Developer Security Checklist

Use this checklist when writing new code or modifying existing code to ensure security best practices.

Before Writing Code

Understand the security implications of your changes
Identify affected security controls (check governance/config/security-control-mapping.yml)
Review relevant security documentation
Consider threat model for your changes

Input Validation

Validate all user inputs at boundaries
Sanitize inputs before processing
Use type-safe APIs (Rust's type system)
Reject invalid inputs early
Validate data from external sources (network, files, databases)

Examples:

#![allow(unused)]
fn main() {
// ✅ Good: Validate input
fn process_amount(amount: u64) -> Result<u64, Error> {
    if amount > MAX_AMOUNT {
        return Err(Error::AmountTooLarge);
    }
    Ok(amount)
}

// ❌ Bad: No validation
fn process_amount(amount: u64) -> u64 {
    amount // Could overflow
}
}

Authentication & Authorization

Implement proper authentication (if applicable)
Check authorization before sensitive operations
Use principle of least privilege
Verify permissions at every boundary
Don't trust client-side authorization checks

Examples:

#![allow(unused)]
fn main() {
// ✅ Good: Check authorization
fn transfer_funds(from: Account, to: Account, amount: u64) -> Result<(), Error> {
    if !from.has_permission(Permission::Transfer) {
        return Err(Error::Unauthorized);
    }
    // ... transfer logic
}

// ❌ Bad: No authorization check
fn transfer_funds(from: Account, to: Account, amount: u64) {
    // ... transfer logic without checking permissions
}
}

Cryptographic Operations

Use well-tested cryptographic libraries (secp256k1, bitcoin_hashes)
Never hardcode keys or secrets
Use cryptographically secure random number generation
Follow Bitcoin standards (BIP32, BIP39, BIP44)
Verify signatures completely
Use constant-time operations where needed (avoid timing attacks)

Examples:

#![allow(unused)]
fn main() {
// ✅ Good: Use secure random
use rand::rngs::OsRng;
let mut rng = OsRng;
let key = secp256k1::SecretKey::new(&mut rng);

// ❌ Bad: Insecure random
let key = secp256k1::SecretKey::from_slice(&[1, 2, 3, ...])?;
}

Consensus & Protocol

Implement consensus rules exactly as specified
Validate all protocol messages
Handle network errors gracefully
Prevent DoS attacks (rate limiting, resource limits)
Don't bypass consensus validation

Examples:

#![allow(unused)]
fn main() {
// ✅ Good: Validate consensus rules
fn validate_block(block: &Block) -> Result<(), ConsensusError> {
    if !block.verify_merkle_root() {
        return Err(ConsensusError::InvalidMerkleRoot);
    }
    // ... more validation
}

// ❌ Bad: Skip validation
fn validate_block(block: &Block) -> Result<(), ConsensusError> {
    Ok(()) // No validation!
}
}

Memory Safety

Prefer safe Rust code
Document and justify any unsafe code
Ensure proper resource cleanup (Drop trait)
Avoid memory leaks (use RAII patterns)
Check bounds before array/vector access

Examples:

#![allow(unused)]
fn main() {
// ✅ Good: Safe Rust
let value = vec.get(index).ok_or(Error::OutOfBounds)?;

// ❌ Bad: Unsafe indexing
let value = vec[index]; // Could panic
}

Error Handling

Don't leak sensitive information in errors
Use specific error types
Handle all error cases
Fail securely (default deny)
Log errors appropriately (no sensitive data)

Examples:

#![allow(unused)]
fn main() {
// ✅ Good: Generic error message
return Err(Error::AuthenticationFailed); // Doesn't reveal why

// ❌ Bad: Leaks information
return Err(Error::InvalidPassword("user123")); // Reveals username
}

Dependencies

Use minimal dependencies
Keep dependencies up-to-date
Pin consensus-critical dependencies to exact versions
Check for known vulnerabilities (cargo audit)
Review dependency licenses

Examples:

# ✅ Good: Pin critical dependencies
[dependencies]
secp256k1 = "=0.28.0"  # Exact version for consensus-critical

# ❌ Bad: Allow version ranges for critical code
[dependencies]
secp256k1 = "^0.28"  # Could break consensus

Testing

Write security-focused tests
Test edge cases and boundary conditions
Test error handling paths
Include fuzzing for consensus/protocol code
Test with malicious inputs
Achieve adequate test coverage

Examples:

#![allow(unused)]
fn main() {
#[test]
fn test_amount_overflow() {
    assert!(process_amount(u64::MAX).is_err());
}

#[test]
fn test_invalid_signature() {
    let invalid_sig = vec![0u8; 64];
    assert!(verify_signature(&invalid_sig).is_err());
}
}