Move ECDSA message hash methods to its own MessageHashUtils library (#4430)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Francisco <fg@frang.io>

test/utils/cryptography/MessageHashUtils.test.js

@@ -0,0 +1,55 @@
+require('@openzeppelin/test-helpers');
+const { toEthSignedMessageHash, toDataWithIntendedValidatorHash } = require('../../helpers/sign');
+const { domainSeparator, hashTypedData } = require('../../helpers/eip712');
+
+const { expect } = require('chai');
+
+const MessageHashUtils = artifacts.require('$MessageHashUtils');
+
+contract('MessageHashUtils', function () {
+  beforeEach(async function () {
+    this.messageHashUtils = await MessageHashUtils.new();
+
+    this.message = '0x' + Buffer.from('abcd').toString('hex');
+    this.messageHash = web3.utils.sha3(this.message);
+    this.verifyingAddress = web3.utils.toChecksumAddress(web3.utils.randomHex(20));
+  });
+
+  context('toEthSignedMessageHash', function () {
+    it('prefixes bytes32 data correctly', async function () {
+      expect(await this.messageHashUtils.methods['$toEthSignedMessageHash(bytes32)'](this.messageHash)).to.equal(
+        toEthSignedMessageHash(this.messageHash),
+      );
+    });
+
+    it('prefixes dynamic length data correctly', async function () {
+      expect(await this.messageHashUtils.methods['$toEthSignedMessageHash(bytes)'](this.message)).to.equal(
+        toEthSignedMessageHash(this.message),
+      );
+    });
+  });
+
+  context('toDataWithIntendedValidatorHash', function () {
+    it('returns the digest correctly', async function () {
+      expect(
+        await this.messageHashUtils.$toDataWithIntendedValidatorHash(this.verifyingAddress, this.message),
+      ).to.equal(toDataWithIntendedValidatorHash(this.verifyingAddress, this.message));
+    });
+  });
+
+  context('toTypedDataHash', function () {
+    it('returns the digest correctly', async function () {
+      const domain = {
+        name: 'Test',
+        version: 1,
+        chainId: 1,
+        verifyingContract: this.verifyingAddress,
+      };
+      const structhash = web3.utils.randomHex(32);
+      const expectedDomainSeparator = await domainSeparator(domain);
+      expect(await this.messageHashUtils.$toTypedDataHash(expectedDomainSeparator, structhash)).to.equal(
+        hashTypedData(domain, structhash),
+      );
+    });
+  });
+});