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websocket.go
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websocket.go
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package cdp
import (
"bufio"
"context"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"net/url"
"sync"
)
var _ WebSocketable = &WebSocket{}
// WebSocket client for chromium. It only implements a subset of WebSocket protocol.
// Both the Read and Write are thread-safe.
// Limitation: https://bugs.chromium.org/p/chromium/issues/detail?id=1069431
// Ref: https://tools.ietf.org/html/rfc6455
type WebSocket struct {
// Dialer is usually used for proxy
Dialer Dialer
lock sync.Mutex
conn net.Conn
r *bufio.Reader
}
// Connect to browser
func (ws *WebSocket) Connect(ctx context.Context, wsURL string, header http.Header) error {
if ws.conn != nil {
panic("duplicated connection: " + wsURL)
}
u, err := url.Parse(wsURL)
if err != nil {
return err
}
ws.initDialer(u)
conn, err := ws.Dialer.DialContext(ctx, "tcp", u.Host)
if err != nil {
return err
}
ws.conn = conn
ws.r = bufio.NewReader(conn)
return ws.handshake(ctx, u, header)
}
// Close the underlying connection.
func (ws *WebSocket) Close() error {
return ws.conn.Close()
}
func (ws *WebSocket) initDialer(u *url.URL) {
if ws.Dialer != nil {
return
}
if u.Scheme == "wss" {
ws.Dialer = &tlsDialer{}
if u.Port() == "" {
u.Host += ":443"
}
} else {
ws.Dialer = &net.Dialer{}
}
}
// Send a message to browser.
// Because we use zero-copy design, it will modify the content of the msg.
// It won't allocate new memory.
func (ws *WebSocket) Send(msg []byte) error {
err := ws.send(msg)
if err != nil {
_ = ws.Close()
}
return err
}
func (ws *WebSocket) send(msg []byte) error {
// FIN is alway true, Opcode is always text frame.
header := [18]byte{0b1000_0001, 0b1000_0000}
mask := []byte{0, 1, 2, 3}
size := len(msg)
fieldLen := 0
switch {
case size <= 125:
header[1] |= byte(size)
case size < 65536:
header[1] |= 126
fieldLen = 2
default:
header[1] |= 127
fieldLen = 8
}
var i int
for i = 0; i < fieldLen; i++ {
digit := (fieldLen - i - 1) * 8
header[i+2] = byte((size >> digit) & 0xff)
}
copy(header[i+2:], mask)
for i := range msg {
msg[i] = msg[i] ^ mask[i%4]
}
data := make([]byte, i+6+len(msg))
copy(data, header[:i+6])
copy(data[i+6:], msg)
_, err := ws.conn.Write(data)
return err
}
// Read a message from browser
func (ws *WebSocket) Read() ([]byte, error) {
b, err := ws.read()
if err != nil {
_ = ws.Close()
return nil, err
}
return b, nil
}
func (ws *WebSocket) read() ([]byte, error) {
ws.lock.Lock()
defer ws.lock.Unlock()
_, err := ws.r.ReadByte()
if err != nil {
return nil, err
}
b, err := ws.r.ReadByte()
if err != nil {
return nil, err
}
size := 0
fieldLen := 0
b &= 0x7f
switch {
case b <= 125:
size = int(b)
case b == 126:
fieldLen = 2
case b == 127:
fieldLen = 8
}
for i := 0; i < fieldLen; i++ {
b, err := ws.r.ReadByte()
if err != nil {
return nil, err
}
size = size<<8 + int(b)
}
data := make([]byte, size)
_, err = io.ReadFull(ws.r, data)
return data, err
}
// ErrBadHandshake type
type ErrBadHandshake struct {
Status string
Body string
}
func (e *ErrBadHandshake) Error() string {
return fmt.Sprintf(
"websocket bad handshake: %s. %s",
e.Status, e.Body,
)
}
func (ws *WebSocket) handshake(ctx context.Context, u *url.URL, header http.Header) error {
req := (&http.Request{Method: http.MethodGet, URL: u, Header: http.Header{
"Upgrade": {"websocket"},
"Connection": {"Upgrade"},
"Sec-WebSocket-Key": {"nil"},
"Sec-WebSocket-Version": {"13"},
}}).WithContext(ctx)
for k, vs := range header {
if k == "Host" && len(vs) > 0 {
req.Host = vs[0]
} else {
req.Header[k] = vs
}
}
err := req.Write(ws.conn)
if err != nil {
return err
}
res, err := http.ReadResponse(ws.r, req)
if err != nil {
return err
}
defer func() { _ = res.Body.Close() }()
if res.StatusCode != http.StatusSwitchingProtocols ||
res.Header.Get("Sec-Websocket-Accept") != "Q67D9eATKx531lK8F7u2rqQNnNI=" {
body, _ := ioutil.ReadAll(res.Body)
return &ErrBadHandshake{
Status: res.Status,
Body: string(body),
}
}
return nil
}