CrossChainBridge

Smart Contract Security Analysis

Published on : Jan 28, 2022
Version v1.0

TABLE OF CONTENTS

3 Issues (1 Critical, 0 Major, 2 Minor) Found

TABLE OF CONTENTS

ABOUT US

INTRODUCTION

SUMMARY

OVERVIEW

FINDINGS

Front running attack is possible using the CrossChainBridgeERC20V1#releaseNative() function.        (Found - v1.0).

It is advised to define the wrappedNative() function of the router as a view function.

The parameter of the LiquidityRemoved event that occurs in the CrossChainBridgeERC20LiquidityManagerV1#_withdrawLiquidityERC20() function may fail to return a normal value.

DISCLAIMER

Appendix A. Test Results

ABOUT US

HAECHI AUDIT is a flagship service of HAECHI LABS, the leader of the global blockchain industry. HAECHI AUDIT provides specialized and professional smart contract security auditing and development services.

We are a team of experts with years of experience in the blockchain field and have been trusted by 300+ project groups. Our notable partners include Universe,1inch, Klaytn, Badger, etc.

HAECHI AUDIT is the only blockchain technology company selected for the Samsung Electronics Startup Incubation Program in recognition of our expertise. We have also received technology grants from the Ethereum Foundation and Ethereum Community Fund. 

Inquiries : audit@haechi.io 
Website : audit.haechi.io

INTRODUCTION

HAECHI AUDIT recommends that CrossChainBridge team improve all issues discovered.  The following issue explanation uses the format of {file name}#{line number}, {contract name}#{function/variable name} to specify the code. For instance, Sample.sol:20  points to the 20th line of Sample.sol file, and Sample#fallback() means the fallback() function of the Sample contract.

Please refer to the Appendix to check all results of the tests conducted for this report. 

SUMMARY

OVERVIEW

Contracts subject to audit

• BridgeChefV1
• BuyBackAndBurn
• CrossChainBridgeERC20LiqudityManagerV1
• CrossChainBridgeERC20V1
• CrossChainBridgeERC721V!
• LiquidityMiningPoolsV1
• MultiSignatureOracleV1
• RewardPoolsV1
• RouterBSCPancakeV1
• RouterETHUniswapV1
• RouterPOLYSushiV1
• Bridge
• MintableERC20
• MintableERC721
• PoolsInterestBearingToken
• MyPausable
• MyPausableUpgradeable

FINDINGS

Front running attack is possible using the CrossChainBridgeERC20V1#releaseNative() function. (Found - v.1.0)

 /**

  * @notice Releases native tokens in this network that were deposited in another network

  *         (effectively completing a bridge transaction)

  *

  * @param sigV Array of recovery Ids for the signature

  * @param sigR Array of R values of the signatures

  * @param sigS Array of S values of the signatures

  * @param receiverAddress The account to receive the tokens

  * @param sourceNetworkTokenAddress the address of the ERC20 contract in the network the deposit was made

  * @param amount The amount of tokens to be released

  * @param depositChainId chain ID of the network in which the deposit was made

  * @param depositNumber The identifier of the corresponding deposit

  * @dev emits event TokensReleased after successful release

  */

 function releaseNative(

   uint8[] memory sigV,

   bytes32[] memory sigR,

   bytes32[] memory sigS,

   address receiverAddress,

   address sourceNetworkTokenAddress,

   uint256 amount,

   uint256 depositChainId,

   uint256 depositNumber

 ) external nonReentrant {

   // release wrapped native (ERC20) tokens from bridge without transferring them

   // tokens will be swapped from ERC20 to native token in the following steps

   uint256 releaseAmountAfterFees = _releaseERC20(

     sigV,

     sigR,

     sigS,

     receiverAddress,

     sourceNetworkTokenAddress,

     amount,

     depositChainId,

     depositNumber,

     true

   );

   // check native token balance before ERC20-to-native swap

   uint256 contractBalance = address(this).balance;

   // swap wrapped native ERC20 token back to native token

   wrappedNative.withdraw(releaseAmountAfterFees);

   // check if native token balance has increased by release amount

   require(

     address(this).balance == contractBalance + releaseAmountAfterFees,

     'CrossChainBridgeERC20: error while unwrapping native tokens'

   );

   // send native token back to user

   payable(_msgSender()).transfer(releaseAmountAfterFees);

 }

[https://github.com/HAECHI-LABS/CrosschainBridge-audit/blob/de43c5b8e2c8fbf4690f04a50b44fe02d73b8d6d/contracts/CrossChainBridgeERC20V1.sol#L241-L293]

Issue

The CrossChainBridgeERC20V1#releaseNative() deposits the native token of network A in the network and then withdraws the native token in network B via the signature of multi oracle. However, the multi oracle signature contains the receiver address, it sends the native token of the current network to msg.sender when the signature is verified.

Thus, when a user who actually intends to move a native token between networks through the bridge sends the CrossChainBridgeERC20V1#releaseNative() function to txPool, another user can perform a front running attack by initiating the transaction first to obtain the native token.

Recommendation

We recommend changing the logic to send the native token of the current network to the receiver address included in the signature if the signature verification from multi oracle is completed.

It is advised to define the wrappedNative() function of the router as a view function.

(Found - v.1.0)

 /**

  * @notice Returns the address of the wrapped native token that is used by the dex

  */

 function wrappedNative() external override returns (address) {

   return pancakeRouter.WETH();

 }

[https://github.com/HAECHI-LABS/CrosschainBridge-audit/blob/de43c5b8e2c8fbf4690f04a50b44fe02d73b8d6d/contracts/router/RouterBSCPancakeV1.sol#L78-L83]

 /**

  * @notice Returns the address of the wrapped native token that is used by the dex router

  */

 function wrappedNative() external override returns (address) {

   return uniswapRouter.WETH();

 }

[https://github.com/HAECHI-LABS/CrosschainBridge-audit/blob/de43c5b8e2c8fbf4690f04a50b44fe02d73b8d6d/contracts/router/RouterETHUniswapV1.sol#L78-L83]

 /**

  * @notice Returns the address of the wrapped native token that is used by the dex

  */

 function wrappedNative() external override returns (address) {

   return sushiSwapRouter.WETH();

 }

[https://github.com/HAECHI-LABS/CrosschainBridge-audit/blob/de43c5b8e2c8fbf4690f04a50b44fe02d73b8d6d/contracts/router/RouterPOLYSushiV1.sol#L78-L83]

Issue

The RouterBSCPancakeV1#wrappedNatvie(), RouterETHUniswapV1#wrappedNatvie(), and  RouterPOLYSushiV1#wrappedNatvie() functions are external functions that return the address of the wrapped native token in each network. However, because they are not declared as a view function, the return value cannot be obtained.

Recommendation

We advise adding a statement to request a claim to the connected pool even when the DCBVault#withdraw() function is called.

The parameter of the LiquidityRemoved event that occurs in the CrossChainBridgeERC20LiquidityManagerV1#_withdrawLiquidityERC20() function may fail to return a normal value.

(Found - v.1.0)

 /**

  * @notice Removes ERC20 liquidity from a pool

  *         Private interface to this function which allows internal calls from reentrancy guard protected functions

  *

  * @param token the token for which liquidity should be removed from this pool

  * @param amount the amount of liquidity to be removed

  * @dev emits event LiquidityRemoved

  */

 function _withdrawLiquidityERC20(IERC20 token, uint256 amount)

   private

   whenNotPaused

   returns (uint256 withdrawalAmount)

 {

   require(amount > 0, 'LiquidityManager: amount cannot be 0');

   // check if liquidity is sufficient for withdrawal

   require(token.balanceOf(address(bridgeERC20)) >= amount, 'LiquidityManager: not enough liquidity in bridge');

   // determine the fee rate to be used for this transaction (usually default liquidity withdrawal fee)

   uint256 liquidityWithdrawalFee = defaultLiquidityWithdrawalFee;

   // if a specific fee rate is stored for this particular release token then we use this rate instead

   if (liquidityWithdrawalFees[address(token)] > 0) {

     liquidityWithdrawalFee = liquidityWithdrawalFees[address(token)];

   }

   // calculate the fee amounts (dividing by 1.000.000 since the fee rate is provided as parts per million [ppm])

   // calculate the total fee amount for this transaction

   uint256 withdrawalFeeAmount = (amount * liquidityWithdrawalFee) / 1000000;

   // calculate the remaining amount that will be released to the user

   withdrawalAmount = amount - withdrawalFeeAmount;

   // transfer developer account fee, if applicable

   if (devAddr != address(0) && withdrawalFeeAmount > 0) {

     token.safeTransferFrom(address(bridgeERC20), devAddr, withdrawalFeeAmount);

   }

[https://github.com/HAECHI-LABS/CrosschainBridge-audit/blob/de43c5b8e2c8fbf4690f04a50b44fe02d73b8d6d/contracts/router/RouterPOLYSushiV1.sol#L78-L83]

Issue

The CrossChainBridgeERC20LiquidityManagerV1#_withdrawLiquidityERC20() function is called from the functions CrossChainBridgeERC20LiquidityManagerV1#withdrawLiquidityNative() and CrossChainBridgeERC20LiquidityManagerV1#withdrawLiquidityERC20(), and is also a function that withdraws some of the deposited tokens. In the case of a deposit, liquidity is added as much as the amount of the deposited token, and the amount parameter of the LiquidityRemoved event is also entered as the amount of the deposited token.

However, for withdrawal, the amount excluding the fee from the withdrawal amount enters the parameter of the LiquidityRemoved event even though liquidity is removed by the amount of tokens to be withdrawn

Recommendation

We recommend modifying the event to occur with the amount including withdrawalFee in the amount parameter of the LiquidityRemoved event.

DISCLAIMER

Appendix A. Test Results

The following results show the unit test results covering the key logic of the smart contract subject to the security audit. Parts marked in red are test cases that failed to pass the test due to existing issues.

End of Document