如何使用 GO 实现一个简单的 HTTP(S) PROXY

• 问题由来

想实现一个简单的 proxy,仅作为玩具使用, 当然其实现成的 lib 有很多, 但是目标很明确,学习一下基本原理

• 是否有其他的代码参考

有的, 有一个 python 版本的, 在 github 上发现的 python proxy code

• 是否有 GO 代码

package main

import (
	"errors"
	"fmt"
	"github.com/valyala/fasthttp"
	"io"
	"log"
	"net"
	"sync"
)

func main() {

	if err := fasthttp.ListenAndServe(":1234", requestHandler); err != nil {
		log.Fatalf("Error in ListenAndServe: %s", err)
	}
}

func processSocket(conn1, conn2 net.Conn, wg *sync.WaitGroup, s string) {
	defer func() {
		fmt.Println("END", s)
		wg.Done()
	}()
	fmt.Println(s)
	var buf []byte
	buf = make([]byte, 4096)
	i, err := conn1.Read(buf)
	buf = buf[:i]
	if err != nil {
		return
	}
	for {
		fmt.Println(s, string(buf))
		conn2.Write(buf)
		buf = buf[:]
		buf = make([]byte, 2<<10<<10) // 10m
		i, err := conn1.Read(buf)
		buf = buf[:i]
		if err != nil {
			if len(buf) > 0 {
				conn2.Write(buf)
			}
			fmt.Println(s, err)
			if errors.Is(err, io.EOF) {
				break

			}
		}
	}

}

func haddleHTTPS(ctx *fasthttp.RequestCtx) {
	h := string(ctx.Request.Host()) // host:port eg. www.baidu.com:443
	curConn := ctx.Conn()
	curConn.Write([]byte("HTTP/1.1 200 OK\r\nContent-Length: 6\r\n\r\nfoo"))
	fmt.Println("haddle:", h)
	remotConn, err := net.Dial("tcp", h)
	if err != nil {
	}
	var wg sync.WaitGroup
	wg.Add(2)
	go processSocket(curConn, remotConn, &wg, "from local to remote")
	go processSocket(remotConn, curConn, &wg, "from remote to local")

	wg.Wait()

}

func haddleHTTP(ctx *fasthttp.RequestCtx) {
	req := fasthttp.AcquireRequest()
	req.SetRequestURIBytes(ctx.Request.RequestURI())
	//req.Header.SetMethodBytes(ctx.Method())
	req.Header = ctx.Request.Header
	req.SetBody(ctx.Request.Body())
	client := &fasthttp.Client{}
	resp := fasthttp.AcquireResponse()
	client.Do(req, resp)
	body := resp.Body()
	fmt.Println(body)
	ctx.Write(body)
}

func requestHandler(ctx *fasthttp.RequestCtx) {
	method := string(ctx.Method())
	if method == "CONNECT" {
		// https
		haddleHTTPS(ctx)
		return
	}
	// http
	haddleHTTP(ctx)
	return

}

• 代码是否可以正常工作

不行, http 是没有问题的, https 存在问题

• 问题日志 /描述

➜  ~ curl https://www.baidu.com -vvv
* Uses proxy env variable https_proxy == 'http://127.0.0.1:1234'
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 1234 (#0)
* allocate connect buffer!
* Establish HTTP proxy tunnel to www.baidu.com:443
> CONNECT www.baidu.com:443 HTTP/1.1
> Host: www.baidu.com:443
> User-Agent: curl/7.64.1
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 200 OK
< Content-Length: 6
* Ignoring Content-Length in CONNECT 200 response
<
* Proxy replied 200 to CONNECT request
* CONNECT phase completed!
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/cert.pem
  CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* CONNECT phase completed!
* CONNECT phase completed!
* error:1400410B:SSL routines:CONNECT_CR_SRVR_HELLO:wrong version number
* Closing connection 0
curl: (35) error:1400410B:SSL routines:CONNECT_CR_SRVR_HELLO:wrong version number

• 是否自行 debug

有的, 发现 local to server 的时候, read 出现了 error, err: ECONNRESET (54) 然后 接下来就 EOF 了, 所以就退出了, 但是拿到这个 error 的时候, curl 就已经结束了, 所以拿到 EOF 也是正常行为, 主要在于不知道为啥会 curl 会断掉

• 主题目标

1. 想知道为什么 curl 会断掉
2. 有没有什么解决办法[在上述代码中修改]
3. 或者有其他代码编写方式