Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
148 lines (131 sloc) 3.11 KB
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
}
switch extension {
case 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
}
You can’t perform that action at this time.