transport := &http.Transport{TLSClientConfig: TLSClientConfig}

outReq.Header.Add("X-Remote-User", "admin")
outReq.Header.Add("X-Remote-Group", "system:master")

outReq.URL.Host = p.KubeHost
outReq.URL.Scheme = "https"

mkdir -pv certs
cp -rv /etc/kubernetes/pki/{ca.crt,front-proxy-client.{crt,key}} certs
chown ${username}:${username} -R certs  # set username as your normal username

package main

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"net/textproto"
	"strings"
)

const (
	caCertPath               = "certs/ca.crt"
	frontProxyClientCertPath = "certs/front-proxy-client.crt"
	frontProxyClientKeyPath  = "certs/front-proxy-client.key"
)

var (
	// Hop-by-hop headers. These are removed when sent to the backend.
	// As of RFC 7230, hop-by-hop headers are required to appear in the
	// Connection header field. These are the headers defined by the
	// obsoleted RFC 2616 (section 13.5.1) and are used for backward
	// compatibility.
	hopHeaders = []string{
		"Connection",
		"Proxy-Connection", // non-standard but still sent by libcurl and rejected by e.g. google
		"Keep-Alive",
		"Proxy-Authenticate",
		"Proxy-Authorization",
		"Te",      // canonicalized version of "TE"
		"Trailer", // not Trailers per URL above; https://www.rfc-editor.org/errata_search.php?eid=4522
		"Transfer-Encoding",
		"Upgrade",
	}
)

type KubeAccessProxy struct {
	KubeHost        string
	TLSClientConfig *tls.Config
}

func (p *KubeAccessProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	transport := &http.Transport{TLSClientConfig: p.TLSClientConfig}

	ctx := req.Context()
	outReq := req.Clone(ctx)

	if req.ContentLength == 0 {
		outReq.Body = nil
	}
	if outReq.Header == nil {
		outReq.Header = make(http.Header)
	}

	outReq.Close = false

	if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
		// If we aren't the first proxy retain prior
		// X-Forwarded-For information as a comma+space
		// separated list and fold multiple headers into one.
		prior, ok := outReq.Header["X-Forwarded-For"]
		omit := ok && prior == nil // Issue 38079: nil now means don't populate the header
		if len(prior) > 0 {
			clientIP = strings.Join(prior, ", ") + ", " + clientIP
		}
		if !omit {
			outReq.Header.Set("X-Forwarded-For", clientIP)
		}
	}
	outReq.URL.Host = p.KubeHost
	outReq.URL.Scheme = "https"
	log.Printf("request url: %s", outReq.URL)
	outReq.Header.Add("X-Remote-User", "admin")
	outReq.Header.Add("X-Remote-Group", "system:master")

	res, err := transport.RoundTrip(outReq)
	if err != nil {
		rw.WriteHeader(http.StatusBadGateway)
		log.Printf("err: %s", err.Error())
		return
	}

	removeConnectionHeaders(res.Header)

	for _, h := range hopHeaders {
		res.Header.Del(h)
	}

	copyHeader(rw.Header(), res.Header)

	// The "Trailer" header isn't included in the Transport's response,
	// at least for *http.Transport. Build it up from Trailer.
	announcedTrailers := len(res.Trailer)
	if announcedTrailers > 0 {
		trailerKeys := make([]string, 0, len(res.Trailer))
		for k := range res.Trailer {
			trailerKeys = append(trailerKeys, k)
		}
		rw.Header().Add("Trailer", strings.Join(trailerKeys, ", "))
	}

	rw.WriteHeader(res.StatusCode)

	err = p.copyResponse(rw, res.Body)
	if err != nil {
		defer res.Body.Close()
		panic(http.ErrAbortHandler)
	}
	res.Body.Close() // close now, instead of defer, to populate res.Trailer

	if len(res.Trailer) > 0 {
		// Force chunking if we saw a response trailer.
		// This prevents net/http from calculating the length for short
		// bodies and adding a Content-Length.
		if fl, ok := rw.(http.Flusher); ok {
			fl.Flush()
		}
	}

	if len(res.Trailer) == announcedTrailers {
		copyHeader(rw.Header(), res.Trailer)
		return
	}

	for k, vv := range res.Trailer {
		k = http.TrailerPrefix + k
		for _, v := range vv {
			rw.Header().Add(k, v)
		}
	}
}

func (p *KubeAccessProxy) copyResponse(dst io.Writer, src io.Reader) error {
	var buf []byte
	_, err := p.copyBuffer(dst, src, buf)
	return err
}

// copyBuffer returns any write errors or non-EOF read errors, and the amount
// of bytes written.
func (p *KubeAccessProxy) copyBuffer(dst io.Writer, src io.Reader, buf []byte) (int64, error) {
	if len(buf) == 0 {
		buf = make([]byte, 32*1024)
	}
	var written int64
	for {
		nr, rerr := src.Read(buf)
		if rerr != nil && rerr != io.EOF && rerr != context.Canceled {
			log.Printf("httputil: ReverseProxy read error during body copy: %v", rerr)
		}
		if nr > 0 {
			nw, werr := dst.Write(buf[:nr])
			if nw > 0 {
				written += int64(nw)
			}
			if werr != nil {
				return written, werr
			}
			if nr != nw {
				return written, io.ErrShortWrite
			}
		}
		if rerr != nil {
			if rerr == io.EOF {
				rerr = nil
			}
			return written, rerr
		}
	}
}
func removeConnectionHeaders(h http.Header) {
	for _, f := range h["Connection"] {
		for _, sf := range strings.Split(f, ",") {
			if sf = textproto.TrimString(sf); sf != "" {
				h.Del(sf)
			}
		}
	}
}
func copyHeader(dst, src http.Header) {
	for k, vv := range src {
		for _, v := range vv {
			dst.Add(k, v)
		}
	}
}

func main() {
	caCertData, err := ioutil.ReadFile(caCertPath)
	if err != nil {
		panic(err)
	}
	frontProxyClientCertData, err := ioutil.ReadFile(frontProxyClientCertPath)
	if err != nil {
		panic(err)
	}
	frontProxyClientKeyData, err := ioutil.ReadFile(frontProxyClientKeyPath)
	if err != nil {
		panic(err)
	}
	roots := x509.NewCertPool()
	ok := roots.AppendCertsFromPEM(caCertData)
	if !ok {
		panic("failed to parse root certificate")
	}
	proxyCert, err := tls.X509KeyPair(frontProxyClientCertData, frontProxyClientKeyData)
	if err != nil {
		panic(err)
	}
	proxyCerts := []tls.Certificate{proxyCert}
	tlsConfig := &tls.Config{
		Certificates: proxyCerts,
		RootCAs:      roots,
	}
	handler := &KubeAccessProxy{
		KubeHost:        "192.168.0.2:6443",
		TLSClientConfig: tlsConfig,
	}
	log.Fatal(http.ListenAndServe("localhost:8080", handler))
}