func handShake(conn net.Conn) (err error) {
const (
idVer = 0
idNmethod = 1
)
// version identification and method selection message in theory can have
// at most 256 methods, plus version and nmethod field in total 258 bytes
// the current rfc defines only 3 authentication methods (plus 2 reserved),
// so it won't be such long in practice
buf := make([]byte, 258)
var n int
ss.SetReadTimeout(conn)
// make sure we get the nmethod field
if n, err = io.ReadAtLeast(conn, buf, idNmethod+1); err != nil {
return
}
if buf[idVer] != socksVer5 {
return errVer
}
nmethod := int(buf[idNmethod])
msgLen := nmethod + 2
if n == msgLen { // handshake done, common case
// do nothing, jump directly to send confirmation
} else if n < msgLen { // has more methods to read, rare case
if _, err = io.ReadFull(conn, buf[n:msgLen]); err != nil {
return
}
} else { // error, should not get extra data
return errAuthExtraData
}
// send confirmation: version 5, no authentication required
_, err = conn.Write([]byte{socksVer5, 0})
return
}
func getRequest(conn net.Conn) (rawaddr []byte, host string, err error) {
const (
idVer = 0
idCmd = 1
idType = 3 // address type index
idIP0 = 4 // ip addres start index
idDmLen = 4 // domain address length index
idDm0 = 5 // domain address start index
typeIPv4 = 1 // type is ipv4 address
typeDm = 3 // type is domain address
typeIPv6 = 4 // type is ipv6 address
lenIPv4 = 3 + 1 + net.IPv4len + 2 // 3(ver+cmd+rsv) + 1addrType + ipv4 + 2port
lenIPv6 = 3 + 1 + net.IPv6len + 2 // 3(ver+cmd+rsv) + 1addrType + ipv6 + 2port
lenDmBase = 3 + 1 + 1 + 2 // 3 + 1addrType + 1addrLen + 2port, plus addrLen
)
// refer to getRequest in server.go for why set buffer size to 263
buf := make([]byte, 263)
var n int
ss.SetReadTimeout(conn)
// read till we get possible domain length field
if n, err = io.ReadAtLeast(conn, buf, idDmLen+1); err != nil {
return
}
// check version and cmd
if buf[idVer] != socksVer5 {
err = errVer
return
}
if buf[idCmd] != socksCmdConnect {
err = errCmd
return
}
reqLen := -1
switch buf[idType] {
case typeIPv4:
reqLen = lenIPv4
case typeIPv6:
reqLen = lenIPv6
case typeDm:
reqLen = int(buf[idDmLen]) + lenDmBase
default:
err = errAddrType
return
}
if n == reqLen {
// common case, do nothing
} else if n < reqLen { // rare case
if _, err = io.ReadFull(conn, buf[n:reqLen]); err != nil {
return
}
} else {
err = errReqExtraData
return
}
rawaddr = buf[idType:reqLen]
if debug {
switch buf[idType] {
case typeIPv4:
host = net.IP(buf[idIP0 : idIP0+net.IPv4len]).String()
case typeIPv6:
host = net.IP(buf[idIP0 : idIP0+net.IPv6len]).String()
case typeDm:
host = string(buf[idDm0 : idDm0+buf[idDmLen]])
}
port := binary.BigEndian.Uint16(buf[reqLen-2 : reqLen])
host = net.JoinHostPort(host, strconv.Itoa(int(port)))
}
return
}