| 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
// ❌ 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);
}
// ❌ 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:
- Identify who should be authorized to call it
- Verify authorization check exists (witness + assertion)
- Check authorization uses proper cryptographic verification
// 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:
- Trace value origin (ledger, witness, computation)
- Verify
disclose() is used for public outputs
- Check for implicit disclosure via ledger writes
// 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:
- Check type bounds (Uint has 2^N values)
- Verify assertions bound the valid range
- Look for missing null/empty checks
// ❌ 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
Related Skills
