Add missing EIP191 prefix for EIP712

1 files changed, 63 insertions, 0 deletions

diff --git a/packages/contracts/src/utils/eip712_utils.ts b/packages/contracts/src/utils/eip712_utils.ts
new file mode 100644
index 000000000..07b45c8af
--- /dev/null
+++ b/packages/contracts/src/utils/eip712_utils.ts
@@ -0,0 +1,63 @@
+import { BigNumber } from '@0xproject/utils';
+import ethUtil = require('ethereumjs-util');
+import * as _ from 'lodash';
+
+import { crypto } from './crypto';
+import { EIP712Schema } from './types';
+
+const EIP191_PREFIX = '\x19\x01';
+const EIP712_DOMAIN_NAME = '0x Protocol';
+const EIP712_DOMAIN_VERSION = '1';
+
+const EIP712_DOMAIN_SCHEMA: EIP712Schema = {
+    name: 'DomainSeparator',
+    parameters: [
+        { name: 'name', type: 'string' },
+        { name: 'version', type: 'string' },
+        { name: 'contract', type: 'address' },
+    ],
+};
+
+export const EIP712Utils = {
+    compileSchema(schema: EIP712Schema): Buffer {
+        const namedTypes = _.map(schema.parameters, parameter => `${parameter.type} ${parameter.name}`);
+        const namedTypesJoined = namedTypes.join(',');
+        const eip712Schema = `${schema.name}(${namedTypesJoined})`;
+        const eip712SchemaHashBuffer = crypto.solSHA3([eip712Schema]);
+        return eip712SchemaHashBuffer;
+    },
+    createEIP712Message(hashStruct: string, contractAddress: string): Buffer {
+        const domainSeparatorHashHex = EIP712Utils.getDomainSeparatorHashHex(contractAddress);
+        const messageBuff = crypto.solSHA3([
+            EIP191_PREFIX,
+            new BigNumber(domainSeparatorHashHex),
+            new BigNumber(hashStruct),
+        ]);
+        return messageBuff;
+    },
+    getDomainSeparatorSchemaBuffer(): Buffer {
+        return EIP712Utils.compileSchema(EIP712_DOMAIN_SCHEMA);
+    },
+    getDomainSeparatorHashHex(exchangeAddress: string): string {
+        const domainSeparatorSchemaBuffer = EIP712Utils.getDomainSeparatorSchemaBuffer();
+        const nameHash = crypto.solSHA3([EIP712_DOMAIN_NAME]);
+        const versionHash = crypto.solSHA3([EIP712_DOMAIN_VERSION]);
+        const domainSeparatorHashBuff = crypto.solSHA3([
+            domainSeparatorSchemaBuffer,
+            nameHash,
+            versionHash,
+            EIP712Utils.pad32Address(exchangeAddress),
+        ]);
+        const domainSeparatorHashHex = `0x${domainSeparatorHashBuff.toString('hex')}`;
+        return domainSeparatorHashHex;
+    },
+    pad32Address(address: string): Buffer {
+        const addressBuffer = ethUtil.toBuffer(address);
+        const addressPadded = EIP712Utils.pad32Buffer(addressBuffer);
+        return addressPadded;
+    },
+    pad32Buffer(buffer: Buffer): Buffer {
+        const bufferPadded = ethUtil.setLengthLeft(buffer, 32);
+        return bufferPadded;
+    },
+};