    }
    defer sub.Unsubscribe()

    for {
        select {
        case head := <-heads:
            // New chain head arrived, query the current stats and stream to clients
            balance, _ := f.client.BalanceAt(context.Background(), f.account.Address, nil)
            balance = new(big.Int).Div(balance, ether)

            price, _ := f.client.SuggestGasPrice(context.Background())
            nonce, _ := f.client.NonceAt(context.Background(), f.account.Address, nil)

            f.lock.Lock()
            f.price, f.nonce = price, nonce
            for len(f.reqs) > 0 && f.reqs[0].Tx.Nonce() < f.nonce {
                f.reqs = f.reqs[1:]
            }
            f.lock.Unlock()

            f.lock.RLock()
            for _, conn := range f.conns {
                if err := websocket.JSON.Send(conn, map[string]interface{}{
                    "funds":    balance,
                    "funded":   f.nonce,
                    "peers":    f.stack.Server().PeerCount(),
                    "requests": f.reqs,
                }); err != nil {
                    log.Warn("Failed to send stats to client", "err", err)
                    conn.Close()
                    continue
                }
                if err := websocket.JSON.Send(conn, head); err != nil {
                    log.Warn("Failed to send header to client", "err", err)
                    conn.Close()
                }
            }
            f.lock.RUnlock()

        case <-f.update:
            // Pending requests updated, stream to clients
            f.lock.RLock()
            for _, conn := range f.conns {
                if err := websocket.JSON.Send(conn, map[string]interface{}{"requests": f.reqs}); err != nil {
                    log.Warn("Failed to send requests to client", "err", err)
                    conn.Close()
                }
            }
            f.lock.RUnlock()
        }
    }
}