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socks.go
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socks.go
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// Package socks implements essential parts of SOCKS protocol.
package socks
import (
"io"
"net"
"strconv"
)
// SOCKS address types as defined in RFC 1928 section 5.
const (
AtypIPv4 = 1
AtypDomainName = 3
AtypIPv6 = 4
ErrAddressNotSupported = Error(8)
)
// Error represents a SOCKS error
type Error byte
func (err Error) Error() string {
return "SOCKS error: " + strconv.Itoa(int(err))
}
// MaxAddrLen is the maximum size of SOCKS address in bytes.
const MaxAddrLen = 1 + 1 + 255 + 2
// 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 AtypDomainName:
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 AtypIPv4:
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 AtypIPv6:
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)
}
// String serializes SOCKS address a to string form.
func (a Addr) IPString() string {
switch a[0] { // address type
case AtypDomainName:
return string(a[2 : 2+int(a[1])])
case AtypIPv4:
return net.IP(a[1 : 1+net.IPv4len]).String()
case AtypIPv6:
return net.IP(a[1 : 1+net.IPv6len]).String()
}
return ""
}
func readAddr(r io.Reader, b []byte) (addr Addr, err 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 AtypDomainName:
_, err = io.ReadFull(r, b[1:2]) // read 2nd byte for domain length
if err != nil {
return nil, err
}
hostLen := uint16(b[1])
_, err = io.ReadFull(r, b[2:2+hostLen+2])
addr = b[:1+1+hostLen+2]
return
case AtypIPv4:
_, err = io.ReadFull(r, b[1:1+net.IPv4len+2])
addr = b[:1+net.IPv4len+2]
return
case AtypIPv6:
_, err = io.ReadFull(r, b[1:1+net.IPv6len+2])
addr = b[:1+net.IPv6len+2]
return
}
return nil, ErrAddressNotSupported
}
// ReadAddr reads just enough bytes from r to get a valid Addr.
func ReadAddr(r io.Reader) (Addr, error) {
return readAddr(r, make([]byte, MaxAddrLen))
}
// 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] = AtypIPv4
copy(addr[1:], ip4)
} else {
addr = make([]byte, 1+net.IPv6len+2)
addr[0] = AtypIPv6
copy(addr[1:], ip)
}
} else {
if len(host) > 255 {
return nil
}
addr = make([]byte, 1+1+len(host)+2)
addr[0] = AtypDomainName
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
}