--- name: compact-reviewer:security-review description: Use when reviewing Compact contracts for security vulnerabilities, privacy leaks, disclosure violations, access control issues, or ZK-specific attack vectors. --- # Security Review Skill Comprehensive security analysis for Compact smart contracts on the Midnight Network. ## When to Use This skill activates for queries about: - Security vulnerabilities in Compact contracts - Privacy and disclosure issues - Access control verification - ZK-specific attack patterns - Audit and security review **Trigger words**: security, vulnerability, audit, disclosure, access control, privacy leak, attack vector ## Quick Reference ### Security Checklist | Category | Check | Severity if Failed | |----------|-------|-------------------| | **Access Control** | Exported circuits verify caller authorization | 🔴 Critical | | **Disclosure** | All public outputs use `disclose()` | 🔴 Critical | | **Input Validation** | All witness inputs validated/bounded | 🔴 Critical | | **State Protection** | Ledger writes have authorization checks | 🟠 High | | **ZK Attacks** | Low-entropy witnesses not used in hashes | 🔴 Critical | | **Timing** | No witness-dependent control flow | 🟠 High | ### Common Vulnerabilities ```compact // ❌ Missing access control export circuit withdraw(amount: Uint<64>): [] { balance.decrement(amount); // Anyone can call! } // ✅ With access control export circuit withdraw(amount: Uint<64>): [] { const caller = get_caller_secret(); assert hash(caller) == owner_hash.read(); balance.decrement(amount); } ``` ```compact // ❌ Disclosure violation export circuit get_balance(): Uint<64> { return balance.read(); // Missing disclose! } // ✅ Explicit disclosure export circuit get_balance(): Uint<64> { return disclose(balance.read()); } ``` ### ZK Attack Vectors | ID | Attack | Risk | Detection | |----|--------|------|-----------| | AV-03 | Nullifier Linkability | 🔴 Critical | Low-entropy input to `persistentHash()` | | AV-06 | Witness Entropy Exhaustion | 🔴 Critical | Bounded witness types (Uint<8>, enums) | | AV-01 | Implicit Taint Leakage | 🟠 High | Witness-dependent control flow | | AV-08 | Circuit Under-Constraint | 🔴 Critical | Missing assertions on witness ranges | ## Review Process ### 1. Access Control Verification For each `export circuit`: 1. Identify who should be authorized to call it 2. Verify authorization check exists (witness + assertion) 3. Check authorization uses proper cryptographic verification ```compact // Pattern: Authorization check witness get_admin_key(): Bytes<32>; export circuit admin_action(): [] { const admin = get_admin_key(); assert hash(admin) == admin_hash.read(); // ✓ Crypto verification // ... perform action } ``` ### 2. Disclosure Analysis For each value returned from a circuit: 1. Trace value origin (ledger, witness, computation) 2. Verify `disclose()` is used for public outputs 3. Check for implicit disclosure via ledger writes ```compact // Must use disclose() for: // - Return values from export circuits // - Values derived from witnesses that become public // - Ledger state that should be visible ``` ### 3. Input Validation For each witness function: 1. Check type bounds (Uint has 2^N values) 2. Verify assertions bound the valid range 3. Look for missing null/empty checks ```compact // ❌ Unbounded witness witness get_choice(): Uint<8>; // 256 possibilities export circuit vote(): [] { const choice = get_choice(); voteTally[choice].increment(1); // No bounds check! } // ✅ Bounded witness export circuit vote(): [] { const choice = get_choice(); assert choice < 5; // Only 5 valid choices voteTally[choice].increment(1); } ``` ### 4. ZK-Specific Checks Run through attack vector checklist: | Check | Look For | If Found | |-------|----------|----------| | AV-01 | `if disclose(witness)` or witness in loop count | Flag timing leak | | AV-03 | `persistentHash(low_entropy)` | Flag nullifier linkability | | AV-06 | Uint<1-16> in security-critical paths | Flag brute-force risk | | AV-08 | Witness used without range assertion | Flag under-constraint | ## References - [Vulnerability Checklist](./references/vulnerability-checklist.md) - Complete vulnerability catalog - [Disclosure Rules](./references/disclosure-rules.md) - Privacy leak detection patterns - [ZK Attack Vectors](./references/zk-attack-vectors.md) - AV-01 through AV-12 documentation ## Related Skills - [critical-issues](../critical-issues/SKILL.md) - Bug and logic error detection - [compact-core/privacy-disclosure](../../../compact-core/skills/privacy-disclosure/SKILL.md) - Compact privacy model - [compact-core/standard-library](../../../compact-core/skills/standard-library/SKILL.md) - Crypto function safety

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