# Phase 3, Milestone 2: Network Hardening

> Security hardening for P2P network

**Status**: ✅ Complete
**Priority**: High
**Crate**: `synor-network`

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## Overview

Implement security measures to protect the network from attacks including peer banning, rate limiting, eclipse attack mitigation, and partition detection.

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## Tasks

### Task 2.1: Peer Reputation System
- [x] Track peer behavior scores
- [x] Increment score for good behavior
- [x] Decrement score for bad behavior
- [x] Automatic banning at threshold
- [x] Ban persistence across restarts

**Files:**
- `crates/synor-network/src/reputation.rs`

**Reputation Events:**
| Event | Score Change |
|-------|--------------|
| Valid block | +10 |
| Invalid block | -100 |
| Valid transaction | +1 |
| Invalid transaction | -50 |
| Timeout | -5 |
| Protocol violation | -200 |

### Task 2.2: Rate Limiting
- [x] Per-peer message rate limiting
- [x] Global rate limiting
- [x] Adaptive limits based on load
- [x] Separate limits by message type

**Files:**
- `crates/synor-network/src/rate_limit.rs`

**Rate Limits:**
| Message Type | Limit | Window |
|--------------|-------|--------|
| Transactions | 100/s | 1s |
| Blocks | 10/s | 1s |
| Headers | 1000/s | 1s |
| GetData | 50/s | 1s |

### Task 2.3: Eclipse Attack Mitigation
- [x] Subnet diversity enforcement
- [x] Anchor connections (persistent)
- [x] Peer rotation with minimum tenure
- [x] Outbound connection limits per subnet
- [x] Feeler connections for discovery

**Files:**
- `crates/synor-network/src/eclipse.rs`

**Mitigation Parameters:**
- Max 2 peers per /16 subnet
- 8 anchor connections (persistent)
- Minimum peer tenure: 30 minutes
- Feeler connection interval: 2 minutes

### Task 2.4: Network Partition Detection
- [x] Monitor connectivity metrics
- [x] Detect isolation from network
- [x] Alert on partition symptoms
- [x] Automatic recovery attempts
- [x] Partition event logging

**Files:**
- `crates/synor-network/src/partition.rs` (65 tests)

**Detection Heuristics:**
- No new blocks for >10 minutes
- Peer count drops below threshold
- Tip divergence from known good tips
- Clock skew detection

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## Validation

### Validation Commands

```bash
# Run network tests
cargo test -p synor-network

# Run security-specific tests
cargo test -p synor-network reputation
cargo test -p synor-network rate_limit
cargo test -p synor-network eclipse
cargo test -p synor-network partition
```

### Validation Agents

| Agent | Purpose |
|-------|---------|
| `code-reviewer` | Review security implementations |
| `silent-failure-hunter` | Check edge cases |

### Security Test Cases

```rust
// Test peer banning
#[test]
fn test_peer_banned_after_violations() {
    let mut rep = Reputation::new();
    for _ in 0..3 {
        rep.record_event(peer_id, Event::InvalidBlock);
    }
    assert!(rep.is_banned(peer_id));
}

// Test rate limiting
#[test]
fn test_rate_limit_enforced() {
    let mut limiter = RateLimiter::new(100, Duration::from_secs(1));
    for _ in 0..100 {
        assert!(limiter.check());
    }
    assert!(!limiter.check()); // 101st should fail
}

// Test eclipse mitigation
#[test]
fn test_subnet_diversity() {
    let mut conns = ConnectionManager::new();
    // Add 2 peers from same /16
    conns.add("1.2.3.4:16111");
    conns.add("1.2.5.6:16111");
    // Third from same /16 should be rejected
    assert!(!conns.can_add("1.2.7.8:16111"));
}
```

### Attack Simulations

| Attack | Mitigation | Test |
|--------|------------|------|
| Sybil | Reputation + subnet limits | `test_sybil_resistance` |
| Eclipse | Anchor connections | `test_eclipse_resistance` |
| DoS | Rate limiting | `test_dos_resistance` |
| Partition | Detection + recovery | `test_partition_recovery` |

### Security Checks

- [ ] Banned peers cannot reconnect
- [ ] Rate limits apply to all message types
- [ ] Subnet diversity enforced
- [ ] Partition detection triggers alerts
- [ ] No amplification attacks possible

---

## Compliance

- [ ] CWE-400: Resource Exhaustion (rate limiting)
- [ ] CWE-693: Protection Mechanism Failure (multi-layer defense)

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## Acceptance Criteria

1. Peer reputation system functioning
2. Rate limiting enforced at all levels
3. Eclipse attack mitigations active
4. Partition detection alerts working
5. All 65 network security tests pass

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*Completed: January 2025*