`call()` should be used instead of `transfer()` on an `address payable`

[code423n4]

Lines of code

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/ethregistrar/ETHRegistrarController.sol#L183 https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/ethregistrar/ETHRegistrarController.sol#L204 https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/ethregistrar/ETHRegistrarController.sol#L211

Vulnerability details

This is a classic Code4rena issue:

• https://github.com/code-423n4/2021-04-meebits-findings/issues/2
• https://github.com/code-423n4/2021-10-tally-findings/issues/20
• https://github.com/code-423n4/2022-01-openleverage-findings/issues/75

Impact

The use of the deprecated transfer() function for an address will inevitably make the transaction fail when:

1. The claimer smart contract does not implement a payable function.
2. The claimer smart contract does implement a payable fallback which uses more than 2300 gas unit.
3. The claimer smart contract 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.

Impacted lines:

ethregistrar/ETHRegistrarController.sol:183:            payable(msg.sender).transfer(
ethregistrar/ETHRegistrarController.sol:204:            payable(msg.sender).transfer(msg.value - price.base);
ethregistrar/ETHRegistrarController.sol:211:        payable(owner()).transfer(address(this).balance);

Recommended Mitigation

Use call() instead of transfer(), but be sure to respect the CEI pattern and/or add re-entrancy guards, as several hacks already happened in the past due to this recommendation not being fully understood.

Relevant links: https://twitter.com/hacxyk/status/1520715516490379264?s=21&t=fnhDkcC3KpE_kJE8eLiE2A https://twitter.com/hacxyk/status/1520715536325218304?s=21&t=fnhDkcC3KpE_kJE8eLiE2A https://twitter.com/hacxyk/status/1520370441705037824?s=21&t=fnhDkcC3KpE_kJE8eLiE2A https://twitter.com/Hacxyk/status/1521949933380595712

[jefflau]

Duplicate of #133