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server.go
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server.go
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// Copyright (C) 2020, IrineSistiana
//
// This file is part of simple-tls.
//
// simple-tls is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// simple-tls is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package main
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/tls"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"log"
"math/big"
"net"
"time"
mathRand "math/rand"
)
func doServer(l net.Listener, certificates []tls.Certificate, dst string, sendPaddingData bool, timeout time.Duration) error {
tlsConfig := new(tls.Config)
tlsConfig.MinVersion = tls.VersionTLS13
tlsConfig.NextProtos = []string{"h2"}
tlsConfig.Certificates = certificates
tlsConfig.MinVersion = tls.VersionTLS13
for {
clientRawConn, err := l.Accept()
if err != nil {
return fmt.Errorf("l.Accept(): %w", err)
}
go func() {
clientTLSConn := tls.Server(clientRawConn, tlsConfig)
defer clientTLSConn.Close()
// check client conn before dialing dst
if err := tls13HandshakeWithTimeout(clientTLSConn, time.Second*5); err != nil {
log.Printf("ERROR: doServer: %s, tls13HandshakeWithTimeout: %v", clientRawConn.RemoteAddr(), err)
return
}
if err := handleClientConn(clientTLSConn, sendPaddingData, dst, timeout); err != nil {
log.Printf("ERROR: doServer: %s, handleClientConn: %v", clientRawConn.RemoteAddr(), err)
return
}
}()
}
}
func handleClientConn(cc net.Conn, sendPaddingData bool, dst string, timeout time.Duration) (err error) {
dstConn, err := net.Dial("tcp", dst)
if err != nil {
return fmt.Errorf("net.Dial: %v", err)
}
defer dstConn.Close()
if sendPaddingData {
cc = newPaddingConn(cc, false, true)
}
if err := openTunnel(dstConn, cc, timeout); err != nil {
return fmt.Errorf("openTunnel: %v", err)
}
return nil
}
func generateCertificate(serverName string) (dnsName string, keyPEM, certPEM []byte, err error) {
//priv key
key, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
if err != nil {
return
}
//serial number
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
err = fmt.Errorf("generate serial number: %v", err)
return
}
// set DNSNames
if len(serverName) == 0 {
dnsName = randServerName()
} else {
dnsName = serverName
}
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{CommonName: dnsName},
DNSNames: []string{dnsName},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
}
certDER, err := x509.CreateCertificate(rand.Reader, &template, &template, &key.PublicKey, key)
if err != nil {
return
}
b, err := x509.MarshalPKCS8PrivateKey(key)
if err != nil {
return
}
keyPEM = pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: b})
certPEM = pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certDER})
return dnsName, keyPEM, certPEM, nil
}
func randServerName() string {
return fmt.Sprintf("%s.%s", randStr(mathRand.Intn(5)+3), randStr(mathRand.Intn(3)+1))
}
func randStr(length int) string {
r := mathRand.New(mathRand.NewSource(time.Now().UnixNano()))
set := "abcdefghijklmnopqrstuvwxyz"
b := make([]byte, length)
for i := range b {
b[i] = set[r.Intn(len(set))]
}
return string(b)
}