Create assert.isValidSignature method and use it in addOrder

src/order_watcher/order_state_watcher.ts

@@ -60,6 +60,7 @@ export class OrderStateWatcher {
     public addOrder(signedOrder: SignedOrder): void {
         assert.doesConformToSchema('signedOrder', signedOrder, schemas.signedOrderSchema);
         const orderHash = ZeroEx.getOrderHashHex(signedOrder);
+        assert.isValidSignature(orderHash, signedOrder.ecSignature, signedOrder.maker);
         this._orders[orderHash] = signedOrder;
         this.addToDependentOrderHashes(signedOrder, orderHash);
     }

src/utils/assert.ts

@@ -1,8 +1,10 @@
 import * as _ from 'lodash';
-import BigNumber from 'bignumber.js';
 import * as Web3 from 'web3';
-import {Web3Wrapper} from '../web3_wrapper';
+import BigNumber from 'bignumber.js';
 import {SchemaValidator, Schema} from '0x-json-schemas';
+import {Web3Wrapper} from '../web3_wrapper';
+import {signatureUtils} from '../utils/signature_utils';
+import {ECSignature} from '../types';
 
 const HEX_REGEX = /^0x[0-9A-F]*$/i;
 
@@ -18,6 +20,10 @@ export const assert = {
             !hasDecimals, `${variableName} should be in baseUnits (no decimals), found value: ${value.toNumber()}`,
         );
     },
+    isValidSignature(orderHash: string, ecSignature: ECSignature, signerAddress: string) {
+        const isValidSignature = signatureUtils.isValidSignature(orderHash, ecSignature, signerAddress);
+        this.assert(isValidSignature, `Expected order with hash '${orderHash}' to have a valid signature`);
+    },
     isUndefined(value: any, variableName?: string): void {
         this.assert(_.isUndefined(value), this.typeAssertionMessage(variableName, 'undefined', value));
     },