Aptos Pizza Drop
Cyfrin
Beginner FriendlyGameFi
100 EXP
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Submission Details
Impact: low
Likelihood: medium
Invalid

# Redundant Logic in has_claimed_slice Function

wojack0x0

Root Cause + Impact

The has_claimed_slice() function contains redundant and inefficient logic that performs the same table lookup twice, leading to unnecessary gas consumption and potential confusion.

Description

The normal behavior should be to check if a user has claimed their pizza slice by looking up their address in the claimed_users table once and returning the result.

The specific issue is that the function performs the same table::contains() operation twice - once in the if condition and again in the return statement, which is redundant and wastes gas.

// Root cause in the codebase
#[view]
public fun has_claimed_slice(user: address): bool acquires ModuleData, State {
let state = borrow_global<State>(get_resource_address());
@> if (!table::contains(&state.claimed_users, user)) {
@> return false
@> };
@> table::contains(&state.claimed_users, user) // Redundant check
}

Risk

Likelihood: High

  • This inefficiency occurs every time the function is called

  • The redundant logic is always executed when the user has claimed

  • Gas waste accumulates with frequent view function calls

Impact: Low

  • Unnecessary gas consumption for view function calls

  • Code maintainability issues due to redundant logic

  • Potential confusion for developers reading the code

  • No security risk, but impacts efficiency

Proof of Concept (PoC)

To concretely demonstrate the inefficiency, a dedicated test case, test_redundant_logic_in_has_claimed_slice, was developed. This test contrasts the behavior of the function when called for a user who has claimed versus one who has not. The debug output serves as a clear, step-by-step analysis, quantifying the performance impact.

Setup

Add the following test case to the end of the sources/pizza_drop.move file.

Test Code

#[test(deployer = @pizza_drop, user1 = @0x123, user2 = @0x456, framework = @0x1)]
fun test_redundant_logic_in_has_claimed_slice(
deployer: &signer,
user1: &signer,
user2: &signer,
framework: &signer
) acquires State, ModuleData {
use aptos_framework::account;
use aptos_framework::timestamp;
use aptos_framework::aptos_coin;
// Setup test environment
timestamp::set_time_has_started_for_testing(framework);
let (burn_cap, mint_cap) = aptos_coin::initialize_for_test(framework);
account::create_account_for_test(@pizza_drop);
account::create_account_for_test(signer::address_of(user1));
account::create_account_for_test(signer::address_of(user2));
​
debug::print(&b"\n======================================================");
debug::print(&b" REDUNDANT LOGIC VULNERABILITY TEST");
debug::print(&b"======================================================");
// Initialize the contract
init_module(deployer);
let user1_addr = signer::address_of(user1);
let user2_addr = signer::address_of(user2);
debug::print(&b"\n[PHASE 1] Testing Unclaimed User Behavior");
debug::print(&b"------------------------------------------");
// Test unclaimed user (should use 1 table lookup)
let has_claimed_unclaimed = has_claimed_slice(user1_addr);
debug::print(&b"User1 (unclaimed) has_claimed_slice result: ");
debug::print(&has_claimed_unclaimed);
debug::print(&b"[OK] Expected: false (1 table lookup - efficient)");
assert!(!has_claimed_unclaimed, 1);
debug::print(&b"\n[PHASE 2] Setting Up Claimed User");
debug::print(&b"----------------------------------");
// Register and fund users
register_pizza_lover(deployer, user1_addr);
register_pizza_lover(deployer, user2_addr);
let funding_amount = 200000;
aptos_coin::mint(framework, @pizza_drop, funding_amount);
fund_pizza_drop(deployer, funding_amount);
// User1 claims their slice
claim_pizza_slice(user1);
debug::print(&b"[OK] User1 successfully claimed their pizza slice");
debug::print(&b"\n[PHASE 3] Testing Claimed User Behavior");
debug::print(&b"----------------------------------------");
// Test claimed user (uses 2 table lookups - INEFFICIENT)
let has_claimed_claimed = has_claimed_slice(user1_addr);
debug::print(&b"User1 (claimed) has_claimed_slice result: ");
debug::print(&has_claimed_claimed);
debug::print(&b"[WARNING] INEFFICIENCY: This required 2 table lookups!");
assert!(has_claimed_claimed, 2);
debug::print(&b"\n[PHASE 4] Comparative Analysis");
debug::print(&b"-------------------------------");
// Test both scenarios for comparison
debug::print(&b"Testing multiple calls to demonstrate gas waste:");
// Multiple calls for unclaimed user (efficient)
debug::print(&b"\n> Unclaimed user (User2) - 5 calls:");
let i = 0;
while (i < 5) {
let result = has_claimed_slice(user2_addr);
debug::print(&b" Call ");
debug::print(&(i + 1));
debug::print(&b": ");
debug::print(&result);
debug::print(&b" (1 lookup each)");
i = i + 1;
};
debug::print(&b" Total: 5 table lookups for 5 calls");
// Multiple calls for claimed user (inefficient)
debug::print(&b"\n> Claimed user (User1) - 5 calls:");
let j = 0;
while (j < 5) {
let result = has_claimed_slice(user1_addr);
debug::print(&b" Call ");
debug::print(&(j + 1));
debug::print(&b": ");
debug::print(&result);
debug::print(&b" (2 lookups each!)");
j = j + 1;
};
debug::print(&b" Total: 10 table lookups for 5 calls");
debug::print(&b"\n[VULNERABILITY ANALYSIS]");
debug::print(&b"========================");
debug::print(&b"\n[ROOT CAUSE]:");
debug::print(&b" The has_claimed_slice() function contains redundant logic:");
debug::print(&b" ");
debug::print(&b" if (!table::contains(&state.claimed_users, user)) {");
debug::print(&b" return false; // <- First table lookup");
debug::print(&b" };");
debug::print(&b" table::contains(&state.claimed_users, user) // <- Second lookup!");
debug::print(&b"\n[PERFORMANCE IMPACT]:");
debug::print(&b" - Unclaimed users: 1 table lookup (efficient)");
debug::print(&b" - Claimed users: 2 table lookups (100% overhead!)");
debug::print(&b" - Gas waste: Doubles lookup cost for claimed users");
debug::print(&b"\n[RECOMMENDED FIX]:");
debug::print(&b" Simply return: table::contains(&state.claimed_users, user)");
debug::print(&b" This eliminates redundant logic and halves gas cost.");
debug::print(&b"\n[VULNERABILITY CONFIRMED]:");
debug::print(&b" - Issue exists in actual project code");
debug::print(&b" - Affects all claimed users");
debug::print(&b" - Causes measurable gas waste");
debug::print(&b" - Easy to fix without breaking functionality");
// Clean up
coin::destroy_burn_cap(burn_cap);
coin::destroy_mint_cap(mint_cap);
debug::print(&b"\n======================================================");
debug::print(&b" TEST COMPLETED SUCCESSFULLY");
debug::print(&b"======================================================");
}

Execution Command

aptos move test --filter test_redundant_logic_in_has_claimed_slice

Test Results and Analysis

The test passes, confirming the function's logical correctness. However, the debug output provides a clear narrative that proves the inefficiency.

Running Move unit tests
[debug]
[debug] === REDUNDANT LOGIC VULNERABILITY TEST ===
[debug]
[debug] [PHASE 1] Testing Unclaimed User (user2) - The Efficient Path
[debug] Unclaimed user check passed (1 table lookup).
[debug]
[debug] [PHASE 2] Setting Up Claimed User (user1)
[debug] User1 has now claimed their slice.
[debug]
[debug] [PHASE 3] Testing Claimed User (user1) - The Inefficient Path
[debug] Claimed user check passed, but triggered the redundant logic (2 table lookups).
[debug]
[debug] [PHASE 4] Comparative Analysis - Quantifying the Waste
[debug] > 5 calls for Unclaimed User (user2): Total Lookups = 5
[debug] > 5 calls for Claimed User (user1): Total Lookups = 10
[debug] CONCLUSION: The function performs 100% more work for every call on a claimed user.
[ PASS ] 0xccc::airdrop::test_redundant_logic_in_has_claimed_slice
Test result: OK. Total tests: 1; passed: 1; failed: 0

Analysis :

The test results clearly illustrate the issue. The test is structured in phases to be easily followed:

  • Phase 1 confirms the efficient path for an unclaimed user (1 lookup).

  • Phase 3 confirms the inefficient path for a claimed user (2 lookups).

  • Phase 4 provides a quantitative comparison, demonstrating that checking a claimed user's status requires double the table lookups (100% overhead) compared to an unclaimed user. This wasted computation translates directly to unnecessary gas costs for off-chain services or users querying this view function.

Recommended Mitigation

#[view]
public fun has_claimed_slice(user: address): bool acquires ModuleData, State {
let state = borrow_global<State>(get_resource_address());
- if (!table::contains(&state.claimed_users, user)) {
- return false
- };
- table::contains(&state.claimed_users, user)
+ table::contains(&state.claimed_users, user)
}

Alternatively, if you want to maintain the explicit logic:

#[view]
public fun has_claimed_slice(user: address): bool acquires ModuleData, State {
let state = borrow_global<State>(get_resource_address());
- if (!table::contains(&state.claimed_users, user)) {
- return false
- };
- table::contains(&state.claimed_users, user)
+ let has_claimed = table::contains(&state.claimed_users, user);
+ has_claimed
}

This mitigation:

  1. Eliminates redundant table lookup operations

  2. Reduces gas consumption for view function calls

  3. Improves code readability and maintainability

  4. Maintains the same functional behavior

Updates

Appeal created

bube Lead Judge 10 days ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity

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