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server.go
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server.go
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/*
* This file is part of open-snell.
* open-snell 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.
* open-snell 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 open-snell. If not, see <https://www.gnu.org/licenses/>.
*/
package http
import (
"bufio"
"encoding/base64"
"fmt"
"io"
"io/ioutil"
"math/rand"
"net"
"net/http"
"time"
)
type HTTPObfsServer struct {
net.Conn
buf []byte
bio *bufio.Reader
offset int
firstRequest bool
firstResponse bool
}
func (hos *HTTPObfsServer) Read(b []byte) (int, error) {
if hos.buf != nil {
n := copy(b, hos.buf[hos.offset:])
hos.offset += n
if hos.offset == len(hos.buf) {
hos.offset = 0
hos.buf = nil
}
return n, nil
}
if hos.firstRequest {
bio := bufio.NewReader(hos.Conn)
req, err := http.ReadRequest(bio)
if err != nil {
return 0, err
}
if req.Method != "GET" || req.Header.Get("Connection") != "Upgrade" {
return 0, io.EOF
}
buf, err := ioutil.ReadAll(req.Body)
if err != nil {
return 0, err
}
n := copy(b, buf)
if n < len(buf) {
hos.buf = buf
hos.offset = n
}
req.Body.Close()
hos.bio = bio
hos.firstRequest = false
return n, nil
}
return hos.bio.Read(b)
}
const httpResponseTemplate = "HTTP/1.1 101 Switching Protocols\r\n" +
"Server: nginx/1.%d.%d\r\n" +
"Date: %s\r\n" +
"Upgrade: websocket\r\n" +
"Connection: Upgrade\r\n" +
"Sec-WebSocket-Accept: %s\r\n" +
"\r\n"
var vMajor = rand.Int() % 11
var vMinor = rand.Int() % 12
func (hos *HTTPObfsServer) Write(b []byte) (int, error) {
if hos.firstResponse {
randBytes := make([]byte, 16)
rand.Read(randBytes)
date := time.Now().Format(time.RFC1123)
resp := fmt.Sprintf(httpResponseTemplate, vMajor, vMinor, date, base64.URLEncoding.EncodeToString(randBytes))
_, err := hos.Conn.Write([]byte(resp))
if err != nil {
return 0, err
}
hos.firstResponse = false
_, err = hos.Conn.Write(b)
return len(b), err
}
return hos.Conn.Write(b)
}
func NewHTTPObfsServer(conn net.Conn) net.Conn {
return &HTTPObfsServer{
Conn: conn,
buf: nil,
bio: nil,
offset: 0,
firstRequest: true,
firstResponse: true,
}
}