/
client.go
151 lines (121 loc) · 3.43 KB
/
client.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
package websocket
import (
"bufio"
"context"
"crypto/tls"
"fmt"
"net"
"net/http"
"net/url"
"time"
)
// Dialer is a type which represents the client settings to establish a
// WebSocket connection.
type Dialer struct {
HandshakeTimeout time.Duration
TLSConfig *tls.Config
wsKey string
}
// Dial creates a new client WebSocket connection using DialContext with a background context.
func (d *Dialer) Dial(urlStr string) (*Conn, error) {
return d.DialContext(context.Background(), urlStr)
}
// DialContext creates a new client WebSocket connection.
//
// At first, it opens a new tcp connection over which it sends http handshake
// request for switching protocol to WebSocket. If handshake fails, DialContext returns
// HandshakeError with detailed reason about error.
func (d *Dialer) DialContext(ctx context.Context, urlStr string) (*Conn, error) {
addr, err := url.Parse(urlStr)
if err != nil {
return nil, err
}
switch addr.Scheme {
case "ws":
addr.Scheme = "http"
case "wss":
addr.Scheme = "https"
default:
return nil, fmt.Errorf("bad url schema (must be ws or wss)")
}
if d.HandshakeTimeout != 0 {
var cancel context.CancelFunc
ctx, cancel = context.WithTimeout(ctx, d.HandshakeTimeout)
defer cancel()
}
wsKey, err := randomWebsocketKey()
if err != nil {
return nil, err
}
d.wsKey = wsKey
req, err := d.prepareHandshakeRequest(ctx, addr.String())
if err != nil {
return nil, err
}
netConn, err := net.Dial("tcp", extractHostPort(addr))
if err != nil {
return nil, err
}
if addr.Scheme == "https" {
tlsConn, err := d.tlsHandshake(netConn)
if err != nil {
return nil, err
}
netConn = tlsConn
}
if err = req.Write(netConn); err != nil {
return nil, err
}
r := bufio.NewReader(netConn)
if err = d.handleHandshakeResponse(r, req); err != nil {
return nil, err
}
return &Conn{
conn: netConn,
rw: bufio.NewReadWriter(r, bufio.NewWriter(netConn)),
}, nil
}
func (d *Dialer) prepareHandshakeRequest(ctx context.Context, addr string) (*http.Request, error) {
req, err := http.NewRequestWithContext(ctx, http.MethodGet, addr, nil)
if err != nil {
return nil, err
}
req.Header.Set("Upgrade", "WebSocket")
req.Header.Set("Connection", "Upgrade")
req.Header.Set("Sec-WebSocket-Key", d.wsKey)
req.Header.Set("Sec-WebSocket-Version", "13")
return req, nil
}
func (d *Dialer) handleHandshakeResponse(r *bufio.Reader, req *http.Request) error {
resp, err := http.ReadResponse(r, req)
if err != nil {
return err
}
defer func() { _ = resp.Body.Close() }()
if resp.StatusCode != http.StatusSwitchingProtocols {
return HandshakeError{"bad status code, expect status switching protocols (101)"}
}
if !checkHeaderContains(resp.Header, "Upgrade", "WebSocket") {
return HandshakeError{"response Upgrade header value doesn't equal WebSocket"}
}
if !checkHeaderContains(resp.Header, "Connection", "Upgrade") {
return HandshakeError{"response Connection header value doesn't equal Upgrade"}
}
if resp.Header.Get("Sec-Websocket-Accept") != hashWebsocketKey(d.wsKey) {
return HandshakeError{"bad calculated Sec-Websocket-Accept header value"}
}
return nil
}
func (d *Dialer) tlsHandshake(netConn net.Conn) (*tls.Conn, error) {
var tlsConfig *tls.Config
if d.TLSConfig != nil {
tlsConfig = d.TLSConfig.Clone()
} else {
tlsConfig = &tls.Config{}
}
tlsConn := tls.Client(netConn, tlsConfig)
if err := tlsConn.Handshake(); err != nil {
return nil, err
}
return tlsConn, nil
}