

| Priority      | Rule Name                         | Description                                   | Action       |
|---------------|-----------------------------------|-----------------------------------------------|--------------|
| 1000          | allow-api-location-whitelist      | 明确允许的 API 路径白名单                    | allow        |
| 1100          | allow-vpn-trusted-ip-ranges       | 特殊 VPN 网络段（信任 IP 段）允许访问        | allow        |
| 2000          | country-deny-ru                   | 地区封锁，如拒绝 RU 流量                    | deny(403)    |
| 3000          | waf-preconfigured-rules           | Cloud Armor WAF 检测（SQLi/XSS 等）          | deny(403)    |
| 4000          | rate-limit-ip                     | 基于来源 IP 的速率限制与封禁                | deny(429) or throttle |
| 2147483647    | default-deny-all                  | 默认拒绝所有未命中规则的流量                | deny(403)    |


Google Cloud Platform (GCP) Cloud Armor is a powerful tool for securing applications by providing Web Application Firewall (WAF) capabilities, DDoS protection, and access control. Below, I will outline best practices for the points you've mentioned, including examples and considerations for dynamic API environments as mentioned in your first point.

---

### 1. Create Whitelist Access Based on API Location Path
**Objective:** Allow access only to specific API paths while denying others by default. Since your APIs are dynamically added, a flexible and prioritized rule design is necessary.

#### Best Practices:
- **Use Path-Based Matching:** Define rules to allow access to specific API paths using `request.path` in Cloud Armor policies.
- **Dynamic API Path Handling:** Since APIs are dynamically added, group APIs with similar paths under a broader pattern (e.g., `/api/v1/*`) and create rules to whitelist these patterns.
- **Rule Priority Design:** Assign a lower priority number (e.g., `1000`) to whitelist rules so they are evaluated before more restrictive rules (like Deny All).
- **Regular Updates:** Automate updates to Cloud Armor policies using scripts (e.g., via `gcloud` commands) to add new API paths as they are created.

#### Example Rule:
- **Target:** Whitelist access to `/api/v1/users/*`
- **Expression:** `request.path.matches('/api/v1/users/*')`
- **Action:** Allow
- **Priority:** `1000`

#### Implementation via `gcloud`:
```bash
gcloud compute security-policies rules create 1000 \
    --security-policy=my-policy \
    --expression="request.path.matches('/api/v1/users/*')" \
    --action=allow \
    --description="Allow access to /api/v1/users/*"
```

#### Considerations for Dynamic APIs:
- Use a CI/CD pipeline or infrastructure-as-code (IaC) tools like Terraform to update Cloud Armor policies when new APIs are deployed.
- Monitor logs in Cloud Logging to identify unlisted API paths that are being blocked and adjust rules accordingly.

---

### 2. Default Deny All Access with Rule Priority (e.g., 2147483647)
**Objective:** Deny all traffic by default unless explicitly allowed by higher-priority rules.

#### Best Practices:
- **Set Deny Rule at Lowest Priority:** Use the highest possible priority value (`2147483647`) for the default Deny rule to ensure it is evaluated last.
- **Explicit Allow Rules:** Ensure all whitelist rules (like the one for API paths) have lower priority numbers (e.g., `1000`, `2000`) so they override the default Deny rule.

#### Example Rule:
- **Target:** Deny all traffic
- **Expression:** `true` (matches all requests)
- **Action:** Deny
- **Priority:** `2147483647`

#### Implementation via `gcloud`:
```bash
gcloud compute security-policies rules create 2147483647 \
    --security-policy=my-policy \
    --expression="true" \
    --action=deny-403 \
    --description="Default Deny All"
```

#### Considerations:
- Ensure no rule conflicts by testing higher-priority rules (Allow) against this default Deny rule.

---

### 3. Block Specific Countries Using `region_code` Configuration
**Objective:** Restrict access from specific countries to prevent unwanted traffic.

#### Best Practices:
- **Use Geo-Based Restrictions:** Leverage Cloud Armor’s `origin.region_code` to block or allow traffic based on the source country.
- **Priority:** Place geo-restriction rules at a medium priority (e.g., `5000`), after specific whitelist rules but before the default Deny rule.
- **Monitor and Update:** Regularly review traffic logs to ensure legitimate users from blocked countries are not affected (e.g., use VPN exceptions if needed).

#### Example Rule:
- **Target:** Block traffic from specific countries (e.g., `CN` for China, `RU` for Russia)
- **Expression:** `origin.region_code in ['CN', 'RU']`
- **Action:** Deny
- **Priority:** `5000`

#### Implementation via `gcloud`:
```bash
gcloud compute security-policies rules create 5000 \
    --security-policy=my-policy \
    --expression="origin.region_code in ['CN', 'RU']" \
    --action=deny-403 \
    --description="Block specific countries"
```

#### Considerations:
- Geo-restrictions may not be 100% accurate due to VPNs or proxy servers. Combine with other security measures (e.g., WAF rules).
- Whitelist specific IPs or ranges for trusted users in blocked regions with higher-priority Allow rules.

---

### 4. Configure WAF Rules
**Objective:** Protect applications from common vulnerabilities using predefined or custom WAF rules.

#### Best Practices:
- **Use Preconfigured Rulesets:** Enable OWASP Core Rule Set (CRS) or other predefined rulesets in Cloud Armor to protect against SQL injection, XSS, and other attacks.
- **Custom Rules:** Write custom expressions for application-specific vulnerabilities or to address false positives from predefined rules.
- **Priority:** Place WAF rules at a medium-high priority (e.g., `2000`–`4000`) to ensure they are evaluated after specific whitelists but before geo-restrictions.
- **Logging and Tuning:** Enable logging for WAF rules to identify false positives and fine-tune rules over time.

#### Example Rule (Custom WAF Rule):
- **Target:** Block SQL injection attempts in query parameters
- **Expression:** `request.query.contains("union+select")`
- **Action:** Deny
- **Priority:** `3000`

#### Implementation via `gcloud`:
```bash
gcloud compute security-policies rules create 3000 \
    --security-policy=my-policy \
    --expression="request.query.contains('union+select')" \
    --action=deny-403 \
    --description="Block SQL injection attempts"
```

#### Considerations:
- Regularly update WAF rules to address new attack patterns.
- Use `preview` mode for new rules to test their impact before enforcing them.

---

### 5. DDoS Attack Protection Rules
**Objective:** Mitigate Distributed Denial of Service (DDoS) attacks using Cloud Armor’s built-in protection.

#### Best Practices:
- **Enable DDoS Protection:** Cloud Armor automatically mitigates Layer 7 DDoS attacks (e.g., HTTP floods) when attached to a backend service.
- **Use Rate-Based Rules:** Combine with rate-limiting rules (next point) to block IPs sending excessive requests.
- **Priority:** DDoS rules are generally enforced at the infrastructure level by Cloud Armor, but custom rate-based or behavioral rules can have a priority like `2000`.
- **Adaptive Protection:** Enable Adaptive Protection (available in Cloud Armor Security Plus tier) to detect and mitigate sophisticated attacks using machine learning.

#### Considerations:
- Monitor traffic in real-time using Cloud Monitoring and Cloud Logging to identify DDoS attack patterns.
- Ensure sufficient capacity in backend services to handle legitimate traffic spikes.

---

### 6. Rate-Based Ban Configuration (Source IP Throttling)
**Objective:** Limit the number of requests per IP to prevent abuse or DDoS attacks.

#### Best Practices:
- **Set Rate Limits:** Use Cloud Armor’s rate-based ban to throttle IPs exceeding a specified request rate (e.g., 100 requests per minute).
- **Ban Duration:** Configure a ban duration (e.g., 10 minutes) to temporarily block offending IPs.
- **Priority:** Place rate-based rules at a medium priority (e.g., `4000`), after specific whitelists and WAF rules.
- **Exceptions:** Whitelist trusted IPs (e.g., internal monitoring tools) to avoid throttling legitimate traffic.

#### Example Rule:
- **Target:** Throttle IPs exceeding 100 requests per minute
- **Expression:** Rate-based rule with a threshold of 100 requests per minute
- **Action:** Throttle and ban for 10 minutes
- **Priority:** `4000`

#### Implementation via `gcloud`:
```bash
gcloud compute security-policies rules create 4000 \
    --security-policy=my-policy \
    --expression="true" \
    --action=throttle \
    --rate-limit-options-config='{"rateLimitThreshold": {"count": 100, "intervalSec": 60}, "banDurationSec": 600}' \
    --description="Rate limit per IP"
```

#### Considerations:
- Fine-tune rate limits based on application usage patterns to avoid blocking legitimate users.
- Monitor throttled IPs in Cloud Logging to adjust thresholds if needed.

---

### Summary of Priority Design
Given your dynamic API environment, the rule priorities should generally follow this structure:
1. **Whitelist Rules for API Paths:** Priority `1000`–`2000`
2. **WAF Rules:** Priority `2000`–`3000`
3. **DDoS/Rate-Based Rules:** Priority `3000`–`4000`
4. **Geo-Restriction Rules:** Priority `5000`–`6000`
5. **Default Deny Rule:** Priority `2147483647`

#### Final Notes:
- **Automation:** Use scripts or IaC tools to manage dynamic API path rules and policy updates.
- **Monitoring:** Enable detailed logging for Cloud Armor in Cloud Logging to audit rules and detect issues.
- **Testing:** Use `preview` mode for new rules to evaluate their impact before enforcement.

By following these best practices, you can ensure robust security for your application while accommodating dynamic API additions and protecting against common threats. Let me know if you need help with specific configurations or automation scripts!

Below is a Markdown table summarizing the Cloud Armor rule priorities based on the best practices and structure discussed earlier. This table organizes the rules by their purpose, priority range, and example actions to provide a clear overview of the policy design.

```markdown
| Rule Type                     | Priority Range      | Example Action             | Description                                      |
|-------------------------------|---------------------|----------------------------|--------------------------------------------------|
| Whitelist Rules for API Paths | 1000 - 2000         | Allow                     | Allow access to specific API paths (e.g., `/api/v1/users/*`) |
| WAF Rules                     | 2000 - 3000         | Deny (e.g., SQL Injection)| Protect against common vulnerabilities (e.g., XSS, SQLi) |
| DDoS/Rate-Based Rules         | 3000 - 4000         | Throttle/Ban              | Mitigate DDoS and limit requests per IP          |
| Geo-Restriction Rules         | 5000 - 6000         | Deny                      | Block traffic from specific countries            |
| Default Deny Rule             | 2147483647          | Deny                      | Deny all traffic not matched by higher-priority rules |
```

This table can be used as a reference for designing Cloud Armor policies with a clear hierarchy of priorities, ensuring that rules are evaluated in the correct order. Let me know if you'd like to add more details or adjust the ranges!

