Nginx TLS 进阶与 mTLS：客户端证书认证、证书轮换与 TLS 1.3 优化

# 查看一个 HTTPS 站点实际协商的协议与套件
openssl s_client -connect api.example.com:443 \
  -servername api.example.com 2>/dev/null | grep -E 'Protocol|Cipher'

server {
    listen      443 ssl;
    http2 on;
    server_name api.example.com;

    ssl_certificate     /etc/nginx/ssl/api.example.com.crt;
    ssl_certificate_key /etc/nginx/ssl/api.example.com.key;

    ssl_protocols       TLSv1.2 TLSv1.3;
    ssl_ciphers         ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256;
    ssl_prefer_server_ciphers off;

    ssl_session_cache   shared:SSL:10m;
    ssl_session_timeout 1d;
    ssl_session_tickets on;
}

# 开启客户端证书认证的最小配置
server {
    listen      443 ssl;
    server_name internal.example.com;

    ssl_client_certificate /etc/nginx/ssl/ca-chain.crt;   # 信任的 CA 列表
    ssl_verify_client      on;                            # 强制校验客户端证书
    ssl_verify_depth       2;                              # 校验链最大深度

    location / {
        proxy_pass http://backend;
        # 把客户端证书的 Subject 透传给后端
        proxy_set_header X-Client-CN      $ssl_client_s_dn;
        proxy_set_header X-Client-Verify  $ssl_client_verify;
    }
}

# 按客户端证书 CN 映射到不同后端
map $ssl_client_s_dn $backend {
    default                default_backend;
    "~CN=svc-order"        order_backend;
    "~CN=svc-user"         user_backend;
    "~CN=svc-payment"      payment_backend;
}

server {
    listen      8443 ssl;
    ssl_client_certificate /etc/nginx/ssl/ca-chain.crt;
    ssl_verify_client      optional;   # 允许未携带证书的请求走单独逻辑

    location / {
        # 校验失败或未提供证书时拒绝
        if ($ssl_client_verify != SUCCESS) {
            return 403;
        }
        proxy_pass http://$backend;
        proxy_set_header X-Client-CN $ssl_client_s_dn;
    }
}

log_format mtls '$remote_addr - [$time_local] "$request" $status '
                'verify=$ssl_client_verify cn=$ssl_client_s_dn '
                'serial=$ssl_client_serial';

server {
    listen      8443 ssl;
    access_log  /var/log/nginx/mtls-access.log mtls;
    ssl_client_certificate /etc/nginx/ssl/ca-chain.crt;
    ssl_verify_client on;
    location / {
        proxy_pass http://backend;
    }
}

# 轮换期：信任列表同时包含新旧 CA
ssl_client_certificate /etc/nginx/ssl/ca-chain-both.crt;
# ca-chain-both.crt = 新 CA + 旧 CA 拼接

# 生成自签名 CA 与客户端证书（示意）
openssl req -x509 -newkey rsa:2048 -nodes \
  -keyout ca.key -out ca.crt -days 3650 -subj "/CN=Internal CA"

openssl req -newkey rsa:2048 -nodes \
  -keyout client.key -out client.csr -subj "/CN=svc-order"

openssl x509 -req -in client.csr -CA ca.crt -CAkey ca.key \
  -CAcreateserial -out client.crt -days 365

ssl_client_certificate /etc/nginx/ssl/ca-chain.crt;
ssl_crl              /etc/nginx/ssl/ca-crl.pem;   # 定期更新吊销列表
ssl_verify_client    on;

server {
    listen      443 ssl;
    http2 on;

    ssl_protocols  TLSv1.2 TLSv1.3;
    ssl_ciphers    TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256;

    # 优先使用 ECDSA 证书可缩短握手；RSA 证书则去掉 ECDSA 套件
    ssl_prefer_server_ciphers off;

    ssl_session_cache   shared:SSL:20m;
    ssl_session_timeout 4h;
    ssl_session_tickets on;

    # OCSP Stapling：由 Nginx 代为查询证书吊销状态，客户端免去额外往返
    ssl_stapling            on;
    ssl_stapling_verify     on;
    resolver                8.8.8.8 8.8.4.4 valid=300s;
}

server {
    listen      443 ssl;
    ssl_protocols  TLSv1.3;
    ssl_early_data on;          # 0-RTT
    # 0-RTT 请求可能重放，后端需要做幂等处理
    proxy_set_header X-Request-ID $request_id;
}

# 安全基线配置清单
server {
    listen      443 ssl;
    ssl_protocols       TLSv1.2 TLSv1.3;
    ssl_ciphers         HIGH:!aNULL:!MD5;
    ssl_prefer_server_ciphers off;
    ssl_session_tickets off;          # 无状态恢复，避免 Ticket 密钥泄露面
    ssl_buffer_size     4k;

    # 强制 HSTS，杜绝降级
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
}

# 不带客户端证书连接，观察服务器是否请求证书
openssl s_client -connect internal.example.com:8443 \
  -servername internal.example.com 2>&1 | grep -E 'Acceptable|verify|alert'

# 带客户端证书连接，确认校验结果
openssl s_client -connect internal.example.com:8443 \
  -servername internal.example.com \
  -cert client.crt -key client.key 2>&1 | grep -E 'verify|Cipher is'