Aave DIVA Wrapper
DIVA
HardhatDeFi
15,000 USDC
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Submission Details
Severity: medium
Invalid

type(uint256).max approval causes revert in certain tokens

wellbyt3

Summary

The protocol attempts to approve type(uint256).max for collateral tokens, but since tokens like UNI enforces a 96-bit limit on approvals, this call will always revert, preventing tokens like UNI from being registered as a collateral token even though they are supported by Aave.

Vulnerability Details

The protocol states in the README that supported collateral tokens are:

Any ERC20 token supported by Aave V3, but mainly stablecoins like USDC, USDT are expected to be used for DIVA Donate.

UNI is a token supported by Aave. When UNI.approve() is called, UNI reverts if the approval amount is 2^96 or larger. Here's the code from the UNI contract on Ethereum:

function approve(address spender, uint rawAmount) external returns (bool) {
uint96 amount;
if (rawAmount == uint(-1)) {
amount = uint96(-1);
} else {
@> amount = safe96(rawAmount, "Uni::approve: amount exceeds 96 bits");
}
​
allowances[msg.sender][spender] = amount;
​
emit Approval(msg.sender, spender, amount);
return true;
}
​
function safe96(uint n, string memory errorMessage) internal pure returns (uint96) {
@> require(n < 2**96, errorMessage);
return uint96(n);
}
​
​

https://etherscan.io/address/0x1f9840a85d5af5bf1d1762f925bdaddc4201f984#code

In AaveDIVAWrapperCore::_registerCollateralToken, type(uint256).max is passed as the approval amount for collateral token which will always revert when trying to register UNI as a collateral token:

function _registerCollateralToken(address _collateralToken) internal returns (address) {
...
​
@> _collateralTokenContract.approve(_aaveV3Pool, type(uint256).max);
​
...
}
​

Impact

Tokens like UNI that are Aave supported aren't compatible with the protocol.

Tools Used

Manual review

Recommendations

If you want to really support all tokens Aave supports, use uint96 - 1 and then update the increase allowance functions to increase to uint96 - 1

Updates

Lead Judging Commences

bube Lead Judge 10 months ago
Submission Judgement Published
Invalidated
Reason: Known issue

Appeal created

bube Lead Judge 10 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement

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