fixed critical bug inside fee manager

Author: Nico205

.mocharc.json

@@ -0,0 +1,7 @@
+{
+  "require": "hardhat/register",
+  "timeout": 40000,
+  "_": [
+    "test/**/*.ts"
+  ]
+}

contracts/BaseDynamicFeeManager.sol

@@ -55,6 +55,9 @@ abstract contract BaseDynamicFeeManager is
     // Max. amount for fee entries
     uint256 public constant MAX_FEE_AMOUNT = 30;
 
+    // Min. amount for swap / liquify
+    uint256 public constant MIN_SWAP_OR_LIQUIFY_AMOUNT = 1 ether;
+
     // Fee divider
     uint256 internal constant FEE_DIVIDER = 100_000;
 
@@ -65,11 +68,11 @@ abstract contract BaseDynamicFeeManager is
     // List of all currently added fees
     FeeEntry[] internal feeEntries;
 
-    // Mapping id to current liquify or swap amounts
+    // Mapping id to current swap or liquify amounts
     mapping(bytes32 => uint256) internal feeEntryAmounts;
 
     // Fees enabled state
-    bool private _feesEnabled = false;
+    bool internal feesEnabled_ = false;
 
     // Pancake Router address
     IPancakeRouter02 private _pancakeRouter =
@@ -134,7 +137,7 @@ abstract contract BaseDynamicFeeManager is
     }
 
     function setFeesEnabled(bool value) external override onlyRole(ADMIN) {
-        _feesEnabled = value;
+        feesEnabled_ = value;
 
         emit FeeEnabledUpdated(value);
     }
@@ -251,7 +254,7 @@ abstract contract BaseDynamicFeeManager is
     }
 
     function feesEnabled() public view override returns (bool) {
-        return _feesEnabled;
+        return feesEnabled_;
     }
 
     function pancakeRouter()
@@ -472,17 +475,24 @@ abstract contract BaseDynamicFeeManager is
     /**
      * Returns the amount used for swap / liquify based on volume percentage for swap / liquify
      *
+     * @param feeId bytes32 - Fee entry id
      * @param swapOrLiquifyAmount uint256 - Fee entry swap or liquify amount
      * @param percentageVolume uint256 - Volume percentage for swap / liquify
      * @param pancakePairAddress address - Pancakeswap pair address to use for volume
      *
      * @return amount uint256 - Amount used for swap / liquify
      */
     function _getSwapOrLiquifyAmount(
+        bytes32 feeId,
         uint256 swapOrLiquifyAmount,
         uint256 percentageVolume,
         address pancakePairAddress
     ) internal view returns (uint256 amount) {
+        // If no percentage and fixed amount is set, use balance
+        if (percentageVolume == 0 && swapOrLiquifyAmount == 0) {
+            return feeEntryAmounts[feeId];
+        }
+
         if (pancakePairAddress == address(0) || percentageVolume == 0) {
             return swapOrLiquifyAmount;
         }
@@ -495,6 +505,16 @@ abstract contract BaseDynamicFeeManager is
         uint256 percentualAmount = (pancakePairTokenBalance *
             percentageVolume) / 100;
 
+        // If swap or liquify amount is zero, and percentual amount is
+        // higher than collected amount, return collected amount, otherwise
+        // return percentual amount
+        if (swapOrLiquifyAmount == 0) {
+            return
+                percentualAmount > feeEntryAmounts[feeId]
+                    ? feeEntryAmounts[feeId]
+                    : percentualAmount;
+        }
+
         // Do not exceed swap or liquify amount from fee entry
         if (percentualAmount >= swapOrLiquifyAmount) {
             return swapOrLiquifyAmount;

contracts/DynamicFeeManager.sol

@@ -159,6 +159,7 @@ contract DynamicFeeManager is BaseDynamicFeeManager {
      * @param to address - Receiver address
      * @param tFee uint256 - Fee amount
      * @param fee FeeEntry - Fee Entry
+     * @param bypassSwapAndLiquify bool - Indicator, if swap and liquify should be bypassed
      */
     function _reflectFee(
         address from,
@@ -192,24 +193,33 @@ contract DynamicFeeManager is BaseDynamicFeeManager {
         // Check if swap / liquify amount was reached
         if (
             !bypassSwapAndLiquify &&
+            feeEntryAmounts[fee.id] >= MIN_SWAP_OR_LIQUIFY_AMOUNT &&
             feeEntryAmounts[fee.id] >= fee.swapOrLiquifyAmount
         ) {
+            // Disable fees, to prevent PancakeSwap pair recursive calls
+            feesEnabled_ = false;
+
+            // Check if swap / liquify amount was reached
             uint256 tokenSwapped = 0;
 
-            if (fee.doSwapForBusd) {
+            if (fee.doSwapForBusd && from != pancakePairBusdAddress()) {
                 // Calculate amount of token we're going to swap
                 tokenSwapped = _getSwapOrLiquifyAmount(
+                    fee.id,
                     fee.swapOrLiquifyAmount,
                     percentageVolumeSwap(),
                     pancakePairBusdAddress()
                 );
 
                 // Swap token for BUSD
                 _swapTokensForBusd(tokenSwapped, fee.destination);
-            } else if (fee.doLiquify) {
+            }
+
+            if (fee.doLiquify) {
                 // Swap (BNB) and liquify token
                 tokenSwapped = _swapAndLiquify(
                     _getSwapOrLiquifyAmount(
+                        fee.id,
                         fee.swapOrLiquifyAmount,
                         percentageVolumeLiquify(),
                         pancakePairBnbAddress()
@@ -220,6 +230,9 @@ contract DynamicFeeManager is BaseDynamicFeeManager {
 
             // Subtract amount of swapped token from fee entry amount
             feeEntryAmounts[fee.id] = feeEntryAmounts[fee.id] - tokenSwapped;
+
+            // Enable fees again
+            feesEnabled_ = true;
         }
 
         // Check if callback should be called on destination
@@ -258,11 +271,9 @@ contract DynamicFeeManager is BaseDynamicFeeManager {
      *
      * @return isValid bool - Indicates, if the fee entry is still valid
      */
-    function _isFeeEntryValid(FeeEntry memory fee)
-        private
-        view
-        returns (bool isValid)
-    {
+    function _isFeeEntryValid(
+        FeeEntry memory fee
+    ) private view returns (bool isValid) {
         return fee.expiresAt == 0 || block.timestamp <= fee.expiresAt;
     }
 
@@ -302,11 +313,10 @@ contract DynamicFeeManager is BaseDynamicFeeManager {
      *
      * @return tFee - Total Fee Amount
      */
-    function _calculateFee(uint256 amount, uint256 percentage)
-        private
-        pure
-        returns (uint256 tFee)
-    {
+    function _calculateFee(
+        uint256 amount,
+        uint256 percentage
+    ) private pure returns (uint256 tFee) {
         return (amount * percentage) / FEE_DIVIDER;
     }
 

contracts/mocks/MockERC20.sol

@@ -8,6 +8,6 @@ import "@openzeppelin/contracts/access/Ownable.sol";
 
 contract MockERC20 is ERC20, Ownable {
     constructor() ERC20("MockERC20", "MERC20") {
-        _mint(_msgSender(), 100 ether);
+        _mint(_msgSender(), 100_000_000 ether);
     }
 }

contracts/mocks/MockPancakeRouter.sol

@@ -9,11 +9,27 @@ contract MockPancakeRouter {
     event MockEvent(uint256 value);
 
     address private immutable _weth;
-    address private immutable _pair;
 
-    constructor(address weth, address pair) {
+    // See https://github.com/pancakeswap/pancake-smart-contracts/blob/master/projects/exchange-protocol/contracts/PancakeFactory.sol#L13
+    mapping(address => mapping(address => address)) public getPair;
+
+    constructor(
+        address weth,
+        address busd,
+        address wsi,
+        address wethPair,
+        address busdPair
+    ) {
+        // BNB
         _weth = weth;
-        _pair = pair;
+
+        // BNB <-> WSI
+        getPair[weth][wsi] = wethPair;
+        getPair[wsi][weth] = wethPair;
+
+        // BUSD <-> WSI
+        getPair[busd][wsi] = busdPair;
+        getPair[wsi][busd] = busdPair;
     }
 
     function WETH() public view returns (address) {
@@ -36,7 +52,9 @@ contract MockPancakeRouter {
             uint256 liquidity
         )
     {
-        IERC20(token).transferFrom(msg.sender, _pair, amountTokenDesired);
+        address pair = getPair[_weth][token];
+
+        IERC20(token).transferFrom(msg.sender, pair, amountTokenDesired);
 
         return (amountTokenDesired, msg.value, 0);
     }
@@ -48,7 +66,13 @@ contract MockPancakeRouter {
         address to,
         uint256 deadline
     ) public {
-        IERC20(path[0]).transferFrom(msg.sender, _pair, amountIn);
+        require(amountIn > 0, "MockPancakeRouter: Invalid input amount");
+
+        address pair = getPair[path[0]][path[1]];
+
+        IERC20(path[0]).transferFrom(msg.sender, pair, amountIn);
+        // MockPancakePair(_pair).swap(path[1], address(0), amountIn);
+        payable(to).transfer(amountIn);
     }
 
     function swapExactETHForTokensSupportingFeeOnTransferTokens(
@@ -57,7 +81,10 @@ contract MockPancakeRouter {
         address to,
         uint256 deadline
     ) public payable {
-        MockPancakePair(_pair).swap(path[1], msg.sender, amountOutMin);
+        address pair = getPair[path[0]][path[1]];
+
+        IERC20(path[0]).transfer(pair, msg.value);
+        MockPancakePair(pair).swap(path[1], to, amountOutMin);
     }
 
     function swapExactTokensForTokensSupportingFeeOnTransferTokens(
@@ -67,6 +94,13 @@ contract MockPancakeRouter {
         address to,
         uint256 deadline
     ) public {
-        IERC20(path[0]).transferFrom(msg.sender, _pair, amountIn);
+        address pair = getPair[path[0]][path[1]];
+
+        IERC20(path[0]).transferFrom(msg.sender, pair, amountIn);
+        MockPancakePair(pair).swap(
+            path[1],
+            to,
+            amountOutMin > 0 ? amountOutMin : amountIn
+        );
     }
 }

hardhat.config.ts

@@ -45,6 +45,11 @@ const config: HardhatUserConfig = {
       accounts:
         process.env.PRIVATE_KEY !== undefined ? [process.env.PRIVATE_KEY] : [],
     },
+    hardhat: {
+      forking: {
+        url: process.env.BSC_GETBLOCK_URL || '',
+      }
+    }
   },
   gasReporter: {
     enabled: process.env.REPORT_GAS !== undefined,