Merge pull request #81 from benjamincburns/issue80-hash-collisions

fixes #80

fake.js

@@ -53,4 +53,20 @@ module.exports = class FakeTransaction extends Transaction {
       this.from = data.from
     }
   }
+
+  /**
+   * Computes a sha3-256 hash of the serialized tx, using the sender address to generate a fake signature.
+   * @param {Boolean} [includeSignature=true] whether or not to inculde the signature
+   * @return {Buffer}
+   */
+  hash (includeSignature) {
+    if (includeSignature && this._from) {
+      // include a fake signature using the from address as a private key
+      let fakeKey = Buffer.concat([this._from, this._from.slice(0, 12)])
+      this.sign(fakeKey)
+    }
+
+    return super.hash(includeSignature)
+  }
 }
+

test/fake.js

@@ -0,0 +1,23 @@
+const tape = require('tape')
+const utils = require('ethereumjs-util')
+const FakeTransaction = require('../fake.js')
+tape('[FakeTransaction]: Basic functions', function (t) {
+  t.test('should not produce hash collsions for different senders', function (st) {
+    st.plan(1)
+    var baseTxData = {
+      data: '0x7cf5dab00000000000000000000000000000000000000000000000000000000000000005',
+      gasLimit: '0x15f90',
+      gasPrice: '0x1',
+      nonce: '0x01',
+      to: '0xd9024df085d09398ec76fbed18cac0e1149f50dc',
+      value: '0x0',
+      from: '0x1111111111111111111111111111111111111111'
+    }
+    var modifiedFromFieldTxData = Object.assign({}, baseTxData, { from: '0x2222222222222222222222222222222222222222' })
+    var baseTx = new FakeTransaction(baseTxData)
+    var modifiedFromFieldTx = new FakeTransaction(modifiedFromFieldTxData)
+    var baseTxHash = utils.bufferToHex(baseTx.hash(true))
+    var modifiedFromFieldTxHash = utils.bufferToHex(modifiedFromFieldTx.hash(true))
+    st.notEqual(baseTxHash, modifiedFromFieldTxHash, 'FakeTransactions with different `from` addresses but otherwise identical data should have different hashes')
+  })
+})

test/index.js

@@ -1,2 +1,3 @@
+require('./fake.js')
 require('./api.js')
 require('./transactionRunner.js')