[golang]使用mTLS双向加密认证http通信

前言

假设一个场景，服务端部署在内网，客户端需要通过暴露在公网的nginx与服务端进行通信。为了避免在公网进行 http 明文通信造成的信息泄露，nginx与客户端之间的通信应当使用 https 协议，并且nginx也要验证客户端的身份，也就是mTLS双向加密认证通信。

这条通信链路有三个角色：服务端、Nginx、客户端。

• 服务端部署在内网，与nginx使用http通信。
• 客户端在公网，与nginx使用https通信，且双向加密认证。

服务端

服务端只使用http，所以这里用gin框架写个简单的示例，返回客户端一些基本的http信息，比如客户端IP、请求方法、host等。

package main

import (
	"log"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
)

/* 中间件: 获取api处理时长 */
func midElapsed(c *gin.Context) {
	start := time.Now()
	c.Next()
	elapsed := time.Since(start)
	log.Printf("API: %s, elapsed: %s", c.Request.URL.Path, elapsed)
}

/* 处理 GET / 请求 */
func f1(c *gin.Context) {
	// 获取客户端IP
	clientIP := c.ClientIP()

	// 获取请求方法
	method := c.Request.Method

	// 获取协议
	proto := c.Request.Proto

	// 获取host
	host := c.Request.Host

	// 请求Path
	path := c.Request.URL.Path

	log.Printf("客户端IP: %s, 请求方法: %s, 协议: %s, host: %s, path: %s", clientIP, method, proto, host, path)

	// 获取请求头
	headers := c.Request.Header
	for hk, hv := range headers {
		log.Printf("header key: %s, value: %s", hk, hv)
	}

	// 获取名为"mycookie"的cookie
	var cookies []string
	cookie, err := c.Cookie("mycookie")
	if err != nil {
		log.Printf("get cookie [mycookie] error: %s", err)
	} else {
		log.Printf("get cookie [mycookie]: %s", cookie)
		cookies = append(cookies, cookie)
	}

	c.JSON(http.StatusOK, gin.H{
		"clientIP": clientIP,
		"method":   method,
		"proto":    proto,
		"host":     host,
		"headers":  headers,
		"cookies":  cookies,
		"path":     path,
	})
}

func main() {
	r := gin.Default()
	r.Use(midElapsed) // 全局引用计算耗时的中间件
	r.GET("/", f1)
	r.Run("0.0.0.0:8080")
}

生成证书

1. 生成ca根证书。生成过程会要求填写密码、CN、ON、OU等信息，记住密码，填写的信息也要和下一步openssl.cnf文件内容一致。

openssl req -x509 -newkey rsa:4096 -keyout ca.key -out ca.crt -days 3650

2. 新建并编辑文件openssl.cnf文件。req_distinguished_name中内容按需填写，DNS.1要替换成实际域名。

[req]
req_extensions = v3_req
distinguished_name = req_distinguished_name
prompt = no

[req_distinguished_name]
countryName = CN
stateOrProvinceName = Anhui
localityName = Hefei
organizationName = zhangsan
commonName = qw.er.com

[v3_req]
subjectAltName = @alt_names

[alt_names]
DNS.1 = qw.er.com

3. 生成服务端证书

openssl req -newkey rsa:2048 -nodes -keyout server.key -out server.csr -subj "/CN=qw.er.com" -config openssl.cnf

# 提示输入ca私钥的密码
openssl x509 -req -in server.csr -out server.crt -CA ca.crt -CAkey ca.key -CAcreateserial -days 365 -extensions v3_req -extfile openssl.cnf

4. 生成客户端证书

openssl req -newkey rsa:2048 -nodes -keyout client.key -out client.csr -subj "/CN=qw.er.com" -config openssl.cnf

# 提示输入ca私钥的密码
openssl x509 -req -in client.csr -out client.crt -CA ca.crt -CAkey ca.key -CAcreateserial -days 365 -extensions v3_req -extfile openssl.cnf

Nginx配置

nginx反向代理服务端的配置示例如下

server {
    listen 80 ssl;
    server_name qw.er.com;
    ssl_certificate /home/atlas/apps/nginx/certs/qwer/server.crt;
    ssl_certificate_key /home/atlas/apps/nginx/certs/qwer/server.key;
    
    # 校验客户端证书
    ssl_verify_client on;
    ssl_client_certificate /home/atlas/apps/nginx/certs/qwer/ca.crt;
    location / {
        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_pass http://192.168.0.10:8080; # 服务端地址
    }
}

客户端

以下示例使用命令行传参的方式，指定tls证书文件和是否使用tls通信。

package main

import (
	"crypto/tls"
	"crypto/x509"
	"flag"
	"io"
	"log"
	"net/http"
	"os"
	"time"
)

var (
	cafile  = flag.String("cafile", "ca.crt", "ca 证书文件")
	crtfile = flag.String("crtfile", "client.crt", "客户端tls证书")
	keyfile = flag.String("keyfile", "client.key", "客户端tls私钥")
	url     = flag.String("url", "http://127.0.0.1:8080", "url")
	isTls   = flag.Bool("tls", false, "是否使用tls")
)

func tlsClient(cafile, crtfile, keyfile string) *http.Transport {
	// 加载证书和私钥
	clientCert, err := tls.LoadX509KeyPair(crtfile, keyfile)
	if err != nil {
		log.Fatalf("load key pair error: %s", err)
	}

	// 加载ca证书
	clientCA, err := os.ReadFile(cafile)
	if err != nil {
		log.Fatalf("load ca cert error: %s", err)
	}

	// 创建根证书池并添加ca证书
	caCertPool := x509.NewCertPool()
	caCertPool.AppendCertsFromPEM(clientCA)

	// 创建transport
	tr := &http.Transport{
		TLSClientConfig: &tls.Config{
			Certificates: []tls.Certificate{clientCert},
			RootCAs:      caCertPool,
		},
	}

	return tr
}

func main() {
	flag.Parse()

	req, err := http.NewRequest("GET", *url, nil)
	if err != nil {
		log.Fatalf("new request error: %s", err)
	}
	// 自定义HTTP请求头
	req.Header.Set("myheader1", "myheader1value123")
	// 自定义一个cookie对象
	cookie := &http.Cookie{
		Name: "mycookie",
		Value: "mycookievalue",
	}
	req.AddCookie(cookie)

	client := &http.Client{
		Timeout: time.Second * 5,
	}
	if *isTls {
		client.Transport = tlsClient(*cafile, *crtfile, *keyfile)
	}

	resp, err := client.Do(req)
	if err != nil {
		log.Fatalf("get error: %s", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatalf("read error: %s", err)
	}

	log.Printf("body: %+v", string(body))
}

Nginx配置

server {
    listen 80 ssl;
    server_name qw.er.com;
    ssl_certificate /home/elifen/apps/nginx/certs/qwer/server.crt;
    ssl_certificate_key /home/elifen/apps/nginx/certs/qwer/server.key;
    ssl_verify_client on;
    ssl_client_certificate /home/elifen/apps/nginx/qwer/ca.crt;
    location / {
        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_pass http://192.168.0.10:8080;
    }
}

测试

这里需要先确保qw.er.com能被正常解析到nginx服务器，比如配置hosts文件或dns解析记录。

go run main.go -cafile ./ca.crt -crtfile ./client.crt -keyfile ./client.key -url 'https://qw.er.com:80/' -tls

输出示例

2023/08/07 17:34:51 body: {"clientIP":"192.168.0.11","cookies":["mycookievalue"],"headers":{"Accept-Encoding":["gzip"],"Connection":["close"],"Cookie":["mycookie=mycookievalue"],"Myheader1":["myheader1value123"],"User-Agent":["Go-http-client/1.1"],"X-Forwarded-For":["192.168.0.11"],"X-Real-Ip":["192.168.0.11"]},"host":"qw.er.com","method":"GET","path":"/","proto":"HTTP/1.0"}