Holograph contest - cryptphi's results

Lines of code

https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/HolographBridge.sol#L274-L282 https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/HolographOperator.sol#L593 https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/module/LayerZeroModule.sol#L293

Vulnerability details

Impact

When a user creates a beam request for a destination chain, the user can input zero as a value for gasLimit. With this, the user is able to make the request without paying any fees to Hologram since messagingModule.getHlgFee(toChain, gasLimit, gasPrice); would return 0 in https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/HolographOperator.sol#L593

Proof of Concept

1. Alice calls HolographBridge.bridgeOutRequest() to send a beam request with gasLimit as 0.
2. The call moves on to HolographOperator.send() where the hlgFee returns 0 in the call to getHlgFee() in the messagingmodule contract https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/module/LayerZeroModule.sol#L293
3. A call to send function in the messaging module with full amount from msg.value without any deductible fees.
4. No hlgfee is transfered to the hToken contract.

Tools Used

Manual review

Recommended Mitigation Steps

Add a zero value check.

Lines of code

https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/HolographOperator.sol#L596 https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/enforcer/PA1D.sol#L396

Vulnerability details

Impact

The use of the deprecated transfer() function for an address will inevitably make the transaction fail when the caller is a smart contract and:

1. Does not implement a payable function.
2. Implements a payable fallback which uses more than 2300 gas unit.
3. Implements a payable fallback function that needs less than 2300 gas units but is called through proxy, raising the call's gas usage above 2300.

Additionally, using higher than 2300 gas might be mandatory for some multisig wallets.

Proof of Concept

https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/HolographOperator.sol#L596 https://github.com/code-423n4/2022-10-holograph/blob/main/contracts/enforcer/PA1D.sol#L396

Tools Used

Manual review

Recommended Mitigation Steps

using call() instead of transfer() is recommended as suggested in https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/