First Flight #5: Santa's List
First Flight #5
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100 EXP
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Submission Details
Severity: high
Valid

Sybil attack caused by default enum Status

dcheng

Summary

The default value for any person in storage variables SantasList::s_theListCheckedOnce and SantasList::s_theListCheckedTwice is NICE. This results in anyone can call SantasList::collectPresent and mint an NFT. A malicious user can create multiple accounts and mint multiple NFTs.

Vulnerability Details

The default value for a enum type is it's first member, and in this case, the default value is NICE. SantasList::collectPresent function allows a user to mint a NFT if their address is marked NICE in storage variables s_theListCheckedOnce and s_theListCheckedTwice. Since the default value is NICE, anyone can mint a NFT. A malicious user can create multiple accounts and mint multiple NFTs.

Impact

Unlimited NFT mints

Forge test case

function testCanCollectPresentWithoutBeingChecked() public {
address randomUser = makeAddr("randomUser");
vm.warp(santasList.CHRISTMAS_2023_BLOCK_TIME() + 1);
assertEq(santasList.balanceOf(randomUser), 0);
vm.startPrank(randomUser);
santasList.collectPresent();
assertEq(santasList.balanceOf(randomUser), 1);
}

Tools Used

  • Foundry

Recommendations

Change first member of enum Status to NOT_CHECKED_TWICE

enum Status {
+ NOT_CHECKED_TWICE,
NICE,
EXTRA_NICE,
NAUGHTY,
- NOT_CHECKED_TWICE
}
Updates

Lead Judging Commences

inallhonesty Lead Judge almost 2 years ago
Submission Judgement Published
Validated
Assigned finding tags:

default status is nice

In Solidity the first element of an enum is the default value. In Santa's List, the means each person is mapped by default to 'NICE'.

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