From 8815a6e78989e8fde6edabdbb41c2742b133c14e Mon Sep 17 00:00:00 2001
From: meetsiraja <darkdespec@protonmail.com>
Date: Wed, 20 Nov 2019 15:49:24 +0530
Subject: [PATCH] Sign Transaction with ethereum account private key

---
 src/middleware/signed-tx-middleware.ts | 40 +++++++++++++++++++-------
 src/solidity-helpers.ts                | 21 ++++++--------
 2 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/src/middleware/signed-tx-middleware.ts b/src/middleware/signed-tx-middleware.ts
index 421d257c..5f873546 100644
--- a/src/middleware/signed-tx-middleware.ts
+++ b/src/middleware/signed-tx-middleware.ts
@@ -1,28 +1,46 @@
+import debug from 'debug'
 import { SignedTx } from '../proto/loom_pb'
 import { ITxMiddlewareHandler } from '../client'
-import { sign, publicKeyFromPrivateKey } from '../crypto-utils'
+import { OfflineWeb3Signer, soliditySha3 } from '../solidity-helpers'
+import { bytesToHex, hexToBytes } from '../crypto-utils'
+import Web3 from 'web3'
+
+const log = debug('signed-tx-middleware')
 
 /**
  * Signs transactions.
  */
 export class SignedTxMiddleware implements ITxMiddlewareHandler {
   // The private key that should be used to sign txs.
-  privateKey: Uint8Array
+  private _web3: Web3
+  private _account: any
 
   /**
-   * Creates middlware that signs txs with the given key.
-   * @param privateKey The private key that should be used to sign txs.
+   * @param web3 Web3 instance to use for signing.
+   * @param account Web3 account to sign with.
    */
-  constructor(privateKey: Uint8Array) {
-    this.privateKey = privateKey
+  constructor(web3: Web3, account: any) {
+    this._web3 = web3
+    this._account = account
   }
 
-  Handle(txData: Readonly<Uint8Array>): Promise<Uint8Array> {
-    const sig = sign(txData as Uint8Array, this.privateKey)
+  async Handle(txData: Readonly<Uint8Array>): Promise<Uint8Array> {
+    // Get hash to be signed
+    const hash = soliditySha3({
+      type: 'bytes',
+      value: bytesToHex(txData)
+    })
+
+    // Signing the transaction
+    const offlineSigner = new OfflineWeb3Signer(this._web3, this._account)
+    const sig = await offlineSigner.signAsync(hash)
+
+    log(`signer: ${this._account.address}, signature: 0x${bytesToHex(sig.slice(1))}`)
+
     const signedTx = new SignedTx()
     signedTx.setInner(txData as Uint8Array)
     signedTx.setSignature(sig)
-    signedTx.setPublicKey(publicKeyFromPrivateKey(this.privateKey))
-    return Promise.resolve(signedTx.serializeBinary())
+
+    return signedTx.serializeBinary()
   }
-}
+}
\ No newline at end of file
diff --git a/src/solidity-helpers.ts b/src/solidity-helpers.ts
index 343825d3..e2f2a378 100644
--- a/src/solidity-helpers.ts
+++ b/src/solidity-helpers.ts
@@ -136,18 +136,13 @@ export class OfflineWeb3Signer implements IEthereumSigner {
    * @returns Promise that will be resolved with the signature bytes.
    */
   async signAsync(msg: string): Promise<Uint8Array> {
-    const ret = await this._web3.eth.accounts.sign(msg, this._account.privateKey)
-    // @ts-ignore
-    const sig = ret.signature.slice(2)
-    const r = ethutil.toBuffer('0x' + sig.substring(0, 64)) as Buffer
-    const s = ethutil.toBuffer('0x' + sig.substring(64, 128)) as Buffer
-    let v = parseInt(sig.substring(128, 130), 16)
-
-    return Buffer.concat([
-      ethutil.toBuffer(SIGNATURE_TYPE.GETH) as Buffer,
-      r,
-      s,
-      ethutil.toBuffer(v) as Buffer
-    ])
+    let flatSig = await this._web3.eth.accounts.sign(msg, this._account.privateKey)
+    const sig = ethers.utils.splitSignature(flatSig)
+    let v = sig.v!
+    if (v === 0 || v === 1) {
+      v += 27
+    }
+    flatSig = '0x01' + sig.r.slice(2) + sig.s.slice(2) + v.toString(16)
+    return ethutil.toBuffer(flatSig)
   }
 }