package main

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"os"
)

func createPriviteKeyAndPublicKey() {
	privKey, err := rsa.GenerateKey(rand.Reader, 4096)
	if err != nil {
		return
	}
	privStream := x509.MarshalPKCS1PrivateKey(privKey)
	block := &pem.Block{
		Type:  "private key",
		Bytes: privStream,
	}
	privFile, err := os.OpenFile("private.pem", os.O_CREATE|os.O_WRONLY, 0666)
	if err != nil {
		return
	}
	err = pem.Encode(privFile, block)
	if err != nil {
		return
	}

	//--------------------------------------------------------
	pubKey := privKey.PublicKey
	pubStream, err := x509.MarshalPKIXPublicKey(&pubKey)
	if err != nil {
		return
	}
	block = &pem.Block{
		Type:  "public key",
		Bytes: pubStream,
	}
	pubFile, err := os.OpenFile("public.pem", os.O_CREATE|os.O_WRONLY, 0666)
	if err != nil {
		return
	}
	err = pem.Encode(pubFile, block)
	if err != nil {
		return
	}
	fmt.Println("成功生成公钥和私钥")
}

//RSAPublicEncrypt 使用公钥对文件加密
func RSAPublicEncrypt(src []byte, pathName string) []byte {
	pubFile, err := os.Open(pathName)
	if err != nil {
		return nil
	}
	fileInfo, err := pubFile.Stat()
	if err != nil {
		return nil
	}
	recevBuf := make([]byte, fileInfo.Size())
	pubFile.Read(recevBuf)
	block, _ := pem.Decode(recevBuf)
	pubInter, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return nil
	}
	pubKey := pubInter.(*rsa.PublicKey)
	msg, err := rsa.EncryptPKCS1v15(rand.Reader, pubKey, src)
	if err != nil {
		return nil
	}
	return msg
}

//RSAPrivateDecrypt 使用私钥对文件解密
func RSAPrivateDecrypt(cipherText []byte, pathName string) []byte {
	privFile, err := os.Open(pathName)
	if err != nil {
		return nil
	}
	fileInfo, err := privFile.Stat()
	if err != nil {
		return nil
	}
	recevFile := make([]byte, fileInfo.Size())
	privFile.Read(recevFile)
	block, _ := pem.Decode(recevFile)
	privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
	if err != nil {
		return nil
	}
	msg, err := rsa.DecryptPKCS1v15(rand.Reader, privateKey, cipherText)
	if err != nil {
		return nil
	}
	return msg
}
func main() {
	// createPriviteKeyAndPublicKey()
	src := []byte("通过某种算法将某种文本转换为其他文本。 ")
	cipherText := RSAPublicEncrypt(src, "public.pem")
	bytes := RSAPrivateDecrypt(cipherText, "private.pem")
	fmt.Println(string(bytes))
}