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// Copyright (C) 2022 Andrew Ayer
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//
// Except as contained in this notice, the name(s) of the above copyright
// holders shall not be used in advertising or otherwise to promote the
// sale, use or other dealings in this Software without prior written
// authorization.
package proxy
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"net"
)
var protocolSignature = [12]byte{0x0D, 0x0A, 0x0D, 0x0A, 0x00, 0x0D, 0x0A, 0x51, 0x55, 0x49, 0x54, 0x0A}
const protocolVersion = 2
const (
commandLocal = 0x00
commandProxy = 0x01
)
const (
familyUnspecified = 0x00
familyTCP4 = 0x11
familyUDP4 = 0x12
familyTCP6 = 0x21
familyUDP6 = 0x22
)
// Header represents a PROXY protocol header
type Header struct {
RemoteAddr net.Addr
LocalAddr net.Addr
}
// Read the PROXY protocol header from conn
func ReadHeader(conn net.Conn) (*Header, error) {
var preamble [16]byte
if _, err := io.ReadFull(conn, preamble[:]); err != nil {
return nil, err
}
var (
signature = preamble[0:12]
version = preamble[12] >> 4
command = preamble[12] & 0xF
family = preamble[13]
length = binary.BigEndian.Uint16(preamble[14:16])
)
if !bytes.Equal(signature[:], protocolSignature[:]) {
return nil, errors.New("not a proxied connection")
}
if version != protocolVersion {
return nil, errors.New("unsupported proxy protocol version")
}
payload := make([]byte, length)
if _, err := io.ReadFull(conn, payload); err != nil {
return nil, err
}
switch command {
case commandLocal:
return &Header{LocalAddr: conn.LocalAddr(), RemoteAddr: conn.RemoteAddr()}, nil
case commandProxy:
return parseProxyHeader(family, payload)
default:
return nil, fmt.Errorf("unsupported proxy command %x", command)
}
}
func parseProxyHeader(family uint8, payload []byte) (*Header, error) {
switch family {
case familyTCP4:
if len(payload) < 12 {
return nil, errors.New("header too short for TCP over IPv4")
}
return &Header{
RemoteAddr: &net.TCPAddr{
IP: payload[0:4],
Port: int(binary.BigEndian.Uint16(payload[8:10])),
},
LocalAddr: &net.TCPAddr{
IP: payload[4:8],
Port: int(binary.BigEndian.Uint16(payload[10:12])),
},
}, nil
case familyUDP4:
if len(payload) < 12 {
return nil, errors.New("header too short for UDP over IPv4")
}
return &Header{
RemoteAddr: &net.UDPAddr{
IP: payload[0:4],
Port: int(binary.BigEndian.Uint16(payload[8:10])),
},
LocalAddr: &net.UDPAddr{
IP: payload[4:8],
Port: int(binary.BigEndian.Uint16(payload[10:12])),
},
}, nil
case familyTCP6:
if len(payload) < 36 {
return nil, errors.New("header too short for TCP over IPv6")
}
return &Header{
RemoteAddr: &net.TCPAddr{
IP: payload[0:16],
Port: int(binary.BigEndian.Uint16(payload[32:34])),
},
LocalAddr: &net.TCPAddr{
IP: payload[16:32],
Port: int(binary.BigEndian.Uint16(payload[34:36])),
},
}, nil
case familyUDP6:
if len(payload) < 36 {
return nil, errors.New("header too short for UDP over IPv6")
}
return &Header{
RemoteAddr: &net.UDPAddr{
IP: payload[0:16],
Port: int(binary.BigEndian.Uint16(payload[32:34])),
},
LocalAddr: &net.UDPAddr{
IP: payload[16:32],
Port: int(binary.BigEndian.Uint16(payload[34:36])),
},
}, nil
default:
return nil, fmt.Errorf("unsupported address family %x", family)
}
}
// Return the wire representation of header
func (header Header) Format() []byte {
switch remoteAddr := header.RemoteAddr.(type) {
case *net.TCPAddr:
localAddr := header.LocalAddr.(*net.TCPAddr)
if remoteAddr.IP.To4() != nil {
return formatIPv4Header(familyTCP4, remoteAddr.IP, localAddr.IP, remoteAddr.Port, localAddr.Port)
} else {
return formatIPv6Header(familyTCP6, remoteAddr.IP, localAddr.IP, remoteAddr.Port, localAddr.Port)
}
case *net.UDPAddr:
localAddr := header.LocalAddr.(*net.UDPAddr)
if remoteAddr.IP.To4() != nil {
return formatIPv4Header(familyUDP4, remoteAddr.IP, localAddr.IP, remoteAddr.Port, localAddr.Port)
} else {
return formatIPv6Header(familyUDP6, remoteAddr.IP, localAddr.IP, remoteAddr.Port, localAddr.Port)
}
default:
return formatUnspecifiedHeader()
}
}
func formatIPv4Header(family uint8, remoteIP, localIP net.IP, remotePort, localPort int) []byte {
header := make([]byte, 28)
copy(header[0:12], protocolSignature[:])
header[12] = (protocolVersion << 4) | commandProxy
header[13] = family
binary.BigEndian.PutUint16(header[14:16], 12)
copy(header[16:20], remoteIP.To4())
copy(header[20:24], localIP.To4())
binary.BigEndian.PutUint16(header[24:26], uint16(remotePort))
binary.BigEndian.PutUint16(header[26:28], uint16(localPort))
return header[:]
}
func formatIPv6Header(family uint8, remoteIP, localIP net.IP, remotePort, localPort int) []byte {
header := make([]byte, 52)
copy(header[0:12], protocolSignature[:])
header[12] = (protocolVersion << 4) | commandProxy
header[13] = family
binary.BigEndian.PutUint16(header[14:16], 36)
copy(header[16:32], remoteIP)
copy(header[32:48], localIP)
binary.BigEndian.PutUint16(header[48:50], uint16(remotePort))
binary.BigEndian.PutUint16(header[50:52], uint16(localPort))
return header[:]
}
func formatUnspecifiedHeader() []byte {
var header [16]byte
copy(header[0:12], protocolSignature[:])
header[12] = (protocolVersion << 4) | commandProxy
header[13] = familyUnspecified
return header[:]
}
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