From ccbfecfa63aa5037455405d929aea6322590d6ac Mon Sep 17 00:00:00 2001
From: Chris Lexmond <chris@chrislexmond.com>
Date: Fri, 23 Sep 2022 10:10:13 -0400
Subject: [PATCH] fix: fixed hash arg sorting in merkle tree generation

---
 CONTRIBUTING.md                   |  4 ++--
 __tests__/utils/merkle.test.ts    | 11 +++++++++++
 __tests__/utils/typedData.test.ts |  2 +-
 src/utils/merkle.ts               | 10 +++++++++-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index dc49a8d6f..1682d3d6a 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -19,7 +19,7 @@ ALways start from `develop` branch and merge back to `develop` branch.
 To build you changes run:
 
 ```bash
-npm build
+npm run build
 ```
 
 Run linters and tests:
@@ -31,7 +31,7 @@ npm test
 Or run tests in watch mode:
 
 ```bash
-npm run test --watch
+npm test --watch
 ```
 
 **Don’t forget to add tests and update documentation for your changes.**
diff --git a/__tests__/utils/merkle.test.ts b/__tests__/utils/merkle.test.ts
index 2c1fb8764..41980d017 100644
--- a/__tests__/utils/merkle.test.ts
+++ b/__tests__/utils/merkle.test.ts
@@ -1,6 +1,17 @@
+import { pedersen } from '../../src/utils/hash';
 import { MerkleTree, proofMerklePath } from '../../src/utils/merkle';
 
 describe('MerkleTree class', () => {
+  describe('calculate hashes', () => {
+    test('should generate hash with sorted arguments', async () => {
+      const leaves = ['0x12', '0xa']; // 18, 10
+
+      const merkleHash = MerkleTree.hash(leaves[0], leaves[1]);
+      const rawHash = pedersen([10, 18]);
+
+      expect(merkleHash).toBe(rawHash);
+    });
+  });
   describe('generate roots', () => {
     test('should generate valid root for 1 elements', async () => {
       const leaves = ['0x1'];
diff --git a/__tests__/utils/typedData.test.ts b/__tests__/utils/typedData.test.ts
index 78d82b78c..1ba42f29f 100644
--- a/__tests__/utils/typedData.test.ts
+++ b/__tests__/utils/typedData.test.ts
@@ -72,7 +72,7 @@ describe('typedData', () => {
     const [, merkleTreeHash] = encodeValue({}, 'merkletree', tree.leaves);
     expect(merkleTreeHash).toBe(tree.root);
     expect(merkleTreeHash).toMatchInlineSnapshot(
-      `"0x551b4adb6c35d49c686a00b9192da9332b18c9b262507cad0ece37f3b6918d2"`
+      `"0x5cdd7ef6b0b1cf28fba033a8369dec45d1d94101c0550ac8a26bd8133695e07"`
     );
   });
 
diff --git a/src/utils/merkle.ts b/src/utils/merkle.ts
index 1dd288c0c..4812560f0 100644
--- a/src/utils/merkle.ts
+++ b/src/utils/merkle.ts
@@ -1,4 +1,5 @@
 import { pedersen } from './hash';
+import { toBN } from './number';
 
 export class MerkleTree {
   public leaves: string[];
@@ -31,7 +32,14 @@ export class MerkleTree {
   }
 
   static hash(a: string, b: string) {
-    const [aSorted, bSorted] = [a, b].sort();
+    let aSorted = a;
+    let bSorted = b;
+
+    if (toBN(aSorted) > toBN(bSorted)) {
+      aSorted = b;
+      bSorted = a;
+    }
+
     return pedersen([aSorted, bSorted]);
   }