NICE is enum member 0, so every unwritten mapping slot is already a passing verdict — any address mints a present with no grading
## [H-1] `NICE` is enum member 0, so every unwritten mapping slot is already a passing verdict — any address mints a present with no grading
**Impact:** High · **Likelihood:** High
### Description
- A present is meant to be earned. The specification states that *"in order for someone to be
considered `NICE` or `EXTRA_NICE` they **must** be first 'checked twice' by Santa"*, and
`collectPresent` reads both status mappings to enforce it.
- `Status` declares `NICE` first, so `NICE == 0`, and `0` is what every unwritten mapping slot
returns. Both mappings already read `NICE` for every address in existence, which is exactly the
branch condition at `:154`. Santa's grading confers nothing the default does not already confer.
```solidity
// src/SantasList.sol:69-74
enum Status {
@> NICE, // member 0 — the default value of every unwritten slot
EXTRA_NICE,
NAUGHTY,
NOT_CHECKED_TWICE
}
// src/SantasList.sol:79-80
mapping(address person => Status naughtyOrNice) private s_theListCheckedOnce;
mapping(address person => Status naughtyOrNice) private s_theListCheckedTwice;
// src/SantasList.sol:154
@> if (s_theListCheckedOnce[msg.sender] == Status.NICE && s_theListCheckedTwice[msg.sender] == Status.NICE) {
_mintAndIncrement();
return;
}
```
### Risk
**Likelihood:**
- Every address on the chain satisfies the branch at `:154` from the moment the contract is
deployed, with no transaction sent and no state written.
- `collectPresent` is `external` with no modifier, and the only other gate — `block.timestamp >=
CHRISTMAS_2023_BLOCK_TIME` — passed on 2023-12-25.
**Impact:**
- Presents are minted from unlimited fresh addresses for gas alone. The PoC mints 100 against 2
legitimately graded users.
- The issuance is irreversible: there is no burn function, no cap, no pause, no owner, and no
upgrade path. `i_santa` and `i_santaToken` are `immutable` with no setters.
Bounded: this path yields the NFT and **no `SantaToken`**. `EXTRA_NICE` is member 1, not a
default, and is writable only through the `onlySanta`-gated `checkTwice`.
### Proof of Concept
```solidity
function test_F01_freeMint() public {
address freshAttacker = makeAddr("freshAttacker"); // never graded, never seen by Santa
vm.warp(1_703_480_381); // Christmas 2023
assertEq(uint256(list.getNaughtyOrNiceOnce(freshAttacker)), uint256(SantasList.Status.NICE));
assertEq(uint256(list.getNaughtyOrNiceTwice(freshAttacker)), uint256(SantasList.Status.NICE));
vm.prank(freshAttacker);
list.collectPresent(); *// no checkList, no privilege, no capital*
assertEq(list.balanceOf(freshAttacker), 1);
}
```
### Recommended Mitigation
```diff
- enum Status { NICE, EXTRA_NICE, NAUGHTY, NOT_CHECKED_TWICE }
+ enum Status { NOT_CHECKED_TWICE, NICE, EXTRA_NICE, NAUGHTY }
```
Any equivalent works — gate on `s_theListCheckedTwice[msg.sender] != Status.NOT_CHECKED_TWICE`, or
add an explicit `mapping(address => bool) s_graded`. A verdict must not be the default value of an
unwritten slot.
Lead Judging Commences
[H-02] All addresses are considered `NICE` by default and are able to claim a NFT through `collectPresent` function before any Santa check.
## Description `collectPresent` function is supposed to be called by users that are considered `NICE` or `EXTRA_NICE` by Santa. This means Santa is supposed to call `checkList` function to assigned a user to a status, and then call `checkTwice` function to execute a double check of the status. Currently, the enum `Status` assigns its default value (0) to `NICE`. This means that both mappings `s_theListCheckedOnce` and `s_theListCheckedTwice` consider every existent address as `NICE`. In other words, all users are by default double checked as `NICE`, and therefore eligible to call `collectPresent` function. ## Vulnerability Details The vulnerability arises due to the order of elements in the enum. If the first value is `NICE`, this means the enum value for each key in both mappings will be `NICE`, as it corresponds to `0` value. ## Impact The impact of this vulnerability is HIGH as it results in a flawed mechanism of the present distribution. Any unchecked address is currently able to call `collectPresent` function and mint an NFT. This is because this contract considers by default every address with a `NICE` status (or 0 value). ## Proof of Concept The following Foundry test will show that any user is able to call `collectPresent` function after `CHRISTMAS_2023_BLOCK_TIME` : ``` function testCollectPresentIsFlawed() external { // prank an attacker's address vm.startPrank(makeAddr("attacker")); // set block.timestamp to CHRISTMAS_2023_BLOCK_TIME vm.warp(1_703_480_381); // collect present without any check from Santa santasList.collectPresent(); vm.stopPrank(); } ``` ## Recommendations I suggest to modify `Status` enum, and use `UNKNOWN` status as the first one. This way, all users will default to `UNKNOWN` status, preventing the successful call to `collectPresent` before any check form Santa: ``` enum Status { UNKNOWN, NICE, EXTRA_NICE, NAUGHTY } ``` After modifying the enum, you can run the following test and see that `collectPresent` call will revert if Santa didn't check the address and assigned its status to `NICE` or `EXTRA_NICE` : ``` function testCollectPresentIsFlawed() external { // prank an attacker's address vm.startPrank(makeAddr("attacker")); // set block.timestamp to CHRISTMAS_2023_BLOCK_TIME vm.warp(1_703_480_381); // collect present without any check from Santa vm.expectRevert(SantasList.SantasList__NotNice.selector); santasList.collectPresent(); vm.stopPrank(); } ```
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