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sniffer.go
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sniffer.go
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package impl
import (
"bytes"
"strings"
"v2ray.com/core/app/proxyman"
"v2ray.com/core/common/serial"
)
var (
ErrMoreData = newError("need more data")
ErrInvalidData = newError("invalid data")
)
func ContainsValidHTTPMethod(b []byte) bool {
if len(b) == 0 {
return false
}
parts := bytes.Split(b, []byte{' '})
part0Trimed := strings.ToLower(string(bytes.Trim(parts[0], " ")))
return part0Trimed == "get" || part0Trimed == "post" ||
part0Trimed == "head" || part0Trimed == "put" ||
part0Trimed == "delete" || part0Trimed == "options" || part0Trimed == "connect"
}
func SniffHTTP(b []byte) (string, error) {
if len(b) == 0 {
return "", ErrMoreData
}
headers := bytes.Split(b, []byte{'\n'})
if !ContainsValidHTTPMethod(headers[0]) {
return "", ErrInvalidData
}
for i := 1; i < len(headers); i++ {
header := headers[i]
if len(header) == 0 {
return "", ErrInvalidData
}
parts := bytes.SplitN(header, []byte{':'}, 2)
if len(parts) != 2 {
return "", ErrInvalidData
}
key := strings.ToLower(string(parts[0]))
value := strings.ToLower(string(bytes.Trim(parts[1], " ")))
if key == "host" {
domain := strings.Split(value, ":")
return strings.TrimSpace(domain[0]), nil
}
}
return "", ErrMoreData
}
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) (string, error) {
if len(data) < 42 {
return "", ErrMoreData
}
sessionIDLen := int(data[38])
if sessionIDLen > 32 || len(data) < 39+sessionIDLen {
return "", ErrInvalidData
}
data = data[39+sessionIDLen:]
if len(data) < 2 {
return "", ErrMoreData
}
// 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 "", ErrInvalidData
}
data = data[2+cipherSuiteLen:]
if len(data) < 1 {
return "", ErrMoreData
}
compressionMethodsLen := int(data[0])
if len(data) < 1+compressionMethodsLen {
return "", ErrMoreData
}
data = data[1+compressionMethodsLen:]
if len(data) == 0 {
return "", ErrInvalidData
}
if len(data) < 2 {
return "", ErrInvalidData
}
extensionsLength := int(data[0])<<8 | int(data[1])
data = data[2:]
if extensionsLength != len(data) {
return "", ErrInvalidData
}
for len(data) != 0 {
if len(data) < 4 {
return "", ErrInvalidData
}
extension := uint16(data[0])<<8 | uint16(data[1])
length := int(data[2])<<8 | int(data[3])
data = data[4:]
if len(data) < length {
return "", ErrInvalidData
}
switch extension {
case 0x00: /* extensionServerName */
d := data[:length]
if len(d) < 2 {
return "", ErrInvalidData
}
namesLen := int(d[0])<<8 | int(d[1])
d = d[2:]
if len(d) != namesLen {
return "", ErrInvalidData
}
for len(d) > 0 {
if len(d) < 3 {
return "", ErrInvalidData
}
nameType := d[0]
nameLen := int(d[1])<<8 | int(d[2])
d = d[3:]
if len(d) < nameLen {
return "", ErrInvalidData
}
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 "", ErrInvalidData
}
return serverName, nil
}
d = d[nameLen:]
}
}
data = data[length:]
}
return "", ErrInvalidData
}
func SniffTLS(b []byte) (string, error) {
if len(b) < 5 {
return "", ErrMoreData
}
if b[0] != 0x16 /* TLS Handshake */ {
return "", ErrInvalidData
}
if !IsValidTLSVersion(b[1], b[2]) {
return "", ErrInvalidData
}
headerLen := int(serial.BytesToUint16(b[3:5]))
if 5+headerLen > len(b) {
return "", ErrMoreData
}
return ReadClientHello(b[5 : 5+headerLen])
}
type Sniffer struct {
slist []func([]byte) (string, error)
err []error
}
func NewSniffer(sniferList []proxyman.KnownProtocols) *Sniffer {
s := new(Sniffer)
for _, protocol := range sniferList {
var f func([]byte) (string, error)
switch protocol {
case proxyman.KnownProtocols_HTTP:
f = SniffHTTP
case proxyman.KnownProtocols_TLS:
f = SniffTLS
default:
panic("Unsupported protocol")
}
s.slist = append(s.slist, f)
}
s.err = make([]error, len(s.slist))
return s
}
func (s *Sniffer) Sniff(payload []byte) (string, error) {
sniffed := false
for idx, sniffer := range s.slist {
if s.err[idx] != nil {
continue
}
sniffed = true
domain, err := sniffer(payload)
if err == nil {
return domain, nil
}
if err != ErrMoreData {
s.err[idx] = err
}
}
if sniffed {
return "", ErrMoreData
}
return "", s.err[0]
}