network: Adds HashTransaction helper

CHANGELOG.md

@@ -0,0 +1,17 @@
+# Changelog
+
+All notable changes to this project will be documented in this
+file. This project adheres to [Semantic Versioning](http:https://semver.org/).
+
+As this project is pre 1.0, breaking changes may happen for minor version
+bumps. A breaking change will get clearly notified in this log.
+
+NOTE: this changelog represents the changes that are associated with the library code in this repo (rather than the tools or services in this repo). 
+
+## [Unreleased]
+
+### Added
+
+- network: Added the `HashTransaction` helper func to get the hash of a transaction targetted to a specific stellar network.
+
+[Unreleased]: https://github.com/stellar/go/commits/master

build/transaction.go

@@ -1,12 +1,10 @@
 package build
 
 import (
- "bytes"
  "encoding/hex"
  "errors"
- "fmt"
 
- "github.com/stellar/go/hash"
+ "github.com/stellar/go/network"
  "github.com/stellar/go/xdr"
 )
 
@@ -28,9 +26,9 @@ type TransactionMutator interface {
 
 // TransactionBuilder represents a Transaction that is being constructed.
 type TransactionBuilder struct {
- TX *xdr.Transaction
- NetworkID [32]byte
- Err error
+ TX  *xdr.Transaction
+ NetworkPassphrase string
+ Err  error
 }
 
 // Mutate applies the provided TransactionMutators to this builder's transaction
@@ -50,24 +48,7 @@ func (b *TransactionBuilder) Mutate(muts ...TransactionMutator) {
 
 // Hash returns the hash of this builder's transaction.
 func (b *TransactionBuilder) Hash() ([32]byte, error) {
- var txBytes bytes.Buffer
-
- _, err := fmt.Fprintf(&txBytes, "%s", b.NetworkID)
- if err != nil {
- return [32]byte{}, err
- }
-
- _, err = xdr.Marshal(&txBytes, xdr.EnvelopeTypeEnvelopeTypeTx)
- if err != nil {
- return [32]byte{}, err
- }
-
- _, err = xdr.Marshal(&txBytes, b.TX)
- if err != nil {
- return [32]byte{}, err
- }
-
- return hash.Hash(txBytes.Bytes()), nil
+ return network.HashTransaction(b.TX, b.NetworkPassphrase)
 }
 
 // HashHex returns the hex-encoded hash of this builder's transaction
@@ -175,8 +156,8 @@ func (m Defaults) MutateTransaction(o *TransactionBuilder) error {
  o.TX.Fee = xdr.Uint32(100 * len(o.TX.Operations))
  }
 
- if o.NetworkID == [32]byte{} {
- o.NetworkID = DefaultNetwork.ID()
+ if o.NetworkPassphrase == "" {
+ o.NetworkPassphrase = DefaultNetwork.Passphrase
  }
  return nil
 }
@@ -257,7 +238,7 @@ func (m MemoText) MutateTransaction(o *TransactionBuilder) (err error) {
 
 // MutateTransaction for Network sets the Network ID to use when signing this transaction
 func (m Network) MutateTransaction(o *TransactionBuilder) error {
- o.NetworkID = m.ID()
+ o.NetworkPassphrase = m.Passphrase
  return nil
 }
 

build/transaction_test.go

@@ -22,7 +22,7 @@ var _ = Describe("Transaction Mutators:", func() {
  mut = Defaults{}
  })
  It("sets the fee", func() { Expect(subject.TX.Fee).To(BeEquivalentTo(100)) })
- It("sets the network id", func() { Expect(subject.NetworkID).To(Equal(DefaultNetwork.ID())) })
+ It("sets the network passphrase", func() { Expect(subject.NetworkPassphrase).To(Equal(DefaultNetwork.Passphrase)) })
 
  Context("on a transaction with 2 operations", func() {
  BeforeEach(func() { subject.Mutate(Payment()) })

network/main.go

@@ -3,7 +3,12 @@
 package network
 
 import (
+ "bytes"
+ "fmt"
+
  "github.com/stellar/go/hash"
+ "github.com/stellar/go/support/errors"
+ "github.com/stellar/go/xdr"
 )
 
 const (
@@ -19,3 +24,28 @@ const (
 func ID(passphrase string) [32]byte {
  return hash.Hash([]byte(passphrase))
 }
+
+// HashTransaction derives the network specific hash for the provided
+// transaction using the network identified by the supplied passphrase. The
+// resulting hash is the value that can be signed by stellar secret key to
+// authorize the transaction identified by the hash to stellar validators.
+func HashTransaction(tx *xdr.Transaction, passphrase string) ([32]byte, error) {
+ var txBytes bytes.Buffer
+
+ _, err := fmt.Fprintf(&txBytes, "%s", ID(passphrase))
+ if err != nil {
+ return [32]byte{}, errors.Wrap(err, "fprint network id failed")
+ }
+
+ _, err = xdr.Marshal(&txBytes, xdr.EnvelopeTypeEnvelopeTypeTx)
+ if err != nil {
+ return [32]byte{}, errors.Wrap(err, "marshal type failed")
+ }
+
+ _, err = xdr.Marshal(&txBytes, tx)
+ if err != nil {
+ return [32]byte{}, errors.Wrap(err, "marshal tx failed")
+ }
+
+ return hash.Hash(txBytes.Bytes()), nil
+}