TLS 1.3 与 mTLS 企业级安全：构建零信任网络访问体系

# ECDHE 密钥交换原理
客户端: 生成 (client_public, client_private)
服务器: 生成 (server_public, server_private)

客户端 ──► 发送 client_public
服务器 ◄── 发送 server_public

共享密钥 = ECDH(client_private, server_public)
              = ECDH(server_private, client_public)
              = 双方独立计算得到相同结果

# 使用 EasyRSA 或 Step CA 搭建私有 PKI
# 这里以 Step CA 为例

# 安装 step-ca
wget https://github.com/smallstep/cli/releases/latest/download/step-ca_linux_amd64.tar.gz
tar -xzvf step-ca_linux_amd64.tar.gz
sudo mv step-ca /usr/local/bin/

# 初始化 PKI
step ca init --name="My Enterprise CA" --dns=ca.internal.example.com

# 启动 CA
step-ca $(step path)/config/ca.json

# 在服务器上生成私钥和 CSR
step crypto keypair /etc/ssl/server.key /etc/ssl/server.pub
step certificate request /etc/ssl/server.csr \
  --cn="vpn.example.com" \
  --san="vpn.example.com" \
  --san="10.0.0.1" \
  --signer=/etc/ssl/server.key

# 提交 CSR 到 CA，获取证书
step certificate sign /etc/ssl/server.csr \
  --ca-url=https://ca.internal.example.com \
  --root=/etc/ssl/root.crt \
  --not-after=8760h \
  > /etc/ssl/server.crt

# 为用户颁发客户端证书
step certificate create "user@example.com" \
  /etc/ssl/users/alice.crt \
  /etc/ssl/users/alice.key \
  --ca-url=https://ca.internal.example.com \
  --root=/etc/ssl/root.crt \
  --not-after=2160h \
  --signer=/etc/ssl/users/alice.key

# 导出为 PKCS#12（浏览器兼容格式）
step certificate p12 export /etc/ssl/users/alice.crt \
  --certificate=/etc/ssl/users/alice.key \
  --ca=/etc/ssl/root.crt \
  --password=changeit \
  > /etc/ssl/users/alice.p12

server {
    listen 443 ssl;
    server_name vpn.example.com;

    # 服务器证书
    ssl_certificate /etc/ssl/server.crt;
    ssl_certificate_key /etc/ssl/server.key;

    # 客户端证书验证
    ssl_client_certificate /etc/ssl/root.crt;
    ssl_verify_client on;
    ssl_verify_depth 2;

    # TLS 1.3 配置
    ssl_protocols TLSv1.3;
    ssl_ciphers TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256;
    ssl_ecdh_curve X25519:secp384r1;
    ssl_prefer_server_ciphers off;

    # OCSP 装订
    ssl_stapling on;
    ssl_stapling_verify on;

    # 安全头
    add_header Strict-Transport-Security "max-age=63072000" always;
    add_header X-Frame-Options DENY;
    add_header X-Content-Type-Options nosniff;

    location / {
        # 仅允许验证通过的客户端
        if ($ssl_client_verify != SUCCESS) {
            return 403;
        }

        # 将客户端证书信息传递给后端
        proxy_set_header X-Client-Cert $ssl_client_escaped_cert;
        proxy_pass https://backend;
    }
}

{
  "inbounds": [
    {
      "type": "trojan",
      "listen": "0.0.0.0",
      "listen_port": 443,
      "tls": {
        "enabled": true,
        "min_version": "1.3",
        "certificate": "/etc/ssl/server.crt",
        "key": "/etc/ssl/server.key",
        "client_auth": true,
        "client_ca": "/etc/ssl/root.crt"
      }
    }
  ]
}

# /etc/nginx/conf.d/mtls-proxy.conf

# 上游服务器（内部）
upstream backend {
    server 127.0.0.1:10080;
    keepalive 32;
}

# 主服务器块
server {
    listen 443 ssl;
    listen [::]:443 ssl;
    server_name proxy.example.com;

    # 服务器证书（由内部 CA 颁发）
    ssl_certificate /etc/ssl/internal/server.crt;
    ssl_certificate_key /etc/ssl/internal/server.key;

    # 客户端证书验证（mTLS 核心）
    ssl_client_certificate /etc/ssl/internal/ca.crt;
    ssl_verify_client optional_no_ca;
    ssl_verify_depth 3;

    # TLS 1.3 配置
    ssl_protocols TLSv1.3;
    ssl_ciphers TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256;
    ssl_ecdh_curve X25519:secp384r1;
    ssl_prefer_server_ciphers off;

    # Session 缓存
    ssl_session_timeout 1d;
    ssl_session_cache shared:SSL:50m;
    ssl_session_tickets off;

    # OCSP 装订
    ssl_stapling on;
    ssl_stapling_verify on;
    resolver 223.5.5.5 valid=300s;

    # 安全响应头
    add_header Strict-Transport-Security "max-age=63072000; includeSubDomains" always;
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;

    # 访问日志
    access_log /var/log/nginx/mtls-access.log;
    error_log /var/log/nginx/mtls-error.log;

    location / {
        # 将客户端证书信息传递给后端
        proxy_pass https://backend;
        proxy_http_version 1.1;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;

        # 传递客户端证书信息
        proxy_set_header X-Client-DN $ssl_client_s_dn;
        proxy_set_header X-Client-Verify $ssl_client_verify;

        # 连接复用
        proxy_set_header Connection "";

        # 超时配置
        proxy_connect_timeout 30s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
    }

    # 健康检查端点
    location /health {
        access_log off;
        return 200 "OK\n";
        add_header Content-Type text/plain;
    }
}

# HTTP 重定向到 HTTPS
server {
    listen 80;
    listen [::]:80;
    server_name proxy.example.com;
    return 301 https://$server_name$request_uri;
}

# 安装 certbot
sudo apt install certbot python3-certbot-nginx

# 获取证书（DNS 验证方式，适合内网）
certbot certonly \
  --manual \
  --preferred-challenges=dns \
  --email admin@example.com \
  --server https://acme-v02.api.letsencrypt.org/directory \
  --agree-tos \
  -d proxy.example.com

# 自动续期配置
sudo crontab -e
# 添加：0 0 * * * certbot renew --quiet

# 基于客户端证书 O 的访问控制
geo $allowed_ou {
    default 0;
    # 允许研发部证书
    "OU=Engineering,O=Example Inc" 1;
    # 允许运维部证书
    "OU=Operations,O=Example Inc" 1;
}

server {
    # ... SSL 配置 ...

    location /internal-api/ {
        if ($ssl_client_verify != SUCCESS) {
            return 403;
        }

        # 提取 OU 字段做细粒度控制
        set $client_ou "";
        set $client_cn "";

        # 使用 map 从 DN 中提取字段
        if ($ssl_client_s_dn ~ *,O=(.+)) {
            set $client_ou $1;
        }

        # 访问控制
        if ($allowed_ou = 0) {
            return 403 "Access denied: invalid certificate";
        }

        proxy_pass https://internal-api-backend;
    }
}

# 方式一：CRL（Certificate Revocation List）
# 在 CA 服务器上发布吊销列表
step ca crl list

# 方式二：OCSP（Online Certificate Status Protocol）
# 实时检查证书状态
openssl ocsp \
  -CA /etc/ssl/root.crt \
  -issuer /etc/ssl/root.crt \
  -cert /etc/ssl/client.crt \
  -url http://ocsp.example.com \
  -text

# 方式三：OCSP 装订（服务器自动获取）
# Nginx 配置
ssl_stapling on;
ssl_stapling_verify on;

#!/bin/bash
# check-cert-expiry.sh

CERT_FILE="/etc/ssl/server.crt"
WARN_DAYS=30
CRIT_DAYS=7

EXPIRY_DATE=$(openssl x509 -in "$CERT_FILE" -noout -enddate | cut -d= -f2)
EXPIRY_EPOCH=$(date -d "$EXPIRY_DATE" +%s)
NOW_EPOCH=$(date +%s)
DAYS_LEFT=$(( ($EXPIRY_EPOCH - $NOW_EPOCH) / 86400 ))

if [ $DAYS_LEFT -le $CRIT_DAYS ]; then
    echo "CRITICAL: Certificate expires in $DAYS_LEFT days"
    # 发送告警（PagerDuty/Slack/Email）
    exit 2
elif [ $DAYS_LEFT -le $WARN_DAYS ]; then
    echo "WARNING: Certificate expires in $DAYS_LEFT days"
    # 发送警告
    exit 1
else
    echo "OK: Certificate valid for $DAYS_LEFT days"
    exit 0
fi

# 使用 testssl.sh 进行全面 TLS 检测
docker run --rm -ti drwetter/testssl.sh \
  --protocols \
  --ciphers \
  --headers \
  --vulnerabilities \
  https://your-proxy-server.com

# 关键检查项
# ✅ TLS 1.3 已启用
# ✅ TLS 1.2 已禁用或仅启用安全套件
# ✅ 前向保密已启用（DH/ECDH）
# ✅ 证书链完整
# ✅ 私钥安全（无密码保护的私钥是大忌）
# ✅ 无弱加密套件（SSLv2/v3, RC4, 3DES 等）