Missing nonreentrant modifier on various yield source functions making external calls

[code423n4]

Handle

0xRajeev

Vulnerability details

Impact

Many contracts use OpenZeppelin’s nonreentrant modifier on functions that interact with external contracts to prevent any reentrancies possible. However, there are a few functions that miss using this modifier.

Impact: Missing nonreentrant modifier may allow reentrancy although the risk is low given that most external contracts are “trusted” ones from the project itself or well-known yield sources. Although, there are a few functions that make calls to unknown/untrusted erc20 tokens but they seem to follow the CEI pattern currently. It is nevertheless safer to add the modifier for consistency given this is used everywhere else, at the cost of some extra gas.

Proof of Concept

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/ATokenYieldSource.sol#L224

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/ATokenYieldSource.sol#L233

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/IdleYieldSource.sol#L150

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/BadgerYieldSource.sol#L43

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/BadgerYieldSource.sol#L57

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/SushiYieldSource.sol#L47

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/SushiYieldSource.sol#L66

Tools Used

Manual Analysis

Recommended Mitigation Steps

Add missing nonreentrant modifier on all functions with external calls.

[asselstine]

See #119