exp/proxy: new package

exp/proxy provides client support for tunneling connections through
various proxies.

This is an initial, incomplete sketch of the code to lay down an
API.

R=golang-dev, r, r, bradfitz, rsc
CC=golang-dev
https://golang.org/cl/5490062

src/pkg/exp/proxy/Makefile

@@ -0,0 +1,14 @@
+# Copyright 2011 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.
+
+include ../../../Make.inc
+
+TARG=exp/proxy
+GOFILES=\
+	direct.go\
+	per_host.go\
+	proxy.go\
+	socks5.go\
+
+include ../../../Make.pkg

src/pkg/exp/proxy/direct.go

@@ -0,0 +1,18 @@
+// Copyright 2011 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 proxy
+
+import (
+	"net"
+)
+
+type direct struct{}
+
+// Direct is a direct proxy: one that makes network connections directly.
+var Direct = direct{}
+
+func (direct) Dial(network, addr string) (net.Conn, error) {
+	return net.Dial(network, addr)
+}

src/pkg/exp/proxy/per_host.go

@@ -0,0 +1,140 @@
+// Copyright 2011 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 proxy
+
+import (
+	"net"
+	"strings"
+)
+
+// A PerHost directs connections to a default Dailer unless the hostname
+// requested matches one of a number of exceptions.
+type PerHost struct {
+	def, bypass Dialer
+
+	bypassNetworks []*net.IPNet
+	bypassIPs      []net.IP
+	bypassZones    []string
+	bypassHosts    []string
+}
+
+// NewPerHost returns a PerHost Dialer that directs connections to either
+// defaultDialer or bypass, depending on whether the connection matches one of
+// the configured rules.
+func NewPerHost(defaultDialer, bypass Dialer) *PerHost {
+	return &PerHost{
+		def:    defaultDialer,
+		bypass: bypass,
+	}
+}
+
+// Dial connects to the address addr on the network net through either
+// defaultDialer or bypass.
+func (p *PerHost) Dial(network, addr string) (c net.Conn, err error) {
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	return p.dialerForRequest(host).Dial(network, addr)
+}
+
+func (p *PerHost) dialerForRequest(host string) Dialer {
+	if ip := net.ParseIP(host); ip != nil {
+		for _, net := range p.bypassNetworks {
+			if net.Contains(ip) {
+				return p.bypass
+			}
+		}
+		for _, bypassIP := range p.bypassIPs {
+			if bypassIP.Equal(ip) {
+				return p.bypass
+			}
+		}
+		return p.def
+	}
+
+	for _, zone := range p.bypassZones {
+		if strings.HasSuffix(host, zone) {
+			return p.bypass
+		}
+		if host == zone[1:] {
+			// For a zone "example.com", we match "example.com"
+			// too.
+			return p.bypass
+		}
+	}
+	for _, bypassHost := range p.bypassHosts {
+		if bypassHost == host {
+			return p.bypass
+		}
+	}
+	return p.def
+}
+
+// AddFromString parses a string that contains comma-separated values
+// specifing hosts that should use the bypass proxy. Each value is either an
+// IP address, a CIDR range, a zone (*.example.com) or a hostname
+// (localhost). A best effort is made to parse the string and errors are
+// ignored.
+func (p *PerHost) AddFromString(s string) {
+	hosts := strings.Split(s, ",")
+	for _, host := range hosts {
+		host = strings.TrimSpace(host)
+		if len(host) == 0 {
+			continue
+		}
+		if strings.Contains(host, "/") {
+			// We assume that it's a CIDR address like 127.0.0.0/8
+			if _, net, err := net.ParseCIDR(host); err == nil {
+				p.AddNetwork(net)
+			}
+			continue
+		}
+		if ip := net.ParseIP(host); ip != nil {
+			p.AddIP(ip)
+			continue
+		}
+		if strings.HasPrefix(host, "*.") {
+			p.AddZone(host[1:])
+			continue
+		}
+		p.AddHost(host)
+	}
+}
+
+// AddIP specifies an IP address that will use the bypass proxy. Note that
+// this will only take effect if a literal IP address is dialed. A connection
+// to a named host will never match an IP.
+func (p *PerHost) AddIP(ip net.IP) {
+	p.bypassIPs = append(p.bypassIPs, ip)
+}
+
+// AddIP specifies an IP range that will use the bypass proxy. Note that this
+// will only take effect if a literal IP address is dialed. A connection to a
+// named host will never match.
+func (p *PerHost) AddNetwork(net *net.IPNet) {
+	p.bypassNetworks = append(p.bypassNetworks, net)
+}
+
+// AddZone specifies a DNS suffix that will use the bypass proxy. A zone of
+// "example.com" matches "example.com" and all of its subdomains.
+func (p *PerHost) AddZone(zone string) {
+	if strings.HasSuffix(zone, ".") {
+		zone = zone[:len(zone)-1]
+	}
+	if !strings.HasPrefix(zone, ".") {
+		zone = "." + zone
+	}
+	p.bypassZones = append(p.bypassZones, zone)
+}
+
+// AddHost specifies a hostname that will use the bypass proxy.
+func (p *PerHost) AddHost(host string) {
+	if strings.HasSuffix(host, ".") {
+		host = host[:len(host)-1]
+	}
+	p.bypassHosts = append(p.bypassHosts, host)
+}

src/pkg/exp/proxy/per_host_test.go

@@ -0,0 +1,55 @@
+// Copyright 2011 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 proxy
+
+import (
+	"errors"
+	"net"
+	"reflect"
+	"testing"
+)
+
+type recordingProxy struct {
+	addrs []string
+}
+
+func (r *recordingProxy) Dial(network, addr string) (net.Conn, error) {
+	r.addrs = append(r.addrs, addr)
+	return nil, errors.New("recordingProxy")
+}
+
+func TestPerHost(t *testing.T) {
+	var def, bypass recordingProxy
+	perHost := NewPerHost(&def, &bypass)
+	perHost.AddFromString("localhost,*.zone,127.0.0.1,10.0.0.1/8,1000::/16")
+
+	expectedDef := []string{
+		"example.com:123",
+		"1.2.3.4:123",
+		"[1001::]:123",
+	}
+	expectedBypass := []string{
+		"localhost:123",
+		"zone:123",
+		"foo.zone:123",
+		"127.0.0.1:123",
+		"10.1.2.3:123",
+		"[1000::]:123",
+	}
+
+	for _, addr := range expectedDef {
+		perHost.Dial("tcp", addr)
+	}
+	for _, addr := range expectedBypass {
+		perHost.Dial("tcp", addr)
+	}
+
+	if !reflect.DeepEqual(expectedDef, def.addrs) {
+		t.Errorf("Hosts which went to the default proxy didn't match. Got %v, want %v", def.addrs, expectedDef)
+	}
+	if !reflect.DeepEqual(expectedBypass, bypass.addrs) {
+		t.Errorf("Hosts which went to the bypass proxy didn't match. Got %v, want %v", bypass.addrs, expectedBypass)
+	}
+}

src/pkg/exp/proxy/proxy.go

@@ -0,0 +1,98 @@
+// Copyright 2011 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 proxy provides support for a variety of protocols to proxy network
+// data.
+package proxy
+
+import (
+	"errors"
+	"net"
+	"net/url"
+	"os"
+	"strings"
+)
+
+// A Dialer is a means to establish a connection.
+type Dialer interface {
+	// Dial connects to the given address via the proxy.
+	Dial(network, addr string) (c net.Conn, err error)
+}
+
+// Auth contains authentication parameters that specific Dialers may require.
+type Auth struct {
+	User, Password string
+}
+
+// DefaultDialer returns the dialer specified by the proxy related variables in
+// the environment.
+func FromEnvironment() Dialer {
+	allProxy := os.Getenv("all_proxy")
+	if len(allProxy) == 0 {
+		return Direct
+	}
+
+	proxyURL, err := url.Parse(allProxy)
+	if err != nil {
+		return Direct
+	}
+	proxy, err := FromURL(proxyURL, Direct)
+	if err != nil {
+		return Direct
+	}
+
+	noProxy := os.Getenv("no_proxy")
+	if len(noProxy) == 0 {
+		return proxy
+	}
+
+	perHost := NewPerHost(proxy, Direct)
+	perHost.AddFromString(noProxy)
+	return perHost
+}
+
+// proxySchemes is a map from URL schemes to a function that creates a Dialer
+// from a URL with such a scheme.
+var proxySchemes map[string]func(*url.URL, Dialer) (Dialer, error)
+
+// RegisterDialerType takes a URL scheme and a function to generate Dialers from
+// a URL with that scheme and a forwarding Dialer. Registered schemes are used
+// by FromURL.
+func RegisterDialerType(scheme string, f func(*url.URL, Dialer) (Dialer, error)) {
+	if proxySchemes == nil {
+		proxySchemes = make(map[string]func(*url.URL, Dialer) (Dialer, error))
+	}
+	proxySchemes[scheme] = f
+}
+
+// FromURL returns a Dialer given a URL specification and an underlying
+// Dialer for it to make network requests.
+func FromURL(u *url.URL, forward Dialer) (Dialer, error) {
+	var auth *Auth
+	if len(u.RawUserinfo) > 0 {
+		auth = new(Auth)
+		parts := strings.SplitN(u.RawUserinfo, ":", 1)
+		if len(parts) == 1 {
+			auth.User = parts[0]
+		} else if len(parts) >= 2 {
+			auth.User = parts[0]
+			auth.Password = parts[1]
+		}
+	}
+
+	switch u.Scheme {
+	case "socks5":
+		return SOCKS5("tcp", u.Host, auth, forward)
+	}
+
+	// If the scheme doesn't match any of the built-in schemes, see if it
+	// was registered by another package.
+	if proxySchemes != nil {
+		if f, ok := proxySchemes[u.Scheme]; ok {
+			return f(u, forward)
+		}
+	}
+
+	return nil, errors.New("proxy: unknown scheme: " + u.Scheme)
+}

src/pkg/exp/proxy/proxy_test.go

@@ -0,0 +1,50 @@
+// Copyright 2011 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 proxy
+
+import (
+	"net"
+	"net/url"
+	"testing"
+)
+
+type testDialer struct {
+	network, addr string
+}
+
+func (t *testDialer) Dial(network, addr string) (net.Conn, error) {
+	t.network = network
+	t.addr = addr
+	return nil, t
+}
+
+func (t *testDialer) Error() string {
+	return "testDialer " + t.network + " " + t.addr
+}
+
+func TestFromURL(t *testing.T) {
+	u, err := url.Parse("socks5://user:password@1.2.3.4:5678")
+	if err != nil {
+		t.Fatalf("failed to parse URL: %s", err)
+	}
+
+	tp := &testDialer{}
+	proxy, err := FromURL(u, tp)
+	if err != nil {
+		t.Fatalf("FromURL failed: %s", err)
+	}
+
+	conn, err := proxy.Dial("tcp", "example.com:80")
+	if conn != nil {
+		t.Error("Dial unexpected didn't return an error")
+	}
+	if tp, ok := err.(*testDialer); ok {
+		if tp.network != "tcp" || tp.addr != "1.2.3.4:5678" {
+			t.Errorf("Dialer connected to wrong host. Wanted 1.2.3.4:5678, got: %v", tp)
+		}
+	} else {
+		t.Errorf("Unexpected error from Dial: %s", err)
+	}
+}

src/pkg/exp/proxy/socks5.go

@@ -0,0 +1,207 @@
+// Copyright 2011 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 proxy
+
+import (
+	"errors"
+	"io"
+	"net"
+	"strconv"
+)
+
+// SOCKS5 returns a Dialer that makes SOCKSv5 connections to the given address
+// with an optional username and password. See RFC 1928.
+func SOCKS5(network, addr string, auth *Auth, forward Dialer) (Dialer, error) {
+	s := &socks5{
+		network: network,
+		addr:    addr,
+		forward: forward,
+	}
+	if auth != nil {
+		s.user = auth.User
+		s.password = auth.Password
+	}
+
+	return s, nil
+}
+
+type socks5 struct {
+	user, password string
+	network, addr  string
+	forward        Dialer
+}
+
+const socks5Version = 5
+
+const (
+	socks5AuthNone     = 0
+	socks5AuthPassword = 2
+)
+
+const socks5Connect = 1
+
+const (
+	socks5IP4    = 1
+	socks5Domain = 3
+	socks5IP6    = 4
+)
+
+var socks5Errors = []string{
+	"",
+	"general failure",
+	"connection forbidden",
+	"network unreachable",
+	"host unreachable",
+	"connection refused",
+	"TTL expired",
+	"command not supported",
+	"address type not supported",
+}
+
+// Dial connects to the address addr on the network net via the SOCKS5 proxy.
+func (s *socks5) Dial(network, addr string) (net.Conn, error) {
+	switch network {
+	case "tcp", "tcp6", "tcp4":
+		break
+	default:
+		return nil, errors.New("proxy: no support for SOCKS5 proxy connections of type " + network)
+	}
+
+	conn, err := s.forward.Dial(s.network, s.addr)
+	if err != nil {
+		return nil, err
+	}
+	closeConn := &conn
+	defer func() {
+		if closeConn != nil {
+			(*closeConn).Close()
+		}
+	}()
+
+	host, portStr, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	port, err := strconv.Atoi(portStr)
+	if err != nil {
+		return nil, errors.New("proxy: failed to parse port number: " + portStr)
+	}
+	if port < 1 || port > 0xffff {
+		return nil, errors.New("proxy: port number out of range: " + portStr)
+	}
+
+	// the size here is just an estimate
+	buf := make([]byte, 0, 6+len(host))
+
+	buf = append(buf, socks5Version)
+	if len(s.user) > 0 && len(s.user) < 256 && len(s.password) < 256 {
+		buf = append(buf, 2, /* num auth methods */ socks5AuthNone, socks5AuthPassword)
+	} else {
+		buf = append(buf, 1, /* num auth methods */ socks5AuthNone)
+	}
+
+	if _, err = conn.Write(buf); err != nil {
+		return nil, errors.New("proxy: failed to write greeting to SOCKS5 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	if _, err = io.ReadFull(conn, buf[:2]); err != nil {
+		return nil, errors.New("proxy: failed to read greeting from SOCKS5 proxy at " + s.addr + ": " + err.Error())
+	}
+	if buf[0] != 5 {
+		return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " has unexpected version " + strconv.Itoa(int(buf[0])))
+	}
+	if buf[1] == 0xff {
+		return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " requires authentication")
+	}
+
+	if buf[1] == socks5AuthPassword {
+		buf = buf[:0]
+		buf = append(buf, socks5Version)
+		buf = append(buf, uint8(len(s.user)))
+		buf = append(buf, s.user...)
+		buf = append(buf, uint8(len(s.password)))
+		buf = append(buf, s.password...)
+
+		if _, err = conn.Write(buf); err != nil {
+			return nil, errors.New("proxy: failed to write authentication request to SOCKS5 proxy at " + s.addr + ": " + err.Error())
+		}
+
+		if _, err = io.ReadFull(conn, buf[:2]); err != nil {
+			return nil, errors.New("proxy: failed to read authentication reply from SOCKS5 proxy at " + s.addr + ": " + err.Error())
+		}
+
+		if buf[1] != 0 {
+			return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " rejected username/password")
+		}
+	}
+
+	buf = buf[:0]
+	buf = append(buf, socks5Version, socks5Connect, 0 /* reserved */ )
+
+	if ip := net.ParseIP(host); ip != nil {
+		if len(ip) == 4 {
+			buf = append(buf, socks5IP4)
+		} else {
+			buf = append(buf, socks5IP6)
+		}
+		buf = append(buf, []byte(ip)...)
+	} else {
+		buf = append(buf, socks5Domain)
+		buf = append(buf, byte(len(host)))
+		buf = append(buf, host...)
+	}
+	buf = append(buf, byte(port>>8), byte(port))
+
+	if _, err = conn.Write(buf); err != nil {
+		return nil, errors.New("proxy: failed to write connect request to SOCKS5 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	if _, err = io.ReadFull(conn, buf[:4]); err != nil {
+		return nil, errors.New("proxy: failed to read connect reply from SOCKS5 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	failure := "unknown error"
+	if int(buf[1]) < len(socks5Errors) {
+		failure = socks5Errors[buf[1]]
+	}
+
+	if len(failure) > 0 {
+		return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " failed to connect: " + failure)
+	}
+
+	bytesToDiscard := 0
+	switch buf[3] {
+	case socks5IP4:
+		bytesToDiscard = 4
+	case socks5IP6:
+		bytesToDiscard = 16
+	case socks5Domain:
+		_, err := io.ReadFull(conn, buf[:1])
+		if err != nil {
+			return nil, errors.New("proxy: failed to read domain length from SOCKS5 proxy at " + s.addr + ": " + err.Error())
+		}
+		bytesToDiscard = int(buf[0])
+	default:
+		return nil, errors.New("proxy: got unknown address type " + strconv.Itoa(int(buf[3])) + " from SOCKS5 proxy at " + s.addr)
+	}
+
+	if cap(buf) < bytesToDiscard {
+		buf = make([]byte, bytesToDiscard)
+	} else {
+		buf = buf[:bytesToDiscard]
+	}
+	if _, err = io.ReadFull(conn, buf); err != nil {
+		return nil, errors.New("proxy: failed to read address from SOCKS5 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	// Also need to discard the port number
+	if _, err = io.ReadFull(conn, buf[:2]); err != nil {
+		return nil, errors.New("proxy: failed to read port from SOCKS5 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	closeConn = nil
+	return conn, nil
+}