Canto Dex Oracle contest - ignacio's results

#1 ABI.ENCODEPACKED() SHOULD NOT BE USED WITH DYNAMIC TYPES WHEN PASSING THE RESULT TO A HASH FUNCTION SUCH AS KECCAK256()

Use abi.encode() instead which will pad items to 32 bytes, which will prevent hash collisions (e.g. abi.encodePacked(0x123,0x456) => 0x123456 => abi.encodePacked(0x1,0x23456), but abi.encode(0x123,0x456) => 0x0...1230...456). “Unless there is a compelling reason, abi.encode should be preferred”. If there is only one argument to abi.encodePacked() it can often be cast to bytes() or bytes32() instead.

https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-periphery.sol#L103 https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-periphery.sol#L597 https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-core.sol#L603 #2 A miner can manipulate the block timestamp which can be used to their advantage to attack a smart contract via Block Timestamp Manipulation

https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-core.sol#L138 https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-core.sol#L159 https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-core.sol#L176 Blocks have a timestamp field in the block header which is set by the miner and can be changed to whatever they want (with some restriction). In order for a miner to set a block timestamp they need to win the next block and abide by the following time constrains:

The next timestamp is after the last block timestamp The timestamp can not be too far into the future If the miner wins a block they can slightly change the block timestamp to their advantage.

Impact

Dishonest Miners can influence the value of block.timestamp to perform Maximal Extractable Value (MEV) attacks. The use of now creates a risk that time manipulation can be performed to manipulate price oracles. Miners can modify the timestamp by up to 900 seconds , Usually to an extent of few seconds on Ethereum, or generally few percent of the block time on any EVM-compatible PoW network.

Recommended Mitigation Steps

Use block.number instead of block.timestamp or now to reduce the risk of MEV attacks Block timestamps should not be used for entropy or generating random numbers—i.e., they should not be the deciding factor (either directly or through some derivation) for changing an important state.

Time-sensitive logic is sometimes required; e.g., for unlocking contracts (time-locking), completing an ICO after a few weeks, or enforcing expiry dates. It is sometimes recommended to use block.number and an average block time to estimate times; with a 10 second block time, 1 week equates to approximately, 60480 blocks. Thus, specifying a block number at which to change a contract state can be more secure, as miners are unable to easily manipulate the block number.

here some reference :

https://www.bookstack.cn/read/ethereumbook-en/spilt.14.c2a6b48ca6e1e33c.md https://ethereum.stackexchange.com/questions/108033/what-do-i-need-to-be-careful-about-when-using-block-timestamp

#3 USE SAFETRANSFER/SAFETRANSFERFROM CONSISTENTLY INSTEAD OF TRANSFER/TRANSFERFROM It is good to add a require() statement that checks the return value of token transfers or to use something like OpenZeppelin’s safeTransfer/safeTransferFrom unless one is sure the given token reverts in case of a failure. Failure to do so will cause silent failures of transfers and affect token accounting in contract. https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-periphery.sol#L475 Recommended Mitigation Steps Consider using safeTransfer/safeTransferFrom or require() consistently #4 RETURN VALUES OF TRANSFER()/TRANSFERFROM() NOT CHECKED Not all IERC20 implementations revert() when there’s a failure in transfer()/transferFrom(). The function signature has a boolean return value and they indicate errors that way instead. By not checking the return value, operations that should have marked as failed, may potentially go through without actually making a payment https://github.com/code-423n4/2022-09-canto/blob/main/src/Swap/BaseV1-periphery.sol#L475