// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package chequebook package wraps the 'chequebook' Ethereum smart contract.
//
// The functions in this package allow using chequebook for
// issuing, receiving, verifying cheques in ether; (auto)cashing cheques in ether
// as well as (auto)depositing ether to the chequebook contract.
package chequebook
//go:generate abigen --sol contract/chequebook.sol --pkg contract --out contract/chequebook.go
//go:generate go run ./gencode.go
import (
"bytes"
"crypto/ecdsa"
"encoding/json"
"fmt"
"io/ioutil"
"math/big"
"os"
"sync"
"time"
"github.com/ethereum/go-ethereum/accounts/abi/bind"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/contracts/chequebook/contract"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/swarm/services/swap/swap"
"golang.org/x/net/context"
)
// TODO(zelig): watch peer solvency and notify of bouncing cheques
// TODO(zelig): enable paying with cheque by signing off
// Some functionality require interacting with the blockchain:
// * setting current balance on peer's chequebook
// * sending the transaction to cash the cheque
// * depositing ether to the chequebook
// * watching incoming ether
var (
gasToCash = big.NewInt(2000000) // gas cost of a cash transaction using chequebook
// gasToDeploy = big.NewInt(3000000)
)
// Backend wraps all methods required for chequebook operation.
type Backend interface {
bind.ContractBackend
TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error)
BalanceAt(ctx context.Context, address common.Address, blockNum *big.Int) (*big.Int, error)
}
// Cheque represents a payment promise to a single beneficiary.
type Cheque struct {
Contract common.Address // address of chequebook, needed to avoid cross-contract submission
Beneficiary common.Address
Amount *big.Int // cumulative amount of all funds sent
Sig []byte // signature Sign(Keccak256(contract, beneficiary, amount), prvKey)
}
func (self *Cheque) String() string {
return fmt.Sprintf("contract: %s, beneficiary: %s, amount: %v, signature: %x", self.Contract.Hex(), self.Beneficiary.Hex(), self.Amount, self.Sig)
}
type Params struct {
ContractCode, ContractAbi string
}
var ContractParams = &Params{contract.ChequebookBin, contract.ChequebookABI}
// Chequebook can create and sign cheques from a single contract to multiple beneficiaries.
// It is the outgoing payment handler for peer to peer micropayments.
type Chequebook struct {
path string // path to chequebook file
prvKey *ecdsa.PrivateKey // private key to sign cheque with
lock sync.Mutex //
backend Backend // blockchain API
quit chan bool // when closed causes autodeposit to stop
owner common.Address // owner address (derived from pubkey)
contract *contract.Chequebook // abigen binding
session *contract.ChequebookSession // abigen binding with Tx Opts
// persisted fields
balance *big.Int // not synced with blockchain
contractAddr common.Address // contract address
sent map[common.Address]*big.Int //tallies for beneficiarys
txhash string // tx hash of last deposit tx
threshold *big.Int // threshold that triggers autodeposit if not nil
buffer *big.Int // buffer to keep on top of balance for fork protection
}
func (self *Chequebook) String() string {
return fmt.Sprintf("contract: %s, owner: %s, balance: %v, signer: %x", self.contractAddr.Hex(), self.owner.Hex(), self.balance, self.prvKey.PublicKey)
}
// NewChequebook creates a new Chequebook.
func NewChequebook(path string, contractAddr common.Address, prvKey *ecdsa.PrivateKey, backend Backend) (self *Chequebook, err error) {
balance := new(big.Int)
sent := make(map[common.Address]*big.Int)
chbook, err := contract.NewChequebook(contractAddr, backend)
if err != nil {
return nil, err
}
transactOpts := bind.NewKeyedTransactor(prvKey)
session := &contract.ChequebookSession{
Contract: chbook,
TransactOpts: *transactOpts,
}
self = &Chequebook{
prvKey: prvKey,
balance: balance,
contractAddr: contractAddr,
sent: sent,
path: path,
backend: backend,
owner: transactOpts.From,
contract: chbook,
session: session,
}
if (contractAddr != common.Address{}) {
self.setBalanceFromBlockChain()
log.Trace(fmt.Sprintf("new chequebook initialised from %s (owner: %v, balance: %s)", contractAddr.Hex(), self.owner.Hex(), self.balance.String()))
}
return
}
func (self *Chequebook) setBalanceFromBlockChain() {
balance, err := self.backend.BalanceAt(context.TODO(), self.contractAddr, nil)
if err != nil {
log.Error(fmt.Sprintf("can't get balance: %v", err))
} else {
self.balance.Set(balance)
}
}
// LoadChequebook loads a chequebook from disk (file path).
func LoadChequebook(path string, prvKey *ecdsa.PrivateKey, backend Backend, checkBalance bool) (self *Chequebook, err error) {
var data []byte
data, err = ioutil.ReadFile(path)
if err != nil {
return
}
self, _ = NewChequebook(path, common.Address{}, prvKey, backend)
err = json.Unmarshal(data, self)
if err != nil {
return nil, err
}
if checkBalance {
self.setBalanceFromBlockChain()
}
log.Trace(fmt.Sprintf("loaded chequebook (%s, owner: %v, balance: %v) initialised from %v", self.contractAddr.Hex(), self.owner.Hex(), self.balance, path))
return
}
// chequebookFile is the JSON representation of a chequebook.
type chequebookFile struct {
Balance string
Contract string
Owner string
Sent map[string]string
}
// UnmarshalJSON deserialises a chequebook.
func (self *Chequebook) UnmarshalJSON(data []byte) error {
var file chequebookFile
err := json.Unmarshal(data, &file)
if err != nil {
return err
}
_, ok := self.balance.SetString(file.Balance, 10)
if !ok {
return fmt.Errorf("cumulative amount sent: unable to convert string to big integer: %v", file.Balance)
}
self.contractAddr = common.HexToAddress(file.Contract)
for addr, sent := range file.Sent {
self.sent[common.HexToAddress(addr)], ok = new(big.Int).SetString(sent, 10)
if !ok {
return fmt.Errorf("beneficiary %v cumulative amount sent: unable to convert string to big integer: %v", addr, sent)
}
}
return nil
}
// MarshalJSON serialises a chequebook.
func (self *Chequebook) MarshalJSON() ([]byte, error) {
var file = &chequebookFile{
Balance: self.balance.String(),
Contract: self.contractAddr.Hex(),
Owner: self.owner.Hex(),
Sent: make(map[string]string),
}
for addr, sent := range self.sent {
file.Sent[addr.Hex()] = sent.String()
}
return json.Marshal(file)
}
// Save persists the chequebook on disk, remembering balance, contract address and
// cumulative amount of funds sent for each beneficiary.
func (self *Chequebook) Save() (err error) {
data, err := json.MarshalIndent(self, "", " ")
if err != nil {
return err
}
log.Trace(fmt.Sprintf("saving chequebook (%s) to %v", self.contractAddr.Hex(), self.path))
return ioutil.WriteFile(self.path, data, os.ModePerm)
}
// Stop quits the autodeposit go routine to terminate
func (self *Chequebook) Stop() {
defer self.lock.Unlock()
self.lock.Lock()
if self.quit != nil {
close(self.quit)
self.quit = nil
}
}
// Issue creates a cheque signed by the chequebook owner's private key. The
// signer commits to a contract (one that they own), a beneficiary and amount.
func (self *Chequebook) Issue(beneficiary common.Address, amount *big.Int) (ch *Cheque, err error) {
defer self.lock.Unlock()
self.lock.Lock()
if amount.Cmp(common.Big0) <= 0 {
return nil, fmt.Errorf("amount must be greater than zero (%v)", amount)
}
if self.balance.Cmp(amount) < 0 {
err = fmt.Errorf("insufficient funds to issue cheque for amount: %v. balance: %v", amount, self.balance)
} else {
var sig []byte
sent, found := self.sent[beneficiary]
if !found {
sent = new(big.Int)
self.sent[beneficiary] = sent
}
sum := new(big.Int).Set(sent)
sum.Add(sum, amount)
sig, err = crypto.Sign(sigHash(self.contractAddr, beneficiary, sum), self.prvKey)
if err == nil {
ch = &Cheque{
Contract: self.contractAddr,
Beneficiary: beneficiary,
Amount: sum,
Sig: sig,
}
sent.Set(sum)
self.balance.Sub(self.balance, amount) // subtract amount from balance
}
}
// auto deposit if threshold is set and balance is less then threshold
// note this is called even if issuing cheque fails
// so we reattempt depositing
if self.threshold != nil {
if self.balance.Cmp(self.threshold) < 0 {
send := new(big.Int).Sub(self.buffer, self.balance)
self.deposit(send)
}
}
return
}
// Cash is a convenience method to cash any cheque.
func (self *Chequebook) Cash(ch *Cheque) (txhash string, err error) {
return ch.Cash(self.session)
}
// data to sign: contract address, beneficiary, cumulative amount of funds ever sent
func sigHash(contract, beneficiary common.Address, sum *big.Int) []byte {
bigamount := sum.Bytes()
if len(bigamount) > 32 {
return nil
}
var amount32 [32]byte
copy(amount32[32-len(bigamount):32], bigamount)
input := append(contract.Bytes(), beneficiary.Bytes()...)
input = append(input, amount32[:]...)
return crypto.Keccak256(input)
}
// Balance returns the current balance of the chequebook.
func (self *Chequebook) Balance() *big.Int {
defer self.lock.Unlock()
self.lock.Lock()
return new(big.Int).Set(self.balance)
}
// Owner returns the owner account of the chequebook.
func (self *Chequebook) Owner() common.Address {
return self.owner
}
// Address returns the on-chain contract address of the chequebook.
func (self *Chequebook) Address() common.Address {
return self.contractAddr
}
// Deposit deposits money to the chequebook account.
func (self *Chequebook) Deposit(amount *big.Int) (string, error) {
defer self.lock.Unlock()
self.lock.Lock()
return self.deposit(amount)
}
// deposit deposits amount to the chequebook account.
// The caller must hold self.lock.
func (self *Chequebook) deposit(amount *big.Int) (string, error) {
// since the amount is variable here, we do not use sessions
depositTransactor := bind.NewKeyedTransactor(self.prvKey)
depositTransactor.Value = amount
chbookRaw := &contract.ChequebookRaw{Contract: self.contract}
tx, err := chbookRaw.Transfer(depositTransactor)
if err != nil {
log.Warn(fmt.Sprintf("error depositing %d wei to chequebook (%s, balance: %v, target: %v): %v", amount, self.contractAddr.Hex(), self.balance, self.buffer, err))
return "", err
}
// assume that transaction is actually successful, we add the amount to balance right away
self.balance.Add(self.balance, amount)
log.Trace(fmt.Sprintf("deposited %d wei to chequebook (%s, balance: %v, target: %v)", amount, self.contractAddr.Hex(), self.balance, self.buffer))
return tx.Hash().Hex(), nil
}
// AutoDeposit (re)sets interval time and amount which triggers sending funds to the
// chequebook. Contract backend needs to be set if threshold is not less than buffer, then
// deposit will be triggered on every new cheque issued.
func (self *Chequebook) AutoDeposit(interval time.Duration, threshold, buffer *big.Int) {
defer self.lock.Unlock()
self.lock.Lock()
self.threshold = threshold
self.buffer = buffer
self.autoDeposit(interval)
}
// autoDeposit starts a goroutine that periodically sends funds to the chequebook
// contract caller holds the lock the go routine terminates if Chequebook.quit is closed.
func (self *Chequebook) autoDeposit(interval time.Duration) {
if self.quit != nil {
close(self.quit)
self.quit = nil
}
// if threshold >= balance autodeposit after every cheque issued
if interval == time.Duration(0) || self.threshold != nil && self.buffer != nil && self.threshold.Cmp(self.buffer) >= 0 {
return
}
ticker := time.NewTicker(interval)
self.quit = make(chan bool)
quit := self.quit
go func() {
FOR:
for {
select {
case <-quit:
break FOR
case <-ticker.C:
self.lock.Lock()
if self.balance.Cmp(self.buffer) < 0 {
amount := new(big.Int).Sub(self.buffer, self.balance)
txhash, err := self.deposit(amount)
if err == nil {
self.txhash = txhash
}
}
self.lock.Unlock()
}
}
}()
return
}
// Outbox can issue cheques from a single contract to a single beneficiary.
type Outbox struct {
chequeBook *Chequebook
beneficiary common.Address
}
// NewOutbox creates an outbox.
func NewOutbox(chbook *Chequebook, beneficiary common.Address) *Outbox {
return &Outbox{chbook, beneficiary}
}
// Issue creates cheque.
func (self *Outbox) Issue(amount *big.Int) (swap.Promise, error) {
return self.chequeBook.Issue(self.beneficiary, amount)
}
// AutoDeposit enables auto-deposits on the underlying chequebook.
func (self *Outbox) AutoDeposit(interval time.Duration, threshold, buffer *big.Int) {
self.chequeBook.AutoDeposit(interval, threshold, buffer)
}
// Stop helps satisfy the swap.OutPayment interface.
func (self *Outbox) Stop() {}
// String implements fmt.Stringer.
func (self *Outbox) String() string {
return fmt.Sprintf("chequebook: %v, beneficiary: %s, balance: %v", self.chequeBook.Address().Hex(), self.beneficiary.Hex(), self.chequeBook.Balance())
}
// Inbox can deposit, verify and cash cheques from a single contract to a single
// beneficiary. It is the incoming payment handler for peer to peer micropayments.
type Inbox struct {
lock sync.Mutex
contract common.Address // peer's chequebook contract
beneficiary common.Address // local peer's receiving address
sender common.Address // local peer's address to send cashing tx from
signer *ecdsa.PublicKey // peer's public key
txhash string // tx hash of last cashing tx
abigen bind.ContractBackend // blockchain API
session *contract.ChequebookSession // abi contract backend with tx opts
quit chan bool // when closed causes autocash to stop
maxUncashed *big.Int // threshold that triggers autocashing
cashed *big.Int // cumulative amount cashed
cheque *Cheque // last cheque, nil if none yet received
}
// NewInbox creates an Inbox. An Inboxes is not persisted, the cumulative sum is updated
// from blockchain when first cheque is received.
func NewInbox(prvKey *ecdsa.PrivateKey, contractAddr, beneficiary common.Address, signer *ecdsa.PublicKey, abigen bind.ContractBackend) (self *Inbox, err error) {
if signer == nil {
return nil, fmt.Errorf("signer is null")
}
chbook, err := contract.NewChequebook(contractAddr, abigen)
if err != nil {
return nil, err
}
transactOpts := bind.NewKeyedTransactor(prvKey)
transactOpts.GasLimit = gasToCash
session := &contract.ChequebookSession{
Contract: chbook,
TransactOpts: *transactOpts,
}
sender := transactOpts.From
self = &Inbox{
contract: contractAddr,
beneficiary: beneficiary,
sender: sender,
signer: signer,
session: session,
cashed: new(big.Int).Set(common.Big0),
}
log.Trace(fmt.Sprintf("initialised inbox (%s -> %s) expected signer: %x", self.contract.Hex(), self.beneficiary.Hex(), crypto.FromECDSAPub(signer)))
return
}
func (self *Inbox) String() string {
return fmt.Sprintf("chequebook: %v, beneficiary: %s, balance: %v", self.contract.Hex(), self.beneficiary.Hex(), self.cheque.Amount)
}
// Stop quits the autocash goroutine.
func (self *Inbox) Stop() {
defer self.lock.Unlock()
self.lock.Lock()
if self.quit != nil {
close(self.quit)
self.quit = nil
}
}
// Cash attempts to cash the current cheque.
func (self *Inbox) Cash() (txhash string, err error) {
if self.cheque != nil {
txhash, err = self.cheque.Cash(self.session)
log.Trace(fmt.Sprintf("cashing cheque (total: %v) on chequebook (%s) sending to %v", self.cheque.Amount, self.contract.Hex(), self.beneficiary.Hex()))
self.cashed = self.cheque.Amount
}
return
}
// AutoCash (re)sets maximum time and amount which triggers cashing of the last uncashed
// cheque if maxUncashed is set to 0, then autocash on receipt.
func (self *Inbox) AutoCash(cashInterval time.Duration, maxUncashed *big.Int) {
defer self.lock.Unlock()
self.lock.Lock()
self.maxUncashed = maxUncashed
self.autoCash(cashInterval)
}
// autoCash starts a loop that periodically clears the last check
// if the peer is trusted. Clearing period could be 24h or a week.
//
// The caller must hold self.lock.
func (self *Inbox) autoCash(cashInterval time.Duration) {
if self.quit != nil {
close(self.quit)
self.quit = nil
}
// if maxUncashed is set to 0, then autocash on receipt
if cashInterval == time.Duration(0) || self.maxUncashed != nil && self.maxUncashed.Cmp(common.Big0) == 0 {
return
}
ticker := time.NewTicker(cashInterval)
self.quit = make(chan bool)
quit := self.quit
go func() {
FOR:
for {
select {
case <-quit:
break FOR
case <-ticker.C:
self.lock.Lock()
if self.cheque != nil && self.cheque.Amount.Cmp(self.cashed) != 0 {
txhash, err := self.Cash()
if err == nil {
self.txhash = txhash
}
}
self.lock.Unlock()
}
}
}()
return
}
// Receive is called to deposit the latest cheque to the incoming Inbox.
// The given promise must be a *Cheque.
func (self *Inbox) Receive(promise swap.Promise) (*big.Int, error) {
ch := promise.(*Cheque)
defer self.lock.Unlock()
self.lock.Lock()
var sum *big.Int
if self.cheque == nil {
// the sum is checked against the blockchain once a check is received
tally, err := self.session.Sent(self.beneficiary)
if err != nil {
return nil, fmt.Errorf("inbox: error calling backend to set amount: %v", err)
}
sum = tally
} else {
sum = self.cheque.Amount
}
amount, err := ch.Verify(self.signer, self.contract, self.beneficiary, sum)
var uncashed *big.Int
if err == nil {
self.cheque = ch
if self.maxUncashed != nil {
uncashed = new(big.Int).Sub(ch.Amount, self.cashed)
if self.maxUncashed.Cmp(uncashed) < 0 {
self.Cash()
}
}
log.Trace(fmt.Sprintf("received cheque of %v wei in inbox (%s, uncashed: %v)", amount, self.contract.Hex(), uncashed))
}
return amount, err
}
// Verify verifies cheque for signer, contract, beneficiary, amount, valid signature.
func (self *Cheque) Verify(signerKey *ecdsa.PublicKey, contract, beneficiary common.Address, sum *big.Int) (*big.Int, error) {
log.Trace(fmt.Sprintf("verify cheque: %v - sum: %v", self, sum))
if sum == nil {
return nil, fmt.Errorf("invalid amount")
}
if self.Beneficiary != beneficiary {
return nil, fmt.Errorf("beneficiary mismatch: %v != %v", self.Beneficiary.Hex(), beneficiary.Hex())
}
if self.Contract != contract {
return nil, fmt.Errorf("contract mismatch: %v != %v", self.Contract.Hex(), contract.Hex())
}
amount := new(big.Int).Set(self.Amount)
if sum != nil {
amount.Sub(amount, sum)
if amount.Cmp(common.Big0) <= 0 {
return nil, fmt.Errorf("incorrect amount: %v <= 0", amount)
}
}
pubKey, err := crypto.SigToPub(sigHash(self.Contract, beneficiary, self.Amount), self.Sig)
if err != nil {
return nil, fmt.Errorf("invalid signature: %v", err)
}
if !bytes.Equal(crypto.FromECDSAPub(pubKey), crypto.FromECDSAPub(signerKey)) {
return nil, fmt.Errorf("signer mismatch: %x != %x", crypto.FromECDSAPub(pubKey), crypto.FromECDSAPub(signerKey))
}
return amount, nil
}
// v/r/s representation of signature
func sig2vrs(sig []byte) (v byte, r, s [32]byte) {
v = sig[64] + 27
copy(r[:], sig[:32])
copy(s[:], sig[32:64])
return
}
// Cash cashes the cheque by sending an Ethereum transaction.
func (self *Cheque) Cash(session *contract.ChequebookSession) (string, error) {
v, r, s := sig2vrs(self.Sig)
tx, err := session.Cash(self.Beneficiary, self.Amount, v, r, s)
if err != nil {
return "", err
}
return tx.Hash().Hex(), nil
}
// ValidateCode checks that the on-chain code at address matches the expected chequebook
// contract code. This is used to detect suicided chequebooks.
func ValidateCode(ctx context.Context, b Backend, address common.Address) (ok bool, err error) {
code, err := b.CodeAt(ctx, address, nil)
if err != nil {
return false, err
}
return bytes.Equal(code, common.FromHex(contract.ContractDeployedCode)), nil
}
