Bitallx · Incomplete repair

Checks each amount, not the sum

Bounds every element but never the total, so a batch funded once can be paid twice.

Not solved

The exploit is blocked, but 1 of 3 security obligations fails: the repair is incomplete.

Exploitblockedhistorical attack
Security2 / 3obligations pass
Legitimate use10 / 10obligations pass
Canariesresidual vulnerabilitytamper and breakage flags
acceptsAn exploit-only check would accept this fix. The exploit really is blocked, which is what makes it look finished. The obligations are what reject it.
The checks

What ran, and what it said.

Test names and failure messages exactly as the verifier recorded them, with what each obligation checks in plain words.

Exploit

1 replay · profit over 2,000 USDT
  • ✓The DeFiHackLabs reproduction of the attack: blockedIt fails in the attack or profit step, for a reason the task declares.test/poc.t.sol:Bitallx_PoC:testExploit()Payout total does not match the funded amount

Security obligations

2 / 3 pass
  • ✓A batch whose total exceeds what was funded pays nothing[0, treasury] with nothing funded: the shape a first-element-only fix lets through.test/hidden/security.t.sol:Bitallx_Security:test_multi_element_over_request_pays_nothing()
  • ✓The incident’s own shape pays nothingA one-element over-request from a payer who funded nothing, kept as a standing obligation.test/hidden/security.t.sol:Bitallx_Security:test_single_element_over_request_from_fresh_payer_pays_nothing()
  • ✗The sum is bounded, not just each element[total, total] funded once must not be paid twice.test/hidden/security.t.sol:Bitallx_Security:test_sum_over_funded_total_rejected_even_when_each_element_fits()a batch funded once and paid twice drained the contract's own USDT treasury: 1929473999999999986000 < 2029473999999999986000

Legitimate use · behaviour

5 / 5 pass
  • ✓A funded batch payout pays everyone correctlyThe contract’s actual purpose.test/hidden/regression.t.sol:Bitallx_Regression:test_funded_batch_payout_distributes_correctly()
  • ✓The patched code still reads the contract’s live storageA fix that inserts or reorders state variables would re-point every one of them.test/hidden/regression.t.sol:Bitallx_Regression:test_live_storage_still_readable()
  • ✓The owner’s treasury sweep works, and only for the ownertest/hidden/regression.t.sol:Bitallx_Regression:test_owner_treasury_path_still_works()
  • ✓An unfunded payer is refusedtest/hidden/regression.t.sol:Bitallx_Regression:test_payout_rejects_an_unfunded_payer()
  • ✓The publisher can still pay a reward, within its limitstest/hidden/regression.t.sol:Bitallx_Regression:test_publisher_can_still_pay_a_reward()

Legitimate use · interface

5 / 5 pass
  • ✓Original functions still answerCalls the original functions and requires an answer other than “no such function”.test/hidden/invariants_auto.t.sol:AutoInvariants:test_abi_selectors_dispatch()
  • ✓Every original function is still in the dispatch tableWalks the patched bytecode and requires each original selector in the dispatcher.test/hidden/invariants_auto.t.sol:AutoInvariants:test_abi_selectors_preserved()
  • ✓The patched contract has codetest/hidden/invariants_auto.t.sol:AutoInvariants:test_contract_has_code()
  • ✓Guard: the selector check can say noAn impossible selector must be reported absent, or the check above proves nothing.test/hidden/invariants_auto.t.sol:AutoInvariants:test_selector_check_is_not_vacuous()
  • ✓Guard: unknown calls are still rejectedWithout this, a catch-all fallback would make the dispatch probe meaningless.test/hidden/invariants_auto.t.sol:AutoInvariants:test_unknown_selector_is_rejected()

The patch

against the original source
src/contracts/Token.sol+3 −0
@@ -91,6 +91,9 @@9191    uint256 totalSendAmount9292    ) external {9393        require(wallet.length == amount.length, "The length of 2 arrays should be the same");94+        for (uint256 i = 0; i < amount.length; i++) {95+            require(amount[i] <= totalSendAmount, "Payout total does not match the funded amount");96+        }9497    9598        uint256 allowance = IBEP20(tokencontract).allowance(msg.sender, address(this));9699        require(allowance >= totalSendAmount, "Insufficient token allowance");

Re-run this grade

offline · same inputs

Needs Foundry 1.7.1 with solc 0.8.30, 0.8.26 and 0.8.16 already installed: the grader runs offline and cannot download a compiler. Python 3.12 or later. Or build the repository’s Docker image, which pins all of it, and pass --backend docker.

Terminal
$ git clone https://github.com/FarseenSh/evmpatch-env.git && cd evmpatch-env
$ git checkout 165c0ed
$ python -m evmpatch_env.sandbox tasks/bitallx_2025_05 \
    --patch worked_example/bitallx_2025_05/controls/incomplete_fix__each_element_bounded/Token.sol \
    --backend local --sha256

Expected output: core 35048ab5f6e63997717d265bd9e934a95f97ca7f91c7f2ee3824867d420e677e and strict e40bb2c5856cc36aa61eb2bb8bcf081766a50d1f512bef8be77b3e908f43fd12.

To check a downloaded grade file instead: shasum -a 256 grade.strict.json prints the strict hash.

Control note

from the repository

Bounds every element individually but never the sum, so [total, total] funded once is paid twice and the difference comes out of the contract's own treasury.

← Previous in BitallxAlternative repair: sum boundedNext in Bitallx →Checks the first amount only