Cairo Vulnerability Scanner

// Cairo contract indicators
#[contract]
mod MyContract {
    use starknet::ContractAddress;

    #[storage]
    struct Storage {
        balance: LegacyMap<ContractAddress, felt252>,
    }

    #[external(v0)]
    fn transfer(ref self: ContractState, to: ContractAddress, amount: felt252) {
        // Contract logic
    }

    #[l1_handler]
    fn handle_deposit(ref self: ContractState, from_address: felt252, amount: u256) {
        // L1 message handler
    }
}

// Common patterns
felt252, u128, u256
ContractAddress, EthAddress
#[external(v0)], #[l1_handler], #[constructor]
get_caller_address(), get_contract_address()
send_message_to_l1_syscall

=== CAIRO/STARKNET VULNERABILITY SCAN RESULTS ===


---

## 5. Vulnerability Patterns (6 Patterns)

I check for 6 critical vulnerability patterns unique to Cairo/Starknet. For detailed detection patterns, code examples, mitigations, and testing strategies, see [VULNERABILITY_PATTERNS.md](resources/VULNERABILITY_PATTERNS.md).

### Pattern Summary:

1. **Unchecked Arithmetic** ⚠️ CRITICAL - Integer overflow/underflow in felt252
2. **Storage Collision** ⚠️ CRITICAL - Conflicting storage variable hashes
3. **Missing Access Control** ⚠️ CRITICAL - No caller validation on sensitive functions
4. **Improper Felt252 Boundaries** ⚠️ HIGH - Not validating felt252 range
5. **Unvalidated Contract Address** ⚠️ HIGH - Using untrusted contract addresses
6. **Missing Caller Validation** ⚠️ CRITICAL - No get_caller_address() checks

For complete vulnerability patterns with code examples, see [VULNERABILITY_PATTERNS.md](resources/VULNERABILITY_PATTERNS.md).
## 5. Scanning Workflow

### Step 1: Platform Identification
1. Verify Cairo language and StarkNet framework
2. Check Cairo version (Cairo 1.0+ vs legacy Cairo 0)
3. Locate contract files (`src/*.cairo`)
4. Identify L1-L2 bridge contracts (if applicable)

### Step 2: Arithmetic Safety Sweep

### Step 3: L1 Handler Analysis
For each `#[l1_handler]` function:
- [ ] Validates `from_address` parameter
- [ ] Checks address != zero
- [ ] Has proper access control
- [ ] Emits events for monitoring

### Step 4: Signature Verification Review
For signature-based functions:
- [ ] Includes nonce tracking
- [ ] Nonce incremented after use
- [ ] Domain separator includes chain ID and contract address
- [ ] Cannot replay signatures

### Step 5: L1-L2 Bridge Audit
If contract includes bridge functionality:
- [ ] L1 validates address < STARKNET_FIELD_PRIME
- [ ] L1 implements message cancellation
- [ ] L2 validates from_address in handlers
- [ ] Symmetric access controls L1 ↔ L2
- [ ] Test full roundtrip flows

### Step 6: Static Analysis with Caracal

---

## 6. Reporting Format

### Finding Template

// bridge.cairo, line 145
#[l1_handler]
fn handle_deposit(
    ref self: ContractState,
    from_address: felt252,  // Not validated!
    user: ContractAddress,
    amount: u256
) {
    let current_balance = self.balances.read(user);
    self.balances.write(user, current_balance + amount);
}

#[l1_handler]
fn handle_deposit(
    ref self: ContractState,
    from_address: felt252,
    user: ContractAddress,
    amount: u256
) {
    // Validate L1 sender
    let authorized_l1_bridge = self.l1_bridge_address.read();
    assert(from_address == authorized_l1_bridge, 'Unauthorized L1 sender');

    let current_balance = self.balances.read(user);
    self.balances.write(user, current_balance + amount);
}

---

## 7. Priority Guidelines

### Critical (Immediate Fix Required)
- Unchecked from_address in L1 handlers (infinite mint)
- L1-L2 address conversion issues (funds to zero address)

### High (Fix Before Deployment)
- Felt252 arithmetic overflow/underflow (balance manipulation)
- Missing signature replay protection (replay attacks)
- L1-L2 message failure without cancellation (locked funds)

### Medium (Address in Audit)
- Overconstrained L1-L2 interactions (trapped funds)

---

## 8. Testing Recommendations

### Unit Tests

### Integration Tests (with L1)

### Caracal CI Integration

---

## 9. Additional Resources

- **Building Secure Contracts**: `building-secure-contracts/not-so-smart-contracts/cairo/`
- **Caracal**: https://github.com/crytic/caracal
- **Cairo Documentation**: https://book.cairo-lang.org/
- **StarkNet Documentation**: https://docs.starknet.io/
- **OpenZeppelin Cairo Contracts**: https://github.com/OpenZeppelin/cairo-contracts

---

## 10. Quick Reference Checklist

Before completing Cairo/StarkNet audit:

**Arithmetic Safety (HIGH)**:
- [ ] No felt252 used for balances/amounts (use u128/u256)
- [ ] OR felt252 arithmetic has explicit bounds checking
- [ ] Overflow/underflow scenarios tested

**L1 Handler Security (CRITICAL)**:
- [ ] ALL `#[l1_handler]` functions validate `from_address`
- [ ] from_address compared against stored L1 contract address
- [ ] Cannot bypass by deploying alternate L1 contract

**L1-L2 Messaging (HIGH)**:
- [ ] L1 bridge validates addresses < STARKNET_FIELD_PRIME
- [ ] L1 bridge implements message cancellation
- [ ] L2 handlers check from_address
- [ ] Symmetric validation rules L1 ↔ L2
- [ ] Full roundtrip flows tested

**Signature Security (HIGH)**:
- [ ] Signatures include nonce tracking
- [ ] Nonce incremented after each use
- [ ] Domain separator includes chain ID and contract address
- [ ] Signature replay tested and prevented
- [ ] Cross-chain replay prevented

**Tool Usage**:
- [ ] Caracal scan completed with no critical findings
- [ ] Unit tests cover all vulnerability scenarios
- [ ] Integration tests verify L1-L2 flows
- [ ] Testnet deployment tested before mainnet