From d9a271742f7c6c5607c0e21fdb545161781615c4 Mon Sep 17 00:00:00 2001
From: Tyera Eulberg <tyera@solana.com>
Date: Tue, 3 Mar 2020 13:39:00 -0700
Subject: [PATCH] feat: add transaction signature verification

---
 web3.js/flow-typed/tweetnacl.js          | 10 ++-
 web3.js/src/transaction.js               | 16 +++++
 web3.js/test/get-confirmed-block.test.js | 81 ++++++++++++++++++++++++
 3 files changed, 104 insertions(+), 3 deletions(-)
 create mode 100644 web3.js/test/get-confirmed-block.test.js

diff --git a/web3.js/flow-typed/tweetnacl.js b/web3.js/flow-typed/tweetnacl.js
index a797309b5c..552b47a8a6 100644
--- a/web3.js/flow-typed/tweetnacl.js
+++ b/web3.js/flow-typed/tweetnacl.js
@@ -8,13 +8,17 @@ declare module "tweetnacl" {
     (): KeyPair,
     fromSecretKey(secretKey: Buffer): KeyPair,
     fromSeed(seed: Uint8Array): KeyPair,
-
   };
+
+  declare type DetachedFunc = {
+    (text: Buffer, secretKey: Buffer): Buffer,
+    verify(message: Buffer, signature: Buffer|null, publicKey: Buffer): bool,
+  };
+
   declare module.exports: {
     sign: {
       keyPair: KeypairFunc;
-      detached(text: Buffer, secretKey: Buffer): Buffer;
+      detached: DetachedFunc;
     };
   };
 }
-
diff --git a/web3.js/src/transaction.js b/web3.js/src/transaction.js
index 7821ec2372..b63b8012a9 100644
--- a/web3.js/src/transaction.js
+++ b/web3.js/src/transaction.js
@@ -411,6 +411,22 @@ export class Transaction {
     this.signatures[index].signature = Buffer.from(signature);
   }
 
+  /**
+   * Verify signatures of a complete, signed Transaction
+   */
+  verifySignatures(): boolean {
+    let verified = true;
+    const signData = this._getSignData();
+    for (const {signature, publicKey} of this.signatures) {
+      if (
+        !nacl.sign.detached.verify(signData, signature, publicKey.toBuffer())
+      ) {
+        verified = false;
+      }
+    }
+    return verified;
+  }
+
   /**
    * Serialize the Transaction in the wire format.
    *
diff --git a/web3.js/test/get-confirmed-block.test.js b/web3.js/test/get-confirmed-block.test.js
new file mode 100644
index 0000000000..55be8e5e38
--- /dev/null
+++ b/web3.js/test/get-confirmed-block.test.js
@@ -0,0 +1,81 @@
+// @flow
+import {Account} from '../src/account';
+import {SystemProgram} from '../src/system-program';
+import {Transaction} from '../src/transaction';
+
+test('verify getConfirmedBlock', () => {
+  const account0 = new Account();
+  const account1 = new Account();
+  const account2 = new Account();
+  const account3 = new Account();
+  const recentBlockhash = account1.publicKey.toBase58(); // Fake recentBlockhash
+
+  // Create a couple signed transactions
+  const transfer0 = SystemProgram.transfer(
+    account0.publicKey,
+    account1.publicKey,
+    123,
+  );
+
+  const transaction0 = new Transaction({recentBlockhash}).add(transfer0);
+  transaction0.sign(account0);
+  const transfer1 = SystemProgram.transfer(
+    account2.publicKey,
+    account3.publicKey,
+    456,
+  );
+
+  let transaction1 = new Transaction({recentBlockhash}).add(transfer1);
+  transaction1.sign(account2);
+
+  // Build ConfirmedBlock, with dummy data for blockhashes, balances
+  const confirmedBlock = {
+    blockhash: recentBlockhash,
+    previousBlockhash: recentBlockhash,
+    transactions: [
+      {
+        transaction: transaction0,
+        meta: {
+          fee: 0,
+          preBalances: [100000, 100000, 1, 1, 1],
+          postBalances: [99877, 100123, 1, 1, 1],
+          status: {Ok: 'null'},
+        },
+      },
+      {
+        transaction: transaction1,
+        meta: {
+          fee: 0,
+          preBalances: [100000, 100000, 1, 1, 1],
+          postBalances: [99544, 100456, 1, 1, 1],
+          status: {Ok: 'null'},
+        },
+      },
+    ],
+    rewards: [],
+  };
+
+  // Verify signatures in ConfirmedBlock
+  for (const transactionWithMeta of confirmedBlock.transactions) {
+    expect(transactionWithMeta.transaction.verifySignatures()).toBe(true);
+  }
+
+  const bogusSignature = {
+    signature: Buffer.alloc(64, 9),
+    publicKey: account2.publicKey,
+  };
+  transaction1.signatures[0] = bogusSignature;
+
+  let badConfirmedBlock = confirmedBlock;
+  badConfirmedBlock.transactions[1].transaction = transaction1;
+
+  // Verify signatures in ConfirmedBlock
+  const verifications = badConfirmedBlock.transactions.map(
+    transactionWithMeta => transactionWithMeta.transaction.verifySignatures(),
+  );
+  expect(
+    verifications.reduce(
+      (accumulator, currentValue) => accumulator && currentValue,
+    ),
+  ).toBe(false);
+});