Add EIP 712 helpers (#2418)

test/drafts/EIP712.test.js

@@ -0,0 +1,70 @@
+const ethSigUtil = require('eth-sig-util');
+const Wallet = require('ethereumjs-wallet').default;
+
+const EIP712 = artifacts.require('EIP712External');
+
+const EIP712Domain = [
+  { name: 'name', type: 'string' },
+  { name: 'version', type: 'string' },
+  { name: 'chainId', type: 'uint256' },
+  { name: 'verifyingContract', type: 'address' },
+];
+
+async function domainSeparator (name, version, chainId, verifyingContract) {
+  return '0x' + ethSigUtil.TypedDataUtils.hashStruct(
+    'EIP712Domain',
+    { name, version, chainId, verifyingContract },
+    { EIP712Domain },
+  ).toString('hex');
+}
+
+contract('EIP712', function (accounts) {
+  const [mailTo] = accounts;
+
+  const name = 'A Name';
+  const version = '1';
+
+  beforeEach('deploying', async function () {
+    this.eip712 = await EIP712.new(name, version);
+
+    // We get the chain id from the contract because Ganache (used for coverage) does not return the same chain id
+    // from within the EVM as from the JSON RPC interface.
+    // See https://github.com/trufflesuite/ganache-core/issues/515
+    this.chainId = await this.eip712.getChainId();
+  });
+
+  it('domain separator', async function () {
+    expect(
+      await this.eip712.domainSeparator(),
+    ).to.equal(
+      await domainSeparator(name, version, this.chainId, this.eip712.address),
+    );
+  });
+
+  it('digest', async function () {
+    const chainId = this.chainId;
+    const verifyingContract = this.eip712.address;
+    const message = {
+      to: mailTo,
+      contents: 'very interesting',
+    };
+
+    const data = {
+      types: {
+        EIP712Domain,
+        Mail: [
+          { name: 'to', type: 'address' },
+          { name: 'contents', type: 'string' },
+        ],
+      },
+      domain: { name, version, chainId, verifyingContract },
+      primaryType: 'Mail',
+      message,
+    };
+
+    const wallet = Wallet.generate();
+    const signature = ethSigUtil.signTypedMessage(wallet.getPrivateKey(), { data });
+
+    await this.eip712.verify(signature, wallet.getAddressString(), message.to, message.contents);
+  });
+});