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send.go
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send.go
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package send
import (
"bytes"
"encoding/hex"
"fmt"
"github.com/btcsuite/btcd/wire"
"github.com/pkg/errors"
"github.com/rhavar/bustapay/rpc-client"
"github.com/rhavar/bustapay/util"
"io/ioutil"
"net/http"
)
func Send(address string, url string, amount int64) error {
util.VerboseLog("Sending ", amount, " satoshis to ", address, " via url ", url)
rpcClient, err := rpc_client.NewRpcClient()
if err != nil {
return err
}
defer rpcClient.Shutdown()
// Step 1. Create a transaction with correct output
unfunded, err := rpcClient.CreateRawTransaction(address, amount)
if err != nil {
return err
}
util.VerboseLog("Created unfunded transaction: ", unfunded)
// Step 2. Run coin selection, and add change (if applicable)
funded, err := rpcClient.FundRawTransaction(unfunded)
if err != nil {
return err
}
util.VerboseLog("Funded transaction: ", util.HexifyTransaction(funded))
// Step 3. Sign the transaction
template, _, err := rpcClient.SignRawTransactionWithWallet(funded)
if err != nil {
return err
}
util.VerboseLog("Template transaction: ", util.HexifyTransaction(template))
// Step 4. Send transaction to receiver
partial, err := httpPost(template, url)
if err != nil {
return err
}
util.VerboseLog("Got partial transaction back: ", util.HexifyTransaction(partial))
// Step 5. Validate the receiver didn't give us anything funny
err = validate(template, partial)
if err != nil {
return err
}
// Step 6. sign the partial transaction
final, _, err := rpcClient.SignRawTransactionWithWallet(partial)
if err != nil {
return err
}
util.VerboseLog("Final transaction: ", util.HexifyTransaction(final))
// Step 7. broadcast the raw transaction
_, err = rpcClient.SendRawTransaction(final)
if err != nil {
return err
}
util.VerboseLog("Broadcasted final transaction")
fmt.Println(final.TxHash())
return nil
}
func httpPost(tx *wire.MsgTx, url string) (*wire.MsgTx, error) {
byteBuffer := bytes.Buffer{}
if err := tx.Serialize(&byteBuffer); err != nil {
return nil, errors.WithStack(err)
}
util.VerboseLog("HTTP POSTing template transaction to ", url)
response, err := http.Post(url, "application/binary", &byteBuffer)
if err != nil {
return nil, errors.WithStack(err)
}
if response.StatusCode != 200 {
util.VerboseLog("Got http status code: ", response.StatusCode)
body, err := ioutil.ReadAll(response.Body)
if err != nil {
return nil, errors.WithStack(err)
}
util.VerboseLog("Http response body: ", string(body))
return nil, errors.New("got http error from server")
}
if err != nil {
return nil, errors.WithStack(err)
}
var msgTx wire.MsgTx
if err := msgTx.Deserialize(response.Body); err != nil {
return nil, errors.WithStack(err)
}
return &msgTx, nil
}
func validate(template *wire.MsgTx, partial *wire.MsgTx) error {
if template.LockTime != partial.LockTime {
return errors.New("lock time changed")
}
if template.Version != partial.Version {
return errors.New("version changed")
}
if len(template.TxOut) != len(partial.TxOut) {
return errors.New("number of outputs changed")
}
if len(partial.TxIn) <= len(template.TxIn) {
return errors.New("partial transaction should add inputs")
}
// validate the txins
usedContributedInputs := make(map[wire.OutPoint] struct{}) // What inputs did the receiver contribute
usedTemplateInputs := make(map[wire.OutPoint] struct{}) // Which have we seen
templateTxIns := make(map[wire.OutPoint]*wire.TxIn)
for _, txIn := range template.TxIn {
templateTxIns[txIn.PreviousOutPoint] = txIn
}
util.Assert(len(templateTxIns) == len(template.TxIn))
for _, txIn := range partial.TxIn {
templateTxIn, contains := templateTxIns[txIn.PreviousOutPoint]
if contains {
if templateTxIn.Sequence != txIn.Sequence {
return errors.New("input sequence has been changed")
}
if !bytes.Equal(templateTxIn.SignatureScript, txIn.SignatureScript) {
return errors.New("input sig script has been changed")
}
if len(txIn.Witness) != 0 {
return errors.New("input witness has not been cleared")
}
usedTemplateInputs[txIn.PreviousOutPoint] = struct{}{}
} else {
// No need to validate, (if it's invalid, the transaction won't propagate..)
// but we can sanity check that it has witnesses
if len(txIn.Witness) == 0 {
return errors.New("found contributed input, but without witness")
}
usedContributedInputs[txIn.PreviousOutPoint] = struct{}{}
}
}
if len(usedTemplateInputs) != len(template.TxIn) {
return errors.New("partial transaction did contain all original txins")
}
if len(usedContributedInputs) + len(usedTemplateInputs) != len(partial.TxIn) {
return errors.New("partial transaction contained dupe inputs")
}
originalTxOuts := make(map[string]*wire.TxOut)
for _, txOut := range template.TxOut {
originalTxOuts[hex.EncodeToString(txOut.PkScript)] = txOut
}
for _, txOut := range partial.TxOut {
pkScriptHex := hex.EncodeToString(txOut.PkScript)
original, contains := originalTxOuts[pkScriptHex]
if !contains {
return errors.New("partial transaction has output that original didn't")
}
// Check if this is the changed output
if txOut.Value < original.Value {
return errors.New("an output decreased. wtf?")
}
delete(originalTxOuts, pkScriptHex)
}
util.Assert(len(originalTxOuts) == 0)
return nil
}