Drop ComposableCoW bytecode check (#151)

# Description
Removes the janky bytecode check that was being used to enforce that the
contract being indexed was `ComposableCoW` compatible. This is possible
given that there are exhaustive switch statements that were published
for the revert messages.

# Changes

- [x] Add a try/catch around the decode function result to catch bad
`ComposableCoW`-like implementations.
- [x] Remove bytecode checks.

## How to test
1. Remove the sepolia database.
2. Restart
3. Observe new CoW AMMs 🚀

---------

Co-authored-by: Federico Giacon <[email protected]>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@cowprotocol/watch-tower",
   "license": "GPL-3.0-or-later",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "A standalone watch tower, keeping an eye on Composable Cows  👀🐮",
   "author": {
     "name": "Cow Protocol"

src/domain/events/index.ts

@@ -2,7 +2,6 @@ import {
   toConditionalOrderParams,
   getLogger,
   handleExecutionError,
-  isComposableCowCompatible,
   metrics,
 } from "../../utils";
 import { BytesLike, ethers } from "ethers";
@@ -50,19 +49,13 @@ async function _addContract(
 ) {
   const log = getLogger("addContract:_addContract");
   const composableCow = ComposableCoW__factory.createInterface();
-  const { provider, registry } = context;
+  const { registry } = context;
   const { transactionHash: tx, blockNumber } = event;
 
   // Process the logs
   let hasErrors = false;
   let numContractsAdded = 0;
 
-  // Do not process logs that are not from a `ComposableCoW`-compatible contract
-  // This is a *normal* case, if the contract is not `ComposableCoW`-compatible
-  // then we do not need to do anything, and therefore don't flag as an error.
-  if (!isComposableCowCompatible(await provider.getCode(event.address))) {
-    return;
-  }
   const { error, added } = await _registerNewOrder(
     event,
     composableCow,

src/domain/polling/index.ts

@@ -665,11 +665,11 @@ async function _pollLegacy(
 ): Promise<PollResult> {
   const { contract, multicall, chainId } = context;
   const log = getLogger("checkForAndPlaceOrder:_pollLegacy", orderRef);
+  const { composableCow: target } = conditionalOrder;
   const { handler } = conditionalOrder.params;
   // as we going to use multicall, with `aggregate3Value`, there is no need to do any simulation as the
   // calls are guaranteed to pass, and will return the results, or the reversion within the ABI-encoded data.
   // By not using `populateTransaction`, we avoid an `eth_estimateGas` RPC call.
-  const target = contract.address;
   const callData = contract.interface.encodeFunctionData(
     "getTradeableOrderWithSignature",
     [owner, conditionalOrder.params, offchainInput, proof]
@@ -690,16 +690,27 @@ async function _pollLegacy(
     const [{ success, returnData }] = lowLevelCall;
 
     if (success) {
-      // Decode the returnData to get the order and signature tuple
-      const { order, signature } = contract.interface.decodeFunctionResult(
-        "getTradeableOrderWithSignature",
-        returnData
-      );
-      return {
-        result: PollResultCode.SUCCESS,
-        order,
-        signature,
-      };
+      try {
+        // Decode the returnData to get the order and signature tuple
+        const { order, signature } = contract.interface.decodeFunctionResult(
+          "getTradeableOrderWithSignature",
+          returnData
+        );
+        return {
+          result: PollResultCode.SUCCESS,
+          order,
+          signature,
+        };
+      } catch (error: any) {
+        log.error(`ethers/decodeFunctionResult Unexpected error`, error);
+        metrics.pollingOnChainEthersErrorsTotal.labels(...metricLabels).inc();
+        return {
+          result: PollResultCode.DONT_TRY_AGAIN,
+          reason:
+            "UnexpectedErrorName: Data decoding failure" +
+            (error.message ? `: ${error.message}` : ""),
+        };
+      }
     }
 
     // If the low-level call failed, per the `ComposableCoW` interface, the contract is attempting to

src/services/chain.ts

@@ -16,15 +16,14 @@ import {
 } from "@cowprotocol/cow-sdk";
 import { addContract } from "../domain/events";
 import { checkForAndPlaceOrder } from "../domain/polling";
-import { EventFilter, providers } from "ethers";
+import { ethers, providers } from "ethers";
 import {
   composableCowContract,
   getLogger,
   isRunningInKubernetesPod,
   metrics,
 } from "../utils";
 import { DBService } from ".";
-import { hexZeroPad } from "ethers/lib/utils";
 import { policy } from "../domain/polling/filtering";
 
 const WATCHDOG_FREQUENCY_SECS = 5; // 5 seconds
@@ -506,22 +505,43 @@ async function processBlock(
   }
 }
 
-function pollContractForEvents(
+async function pollContractForEvents(
   fromBlock: number,
   toBlock: number | "latest",
   context: ChainContext
 ): Promise<ConditionalOrderCreatedEvent[]> {
   const { provider, chainId, addresses } = context;
   const composableCow = composableCowContract(provider, chainId);
-  const filter = composableCow.filters.ConditionalOrderCreated() as EventFilter;
+  const eventName = "ConditionalOrderCreated(address,(address,bytes32,bytes))";
+  const topic = ethers.utils.id(eventName);
 
-  if (addresses) {
-    filter.topics?.push(
-      addresses.map((address) => hexZeroPad(address.toLowerCase(), 32))
-    );
-  }
+  const logs = await provider.getLogs({
+    fromBlock,
+    toBlock,
+    topics: [topic],
+  });
 
-  return composableCow.queryFilter(filter, fromBlock, toBlock);
+  return logs
+    .map((event) => {
+      try {
+        const decoded = composableCow.interface.decodeEventLog(
+          topic,
+          event.data,
+          event.topics
+        ) as unknown as ConditionalOrderCreatedEvent;
+
+        return {
+          ...decoded,
+          ...event,
+        };
+      } catch {
+        return null;
+      }
+    })
+    .filter((e): e is ConditionalOrderCreatedEvent => e !== null)
+    .filter((e): e is ConditionalOrderCreatedEvent => {
+      return addresses ? addresses.includes(e.args.owner) : true;
+    });
 }
 
 function _formatResult(result: boolean) {

src/utils/contracts.ts

@@ -10,12 +10,6 @@ import {
 import { getLogger } from "./logging";
 import { metrics } from ".";
 
-// Selectors that are required to be part of the contract's bytecode in order to be considered compatible
-const REQUIRED_SELECTORS = [
-  "cabinet(address,bytes32)",
-  "getTradeableOrderWithSignature(address,(address,bytes32,bytes),bytes,bytes32[])",
-];
-
 // Define an enum for the custom error revert hints that can be returned by the ComposableCoW's interfaces.
 export enum CustomErrorSelectors {
   /**
@@ -117,30 +111,6 @@ export function abiToSelector(abi: string) {
   return ethers.utils.id(abi).slice(0, 10);
 }
 
-/**
- * Attempts to verify that the contract at the given address implements the interface of the `ComposableCoW`
- * contract. This is done by checking that the contract contains the selectors of the functions that are
- * required to be implemented by the interface.
- *
- * @remarks This is not a foolproof way of verifying that the contract implements the interface, but it is
- * a good enough heuristic to filter out most of the contracts that do not implement the interface.
- *
- * @dev The selectors are:
- * - `cabinet(address,bytes32)`: `1c7662c8`
- * - `getTradeableOrderWithSignature(address,(address,bytes32,bytes),bytes,bytes32[])`: `26e0a196`
- *
- * @param code the contract's deployed bytecode as a hex string
- * @returns A boolean indicating if the contract likely implements the interface
- */
-export function isComposableCowCompatible(code: string): boolean {
-  const composableCow = ComposableCoW__factory.createInterface();
-
-  return REQUIRED_SELECTORS.every((signature) => {
-    const sighash = composableCow.getSighash(signature);
-    return code.includes(sighash.slice(2));
-  });
-}
-
 export function composableCowContract(
   provider: ethers.providers.Provider,
   chainId: SupportedChainId

src/utils/utils.spec.ts

@@ -1,49 +1,13 @@
-import * as composableCow from "../../abi/ComposableCoW.json";
-import * as extensibleFallbackHandler from "../../abi/ExtensibleFallbackHandler.json";
 import {
   CUSTOM_ERROR_ABI_MAP,
   CustomErrorSelectors,
   abiToSelector,
   handleOnChainCustomError,
   initLogging,
-  isComposableCowCompatible,
   parseCustomError,
 } from ".";
 import { COMPOSABLE_COW_CONTRACT_ADDRESS } from "@cowprotocol/cow-sdk";
 
-// consts for readability
-const composableCowBytecode = composableCow.deployedBytecode.object;
-const failBytecode = extensibleFallbackHandler.deployedBytecode.object;
-
-describe("test supports composable cow interface from bytecode", () => {
-  it("should pass", () => {
-    expect(isComposableCowCompatible(composableCowBytecode)).toBe(true);
-  });
-
-  it("should fail", () => {
-    expect(isComposableCowCompatible(failBytecode)).toBe(false);
-  });
-});
-
-describe("test against concrete examples", () => {
-  const signatures = ["0x1c7662c8", "0x26e0a196"];
-
-  it("should pass with both selectors", () => {
-    expect(isComposableCowCompatible("0x1c7662c826e0a196")).toBe(true);
-  });
-
-  // using `forEach` here, be careful not to do async tests.
-  signatures.forEach((s) => {
-    it(`should fail with only selector ${s}`, () => {
-      expect(isComposableCowCompatible(s)).toBe(false);
-    });
-  });
-
-  it("should fail with no selectors", () => {
-    expect(isComposableCowCompatible("0xdeadbeefdeadbeef")).toBe(false);
-  });
-});
-
 describe("parse custom errors (reversions)", () => {
   it("should pass the SingleOrderNotAuthed selector correctly", () => {
     expect(parseCustomError(SINGLE_ORDER_NOT_AUTHED_ERROR)).toMatchObject({