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
|
package tls
import (
"encoding/binary"
"errors"
"strings"
"v2ray.com/core/common"
)
type SniffHeader struct {
domain string
}
func (h *SniffHeader) Protocol() string {
return "tls"
}
func (h *SniffHeader) Domain() string {
return h.domain
}
var errNotTLS = errors.New("not TLS header")
var errNotClientHello = errors.New("not client hello")
func IsValidTLSVersion(major, minor byte) bool {
return major == 3
}
// ReadClientHello returns server name (if any) from TLS client hello message.
// https://github.com/golang/go/blob/master/src/crypto/tls/handshake_messages.go#L300
func ReadClientHello(data []byte, h *SniffHeader) error {
if len(data) < 42 {
return common.ErrNoClue
}
sessionIDLen := int(data[38])
if sessionIDLen > 32 || len(data) < 39+sessionIDLen {
return common.ErrNoClue
}
data = data[39+sessionIDLen:]
if len(data) < 2 {
return common.ErrNoClue
}
// cipherSuiteLen is the number of bytes of cipher suite numbers. Since
// they are uint16s, the number must be even.
cipherSuiteLen := int(data[0])<<8 | int(data[1])
if cipherSuiteLen%2 == 1 || len(data) < 2+cipherSuiteLen {
return errNotClientHello
}
data = data[2+cipherSuiteLen:]
if len(data) < 1 {
return common.ErrNoClue
}
compressionMethodsLen := int(data[0])
if len(data) < 1+compressionMethodsLen {
return common.ErrNoClue
}
data = data[1+compressionMethodsLen:]
if len(data) == 0 {
return errNotClientHello
}
if len(data) < 2 {
return errNotClientHello
}
extensionsLength := int(data[0])<<8 | int(data[1])
data = data[2:]
if extensionsLength != len(data) {
return errNotClientHello
}
for len(data) != 0 {
if len(data) < 4 {
return errNotClientHello
}
extension := uint16(data[0])<<8 | uint16(data[1])
length := int(data[2])<<8 | int(data[3])
data = data[4:]
if len(data) < length {
return errNotClientHello
}
if extension == 0x00 { /* extensionServerName */
d := data[:length]
if len(d) < 2 {
return errNotClientHello
}
namesLen := int(d[0])<<8 | int(d[1])
d = d[2:]
if len(d) != namesLen {
return errNotClientHello
}
for len(d) > 0 {
if len(d) < 3 {
return errNotClientHello
}
nameType := d[0]
nameLen := int(d[1])<<8 | int(d[2])
d = d[3:]
if len(d) < nameLen {
return errNotClientHello
}
if nameType == 0 {
serverName := string(d[:nameLen])
// An SNI value may not include a
// trailing dot. See
// https://tools.ietf.org/html/rfc6066#section-3.
if strings.HasSuffix(serverName, ".") {
return errNotClientHello
}
h.domain = serverName
return nil
}
d = d[nameLen:]
}
}
data = data[length:]
}
return errNotTLS
}
func SniffTLS(b []byte) (*SniffHeader, error) {
if len(b) < 5 {
return nil, common.ErrNoClue
}
if b[0] != 0x16 /* TLS Handshake */ {
return nil, errNotTLS
}
if !IsValidTLSVersion(b[1], b[2]) {
return nil, errNotTLS
}
headerLen := int(binary.BigEndian.Uint16(b[3:5]))
if 5+headerLen > len(b) {
return nil, common.ErrNoClue
}
h := &SniffHeader{}
err := ReadClientHello(b[5:5+headerLen], h)
if err == nil {
return h, nil
}
return nil, err
}
|
