From c3e1244e52385eb9f6d49a94b10ee9a631a973c4 Mon Sep 17 00:00:00 2001
From: manolodewiner <manuel@bigchaindb.com>
Date: Thu, 1 Mar 2018 12:22:36 +0100
Subject: [PATCH] unique-fulfillment and hash&sign

---
 .travis.yml                               |  2 +-
 src/transaction.js                        | 24 +++++++++++------------
 test/transaction/test_cryptoconditions.js | 18 ++++++++++++++---
 3 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 7d4f5cc..b0f09a5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,7 +18,7 @@ before_install:
       -e BIGCHAINDB_KEYPAIR_PRIVATE=5C5Cknco7YxBRP9AgB1cbUVTL4FAcooxErLygw1DeG2D
       -e BIGCHAINDB_DATABASE_BACKEND=mongodb
       -e BIGCHAINDB_DATABASE_HOST=172.17.0.1
-      bigchaindb/bigchaindb:1.3.0
+      bigchaindb/bigchaindb:1.4.0
       start
     - gem install cowsay
     - npm install -g codecov
diff --git a/src/transaction.js b/src/transaction.js
index f84cf4c..8c15f1c 100644
--- a/src/transaction.js
+++ b/src/transaction.js
@@ -30,14 +30,6 @@ export default class Transaction {
         }
     }
 
-    static hashTransaction(transaction) {
-        // Safely remove any tx id from the given transaction for hashing
-        const tx = { ...transaction }
-        delete tx.id
-
-        return sha256Hash(Transaction.serializeTransactionIntoCanonicalString(tx))
-    }
-
     static makeTransactionTemplate() {
         const txTemplate = {
             'id': null,
@@ -58,8 +50,6 @@ export default class Transaction {
         tx.metadata = metadata
         tx.inputs = inputs
         tx.outputs = outputs
-
-        tx.id = Transaction.hashTransaction(tx)
         return tx
     }
 
@@ -246,15 +236,23 @@ export default class Transaction {
         signedTx.inputs.forEach((input, index) => {
             const privateKey = privateKeys[index]
             const privateKeyBuffer = Buffer.from(base58.decode(privateKey))
-            const serializedTransaction = Transaction
-                .serializeTransactionIntoCanonicalString(transaction)
+            const serializedTransaction =
+                Transaction.serializeTransactionIntoCanonicalString(transaction)
+
+            const transactionUniqueFulfillment = input.fulfills ? serializedTransaction
+                .concat(input.fulfills.transaction_id)
+                .concat(input.fulfills.output_index) : serializedTransaction
+            const transactionHash = sha256Hash(transactionUniqueFulfillment)
             const ed25519Fulfillment = new cc.Ed25519Sha256()
-            ed25519Fulfillment.sign(Buffer.from(serializedTransaction), privateKeyBuffer)
+            ed25519Fulfillment.sign(Buffer.from(transactionHash, 'hex'), privateKeyBuffer)
             const fulfillmentUri = ed25519Fulfillment.serializeUri()
 
             input.fulfillment = fulfillmentUri
         })
 
+        const serializedTransaction =
+                Transaction.serializeTransactionIntoCanonicalString(signedTx)
+        signedTx.id = sha256Hash(serializedTransaction)
         return signedTx
     }
 }
diff --git a/test/transaction/test_cryptoconditions.js b/test/transaction/test_cryptoconditions.js
index 4673e17..65e389b 100644
--- a/test/transaction/test_cryptoconditions.js
+++ b/test/transaction/test_cryptoconditions.js
@@ -1,6 +1,7 @@
 import test from 'ava'
 import cc from 'crypto-conditions'
 import { Ed25519Keypair, Transaction, ccJsonLoad } from '../../src'
+import sha256Hash from '../../src/sha256Hash'
 
 test('Ed25519 condition encoding', t => {
     const publicKey = '4zvwRjXUKGfvwnParsHAS3HuSVzV5cA4McphgmoCtajS'
@@ -53,16 +54,27 @@ test('Fulfillment correctly formed', t => {
         [Transaction.makeOutput(Transaction.makeEd25519Condition(alice.publicKey))],
         alice.publicKey
     )
+    // Sign in order to get the tx id, needed for the unique fulfillment in the transfer transaction
+    const signCreateTransaction = Transaction.signTransaction(txCreate, alice.privateKey)
+
     const txTransfer = Transaction.makeTransferTransaction(
-        [{ tx: txCreate, output_index: 0 }],
+        [{ tx: signCreateTransaction, output_index: 0 }],
         [Transaction.makeOutput(Transaction.makeEd25519Condition(alice.publicKey))],
         {}
     )
-    const msg = Transaction.serializeTransactionIntoCanonicalString(txTransfer)
     const txSigned = Transaction.signTransaction(txTransfer, alice.privateKey)
+
+    // Here reconstruct the fulfillment of the transfer transaction
+    // The tx is serialized, and extended with tx_id and output index, and then hashed into bytes
+    const msg = Transaction.serializeTransactionIntoCanonicalString(txTransfer)
+    const msgUniqueFulfillment = txTransfer.inputs[0].fulfills ? msg
+        .concat(txTransfer.inputs[0].fulfills.transaction_id)
+        .concat(txTransfer.inputs[0].fulfills.output_index) : msg
+    const msgHash = sha256Hash(msgUniqueFulfillment)
+
     t.truthy(cc.validateFulfillment(
         txSigned.inputs[0].fulfillment, txCreate.outputs[0].condition.uri,
-        Buffer.from(msg)
+        Buffer.from(msgHash, 'hex')
     ))
 })