implementing-ddos-mitigation-with-cloudflare

name	implementing-ddos-mitigation-with-cloudflare
description	配置 Cloudflare DDoS 防护，包括托管规则集、速率限制、WAF 规则、Bot 管理和源站保护，以缓解容量型、协议型和应用层攻击。
domain	cybersecurity
subdomain	network-security
tags	["ddos","cloudflare","ddos-mitigation","rate-limiting","waf","bot-management","layer-7","volumetric-attack","network-security"]
version	1.0
author	mahipal
license	Apache-2.0

使用 Cloudflare 实施 DDoS 缓解

概述

Cloudflare 通过其遍布全球 300 多个数据中心、477+ Tbps 容量的网络提供多层 DDoS（分布式拒绝服务）防护。该平台防护 L3/4 容量型攻击（SYN 洪水、UDP 放大、DNS 反射）、协议攻击（Ping of Death、Smurf）和 L7 应用层攻击（HTTP 洪水、Slowloris、缓存破坏）。Cloudflare 的自主检测系统使用流量分析、机器学习和自适应规则集，在约 3 秒内识别并缓解攻击。本技能涵盖配置 Cloudflare DDoS 防护栈，包括托管规则集、WAF 规则、速率限制、Bot 管理和源站服务器加固。

前置条件

• Cloudflare 账户（WAF 最低需要 Pro 计划，高级 DDoS 需要 Enterprise 计划）
• 已将 DNS 委托给 Cloudflare 名称服务器的域名
• 源站服务器 IP 地址
• 了解正常流量模式和峰值
• 用于自动化的 Cloudflare API 令牌

核心概念

DDoS 攻击类别

层	攻击类型	示例	Cloudflare 防护
L3/4	容量型	SYN 洪水、UDP 洪水、DNS 放大	网络层 DDoS 托管规则
L3/4	协议型	Ping of Death、Smurf、IP 分片	高级 TCP 防护
L7	应用层	HTTP 洪水、Slowloris、缓存破坏	HTTP DDoS 托管规则、WAF、速率限制
DNS	DNS 专项	DNS 查询洪水、NXDOMAIN 攻击	高级 DNS 防护

Cloudflare 防护栈

互联网流量
     │
     ▼
┌─────────────────────────┐
│  Cloudflare 边缘节点（PoP）│
│  ┌───────────────────┐  │
│  │ L3/4 DDoS 托管规则 │  │  ← 容量型/协议型缓解
│  └───────────────────┘  │
│  ┌───────────────────┐  │
│  │ IP 访问规则        │  │  ← 国家/ASN/IP 封锁
│  └───────────────────┘  │
│  ┌───────────────────┐  │
│  │ Bot 管理           │  │  ← Bot 评分、JS 验证
│  └───────────────────┘  │
│  ┌───────────────────┐  │
│  │ WAF 托管规则       │  │  ← OWASP、Cloudflare、自定义
│  └───────────────────┘  │
│  ┌───────────────────┐  │
│  │ 速率限制           │  │  ← 请求速率执行
│  └───────────────────┘  │
│  ┌───────────────────┐  │
│  │ HTTP DDoS 托管规则 │  │  ← L7 洪水检测
│  └───────────────────┘  │
└─────────────────────────┘
     │
     ▼
  源站服务器

步骤

步骤 1：将域名接入 Cloudflare

# 通过 API 添加域名
curl -X POST "https://api.cloudflare.com/client/v4/zones" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "name": "example.com",
    "type": "full",
    "plan": {"id": "enterprise"}
  }'

# 更新 DNS 记录（启用代理以获得 DDoS 防护）
curl -X POST "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/dns_records" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "type": "A",
    "name": "example.com",
    "content": "203.0.113.50",
    "proxied": true,
    "ttl": 1
  }'

步骤 2：配置 DDoS 托管规则集

HTTP DDoS 攻击防护覆盖：

# 列出 HTTP DDoS 托管规则集
curl -X GET "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/phases/ddos_l7/entrypoint" \
  -H "Authorization: Bearer $CF_API_TOKEN"

# 覆盖 HTTP DDoS 灵敏度和动作
curl -X PUT "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/phases/ddos_l7/entrypoint" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "rules": [{
      "action": "execute",
      "action_parameters": {
        "id": "4d21379b4f9f4bb088e0729962c8b3cf",
        "overrides": {
          "rules": [{
            "id": "fdfdac75430c4c47a422bdc024aab531",
            "sensitivity_level": "medium",
            "action": "block"
          }],
          "sensitivity_level": "high"
        }
      },
      "expression": "true"
    }]
  }'

网络层 DDoS 防护覆盖：

curl -X PUT "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/rulesets/phases/ddos_l4/entrypoint" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "rules": [{
      "action": "execute",
      "action_parameters": {
        "id": "3b64149bfa6e4220bbbc2bd6db7c867e",
        "overrides": {
          "sensitivity_level": "high"
        }
      },
      "expression": "true"
    }]
  }'

步骤 3：配置速率限制规则

# 为登录端点创建速率限制规则
curl -X POST "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/phases/http_ratelimit/entrypoint" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "rules": [
      {
        "description": "Rate limit login attempts",
        "expression": "(http.request.uri.path eq \"/api/login\")",
        "action": "block",
        "ratelimit": {
          "characteristics": ["cf.colo.id", "ip.src"],
          "period": 60,
          "requests_per_period": 10,
          "mitigation_timeout": 600
        }
      },
      {
        "description": "Rate limit API endpoints",
        "expression": "(http.request.uri.path matches \"^/api/\")",
        "action": "managed_challenge",
        "ratelimit": {
          "characteristics": ["cf.colo.id", "ip.src"],
          "period": 60,
          "requests_per_period": 100,
          "mitigation_timeout": 300
        }
      },
      {
        "description": "Global rate limit per IP",
        "expression": "true",
        "action": "managed_challenge",
        "ratelimit": {
          "characteristics": ["ip.src"],
          "period": 10,
          "requests_per_period": 50,
          "mitigation_timeout": 60
        }
      }
    ]
  }'

步骤 4：配置 WAF 自定义规则

# 阻止已知攻击模式
curl -X POST "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/phases/http_request_firewall_custom/entrypoint" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "rules": [
      {
        "description": "Block requests from known bad ASNs",
        "expression": "(ip.geoip.asnum in {12345 67890})",
        "action": "block"
      },
      {
        "description": "Challenge requests without User-Agent",
        "expression": "(not http.user_agent ne \"\")",
        "action": "managed_challenge"
      },
      {
        "description": "Block high-risk countries for admin paths",
        "expression": "(http.request.uri.path contains \"/admin\" and not ip.geoip.country in {\"US\" \"CA\" \"GB\"})",
        "action": "block"
      },
      {
        "description": "Block oversized request bodies",
        "expression": "(http.request.body.size gt 10000000)",
        "action": "block"
      }
    ]
  }'

步骤 5：配置源站保护

确保源站服务器只接受来自 Cloudflare 的流量：

# 获取 Cloudflare IP 范围
curl https://api.cloudflare.com/client/v4/ips

# 配置源站服务器防火墙（iptables）
# 只允许 Cloudflare IP
for ip in $(curl -s https://www.cloudflare.com/ips-v4); do
    iptables -A INPUT -p tcp --dport 443 -s $ip -j ACCEPT
    iptables -A INPUT -p tcp --dport 80 -s $ip -j ACCEPT
done

# 丢弃所有其他 HTTP/HTTPS 流量
iptables -A INPUT -p tcp --dport 443 -j DROP
iptables -A INPUT -p tcp --dport 80 -j DROP

# 启用认证源站拉取（双向 TLS）
# 下载 Cloudflare 源站 CA 证书
curl -o /etc/ssl/cloudflare-origin-pull.pem \
  https://developers.cloudflare.com/ssl/static/authenticated_origin_pull_ca.pem

# Nginx 认证源站拉取配置
# ssl_client_certificate /etc/ssl/cloudflare-origin-pull.pem;
# ssl_verify_client on;

步骤 6：启用攻击模式自动化

#!/usr/bin/env python3
"""根据流量异常自动启用 Cloudflare 攻击模式。"""

import requests
import time
import sys

CF_API_TOKEN = "your-api-token"
ZONE_ID = "your-zone-id"
HEADERS = {
    "Authorization": f"Bearer {CF_API_TOKEN}",
    "Content-Type": "application/json",
}
BASE_URL = f"https://api.cloudflare.com/client/v4/zones/{ZONE_ID}"

NORMAL_RPS_THRESHOLD = 5000  # 每秒请求数阈值
CHECK_INTERVAL = 30  # 检查间隔秒数


def get_current_security_level():
    """获取当前安全级别设置。"""
    resp = requests.get(
        f"{BASE_URL}/settings/security_level",
        headers=HEADERS
    )
    return resp.json()["result"]["value"]


def set_security_level(level: str):
    """设置安全级别（off/essentially_off/low/medium/high/under_attack）。"""
    resp = requests.patch(
        f"{BASE_URL}/settings/security_level",
        headers=HEADERS,
        json={"value": level}
    )
    result = resp.json()
    if result["success"]:
        print(f"[+] 安全级别已设置为：{level}")
    else:
        print(f"[-] 设置安全级别失败：{result['errors']}")
    return result["success"]


 ():
    
    query =  % ZONE_ID

    resp = requests.post(
        ,
        headers=HEADERS,
        json={: query}
    )
     resp.json()


 ():
    
    current_level = get_current_security_level()
    ()
    ()

    attack_mode_active = 
    consecutive_normal = 

     :
        :
            analytics = get_traffic_analytics()
            zones = analytics.get(, {}).get(, {}).get(, [])

             zones  zones[].get():
                data = zones[][][][]
                rps = data[] / 
                threats = data[]

                ()

                 rps > NORMAL_RPS_THRESHOLD   attack_mode_active:
                    ()
                    set_security_level()
                    attack_mode_active = 
                    consecutive_normal = 

                 rps <= NORMAL_RPS_THRESHOLD  attack_mode_active:
                    consecutive_normal += 
                     consecutive_normal >= :
                        ()
                        set_security_level()
                        attack_mode_active = 
                        consecutive_normal = 

         Exception  e:
            ()

        time.sleep(CHECK_INTERVAL)


 __name__ == :
    monitor_and_respond()

监控与告警

Cloudflare 控制台指标

• 防火墙事件——查看被封锁的请求、受挑战的请求、速率受限的请求
• DDoS 分析——攻击规模、持续时间、类型和缓解状态
• 流量分析——按时间的请求量、带宽、错误率
• Bot 分析——Bot 评分分布、已验证 Bot 与自动化威胁对比

告警配置

# 为 DDoS 攻击创建通知策略
curl -X POST "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/alerting/v3/policies" \
  -H "Authorization: Bearer $CF_API_TOKEN" \
  -H "Content-Type: application/json" \
  --data '{
    "name": "DDoS Attack Alert",
    "alert_type": "dos_attack_l7",
    "enabled": true,
    "mechanisms": {
      "email": [{"id": "[e-mail]"}],
      "webhooks": [{"id": "webhook-id"}]
    },
    "filters": {
      "zones": ["'$ZONE_ID'"]
    }
  }'

最佳实践

• 代理所有 DNS 记录——确保所有指向源站的 A/AAAA/CNAME 记录均已代理（橙色云朵图标）
• 隐藏源站 IP——绝不暴露源站服务器 IP；使用 Cloudflare Tunnel 或仅限 Cloudflare IP 访问
• 先以日志模式开始——在切换到"阻止"之前，先以"日志"动作测试 DDoS 规则覆盖
• 分层防御——结合托管规则集、速率限制、WAF 规则和 Bot 管理
• 调整灵敏度——根据流量中的误报率调整 DDoS 规则灵敏度
• 缓存策略——最大化缓存命中率，在攻击期间降低源站负载
• 等候室——为关键页面在流量激增时配置 Cloudflare 等候室（Waiting Room）
• 认证源站——启用认证源站拉取，防止直接攻击源站

参考资料

• Cloudflare DDoS 防护文档
• Cloudflare WAF 文档
• Cloudflare 速率限制
• Cloudflare IP 范围