Use of transfer() instead of call() to send eth

[code423n4]

Lines of code

https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L23
https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L51
https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L71
https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L86
https://github.com/code-423n4/2022-07-axelar/blob/3373c48a71c07cfce856b53afc02ef4fc2357f8c/contracts/gas-service/AxelarGasService.sol#L128
https://github.com/code-423n4/2022-07-axelar/blob/3373c48a71c07cfce856b53afc02ef4fc2357f8c/contracts/gas-service/AxelarGasService.sol#L144

Vulnerability details

Use of transfer() instead of call() to send eth

Impact

Use of transfer() might render ETH impossible to withdraw because after istanbul hardfork, there is increases in the gas cost of the SLOAD operation and therefore breaks some existing smart contracts. Those contracts will break because their fallback functions used to consume less than 2300 gas, and they’ll now consume more, since 2300 the amount of gas a contract’s fallback function receives if it’s called via Solidity’s transfer() or send() methods.

Any smart contract that uses transfer() or send() is taking a hard dependency on gas costs by forwarding a fixed amount of gas: 2300.

References

https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/
https://blog.openzeppelin.com/opyn-gamma-protocol-audit/

Proof of Concept

https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L23
https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L51
https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L71
https://github.com/code-423n4/2022-07-axelar/blob/a46fa61e73dd0f3469c0263bc6818e682d62fb5f/contracts/deposit-service/ReceiverImplementation.sol#L86
https://github.com/code-423n4/2022-07-axelar/blob/3373c48a71c07cfce856b53afc02ef4fc2357f8c/contracts/gas-service/AxelarGasService.sol#L128
https://github.com/code-423n4/2022-07-axelar/blob/3373c48a71c07cfce856b53afc02ef4fc2357f8c/contracts/gas-service/AxelarGasService.sol#L144

Recommended Mitigation Steps

Use call() to send eth

[GalloDaSballo]

See #203

[re1ro]

Duplicate of #4