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client.go
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client.go
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package socks4
import (
"context"
"errors"
"fmt"
"io"
"net"
"net/url"
"time"
)
// Dialer is a SOCKS4 dialer.
type Dialer struct {
// ProxyNetwork network between a proxy server and a client
ProxyNetwork string
// ProxyAddress proxy server address
ProxyAddress string
// ProxyDial specifies the optional dial function for
// establishing the transport connection.
ProxyDial func(ctx context.Context, network string, address string) (net.Conn, error)
// Username use username authentication if not empty
Username string
// IsResolve resolve domain name on locally
IsResolve bool
// Resolver optionally specifies an alternate resolver to use
Resolver *net.Resolver
// Timeout is the maximum amount of time a dial will wait for
// a connect to complete. The default is no timeout
Timeout time.Duration
}
// NewDialer returns a new Dialer that dials through the provided
// proxy server's network and address.
func NewDialer(addr string) (*Dialer, error) {
d := &Dialer{
ProxyNetwork: "tcp",
Timeout: time.Minute,
}
u, err := url.Parse(addr)
if err != nil {
return nil, err
}
switch u.Scheme {
case "socks4":
d.IsResolve = true
case "socks4a":
default:
return nil, fmt.Errorf("unsupported protocol '%s'", u.Scheme)
}
host := u.Host
port := u.Port()
if port == "" {
port = "1080"
hostname := u.Hostname()
host = net.JoinHostPort(hostname, port)
}
if u.User != nil {
d.Username = u.User.Username()
}
d.ProxyAddress = host
return d, nil
}
// DialContext connects to the provided address on the provided network.
func (d *Dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
switch network {
default:
return nil, fmt.Errorf("unsupported network %q", network)
case "tcp", "tcp4", "tcp6":
return d.do(ctx, ConnectCommand, address)
}
}
// Dial connects to the provided address on the provided network.
func (d *Dialer) Dial(network, address string) (net.Conn, error) {
return d.DialContext(context.Background(), network, address)
}
func (d *Dialer) Listen(ctx context.Context, network, address string) (net.Listener, error) {
switch network {
default:
return nil, fmt.Errorf("unsupported network %q", network)
case "tcp", "tcp4", "tcp6":
}
return &listener{ctx: ctx, d: d, address: address}, nil
}
// DialContext connects to the provided address on the provided network.
func (d *Dialer) do(ctx context.Context, cmd Command, address string) (net.Conn, error) {
if d.IsResolve {
host, port, err := net.SplitHostPort(address)
if err != nil {
return nil, err
}
if host != "" {
ip := net.ParseIP(host)
if ip == nil {
ipaddr, err := d.resolver().LookupIP(ctx, "ip4", host)
if err != nil {
return nil, err
}
host := ipaddr[0].String()
address = net.JoinHostPort(host, port)
}
}
}
conn, err := d.proxyDial(ctx, d.ProxyNetwork, d.ProxyAddress)
if err != nil {
return nil, err
}
_, err = d.connect(ctx, conn, cmd, address)
if err != nil {
conn.Close()
return nil, err
}
return conn, nil
}
func (d *Dialer) connect(ctx context.Context, conn net.Conn, cmd Command, address string) (net.Addr, error) {
if d.Timeout != 0 {
deadline := time.Now().Add(d.Timeout)
if d, ok := ctx.Deadline(); !ok || deadline.Before(d) {
subCtx, cancel := context.WithDeadline(ctx, deadline)
defer cancel()
ctx = subCtx
}
}
if deadline, ok := ctx.Deadline(); ok && !deadline.IsZero() {
conn.SetDeadline(deadline)
defer conn.SetDeadline(time.Time{})
}
_, err := conn.Write([]byte{socks4Version, byte(cmd)})
if err != nil {
return nil, err
}
err = writeAddrAndUserWithStr(conn, address, d.Username)
if err != nil {
return nil, err
}
return d.readReply(conn)
}
func (d *Dialer) readReply(conn net.Conn) (net.Addr, error) {
var header [2]byte
i, err := io.ReadFull(conn, header[:])
if err != nil {
return nil, err
}
if i != 2 {
return nil, errors.New("server does not respond properly")
}
addr, err := readAddr(conn)
if err != nil {
return nil, err
}
rep := reply(header[1])
if rep != grantedReply {
return nil, fmt.Errorf("socks connection request failed: %s", rep)
}
return addr, nil
}
func (d *Dialer) resolver() *net.Resolver {
if d.Resolver == nil {
return net.DefaultResolver
}
return d.Resolver
}
func (d *Dialer) proxyDial(ctx context.Context, network, address string) (net.Conn, error) {
proxyDial := d.ProxyDial
if proxyDial == nil {
var dialer net.Dialer
proxyDial = dialer.DialContext
}
return proxyDial(ctx, network, address)
}
type listener struct {
ctx context.Context
d *Dialer
address string
}
// Accept waits for and returns the next connection to the listener.
func (l *listener) Accept() (net.Conn, error) {
conn, err := l.d.do(l.ctx, BindCommand, l.address)
if err != nil {
return nil, err
}
addr, err := l.d.readReply(conn)
if err != nil {
return nil, err
}
return &connect{Conn: conn, remoteAddr: addr}, nil
}
// Close closes the listener.
func (l *listener) Close() error {
return nil
}
// address returns the listener's network address.
func (l *listener) Addr() net.Addr {
return nil
}
type connect struct {
net.Conn
remoteAddr net.Addr
}
func (c *connect) RemoteAddr() net.Addr {
return c.remoteAddr
}