Max approval erc20s

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+# 3.0.1
+
+### Upgrade steps
+
+Update `BackingManager`, both `RevenueTraders` (rTokenTrader/rsrTrader), and call `Broker.setBatchTradeImplementation()` passing in the new `GnosisTrade` address.
+
 # 3.0.0
 
 ### Upgrade Steps

contracts/libraries/Allowance.sol

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: BlueOak-1.0.0
+pragma solidity 0.8.19;
+
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+library AllowanceLib {
+    /// An approve helper that:
+    ///   1. Sets initial allowance to 0
+    ///   2. Tries to set the provided allowance
+    ///   3. Falls back to setting a maximum allowance, if (2) fails
+    /// Context: Some new-age ERC20s think it's a good idea to revert for allowances
+    /// that are > 0 but < type(uint256).max.
+    function safeApproveFallbackToMax(
+        IERC20 token,
+        address spender,
+        uint256 value
+    ) internal {
+        // 1. Set initial allowance to 0
+        require(token.approve(spender, 0), "failed to set 0 allowance");
+
+        if (value == 0) return;
+
+        // 2. Try to set the provided allowance
+        bool success; // bool success = false;
+        try token.approve(spender, value) returns (bool _success) {
+            success = _success;
+        } catch {}
+
+        // 3. Fall-back to setting a maximum allowance
+        if (!success) token.approve(spender, type(uint256).max);
+    }
+}

contracts/p0/mixins/Trading.sol

@@ -6,6 +6,7 @@ import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import "../../interfaces/IBroker.sol";
 import "../../interfaces/IMain.sol";
 import "../../interfaces/ITrade.sol";
+import "../../libraries/Allowance.sol";
 import "../../libraries/Fixed.sol";
 import "./Rewardable.sol";
 
@@ -68,8 +69,12 @@ abstract contract TradingP0 is RewardableP0, ITrading {
         IBroker broker = main.broker();
         assert(address(trades[req.sell.erc20()]) == address(0));
 
-        req.sell.erc20().safeApprove(address(broker), 0);
-        req.sell.erc20().safeApprove(address(broker), req.sellAmount);
+        // Set allowance via custom approval -- first sets allowance to 0, then sets allowance
+        // to either the requested amount or the maximum possible amount, if that fails.
+        //
+        // Context: wcUSDCv3 has a non-standard approve() function that reverts if the approve
+        // amount is > 0 and < type(uint256).max.
+        AllowanceLib.safeApproveFallbackToMax(req.sell.erc20(), address(broker), req.sellAmount);
 
         trade = broker.openTrade(kind, req, prices);
         trades[req.sell.erc20()] = trade;

contracts/p1/mixins/Trading.sol

@@ -7,6 +7,7 @@ import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import "@openzeppelin/contracts/utils/Multicall.sol";
 import "../../interfaces/ITrade.sol";
 import "../../interfaces/ITrading.sol";
+import "../../libraries/Allowance.sol";
 import "../../libraries/Fixed.sol";
 import "./Component.sol";
 import "./RewardableLib.sol";
@@ -120,8 +121,12 @@ abstract contract TradingP1 is Multicall, ComponentP1, ReentrancyGuardUpgradeabl
         IERC20 sell = req.sell.erc20();
         assert(address(trades[sell]) == address(0));
 
-        IERC20Upgradeable(address(sell)).safeApprove(address(broker), 0);
-        IERC20Upgradeable(address(sell)).safeApprove(address(broker), req.sellAmount);
+        // Set allowance via custom approval -- first sets allowance to 0, then sets allowance
+        // to either the requested amount or the maximum possible amount, if that fails.
+        //
+        // Context: wcUSDCv3 has a non-standard approve() function that reverts if the approve
+        // amount is > 0 and < type(uint256).max.
+        AllowanceLib.safeApproveFallbackToMax(req.sell.erc20(), address(broker), req.sellAmount);
 
         trade = broker.openTrade(kind, req, prices);
         trades[sell] = trade;

contracts/plugins/trading/GnosisTrade.sol

@@ -4,6 +4,7 @@ pragma solidity 0.8.19;
 import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
 import "@openzeppelin/contracts/utils/math/Math.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/utils/SafeERC20Upgradeable.sol";
+import "../../libraries/Allowance.sol";
 import "../../libraries/Fixed.sol";
 import "../../interfaces/IBroker.sol";
 import "../../interfaces/IGnosis.sol";
@@ -130,9 +131,12 @@ contract GnosisTrade is ITrade {
 
         // == Interactions ==
 
-        // Set allowance (two safeApprove calls to support USDT)
-        IERC20Upgradeable(address(sell)).safeApprove(address(gnosis), 0);
-        IERC20Upgradeable(address(sell)).safeApprove(address(gnosis), initBal);
+        // Set allowance via custom approval -- first sets allowance to 0, then sets allowance
+        // to either the requested amount or the maximum possible amount, if that fails.
+        //
+        // Context: wcUSDCv3 has a non-standard approve() function that reverts if the approve
+        // amount is > 0 and < type(uint256).max.
+        AllowanceLib.safeApproveFallbackToMax(sell, address(gnosis), initBal);
 
         auctionId = gnosis.initiateAuction(
             sell,