From f2f5c1686edde23f98dc50141aa465c6047e134d Mon Sep 17 00:00:00 2001
From: Michele Esposito <michele@esposito.codes>
Date: Mon, 10 Jul 2023 18:26:28 +0200
Subject: [PATCH] feat: validate checksum addresses

---
 package.json    |  1 +
 src/hex.test.ts | 23 +++++++++++++++++++++++
 src/hex.ts      | 44 ++++++++++++++++++++++++++++++++++++++++++--
 yarn.lock       | 10 +++++++++-
 4 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/package.json b/package.json
index 7eb26aa85..80794aceb 100644
--- a/package.json
+++ b/package.json
@@ -38,6 +38,7 @@
   },
   "dependencies": {
     "@ethereumjs/tx": "^4.1.2",
+    "@noble/hashes": "^1.3.1",
     "@types/debug": "^4.1.7",
     "debug": "^4.3.4",
     "semver": "^7.3.8",
diff --git a/src/hex.test.ts b/src/hex.test.ts
index efac6dfba..a191d7061 100644
--- a/src/hex.test.ts
+++ b/src/hex.test.ts
@@ -3,6 +3,7 @@ import {
   add0x,
   assertIsHexString,
   assertIsStrictHexString,
+  isChecksumAddress,
   isHexString,
   isStrictHexString,
   isValidHexAddress,
@@ -182,6 +183,8 @@ describe('isValidHexAddress', () => {
     '0x1234567890abcdefG',
     '0x1234567890abcdefABCDEFg',
     '0x1234567890abcdefABCDEF1234567890abcdefABCDEFg',
+    '0xD8DA6BF26964AF9D7EED9E03E53415D37AA96045',
+    '0xCF5609B003B2776699EEA1233F7C82D5695CC9AA',
     '0Xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045',
   ])('returns false for an invalid hex address', (hexString) => {
     // @ts-expect-error - testing invalid input
@@ -189,6 +192,26 @@ describe('isValidHexAddress', () => {
   });
 });
 
+describe('isChecksumAddress', () => {
+  it.each([
+    '0x0000000000000000000000000000000000000000' as Hex,
+    '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045' as Hex,
+    '0xCf5609B003B2776699eEA1233F7C82D5695cC9AA' as Hex,
+    '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045' as Hex,
+    '0x8617E340B3D01FA5F11F306F4090FD50E238070D' as Hex,
+  ])('returns true for a valid checksum address', (hexString) => {
+    expect(isChecksumAddress(hexString)).toBe(true);
+  });
+
+  it.each([
+    '0xz' as Hex,
+    '0xD8DA6BF26964AF9D7EED9E03E53415D37AA96045' as Hex,
+    '0xCF5609B003B2776699EEA1233F7C82D5695CC9AA' as Hex,
+  ])('returns false for an invalid checksum address', (hexString) => {
+    expect(isChecksumAddress(hexString)).toBe(false);
+  });
+});
+
 describe('add0x', () => {
   it('adds a 0x-prefix to a string', () => {
     expect(add0x('12345')).toBe('0x12345');
diff --git a/src/hex.ts b/src/hex.ts
index dbe30a39c..cbd3bfdab 100644
--- a/src/hex.ts
+++ b/src/hex.ts
@@ -1,6 +1,8 @@
+import { keccak_256 as keccak256 } from '@noble/hashes/sha3';
 import { is, pattern, string, Struct } from 'superstruct';
 
 import { assert } from './assert';
+import { bytesToHex } from './bytes';
 
 export type Hex = `0x${string}`;
 
@@ -10,6 +12,10 @@ export const StrictHexStruct = pattern(string(), /^0x[0-9a-f]+$/iu) as Struct<
   null
 >;
 export const HexAddressStruct = pattern(
+  string(),
+  /^0x[0-9a-f]{40}$/u,
+) as Struct<Hex, null>;
+export const HexChecksumAddressStruct = pattern(
   string(),
   /^0x[0-9a-fA-F]{40}$/u,
 ) as Struct<Hex, null>;
@@ -60,13 +66,47 @@ export function assertIsStrictHexString(value: unknown): asserts value is Hex {
 }
 
 /**
- * Validates that the passed prefixed hex string is a valid hex address.
+ * Validate that the passed prefixed hex string is a valid hex address, or a
+ * valid mixed-case checksum address.
  *
  * @param possibleAddress - Input parameter to check against.
  * @returns Whether or not the input is a valid hex address.
  */
 export function isValidHexAddress(possibleAddress: Hex) {
-  return is(possibleAddress, HexAddressStruct);
+  return (
+    is(possibleAddress, HexAddressStruct) ||
+    isValidChecksumAddress(possibleAddress)
+  );
+}
+
+/**
+ * Validate that the passed hex string is a valid ERC-55 mixed-case
+ * checksum address.
+ *
+ * @param possibleChecksum - The hex address to check.
+ * @returns True if the address is a checksum address.
+ */
+export function isValidChecksumAddress(possibleChecksum: Hex) {
+  if (!is(possibleChecksum, HexChecksumAddressStruct)) {
+    return false;
+  }
+
+  const unPrefixed = remove0x(possibleChecksum);
+  const unPrefixedHash = remove0x(
+    bytesToHex(keccak256(unPrefixed.toLowerCase())),
+  );
+
+  for (let i = 0; i < unPrefixedHash.length; i++) {
+    const value = parseInt(unPrefixedHash[i] as string, 16);
+    if (
+      (value > 7 && unPrefixed[i]?.toUpperCase() !== unPrefixed[i]) ||
+      (value <= 7 && unPrefixed[i]?.toLowerCase() !== unPrefixed[i])
+    ) {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 /**
diff --git a/yarn.lock b/yarn.lock
index 92902c418..b9ee57cc4 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1069,6 +1069,7 @@ __metadata:
     "@metamask/eslint-config-jest": ^11.0.0
     "@metamask/eslint-config-nodejs": ^11.0.1
     "@metamask/eslint-config-typescript": ^11.0.0
+    "@noble/hashes": ^1.3.1
     "@types/debug": ^4.1.7
     "@types/jest": ^28.1.7
     "@types/node": ^17.0.23
@@ -1108,13 +1109,20 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@noble/hashes@npm:1.3.0, @noble/hashes@npm:^1.3.0, @noble/hashes@npm:~1.3.0":
+"@noble/hashes@npm:1.3.0":
   version: 1.3.0
   resolution: "@noble/hashes@npm:1.3.0"
   checksum: d7ddb6d7c60f1ce1f87facbbef5b724cdea536fc9e7f59ae96e0fc9de96c8f1a2ae2bdedbce10f7dcc621338dfef8533daa73c873f2b5c87fa1a4e05a95c2e2e
   languageName: node
   linkType: hard
 
+"@noble/hashes@npm:^1.3.0, @noble/hashes@npm:^1.3.1, @noble/hashes@npm:~1.3.0":
+  version: 1.3.1
+  resolution: "@noble/hashes@npm:1.3.1"
+  checksum: 7fdefc0f7a0c1ec27acc6ff88841793e3f93ec4ce6b8a6a12bfc0dd70ae6b7c4c82fe305fdfeda1735d5ad4a9eebe761e6693b3d355689c559e91242f4bc95b1
+  languageName: node
+  linkType: hard
+
 "@nodelib/fs.scandir@npm:2.1.5":
   version: 2.1.5
   resolution: "@nodelib/fs.scandir@npm:2.1.5"