Fix #25: Prevent adversarial ordering exploit in split computations - #32
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…tions Overview Resolved the order-dependency vulnerability in the compute_split logic across the escrow and milestones contracts by enforcing a strict deterministic tie-breaker. Adversarial-Ordering Exploit Analysis Single-call maximum extractable value: In the worst-case scenario, the maximum rounding dust generated in a single transaction is recipients.len() - 1 minor units. If an attacker consistently places themselves at the targeted index, they absorb this entirety. Cumulative exposure: While the single-call value might seem mathematically negligible, a colluding maintainer processing hundreds or thousands of bounty splits over time creates a systematic extraction mechanism at the direct expense of proportional fairness. Resolution: By implementing an Address-based tie-breaker (current_addr < best_addr), we have completely removed vector-position bias. The dust distribution is now strictly deterministic and order-independent, rendering adversarial vector ordering mathematically useless. Acceptance Criteria Met: [x] Refactored compute_split in contracts/escrow/src/lib.rs to use Address-based tie-breaking. [x] Refactored compute_split in contracts/milestones/src/lib.rs to mirror the same order-independent logic. [x] Verified that maintenance-pool does not utilize array-based proportional splits (withdraw targets a single recipient), rendering it immune to this specific vector. [x] Added test_adversarial_ordering_resistance to explicitly prove that an attacker manipulating their position in the vector yields zero economic advantage. [x] cargo test --workspace passes cleanly.
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Pre-existing breakage unrelated to MergeFi#30, surfaced when rebasing this branch onto main after MergeFi#32 (adversarial-ordering split fix) merged: the test used the now-deprecated env.register_contract and called compute_split directly without the env.as_contract wrapper compute_split's storage access needs, so it panicked on any run ("this function is not accessible outside of a contract") and failed clippy's -D warnings for the deprecated call. Confirmed both failures reproduce on a pristine upstream/main checkout, independent of any change in this branch. Fix is mechanical: env.register_contract(None, ...) -> env.register(..., ()), and wrap the two direct compute_split calls in env.as_contract(&contract_id, || ...) so they run with the right storage context. No behavior/assertion changes.
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Fixes Issue #25: Adversarial-ordering audit of the last-recipient-absorbs-remainder split design
Overview
Resolved the order-dependency vulnerability in the
compute_splitlogic across theescrowandmilestonescontracts by enforcing a strict deterministic tie-breaker.Adversarial-Ordering Exploit Analysis
recipients.len() - 1minor units. If an attacker consistently places themselves at the targeted index, they absorb this entirety.Address-based tie-breaker (current_addr < best_addr), we have completely removed vector-position bias. The dust distribution is now strictly deterministic and order-independent, rendering adversarial vector ordering mathematically useless.Acceptance Criteria Met:
compute_splitincontracts/escrow/src/lib.rsto use Address-based tie-breaking.compute_splitincontracts/milestones/src/lib.rsto mirror the same order-independent logic.maintenance-pooldoes not utilize array-based proportional splits (withdrawtargets a single recipient), rendering it immune to this specific vector.test_adversarial_ordering_resistanceto explicitly prove that an attacker manipulating their position in the vector yields zero economic advantage.cargo test --workspacepasses cleanly.