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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package socks provides a SOCKS version 5 client implementation.
//
// SOCKS protocol version 5 is defined in RFC 1928.
// Username/Password authentication for SOCKS version 5 is defined in
// RFC 1929.
package socks
import (
"context"
"errors"
"io"
"net"
"strconv"
)
// A Command represents a SOCKS command.
type Command int
func (cmd Command) String() string {
switch cmd {
case CmdConnect:
return "socks connect"
case cmdBind:
return "socks bind"
default:
return "socks " + strconv.Itoa(int(cmd))
}
}
// An AuthMethod represents a SOCKS authentication method.
type AuthMethod int
// A Reply represents a SOCKS command reply code.
type Reply int
func (code Reply) String() string {
switch code {
case StatusSucceeded:
return "succeeded"
case 0x01:
return "general SOCKS server failure"
case 0x02:
return "connection not allowed by ruleset"
case 0x03:
return "network unreachable"
case 0x04:
return "host unreachable"
case 0x05:
return "connection refused"
case 0x06:
return "TTL expired"
case 0x07:
return "command not supported"
case 0x08:
return "address type not supported"
default:
return "unknown code: " + strconv.Itoa(int(code))
}
}
// Wire protocol constants.
const (
Version5 = 0x05
AddrTypeIPv4 = 0x01
AddrTypeFQDN = 0x03
AddrTypeIPv6 = 0x04
CmdConnect Command = 0x01 // establishes an active-open forward proxy connection
cmdBind Command = 0x02 // establishes a passive-open forward proxy connection
AuthMethodNotRequired AuthMethod = 0x00 // no authentication required
AuthMethodUsernamePassword AuthMethod = 0x02 // use username/password
AuthMethodNoAcceptableMethods AuthMethod = 0xff // no acceptable authentication methods
StatusSucceeded Reply = 0x00
)
// An Addr represents a SOCKS-specific address.
// Either Name or IP is used exclusively.
type Addr struct {
Name string // fully-qualified domain name
IP net.IP
Port int
}
func (a *Addr) Network() string { return "socks" }
func (a *Addr) String() string {
if a == nil {
return "<nil>"
}
port := strconv.Itoa(a.Port)
if a.IP == nil {
return net.JoinHostPort(a.Name, port)
}
return net.JoinHostPort(a.IP.String(), port)
}
// A Conn represents a forward proxy connection.
type Conn struct {
net.Conn
boundAddr net.Addr
}
// BoundAddr returns the address assigned by the proxy server for
// connecting to the command target address from the proxy server.
func (c *Conn) BoundAddr() net.Addr {
if c == nil {
return nil
}
return c.boundAddr
}
// A Dialer holds SOCKS-specific options.
type Dialer struct {
cmd Command // either CmdConnect or cmdBind
proxyNetwork string // network between a proxy server and a client
proxyAddress string // proxy server address
// ProxyDial specifies the optional dial function for
// establishing the transport connection.
ProxyDial func(context.Context, string, string) (net.Conn, error)
// AuthMethods specifies the list of request authentication
// methods.
// If empty, SOCKS client requests only AuthMethodNotRequired.
AuthMethods []AuthMethod
// Authenticate specifies the optional authentication
// function. It must be non-nil when AuthMethods is not empty.
// It must return an error when the authentication is failed.
Authenticate func(context.Context, io.ReadWriter, AuthMethod) error
}
// DialContext connects to the provided address on the provided
// network.
//
// The returned error value may be a net.OpError. When the Op field of
// net.OpError contains "socks", the Source field contains a proxy
// server address and the Addr field contains a command target
// address.
//
// See func Dial of the net package of standard library for a
// description of the network and address parameters.
func (d *Dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
if err := d.validateTarget(network, address); err != nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
if ctx == nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: errors.New("nil context")}
}
var err error
var c net.Conn
if d.ProxyDial != nil {
c, err = d.ProxyDial(ctx, d.proxyNetwork, d.proxyAddress)
} else {
var dd net.Dialer
c, err = dd.DialContext(ctx, d.proxyNetwork, d.proxyAddress)
}
if err != nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
a, err := d.connect(ctx, c, address)
if err != nil {
c.Close()
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
return &Conn{Conn: c, boundAddr: a}, nil
}
// DialWithConn initiates a connection from SOCKS server to the target
// network and address using the connection c that is already
// connected to the SOCKS server.
//
// It returns the connection's local address assigned by the SOCKS
// server.
func (d *Dialer) DialWithConn(ctx context.Context, c net.Conn, network, address string) (net.Addr, error) {
if err := d.validateTarget(network, address); err != nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
if ctx == nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: errors.New("nil context")}
}
a, err := d.connect(ctx, c, address)
if err != nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
return a, nil
}
// Dial connects to the provided address on the provided network.
//
// Unlike DialContext, it returns a raw transport connection instead
// of a forward proxy connection.
//
// Deprecated: Use DialContext or DialWithConn instead.
func (d *Dialer) Dial(network, address string) (net.Conn, error) {
if err := d.validateTarget(network, address); err != nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
var err error
var c net.Conn
if d.ProxyDial != nil {
c, err = d.ProxyDial(context.Background(), d.proxyNetwork, d.proxyAddress)
} else {
c, err = net.Dial(d.proxyNetwork, d.proxyAddress)
}
if err != nil {
proxy, dst, _ := d.pathAddrs(address)
return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
}
if _, err := d.DialWithConn(context.Background(), c, network, address); err != nil {
c.Close()
return nil, err
}
return c, nil
}
func (d *Dialer) validateTarget(network, address string) error {
switch network {
case "tcp", "tcp6", "tcp4":
default:
return errors.New("network not implemented")
}
switch d.cmd {
case CmdConnect, cmdBind:
default:
return errors.New("command not implemented")
}
return nil
}
func (d *Dialer) pathAddrs(address string) (proxy, dst net.Addr, err error) {
for i, s := range []string{d.proxyAddress, address} {
host, port, err := splitHostPort(s)
if err != nil {
return nil, nil, err
}
a := &Addr{Port: port}
a.IP = net.ParseIP(host)
if a.IP == nil {
a.Name = host
}
if i == 0 {
proxy = a
} else {
dst = a
}
}
return
}
// NewDialer returns a new Dialer that dials through the provided
// proxy server's network and address.
func NewDialer(network, address string) *Dialer {
return &Dialer{proxyNetwork: network, proxyAddress: address, cmd: CmdConnect}
}
const (
authUsernamePasswordVersion = 0x01
authStatusSucceeded = 0x00
)
// UsernamePassword are the credentials for the username/password
// authentication method.
type UsernamePassword struct {
Username string
Password string
}
// Authenticate authenticates a pair of username and password with the
// proxy server.
func (up *UsernamePassword) Authenticate(ctx context.Context, rw io.ReadWriter, auth AuthMethod) error {
switch auth {
case AuthMethodNotRequired:
return nil
case AuthMethodUsernamePassword:
if len(up.Username) == 0 || len(up.Username) > 255 || len(up.Password) == 0 || len(up.Password) > 255 {
return errors.New("invalid username/password")
}
b := []byte{authUsernamePasswordVersion}
b = append(b, byte(len(up.Username)))
b = append(b, up.Username...)
b = append(b, byte(len(up.Password)))
b = append(b, up.Password...)
// TODO(mikio): handle IO deadlines and cancelation if
// necessary
if _, err := rw.Write(b); err != nil {
return err
}
if _, err := io.ReadFull(rw, b[:2]); err != nil {
return err
}
if b[0] != authUsernamePasswordVersion {
return errors.New("invalid username/password version")
}
if b[1] != authStatusSucceeded {
return errors.New("username/password authentication failed")
}
return nil
}
return errors.New("unsupported authentication method " + strconv.Itoa(int(auth)))
}