package main

import (
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"errors"
	"fmt"
	"log"
	"math/big"
	"net"
	"net/http"
	"net/http/httptest"
	"net/http/httputil"
	"time"
)

func test1() {
	src := []byte("观察输出，加密后的数据已经是不可读的了。接下来，用私钥对加密数据进行解密")
	privateKey, _ := rsa.GenerateKey(rand.Reader, 4096)
	// cipherText, _ := rsa.EncryptPKCS1v15(rand.Reader, &privateKey.PublicKey, src)
	// fmt.Println(string(cipherText))
	// src, _ = rsa.DecryptPKCS1v15(rand.Reader, privateKey, cipherText)
	// fmt.Println(string(src))

	hash := sha256.Sum256(src)
	// fmt.Println("hash值是：", hash)
	signature, err := rsa.SignPKCS1v15(rand.Reader, privateKey, crypto.SHA256, hash[:])
	if err != nil {
		log.Fatalf("error creating signature:%v", err)
	}

	verify := func(pub *rsa.PublicKey, msg, signature []byte) error {
		hash := sha256.Sum256(msg)
		return rsa.VerifyPKCS1v15(&privateKey.PublicKey, crypto.SHA256, hash[:], signature)
	}
	fmt.Println(verify(&privateKey.PublicKey, src, []byte("a bad signature")))
	fmt.Println(verify(&privateKey.PublicKey, []byte("a different plain text"), signature))
	fmt.Println(verify(&privateKey.PublicKey, src, signature))
}
func test2() {
	src := []byte("在介绍证书链之前")
	//构造私钥
	privKey, _ := rsa.GenerateKey(rand.Reader, 4096)
	//对明文进行hash计算
	hash := sha256.Sum256(src)
	//生成签名
	signature, _ := rsa.SignPKCS1v15(rand.Reader, privKey, crypto.SHA256, hash[:])
	//定义验证算法
	verify := func(pub *rsa.PublicKey, msg []byte, signature []byte) error {
		hash := sha256.Sum256(msg)
		return rsa.VerifyPKCS1v15(pub, crypto.SHA256, hash[:], signature)
	}
	//验证签名与验证
	fmt.Println(verify(&privKey.PublicKey, src, []byte("wrong signature")))
	fmt.Println(verify(&privKey.PublicKey, []byte("介绍整数两"), signature))
	fmt.Println(verify(&privKey.PublicKey, src, signature))

}

//CreateCert 创建证书
func CreateCert(template, parent *x509.Certificate, pub interface{}, parentPriv interface{}) (
	cert *x509.Certificate, certPEM []byte, err error) {

	certDER, err := x509.CreateCertificate(rand.Reader, template, parent, pub, parentPriv)
	if err != nil {
		return
	}
	// parse the resulting certificate so we can use it again
	cert, err = x509.ParseCertificate(certDER)
	if err != nil {
		return
	}
	//将 certDER 用 pem 编码，生成 certPEM 证书
	b := pem.Block{Type: "CERTIFICATE", Bytes: certDER}
	certPEM = pem.EncodeToMemory(&b)
	return
}

//CertTemplate 证书模板，通过该模板默认设置一些证书需要的字段，比如序列号，组织信息，有效期等等
func CertTemplate() (*x509.Certificate, error) {
	//生成随机的序列号 (不同组织可以有不同的序列号生成方式)
	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		return nil, errors.New("failed to generate serial number: " + err.Error())
	}
	tmpl := x509.Certificate{
		SerialNumber:          serialNumber,
		Subject:               pkix.Name{Organization: []string{"Yhat, Inc."}},
		SignatureAlgorithm:    x509.SHA256WithRSA,
		NotBefore:             time.Now(),
		NotAfter:              time.Now().Add(time.Hour), //1小时的有效期
		BasicConstraintsValid: true,
	}
	return &tmpl, nil
}
func test3() {
	//创建一对密钥
	rootKey, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		log.Fatalln("创建一对密钥失败", err)
	}
	//构造证书模板
	rootCertTmpl, err := CertTemplate()
	if err != nil {
		log.Fatalln("构造证书模板出错", err)
	}
	rootCertTmpl.IsCA = true
	rootCertTmpl.KeyUsage = x509.KeyUsageCertSign | x509.KeyUsageDigitalSignature
	rootCertTmpl.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth}
	rootCertTmpl.IPAddresses = []net.IP{net.ParseIP("127.0.0.1")}

	//根据模板和密钥构造证书
	rootCert, rootCertPEM, err := CreateCert(rootCertTmpl, rootCertTmpl, &rootKey.PublicKey, rootKey)
	if err != nil {
		log.Fatalln("创建证书失败")
	}

	//构造私钥
	rootKeyPEM := pem.EncodeToMemory(&pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(rootKey),
	})

	//构造证书
	_, err = tls.X509KeyPair(rootCertPEM, rootKeyPEM)
	if err != nil {
		log.Fatalln("构造证书失败")
	}

	//客户端设置
	ok := func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("Hi!"))
	}

	//第一种情况,服务端的证书不受客户端信任，因此客户端拒绝了连接.
	/*
		//服务器设置
		s := httptest.NewUnstartedServer(http.HandlerFunc(ok))
		//配置TLS到服务器上
		s.TLS = &tls.Config{
			Certificates: []tls.Certificate{rootTLSCert},
		}
		//启动服务器
		s.StartTLS()
		fmt.Println(s.URL)
		//启动客户端
		_, err = http.Get(s.URL)
		s.Close()
		fmt.Println(err)
	*/
	//对服务器进行设置，
	serverKey, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		log.Fatalln("生成服务器密钥失败")
	}
	serverCertTmpl, err := CertTemplate()
	if err != nil {
		log.Fatalln("生成服务器证书模板失败")
	}
	serverCertTmpl.KeyUsage = x509.KeyUsageDigitalSignature
	serverCertTmpl.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}
	serverCertTmpl.IPAddresses = []net.IP{net.ParseIP("127.0.0.1")}

	_, serverCertPEM, err := CreateCert(serverCertTmpl, rootCert, &serverKey.PublicKey, rootKey)
	if err != nil {
		log.Fatalln("生成服务器证书失败")
	}

	//得到服务器私钥的pem文件
	serverKeyPEM := pem.EncodeToMemory(&pem.Block{
		Type:  "RSA SERVER PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(serverKey),
	})

	//将服务器证书与私钥一起，构造服务器TLS文件
	serverTLSCert, err := tls.X509KeyPair(serverCertPEM, serverKeyPEM)
	if err != nil {
		log.Fatalln("生成服务器TLS文件失败")
	}
	//将客户端用到的授信证书池也配置到服务端，后面也放到客户端内
	certPool := x509.NewCertPool()
	certPool.AppendCertsFromPEM(rootCertPEM)
	s := httptest.NewUnstartedServer(http.HandlerFunc(ok))
	s.TLS = &tls.Config{
		Certificates: []tls.Certificate{serverTLSCert},
		ClientAuth:   tls.RequireAndVerifyClientCert,
		ClientCAs:    certPool,
	}

	//配置客户端
	//生成密钥对
	clientKey, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		log.Fatalln("客户端密钥生成失败")
	}
	//生成客户端证书模板
	clientCertTmpl, err := CertTemplate()
	if err != nil {
		log.Fatalln("生成客户端证书模板失败")
	}
	clientCertTmpl.KeyUsage = x509.KeyUsageDigitalSignature
	clientCertTmpl.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth}
	//根据模板生成证书
	_, clientCertPEM, err := CreateCert(clientCertTmpl, rootCert, &clientKey.PublicKey, rootKey)
	//生成私钥pem文件
	clientKeyPEM := pem.EncodeToMemory(&pem.Block{
		Type:  "CLIENT PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(clientKey),
	})
	clientTLSCert, err := tls.X509KeyPair(clientCertPEM, clientKeyPEM)
	if err != nil {
		log.Fatalln("生成客户端TLS文件出错")
	}
	//将根CA文件放到客户端允许的证书池内
	client := &http.Client{
		Transport: &http.Transport{
			TLSClientConfig: &tls.Config{
				RootCAs:      certPool,
				Certificates: []tls.Certificate{clientTLSCert},
			},
		},
	}

	//启动服务端
	s.StartTLS()
	resp, err := client.Get(s.URL)
	if err != nil {
		log.Fatalln("启动服务端失败")
	}
	dump, err := httputil.DumpResponse(resp, true)
	if err != nil {
		log.Fatalln("没得到服务端反应")
	}
	fmt.Printf("%s\n", dump)
}
func main() {
	// test1()
	// test2()
	test3()
}