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socks.go
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socks.go
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package socks
import (
"errors"
"io"
"net"
"strconv"
)
// SOCKS auth type
const (
AuthNone = 0
AuthPassword = 2
)
// SOCKS request commands as defined in RFC 1928 section 4
const (
CmdError byte = 0
CmdConnect byte = 1
CmdBind byte = 2
CmdUDPAssociate byte = 3
)
// SOCKS address types as defined in RFC 1928 section 5
const (
ATypIP4 = 1
ATypDomain = 3
ATypIP6 = 4
)
// MaxAddrLen is the maximum size of SOCKS address in bytes
const MaxAddrLen = 1 + 1 + 255 + 2
// Errors are socks5 errors
var Errors = []error{
errors.New(""),
errors.New("general failure"),
errors.New("connection forbidden"),
errors.New("network unreachable"),
errors.New("host unreachable"),
errors.New("connection refused"),
errors.New("TTL expired"),
errors.New("command not supported"),
errors.New("address type not supported"),
errors.New("socks5UDPAssociate"),
}
// Addr represents a SOCKS address as defined in RFC 1928 section 5.
type Addr []byte
// String serializes SOCKS address a to string form.
func (a Addr) String() string {
var host, port string
switch a[0] { // address type
case ATypDomain:
host = string(a[2 : 2+int(a[1])])
port = strconv.Itoa((int(a[2+int(a[1])]) << 8) | int(a[2+int(a[1])+1]))
case ATypIP4:
host = net.IP(a[1 : 1+net.IPv4len]).String()
port = strconv.Itoa((int(a[1+net.IPv4len]) << 8) | int(a[1+net.IPv4len+1]))
case ATypIP6:
host = net.IP(a[1 : 1+net.IPv6len]).String()
port = strconv.Itoa((int(a[1+net.IPv6len]) << 8) | int(a[1+net.IPv6len+1]))
}
return net.JoinHostPort(host, port)
}
// Network returns network name. Implements net.Addr interface.
func (a Addr) Network() string { return "socks" }
// ReadAddrBuf reads just enough bytes from r to get a valid Addr.
func ReadAddrBuf(r io.Reader, b []byte) (Addr, error) {
if len(b) < MaxAddrLen {
return nil, io.ErrShortBuffer
}
_, err := io.ReadFull(r, b[:1]) // read 1st byte for address type
if err != nil {
return nil, err
}
switch b[0] {
case ATypDomain:
_, err = io.ReadFull(r, b[1:2]) // read 2nd byte for domain length
if err != nil {
return nil, err
}
_, err = io.ReadFull(r, b[2:2+int(b[1])+2])
return b[:1+1+int(b[1])+2], err
case ATypIP4:
_, err = io.ReadFull(r, b[1:1+net.IPv4len+2])
return b[:1+net.IPv4len+2], err
case ATypIP6:
_, err = io.ReadFull(r, b[1:1+net.IPv6len+2])
return b[:1+net.IPv6len+2], err
}
return nil, Errors[8]
}
// ReadAddr reads just enough bytes from r to get a valid Addr.
func ReadAddr(r io.Reader) (Addr, error) {
return ReadAddrBuf(r, make([]byte, MaxAddrLen))
}
// SplitAddr slices a SOCKS address from beginning of b. Returns nil if failed.
func SplitAddr(b []byte) Addr {
addrLen := 1
if len(b) < addrLen {
return nil
}
switch b[0] {
case ATypDomain:
if len(b) < 2 {
return nil
}
addrLen = 1 + 1 + int(b[1]) + 2
case ATypIP4:
addrLen = 1 + net.IPv4len + 2
case ATypIP6:
addrLen = 1 + net.IPv6len + 2
default:
return nil
}
if len(b) < addrLen {
return nil
}
return b[:addrLen]
}
// ParseAddr parses the address in string s. Returns nil if failed.
func ParseAddr(s string) Addr {
var addr Addr
host, port, err := net.SplitHostPort(s)
if err != nil {
return nil
}
if ip := net.ParseIP(host); ip != nil {
if ip4 := ip.To4(); ip4 != nil {
addr = make([]byte, 1+net.IPv4len+2)
addr[0] = ATypIP4
copy(addr[1:], ip4)
} else {
addr = make([]byte, 1+net.IPv6len+2)
addr[0] = ATypIP6
copy(addr[1:], ip)
}
} else {
if len(host) > 255 {
return nil
}
addr = make([]byte, 1+1+len(host)+2)
addr[0] = ATypDomain
addr[1] = byte(len(host))
copy(addr[2:], host)
}
portnum, err := strconv.ParseUint(port, 10, 16)
if err != nil {
return nil
}
addr[len(addr)-2], addr[len(addr)-1] = byte(portnum>>8), byte(portnum)
return addr
}